Mole River Dam Feasibility Study WaterNSW
Feasibility Study Report
IS207200-0000-ZM-RPT-0001 | E 15 August 2017 WaterNSW Ref. 05039E31
Feasi bility S tudy R epo rt WaterNS W Feasibility Study Report
Mole River Dam Feasibility Study
© Copyright 2017 Jacobs Australia Pty Limited. The concepts and information contained in this document are the property of Jacobs. Use or copying of this document in whole or in part without the written permission of Jacobs constitutes an infringement of copyright.
Limitation: This document has been prepared on behalf of, and for the exclusive use of Jacobs’ client, and is subject to, and issued in accordance with, the provisions of the contract between Jacobs and the client. Jacobs accepts no liability or responsibility whatsoever for, or in respect of, any use of, or reliance upon, this document by any third party.
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Contents Executive Summary ...... 6 Introduction ...... 8 PART I: The need ...... 15 1. Needs assessment ...... 16 1.1 Past service need considerations ...... 17 1.2 Revised service need ...... 19 1.3 Objectives ...... 22 1.4 Intended benefits ...... 23 1.5 Discussion ...... 24 PART II: Meeting the need ...... 25 2. Options identification ...... 26 2.1 Non asset options ...... 26 2.2 Review of long list of dam site options ...... 26 2.3 Short list of options...... 27 3. Water resources hydrology ...... 28 3.1 Background ...... 28 3.2 Results...... 28 4. Engineering assessment ...... 32 4.1 Flood hydrology ...... 32 4.2 Geology ...... 32 4.3 Dam break consequence assessment ...... 33 4.4 Engineering...... 33 4.5 Cost Estimate...... 36 4.6 Construction schedule ...... 38 5. Environmental assessment ...... 39 5.1 Biodiversity ...... 39 5.2 Contaminated Land ...... 39 5.3 Water Quality ...... 39 5.4 Heritage ...... 39 PART III: Economic viability ...... 41 6. Economic viability...... 42 6.1 Economic Assessment - Cost Benefit Analysis (CBA) ...... 42 7. Discussion and next steps ...... 60 8. Conclusion ...... 63 9. Bibliography ...... 64
Appendix A. Full cost benefit analysis results ...... A-1 Appendix B. Evidence supporting project need ...... B-1 Appendix C. Review of previous studies ...... C-1 Appendix D. Flood hydrology ...... D-1 Appendix E. Geology review ...... E-1
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Appendix F. Consequence Assessment ...... F-1 Appendix G. Flood capacity and spillway design ...... G-1 Appendix H. Environmental desktop assessment ...... H-1 Appendix I. Cost Estimate Schedules ...... I-1 Appendix J. Map showing reservoir extents for Option 3 ...... J-1 Appendix K. Concept design drawing – BRC, 1990 ...... K-1 Appendix L. Concept design – Jacobs, 2017...... L-1
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List of Figures Figure 1 : Border Rivers System Schematic Map (WaterNSW, 2016) ...... 9 Figure 2 : Distribution of irrigation land use in Border Rivers (data provided by Border Rivers Commission) ..... 10 Figure 3 : Distribution of irrigation land use in NSW and Qld Border Rivers (data provided by Border Rivers Commission) ...... 11 Figure 1.1 : Summary of case for change ...... 16 Figure 2.1 : Overview of dam site options (green = feasible/satisfactory, amber= moderately challenging red = unsatisfactory/ challenging) ...... 27 Figure 3.1 : 1st October allocation for general security B licences – all water to NSW case ...... 29 Figure 3.2 : Annual exceedance curve of total demand supplied ...... 30 Figure 4.1 : Stage-storage relationship for the Upper Mole River dam site ...... 34 Figure 4.2 : Stage-area relationship for the Upper Mole River dam site...... 34 Figure 4.3 : Typical dam section for 200GL option (outlet not shown) ...... 36 Figure 4.4 : Cost breakdown for 100 GL rockfill dam ...... 37 Figure 6.1 : Modelled demand for base case and three options ...... 47 Figure 6.2 : Trend in crop types from 1997 to 2017 in Victorian Murray-Mallee (Mallee CMA, 2015) ...... 50 Figure B.1 : Long term annual water reliability for general Security B (provided by Water NSW, 2017) ...... B-2 Figure B.2 : Variable allocations announced for General Security B licences in NSW Border Rivers (source: NSW, DPI) ...... B-3 Figure B.3 : Border Rivers water use history 2006-07 to 2015-16 (BRC Annual Report 2015-16) ...... B-3 Figure B.4 : Supplementary water (NSW) allocations as % of licence share (120 GL) ...... B-4 Figure B.5 : Example of productive regions for almond industry expansion (NSW DPI, 2016) ...... B-5 Figure B.6 : Identified almond industry expansion potential (NSW DPI, 2016) ...... B-5 Figure B.7 : MIA crop types as % of total hectares planted (MIA annual report, 2015-2016) ...... B-9 Figure D.1 : Localities of interest ...... D-2 Figure D.2 : Annual maxima flow series for the Mole River at Donaldson ...... D-5 Figure D.3 : RFFE for Mole River at Donaldson ...... D-6 Figure D.4 : At-site flood frequency plot ...... D-7 Figure D.5 : RORB model features ...... D-9 Figure D.6 : 1976 ...... D-11 Figure D.7 : 1996 ...... D-12 Figure D.8 : 2011 ...... D-13 Figure D.9 : 1976 Calibration Results ...... D-14 Figure D.10 : 1996 Calibration Results ...... D-14 Figure D.11 : 2011 Calibration Results ...... D-15 Figure D.12 : PMP depth versus duration ...... D-16 Figure D.13 : Design rainfall depth-duration-AEP curves ...... D-17 Figure D.14 : Temporal Patterns for design runs used in RORB ...... D-18 Figure D.15 : PMP Hydrographs ...... D-20 Figure D.16 : Hydrographs at proposed Upper Mole River Dam location...... D-23 Figure G.1 : Flood Frequency Curve-FSL 490.5 mAHD ...... G-1
List of Tables Table 1 : Summary of key institutional arrangement feature and the impact on the proposal ...... 12 Table 1.1 : Causes and effects of the two service needs ...... 17 Table 1.2 : Service Need 1: Summary of cause, effect and relevant evidence...... 21 Table 1.3 : Service Need 2: Summary of cause, effect and relevant evidence...... 22 Table 1.4 : Benefit summary ...... 23 Table 3.1 : Change in demand supplied ...... 29 Table 4.1 : Design peak flows for the Upper Mole River Dam site ...... 32 Table 4.2 : Dam options and key dimensions ...... 34 Table 4.3 : Cost estimates totals for rockfill dam options...... 37 Table 4.4 : Construction timeframes ...... 38 Table 6.1 : Steps to be completed in a CBA ...... 42 Table 6.2 : General CBA assumptions...... 44 Table 6.3 : Dam cost assumptions ...... 45
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Table 6.4 : Dam filling assumptions ...... 46 Table 6.5 : Assumptions for average annual water usage for each option ...... 47 Table 6.6 : Assumptions for on farm costs and benefits related to improved reliability of supply ...... 48 Table 6.7 : Land use change assumptions (cotton to higher value cropping)...... 51 Table 6.8 : Assumptions for recreation and amenity benefits ...... 53 Table 6.9 : Residual value of the dam (7% real discount rate) ...... 55 Table 6.10 : CBA results, present value ($Million, 7% real discount rate) ...... 56 Table 6.11 : NPV and BCR sensitivity test results (shaded blue implies NPV>0)...... 57 Table 7.1 : Summary of uncertainties and limitations ...... 60 Table 9.1 : Service need summary of cause, effect and relevant evidence...... B-1 Table B.2 : Water Entitlements at the commencement of the 2009 WSP for NSW Border Rivers ...... B-2 Table B.3 : Gross margin comparison of cotton and almond growing ...... B-6 Table B.4 : Up-front investment costs to shift from cotton to almond irrigation ...... B-6 Table B.5 : Socio-economic profile summary for Border Rivers (ABS 2011 census data) ...... B-7 Table B.6 : MIA land use summary (MIA annual report, 2015-2016) ...... B-8 Table D.1 : Previous FFA Results Mole River at Donaldson ...... D-3 Table D.2 : Details of the previous reports calibration events ...... D-3 Table D.3 : Adopted Peak Flows from previous report ...... D-3 Table D.4 : RFFE variables ...... D-5 Table D.5 : RFFE parameters ...... D-5 Table D.6 : At-site flood quantiles ...... D-7 Table D.7 : Key catchment areas ...... D-8 Table D.8 : Design rainfall depth-duration-AEP table ...... D-16 Table D.9 : Monte-Carlo Initial Loss Distribution ...... D-18 Table D.10 : Monte Carlo model results ...... D-19 Table D.11 : PMP RORB results ...... D-20 Table D.12 : Adopted peaks flows from the various methods ...... D-21 Table D.13 : Parameters for deterministic hydrograph ...... D-22 Table D.14 : Proposed dam configurations ...... D-23 Table D.15 : Resulting peak Inflow and Outflow for all dam configurations ...... D-24 Table D.16 : RORB Subcatchment data ...... D-24 Table D.17 : Glenlyon Dam data ...... D-25 Table D.18 : Temporal Patterns for design events used in RORB ...... D-28 Table D.19 : Design Spatial Patterns ...... D-29 Table F.1 : Estimate of Severity of Damage and Loss ...... F-2 Table G.1 : Spillway Length Calculations...... G-2 Table G.2 : Flood Routing Results...... G-3 Table G.3 : Dam Crest Selection ...... G-4 Table H.1 : Likelihood of occurrence criteria for threatened species ...... H-6 Table H.2 : PCT and legal status of mapped vegetation communities within the study area...... H-7 Table H.3 : TSC Act Threatened Ecological Communities potentially occurring in the study area ...... H-9 Table H.4 : EPBC Act Threatened Ecological Communities potentially occurring in the study area ...... H-9 Table H.5 : Threatened flora species with a 'preliminary' moderate likelihood of occurring in the study area.. H-11 Table H.6 : Threatened fauna species with a 'preliminary' moderate likelihood of occurring in the study area H-12 Table H.7 : Summary of direct impacts to native vegetation ...... H-14 Table H.8 : Summary of direct impacts to threatened ecological communities...... H-15 Table H.9 : Conceptual Site Contamination Model ...... H-19 Table H.10 : Consequence Scale ...... H-20 Table H.11 : Likelihood Scale ...... H-20 Table H.12 : Risk Matrix ...... H-20 Table H.13 : Risk Ranking...... H-21 Table H.14 : AHIMS sites within the Mole River assessment area ...... H-29 Table H.15 : Description of Historic Heritage sites detailed in Rich and Rosen (1991) ...... H-33 Table H.16 : Registered Historic Heritage Sites ...... H-36
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Executive Summary
The Border Rivers’ catchment economy is heavily dependent on agriculture, specifically from dryland and irrigated cereals, dryland livestock, and irrigated cotton. Cotton is heavily dependent on having a regulated water supply. Water supply has low reliability and this undermines agricultural productivity. Poor security of water supply is a barrier to agricultural investment and that, with improved certainty of supply during drier years, there would be potential to convert farming enterprises to higher value crops. Improving water security is the key objective of the feasibility study as per the Commonwealth-NSW NWIDF Feasibility Funding bi-lateral schedule.
Several potential dam sites have been studied in the past, with the Upper Mole River Dam emerging as the most favourable. This study has been focussed on the Upper Mole River site.
This document aims to provide: · A needs assessment or “case for change” · A review of previous needs assessments · A desktop review of previous feasibility studies of major storages in the Border Rivers area, · A review of engineering feasibility, based on the current need · Updated desktop specialist studies (environmental, cultural heritage & others) · A Cost Benefit Analysis (CBA) · Concluding recommendations and next steps.
Need
Two primary needs have emerged from this study:
1. The low reliability of the water supply will continue to erode agricultural productivity in the Border Rivers Catchment
2. Low security of supply prevents long-term on-farm investment that supports the local economy.
Meeting the Need
Water resources modelling results indicate that a 100 GL dam results in a a 27% increase in the demand supplied. Options for 200 and 300 GL were also assessed but the larger dams provide limited further increase in water supply.
The geology review has indicated that underlying rock at the site is of high strength, but is likely to break down upon extraction, and is not thought to be suitable for the construction of an embankment dam. Instead, it is anticipated that igneous rock quarried form a source 1km away would be used. Further field investigations would provide an opportunity to refine conservative engineering and cost estimations.
Concept designs for all three options were prepared and costed, and it emerged that costs were sensitive to the availability and quality of locally sourced materials. The degree of uncertainty is such that significant field work needs to be undertaken before a final configuration and dam type can be selected.
The desktop environmental assessment revealed potential biodiversity, contaminated land and water quality risks. These preliminary assessments require further investigation to better understand their significance and impact on the final design and cost.
It is recommended that an Aboriginal Cultural Heritage Assessment Report (ACHAR) involving a field assessment of the upper Mole River area alongside relevant Indigenous stakeholders be undertaken, to determine the relevant extent of existing registered Aboriginal cultural places and evaluate if any more are
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apparent within the area. It is recommended that the heritage listed Arsenic mine be avoided where possible to limit environmental risks and the associated mitigation costs.
Economic Viability
Based on the preliminary hydrological assessment undertaken to date and the current assumptions in the CBA, none of the options considered are economically viable. Discount rates lower than 3% are necessary for the Mole River Dam to be economically viable.
For any of the options to be economically viable there is a need for greater land-use change from improved water reliability and security. Therefore, further consultation with irrigators to better understand likely land-use changes from improved water reliability and security is a priority.
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Introduction
Jacobs was appointed by WaterNSW to undertake the National Water Infrastructure Development Fund (NWIDF) Mole River Dam Feasibility Study. The objectives of the study are: - To investigate the technical and financial feasibility of a major water storage on the Mole River to provide supply security to users in the Border Rivers catchment, and - Assist the NSW Government in its application for the Mole River Dam capital funding by preparing the content and supporting documents for the EOI submission.
This document is a study of the technical and economic feasibility of a dam on the Upper Mole River. The report is divided into three parts as shown in the figure below, followed by a set of appendices.
The Border Rivers catchment
The Border Rivers include the catchments of Dumaresq, Severn, Macintyre and Barwon Rivers. The Dumaresq River, Macintyre River and section of the Barwon River downstream of the Weir River form the state boundary between New South Wales and Queensland.
The catchment covers an area of 49,500 square kilometres, of which just under half (24,500 square kilometres) is in the NSW portion of the catchment (NSW DPI, 2015a). In total, the Border Rivers population (NSW and Queensland) is approximately 76,000 people. A map of the Border Rivers system and its location is provided in Figure 1 (WaterNSW, 2016).
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Figure 1 : Border Rivers System Schematic Map (WaterNSW, 2016)
The Border Rivers system is regulated by three dams, being: · Pindari Dam - Water stored in Pindari Dam (312 GL capacity) is shared amongst NSW users only · Glenlyon Dam - Water stored in Glenlyon Dam (254 GL capacity) is shared between NSW (up to 57%) and Queensland water users (up to 43%) · Coolmunda Dam - Water stored in Coolmunda Dam (69 GL capacity) is exclusive for Queensland users. The catchment has summer-dominant rainfall with high variability and this affects river flows from season to season (The NSW Agriculture, 2003).The main agricultural uses are grazing and dryland cropping, and this covers approximately 85 percent of the catchment (Green et al 2012).
The catchment includes Inverell, Glen Innes Severn, Moree Plains, and the Gwydir local government areas (LGA) and the Tenterfield statistical local area (SLA) in NSW and the Goondiwindi LGA and the Stanthorpe and Millmerran SLA in Queensland. Inverell is the largest centre in the catchment with a population of about 16,483 (ABS, 2016).
Border Rivers Irrigation
The Border Rivers’ income is heavily dependent on agriculture, specifically from dryland livestock (beef cattle), dryland and irrigated cereals and irrigated cotton (NSW Agriculture, 2003). Cotton is heavily dependent on regulated water supply due to the high evaporation losses of supplementary water (unregulated water) during periods when it is most needed. Approximately 2% of the land is used for irrigation, of which cotton accounts for the majority (quoted figures have ranged from approximately 70% to 90%). The production of cotton mainly occurs on the western plains
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between Goondiwindi and Mungindi (Green et al 2012). Other irrigated crops include fruit, vegetables, wine grapes, lucerne, cereal crops, corn, peanuts and fodder for feedlots.
The distribution of irrigation land use between 2011 and 2016 within Border Rivers is summarised in Figure 2 below.
Figure 2 : Distribution of irrigation land use in Border Rivers (data provided by Border Rivers Commission1) Whilst cotton is the dominant crop across the whole catchment, the NSW Border Rivers tends to have a higher percentage of its irrigated area dedicated to cotton as shown below.
1 Data for 2013-14 was not made available
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Figure 3 : Distribution of irrigation land use in NSW and Qld Border Rivers (data provided by Border Rivers Commission2)
Institutional arrangements in the Border Rivers
The Border Rivers regulated system is located in the States of Queensland and NSW, with a significant proportion of the State boundary located along major rivers in the Border Rivers Catchment (i.e. the Dumaresq, Macintyre and Barwon Rivers).
The New South Wales-Queensland Border Rivers Agreement 1946 (the Agreement), as ratified by the New South Wales-Queensland Border Rivers Act (QLD 1946, NSW 1947) (the Act), contains water sharing arrangements for the Border Rivers, and provisions for the construction and operation of certain storages.
The Dumaresq-Barwon Border Rivers Commission (Border Rivers Commission or BRC) was established under the Agreement. The BRC is responsible for controlling the operation and maintenance of jointly owned water infrastructure (shared assets), determining water volumes under water sharing rules, and reporting and making recommendations to the Queensland and NSW state governments.
Water sharing arrangements in the Border Rivers
The Intergovernmental Border Rivers Agreement between NSW and Queensland, established by the Border Catchments Ministerial Forum contains water sharing arrangements for the Border Rivers, and provisions for the construction and operation of certain storages. In particular, it addresses the following: · Bulk water sharing between the States · Common environmental flow rules · Water allocation and access · Interstate trading · Coordinated monitoring and reporting.
Under the terms of the Act and the Agreement, BRC directs the distribution of water which is made available to Queensland and NSW.
2 Data for 2013-14 was not made available
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Each state is responsible for controlling the distribution of its share of water from the Border Rivers. The use of the water to which each state is entitled is governed by the legislation in force in the state in question.
Under this arrangement, all water in the Border Rivers during periods of regulated flow, regardless of its state of origin, are shared between NSW and Queensland in the ratio 57:43. The BRC agreed that the 57:43 water sharing arrangements would be reviewed at five yearly intervals or when changes in development or management strategies occurred. Such reviews have taken place in 1986, 1989 and in 1992 following the construction of the second stage of the Pindari Dam.
This water sharing arrangement does not apply to water released into the Border Rivers from either Coolmunda Dam or Pindari Dam. The water from these dams belongs solely to Queensland or NSW respectively.
Queensland’s Border Rivers Resource Operations Plan 2008 (ROP) has priority over the Queensland regulated river sections and the NSW Water Sharing Plan (WSP) establishes surface water sharing provisions within the NSW Border Rivers Regulated River Water Source. The intent of the NSW Border Rivers WSP is to protect the water source and its dependent ecosystems, basic landholder rights, and the entitlements of existing licence holders.
The NSW Border Rivers WSP was introduced in 2009. Prior to this, extractions of supplementary water were referred to as ‘off-allocation’ because the water taken was not counted against the licence holders regulated supply water allocation. It was, however, metered and accounted for as a component of total diversions.
Since 2009, supplementary water in NSW has had its own water access licence arrangements that are independent of general security access licences.
Review of the regulatory and institutional framework
A review of the regulatory and institutional arrangements in the Border Rivers and the potential impact on the proposed investment was undertaken in June 2017. The purpose of the assessment was to: · Understand the regulatory and institutional frameworks that could influence or hinder long-term infrastructure planning in the Border Rivers · Clarify whether the Mole River Dam could or should serve both NSW and Queensland users · Consider how the institutional arrangements may impact project planning, delivery, cost sharing and operation. This section summarises the key findings from the review.
At the time of writing, the BRC was advancing a reform package of the current Border Rivers institutional framework. The reform will require legislation changes in both states covering power, roles, obligations and rights, including new financial arrangements. Some of the key features and responsibilities of the BRC that are relevant to the Mole River Dam are summarised in Table 1. Note that these are based on existing framework and are subject to change when the BRC institutional reform takes effect.
Table 1 : Summary of key institutional arrangement feature and the impact on the proposal
Key institutional Description Impact arrangement feature
BRC area of BRC’s operational area includes Glenlyon Dam, the Border Rivers The Mole River and the proposed dam site responsibility and the intersecting streams is located within this area
Funding of asset The costs of managing and maintaining BRC’s assets are jointly paid Process for funding of asset planning for planning for by both states on a 50-50 basis the proposed Mole River Dam would be consistent with the existing process.
Contracts with end The BRC cannot enter into contracts itself, an impact of which is that Processes for collecting any new revenue users it does not have contracts with end users. WaterNSW (in NSW) and from customers (where applicable) for the
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Key institutional Description Impact arrangement feature
Sunwater (in Queensland) send the invoices to the customers and new dam would be consistent with the returns a portion of collected funds to Government bodies (DPI in existing process NSW and DNRM in Queensland) to pass on to BRC.
BRC staff and The BRC does not have a large dedicated staff. Rather it draws The BRC would have limited in-house infrastructure delivery upon the expertise of its independent Chairman, Commissioners and capacity to deliver a major capital project, capabilities Management Committee and service providers such as WaterNSW. and would need too assistance (staffing With the exception of BRC’s Secretary, who is a full time resource and funding) to engage external advisors. for BRC, other staff are general part time. This requirements needs to be managed to reduce duplication, planning delays etc.
Asset maintenance, BRC is responsible for, but SunWater delivers and advises on, asset If Mole River Dam is a shared resource renewal and maintenance and renewal. between NSW and Queensland, it is management Similarly, BRC is responsible for, but SunWater delivers and advises assumed that either of the BRC’s current on asset management, potentially with a short-term focus (the next service providers, i.e. WaterNSW or five years). SunWater, will be given the responsibility of the dam’s maintenance, renewal and management, as per the current situation.
Water pricing End user pricing in BRC’s area is not subject to detailed price If the Mole River Dam is funded, there is an regulation. opportunity for institution reform to better In Queensland, charges have not been reviewed since 1999. In link pricing to cost. NSW, IPART passes-thru BRC charges without assessing costs for prudency and efficiency. All BRC charges have been indexed over time and may no longer relate to underlying costs. In June 2017, however, IPART restructured BRC charges in NSW to be 80% fixed. This manages DPI Water’s (but not BRC’s) revenue risk.
Treatment of proposed Mole River Dam as a shared asset
The BRC Act (Sections 35 and 42) defines Mole River Dam as a shared asset. However, there may be a case for treating the proposed dam as a NSW only asset (like Pindari Dam) if this is the agreed position of Queensland, the BRC and NSW. If the proposed Mole River Dam is treated as a shared asset between Queensland and NSW, the BRC would be responsible for controlling construction of the dam through a third-party, such as WaterNSW, under the current arrangement. Regulated yield arising from the proposed Mole River Dam would enter the Dumaresq River and Macintyre River, downstream of the existing Glenlyon Dam, which forms part of the border between NSW and Queensland.
Studies completed to date
Studies on water storage options in the Border Rivers system have been conducted since the mid-1900s. Several options have been investigated, some of which have led to the construction of storages including the Glenlyon Dam and the Boggabilla Weir.
The feasibility study, and in particular the options selection draws on information contained in the following technical studies – please refer to the full list of citations in Section 9: · Proposed Mole River Dam - Report on Investigations - BRC, 1961 (Water Conservation and Irrigation Commission, 1961) . This investigation led to the construction of Glenlyon Dam on Pike Creek · Options to Provide Additional Storage –BRC, 1984 (The Additional Storages Commission, 1984). Following the completion of Glenlyon Dam in 1976, irrigation development increased and the potential need for more
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water emerged. The investigation concluded that the most cost effective major storage option for the Border Rivers System would be a dam on the Mole River · Report on Mole and Severn River Dam sites - Summary Report on First Stage Investigations – NSW DPI, 1990 (Water Resources Commission, 1990). This study considered a number of options including the Lower Mole River Dam, Upper Mole River Dam and the Lower Mole River Dam with Tenterfield Creek Diversion · Report on Mole and Severn River Dam sites - Supplementary Report on First Stage Investigations, 1991 (Water Resources Commission, 1991). This was a more-detailed investigation of the Upper Mole River site as a supplementary report to the 1990 investigation. This described the results of additional investigative work done for the Mole River sites including limited geological investigations, updated engineering assessments based on the results of the site investigations, and cultural heritage surveys for the upper and lower sites.
The business case has been developed in parallel to the feasibility study, and therefore overlap in the information provided relating to the service needs, details of the shortlisted options and the cost-benefit analysis.
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PART I: The need
Purpose of section · This section of the feasibility study explores the rationale for considering investment in Mole River Dam
Summary of findings · The Border Rivers’ income is heavily dependent on agriculture, specifically from dryland livestock, dryland and irrigated cereals, and irrigated cotton which accounts for over 75% of its total irrigation crops. · Low reliability of water supply erodes on-farm productivity. General security (regulated) licences make up two thirds of irrigators’ water licences and have a low reliability (only receive in excess of 48% of water shares 50% of the time). Supplementary (unregulated) licences make up approximately one third of irrigators’ water licences and are even less reliable. Their average allocation between 2009 and 2015 was 37% (as low as 2% in 2014-15). · High variation in water availability year on year reduces business certainty. Since 2001, annual cumulative water allocations have fluctuated between a low of 2% of water shares to 95% of water shares. Forward planning, selling and investment is extremely challenging under these circumstances. · A significant issue for irrigators in the Border Rivers is lack of water security which refers to the number of years where 0% of water shares are announced. In the NSW Border Rivers, it is projected that general security B water shares would not be available (i.e. zero allocations) for 4 years out of every 100. · Irrigators consider these low security levels to be a major constraint on on-farm investment and their long term financial security. They prevent farmers from converting to higher value land use compromised of permanent tree crops (such as almonds) and create a barrier to long-term financial security for farmers, their employees, supporting businesses and the local communities. This puts pressure on the local population, drives increased unemployment and makes it harder for farmers and other industries to attract high skilled workers to the region. · The objectives for investment in Mole River dam are to (1) improve average annual reliability of water supply to Border Rivers irrigators; (2) reduce the likelihood of zero general security allocations in any given year; (3) Reduce reliance on supplementary water.
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1. Needs assessment
This section of the feasibility study examines the case for change, which is best demonstrated through an examination of the current problems (or service needs) which can be seen as ‘drivers’ for the investment. The ‘case for change’ is further supported by: · Identifying the benefits that arise from addressing the service needs and delivering on the objectives · Demonstrating that the project drivers align with and/or support government requirements and policies · Demonstrating that the project drivers support WaterNSW’s current service obligations and its longer term strategic directions.
The following diagram summarises the case for change, highlighting the service need, objectives and intended benefits which are discussed in the following sections.
Figure 1.1 : Summary of case for change
Table 1.1 summarises the causes and effects of the two service needs in Figure 1.1 above.
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Table 1.1 : Causes and effects of the two service needs
Cause Effect
· Available water can only be delivered in · Water availability is not timed for optimal application ‘boom or bust’ fashion · Land use productivity fluctuates, thereby increasing uncertainty and · High water losses from on-farm dams (built anxiety for farmers to help manage some of this unreliability) · Farmers cannot forward-sell cotton, which limits their financial stability · Water buy-backs (past and planned) in the · Land-use is constrained to annual crops which do not take full region to comply with Basin Plan advantage of the region’s potential · Climate variability (including drought)
· Low water security – meaning that in some · Irrigators cannot make long term investment decisions to shift to years, farmers will receive zero allocations higher value land-use due to the inability to guarantee a minimal · Inability to secure bank loans for annual supply of water investments in higher value / more · Town population and socio-economic profile at risk of decline productive land use. · Inability to attract and/or secure a high value workforce in the region
1.1 Past service need considerations
As outlined in Appendix C, Mole River Dam has been the subject of several studies in the past. The most recent investigation, undertaken in 1990/91 by the Border Rivers Commission identified the need for a new dam based on the following: · Upon completion of Glenlyon Dam in 1976 there was a significant increase in irrigation development and it became clear that there was additional demand for irrigation water than could be provided by the dam. The construction of a re-regulating weir near Boggabilla on the Macintyre River in 1992 was only considered to be a short term solution due to its limited capacity to satisfy the continually growing demand for water. · The area licensed and authorised for irrigation from the Border Rivers had grown to an extent that it could no longer be reliably serviced from the NSW share of regulated flows in Glenlyon Dam and downstream tributary flows. · NSW licensed allocations from regulated flows were equivalent to 241,000 ML and there was an embargo on further issuing of licences. On-farm dam capacity was 65,000 ML. In Queensland, licensed allocations from regulated flows were 63,000 ML. The total capacity of on-farm storage was estimated at 24,300 ML. · The average area that could be irrigated annually was estimated at 30,700 hectares using 98,000 ML of regulated flow and 84,000 ML of unregulated flow. Reliability of water was estimated at 45% of licensed allocations in 45% of seasons in NSW and 100% of licensed allocation in 60% of seasons in Queensland. · In NSW, the authorised area for irrigation was 39,000 hectares and the estimated area irrigated was 28,000 hectares. The upper limit of land suitability for irrigation development in NSW was estimated at 127,000 hectares. In Queensland the upper estimate of land suitable for irrigation in the lower reaches was estimated at 79,000 hectares. The area irrigated was estimated at 5,000 hectares. · In response to the above shortfall in supply and the potential for increased irrigation, the NSW Government (then the Department of Water Resources) investigated the feasibility of enlarging Pindari Dam to deliver 100% of licensed allocations in 70% of seasons. This was defined as the optimal level for economic operations.
Since the completion of the previous studies in 1991, there have been some significant policy, climatic and development and infrastructure changes that have an impact on the service needs. The key changes that are relevant to the service need are discussed below.
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Enlarging Pindari Dam The Pindari Dam, situated in the Severn River was built between 1967 and 1969 with an original capacity of 38 GL. In 1995 the height of the dam wall was almost doubled from its original 45 metres and the dam’s storage capacity increased to 312 GL, more than eight times its original size. The dam is used to meet regulated flows in NSW for irrigation, stock and domestic use, town water supplies and industrial use along the Severn and Macintyre rivers upstream of the Dumaresq River junction.
Crop Mix Over the period 1988/89-2000/01, cotton was on average 88% of the area of total irrigated crops in NSW, and 79% in Queensland. The proportion of total area remained practically unchanged after the Pindari enlargement in NSW, whereas it increased from 72% to 87% in Queensland for the same period (NSW DPI, 2013).
On-farm storages
A significant portion of water availability in the Border Rivers catchment is based on opportunistic access to water supplies (supplementary water in NSW and unsupplemented water allocations in Queensland). (Commonwealth Environmental Water Office, 2014). Opportunistic use of unregulated flows is less effective for cotton farming because timing of watering is important for crop development. Cotton farmers will therefore place more importance on expected regulated flows when considering the annual cropping area (i.e. the availability of regulated supply at the start of the cotton growing season significantly impacts the area of cotton planted each year).
Given the lower reliability of supplementary (NSW) and unsupplemented water (QLD), and the recent hold on building new public dams, landowners have been encouraged by irrigator groups (such as the Border Rivers Food and Fibre) to develop their own storage capacity on farm (MDBA, 2010). Even without encouragement it is a viable commercial strategy that has been adopted by many irrigators, to regulate the availability of water during the growing season.
The 1990 study estimated on-farm storges at 24 GL. Data on current on-farm storages varies, but indicates strong growth in private investment in on-farm dams. For example: · The water sharing plan (2009) estimates storage to be approximately 155 GL (NSW side) and 300 GL in Queensland · More recent data provided by the Border River Commission estimated that in 2015-16 off-stream storages were approximately 180 GL in NSW and 280 GL in Queensland. The difference in on-farm storage capacity between the jurisdictions capacity can in part be explained by the fact that NSW has over three times as much headwater storage as Queensland. In Queensland, therefore, irrigators are more reliant on access from natural tributary flows (NSW Department of Water and Energy, 2009b). In addition, we understand that different approaches to water planning have encouraged more investment in Queensland. For example, water harvesting licences were more secure in Queensland, justifying a higher degree of capital investment (as there is less risk of the entitlement being eroded over time). In NSW on farm storages could include not only floodplain harvesting but also licenced water · The CSIRO sustainable yields report (2007) estimated a 14% increase in on-farm storage to 2030 (though this was from a lower baseline than is contained in the Water Sharing Plan). On-farm storages effectively convert supplementary (NSW)/unsupplemented (QLD) water entitlements into a more reliable source of water. With a total farm-dam volume in the Border Rivers comparable to the public storage of the three existing dams in the Valley, these investments demonstrate the importance that irrigators place on a more reliable or ‘regulated’ water supply compared to unregulated water.
Basin plan, Sustainable Diversion Limits and buybacks
The key policy change in the Murray Darling Basin impacting irrigation licences since the previous investigations is the Basin Plan, prepared and overseen by the Murray-Darling Basin Authority (MDBA). This plan is a legally enforceable document that provides for the integrated management of all the Basin’s water resources.
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A key element of the Basin Plan includes defining Sustainable Diversion Limits (SDLs) which are enforceable environmentally sustainable limits on the quantities of surface water and groundwater that may be taken from Basin water resources. The SDLs are progressively being introduced across the Basin and will limit the quantity of surface water and groundwater that may be taken from the Basin water resources as a whole. There will also be SDLs to limit the quantity of surface water and groundwater that can be taken from individual water resource plan areas and particular parts of water resource plan areas within the Basin. The Basin Plan sets to achieve the SDLs by 2019.
The Border Rivers system is fully-allocated, meaning that new investment in water supply cannot be used to create new licences. If the environmental flows can be delivered more efficiently, a potential reduction of planned buybacks in the Border Rivers will be negotiated separately with the MDBA. However, this does not create an opportunity for additional allocations to be created for productive use.
The gap between previous diversions and the SDL is being met using a range of measures, including infrastructure investments and licence buy-backs. Based on a recent review of the socio-economic outcomes from water recovery in the northern basin (MDBA, 2016), 36 GL of water is to be recovered in the Border Rivers to meet the SDL requirements (29 GL in Queensland and 7 GL in NSW). To date, less than 50 percent of this target has been recovered –15 GL in Queensland and 3 GL in NSW.
Climate
The impact of climate change in the region is uncertain. The CSIRO Murray-Darling Basin Sustainable Yields Project included several climate change scenarios (CSIRO, 2007). Under the best estimate 2030 climate scenario, the following projections were made: · Water availability would be reduced by 9%, end-of-system flows by 12% and total diversions by 2% · The impacts on diversions would differ by ‘water product’. In NSW both general security and supplementary use would fall by 1%. In Queensland, both medium priority and unregulated (i.e. unsupplemented) allocations would fall by 3%. Town water supply would be unaffected as it is generally derived from a high security (NSW) or high priority (Queensland) water allocations.
1.2 Revised service need
To support an updated feasibility assessment and business case for the Mole River Dam, the service need was revisited. A workshop with representatives from WaterNSW and the Border Rivers Commission was held on 20th June 2017. This workshop sought to identify and explore the key drivers for change, objectives and intended benefits. It took into consideration the impacts of the key changes in policy, climate, and infrastructure investments (public and private) that have occurred since the previous studies. Key drivers for change are discussed in more detail below. Please refer to Appendix B for evidence supporting service needs.
1.2.1 Service Need 1: Unreliable water supply
Service Need 1: Unreliable water supply, will continue to erode agricultural productivity in the Border Rivers catchment
Water supply to irrigators in the Border Rivers is made up of a combination of general security and supplementary supply, with a significant portion of the water entitlements being supplementary. This means that water is supplied in a ‘boom or bust’ fashion.
Based on long term water supply simulation undertaken by the NSW Department of Primary Industries (DPI), General Security B receives in excess of 48% of the water shares, 50% of the time3. This is very low, considering that general security licences form approximately two thirds of total water shares for irrigators, with
3 This is the main regulated water licence in NSW.
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the remainder being unregulated water which is even less reliable. (Refer to Appendix B, Section B.1.1 for relevant reliability chart)4.
Unregulated water may also not be available at important times in the growing cycle and cannot be carried over, so water from a wet year cannot be carried forward for a dry year.
Unreliable water supply leads to financial uncertainty and anxiety for farmers and their communities. Low reliability of water supply leads to significant variations and uncertainty in irrigators’ on-farm decisions and their annual production. In response, farmers are forced to plant smaller areas of crops based on their estimates of water availability at the start of the planting season. Annual variations in water availability also limits the ability of irrigators to establish higher value fruit and nut plantings which require reliable annual water to ensure a long- lived and capital intensive investment is not lost to drought (i.e. it is not commercially advisable to invest heavily in ‘permanent’ tree crops that may take several years to deliver a financial return, if due to uncertainty of supply the whole investment could be lost in a dry year).
The western part of the Border Rivers catchment where most of NSW’s cotton is grown has lower rainfall, higher evaporation and higher temperatures than the eastern part of the catchment (NSW Agriculture, 2003). Given that irrigation water is needed during summer when evaporation is greatest, on-farm planning based on unregulated water is particularly problematic.
As discussed in Section 1.1, farmers have taken active measures to invest in on-farm storages to help improve the reliability of unregulated supplies. However these dams are expensive to build and incur significant water losses through evaporation. This means that the water available for use from on-farm storages is significantly less than what is extracted from the catchment.
Water availability, and potentially reliability is expected to deteriorate even further due to the final stages of the Basin Plan implementation. As discussed in Section 1.1, an additional 36 GL of water is yet to be recovered from the Border Rivers to meet the SDL requirements, with 7 GL to be recovered from NSW. This is equivalent to 2.6% of the general security licence volume in the NSW Border Rivers.
During preliminary consultation undertaken for the feasibility study, irrigators have advised WaterNSW that they are seeking higher reliability of the “general security” water to provide the certainty they need for: · More productive land use decisions – including planting area (more of the same crop) · Shifting to high value land use which includes up-front capital investment to change crop types (e.g. from cotton to nuts). High variability in water availability means that a shift to higher value horticulture is generally seen as being too risky. · Forward selling cotton. In the absence of more certainty about the reliability of supply, farmers are limited in their ability to forward sell their cotton. Prices set by the world market are impacted by a range of worldwide factors such as politics, economic conditions and weather. Cotton prices have ranged from AUD $300 to $600/bale. The all-time high was $758/bale in 1995 while the all-time low was $233/bale in 1986 (Cotton Australia, 2016). The ability to forward sell cotton allows farmers to manage some of the commercial risk associated with price variability, to the extent that yields can be reliably predicted. The ability to take advantage of the futures market is reduced if water availability and production can vary drastically. That is, if forecast yields are less than a contracted amount, farmers must buy cotton at market prices to fulfil the contract - risking substantial financial penalties or losses.
Table 1.2 summarises the issues underpinning Service Need 1 (the cause) and the associated impacts (effects). It also lists the relevant evidence that is discussed in more detail in Appendix B.
4 This is the main regulated water licence in NSW.
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Table 1.2 : Service Need 1: Summary of cause, effect and relevant evidence
Summary of cause Summary of effect Relevant evidence
(in Appendix B)
· Available water can only be · Water availability is not timed for · Existing water entitlements delivered in ‘boom or bust’ fashion optimal application available to irrigators in the Border · High water losses from on-farm · Land use productivity fluctuates, Rivers and their relative reliability dams built to manage some of this thereby increasing uncertainty and · Estimated water losses in delivery lack of reliability anxiety for farmers and on on-farm dams. · Water buy-backs (past and · Farmers cannot forward sell planned) in the region to comply cotton, which limits their financial with Basin Plan stability · Climate variability (including · Land-use is constrained to annual drought). crops which do not take full advantage of the region’s potential.
1.2.2 Service Need 2: Constrained long term investment
Service Need 2: Low security of supply prevents long-term on-farm investment that supports the local economy
A significant issue for irrigators in the Border Rivers is lack of water security. While linked to water reliability discussed above, security specifically refers to the number of years where 0% of water shares are announced. As shown in the long term simulation of reliability in the catchment, general security B water shares are projected to not be available (i.e. zero allocations) for 4 years out of every 100. Further, less than 10% of the water shares are projected to be available 8% of the time. Irrigators consider these security levels to be a major constraint on on-farm investment and their long term financial security.
Of key concern is the impact that low security water supply has on-farmers wanting to shift from cotton to growing higher value crops (e.g. fruit and nuts). These land use changes require significant on-farm investment (estimated at approximately $18,000 per hectare for land establishment cost plus more than $1,200 per hectare per annum for equipment costs)5 and farmers are unwilling to undertake that investment under current water security projections. This water security risk has also been identified by farmers as a key barrier to securing bank loans for investment.
This constraint on shifting to higher value land use not only impacts the farmers but also the broader community. The continual high dependence on annual crops which vary in productivity from year on year does not offer the local communities the long term certainty needed to sustain the supporting industries and businesses. This puts pressure on the local population, drives increased unemployment and makes it harder for farmers and other industries to attract high skilled workers to the region.
The socio-economic profile of the Border Rivers demonstrates the impacts of this uncertainty. The region has lower population growth, higher unemployment, and lower education levels than other regional areas benefiting from higher water security.
Table 1.3 summarises the issues underpinning Service Need 2 (the cause) and the associated impacts (effects). It also lists the relevant evidence that is discussed in more detail in Appendix B.
5 These assumptions are discussed in more detail as part of the cost benefit analysis in Section 6.1.3.
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Table 1.3 : Service Need 2: Summary of cause, effect and relevant evidence
Cause Effect Relevant Evidence
(in Appendix B)
· Low water security – meaning · Irrigators cannot make long term investment · Potential of higher that in some years, farmers will decisions to shift to higher value land-use due to value land use receive zero allocations the inability to guarantee a minimal annual supply of · Barriers to investment water · Inability to secure bank loans for · Importance of water investments in higher value / · Town population and socio-economic profile at risk security for the local more productive land use. of decline community. · Inability to attract and/or secure a high value workforce in the region.
1.3 Objectives The objectives associated with addressing the service needs support WaterNSW’s corporate objectives, roles and functions as well as government objectives. These include:
Improve long-term water availabilityWaterNSW customers in the Border Rivers have expressed dissatisfaction with security and reliability of their water supply and are concerned that the impact on their productivity and financial stability will be exacerbated when the final stages of the Basin Plan are implemented.
A key objective of this project is to better align the level of service offered with irrigators’ needs and expectations where this offers value for money. Subject to economic viability testing, this objective targets: · Improving average annual reliability of water supply to Border Rivers irrigators · Reducing the likelihood of zero general security allocations in any given year · Reducing reliance on supplementary water, and thereby shifting more of the water shares to general security which can be allocated more reliably, conveniently and with reduced water losses
Realising the economic potential of the region
The second objective extends to the broader region, recognising that a stable and successful irrigated agriculture sector will benefit supporting industries and businesses and in turn help improve the resilience of the regional economy.
The objective aligns with the broader National Water Infrastructure Development Fund (NWIDF) objectives and the rationale for investment in water infrastructure. A more stable irrigated agriculture sector that has the certainty needed to invest in its longer term sustainability and growth will drive job growth and job security across all supporting services.
Job security will increase population growth and encourage those with higher skills to stay in the region or to move to it which will help drive further innovation and productivity.
Subject to economic viability testing, the objective targets are: · Facilitating farmers to invest in more stable and valuable land-use options · Smoothing out irrigation output over the years to provide greater stability and certainty for both farmers and their supporting businesses · Facilitating population growth in the region.
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Facilitate more efficient and equitable management of Basin Plan objectives.
The Basin Plan objectives are to ensure a minimum volume of water is available for the environment and this ultimately leads to SDLs which reduce the volume of water available for other uses (Refer to Section 1.1). A key objective of addressing the service need is to improve the reliability and security of existing water licences whilst still delivering the environmental objectives contained in the Basin Plan. This could potentially include any of the following: · Meeting the environmental objectives more efficiently – for example with less water but more effective targeted releases. This could free up more water for consumptive use with no impact on environmental outcomes. · Reducing water losses so that the reliability of water supply can be improved without reducing water available for the environment. · Being more efficient with available water so that environmental and consumptive needs can be met more equitably.
1.4 Intended benefits
The intended benefits to be realised from addressing identified service needs include the following: · Improved on-farm productivity. The primary and most direct intended benefit will be improvement of on- farm productivity as a result of more reliable and secure water supply to existing licence holders. Irrigators will be able to grow more of their existing crops and to use a portion of their land to grow higher value crops · More stable and resilient local communities. Being able to smooth out irrigators’ production from year to year will help secure existing jobs and create new employment opportunities in nearby towns. This will sustain and grow the local population and economy. It will also attract a higher skilled workforce that can further improve the comparative advantage of the regional economy.
Table 1.4 : Benefit summary
Benefit Intended beneficiaries Link to relevant objectives
Improved on-farm · Irrigators – including more reliable and higher · Improve level of service in line with productivity earnings customers’ needs and expectations · Farm employees – more stable on-farm jobs · Realise economic potential of the region · Farm suppliers – more consistent demand for supplies and improved earning potential · WaterNSW – better alignment with corporate objectives and improved reputation
More stable and resilient · Local residents – improved service provision, · Realise economic potential of the region local communities amenity and recreation from more populated · Facilitate more efficient and equitable and liveable communities management of basin plan objectives. · Local business owners – improved financial security, resilience to change, growth opportunities and access to skilled workforce · Local employees – more employment opportunities, improved job security and wages · Government – more equitable utilisation of government assets, improved efficiency of government policies (predominantly Basin Plan), and reduced burden of supporting struggling local economies (e.g. welfare payments and community facilities).
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The above are the intended benefits of addressing the service needs. The benefits that are specific to the investment option considered are discussed further in the economic appraisal of the considered options (Section 6.1).
1.5 Discussion
The Border Rivers irrigation system is fully-allocated, with in excess of 48% of the General Security B water shares being received 50% of the time, and over 4 in 100 years receiving zero water supply. This has led to the (service) needs to: · Increase the reliability of existing water entitlements · Remove constraints on long term investment by increasing the security of water supply.
Farmers have attempted to partially address these service needs through storing unregulated water in on-farm storages. However the reliability of supply of supplementary water combined with high water losses (potentially as high as 40% through evaporation) limits the effectiveness of on-farm dams as a long term solution. This suggests that a centralised approach to improve reliability of regulated water supply may present comparative (water efficiency) advantages, depending on the cost.
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PART II: Meeting the need
Purpose of section · This section of the feasibility study explores possible ways in which the need, demonstrated in PART I, may be met. · The feasibility of storages on the Border Rivers has been studied at various times in the past. A review of prior studies provided a list of options for consideration. Upon further desktop assessment, a short list of options was produced. · A water resources assessment was undertaken, to better understand the relationship between yield, security of supply and reliability of supply, for each option. · The technical feasibility study included: - Desktop geology review - Flood hydrology study - Dam safety consequence assessment - Engineering · Desktop specialist studies, identifying impacts related to the construction options. Investigations included: - Biodiversity - Contaminated Land - Water Quality - Heritage
Summary of findings · A dam on the Upper Mole River is technically feasible · The type of dam should be chosen once the site and construction materials are better understood · Much further work should be done to reduce cost uncertainties · Several possible environmental, water quality and heritage impacts have been identified at desktop level, and further investigation is needed
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2. Options identification
This section provides a summary of the long list and short list of options considered to address the case for change.
2.1 Non asset options
Non asset options have not been considered in the feasibility assessment. A range of non-asset options have already been approved and implemented in the lead up to the Basin plan and include: · Water licence buy-backs to address over allocation across the MDB. · On-farm efficiency improvements through the Sustaining the Basin: Irrigated Farm Modernisation (STBIFM). This program being delivered by the NSW DPI funds irrigators to update irrigation infrastructure in the NSW Border Rivers, Gwydir, Namoi/Peel, Macquarie/Cudgegong and NSW Barwon–Darling water management areas. This efficiency improvement program aims to reduce the direct extraction of water from each catchment · Capacity building, skills development and information sharing to facilitate improved water efficiency. For example, NSW DPI’s STBIFM program and CottonInfo recently hosted a three day tour where cotton growers, irrigators and consultants from northern NSW, Darling Downs (QLD) and Kununurra (WA) visited the southern NSW irrigation industry to look at some of the different irrigation layouts and automation systems in action. The purpose of these visits was to share information on how efficiency and yield can be improved through more precise scheduling and application technology. These non-asset options to improve efficiency and reduce demand have played an important role in managing over allocation in the Basin. This feasibility assessment outlines options for a new dam in the Border Rivers Catchment that would be needed to improve the reliability and security of supply, in line with the needs outlined in Section 1.2.
2.2 Review of long list of dam site options
Figure 2.1 summarises all the dam site options considered in past reports and studies according to their location, engineering requirements, hydrological assessments and environmental impact and summarises the reason why the site option has been dismissed or considered further as part of a more detailed analysis. A more-detailed discussion on previous reports is included in Appendix C. The Upper Mole River site is the only dam site that is considered in more detail in the feasibility assessment and business case.
The Upper Mole River site offers the hydrological flexibility needed and the most straightforward and manageable environmental conditions. The Lower Mole site is the next best option; however more extensive studies and consultation would be required to address the higher environmental uncertainty. It is expected that the need to manage and mitigate environmental impacts would lead to higher costs and project delays for no additional benefits. As such, this option has not been considered further in the feasibility study.
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Shortlisted for further Option Engineering Hydrological Environmental analysis?
YES: Economic assessment Satisfactory yield Satisfactory: No “show suggests this would be the Upper Mole River Feasible: Rockfill dam achievable stoppers” lowest cost option for the same benefit
Satisfactory yield Lower Mole River Feasible: Rockfill dam achievable NO: For the same benefit that Moderately challenging: could be delivered for Upper Aboriginal site & Arsenic Mole site, deliverability would Mine would create be more challenging and cost approval challenges and would be higher due to the Lower Mole River with increase costs Satisfactory yield environmental constraints. Tenterfield Creek Feasible: Rockfill dam achievable Diversion
NO: Yield constraints Would Enlargement of Feasible: Spillway gates Satisfactory: No “show not deliver the required Unsatisfactory yield Glenlyon Dam 8,5m high stoppers” reliability and the service need wold not be addressed
Areas of high cons. value Enlargement of Feasible: Spillway gates Satisfactory yield inundated; diversion Glenlyon Dam with 8,5m high achievable located within Sundown NO: Challenging Severn River Diversion National Park environmental conditions would be difficult to manage, imposing barriers to construction and / or high Areas of high Feasible: Concrete faced Satisfactory yield mitigation costs Dam on Severn River conservation value rockfill dam achievable inundated
Challenging: Alluvi al soils Dam on Dumaresq River up to 75m deep & wide NO: Engineering costs did not No further investigation No further investigation at Mingoola dam site increase merit further investigation complexity and cost
Figure 2.1 : Overview of dam site options (green = feasible/satisfactory, amber= moderately challenging red = unsatisfactory/ challenging)
2.3 Short list of options
The Upper Mole River site poses the hydrological flexibility needed and the most straightforward and manageable environmental conditions. The Lower Mole site is the next best option; however more extensive studies and consultation would be required to address the higher environmental uncertainty. It is expected that the need to manage and mitigate environmental impacts would lead to higher costs and project delays for limited additional benefits. A dam at the Lower Mole River has therefore not been considered further in the business case. For this study, options of 100, 200 and 300 GL at the Upper Mole River dam site have been considered.
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3. Water resources hydrology
3.1 Background
The needs analysis for the Upper Mole River Dam identified that an understanding of the impact on reliability of supply of the new dam was critical to understanding its benefits.
The technical assessments in this feasibility study were based on modelling outputs provided by WaterNSW to Jacobs. Jacobs understands that WaterNSW developed a simplified Border Rivers model for the feasibility study to carry out water balance analyses and to assess the impact of a new dam on the Upper Mole River on reliability of supply. The model focused on the headworks system of the existing Pindari and Glenlyon dams, and the Upper Mole River. Jacobs did not review the modelling inputs, assumptions, model simplification methods, and results. WaterNSW owns the responsibility of the accuracy of the modelling results and has provided a technical note on the modelling provided at the end of this section.
It is understood that the model is simplified and only provides indicative results. It is strongly recommended that as a next step the impact of the Upper Mole River Dam be assessed using a detailed system model.
3.2 Results
The simplified model was used along with outputs from the base case IQQM model (provided by DPI to WaterNSW) to estimate changes in the system resulting from various Upper Mole River Dam options. Daily time series were generated over the 1912 2014 climatic period for: · Available Water (assuming all water in the new dam goes to NSW) · Available Water (assuming 50:50 split of new dam) · General Security B allocation (assuming all water in the new dam goes to NSW) · General Security B allocation (assuming 50:50 split of new dam) · Demand supplied (total).
Water availability as at the first of October each year was reported as a measure of system reliability. For the case that assumes that all water in the new dam is allocated to NSW, the following allocations were estimated for each of the options considered: · Base case: Allocations of 49% or above were achieved in 50% of years · 100 ML dam case: Allocations of 66% or above were achieved in 50% of years · 200 ML dam case: Allocations of 71% or above were achieved in 50% of years · 300 ML dam case: Allocations of 71% or above were achieved in 50% of years · 500 ML dam case: Allocations of 71% or above were achieved in 50% of years.
This measure is referred to as system reliability. System security is a measure of the likelihood of ‘system failure’. In rural valleys, system failure relates to the percentage of time with zero announced allocation for general security licence holders. For the case that assumes that all water in the new dam is allocated to NSW, the following system security was estimated: · Base case model run: 4.8% of years with zero allocation · 100 ML dam case: 1.9% of years with zero allocation · 200 ML dam case: 1.9% of years with zero allocation · 300 ML dam case: 1.9% of years with zero allocation · 500 ML dam case: 1.9% of years with zero allocation.
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These security results should be considered as indicative only. The inaccuracies resulting from the many simplifications in the Source model are amplified in drought times, in particular the way demand is estimated.
Figure 3.1 : 1st October allocation for general security B licences – all water to NSW case
Total Average annual regulated demand supplied to both QLD and NSW was reported. Whether NSW received 50% or 100% of additional regulated demand depends on the sharing assumption with Queensland. Results are summarised in Table 3.1 and Figure 3.2.
Table 3.1 : Change in demand supplied
Dam size (GL) Average annual demand supplied (GL) Increase in demand supplied (GL)
Base Case 103.5 -
100 131.7 28.1
200 141.3 37.5
300 145.5 41.4
500 146.6 42.3
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Figure 3.2 : Annual exceedance curve of total demand supplied
The modelling results indicate that a 100 GL dam results in a 17% increase in reliability of supply and a 27% increase in demand supplied. Larger dams provide limited further increase in water supply.
It should be noted that this assessment is very approximate and takes into account regulated take only. It is understood that the existence of a new dam would increase regulated flow availability, and reduce downstream unregulated flows and potentially access to supplementary water. The impact of the dam on supplementary water availability use was not modelled, but is constrained as described below.
Diversions from the system are subject to the Murray Darling Basin (MDB) Cap on diversions. The Cap requires that diversions not exceed those that would have occurred under 1993/94 level of development conditions. In 2019, the Cap requirement is likely to be replaced with the MDB Plan Sustainable Diversion Limit. The current SDL for NSW in the Border Rivers catchment is 303 GL. Any increased use of water under general security licences may require a reduction in water use of other licence types including supplementary water in order to comply with Cap (or SDL) requirements.
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· Supply reliability statistics are given for General Mole River – Modelling Notes Security B licenses in NSW. Overview · Regulated use of water is factored up to use the For the feasibility study, WaterNSW developed a simplified additional available water. Increased available water at fit-for-purpose hydrological model for the Border Rivers 1 October is taken to be increase in storage plus water resources system based on a daily time-step. This increase in use-to-date (since 1 July) less new model was used to estimate the increase in the availability commitments. of regulated water, arising from construction of a new Compliance with the Murray-Darling Basin Cap storage on the Upper Mole River. Simulation was carried out for the period 1911 to 2014. The modelling results demonstrate that a new dam on the Mole River will improve reliability of supply, which would The model focuses on the headworks system of the existing likely result in increased regulated water take. Any storages Pindari and Glenlyon, and the Upper Mole River, increased use of water under general security licences may i.e., upstream of gauge 416032. Rainfall-Runoff (RR) require a reduction in water use of other licence types such models were developed to enable estimation of long-term as supplementary water in order to comply with the inflows to each of the storages and the Upper Mole. The RR sustainable diversion limit requirements. Thus, to maintain models were calibrated against calculated storage inflows or compliance with the Basin Plan limit when the Mole River gauged flow data as appropriate. The key features of the dam is built, supplementary take will need to reduce by the model include: increase in average annual regulated take. Modifications to · Regulated demand is a function of available water, and Supplementary access rules will be required to achieve this. the demand is extracted at a lumped location. The long-term average water available on 1 October for · The distribution losses have been lumped in the model General Security B (GS B) allocation has been calculated and assumed to be 30% distribution. The 30% loss for different Upper Mole River dam capacity options and is assumption is based on the NSW DPI Water report of summarised in the table below. For the purpose of this April 2012 “Water resources and management analysis, it is assumed all entitlements with higher security overview Border Rivers Catchment” which reports are fully allocated before water is made available to GS B, setting aside 30% of general security water for losses. and all additional regulated water is allocated to NSW. Current GS B entitlement in NSW is 241,211 ML. The table · The model incorporates the environmental releases also shows the estimated supplementary access reduction from the storages required by the Water Sharing Plan to comply with the Basin Plan limits. for the Border Rivers Regulated System. · The current model does not include supplementary take, but models regulated water use by both NSW and QLD.
Modelled long-term average water available and demand Scenario Average increase in Average Water Average regulated Estimate of average required the release of Available on 1 water demand supplementary access regulated water (ML)* Oct for GS B supplied (ML) reduction to comply with the (ML) Basin Plan limits (ML)**
Base Case - 116,038 103,481 -
Upper Mole River 61,797 147,557 131,782 28,300 Dam – 100 GL
Upper Mole River 75,726 155,644 141,348 37,867 Dam – 200 GL
Upper Mole River 81,606 157,453 145,456 41,974 Dam – 300 GL
Upper Mole River 83,269 157,827 146,586 43,105 Dam – 500 GL * Base case is 147,776 ML **Current Supplementary entitlement in the NSW Border Rivers is 120,000 unit shares
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4. Engineering assessment
The engineering assessment comprises a desktop assessment of factors that influence the design of options and potentially their technical feasibility. The areas are: · Flood hydrology · Geology · Consequence assessment · Dam safety consequence assessment · Engineering
4.1 Flood hydrology
Appendix D presents the full flood hydrology methodology and results. Adopted design peak flows are shown in Table 4.1 below:
Table 4.1 : Design peak flows for the Upper Mole River Dam site
AEP 1 in Y years Adopted Peak (m3/s)
5 330 10 610 20 1,000 50 1,600 100 2,000 200 2,100 500 2,600 1,000 2,800 2,000 3,200 5,000 4,000 10,000 4,600 20,000 5,200 50,000 5,900 100,000 6,600
4.2 Geology
The results of the desktop geological review are presented in Appendix E and summarised below. In summary, the following issues are notable: · Field investigations were limited and inferences that have been made need to be confirmed as soon as practicable · The embankment and spillway sites are believed to be underlain by mudstones of high strength · The mudstone is understood to have high strength and as such would be able to support an earthfill, rockfill, or gravity concrete dam
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· While exhibiting high strength, the rock under the embankment foundation appears to have closely spaced joints, indicating that extensive grouting and a grout curtain may be needed to reduce porosity of the rock mass. · Material won from excavations is not likely to be suitable for use in a rockfill embankment or as aggregate in a concrete dam. The implication is that a large quantity of excavated material would need to be spoiled and more suitable rock quarried elsewhere, at greater cost · It is anticipated that exposed mudstone at the spillway would exhibit poor durability and would require extensive lining and anchoring · The availability of construction materials will need to be confirmed by physical field investigations.
4.3 Dam break consequence assessment
An initial assessment was undertaken to determine the design flood. The design flood was derived from the consequence category as set out in the ANCOLD Guidelines for Consequence Assessment.
The initial assessment concluded that the consequence category for the dam is “Significant”. Details of the consequence assessment are included in Appendix F
4.4 Engineering
Concept designs were prepared for all three options (100, 200 and 300 GL), based on previous studies and an understanding of conditions developed following the background review. As part of the 1990 Summary Report (Water Resources Commission, 1990) an engineering assessment was conducted, however this separate document was not available at the time of writing. When comparing results to those in the concept design shown in the Summary Report, it should be noted that: · The options being considered here correspond with smaller storage sizes than contemplated in the 1990 BRC study · Flood hydrology differs in respect to the calculation methods that are presently available compared with those of the 1990s
4.4.1 Basin characteristics
The water storage and area relationships for the basin formed at the Upper Mole River dam site are shown in Figure 4.1 and Figure 4.2 below.
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1,400
1,200
1,000 ) l M ( 800 e g a
r 600 o t S 400
200
0 440 450 460 470 480 490 500 510 520 530 Water Level (mAHD)
Figure 4.1 : Stage-storage relationship for the Upper Mole River dam site
35,000,000
30,000,000
25,000,000 ) ² m ( 20,000,000 a e r A
e 15,000,000 c a f r u
S 10,000,000 m a D 5,000,000
0 440 460 480 500 520 Water Level (mAHD)
Figure 4.2 : Stage-area relationship for the Upper Mole River dam site
On the basis of the basin’s depth-storage relationship and the spillway characteristic, three dam embankment options were developed, with dimensions given in Table 4.2.
Table 4.2 : Dam options and key dimensions
Capacity (ML) Full Supply Level Dam Crest Level Spillway Length Crest Length (mAHD) (mAHD) (m) (m)
Option 1 100,000 473.0 485.0 59 414 Option 2 200,000 483.0 495.0 59 467 Option 3 300,000 490.5 502.5 59 508
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4.4.2 Dam type
In the 1990 BRC study (Water Resources Commission, 1990), a rockfill dam with central earth core was proposed. Rockfill dams are widely recognised for their safety, practicality and economy (Jansen, 1988).
Following the desktop review of previous studies, rock fill is still considered to be an appropriate technology to apply to this site6. The cost estimate (section 4.5) is based on a rockfill dam; however a roller-compacted concrete dam (RCC) was also conceptualised and costed to form a basis for comparison. Detailed knowledge of the quality and quantity of construction materials will be crucial in developing a suitable final design. It is anticipated that a trade-off between different options related to the availability of imported and locally won materials will emerge.
Referring to the geological review (Appendix E), it has been assumed that mudstone or similar sedimentary rock from foundation and spillway excavations will not be suitable for use in the embankment, and that the large granitic intrusion (Water Resources Commission, 1991) about one kilometre east of the site will provide sufficient rock fill. Further investigation is essential, to determine the suitability and available quantity of this material for construction.
Depending on detailed analysis of rock excavated from the spillway, it is possible that a proportion could be used as “dirty rockfill”. If the excavated rock breaks down to a readily compactible material, an embankment more closely resembling earthfill could also be considered.
The durability of rock in the downstream channel under hydraulic action is uncertain, however given the geological assessment it is anticipated that significant lining of a stilling basin would be necessary.
It is important to note that without the understanding of site conditions that drilling boreholes can provide it is difficult to make engineering assessments with confidence. More detailed-geological field investigations should be undertaken as soon as practicable.
4.4.3 Foundation
The conceptual design is based on the following assessment of foundation conditions, as applied to a rockfill dam: · It is assumed that the strength of the underlying rock is sufficient to support the rockfill embankment · Closely to very closely spaced fractures in the rock suggest that extensive foundation treatment would most likely be needed. This treatment would consist of consolidation grouting, slush grouting and a grout curtain wall, topped by a grout cap · Allowance for dental concrete has been made · Allowance has been made to excavate the weathered surface over what is understood to be competent rock under the embankment to a depth of 4 metres · An extensive grout curtain is most likely required · A cut-off trench under the earth core excavated 2 metres deeper than the remainder of the foundation.
4.4.4 Embankment Certain assumptions have been made in the development of the conceptual embankment design: · Rockfill will be composed of good quality igneous rock, sourced from the intrusion discussed in the Reconnaissance for Sources of Construction Materials report (Water Resources Commission, 1990). · Since the rockfill is assumed to be of good quality, it was assumed that the embankment may be sloped at 1.75H:1V. · An allowance has been made for the protection of the upstream face with riprap.
6 The engineering design was prepared by Jacobs dams engineers and peer reviewed by a leading independent expert in dam engineering in Australia.
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Figure 4.3 : Typical rockfill dam section (outlet not shown)
4.4.5 Spillway
With reference to Appendix F and Appendix G, a design flood of 4800m³/s, corresponding with the 10-4 AEP event, was applied.
The concept design is based on an ogee spillway, cut into the saddle next to the left abutment of the dam. The geological review suggested that rock in the saddle is less deeply weathered than in the hill that forms the left abutment, and that fresh rock was approximately 3 metres deep.
Compared to the concept design of 1990 (Water Resources Commission, 1990), the spillway has been moved farther away from the left abutment towards the adjacent saddle point to reduce the probability of embankment failure as a result of erosion from the spillway.
It is anticipated that the spillway will need extensive lining throughout, and the foundation to be prepared by means of grouting similar to the embankment foundation.
Due to the expense of excavation and lining, the spillway length in this design is relatively short. With a better understanding of the rock characteristics the relationship between spillway length, wet freeboard and embankment height may be optimised. It was assumed that spillway side sloped would need to be cut at 2H:1V to 2.5H:1V, as recommended in the Geology review (Appendix E).
Further detail on the spillway concept is included in Appendix G.
4.5 Cost Estimate
Detailed cost schedules are included in Appendix I. Conceptual estimates have been completed for the three storages. The probable cost range for this type of estimate would typically be ±30% to ±40% (based on ANZ- SOP-2005). Quantities have been taken off conceptual sketches of the options superimposed onto general arrangements. Rates were based on SCA (2010) Infrastructure Assets, Revaluation of Assets for Financial Reporting Purposes – June 2010 escalated from 2010 rates to 2016 rates by CPI.
Cost estimates for the three rockfill dam and roller-compacted concrete (RCC) options are given in Table 4.3 below:
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Table 4.3 : Cost estimates totals for rockfill dam options
100 GL 200 GL 300 GL
Rockfill dam $345,098,000 $388,408,000 $448,328,000 RCC dam $322,970,000 $411,839,000 $492,992,000
This study has been based on a typical rockfill dam design.
Table 4.3 suggests that, for 100GL and 200GL options, rockfill and roller compacted concrete dams will have similar costs. With reference to Section 4.2, there is significant uncertainty about the quality of materials at the site and the source of igneous rock, filter sands and clay core. Furthermore, and with reference to Figure 4.4, earthworks are by far the largest cost component, suggesting that a better understanding of site conditions could provide greater cost certainty and guidance on the most appropriate type of dam.
Figure 4.4 : Cost breakdown for 100 GL rockfill dam
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4.6 Construction schedule
An anticipated high-level schedule is given in the table below:
Table 4.4 : Construction timeframes
Project stage/ works Timeframe
EOI approval 6 months Detailed feasibility including field work, 12 months stakeholder consultation, environmental, planning and Cultural Heritage authorisations, engineering design Final business case preparation and approvals 6 months Detailed design and tender preparation 12 months Construction 3 years Commissioning
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5. Environmental assessment
The environmental desktop assessment is included in Appendix H. Key issues are summarised in the sub- section hereafter.
5.1 Biodiversity
The study area has largely been cleared of the naturally occurring vegetation and is now characterised by extensive areas of agricultural land, both pasture and grazing, with patches of remnant and regenerating vegetation.
Based on a ‘preliminary’ likelihood of occurrence assessment, the threatened flora listed in Table H.5 are considered moderately likely to occur in the study area, based on the presence of suitable habitat. Field surveys are required to confirm the presence or absence of these plants and available habitat from the site.
Although no specific records of threatened species of fauna exist within the study area, there may be potential for some species to occur that are known from the locality. Due to the nature of this desktop assessment, the likelihood of occurrence is considered ‘preliminary’ only. These species would need to be targeted in field surveys during an impact assessment.
The Mole River is part of the indicative distribution of one endangered fish species and two endangered fish populations. Further survey work would be required to determine if the aquatic habitat within the study area is suitable for these species.
5.2 Contaminated Land
Based on the understanding of historical land use of the site, a number of potential contamination sources have been identified which could pose an exposure to human health and/or environmental receptors during construction activities and operation of the project.
To quantify these potential risks, it is recommended that a sampling and analysis program be developed which targets potential contamination sources which could be disturbed as part of construction and operation of the project.
5.3 Water Quality
Potential water quality issues were identified, including: · Algae · Turbidity · Thermal stratification · Cold water pollution · Salinity · Changes to flow regime
More-detailed water quality studies were recommended, should the projct move on to the next stage of investigations.
5.4 Heritage
Preliminary desktop indicates that evidence of Aboriginal occupation is evident in the form of isolated finds and artefact scatters. Many of the reports indicate these scatters do not represent the full extent of these Aboriginal
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cultural deposits and indicate that other cultural sites, such as scarred trees, may be also located within certain contexts of the assessment area.
The primary recommendation for the Aboriginal component of this desktop assessment is to proceed with a Aboriginal Cultural Heritage Assessment Report.
The sole non-Aboriginal site that was identified (the Arsenic Mine downstream of the Upper Mole River Dam) should be avoided where possible. If it is deemed necessary for the Arsenic mine to be disturbed as a result of development, the site should be thoroughly photographed and recorded and the land be sufficiently rehabilitated before development may proceed.
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PART III: Economic viability
Purpose of section · This section of the feasibility study explores the economic viability of the three options considered relative to the do nothing option (base case)
Summary of findings · Three project options were developed for further consideration. These dams were all located on the same site (Upper Mole River), but were of varying capacity (Option 1: 100 GL, Option 2: 200 GL and Option 3: 300GL) · The three options were compared within a feasibility study which considered their hydrological performance, environmental impact, and engineering design · An economic appraisal was undertaken using a cost benefit analysis (CBA) framework to assess and compare the economic viability of the three Mole River Dam options relative to the base case (status quo). · Based on the costs and benefits and the assumptions captured in the analysis, and a discount rate of 7.0%, none of the options are economically viable.. · The results are very sensitive to the assumed discount rate. The discount rate needs to be lower than 3.0%, for the options to become economically viable. · For any of the options to be economically viable there is a need for greater land-use change from improved water reliability and security. Therefore, further consultation with irrigators to better understand likely land- use changes from improved water reliability and security is a priority.
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6. Economic viability
6.1 Economic Assessment - Cost Benefit Analysis (CBA)
6.1.1 Approach The economic viability of the three shortlisted options was assessed using a cost benefit analysis (CBA) framework, consistent with NSW Treasury requirements (NSW Treasury, 2017). Under this framework, a project is deemed to be economically viable when the value of incremental benefits from the proposed project exceed the value of the incremental costs. Therefore, projects that are economically viable have:
· A net present value (NPV) greater than zero: where the NPV is equal to the present value (PV) of the benefits less the PV of the costs. · A benefit-cost ratio (BCR) greater than one: where the BCR is the PV of the quantified incremental economic benefits (financial, social and environmental) divided by the present value of the quantified incremental costs (e.g. project capital and operating expenditure, plus other investments required to realise those benefits). The key steps in the applied methodology are summarised in Table 6.1 below.
Table 6.1 : Steps to be completed in a CBA · Define the ‘without project scenario’ which defines what the outcomes Establish base case would be if the case for change was not addressed.
Identify / quantify the costs · Quantify incremental economic, financial, social and environmental costs and benefits of the project and benefits of the project relative to the base case in monetary terms.
· Discount the costs and benefits to enable comparison of costs and benefits accruing over different time periods. Discounting costs and benefits · A discount rate of 7 per cent was applied (WaterNSW’s Weighted Average Cost of Capital); with sensitivity tests conducted for 7% and 10% (these are real discount rates, consistent with NSW Treasury requirements).
Quantitative economic · Determine the NPV and BCR of the project relative to the base case. appraisal results · A project should generally be pursued if the NPV is greater than zero.
· Test the sensitivity of results to changes in key assumptions underpinning Sensitivity analysis the NPV and BCR.
· Where costs or benefits could not be assessed quantitatively as part of the Qualitative assessment NPV or BCR, they are considered qualitatively.
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6.1.2 Quantified costs and benefits
Costs and benefits linked to the three options, which have been quantified relative to the base case, include: Costs 1) Capital costs (also referred to as capital expenditure or capex) –Project approvals, design and construction (i.e. project implementation) costs 2) Operation and maintenance costs (also referred to as operating expenditure or opex) – Recurrent costs associated with dam operation and asset maintenance and renewal over the assessment period (50 years – consistent with Treasury guidance)) 3) On-farm capital investment costs – Additional on-farm capital investment that would be required to take advantage of the improved supply of water. For example, this can include land-clearing, land-levelling, investment in irrigation and other equipment needed to expand existing land use (e.g. to grow more cotton) or to change enterprise to a higher value crop (e.g. switch from cotton to nuts)7. Benefits 1) Improved on-farm productivity from converting to higher value land use (assumed to be almonds). Based on preliminary discussions between WaterNSW and irrigators, we understand that improved water security (fewer years with zero water allocations) is needed to provide the certainty for farmers and banks to invest in higher value land use comprised of ‘permanent’ tree crops. As such, a key benefit from the proposed dam options is the conversion of a portion of existing irrigated land use (predominantly cotton) to higher value production (e.g. tree crops). The benefits captured in the CBA assume a portion of land use is changed to almond production, as this is considered to be a reasonable proxy for higher value crops given NSW DPI’s assessment of the real potential in this area for almonds to be grown (as discussed in Appendix B). The area of land use change will likely vary from our forecast and the selection of crops will likely be more diverse. However, given the available information we have developed scenarios for a change of enterprise from cotton to almonds. Benefit 1 captured in the CBA is the improved farm net revenue (gross margin8) resulting from the assumed land use change to almonds. 2) Improved on-farm productivity of existing cotton production. Improved average annual reliability of existing general security allocations means that irrigators will have more water on an annual basis to plant, grow and harvest more crops. The majority of existing irrigated land use is cotton. This leads to a local familiarity with cotton growing and the support services and infrastructure available in the region. Therefore, we assume any increase in water availability that is not assigned to a change in land use (i.e. for almond growing) will be allocated to cotton. Benefit 2 captured in the CBA is the improved farm net revenue (gross margin) for incremental changes to cotton grown in the region. 3) Improved amenity and recreation. The construction of a new dam offers new recreation and amenity opportunities in the area for local residents and visitors. Access to the new dam site may include camping, water sports, and birdwatching and BBQ facilities. These benefits, in this proposed location, are new to the area and will be captured in the CBA in monetary terms by estimating the projected visitor numbers and their willingness to pay for the relevant recreation and amenity benefits, times an estimate of visitor numbers.
6.1.3 CBA assumptions
This section provides a summary of key assumptions underpinning the CBA.
6.1.3.1 General assumptions
Table 6.2 provides a summary of the general assumptions relevant to the CBA.
7 These costs only include one-of capital investment, with any change in operational costs captured separately as part of the net revenue benefits (i.e. gross margin calculation) 8 Gross margin refers to the total income derived from an enterprise less the variable costs incurred in the enterprise.
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Table 6.2 : General CBA assumptions
Assumption Description
Assessment period 50 years · The asset life of a dam is more than 50 years, but as outlined in NSW Treasury Guide to CBA, the longer a project period, the more difficult it becomes to forecast costs and benefits, and the less sensitive the quantum of costs and benefits become in later years · As capex occurs in early years and benefits over the life of the project, 50 years could marginally (but not likely materially) understate the benefits. To address this we have included a residual value (see below) as our proxy for the discounted stream of net benefits for the remainder of the dam’s useful life (to 200 years).
Base year 2017/18 · All costs are in 2017/18 real dollars (i.e. today’s dollars). The model start year is 2017/18.
Expenditure 2018/19 commencement year · It is assumed that year one of expenditure is 2018/19 (i.e. Year two of the model) following the necessary funding approvals. A delay in funding approval will push out the costs but also the timing of the benefits, with no net impact on the CBA results.
Discount rate 7.0 % real discount rate (also tested for 3% and 10% real discount rates in the sensitivity test) consistent with the NSW Guide to CBA. · In a CBA, the real discount rate reflects the long term social opportunity cost of capital (i.e. for society collectively, including public and private sectors). · The Independent Pricing and Regulatory Authority (IPART) uses current market data and long-term averages to estimate the Weighted Average Cost of Capital (WACC) for a ‘benchmark’ regulated business such as WaterNSW. · A WACC of 3.1% is the discount rate applied for WaterNSW projects. This is also consistent with the current low cost of borrowing.
Dam useful life 100 years This is based on a review of asset lives for State Water’s 2014 price proposal (Deloitte Access Economics, 2013).
Escalation · The CBA is provided in real dollars (2017/18 dollars) and therefore costs do not include the cost of inflation from Year 1 onwards (i.e. only input cost may have been inflated to 2017-18). · We assume that all costs are escalated at 2.5%, the midpoint of the Reserve Bank of Australia’s (RBA) target range for the Consumer Price Index (CPI) of 2% to 3%. 2.5% escalation is only applied to bring costs into 2017/18 dollars.
Residual Value Included in Year 50 · Consistent with NSW Treasury Guidelines, the residual value is taken as the lesser of the replacement cost and the present value of future benefits. · Given the useful life of the dam is 100 years and the assessment period is only for 50 years, the present value of future benefits is equivalent to the net residual values for ongoing costs and benefits in the CBA, effectively making it equivalent to a 106 year CBA (100 years post commissioning). · The replacement value is taken as the capital cost of the dam in year 50. · The lower residual value is the replacement value and this has been applied in the analysis · The residual values are included as a benefit (not a cost).
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6.1.3.2 Dam establishment and operation costs
The costs associated with each of the three options being considered have been developed as part of the feasibility assessment. Table 6.3 provides a summary of the costs applied to each of the options. The more detailed cost plans are provided in Appendix I and discussed in Section 4.5.
Table 6.3 : Dam cost assumptions
Assumption Option 1: 100 GL Option 2: 200 GL Option 3: 300 GL
Capital cost assumptions
Capital cost estimate $345 million $388 million $448 million
Delivery phasing Distribution of costs across Years 2 to 6: · Yr 2: 7.5% (detailed feasibility, field work, engineering design and planning approvals) · Yr 3: 10% (detailed design and bid preparation) · Yr 4: 25% (Year 1 of construction) · Yr 5: 30% (Year 2 of construction) · Yr 6: 27.5% (Year 3 / final year of construction and commissioning).
Operation and maintenance cost assumptions
O&M cost $575,000 per annum comprised of9: · 3 FTE staff at $120,000 salary package = $360,000 per annum · Consumables / materials = $100,000 per annum · Project work requirements of 0.5 FTE staff at $230,000 salary package = $115,000 per annum
O&M commencement year Year following dam completion Year following dam completion Year following dam completion (year 6 of model) (year 6 of model) (year 6 of model)
6.1.3.3 Distribution of costs and benefits
We use the NSW portion of the Border Rivers region as the reference region for the CBA. It is the aggregate costs and benefits that are important, irrespective of whether the improved water reliability and security is shared by Queensland and NSW water users, or allocated exclusively to one state.
For the purpose of the assessment, it is the total increase in average annual water usage that is used as the key input from the water modelling undertaken by WaterNSW. This is based on the assumption that a ML of water used in NSW will offer the same economic value as a ML of water used in Queensland.
As the location of the benefits will not impact the results of the CBA, and given the paucity of information available from Queensland (and the relatively higher availability of NSW data) at this time, the CBA has focussed on the benefits being realised in NSW.
Given the instructional arrangement in the Border Rives, it is likely that the Mole River Dam will be a shared resource, and that the benefits will be split between Queensland and NSW equally. The distribution of the costs and benefits will be considered in more detail as part of future business case updates required under the NSW Gateway assurance framework, and will be informed by the planned “willingness to pay” consultation with land owners.
6.1.3.4 Dam filling rates and impact on costs and benefits
The time required to fill each dam option has been estimated assuming that zero water is allocated until the first filling and that the benefits associated with improved reliability and security of supply are only realised once the dam is full. This assumption has been made for modelling purposes only. It is more likely that some water will be allocated during the filling period and that the time to reach maximum improvement in reliability of supply will
9 This compares well with the annual operation and maintenance cost of Copeton Dam a 1.4 km long and 113 m high rockfill dam owned and operated by WaterNSW (pers comm Castro and Budahazy 4 August 2017)
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be longer. The impact on total volume of water allocated over the assessment period and the associated impact on productivity is expected to be negligible.
Table 6.4 provides a summary of the dam filling assumptions, including the first year when water is allocated (taking into account the assumed construction period detailed above).
Table 6.4 : Dam filling assumptions
Dam Option Time to fill First year of water allocations
Option 1 : 100 GL 1 year, 3 months 2024-25 (Year 8 of model)
Option 2: 200 GL 2 years, 5 months 2025-26 (Year 9 of model)
Option 3: 300 GL 3 years, 7 months 2026-27 (Year 10 of model)
6.1.3.5 On-farm costs and benefits from improved reliability of supply for current crops
We estimate on-farm benefits based on the increase in water use that would be achieved for each of the dam options. Based on the water modelling undertaken by WaterNSW, each option will result in an increase in average annual reliability of supply to General Security B licence holders.
The WaterNSW model estimates the allocation and demand for general Security B licences for the base case and the three options. Given that the CBA is interested in the amount of water used on-farm, the demand output has been adopted to estimate annual water usage within Border Rivers. The model also provides allocation estimates, but this does not account for carryovers in the same way as demand.
Figure 6.1 below provides the demand projections for the base case and the three options considered. These are presented as demand against the annual exceedance probability (in the same way as the simulated reliability curves in Section 3.2). The area under each curve is taken as the average annual demand (usage).
While the three options offer a slightly different reliability of supply, the preliminary modelling indicates similar security of supply which was identified by landholders as the key constraint to changing land use to higher value irrigation. ‘Security’ refers to the number of years with zero supply (or the absence of those years). See 100% annual exceedance probability (right-hand end of the curves).
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Figure 6.1 : Modelled demand for base case and three options
Table 6.5 provides the average annual demand modelled for each option. This is a key assumption used in the CBA to estimate the improvement in on-farm productivity resulting from a Mole River Dam.
Table 6.5 : Assumptions for average annual water usage for each option
Option Average annual usage Incremental usage relative (demand) (GL/annum ) to base case (GL/annum )
Base case 102.3 NA
Option 1; 100 GL 130.4 28.1
Option 2: 200 GL 139.7 37.5
Option 3: 300 GL 143.6 41.4
Further detail on the WaterNSW model is provided in Section 3. It is important to note these results are based on high-level modelling. Limitations that should be considered further as part of future business case updates required under the NSW Gateway assurance framework include: · The modelling results do not take into account the influence of on-farm dams and their water losses. · The modelling does not consider the impact on supplementary (unregulated) water in sufficient detail. It is recognised that the reliability and allocation of unregulated water (supplementary water in NSW) may be impacted by the existence of the new dam. Early indications are that the impact on the overall volume of supplementary water supplied may be small relative to the expected improvement in supply of General Security B water.
As part of the subsequent more detailed business case CBA, we will seek to include an additional estimate of costs (or forgone benefits) associated with a potential decrease in supplementary (unregulated) water.” At this stage there is simply not enough data to make an estimate of associated forgone agricultural production, so our benefits may be marginally overstated in this regard.
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6.1.3.6 On-farm costs and benefits - two key benefits
The benefits associated with improved water supply are estimated based on the incremental improvement in gross margin relative to the base case.
Gross margin only captures income less variable costs (i.e. operational costs including direct on-farm labour). Therefore, one-off capital investments that farmers will need to make in order to expand their cotton growing activities are captured as a separate cost. This includes any additional infrastructure that may be applicable to extend the area of cotton cropping (such as overhead irrigation).
The on-farm benefits, of improved water availability to existing general security allocation holders, are assumed to be two key increases in the value of agricultural production: (i) increased cotton production; and (ii) land use change to higher value agriculture (e.g. almonds - discussed in more detail further below).
6.1.3.7 On-farm costs and benefits - increased cotton production
Any increase in water used that is not assigned to a change in land use (almonds) will be used by farmers to improve productivity of existing agricultural activities (cotton). The majority of existing irrigated land use is cotton, which leads to a bias in favour of cotton growing. The support services and infrastructure available in the region have also predominantly been established to support cotton production and processing.
Therefore, we assume any increase in water availability that is not assigned to a change in land use will be allocated to improving the efficiency of cotton. This includes using more land or intensifying production on existing land, whichever delivers the highest net benefit to the landowner. For the purposes of modelling, we have calculated the benefits based on 30% using more land for cotton growing with the additional cost of overhead irrigation (see assumptions in Table 6.6 below) and 70% applied to more land assuming zero additional cost for flood irrigation. The latter is effectively a proxy for applying more water to existing areas planted to cotton (not more land); as we assume no incremental irrigation equipment cost is incurred to obtain increased yields.
We note that with flood irrigation, increased rates of water application per existing hectare of cotton may deliver more profitable increases in cotton production due to less additional costs required. As such, our estimate of on- farm costs required to realise this benefits may be overstated. We have taken this relatively conservative (i.e. higher cost) assumption to mitigate some of the other limitations noted above where our approach may have overstated the benefits (e.g. not accounting for foregone production due to reduced availability of unregulated water).
Other assumptions relevant to on-farm costs and benefits associated with improved reliability of supply are outlined in the Table 6.6.
Table 6.6 : Assumptions for on farm costs and benefits related to improved reliability of supply
Assumptions Description Rationale / information source
Gross margin – cotton $286/ per ML Based on a comprehensive irrigation profile undertaken for the Border Rivers in 2003, cotton was estimated to require 7.5-9 ML/ha. 9 ML/ ha was the estimate for cotton grown in the flood plains and is consistent with the most estimate applied by NSW DPI for Furrow irrigated cotton as part of their gross margin calculations (9.79ML/ha). Given that furrow irrigated cotton is the most common in Border Rivers, we have used 9 ML/ha as the requirement for cotton grown on the flood plains (which is the majority of cotton in the Border Rivers). The gross margin for cotton was estimated at approximately $2,575/ha (escalated to 2017/18 dollars) based on NSW DPI gross margin data Assuming application rates of 9 ML/ha per hectare, this results in our assumed a gross margin of $286/ per ML.
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Assumptions Description Rationale / information source
Establishment costs to expand Weighted average $1,125 On the floodplains of the Border Rivers (NSW) catchment, most broad- cotton growing per /ha acre crops (e.g. cotton, cereals, legumes, and oilseeds) are supplied with water in furrows (i.e. flood irrigation). Cotton irrigated using drip tape has been trialled and on undulating country, cotton is also irrigated using centre pivots (NSW Agriculture. (2003) - however, the uptake is limited. For water supplied using flood irrigation, there is no additional up-front investment for expanding production. However, if expansion is with overhead spray (lateral move and centre-pivot), there will be additional equipment cost of approximately $3,750/ha per hectare. In Queensland, it is estimated that water use in cotton production has improved, with approximately 14% of MDB cotton irrigation relying on centre pivots10. To account for potential increased reliance on water efficient methods, the CBA assumes that 30% (twice that in Queensland) of all expansion of growing cotton relies on centre pivots. Applying 30% to $3,750 and 70% to zero additional cost (flood irrigation) results in a weighted average cost of $1,125/ha per hectare. This is a conservative assumption that ensures that on-farm costs associated with a shift to more water efficient irrigation practices are adequately captured (or potentially overstated) in the analysis. The appropriateness of this assumption would need to be refined as part of more detailed stakeholder consultation and business case.
6.1.3.8 On-farm costs and benefits - high value land use (e.g. almonds)
Improved security of supply (i.e. reducing the number of years with zero General Security B allocations) is expected to induce change in land use to higher value production. The majority of irrigated land use is currently cotton. It is assumed that higher value use can be represented by irrigated almonds as this is a growing market and DPI NSW has identified Border Rivers as a region with suitable soil and climate conditions to take advantage of this (Refer to Section 3.2.2.1).
It is important to note that almond crops are used as a proxy for higher value land use for the purpose of the CBA and that the nature of land use change will depend on more detailed agricultural analysis and stakeholder consultation. Further analysis will also consider the possibility of land used for dryland cropping shifting to high value crops. Our experience nationally is that new irrigation schemes are often designed for a purpose (e.g. historically for tobacco and grains) and end-up growing a wide range of unexpected crops (e.g. high-value fruit and nut trees and cotton). So taking a high-value proxy approach is reasonable.
The percentage change in land use is not known with certainty and can be only be based on high-level assumptions from preliminary discussions with irrigators and a desktop analysis of land use in two areas with better water security and uptake of almond productions - Murrumbidgee in NSW and Sunraysia (in the Mallee region) in Victoria.
As discussed in in more detail in Appendix B, approximately 25% of land use within Murrumbidgee Irrigation Area is allocated to higher value crops such as citrus, vines and other fruit, as well as vegetables. Within the Victorian Murray-Mallee, there has been significant change in crop types over the years, with growth in nut tree plantings (99% almonds) increasing by 18,980 ha (986%), from 1,925 ha in 1997 to 20,905 ha in 2015 (Mallee CMA, 2015).
10 This is from the Guide to the proposed Basin Plan Technical background
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A summary of the land use change within the Victorian Murray-Mallee is provided in Figure 6.2. From this land use summary it is evident that the area of nut trees (almonds) has increased from 5% of total crops in 1997 to 29% in 2015. Therefore over 18 years, an additional 24% of land has been assigned to almond trees.
While the Mallee is not a like-for-like comparison with Border Rivers, its recent experience in land use change is considered to be a reasonable indicative estimate of the maximum land use change that could potentially be achievable over a 20 to 25 year period. The appropriateness of using the Mallee as an upper limit bound for land use change would need to be considered further as part of a detailed business case. In both these ‘benchmark’ areas we note that high-value crops reached or increased by about 25% in the long-term. We have, therefore adopted this as our high benefit scenario. Table 6.7 summarises the land use change assumptions that have been adopted in the CBA.
Figure 6.2 : Trend in crop types from 1997 to 2017 in Victorian Murray-Mallee (Mallee CMA, 2015)
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Table 6.7 : Land use change assumptions (cotton to higher value cropping)
Assumption Description Rationale / information source
Land use change from cotton to · 1% per annum of existing · In the Mallee, the area of nut trees (almonds) has increased by higher value use (almonds used irrigated cotton land, is 24% over 18 years. With less horticulture in the Border Rivers as a proxy) converted to almond than in the Mallee, it is assumed that uptake of drip irrigation will irrigation, land for 10 years. take longer. · After 10 years of planting, · As such, we assume that the land use change will be 1% per 10% of existing land used for annum for 10 years (a 10% change in total). cotton crops will be · Our upper limit (high benefit) scenario is 1% per annum for 25 producing almond crops. years up to 25% tested as a sensitivity analysis. · Our lower limit (low benefit) scenario is 1% per annum for 5 years up to 5% also tested as a sensitivity analysis. · We assume that all three dam size options will result in similar land use change, as the water security benefits are similar (approximately 1.9% of years incur zero allocations - at the right- hand end of the supply curves presented further above). · These assumptions will need to be assessed in further detail during consultation with landowners when developing a full business case CBA.
Gross Margin - almonds · $1,024/ ML · According to DPI NSW data, almonds require a minimum of 8.5- · $12,801/ ha 10 ML/ha throughout the growing season (October to April). · More than 14 ML/ ha could be required in some regions. · We have assumed 12.5 ML/ha (the middle of this range). · The gross margin for almonds is estimated at $10,000/ha ($2007/08) based on industry data (Rural Solutions, 2006). · We have escalated this value to $2017/18 using a 2.5% escalation rate to $12,801/ ha. This results in an assumed GM of $1,024/ ML.
Establishment costs for land use · $18,104/ ha · These costs are in addition to those captured within gross change (cotton to almonds) margin and include both land establishment costs and machinery costs. · Establishment costs range ($10,000/ha - $15,000/ha) was provided by DEJTR – Agriculture Victoria (DEJTR, 2017) and is assumed to be a reasonable range for Border Rivers. · The average of $12,500/ha ($2002/03) is assumed for modelling purposes. We have escalated this value to $2017/18 using a 2.5% escalation rate, resulting in $18,104/ha.
Machinery costs · $1,224 / ha per year · US Study (University of California’s Agricultural Issues Centre, 2016) has sample costs for almond orchard production that estimates machinery costs at approximately $35,000 per annum for a property that is 100 acre (approximately 40 ha). This has been used as a conservative estimate, which translates to approximately $1,224/ha per year, using an escalation rate of 2.5% and a $AU to $US exchange rate of 0.74.
Almond trees establishment and · Years to first return: 3 · These assumptions are based on a report on the economics of yield · Yield in 3 years: 0.25 t/ha almond production in southern Australia (Rural Solutions, 2006) · Years to mature return: 6 · Mature yield: 2.45 t/ha
Water use during almond trees · Increasing from 25% of full · Fully established almond trees require approximately 12.5 establishment period water requirements to 100% ML/ha of water. over first four years of plan · However, in the first few years of establishment, water
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Assumption Description Rationale / information source
establishment requirements will be lower. It is assumed that this increases linearly from 3.5% (approximately 3 ML/ha) to 100% (12.5 ML/ha) over four years.
Commencement of planting of · 3 years after filling of the · Based on preliminary discussions between WaterNSW and higher value crop dam irrigators, it is understood that irrigators may wish to see evidence of improved security of supply over several years before investing in land use change. · It is therefore assumed that planting would commence three years after the new dam is filled and the impact on water determinations has been witnessed. · This is conservative as it may understate the benefits (by deferring investment). It is recognised that planting may commence earlier once dam construction is nearing completion. · These assumptions are tested in the sensitivity analysis.
6.1.3.9 Recreation and amenity benefits
The estimated total annual value of recreation and amenity benefits from the proposed Mole River Dam are between $0.8 million (Option 1) and $1.6 million per annum (Option 3). This is based on willingness to pay estimate (per person) times forecast visitor numbers. This is a relatively marginal benefit.
Access to the new dam will result in a number of recreation and amenity values for local residents and visitors to the area. The monetary value of amenity and recreation at the proposed Mole River Dam has been calculated based on an estimate of: · Potential visitation to the Mole River Dam: Visitor numbers were estimated based on the experience of nearby dams. Care was taken to only capture new (i.e. induced) visitors to the area, and to exclude visitors that would visit Mole River Dam instead of other nearby attractions (i.e. substitution demand). · Visitors’ willingness to pay (WTP) for the associated benefits: This has been estimated using a benefit transfer approach which ‘transfers’ WTP values from more detailed studies (i.e. surveys) at other sites that have similar or transferable characterises to the proposed Mole River Dam site. Benefit transfer is the most common valuation approach due to the high costs associated with undertaking site-specific surveys. The accuracy of benefit transfer depends on the degree of similarity between the study and the project area and the accuracy of the initial study.
Glenlyon Dam is considered the most appropriate dam for the purposes of estimating visitor numbers and potential willingness to pay for amenity and recreation benefits at the proposed Mole River Dam site. Glenlyon dam on Pike Creek is geographically the closest dam to the proposed Mole River Dam, at about 50km distance or less than an hour’s drive by car. The site of the proposed Mole River Dam is in northern NSW close to the border with Queensland. While Glenlyon Dam is near to border on the Queensland side, both dams would be in the Border Rivers irrigation catchment.
Amenity and recreation benefits were estimated based on two key values: · Value of recreational fishing. From available studies it appears that fishing attracts the highest willingness to pay relative to other recreation activities, and therefore it is considered worthwhile valuing it as a standalone benefit. The WTP for fishing was based on a study that assessed the WTP for recreational fishing and annual visitation rates for 31 different dams in Queensland, including Glenlyon Dam (Gregg and Rolfe, 2013). The study used the cost of travel incurred by individuals visiting a dam as a proxy for WTP11. Adjustments to the visitation numbers were made to reflect expected differences between the Glenlyon
11 This is referred to as the travel cost method and is the major valuation technique used to estimate WTP values for recreation
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dam and the proposed Mole River Dam site and to ensure that only the incremental benefits of the new dam are captured12. · Value other recreational use and amenity. Other recreation and amenity benefits such as the value placed on improved access to walking tracks, picnic areas, swimming and potential camping grounds were grouped together. These values were based on studies that considered WTP for visits to state and national parks in Victoria and NSW.
Using the recreational fishing values for Glenlyon Dam in the Gregg and Rolfe (2013) study and the recreation and amenity values from state and national parks in other studies, are an appropriate methodology to value recreation and amenity benefits for Mole River Dam based on the key criteria for benefit transfer (refer to text box below).
Demonstrated compliance with benefits transfer criteria
The following demonstrates the compliance of the adopted method with key criteria for benefit transfer: · The primary study should be statistically sound, with a sufficient sample size, and other design aspects which support the production of valid and reliable results – the recreational fishing study has similar results to other Australian studies of recreational fishing and several studies on state and national parks were considered for the other recreation and amenity benefits · The characteristics of the two non-market goods and services (e.g. the original and new application) should be highly similar - some factors that determine comparability are similar types of sites (e.g., dams that provide recreational fishing), similar quality of sites (e.g., size, water quality and facilities), and similar availability of substitutes (e.g., the number of other dams nearby) – the Mole River dam will provide recreational fishing, wildlife viewing, water skiing, sailing, canoeing, swimming, cycling, bushwalking, picnics and barbeques like the Glenlyon Dam and state and national parks in Victoria and NSW; the Mole River dam can be expected to provide similar tourist facilities such as camp sites and holiday parks over time to the Glenlyon Dam and state and national parks in Victoria · The characteristics of the population of the original study (including factors such as disposable income, age, education levels etc.) should be comparable to the new application – both the Glenlyon Dam and the proposed Mole River Dam are in the Border Rivers irrigation catchment and have similar socio-economic characteristics; the studies for state and national parks were for NSW and Victoria · The primary study should be as recent as possible (e.g. ideally within 10 years) – the recreational fishing study was produced in 2013; the studies for state and national parks were generally older, although a study for Victorian parks was produced in 2015.
Costs associated with the proposed Mole River Dam do not include additional costs to provide the facilities for some of the recreation uses (e.g. camping sites, walking trails). However, it is assumed that these facilities (most of which are marginal costs) will be delivered as part of the overall capital cost of the dam or overtime.
Key assumptions relevant to the recreation and amenity benefits are summarised in Table 6.8.
Table 6.8 : Assumptions for recreation and amenity benefits
Assumptions Description Rationale / information source
Relative size of dams · Option 1: 7.7 km2 (~43% of Glenlyon Dam) · Selected recreation and amenity benefits are scaled (square kilometres) · Option 2:11.8 km2 (~66% of Glenlyon Dam) based on dam surface area, which varies by option. · Option 3: 146 km2 (~81% of Glenlyon Dam) · Selected values are based on comparison to Glenlyon Dam, and therefore the surface area of each option was also compared to the surface area of Glenlyon Dam.
12 Some visitors to Glenlyon will now visit Mole River Dam instead because it is more convenient. These substitution impacts need to be excluded from the study.
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Assumptions Description Rationale / information source
Willingness to pay per day · $215/ day (2017/18 dollars) · The average of the two WTP estimates for for recreational fishing at recreational fishing at the Glenlyon Dam was $200 in Mole River Dam 2013 and has been escalated to 2017/18 dollars.
Willingness to pay per visit · $47/ visit (2017/18 dollars) This is the average of several studies: for other recreation · Dorrigo National Park (Bennett, 199513) - $34 per activities and amenity at visit ($58 in 2017/18 dollars). Mole River Dam · Minnamurra Rainforest Centre, Budderoo National Park (Gillespie, 199714) - $28 to $48 per visit ($63 average per visit in 2017/18 dollars). · Grampians National Park (Read, Sturgess and Associates, 199415) $33 per visit ($59 in 2017/18 dollars). · Valuing Victoria’s Parks (Parks Victoria, 2015) – inferred $20 per visit ($21 in 2017/18 dollars) · Gibraltar Range National Park (Bennett, 199516) - $19 per visit ($32 in 2017/18 dollars)
Total new visitors per year · Option 1: 6,410 total visitors/ annum · According to a 2015-16 Annual Report from the · Option 2: 9,850 total visitors/ annum BRC, there were 30,000 visitors to Glenlyon Dam in 2015-16 (assumed that this included repeat visitors). · Option 3: 12,190 total visitors/annum · It is expected that the largest of the three Mole Rover Dam options (Option 3) will attract similar visitor numbers per annum. · It is recognised that some of these visitors would be diverted from Glenlyon Dam and some would not have otherwise visited Glenlyon Dam. To ensure that only the incremental benefits are captured, it is assumed that new (i.e. induced visitors) make up 50% of total visitors. · Visitor numbers for Option 2 and Option 1 were scaled based on the relative size. The relative size of the dams is an indicator of the relative quality of the recreational and amenity benefits of the dams.
Number of new (induced) · Option 1: 2,570 visitor days/annum The number of days per annum to Mole River Dam that visitor days assigned to · Option 2: 3,940 total visits/annum visitors assign to recreational fishing has been estimated fishing benefits · Option 3: 4880 per year/annum based on the following assumptions: · 8% of visitors to Mole River Dam would be recreational fishing visitors · Each of these visitors would spend an average of five 5 days per visit These assumptions were benchmarked against Glenlyon Dam (Gregg and Rolfe, 2013). These assumptions are consistent with other studies which show that most use of dams is passive use (e.g. picnics and camping).
Number of new (induced) · Option 1: ~5,900 total visits/annum · It is assumed that 92% of new (induced) visitors to visits for other recreation · Option 2: ~9,060 total visits/annum Mole River Dam would be visiting for other use and amenity benefits recreational and amenity purposes including · Option 3: 11,220 per year/annum swimming, bushwalking and camping.
13 As cited in Gillespie Economics, 1997 14 As cited in Gillespie Economics, 1997 15 As cited in Gillespie Economics, 1997 16 As cited in Gillespie Economics, 1997
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Assumptions Description Rationale / information source
· This is based on the remaining share of visitors after recreational fishing visitors are estimated and is consistent with studies that show that most use of dams is passive.
Benefit realisation during · Option 1: 100% by year 7 · The value of recreation and amenity benefits were dam filling phase · Option 2: 100% by year 8 scaled during the dam filling phase. The fill of the · Option 3: 100% by year 9 dams is an indicator of the quality of the recreational and amenity benefits of the dams.
The benefits calculated were compared against a study done by Rolfe and Dyack (2010) who calculated the recreation and amenity in the Coorong, South Australia. The Coorong is a long, shallow saline lagoon that stretches more than 100 km. The Coorong National Park provides similar activities to the proposed dam such as bird watching, boating, kayaking, fishing, camping, and walking. The National Park is significantly bigger site at about 490 square kilometres, however.
The study found the average value of the recreation benefits per person per day was $152.80 (average of the travel cost and contingent valuation findings). Applying this benefit per person to the number of estimated visitor days at the proposed Mole River dam, results in a total value of $5.1 million per annum. This suggests that the WTP values used in the analysis are relatively conservative. In contrast, the assumed value of recreation and amenity benefits from the proposed Mole River Dam are between $0.8 million (Option 1) and $1.6 million per annum (Option 3) in this CBA.
6.1.3.10 Residual dam value
As the economic life of the dam is approximately 100 years, and the economic model is only 50 years, the residual value of the dam is captured in Year 50 of the assessment. As outlined in Table 6.2, the residual value is taken as the lesser of the discounted value of the net benefits that would be expected from Year 51 to 106 (100 years post dam commissioning) and the replacement value of the dam. For all three options, the lower value is the net benefits from Year 51 to 106. This approach is consistent with the NSW Treasury guidance.
The assumed values in this CBA are summarised in Table 6.9 below.
Table 6.9 : Residual value of the dam (7% real discount rate)
Net benefits from year 51 Replacement value Applied residual value end of dam life (present (present value) (present value) value)
Option 1: 100 GL $12.54 m $8.12 m $8.12 m
Option 2: 200 GL $14.11 m $9.71 m $9.71 m
Option 3: 300 GL $16.29 m $10.43 m $10.43 m
6.1.4 CBA Results
Key CBA results for Options 1, 2 and 3 are shown in Table 6.10. The results present the incremental changes in costs and benefits against the base case using a discount rate of 7.0%.
The CBA results are as presented in Table 6.10.
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Table 6.10 : CBA results, present value ($Million, 7% real discount rate)
Option 1 Option 2 Option 3
Capital costs $ 271.40 m $ 305.46 m $ 352.59 m
Operation and maintenance costs $ 5.56 m $ 5.56 m $ 5.56 m
On-farm costs (land use change) $ 13.57 m $ 13.28 m $ 12.60 m
Total costs (PV) $ 290.53 m $ 324.30 m $ 370.75 m
On-farm benefits from higher value land use (almond growing) $ 49.54 m $ 45.88 m $ 42.46 m
On-farm benefits from expanded cotton growing $ 54.56 m $ 71.88 m $ 74.37 m
Recreation and amenity benefits $ 7.90 m $ 11.67 m $ 13.89 m
Residual dam value (net of ongoing O&M) $ 8.12 m $ 9.71 m $ 10.43 m
Total Benefits (PV) $ 120.12 m $ 139.14 m $ 141.15 m
NPV -$ 170.41 m -$ 185.16 m -$ 229.60 m
BCR 0.41 0.43 0.38
IRR 2.78% 3.01% 2.66%
Based on the costs and benefits and the assumptions captured in the analysis, none of the options deliver a positive NPV.
The Internal Rate of Return (IRR) demonstrates how sensitive the results are to the selected discount rate. The IRR is the discount rate that would achieve an NPV of 0 (i.e. the rate at which the discounted benefits equal the discounted costs). A discount rate lower than 2.78%, 3.01% and 2.66% for Options 1, 2 and 3 respectively would result in an economically viable project.
The full CBA results for each option are provided in Appendix A.
The impacts of key assumptions on the CBA results are considered further in the sensitivity analysis below.
6.1.5 Sensitivity testing
A sensitivity analysis is used to test the impact on the BCR and NPV from changes to key assumptions. This is an opportunity to test the impact of assumptions with significant uncertainty. The key variables tested include: 1) Discount rate – this is testing a change in discount rate to 3% and 10% in-line with NSW Treasury requirements 2) Land use change assumptions - including the year in which planting commences, the percentage of land converted from cotton to almond crops over the assessment period the rate of this change. The baseline assumes planting only occurs three years after the dam is filled and that there is 1% change in irrigation area per year for 10 years. The sensitivity test considers the impact of bringing forward planting prior to dam filling or dam completion as well as a: - Zero land use change from cotton to almonds, with all additional water being allocated to more cotton (rather than a transition to almond cropping) - Lower transition to almond cropping of 1% per annum for 5 years - Higher transition to almond cropping - at the maximum based on the Mallee experience of 1% per annum for 25 years 3) Improved water use efficiency of cotton crops – this tests 7.5 ML/ha being required rather than the assumed 9 ML/ha 4) Improved water use efficiency of almond crops – this tests 10 ML/ha required rather than the assumed 12.5 ML/ha
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5) Cotton establishment cost - it has been assumed that 30% of any growth in cotton irrigation will use centre pivots which will involve higher up-front investment. The sensitivity analyses tests the impacts of future growth remaining as flood irrigation, with zero up front establishment costs 6) Reduction in forecast average annual water supplied – The average annual water supplied and used by irrigators has been based on initial water modelling. The sensitivity analysis tests for the impact of reducing the modelled average annual usage (demand) for the three options by 20%. This accounts for the need to undertake more detailed modelling, including more detailed consideration of how reliability of supplementary (unregulated) water is affected. 7) Dam construction costs - given that the cost estimates are high-level assumptions, a 40% increase and 20% decrease in costs has been tested The NPV and BCR results for each sensitivity test are provided in Table 6.11.
Table 6.11 : NPV and BCR sensitivity test results (shaded blue implies NPV>0)
Sensitivity Variable Option 1 Option 2 Option 3 test NPV BCR NPV BCR NPV BCR
- Baseline results -$ 170.41 m 0.41 -$ 185.16 m 0.43 -$ 229.60 m 0.4
1 Discount rate is 3% $ 10.90 m 1.03 $ 29.16 m 1.07 $ 1.14 m 1.0
2 Discount rate is 10% -$ 193.26 m 0.25 -$ 214.47 m 0.26 -$ 257.31 m 0.2
Years following dam filling where -$ 157.24 m 0.47 -$ 172.86 m 0.48 -$ 218.10 m 0.4 3 planting of almonds occurs = -3
Years following dam filling where -$ 164.57 m 0.44 -$ 179.71 m 0.45 -$ 224.50 m 0.4 4 planting of almonds occurs = 0
Zero % land use change, with all -$ 195.96 m 0.30 -$ 209.04 m $0.33 -$ 251.91 m 0.3 5 additional water allocated to increased cotton production
% land use change from cotton to -$ 181.03 m 0.37 -$ 195.10 m 0.39 -$ 238.88 m 0.3 almonds is 1% per annum for 5 6 years (low land use change scenario)
% land use change from cotton to -$ 155.10 m 0.48 -$ 170.98 m 0.48 -$ 214.99 m 0.4 almonds is 1% per annum for 25 7 years (high land use change scenario)
Improved water efficiency of cotton -$ 155.08 m 0.47 -$ 166.49 m 0.49 -$ 210.59 m 0.4 8 crops to 7.5 ML/ha
Improved water efficiency of almond -$ 166.76 m 0.43 -$ 181.76 m 0.44 -$ 226.41 m 0.4 9 crops to 10 ML/ha
20% reduction in forecast average -$ 238.15 m 0.17 -$ 252.28 m 0.22 -$ 293.35 m 0.2 10 annual water usage (demand)
40% increase in dam establishment -$ 278.97 m 0.30 -$ 307.35 m 0.31 -$ 370.63 m 0.3 11 costs
20 % decrease in dam -$ 116.13 m 0.51 -$ 124.07 m 0.53 -$ 159.08 m 0.5 12 establishment costs
As can be seen from the above results, the results are most sensitive to the following key variables: · Discount rates. The results are very sensitive to the discount rate, with a discount rate of 3% the only sensitivity test where the project is economically viable.
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· Land use change. The economic viability declines further if there is less land use change from cotton to higher value crops as a result of improved water security. The base assumption is that planting of almonds only occurs three years after the dam is filled and that there is 1% change in irrigation area per year for 10 years. Even with the high land use change scenario (Test 7) the BCR of each option is still less than 0.5. · Water supply. As would be expected, the results are also very sensitive to the results from the water modelling undertaken. If the average annual usage (demand) is reduced by 20% (Test 10) the economic viability all three options declines significantly. · Cost. A reduction in cost by 20% (Test 12) is not sufficient to make any of the options economically viable.
6.1.6 Additional benefits not captured in the CBA
6.1.6.1 Reduced flood damages
Reduced flood damages will also be realised under any of the options considered. This benefit could not be quantified at this stage due to data limitations but may need to be considered further as part of a more detailed business case.
A preliminary assessment of peak flows from the dam have demonstrated that there will be a reduction in flooding downstream of the dam. This will result in a reduction in flood damages.
The flood damages that can be reduced or avoided include: · Direct (tangible) damages comprise the physical impact of the flood. This will predominantly include damages to agricultural crops, equipment and machinery, fencing and potentially farm buildings and contents · Indirect (tangible) damages comprise losses from disruption of normal economic and social activities that arise as a consequence of the physical impact of the flood. This will include emergency response, clean- up, community support, as well as disruption to economic activities which will predominantly be agricultural production. · Intangibles, or ‘non-market’ impacts, comprise losses which cannot be readily quantified in monetary terms (since market prices cannot be used). For example, loss in biodiversity, psychological impacts, physical injury or increased stress levels for residents following a major flood event affecting their homes or livelihood.
The main flood damage cost that would be reduced or avoided as a result of the proposed Mole River Dam is the associated economic loss incurred when agricultural land is inundated. In particular, flooding may prevent planting; destroy crops in the ground, or prevent harvesting. Economic losses are not contained to one season. Subsequent seasons may require higher production costs to control weed infestations, and crop yields may be lower than they would otherwise have been.
These losses vary depending on the month or season of the flood event, the duration of inundation and the type of drops inundated.
The flood mitigation benefits will vary across the three options being considered. A larger dam and shorter spillway will lead to a greater reduction in downstream flood peaks and therefore an increased flood mitigation benefits (i.e. reduced flood damages relative to the base case).
To determine the extent of the benefits and the relative improvement in these benefits between the options, further analysis is required to estimate current annual flood risk and the residual annual flood risk post dam construction. The analysis should include detailed flood modelling and inundation mapping for a variety of Annual Exceedance Probability (AEP) events. This would involve: · Updating the current hydrology to be suitable for detailed flood mapping
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· Hydraulic modelling of the dam and downstream reaches · Flood mapping of the hydraulic model results · Consideration of the incremental damages from the dam · Consideration of coincident flows for adjacent catchments · BCA of flood modelling results
6.1.6.2 Other potential benefits · Potential environmental health benefits along the Barwon-Darling river system resulting from the continuity of flow · Potential to provide an additional small annual surface water supply between Bourke and Menindee Lakes as a result of capturing large inflows upstream of the proposed dam site, and releasing during times of low flows (i.e. keep the river running and reduce initial losses) · Reduced evaporation losses resulting from large, shallow on-farm storages, thereby increasing net water supplied to the system
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7. Discussion and next steps
Table 7.1 below highlights some of the most important limitations and uncertainties associated with this feasibility study.
Table 7.1 : Summary of uncertainties and limitations
Limitation/Uncertainty Impact on feasibility/ Proposed mitigation Effort required viability
Water Resources modelling
High Moderate A simplified water resources Analysis using a more Demonstration of the need is Develop a more detailed model, providing indicative detailed model would likely based on approximate eWater Source Model results take several months to hydrology complete.
Stakeholder consultation
Moderate Targeted stakeholder consultation to test and Moderate The CBA assumes that security refine assumptions about: Consultation would require of supply drivers land use Uncertainty of water users’ · Likely land use change 2-3 months to fit around change (to higher value response to improved water and the timing and rate farmers’ schedules. This permanent crops), with the security and/or reliability and of such changes could be completed balance of the water used for the trade-offs between the alongside the preparation cotton. · Likely uptake of more two impacts efficient cotton irrigation of a more detailed The CBA results are sensitive systems (i.e. from business case for Gateway to the likely split between land furrow to overhead approval. use change and more intensive irrigation) cotton growing.
Moderate Addition research and consultation will require an Consultation with farmers On-farm gross margins and addition 2-4 weeks. in the region and targeted capital investments for cotton Historical data is probably information gathering with and almond crops is based sufficient for the CBA if all DPI Water (NSW), on historic or desktop data – other limitations are Low representatives of the some of which may be out of adequately addressed. cotton sector (e.g. Cotton date or based on other areas Australia) and practitioners This additional research (with different soil types and in the almond growing and consultation will irrigation practices) industry. become more important if the CBA results are inconclusive once the other limitations are addressed.
Cost benefit analysis
High Determine the most Moderate appropriate discount rate in Appropriate discount rate to Commercial discussions consultation by confirming and negotiations with all base economic viability The project is not economically funding partners. potential funding partners decisions on. viable at a real discount rate of Seek clarification from to reach agreed position – 7%, but is economically viable those partners about likely including WaterNSW,
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Limitation/Uncertainty Impact on feasibility/ Proposed mitigation Effort required viability for discount rates below 3.8- commercial arrangements Sunwater, NSW 4.3%, depending on the (i.e. cost of debt) that would Government, Qld option. be incurred. Government, BRC, and the Commonwealth.
Engineering/cost
Moderate
Moderate Undertake drilling and Significant up-front time Geological field investigations and cost investment. Such Unlikely to impact feasibility, preliminary geological field lacking in detail - no borehole investigations would need but significant impact on investigations to improve exploration to be undertaken in any economic viability cost certainty event if the project proceeds
Moderate Moderate Significant up-front time Reconnaissance for Assumptions made for Undertake detailed field and cost investment. Such construction materials lacking engineering inputs have investigations to improve investigations would need in detail significantly increased cost cost certainty to be undertaken in any uncertainty event if the project proceeds
A dam on the Upper Mole River (three size options of 100 GL, 200 GL and 300 GL) is technically feasible, but the low level of detail of some of the supporting investigations (the geological investigation in particular), introduces significant cost uncertainties.
Several possible environmental, water quality and heritage impacts have been identified at desktop level, and further investigation is needed.
However, none of the options are economically viable at a discount rate of 7%. This is based on the preliminary hydrological assessment and the assumptions used in the CBA.
Based on the IRR, discount rates lower than 3% are necessary for the Mole River Dam to be economically viable (subject to further refinement and testing of some of the assumptions).
For any of the options to be economically viable there is a need for greater land-use change from improved water reliability and security. Therefore, further consultation with irrigators to better understand likely land-use changes from improved water reliability and security is a priority.
Should this project proceed to full business case, it is recommended that a more detailed analysis is undertaken that further investigates: · Dam yields and hydrology: This includes estimating average changes in water availability and demand using a more detailed water resources model. This analysis would address some of the current modelling uncertainties, including: i. Capturing the impact of both general and supplementary water reliability ii. Capturing the impact of on-farm dams on water availability (i.e. capturing the benefits as well associated on-farm water losses) iii. Having more robust assumptions regarding water demand and therefore carryover iv. Providing more accurate projections of security impacts, noting that the inaccuracies resulting from the simplifications in the model are expected to be amplified in drought times (in particular the way demand is estimated).
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· Irrigators’ response to improved reliability and security: This includes undertaking stakeholder consultation with irrigators that tests their willingness to pay for improved water supply reliability. In addition, a detailed demand assessment should be carried out that tests or validates assumptions used on how the availability for more secure and more reliable water would change land use and productivity. As part of this consultation, it would be necessary to test and refine assumptions about: i. Likely land use change and the timing and rate of such changes ii. Likely uptake of more efficient cotton irrigation systems (i.e. from furrow to overhead irrigation) · On-farm gross margins and capital investments for the Border Rivers context: Our analysis uses gross margin information from historical sources as well as machinery costs from a range of interjurisdictional and overseas sources. We have indexed many of the key figures at 2.5% CPI, to bring them to 2017/18 dollars. Further work would require development of more robust estimates, in consultation with farmers in the region, and by accessing more current data from DPI Water (NSW), representatives of the cotton sector (e.g. Cotton Australia) and practitioners in the almond growing industry including in the Murrumbidgee Irrigation Area, NSW and Sunraysia, Murray-Mallee Area, Victoria.
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8. Conclusion
Technical feasibility
The Mole River Dam is considered technically feasible to construct, as: · The dam site is believed to be suitable in terms of the water storage provided · Founding conditions appear to be manageable · While there is much uncertainty surrounding the nature and suitability of construction materials, the impact thereafter will be related to cost · Specialist studies have not identified “show stopper” issues that preclude approvals.
Economic viability
However, none of the options are economically viable at a discount rate of 7%. This is based on the preliminary hydrological assessment and the assumptions used in the CBA.
Based on the IRR, discount rates lower than 3% are necessary for the Mole River Dam to be economically viable (subject to further refinement and testing of some of the assumptions).
For any of the options to be economically viable there is a need for greater land-use change from improved water reliability and security. Therefore, further consultation with irrigators to better understand likely land-use changes from improved water reliability and security is a priority.
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Appendix A. Full cost benefit analysis results
This appendix provides the detailed results of eth cost benefit analysis (CBA) discussed in Section 6. It provides the costs and benefits projected to be incurred every year in the 50 year assessment period, the net benefits, NPV, BCR and IRR. All results are provided for a 7% discount rate (real).
A.1 Option 1 (100GL) CBA result (7% discount rate)
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Project Cost Project benefits On farm On-farm benefits - Year (ending Capital On farm benefits - Amenity and Residual dam Net benefits O&M Total Cost higher Total benefits June 30) costs costs current land recreation value value land use use 2018 ------2019 $ 26 m - - $ 25.9 m ------$ 25.9 m 2020 $ 35 m - - $ 34.5 m ------$ 34.5 m 2021 $ 86 m - - $ 86.3 m ------$ 86.3 m 2022 $ 104 m - - $ 103.5 m ------$ 103.5 m 2023 $ 95 m - - $ 94.9 m ------$ 94.9 m 2024 - $ 0.6 m - $ 0.6 m - - $ 0.7 m - $ 0.7 m $ 0.1 m 2025 - $ 0.6 m $ 3 m $ 3.2 m - $ 6.0 m $ 0.8 m - $ 6.9 m $ 3.6 m 2026 - $ 0.6 m $ 1 m $ 1.5 m - $ 8.0 m $ 0.8 m - $ 8.9 m $ 7.4 m 2027 - $ 0.6 m - $ 0.6 m - $ 8.0 m $ 0.8 m - $ 8.9 m $ 8.3 m 2028 - $ 0.6 m $ 2 m $ 2.3 m - $ 7.9 m $ 0.8 m - $ 8.8 m $ 6.5 m 2029 - $ 0.6 m $ 2 m $ 2.3 m - $ 7.8 m $ 0.8 m - $ 8.6 m $ 6.3 m 2030 - $ 0.6 m $ 2 m $ 2.3 m $ 0.1 m $ 7.5 m $ 0.8 m - $ 8.5 m $ 6.1 m 2031 - $ 0.6 m $ 2 m $ 2.4 m $ 0.6 m $ 7.2 m $ 0.8 m - $ 8.6 m $ 6.2 m 2032 - $ 0.6 m $ 2 m $ 2.5 m $ 1.5 m $ 6.8 m $ 0.8 m - $ 9.1 m $ 6.7 m 2033 - $ 0.6 m $ 2 m $ 2.6 m $ 2.7 m $ 6.5 m $ 0.8 m - $ 10.0 m $ 7.4 m 2034 - $ 0.6 m $ 2 m $ 2.7 m $ 4.0 m $ 6.1 m $ 0.8 m - $ 10.9 m $ 8.2 m 2035 - $ 0.6 m $ 2 m $ 2.8 m $ 5.2 m $ 5.8 m $ 0.8 m - $ 11.8 m $ 9.0 m 2036 - $ 0.6 m $ 2 m $ 2.9 m $ 6.4 m $ 5.4 m $ 0.8 m - $ 12.7 m $ 9.8 m 2037 - $ 0.6 m $ 2 m $ 3.1 m $ 7.7 m $ 5.1 m $ 0.8 m - $ 13.6 m $ 10.5 m 2038 - $ 0.6 m $ 1 m $ 1.4 m $ 8.9 m $ 4.8 m $ 0.8 m - $ 14.6 m $ 13.1 m 2039 - $ 0.6 m $ 1 m $ 1.5 m $ 10.1 m $ 4.7 m $ 0.8 m - $ 15.6 m $ 14.1 m 2040 - $ 0.6 m $ 1 m $ 1.7 m $ 11.3 m $ 4.6 m $ 0.8 m - $ 16.7 m $ 15.0 m 2041 - $ 0.6 m $ 1 m $ 1.7 m $ 12.0 m $ 4.6 m $ 0.8 m - $ 17.4 m $ 15.7 m 2042 - $ 0.6 m $ 1 m $ 1.8 m $ 12.4 m $ 4.6 m $ 0.8 m - $ 17.8 m $ 16.0 m 2043 - $ 0.6 m $ 1 m $ 1.8 m $ 12.4 m $ 4.6 m $ 0.8 m - $ 17.8 m $ 16.0 m 2044 - $ 0.6 m $ 1 m $ 1.8 m $ 12.4 m $ 4.6 m $ 0.8 m - $ 17.8 m $ 16.0 m 2045 - $ 0.6 m $ 1 m $ 1.8 m $ 12.4 m $ 4.6 m $ 0.8 m - $ 17.8 m $ 16.0 m 2046 - $ 0.6 m $ 1 m $ 1.8 m $ 12.4 m $ 4.6 m $ 0.8 m - $ 17.8 m $ 16.0 m 2047 - $ 0.6 m $ 1 m $ 1.8 m $ 12.4 m $ 4.6 m $ 0.8 m - $ 17.8 m $ 16.0 m 2048 - $ 0.6 m $ 1 m $ 1.8 m $ 12.4 m $ 4.6 m $ 0.8 m - $ 17.8 m $ 16.0 m 2049 - $ 0.6 m $ 1 m $ 1.8 m $ 12.4 m $ 4.6 m $ 0.8 m - $ 17.8 m $ 16.0 m 2050 - $ 0.6 m $ 1 m $ 1.8 m $ 12.4 m $ 4.6 m $ 0.8 m - $ 17.8 m $ 16.0 m 2051 - $ 0.6 m $ 1 m $ 1.8 m $ 12.4 m $ 4.6 m $ 0.8 m - $ 17.8 m $ 16.0 m 2052 - $ 0.6 m $ 1 m $ 1.8 m $ 12.4 m $ 4.6 m $ 0.8 m - $ 17.8 m $ 16.0 m 2053 - $ 0.6 m $ 1 m $ 1.8 m $ 12.4 m $ 4.6 m $ 0.8 m - $ 17.8 m $ 16.0 m 2054 - $ 0.6 m $ 1 m $ 1.8 m $ 12.4 m $ 4.6 m $ 0.8 m - $ 17.8 m $ 16.0 m 2055 - $ 0.6 m $ 1 m $ 1.8 m $ 12.4 m $ 4.6 m $ 0.8 m - $ 17.8 m $ 16.0 m 2056 - $ 0.6 m $ 1 m $ 1.8 m $ 12.4 m $ 4.6 m $ 0.8 m - $ 17.8 m $ 16.0 m 2057 - $ 0.6 m $ 1 m $ 1.8 m $ 12.4 m $ 4.6 m $ 0.8 m - $ 17.8 m $ 16.0 m 2058 - $ 0.6 m $ 1 m $ 1.8 m $ 12.4 m $ 4.6 m $ 0.8 m - $ 17.8 m $ 16.0 m 2059 - $ 0.6 m $ 1 m $ 1.8 m $ 12.4 m $ 4.6 m $ 0.8 m - $ 17.8 m $ 16.0 m 2060 - $ 0.6 m $ 1 m $ 1.8 m $ 12.4 m $ 4.6 m $ 0.8 m - $ 17.8 m $ 16.0 m 2061 - $ 0.6 m $ 1 m $ 1.8 m $ 12.4 m $ 4.6 m $ 0.8 m - $ 17.8 m $ 16.0 m 2062 - $ 0.6 m $ 1 m $ 1.8 m $ 12.4 m $ 4.6 m $ 0.8 m - $ 17.8 m $ 16.0 m 2063 - $ 0.6 m $ 1 m $ 1.8 m $ 12.4 m $ 4.6 m $ 0.8 m - $ 17.8 m $ 16.0 m 2064 - $ 0.6 m $ 1 m $ 1.8 m $ 12.4 m $ 4.6 m $ 0.8 m - $ 17.8 m $ 16.0 m 2065 - $ 0.6 m $ 1 m $ 1.8 m $ 12.4 m $ 4.6 m $ 0.8 m - $ 17.8 m $ 16.0 m 2066 - $ 0.6 m $ 1 m $ 1.8 m $ 12.4 m $ 4.6 m $ 0.8 m - $ 17.8 m $ 16.0 m 2067 - $ 0.6 m $ 1 m $ 1.8 m $ 12.4 m $ 4.6 m $ 0.8 m $ 223.6 m $ 241.4 m $ 239.6 m TOTAL (real) $ 345 m $ 25 m $ 58.5 m $ 428.9 m $ 391.9 m $ 226.0 m $ 36.3 m $ 223.6 m $ 877.8 m $ 448.9 m Total $ 271.4 m $ 5.6 m $ 13.6 m $ 290.5 m $ 49.5 m $ 54.6 m $ 7.9 m $ 8.1 m $ 120.1 m -$ 170.4 m (discounted)
NPV BCR -$ 170.4 m 0.41
IRR 2.78%
A.2 Option 2 (200GL) CBA result (7% discount rate)
IS207200-0000-ZM-RPT-0001 A-2 Feasibility Study Report
Project Cost Project benefits On farm On-farm benefits - Year (ending Capital On farm benefits - Amenity and Residual dam Net benefits O&M Total Cost higher Total benefits June 30) costs costs current land recreation value value land use use 2018 ------2019 $ 29 m - - $ 29.1 m ------$ 29.1 m 2020 $ 39 m - - $ 38.8 m ------$ 38.8 m 2021 $ 97 m - - $ 97.1 m ------$ 97.1 m 2022 $ 117 m - - $ 116.5 m ------$ 116.5 m 2023 $ 107 m - - $ 106.8 m ------$ 106.8 m 2024 - $ 0.6 m - $ 0.6 m - - $ 0.5 m - $ 0.5 m -$ 0.0 m 2025 - $ 0.6 m - $ 0.6 m - - $ 1.1 m - $ 1.1 m $ 0.5 m 2026 - $ 0.6 m $ 3 m $ 3.3 m - $ 6.3 m $ 1.3 m - $ 7.5 m $ 4.2 m 2027 - $ 0.6 m $ 2 m $ 2.5 m - $ 10.7 m $ 1.3 m - $ 12.0 m $ 9.5 m 2028 - $ 0.6 m - $ 0.6 m - $ 10.7 m $ 1.3 m - $ 12.0 m $ 11.4 m 2029 - $ 0.6 m $ 2 m $ 2.3 m - $ 10.6 m $ 1.3 m - $ 11.9 m $ 9.6 m 2030 - $ 0.6 m $ 2 m $ 2.3 m - $ 10.5 m $ 1.3 m - $ 11.7 m $ 9.4 m 2031 - $ 0.6 m $ 2 m $ 2.3 m $ 0.1 m $ 10.2 m $ 1.3 m - $ 11.6 m $ 9.3 m 2032 - $ 0.6 m $ 2 m $ 2.4 m $ 0.6 m $ 9.9 m $ 1.3 m - $ 11.7 m $ 9.4 m 2033 - $ 0.6 m $ 2 m $ 2.5 m $ 1.5 m $ 9.5 m $ 1.3 m - $ 12.3 m $ 9.8 m 2034 - $ 0.6 m $ 2 m $ 2.6 m $ 2.7 m $ 9.2 m $ 1.3 m - $ 13.2 m $ 10.6 m 2035 - $ 0.6 m $ 2 m $ 2.7 m $ 4.0 m $ 8.8 m $ 1.3 m - $ 14.0 m $ 11.3 m 2036 - $ 0.6 m $ 2 m $ 2.8 m $ 5.2 m $ 8.5 m $ 1.3 m - $ 14.9 m $ 12.1 m 2037 - $ 0.6 m $ 2 m $ 2.9 m $ 6.4 m $ 8.1 m $ 1.3 m - $ 15.8 m $ 12.9 m 2038 - $ 0.6 m $ 2 m $ 3.1 m $ 7.7 m $ 7.8 m $ 1.3 m - $ 16.7 m $ 13.7 m 2039 - $ 0.6 m $ 1 m $ 1.4 m $ 8.9 m $ 7.5 m $ 1.3 m - $ 17.7 m $ 16.3 m 2040 - $ 0.6 m $ 1 m $ 1.5 m $ 10.1 m $ 7.3 m $ 1.3 m - $ 18.8 m $ 17.2 m 2041 - $ 0.6 m $ 1 m $ 1.7 m $ 11.3 m $ 7.3 m $ 1.3 m - $ 19.8 m $ 18.1 m 2042 - $ 0.6 m $ 1 m $ 1.7 m $ 12.0 m $ 7.3 m $ 1.3 m - $ 20.5 m $ 18.8 m 2043 - $ 0.6 m $ 1 m $ 1.8 m $ 12.4 m $ 7.3 m $ 1.3 m - $ 20.9 m $ 19.1 m 2044 - $ 0.6 m $ 1 m $ 1.8 m $ 12.4 m $ 7.3 m $ 1.3 m - $ 20.9 m $ 19.1 m 2045 - $ 0.6 m $ 1 m $ 1.8 m $ 12.4 m $ 7.3 m $ 1.3 m - $ 20.9 m $ 19.1 m 2046 - $ 0.6 m $ 1 m $ 1.8 m $ 12.4 m $ 7.3 m $ 1.3 m - $ 20.9 m $ 19.1 m 2047 - $ 0.6 m $ 1 m $ 1.8 m $ 12.4 m $ 7.3 m $ 1.3 m - $ 20.9 m $ 19.1 m 2048 - $ 0.6 m $ 1 m $ 1.8 m $ 12.4 m $ 7.3 m $ 1.3 m - $ 20.9 m $ 19.1 m 2049 - $ 0.6 m $ 1 m $ 1.8 m $ 12.4 m $ 7.3 m $ 1.3 m - $ 20.9 m $ 19.1 m 2050 - $ 0.6 m $ 1 m $ 1.8 m $ 12.4 m $ 7.3 m $ 1.3 m - $ 20.9 m $ 19.1 m 2051 - $ 0.6 m $ 1 m $ 1.8 m $ 12.4 m $ 7.3 m $ 1.3 m - $ 20.9 m $ 19.1 m 2052 - $ 0.6 m $ 1 m $ 1.8 m $ 12.4 m $ 7.3 m $ 1.3 m - $ 20.9 m $ 19.1 m 2053 - $ 0.6 m $ 1 m $ 1.8 m $ 12.4 m $ 7.3 m $ 1.3 m - $ 20.9 m $ 19.1 m 2054 - $ 0.6 m $ 1 m $ 1.8 m $ 12.4 m $ 7.3 m $ 1.3 m - $ 20.9 m $ 19.1 m 2055 - $ 0.6 m $ 1 m $ 1.8 m $ 12.4 m $ 7.3 m $ 1.3 m - $ 20.9 m $ 19.1 m 2056 - $ 0.6 m $ 1 m $ 1.8 m $ 12.4 m $ 7.3 m $ 1.3 m - $ 20.9 m $ 19.1 m 2057 - $ 0.6 m $ 1 m $ 1.8 m $ 12.4 m $ 7.3 m $ 1.3 m - $ 20.9 m $ 19.1 m 2058 - $ 0.6 m $ 1 m $ 1.8 m $ 12.4 m $ 7.3 m $ 1.3 m - $ 20.9 m $ 19.1 m 2059 - $ 0.6 m $ 1 m $ 1.8 m $ 12.4 m $ 7.3 m $ 1.3 m - $ 20.9 m $ 19.1 m 2060 - $ 0.6 m $ 1 m $ 1.8 m $ 12.4 m $ 7.3 m $ 1.3 m - $ 20.9 m $ 19.1 m 2061 - $ 0.6 m $ 1 m $ 1.8 m $ 12.4 m $ 7.3 m $ 1.3 m - $ 20.9 m $ 19.1 m 2062 - $ 0.6 m $ 1 m $ 1.8 m $ 12.4 m $ 7.3 m $ 1.3 m - $ 20.9 m $ 19.1 m 2063 - $ 0.6 m $ 1 m $ 1.8 m $ 12.4 m $ 7.3 m $ 1.3 m - $ 20.9 m $ 19.1 m 2064 - $ 0.6 m $ 1 m $ 1.8 m $ 12.4 m $ 7.3 m $ 1.3 m - $ 20.9 m $ 19.1 m 2065 - $ 0.6 m $ 1 m $ 1.8 m $ 12.4 m $ 7.3 m $ 1.3 m - $ 20.9 m $ 19.1 m 2066 - $ 0.6 m $ 1 m $ 1.8 m $ 12.4 m $ 7.3 m $ 1.3 m - $ 20.9 m $ 19.1 m 2067 - $ 0.6 m $ 1 m $ 1.8 m $ 12.4 m $ 7.3 m $ 1.3 m $ 267.2 m $ 288.1 m $ 286.4 m TOTAL (real) $ 388 m $ 25 m $ 58.5 m $ 472.2 m $ 379.5 m $ 331.6 m $ 55.0 m $ 267.2 m $ 1,033.4 m $ 561.3 m Total $ 305.5 m $ 5.6 m $ 13.3 m $ 324.3 m $ 45.9 m $ 71.9 m $ 11.7 m $ 9.7 m $ 139.1 m -$ 185.2 m (discounted)
NPV BCR -$ 185.2 m 0.43 IRR 3.01%
IS207200-0000-ZM-RPT-0001 A-3 Feasibility Study Report
A.3 Option 3 (300GL) CBA result (7% discount rate)
Project Cost Project benefits On farm On-farm benefits - Year (ending Capital On farm benefits - Amenity and Residual dam Net benefits O&M Total Cost higher Total benefits June 30) costs costs current land recreation value value land use use 2018 ------2019 $ 34 m - - $ 33.6 m ------$ 33.6 m 2020 $ 45 m - - $ 44.8 m ------$ 44.8 m 2021 $ 112 m - - $ 112.1 m ------$ 112.1 m 2022 $ 134 m - - $ 134.5 m ------$ 134.5 m 2023 $ 123 m - - $ 123.3 m ------$ 123.3 m 2024 - $ 0.6 m - $ 0.6 m - - $ 0.4 m - $ 0.4 m -$ 0.1 m 2025 - $ 0.6 m - $ 0.6 m - - $ 0.9 m - $ 0.9 m $ 0.3 m 2026 - $ 0.6 m - $ 0.6 m - - $ 1.3 m - $ 1.3 m $ 0.7 m 2027 - $ 0.6 m $ 2 m $ 2.7 m - $ 4.9 m $ 1.6 m - $ 6.5 m $ 3.8 m 2028 - $ 0.6 m $ 3 m $ 3.6 m - $ 11.8 m $ 1.6 m - $ 13.4 m $ 9.8 m 2029 - $ 0.6 m - $ 0.6 m - $ 11.8 m $ 1.6 m - $ 13.4 m $ 12.8 m 2030 - $ 0.6 m $ 2 m $ 2.3 m - $ 11.8 m $ 1.6 m - $ 13.3 m $ 11.0 m 2031 - $ 0.6 m $ 2 m $ 2.3 m - $ 11.6 m $ 1.6 m - $ 13.2 m $ 10.8 m 2032 - $ 0.6 m $ 2 m $ 2.3 m $ 0.1 m $ 11.3 m $ 1.6 m - $ 13.0 m $ 10.7 m 2033 - $ 0.6 m $ 2 m $ 2.4 m $ 0.6 m $ 11.0 m $ 1.6 m - $ 13.2 m $ 10.8 m 2034 - $ 0.6 m $ 2 m $ 2.5 m $ 1.5 m $ 10.6 m $ 1.6 m - $ 13.7 m $ 11.2 m 2035 - $ 0.6 m $ 2 m $ 2.6 m $ 2.7 m $ 10.3 m $ 1.6 m - $ 14.6 m $ 12.0 m 2036 - $ 0.6 m $ 2 m $ 2.7 m $ 4.0 m $ 9.9 m $ 1.6 m - $ 15.5 m $ 12.8 m 2037 - $ 0.6 m $ 2 m $ 2.8 m $ 5.2 m $ 9.6 m $ 1.6 m - $ 16.4 m $ 13.5 m 2038 - $ 0.6 m $ 2 m $ 2.9 m $ 6.4 m $ 9.2 m $ 1.6 m - $ 17.3 m $ 14.3 m 2039 - $ 0.6 m $ 2 m $ 3.1 m $ 7.7 m $ 8.9 m $ 1.6 m - $ 18.1 m $ 15.1 m 2040 - $ 0.6 m $ 1 m $ 1.4 m $ 8.9 m $ 8.6 m $ 1.6 m - $ 19.1 m $ 17.7 m 2041 - $ 0.6 m $ 1 m $ 1.5 m $ 10.1 m $ 8.5 m $ 1.6 m - $ 20.2 m $ 18.6 m 2042 - $ 0.6 m $ 1 m $ 1.7 m $ 11.3 m $ 8.4 m $ 1.6 m - $ 21.2 m $ 19.6 m 2043 - $ 0.6 m $ 1 m $ 1.7 m $ 12.0 m $ 8.4 m $ 1.6 m - $ 22.0 m $ 20.2 m 2044 - $ 0.6 m $ 1 m $ 1.8 m $ 12.4 m $ 8.4 m $ 1.6 m - $ 22.3 m $ 20.6 m 2045 - $ 0.6 m $ 1 m $ 1.8 m $ 12.4 m $ 8.4 m $ 1.6 m - $ 22.3 m $ 20.6 m 2046 - $ 0.6 m $ 1 m $ 1.8 m $ 12.4 m $ 8.4 m $ 1.6 m - $ 22.3 m $ 20.6 m 2047 - $ 0.6 m $ 1 m $ 1.8 m $ 12.4 m $ 8.4 m $ 1.6 m - $ 22.3 m $ 20.6 m 2048 - $ 0.6 m $ 1 m $ 1.8 m $ 12.4 m $ 8.4 m $ 1.6 m - $ 22.3 m $ 20.6 m 2049 - $ 0.6 m $ 1 m $ 1.8 m $ 12.4 m $ 8.4 m $ 1.6 m - $ 22.3 m $ 20.6 m 2050 - $ 0.6 m $ 1 m $ 1.8 m $ 12.4 m $ 8.4 m $ 1.6 m - $ 22.3 m $ 20.6 m 2051 - $ 0.6 m $ 1 m $ 1.8 m $ 12.4 m $ 8.4 m $ 1.6 m - $ 22.3 m $ 20.6 m 2052 - $ 0.6 m $ 1 m $ 1.8 m $ 12.4 m $ 8.4 m $ 1.6 m - $ 22.3 m $ 20.6 m 2053 - $ 0.6 m $ 1 m $ 1.8 m $ 12.4 m $ 8.4 m $ 1.6 m - $ 22.3 m $ 20.6 m 2054 - $ 0.6 m $ 1 m $ 1.8 m $ 12.4 m $ 8.4 m $ 1.6 m - $ 22.3 m $ 20.6 m 2055 - $ 0.6 m $ 1 m $ 1.8 m $ 12.4 m $ 8.4 m $ 1.6 m - $ 22.3 m $ 20.6 m 2056 - $ 0.6 m $ 1 m $ 1.8 m $ 12.4 m $ 8.4 m $ 1.6 m - $ 22.3 m $ 20.6 m 2057 - $ 0.6 m $ 1 m $ 1.8 m $ 12.4 m $ 8.4 m $ 1.6 m - $ 22.3 m $ 20.6 m 2058 - $ 0.6 m $ 1 m $ 1.8 m $ 12.4 m $ 8.4 m $ 1.6 m - $ 22.3 m $ 20.6 m 2059 - $ 0.6 m $ 1 m $ 1.8 m $ 12.4 m $ 8.4 m $ 1.6 m - $ 22.3 m $ 20.6 m 2060 - $ 0.6 m $ 1 m $ 1.8 m $ 12.4 m $ 8.4 m $ 1.6 m - $ 22.3 m $ 20.6 m 2061 - $ 0.6 m $ 1 m $ 1.8 m $ 12.4 m $ 8.4 m $ 1.6 m - $ 22.3 m $ 20.6 m 2062 - $ 0.6 m $ 1 m $ 1.8 m $ 12.4 m $ 8.4 m $ 1.6 m - $ 22.3 m $ 20.6 m 2063 - $ 0.6 m $ 1 m $ 1.8 m $ 12.4 m $ 8.4 m $ 1.6 m - $ 22.3 m $ 20.6 m 2064 - $ 0.6 m $ 1 m $ 1.8 m $ 12.4 m $ 8.4 m $ 1.6 m - $ 22.3 m $ 20.6 m 2065 - $ 0.6 m $ 1 m $ 1.8 m $ 12.4 m $ 8.4 m $ 1.6 m - $ 22.3 m $ 20.6 m 2066 - $ 0.6 m $ 1 m $ 1.8 m $ 12.4 m $ 8.4 m $ 1.6 m - $ 22.3 m $ 20.6 m 2067 - $ 0.6 m $ 1 m $ 1.8 m $ 12.4 m $ 8.4 m $ 1.6 m $ 287.2 m $ 309.5 m $ 307.7 m TOTAL (real) $ 448 m $ 25 m $ 57.8 m $ 531.4 m $ 367.2 m $ 368.0 m $ 67.2 m $ 287.2 m $ 1,089.6 m $ 558.2 m Total $ 352.6 m $ 5.6 m $ 12.6 m $ 370.7 m $ 42.5 m $ 74.4 m $ 13.9 m $ 10.4 m $ 141.1 m -$ 229.6 m (discounted)
NPV BCR -$ 229.6 m 0.38
IRR 2.66%
IS207200-0000-ZM-RPT-0001 A-4 Feasibility Study Report
Appendix B. Evidence supporting project need
This Appendix provides the evidence supporting the project need discussed in Section 1.
A summary of the service needs identified, their cause, effect and relevant evidence is provided in Table 9.1:
Table 9.1 : Service need summary of cause, effect and relevant evidence
Service need Summary of cause Summary of effect Relevant evidence
Service need 1: · Available water can only be · Water availability is not · Existing water entitlements delivered in ‘boom or bust’ timed for optimal application available to irrigators in the fashion Border Rivers and their Unreliable water supply, will · Land use productivity relative reliability continue to erode agricultural · High water losses from on- fluctuates, thereby productivity in the Border Rivers farm dams built to manage increasing uncertainty and · Estimated water losses in catchment. some of this lack of reliability anxiety for farmers delivery and on on-farm · Water buy-backs (past and · Farmers cannot forward sell dams. planned) in the region to cotton, which limits their comply with Basin Plan financial stability · Climate variability (including · Land-use is constrained to drought). annual crops which do not take full advantage of the region’s potential
Service need 2: · Low water security – · Irrigators cannot make long · Potential of higher value meaning that in some years, term investment decisions to land use farmers will receive zero shift to higher value land-use Low security of supply prevents · Barriers to investment allocations due to the inability to long-term on-farm investment · Importance of water security guarantee a minimal annual that supports the local economy. · Inability to secure bank for the local community. loans for investments in supply of water higher value / more · Town population and socio- productive land use. economic profile at risk of decline · Inability to attract and/or secure a high value workforce in the region.
B.1 Evidence supporting Service Need 1
B.1.1 Existing water availability and reliability within Border Rivers
The current water entitlements for NSW Border Rivers, as outlined in the Water Sharing Plan (2009) is summarised in Table B.2. The licence types are listed in order of descending security, noting that whenever supply capability is insufficient to satisfy 100% of orders, water is first allocated to domestic and stock access licences, local water utility access licences and regulated river (high security) access licences that have placed orders for water. Once that water has been assigned, the remaining supply is to be shared between regulated river general security – A class (first priority) and general security B class access licences (second priority) (NSW Department of Water and Energy, 2009b).
Unregulated water consists of access to water from tributary rivers downstream of, and not regulated by, Glenlyon and Pindari Dam. Access to unregulated (supplementary) water is only permitted after other needs
IS207200-0000-ZM-RPT-0001 B-1 Feasibility Study Report
(environmental and supply to all other regulated river licences) have been met (NSW Department of Water and Energy, 2009b).17
In 2009, it was estimated that in any given year an average of 70% of supplementary water shares are available (NSW Department of Water and Energy, 2009a). However the recent average between 2009 and 2015 has been much lower. These issues are discussed further in following section.
Table B.2 : Current Water Entitlements for NSW Border Rivers
Irrigators have access to a combination of general security water (A class and B class) and supplementary water. The large majority of their water share is from general security Class B (close to two thirds).
The following chart provides the projected long term average reliability of general security water (general security B) for NSW at the start of the water year. Based on this projection, General Security B receives in excess of 48% of water shares 50% of the time. The area under the cure (49%) is taken as the average annual water reliability.
Figure B.1 : Long term annual water reliability for general Security B at the start of water year (provided by WaterNSW, 2017)
The problem with reliability relates to the high variation in availability year on year that reduces business certainty. As can be seen below, since 2001, annual cumulative water allocations (as a share of licence volume)
17 As such, supplementary access is only allowed once unregulated water has been assigned to the protection of critical natural river benches and to accommodate any rules to ensure provision of passage of some inflows through Pindari Dam (translucency releases) and the periodic release of pulse flows to stimulate downstream ecological processes (NSW Department of Water and Energy, 2009b).
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have fluctuated between a low of 2% of water shares to 95% of water shares. Forward planning, selling and investment is extremely challenging under these circumstances.
Figure B.2 : Variable allocations announced for General Security B licences in NSW Border Rivers (source: NSW, DPI)
The following diagram provides a summary of total water use across Border Rivers (NSW and Queensland) from both unregulated and regulated source between 2006-07 and 2015-16.
Figure B.3 : Border Rivers water use history 2006-07 to 2015-16 (BRC Annual Report 2015-16) Figure B.3 demonstrates the high variability of supply. It also demonstrates that while unregulated supply makes up nearly a third of total licence volume in NSW (supplementary water), it makes up a much smaller portion of usage. This is due to very low reliability of supply, as well as high water losses through evaporation (discussed in more detail below).
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Despite a long term average of 70% reliability of supplementary water in NSW Border Rivers, between 2009 and 2015 the average allocation over that period was 37%, with a low of 2% in 2014-15. There was only one year during that period where supplementary access events allowed irrigators to access 100% of their licence share (120GL). This boom and bust supply is a major constraint on productivity and a barrier to longer term investment.
Figure B.4 : Supplementary water (NSW) allocations as % of licence share (120 GL)
B.1.2 High water losses
Farm storages used to store unregulated water by cotton farmers are highly inefficient. Although they benefit farmers by allowing them to access the water at a time when the water is actually needed, they incur high losses, meaning that the water available for use is significantly lower than the allocation volume.
Evaporation losses from on-farm storage depend on a number of factors including the surface area, the depth, air temperature, relative humidly, and wind speed. A study looking at 136 on-farm storages of various sizes and depths across the cotton industry reported evaporation losses exceeded 40% of the total available water. On- farm storage was the largest contributor of water loss (Cotton Catchment Communities CRC and NCEA, 2012). Therefore, it is estimated that a minimum of 48,000ML of the supplementary water shares are lost to evaporation and seepage from on-farm dams (when 100% of the water is allocated).
B.2 Evidence supporting Service Need 2
B.2.1 Potential of higher value land use
There is significant potential in NSW for further expansion of the almond industry. NSW DPI has modelled potentially suitable regions for almond industry expansion throughout Australia using bioclimatology The Border Rivers is one of the irrigation areas identified as having potential for production expansion (See Figure B.5 and Figure B.6.
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Figure B.5 : Example of productive regions for almond industry expansion (NSW DPI, 2016)
Figure B.6 : Identified almond industry expansion potential (NSW DPI, 2016)
Global trends are driving increased demand for nuts and nut products. The potential for almond industry expansion has been recognised by governments and the private sector. Some recent statistics from the Almond Board of Australia include the following:
IS207200-0000-ZM-RPT-0001 B-5 Feasibility Study Report
· Sales on the domestic market increased by 4% during the marketing year from March 2015 to February 2016, and totalled 22,915 tonnes. Of this, 21,208 tonnes were Australian almonds and 1,707 tonnes were imported · Over the past five years domestic sales have increased by 46% · In 2015, a record crop of 82,509 tonnes was grown, with export sales increasing by 481% from 2010. · Australia is still a small player in a growing sector (Almond Board of Australia, 2016). The Californian industry produces approximately 80% the world’s almonds, but Australia has recently become the second largest producer. Within Australia, most of the almond plantings are in Victoria (64% in Sunraysia), followed by South Australia (20%) and NSW (12%) (Almond Board of Australia, 2016).
Table B.3 provides a summary of the relative gross margin of almond and cotton irrigation. Once the upfront investment is made (land use change, plantings, equipment etc.), almonds are a higher value land-use option per hectare and per ML of water used.
Table B.3 : Gross margin comparison of cotton and almond growing
Land use ML/Ha T/Ha Gross Margin ($/Ha) Gross Margin ($/ML)
Cotton growing 9.0 1.8 $2,575 $286
Almond growing 12.5 2.0 $12,800 $1,024
Source: Various sources including NSW Agriculture (2003), NSW DPI (2014-15), Rural Solutions (2006) escalated to 2017-18 dollars.
B.2.2 Barriers to investment The decision to shift to high value land use is one that does not come easily. There is significant up-front investment in land establishment costs as well as machinery that would only be considered by farmers if there was a guaranteed increase in water security. Irrigators have advised WaterNSW that they need a significant decrease in the likelihood of zero or low water determinations to commit to the high up-front investment needed for land use change. Table B.4 below provides a summary of the costs associated with shifting one hectare of irrigated land from cotton to almond production.
Table B.4 : Up-front investment costs to shift from cotton to almond irrigation
Cost component Assumption Description/ Source
Land establishment cost 18,104/ha Establishment costs of an almond orchard are very high. The estimated range was provided by the Victorian Department of Economic, Jobs, transport and Resources (DEJTR) – Agriculture Victoria and has been escalated to 2017. Further detail on this assumption is the cost-benefit analysis (in Section 6.1 This estimate does not include the cost of machinery (discussed below).
Machinery cost Approximately 1,224/ha/year A US Study has sample costs for almond orchard production that estimates machinery costs at approximately $35,000 per annum for a property that is 100 acre (approximately 40 ha) (US Agricultural Issues Centre, 2016). This has been used as a conservative estimate, which translates to approximately $1000/ha/year. This has been escalated to 2017/18 Australian dollars.
IS207200-0000-ZM-RPT-0001 B-6 Feasibility Study Report
More reliable and secure water will also allow increased investment in cotton growing infrastructure, as the land which can be cultivated annually will increase. In particular, a larger area of regular cultivation will promote converting furrow irrigation to more efficient overhead irrigation (e.g. lateral movement or centre-pivot overhead irrigation equipment).
Regulated water allocations are also a bankable asset. Holding increased volumes of water allocations - all other factors being equal - increases the value of the farm asset. Accordingly, assuming the new allocations are not funded by debt, banks will be able to increase the amount that they can lend to farmers with higher value assets (i.e. greater equity). The absence of sufficiently reliable regulated water allocations can undermine irrigators’ access to finance - yet another barrier to farm development and a move to higher-value cropping.
B.2.3 Importance of water security for the local economy Uncertainty about the availability of irrigation water is the most limiting factor in Australian cotton production systems (Roth et al, 2013). The reliability of water in the Border Rivers is significantly lower than some other valleys and this is reflected in land use being predominantly cotton. Such high dependence on annual crops which fluctuate in production in response to varying water supply creates financial uncertainty for farmers as well as their supporting industries and businesses. The pressure that this places on the local population, employment and skills and social disadvantage is evident from the socio-economic data for the Border Rivers summarised in Table B.5.
Table B.5 : Socio-economic profile summary for Border Rivers (ABS 2011 census data)
Socio-economic Relevant trends and comparison profile
Population growth · The population grew at significantly lower rate than the rest of NSW and the rest of Queensland between 2006 and 2016 (0.3%, 0.9% and 1.7% per annum respectively). · The NSW part of the Border River Irrigation Catchment grew slowest at 0.1% per annum compared with the Queensland part, which grew at 0.7% per annum.
Unemployment · Unemployment in the NSW sections of the Border River Catchment is relatively high. · In the NSW Border Rivers (other than the Gwydir LGA), unemployment rates were higher than 8.2% in March 2017 compared with 6.9% for nearby regions (New England and the North West region) and 4.6% NSW. · In contrast, unemployment in the Queensland sections of the Border River Catchment is relatively low. In March 2017 unemployment of the relevant sections was below the total Queensland unemployment rate of 6.3% and the region of Darling Downs West- Maranoa.
Skills and education · The Border River Catchment has a lower proportion of people with a bachelor degree and greater qualifications than the rest of NSW and QLD. · In 2011, the proportion of employed persons aged 15 years and over with a bachelor degree or greater qualifications in the Border River Catchment was 18% compared to 29% for the rest of Queensland and 23% for the rest of NSW and the New England and North West community.
Socio-economic · The Border River Catchment has a relatively high socio-economic disadvantage within disadvantage NSW and QLD and within Australia, based on the 2011 SEIFA level of socio-economic disadvantage. · All of the Border River Catchment LGAs and SLAs were in the bottom 2 or 3 deciles for Australia except for the Goondiwindi LGA, which had a middle level of disadvantage. · The Moree Plains LGA was in the lowest decile for NSW.
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As a comparison, the Murrumbidgee has significantly higher water security than Border Rivers. Zero allocations of general security water shares will occur less than 1% of the time with allocations less than 10% of water shares only occurring 4 out of every 100 years. This water security is reflected in improved productivity and irrigator certainty in the region.
Irrigated cropping occurs within the Murrumbidgee Irrigation Area (MIA) on the northern side of the river, in the Coleambally Irrigation Area on the southern side of the river, and along the Yanco Creek system. As a comparison to the Border Rivers, the MIA supports higher value irrigation, with prominent crops being rice, corn, wheat, grapes and citrus.
Table B.6 provides a summary of land use in the MIA.
Table B.6 : MIA land use summary (MIA annual report, 2015-2016)
Irrigated crop (2015/16) Ha %
Cereals, oilseeds 49,206 42.4
Citrus, vines, other fruit 30,754 26.5
Cotton 12,650 10.9
Pasture 5,919 5.1
Rice 12,302 10.6
Vegetables 1,625 1.4
Other 3,714 3.2
Total area of irrigated crop 116,053* 100%*
*Difference in totals is due to rounding.
Figure B.7 provides a further breakdown of land use in the MIA. As can be seen from the distribution of crop types below, land use within MIA is more diverse and of higher value than that in the Border Rivers. Higher value crops such as citrus, vines and other fruit, as well as vegetables make up over a quarter of total land use.
IS207200-0000-ZM-RPT-0001 B-8 Feasibility Study Report
Figure B.7 : MIA crop types as % of total hectares planted (MIA annual report, 2015-2016)
Whilst not entirely attributable to higher water reliability and security, the more diverse and stable land use in the region appears to be contributing to a more resilient socio-economic profile. For example: · The area is growing economically, with many parts (Griffith, Murrumbidgee, and Carrathool) experiencing lower unemployment than the State average. · The Murrumbidgee catchment’s employment is also less dependent on agriculture and fishing compared with the NSW section of Border Rivers (22% and 34% respectively). The increased diversity in Murrumbidgee represents a more resilient and diverse economy.
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Appendix C. Review of previous studies
Investigations into the possible construction of a dam on the Mole River began in the late 1950s. Preliminary investigations conducted in 1961, 1984 and 1991 considered several sites, and indicated that a site on the Upper Mole River near “Ringtree” was the preferred option. Presumably due to a lack of funding, investigations have not proceeded significantly since 1991.
As a basis for the selection of options, a review of background documents was undertaken. Selected studies are summarised and discussed below.
C.1 Water Conservation and Irrigation Commission, 1961 (Water Conservation and Irrigation Commission, 1961)
During March 1961, the Water Conservation and Irrigation Commission investigated a potential dam site on the Dumaresq River at Mingoola (Water Conservation and Irrigation Commission, 1961). The Mingoola Dam Site was considered unfavourable due to “unsatisfactory foundation conditions”, prompting the study of alternative sites on four tributary streams – Pike Creek, Mole River, Severn River and Tenterfield Creek.
After initial investigation, sites on the Severn River and Tenterfield Creek were found to have insufficient storage capacity and excluded from further study.
The Pike Creek site was investigated in greater detail, and finally the Border Rivers Commission recommended construction of storages in three stages:
1) Construction of Dam on Pike Creek in the first instance
2) Later enlargement of the Pike Creek dam by means of the installation of crest gates
3) If required, construction of a dam on the Mole River with a storage capacity of 430,000 acre feet (530,000 ML) at a later date
A site on the Mole River at “Bellanboe” (later referred to as the Lower Mole site) was investigated by means of preliminary geophysical, hydrographic and topographical survey, as well as limited core drilling. The site was considered suitable, but more investigation needed.
C.2 Border Rivers Commission, 1984 (The Additional Storages Commission, 1984)
After the completion of Glenlyon Dam on Pike Creek in 1976, irrigation development increased and the potential need for more water emerged. A report by the “Additional Storages Committee” (The Additional Storages Commission, 1984) investigated the following options, concluding that the most cost effective major storage option for the Border Rivers System would be a dam on the Mole River:
C.2.1 Re-regulating weirs on the Macintyre River
The study found that the construction of a weir at Goondiwindi to be technically feasible and economically justified. The weir was subsequently constructed and named Boggabilla Weir.
C.2.2 Enlargement of Glenlyon Dam
The enlargement of Glenlyon dam was investigated, by means of the installation of 8,5m high spillway gates, thereby increasing capacity from 253 000 ML to 440 000 ML. It was noted that “the benefit to be gained by raising Glenlyon Dam would be very limited, as the storage would rarely fill above the existing capacity”.
C.2.3 A dam on the Dumaresq River at Mingoola
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The merits of Mingoola Dam were briefly discussed and the option discounted, due to:
· Engineering problems associated with alluvium up to 75m deep
· Large spillway requirements
· Submergence of the outlet works of Glenlyon Dam storages greater than 60,000 ML.
C.2.4 A diversion scheme from the Severn River to Glenlyon Dam
The option investigated comprised of an 11 kilometre diversion tunnel with diameter of 2.5m, providing a maximum diversion rate of 1200 ML/day. It was found that the scheme may have offer a reasonable improvement in available supply, but more detailed investigations would be necessary.
The environmental consequences of the diversion were not investigated, but it was postulated that there could be significant environmental impacts, at the nearby Sundown National Park and elsewhere.
C.2.5 A dam on the Severn River
A dam site upstream of Sundown National Park in Queensland was considered. No field investigations were undertaken. Preliminary analysis indicated that further study would be warranted, but noted that the proximity of Sundown National Park could delay environmental authorisation.
C.2.6 Mole River Dam
Preliminary investigations for two sites, at Bellanboe (Lower Mole) and Ringtree (Upper Mole) were reviewed, focussing on the former site. Sizes between 100,000 and 530,000 ML were considered.
The Mole River Dam was found to be the most cost effective major storage option available to the BRC. Economic analysis appeared to favour smaller storage capacities than 530,000 ML.
An abandoned arsenic mine of some heritage significance would be submerged by a large storage on the Lower Mole site, prompting pollution and water quality concerns.
C.3 Border Rivers Commission, 1990 (Water Resources Commission, 1990)
A reinvestigation of storage options in the Border Rivers system was undertaken by the NSW Department of Primary Industries - Water Resources Commission in 1990 (Water Resources Commission, 1990). This study recommended the further investigation of the “Ringtree”, or Upper Mole site. Options considered comprised of:
C.3.1 Diversion from Severn River to Pike Creek (Glenlyon Dam)
Two variations were investigated:
· Diversion to Pike Creek to supplement existing storage in Glenlyon Dam
· Diversion to Pike Creek to supplement Glenlyon Dam enlarged by means of spillway gates
The proposed diversion is located within the Sandown National Park, and changes to river flow would affect aquatic environments. The area inundated at the diversion was considered to have high conservation value.
C.3.2 Severn River Dam
Due to a lack of suitable clay reserves, geological investigation suggested concrete faced rock fill as the most suitable type. Dams of 100 000, 300 000 and 500 000 ML capacity were investigated.
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The area of inundation includes Crown Land that was believed to be of high conservation value and largely undisturbed. The dam would also affect several aquatic habitats in the downstream Sundown National Park and potentially impact the brush-tailed rock wallaby, an inhabitant of the area adjacent to the embankment.
C.3.3 Lower Mole River Dam
Dams of 100 000, 300 000 and 500 000 ML capacity were investigated. The nature of the site and availability of materials appeared to favour rockfill dams.
Large portions of the potential inundation area are disturbed. A concern was noted that, for dam capacities greater than 500 000 ML, the abandoned Mole River arsenic mine would be affected by certain flood events. There may be significant cost associated with managing the associated risks if inundated.
An aboriginal site, adjacent to the Mole River Road near its intersection with Gibraltar Road would be inundated by the dam storage.
C.3.4 Upper Mole River Dam
Dams of 100 000, 300 000 and 500 000 ML capacity were investigated, and the nature of the site and availability of materials again appeared to favour rockfill dams.
At the time there were no known cultural or heritage sites in the inundation area. Much of the potential inundation area is disturbed and believed to be of lesser environmental importance.
C.3.5 Lower Mole River Dam with Tenterfield Creek Diversion
A diversion from the Tenterfield Creek towards the Lower Mole was shown to have the ability to increase average annual supplies significantly. The combination Lower Mole Dam with Tenterfield Creek Diversion was shown to have a favourable benefit/cost ratio, but was associated with a high capital investment compared to the Upper Mole option.
C.4 Border Rivers Commission, 1991 (Water Resources Commission, 1991)
A further, more-detailed investigation of the Upper Mole site was completed in 1991 (Water Resources Commission, 1991) as a supplementary report to (Water Resources Commission, 1990), and described the results of additional investigative work done for the Mole River sites including:
· Limited geological investigations of the Upper dam site, including seismic traverses and trenching.
· Updated engineering assessments based on the results of the site investigations
· Cultural heritage surveys for the Upper and Lower sites.
The supplementary study concluded that: · Foundation conditions were suitable at the Upper Mole site, and competent rock was discovered at a higher level than initially assumed · The optimal scale of development for the Upper Mole Dam was of the order of 360 to 400 GL · The Lower Mole Dam in the scale range of 500 to 550 GL, together with the Tenterfield Creek diversion, offered a higher average annual supply, at a higher benefit/cost ratio when compared to the Upper Mole Dam. The capital cost associated with optimal development of the Lower Mole Dam was significantly higher · Economic indicators for the two sites were similar.
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· The Lower Mole Dam appeared to have greater heritage sensitivity, with the arsenic mine and some Aboriginal sites affected.
The supplementary report recommended that any further studies for a major storage should be focussed to the Upper Mole site at Ringtree.
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Appendix D. Flood hydrology
D.1 Purpose The purpose of the flood hydrology for the Project is to produce peak flow rates and hydrographs for a variety of events to inform the concept design of the Upper Mole River dam. The location of the site and the hydrologically significant features are shown in Figure D.1.
The hydrology was completed to a level of detail suitable to assess the feasibility of the Upper Mole River dam. The hydrological analysis was undertaken using Flood Frequency Analysis and rainfall-runoff modelling using the non-linear store routing programme, RORB. Details of work undertaken are presented in the following sections.
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Figure D.1 : Localities of interest
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D.1.1 Previous studies Flood hydrology has previously been completed in the “Mole and Severn River Damsites: Yield Analysis and Flood Hydrology” (Water Resources Commission, 1990) report. This report undertook flood hydrological analysis using Flood Frequency Analysis (FFA), and Rainfall-Runoff modelling using RORB.
The FFA relevant to the current study was completed for the Mole River at Donaldson (416032) gauge, which has a record from 1969 to 1988. The record was further extended with the Mole River at Trenayr (416004) gauge, which had a record from 1924 to 1974. The FFA was completed using the computer program WS06, and it was concluded that the best fit was provided by the Log-Pearson III (LP3) distribution. No details on the fitter technique were provided. As the results were only documented in a chart, values for a variety of Annual Exceedance Probabilities (AEP) have been interpreted and are presented in Table D.1.
Table D.1 : Previous FFA Results Mole River at Donaldson
AEP (1 in Y years) Quantile (m3/s) Lower Confidence Limit Upper Confidence Limit (m3/s) (m3/s)
10 550 380 800 20 800 500 1,400 50 1,250 700 3,400 100 1,600 800 3,400 200 2,150 900 5,000
A RORB Rainfall-Runoff model of the catchment was created and calibrated to five events listed together with other details in Table D.2. The adopted kc value was 34.84 and m value was 0.8. The adopted loss values were 0mm Initial Loss and 2.5mm/h Continuing Loss, although higher loss values were used for rarer events. Design rainfalls for the 5%, 1%, 0.1% and 0.01% AEP events, as well as the Probable Maximum Precipitation event, were calculated or obtained, with the AEP of the PMP being assigned a value of 0.0001% (1 in 1,000,000). The resulting peak flows are presented in Table D.3.
Table D.2 : Details of the previous reports calibration events
Event Peak flow m kc Initial Loss mm Continuing Loss (baseflow mm/h removed) m3/s
28/09/1970 307 0.8 41.5 37 0.1 01/02/1971 634 0.8 22.2 0 4.2 18/02/1971 107 0.8 43.1 0 3.0 18/02/1972 412 0.8 31.4 37 0.2 10/02/1976 1578 0.8 36.0 55 3.5
Table D.3 : Adopted Peak Flows from previous report
Duration (hours) 5% 1% 0.1% 0.01% PMF
6 470 1,400 6,200 9,400 15,700 9 920 2,100 7,200 10,500 18,600 12 670 1,700 6,500 10,000 18,600 24 780 2,000 4,900 8,100 16,300
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Duration (hours) 5% 1% 0.1% 0.01% PMF
48 600 1,600 3,900 5,700 11,500 72 740 1,900 3,400 5,400 10,600
D.2 Flood Frequency Analysis A Flood Frequency Analysis (FFA) was completed for the Mole River at Donaldson (416032) gauge. This involved fitting a peak flow series to a statistical distribution. The major steps in FFA are:
· Obtain flow data - Extract peak flow series from a gauged record - Review the peak flow series to ensure no spurious data is included in the analysis. · Regional parameter information - Obtain regional information about distribution parameters. · Fit distribution - Fit flood frequency curve (or distribution) - Review fit and check for overly influential flow records - Censor influential flow, both large and small - Incorporate regional parameter information into analysis as priors to the Bayesian analysis. · Review results
D.2.1 Approach The methods adopted for the FFA are based on the methods and recommendations contained within Australian Rainfall and Runoff (ARR16) Book 3 Chapter 2 on “At Site Flood Frequency Analysis” (Kuczera and Franks, 2016).
D.2.2 Flow data A peak annual series (peak flood levels, water year starting July) was extracted from flow gauging data for the Mole River at Donaldson (416032) gauge shown in Figure D.2. This gauge has 48 years of recorded flows (1969-2017) from a catchment area of 1,586 km2.
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Figure D.2 : Annual maxima flow series for the Mole River at Donaldson
Regional parameter information The Bayesian framework in FLIKE has the ability to incorporate regional parameter information as prior parameter information. Regional parameter information is available for the Log Pearson Type III distribution from the Regional Flood Frequency Estimate (RFFE) model, developed as part of ARR 2016 (ARR16) (Ball et al., 2016).
RFFE analysis was undertaken for the Mole catchment using the variable listed in Table D.4.
The resulting peaks flow with their confidence limits are shown in Figure D.3, and LPIII parameters together with the standard deviations are shown in Table D.5. The 1% AEP peak discharge was 3,370 m 3/s, with 90% confidence limits of +/- 860 m3/s - 12,900 m3/s.
Table D.4 : RFFE variables
Variable Value
Latitude at catchment outlet (degree) -29.0154 Longitude at catchment outlet (degree) 151.5997 Latitude at catchment centroid (degree) -29.25413 Longitude at catchment centroid (degree) 151.8885 Catchment area 1,600 km2
Table D.5 : RFFE parameters
Parameter Value Standard deviation
Mean (loge flow) 5.589 0.526 St dev (loge flow) 1.058 0.370
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Parameter Value Standard deviation
Skew (loge flow) 0.075 0.029
Figure D.3 : RFFE for Mole River at Donaldson
D.2.3 Fit distribution Flood frequency analysis was performed on the peak annual series described above. This involved fitting the Log-Pearson Type III (LPIII) distribution. The fit of the distribution was further refined by investigating Probable Influential Low Flows (PILF) and the regional parameter information. Discussions of these are presented below.
D.2.3.1 Probable Influential Low Flows Priors Inspection of the raw annual maxima data indicated that there were few low flow years which could be considered Probable Influential Low Flows (PILF). The influence of these low flows was investigated using the multiple Grubbs Beck test incorporated into FLIKE. This test found one PILF; this value was censored from in the FFA analysis.
D.2.3.2 Regional parameter information The regional parameter information obtained from the RFFE was incorporated into FLIKE as prior parameter information, including the standard deviation and covariance estimates. The standard deviation provides FLIKE with information about the uncertainty of the parameter estimate; a larger standard deviation means there is less certainty, while a smaller standard deviation indicates there is a greater certainty.
D.2.4 Results The flood frequency distribution resulting from inclusion the removal of the PILF and incorporation of the regional parameter information were adopted. The resulting Flood Frequency Curve is shown in Figure D.4 and the flood quantiles are listed in Table D.6.
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Figure D.4 : At-site flood frequency plot
Table D.6 : At-site flood quantiles
1 in Y AEP Flood Quantiles (m3/s) Lower Confidence Limit Upper Confidence Limit (m3/s) (m3/s)
2 110 90 150 5 320 230 450 10 550 380 830 20 860 580 1,400 50 1,500 900 2,500 100 2,100 1,200 3,800 200 2,800 1,600 5,500
D.3 Hydrologic modelling
The purpose of the hydrologic modelling was to model the catchment’s response to rainfall, determine flow hydrographs, and examine the impact of the Upper Mole River Dam on runoff downstream for a variety of AEP events. To achieve these aims, a rainfall runoff model was developed using the RORB non-linear routing programme. This section sets out the development of the RORB model and the preparation of the input data.
To determine flood peaks for Vary Rare and Extreme floods, event based rainfall methods are preferred in Australian practice (Ball et al, 2016), using ensemble or Monte Carlo simulations. A Monte Carlo simulation has been completed as part of this assessment for the required events, with the exception of the Probable Maximum Flood (PMF). The PMF has been determined using the Generalised Tropical Storm Method (GTSMR) method, as outlined by the Bureau of Meteorology (BoM). While the PMF has been determined using a different procedure to more frequent AEP events, it is convenient to present the method in this Section.
This section is presented under the following headings:
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· Rainfall runoff model – describes the catchment delineation and reach definition
· Calibration – sets out the calibration of the RORB model to determine the kc parameter · Design rainfall – present the design rainfall used in the analysis including the Probable Maximum Precipitation · Design losses – describes the design losses used in the Monte Carlo simulation · Monte Carlo results – presents the results of the Monte Carlo simulation · PMF modelling – Presents the results of the PMF modelling.
D.3.1 Rainfall runoff model A RORB hydrologic model was created to represent the catchment to the Dumaresq gauge. CatchmentSIM was used to generate sub-catchments within the area of interest (see Table D.7). ArcRORB was used to create the catchment file used by RORB (see Figure D.5). The resulting catchment areas are listed in Table D.7. Glenlyon Dam was modelled as a reservoir within RORB. Dam storage/discharge and level/storage curves were obtained and used as input for the RORB model (see Table D.17). Note that whilst some details of the dam staging were available for Glenlyon dam, these were modified to allow the PMP flows through the dam. As the dam is downstream of the site of interest, this did not affect the results or conclusions regarding the Upper Mole River Dam. The RORB reaches within Glenlyon Dam were modelled as “drowned” reaches. All other reaches were modelled as “natural” reaches.
Table D.7 : Key catchment areas
Location Catchment Area km2
Upper Mole River Dam 1,550 Mole River @ Donaldson (416032) 1,590 Glenlyon Dam 1,320 Dumaresq @ Roseneath (416011) 5,510
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Figure D.5 : RORB model features
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D.3.2 Calibration
D.3.2.1 Model set-up Three historic flood events were used for calibration;
· 9-12th February 1976: Dumaresq @ Roseneath peak flow 5,685m3/s on 11th February 1976 Mole River @ Donaldson peak flow 1,659m3/s on 11th February 1976 · 2-6th January 1996: Dumaresq @ Roseneath peak flow 1,065 m3/s 4th on January 1996 Mole River @ Donaldson peak flow 797m3/s on 3rd January 1996 · 9-13th January 2011: Dumaresq @ Roseneath peak flow 3,707m3/s on 11th January 2011 Mole River @ Donaldson peak flow 1,250m3/s on 11th January 2011 These events represent the largest three events at the Mole River gauge, and the first, second, and fourth largest historical events recorded at Dumaresq gauge. This indicates that flood events the Mole River catchment and Dumaresq River catchment are strong correlated. Calibration was to recorded streamflow at both Dumaresq River and Mole River gauges. All three flood events were generated by storms in excess of 24 hours and produced hydrographs greater than 48 hours.
A gauge is located at the headwater of Glenlyon Dam, “416315A Pike Creek Glenlyon HW”. The historic water level data from this gauge was used to identify initial dam level information for historic flood events.
For all three events, rainfall depths for each subcatchment were gained by averaging the rainfall depth within the subcatchment extent, as sourced from AWAP (Australian Water Availability Project) rainfall depth grid data. Temporal patterns were determined from the available sub-daily rainfall gauges.
For the 1976 event, only one gauge in the area recorded sub-daily data (see Figure D.6). All sub-catchments derived temporal patterns from this gauge.
For the 1996 event, sub-daily rainfall data was gained from the Stanthorpe, Tenterfield and Glenlyon Dam rainfall gauges. Thiessen (Voronoi) polygons were created to identify which gauge would be used as a source for temporal pattern information for each sub-catchment (see Figure D.7).
For the 2011 event, sub-daily rainfall data was gained from the Stanthorpe, Tenterfield and Mole River at Donaldson rainfall gauges. Thiessen (Voronoi) polygons were created to identify which gauge would be used as a source for temporal pattern information for each sub-catchment (see Figure D.8).
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Figure D.6 : 1976
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Figure D.7 : 1996
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Figure D.8 : 2011
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D.3.2.2 Calibration Results Calibration involved running a “Fit” RORB scenario with an initial loss/continuing loss model. Two RORB parameters were involved in calibration; kc and m. The “Queensland (Weeks) – Eqn 3.23, ARR 1987 Book V)” method was utilised to determine a kc value of 84.62. A default value of m = 0.8 and initial loss = 0 was used for the first RORB calibration model runs.
Results for all three storm events with these parameters are shown in Figure D.9 to Figure D.11. Various initial loss values were tested, and the resulting hydrographs were found to be insensitive. The resulting fit of the models were considered suitable for purposes of the feasibility study and the RORB parameters adopted.
Figure D.9 : 1976 Calibration Results
Figure D.10 : 1996 Calibration Results
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Figure D.11 : 2011 Calibration Results
D.3.3 Design peaks
To determine the peak discharge for given AEP events, a Monte Carlo simulation was undertaken. This involves determining input into the simulation; namely rainfall inputs and design losses. Once these inputs are determined, the Monte Carlo simulation repeatedly samples the inputs to determine peak discharges and undertakes a statistical analysis to determine a flood frequency curve. Design flood hydrographs are then determined as set out in Section D.5.
While the determination of the Probable Maximum Flood (PMF) was undertaken using the GTSMR approach (BoM, 2003) rather than a Monte Carlo simulation, it is also presented here for convenience.
D.3.3.1 Design rainfall
1 to 2,000 year AEP Rainfall
The design rainfall depths were gained from intensity-frequency-duration (IFD) data developed by the Bureau of Meteorology (2016) as part ARR16. Design rainfall depths were estimated for burst durations between 24 and 168 hours. The resulting values are presented in Table D.8.
Given the size of the catchment of the catchment (1,590 km 2) and the historical response of rainfall in the catchment, it was considered that rainfalls less than the 24 hour duration would not reasonably lead to flood peaks in the catchment. For this reason, shorter duration storms were not considered. Further, given the purpose of the assessment is to assess the feasibility of the proposed dam, flood volumes are considered to be an important outcome of the model. Shorter duration storms will bias flood volumes to smaller values.
PMP Rainfall
PMP rainfall depth estimates for the Dumaresq gauge catchment were gained by applying the Generalised Tropical Storm Method (GTSMR) approach. The final PMP depths adopted are presented in Table D.8.
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Figure D.12 : PMP depth versus duration
AEP of PMP
The AEP assigned to the PMP is a function of the method used in its derivation. The recommendations by Laurenson & Kuczera (1999) are for a lower limit of 1 in 10,000,000 for catchments less than 100 km², and for the AEP of the PMP to vary as a power function of catchment area (i.e. linearly in log-log space) to an AEP of 1 in 104 for a catchment area of 100,000 km2. The Dumaresq gauge catchment has an area of 5,500 km2, and the estimated AEP of the PMP is 1 in 180,000. The Mole river gauge catchment has an area of 1,590 km 2, and the estimated AEP of the PMP is 1 in 630,000.
Interpolation of design depths between 1 in 2000 AEP and the PMP
The interpolation procedure as recommended ARR16 was used to interpolate between the 1 in 2000 and PMP design rainfall depths.
The design rainfall depth versus frequency data is provided in Table D.8 and the curves are plotted in Figure D.13.
Adopted rainfall depths
Table D.8 : Design rainfall depth-duration-AEP table
Duration (hours)
AEP (1 in Y) 24 48 72 96 120 144 168
1 60 80 80 90 90 100 100 2 70 90 90 100 100 110 110 5 90 110 130 130 140 150 150 10 110 140 150 160 170 170 170 20 130 160 170 180 190 190 190 50 160 190 210 220 220 220 230 100 180 220 230 240 250 250 250
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Duration (hours)
AEP (1 in Y) 24 48 72 96 120 144 168
200 210 250 260 270 270 280 280
500 240 290 300 310 310 310 320
1,000 280 330 330 340 340 340 350
2,000 310 360 370 370 370 380 380
5,000 370 410 420 430 440 N/A N/A
10,000 410 470 480 500 520 N/A N/A
20,000 460 530 560 580 610 N/A N/A
50,000 530 640 690 730 790 N/A N/A
100,000 590 750 830 890 1010 N/A N/A
200,000 (PMP) 640 870 980 1070 1250 N/A N/A
Figure D.13 : Design rainfall depth-duration-AEP curves
Pre-burst rainfall The analysis of storms can be undertaken to include the entire or complete storm or just the most intense rainfall burst (storm burst). When only storm burst are analysed, the pre-burst rainfall should be incorporated into the analysis. This is typically done by changing the loss value; however, where gauge data is available, such as for the Mole River catchment, this is not necessary. For this reason, pre-burst rainfall was not incorporated into the analysis.
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D.3.3.2 Design and Monte Carlo temporal patterns Monte Carlo temporal patterns were gained from the ARR16 Data Hub website for the Mole River catchment.
Temporal patterns for deterministic runs were a subset from this dataset. Patterns were chosen for RORB for durations from 24 hour up to 168 hour (see Figure D.14). Selection of patterns was based on pattern AEP classification, with only “intermediate” patterns chosen, and patterns having one main peak.
Figure D.14 : Temporal Patterns for design runs used in RORB
D.3.3.3 Design spatial patterns The 1% AEP 48 hour IFD results were obtained from BoM for a grid across the catchment. The point IFD values were converted to a spatial grid and the mean rainfall depth within each subcatchment was calculated. The ratio of the individual subcatchments’ means relative to the overall average was calculated, which was used to determine the spatial distribution or pattern of design rainfall. This was input to the RORB model.
D.3.3.4 Monte Carlo Losses
For the Monte Carlo runs, an initial/continuing loss model was adopted. An initial loss of 20mm and continuing loss of 1mm was used, to better align Monte Carlo results with the flood frequency analysis.
Monte Carlo initial loss distribution was adopted as per Table D.9.
Table D.9 : Monte-Carlo Initial Loss Distribution
Value Initial Loss Factor
0% 3.190 10% 2.260 20% 1.710 30% 1.400
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Value Initial Loss Factor
40% 1.200 50% 1.000 60% 0.850 70% 0.680 80% 0.530 90% 0.390 100% 0.140
D.3.3.5 Monte Carlo results Results at the proposed Upper Mole River Dam location from the Monte Carlo run are presented in Table D.10.
Table D.10 : Monte Carlo model results
AEP (1:Y) 24 hour 48 hour 72 hour 96 hour 120 144 168 Maximum Critical hour hour hour time (hour)
2 280 190 150 100 50 40 10 280 24 5 510 380 290 220 150 130 90 510 24 10 650 530 390 310 240 190 150 650 24 20 880 720 540 440 350 290 230 880 24 50 1,180 990 780 660 470 420 340 1,180 24 100 1,390 1,180 950 830 560 550 440 1,390 24 200 1,730 1,390 1,160 1,000 690 660 550 1,730 24 500 2,210 1,780 1,560 1,180 920 810 690 2,210 24 1,000 2,760 2,120 1,810 1,300 1,060 920 810 2,760 24 2,000 3,190 2,410 2,040 1,600 1,170 1,050 980 3,190 24 5,000 3,960 2,980 2,450 1,920 1,510 1,240 1,250 3,960 24 10,000 4,590 3,470 2,810 2,110 1,970 1,480 1,480 4,590 24 20,000 5,230 4,080 3,190 2,600 2,420 1,920 1,810 5,230 24 50,000 5,940 5,040 4,190 3,640 3,240 2,690 2,520 5,940 24 100,000 6,550 5,930 5,060 4,670 4,170 3,590 3,370 6,550 24
D.3.3.6 PMP Modelling Two PMP events were run; the 48 hour and the 72 hour event. PMF was modelled using ARR 1987 (ARR87) (Pilgrim, 1987) temporal patterns. No spatial distribution of depths was adopted. Initial losses were set as zero, with continuing losses set as 2mm/hr.
Results at the proposed Upper Mole River Dam location from the PMP runs are as per Table D.11 and Figure D.15.
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Table D.11 : PMP RORB results
Model Run Peak flow (m3/s) Volume (m3)
48hr, temporal pattern 1 14,560 1,200,000,000 48hr, temporal pattern 2 13,640 1,200,000,000 72hr, temporal pattern 1 15,380 1,290,000,000 72hr, temporal pattern 2 14,260 1,290,000,000
Figure D.15 : PMP Hydrographs
D.4 Adopted Peak flow
Peak flows have been determined using FFA and rainfall-runoff modelling as outlined in the previous sections. It is therefore necessary to adopted peak flows for the assessment. In general, gauged flows provide the most certain estimate of runoff for the range of AEPs equivalent to, or slightly greater than, the length of the gauge record. However, extrapolation significantly beyond ‘the range of experience” is not recommended. For flows rarer than those that can be reasonably determined from gauged data, in particular those that are considered to be Very Rare to Extreme, rainfall methods are preferred. Clearly, there is a transition from FFA results to the rainfall-runoff results. In addition, peak flows can also be extracted from the deterministic hydrographs prepared as outlined in Section D.5. While the deterministic peaks do not have any theoretical advantages over the FFA or Monte Carlo peaks, they can provide a convenient interpolation point.
This section outlines the determination of the peak values in the ‘transition zone’ and the adopted peak flows across a range of AEP.
D.4.1 FFA peaks
The length of record at the Mole River gauge is 48 years. This indicates that, for AEP’s more frequent than 1 in 50 year event, FFA peak flows will be the most accurate of the compared methods, whereas the FFA calculated peaks for AEP’s rarer than the 1 in 100 year event will be less accurate. This is reflected in the uncertainty
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bounds presented in Table D.12. For this reason, the peaks determined from the FFA more frequent than the 1 in 50 year event have been adopted for this assessment, as indicated in Table D.12 (highlighted green).
D.4.2 Monte Carlo peaks
Monte Carlo peaks for events rarer than the 1 in 1,000 year AEP event have been adopted for this assessment as indicated in Table D.12 (highlighted grey).
D.4.3 Deterministic peaks
Peaks from the deterministic RORB model runs have been adopted as peaks as they provide convenient interpolation points. Deterministic peaks for the 1 in 50 year and 1 in 100 year AEP events have been adopted for this assessment as indicated in Table D.12 (highlighted blue).
D.4.4 Interpolated peaks
To provide reasonable peaks for AEP events between the adopted peaks, it is necessary to interpolate between the results of various techniques. This was achieved by undertaken a log-log interpolation using the adopted 1 in 50 year and 1 in 1000 year AEP events as anchor points. This was found to provide smooth growth curve of flood peaks. The adopted interpolated values are indicated in Table D.12 (highlighted orange).
Table D.12 : Adopted peaks flows from the various methods
Deterministic Peak AEP 1 in Y years Monte Carlo (m3/s) (m3/s) FFA Peak (m3/s) Adopted Peak (m3/s)
5 514 531 329 330 10 651 810 607 610 20 879 1,107 1,027 1,000 50 1,176 1,593 1,895 1,600 100 1,385 2,005 2,886 2,000 200 1,726 2,576 4,278 2,100 500 2,209 3,347 6,970 2,600 1,000 2,755 4,023 9,888 2,800 2,000 3,194 4,747 13,836 3,200 5,000 3,960 5,806 21,190 4,000 10,000 4,592 6,681 28,918 4,600 20,000 5,227 7,731 39,124 5,200 50,000 5,939 9,174 57,668 5,900 100,000 6,553 10,364 76,737 6,600
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D.5 Flood hydrographs Flood hydrographs were generated using the RORB model developed for the catchment and the design inputs outlined above; however, the rainfall temporal pattern and design losses were fixed to produce a deterministic output. The fixed temporal patterns were the ARR87 patterns. The design losses were selected so that the peaks of the hydrographs matched the adopted peaks in Table D.12. The selected losses are listed in Table D.13, with key hydrographs as per Figure D.16.
Table D.13 : Parameters for deterministic hydrograph
Adopted Initial Loss Adopted Continuing RORB peak flow at (mm) Loss (mm/hr) Mole River gauge AEP 1 in Y years Adopted Peak (m3/s) (m3/s)
10 610 20 4.4 620 100 2,000 20 3 2,000 500 2,600 20 5.4 2,600 1,000 2,800 20 6.9 2,810 2,000 3,200 20 8 3,200 5,000 4,000 20 8.85 4,000 10,000 4,600 20 9.8 4,610 20,000 5,200 20 11.3 5,220 50,000 5,900 20 13.9 5,920 100,000 6,600 20 15.7 6,620
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Figure D.16 : Hydrographs at proposed Upper Mole River Dam location.
D.6 Upper Mole River Dam
Details of the Upper Mole River Dam were incorporated into the RORB model to assess the impact of the dam on downstream flood flows. A number of dam configurations were modelled as listed in Section 4.4.
Each dam configuration was incorporated into the RORB model with details for the Storage-Elevation (H-S table) relationship and the Storage-Discharge (S-Q table) relationship. Details are provided in Section 4.4 and Appendix E.
Table D.14 : Proposed dam configurations
Option Spillway length Full Supply Level
L50_S490.5 50m 490.5 m AHD L50_S497.0 50m 497.0 m AHD L50_S502.5 50m 502.5 m AHD L100_S490.5 100m 490.5 m AHD L100_S497.0 100m 497.0 m AHD L100_S502.5 100m 502.5 m AHD L150_S490.5 150m 490.5 m AHD L150_S497.0 150m 497.0 m AHD L150_S502.5 150m 502.5 m AHD
D.6.1 Results
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The resulting peak flows for all configurations are presented in Table D.15 together with the “No dam flow” and “Dam inflow”. The No dam inflow represents the current conditions flow at the dam site for a given AEP, whilst the Dam inflow represents the inflows to the dam. Note that there is an increase in the inflow rate when the dam is in place due to the drowned reach (or full dam) as the pressure wave of the dam fill travels faster than a flood wave.
The results demonstrate that the larger the dam volume and shorter the spillway the greater the reduction in downstream flood peaks. These results indicated the potential flood alleviation benefits of the dam.
Table D.15 : Resulting peak Inflow and Outflow for all dam configurations
No Dam L50_S4 L50_S4 L50_S5 L100_S L100_S L100_S L150_S L150_S L150_S dam AEP Inflow 90.5 97 02.5 490.5 497 502.5 490.5 497 502.5 flow (m3/s) (m3/s) (m3/s) (m3/s) (m3/s) (m3/s) (m3/s) (m3/s) (m3/s) (m3/s) (m3/s)
10 610 650 280 240 220 380 340 310 440 400 380
100 2,000 2,100 1,100 1,000 900 1,500 1,300 1,200 1,600 1,500 1,400
500 2,600 2,700 1,500 1,300 1,200 1,900 1,800 1,700 2,100 2,000 1,900
1000 2,800 3,000 1,600 1,400 1,300 2,100 1,900 1,800 2,300 2,200 2,100
2000 3,200 3,400 1,800 1,700 1,500 2,400 2,200 2,100 2,700 2,500 2,400
5000 4,000 4,200 2,400 2,100 2,000 3,000 2,800 2,700 3,400 3,200 3,000
10000 4,600 4,800 2,800 2,500 2,300 3,600 3,300 3,100 3,900 3,700 3,600
20000 5,200 5,500 3,200 2,900 2,700 4,100 3,800 3,600 4,500 4,300 4,100
50000 5,900 6,200 3,700 3,300 3,100 4,700 4,400 4,100 5,100 4,900 4,700
100000 6,600 6,900 4,100 3,800 3,500 5,300 4,900 4,700 5,700 5,500 5,300
D.7 RORB Model Data
Table D.16 contains the details for each of the RORB sub-catchments
Table D.16 : RORB Subcatchment data
Subcatchment Name Subcatchment Number Area (km2) Impervious Fraction
A 1 33.41 B 2 71.58 C 3 164.14 D 4 170.62 E 5 176.9 F 6 246.75 G 7 255.49 H 8 165.1
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Subcatchment Name Subcatchment Number Area (km2) Impervious Fraction
I 9 170.99 J 10 202.94 K 11 166.45 L 12 190.08 M 13 195.14 N 14 177.64 O 15 165.99 P 16 168.83 Q 17 202.74 R 18 165.26 S 19 252.9 T 20 165.09 2.4% U 21 165.03 V 22 210.82 W 23 156.63 X 24 167.88 Y 25 176.18 Z 26 179.78 AA 27 167.67 AB 28 168.77 AC 29 183.46 AD 30 123.68 AE 31 178.6 AF 32 82.24 AG 33 45.4
The first part of Table D.17 contains the details of the stage (level) storage (volume) relationship for Glenlyon Dam and the second part contains the details of storage discharge relationship.
Table D.17 : Glenlyon Dam data
Level (mAHD) Volume (m3)
365 - 366 9,860 367 108,000 368 187,000 369 266,000
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Level (mAHD) Volume (m3)
370 345,000 371 698,000 372 1,051,000 373 1,404,000 374 1,757,000 375 2,110,000 376 2,952,000 377 3,794,000 378 4,636,000 379 5,478,000 380 6,320,000 381 8,112,000 382 9,904,000 383 11,696,000 384 13,488,000 385 15,280,000 386 18,542,000 387 21,804,000 388 25,066,000 389 28,328,000 390 31,590,000 391 36,802,000 392 42,014,000 393 47,226,000 394 52,438,000 395 57,650,000 396 64,066,000 397 70,482,000 398 78,252,000 399 87,376,000 400 96,500,000 401 106,212,000 402 115,924,000 403 126,440,000 404 137,760,000 405 149,080,000
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Level (mAHD) Volume (m3)
406 162,028,000 407 174,976,000 408 188,888,000 409 203,764,000 410 218,640,000 411 235,712,000 412 252,784,000 413 271,149,000 414 290,509,000 415 310,929,000
Volume (m3) Discharge (m3/s)
248,174,560 0 248,345,280 0.125 250,052,480 2.716 251,759,680 9.324 253,518,600 18.79 255,355,100 30.39 257,191,600 43.17 259,028,100 57.55 260,864,600 73.74 262,701,100 92.14 264,537,600 112.3 266,374,100 133.9 268,210,600 157.2 270,047,100 181.8 271,923,400 208.1 273,859,400 235.7 275,795,400 265.0 277,731,400 295.6 279,667,400 327.9 281,603,400 361.2 283,539,400 395.8 285,475,400 432.1 287,411,400 469.4
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Volume (m3) Discharge (m3/s)
289,347,400 507.7 291,325,800 547.0 293,367,800 587.6 295,409,800 629.6 297,451,800 672.2 299,493,800 716.5 301,535,800 761.8 303,577,800 808.1
Table D.18 contains the details of the rainfall temporal patterns used in the RORB modelling
Table D.18 : Temporal Patterns for design events used in RORB
Duration (hours)
24 48 72 96 120 144 168
3.06 0.32 0 0.15 7.6 3.04 12.44 4.01 5.37 7.01 0 0.76 0.67 2.33 1.43 0.81 9.46 5.95 0 0.13 1.17 3.24 0.49 0.17 0 0 0 7.71 1.39 1.14 0 1.11 0.25 0 6.69 2.04 24.55 0 17.84 0 0 4.44 0.55 5.85 2.82 12.31 0.13 0 0 2.02 0.98 2.98 9.82 0 0 0.56 6.46 0.49 20.39 1.11 0 2.51 1.29 4.72 0.81 7.32 0.55 0.13 0 4.23 0 0.81 7.75 4.98 0 0.72 0.92 2.63 1.79 8.49 0.69 5.44 6.8 1.46 3.42 6.5 8.66 0.55 0 0 7.78 2.43 5.37 0.31 0.41 2.03 0 1.68 4 4.23 0 0 16.2 0 3.07 2.37 3.58 4.29 0.28 11.9 0 0.94 1.52 2.28 7.3 2.49 7.85 0 2.35 5.03 5.85 3.65 0 0.63 0 21.72 2.1 7.48 0.25 2.07 0.51 0 4.48 9.92 1.46 0.7 1.38 4.94 0 13.96 11.72 2.44 1.14 4.43 0.25 0 0.78 6.44 5.2 3.2 8.58 0.63 0
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Duration (hours)
24 48 72 96 120 144 168
13.33 2.44 0 4.01 0.25 4.31 6.17 9.76 4.11 1.8 0 29.87 0.41 0.51 14.79 1.94 2.03 2.49 1.38 0.25 0.36 4.15 1.9 0 5.67 1.01 0.36 4.84 5.06 0.36 0.41 7.85 0 0.69 2.78 2.14 1.9 1.06 0 1.46 1.77 0 1.39 0.71 3.67 0.73 7.22 1.06 2.53 8.71 0.63 8.09 0.72 0.72 1.79 0.36 2.63 0.91 0.71 1.79
Table D.19 contains the details of the rainfall spatial pattern used in the RORB modelling. Each sub-catchment has a value relative to 100, values greater than 100 have high rainfall values and values less than 100 have lower rainfall values.
Table D.19 : Design Spatial Patterns
Subcatchment Name Area (km2) Pattern
H 165.10 113.87 I 170.99 100.49 J 202.94 99.97
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Subcatchment Name Area (km2) Pattern
E 176.90 119.51 D 170.62 108.87 F 246.75 102.37 G 255.49 95.18 C 164.14 95.52 A 33.42 95.51 AC 183.46 95.03 AB 168.77 98.39 AA 167.67 101.48 Z 179.78 97.00 Y 176.18 103.39 X 167.88 99.91 W 156.63 98.21 B 71.58 97.32 AG 45.40 97.55 U 165.03 104.04 V 210.82 93.98 T 165.09 96.16 Q 202.74 103.78 S 252.90 96.90 R 165.26 97.27 P 168.83 98.24 L 190.08 109.88 N 177.64 103.28 K 166.45 99.74 O 165.99 97.52 M 195.14 96.46 AE 178.60 93.01 AF 82.24 94.20 AD 123.68 95.98
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Appendix E. Geology review
The following documents were reviewed: · Preliminary Geological Investigations of the Upper Mole River Site (Water Resources Commission, 1991) · Drawing “Upper Mole River Dam AMTD 39.0km General Arrangement” (Water Resources Commission, 1990) · Reconnaissance for Sources of Construction Material (Water Resources Commission, 1990)
There is limited geological data available for the site. Prior investigations comprised of seismic traverses and test pitting (refer to Figure E.1), with some petrographic analysis. No borehole drilling records are available.
Typically some drilling is performed at feasibility study level and it is recommended that, if this project proceeds to more-detailed investigations, subsurface drilling be undertaken to provide greater certainty on the foundation and materials sources.
Test pits exposed alluvium and soil but were not able to reach the underlying rock. Therefore, the nature of the underlying rock was inferred from outcrops. The available seismic data is of limited value without the presence of correlating boreholes.
E.1 Review summary
The dam site (dam and spillway) is underlain by massive blue grey mudstone or siltstone (called mudstone in this report to be consistent with the original reports). No other rock type was observed near the dam site with the exception of some small porphyritic granitic dykes on the right abutment. The region has been intruded by granitic rocks although at the dam site only the dykes were observed.
Bedding is non-distinct in the mudstone outcrops at the site. However, there are a number of persistent planar joints observed in outcrops at the site. Some of these joints are striated indicating relative movement. This may be tectonic although the possibility of landsliding on the abutments cannot be discounted based on the available information. Either way the presence of continuous planar joints in the abutments, foundation and spillway cut is likely. Given the evidence of striations some of these joints may be at or near residual strength. Although no horizontal continuous joints were reported, rock outcrops were limited and any such structures may not have been exposed.
The report (Water Resources Commission, 1991) notes two sets of joints: · A predominant joint set trending at 200 degrees from true north. This runs at an angle from upstream to downstream from the dam axis and near parallel to the spillway as it is shown in the concept drawings. No mention is made of its dip. · Open joints parallel to the bedding although the bedding is said to be indistinct. These joints dipped sub vertically at a 45 degree trend.
The presence of at least these two sets of joints (there are likely others) being open and persistent suggests a grout curtain below the dam is required and for both dam abutments and the slope cuts in the spillway rock slides are feasible. The sub-vertical set of joints may form a reasonable plane to excavate back to in the spillway cut. Below the dam, the presence of adversely orientated joints is possible although there is insufficient information to assess this.
The possibility of a minor fault in the valley where the dam will be located is also raised due to the presence of fault breccia in outcrop and the seismic traverses. There may need to be some local excavation and foundation treatment if such a feature does exist.
E.2 1990 Concept
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The following observations were made upon review of the 1990 “First Stage” study (Water Resources Commission, 1990) – refer to Appendix K: · The level of geological information is not consistent with a feasibility level study and any costings will reflect this level of knowledge. Further site investigations would be required. · The dam crest is at about 522 metres from the layout provided. It may be possible that the crest could be taken higher given the topography, if greater storage capacity was required. · The spillway is shown as cutting through the top of the hill that forms the left abutment. This appears too close to the embankment. Given that the rock is likely to be highly fractured mudstone, expected erosion resistance would not be high. The failure mode of spillway erosion cutting back to the embankment would have high conditional probabilities if erosion initiated in the spillway. · The existing spillway shows a cut of over 50 metres. Moving the spillway into the gully to the east (or finding another site for the spillway further away from the embankment) would seem logical and reduce the cut if the elevations are suitable. · The spillway (and indeed any spillway) in the highly fractured mudstone would likely require full lining as the rock will be erodible due to closely spaced fracturing.
E.3 Construction materials
The mudstone is of high strength when fresh at the base of the river and also has closely to very closely spaced fractures. Mudstones do not typically form high strength rocks without some form of cementation, or if they have been metamorphosed to form a phyllite. No mention is made of such metamorphism at this site; however given the Silurian Age of the rock this may be possible, and would explain the very high strength. Two of the petrographic samples assessed the mudstone and these indicated characteristics typical of low grade regional metamorphism in the mudstone.
The previous reports do not directly mention utilising the existing rock at the site as a construction material but refer to igneous rocks within one kilometre as potential sources of rock. Based on current knowledge, the mudstone below the dam and spillway is unlikely to be suitable for aggregates, filters or rockfill. There may be an opportunity to reassess this rock for use in RCC aggregates or dirty rockfill as part of further studies.
E.4 Implications on dam design
Closely to very closely spaced fractures in the bedrock suggest joint spacings of no more than 200mm, with the majority being less than 60mm. Hence any rock excavated is likely to be relatively fine, and is likely to breakdown further under handling. The long-term durability of a mudstone under wetting and drying would also be a concern.
There is recent alluvium in the river valley and alluvial terraces and scree deposits on the abutments. These deposits are predominantly sandy. These would need removal for the dam foundations. They are unlikely to be suitable for reuse due to their variable nature. In the river valley alluvium depths were up to 6 metres although there may be locally deeper pockets.
Beneath the dam the seismic refraction velocities suggest that, for a mudstone or siltstone, the rock is fresh to slightly weathered. In the case of an embankment dam there is likely to be minimal rock excavation, unless around specific features such as a fault, shears or preferentially weathered defects. For a concrete dam, the excavation depth may be greater than for an embankment but once again is expected to be relatively minimal. Based on the above assessment, an allowance for rock profiling and dental concrete in the dam foundation should be made.
On both abutments, the seismic traverses and test pits generally indicate less weathered rock within 3 metres. Preferential weathering along joints and other structures may result in pockets of deeper weathering, requiring additional treatment and excavation, particularly for a concrete dam. An allowance for rock profiling and dental concrete should be allowed for both abutments. The potential for historic landslides on the observed joints
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should be assessed and also the potential for open continuous joints from upstream to downstream within the dam abutments.
In the spillway, the seismic traverses suggest soil or highly weathered rock up to 9 metres deep. Soils would likely need to be laid back to slopes in the order of 2.5H:1V and highly weathered rock 2H:1V. For fresh to slightly weathered rock, the slope angles will be dictated by structure in the rock. Near-vertical persistent joints may result in a natural surface being formed at one side. Toppling failures are likely on the other side. There may be other structures not identified that will affect stability. The presence of these is unknown, based on the limited investigation completed to date. In fresh to slightly weathered rock (say below 15 metres depth), steeper slopes (1H:0.3V ) may be possible.
Seismic traverses in the saddle immediately east of the concept spillway suggest a much thinner soil and highly weathered rock profile of up to 3 metres overlying fresh to slightly weathered rock. The presence of a fault or other structure was not identified in the seismic traverses in the saddle. This site appears geologically superior to the current site for a spillway.
The dam will have a rock foundation; hence a concrete/RCC dam could be viable, with an overtopping section. The rock in the investigations, whilst not drilled, was logged as having very high strength at the river. A concrete faced rockfill dam may also work. The issue with both is that the local mudstone is unlikely to be suitable as an aggregate or rockfill. A key consideration for an overtopping dam/spillway is the erodibility of the mudstone rock. Whilst it may be of high strength, the fracturing could likely lead to excessive erosion if not protected. Excessive erosion in a phyllite (metamorphosed mudstone) was seen at the Paradise dam in the 2013 overtopping leading to repairs in excess of $20 million. This dam was commissioned in 2005.
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Figure E.1 : Location of sesmic lines and pits (BRC, 1990)
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Appendix F. Consequence Assessment
In order to determine the design flood for the dam the consequence category of the dam must be assessed an initial assessment was undertaken in accordance with the ANCOLD Guidelines for Consequence Assessment
F.1 Assumptions
· Population at Risk (PAR): ≥ 1 to <10 · Potential Loss of Life (PLL): ≥ 0.1 to <1 · Severity of Damage and Loss: Medium
F.2 Severity
Severity of damage and loss was estimated based on information available at this stage, and is summarised in Table F.1 overleaf.
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Table F.1 : Estimate of Severity of Damage and Loss
Applicant Name - Stream Name Mole River Estimated Capacity at FSL 300 GL Dam ID. No. (If existing dam) - Dam Height (metres) 68 m Location Upper Mole River at "Ringtree" Severity Level s t c i n h e p m r r m o u Damage and Loss Estimate o o i j r n t m i d a s o e M M a t C M a C
B1 TOTAL INFRASTRUCTURE COSTS Residential <$10M YES . . . There are very few houses in the floodpath
Commercial $10M-$100M . YES . . Agricultural machinery and outbuildings
Community Infrastructure $10M-$100M . YES . . Roads, irrigation supply would be affected
Dam repair or replacement cost $10M-$100M . YES . . Approximately 1/3 of white water demand
Total Infrastructure cost severity level MEDIUM
B2 IMPACT ON DAM OWNER'S BUSINESS Without the storage the system reverts to current Importance of the system, need to replace the dam Restrictions needed during peak days and peak hours . YES . . operations with reduced reliability Reduced services are possible with reasonable Without the storage the system reverts to current Effect on services provided by owner . YES . . restrictions levels of service with reduced reliability Effect on continuing credibility Some reaction but short lived YES . . . Credibility damage would be localised
Community reaction and political implications Some reaction but short lived YES . . . Community reaction would be localised Assume that operating authority would be assisted by Impact on financial viability Significant with considerable impact . YES . . State and Federal governments Could be absorbed in one year with governmental Value of water in the storage Loss of income for at least 1 year . YES . . assistance Impact on dam owner' business severity level MEDIUM
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B3 HEALTH AND SOCIAL IMPACTS Human health < 100 people affected YES . . . No drinking water to contaminate No life critical items would be forgotten due to strong Loss of services to the community < 100 people affected YES . . . fire pribase leadership Cost of emergency management < 1,000 person days YES . . . Judgement
Dislocation of people < 100 person months YES . . .
Dislocation of businesses 20 to 200 business months YES . . Some impact on ecosystems
Employment affected 100 to 1000 jobs lost . YES . . <100 jobs lost in catchment
Loss of heritage Local facility YES . . . Local facility
Loss of recreational facility Local facility YES . . . Local facility Health and Social severity level MEDIUM B4 ENVIRONMENTAL IMPACTS Area of impact 1km² to < 5km² . YES . . <5 km square area above land prone to flooding
Duration of impact 1 year to 5 years . YES . . <1 year resilient catchment Discharge from dambreak would not contaminate water Stock and fauna YES . . . No contamination to water supplies supplies used by stcok and fauna Discharge from dambreak is not expected to impact on Ecosystems YES . . At least one wet season ecosystems. Remediation possible Species exist but minimal damage expected. Recovery Rare and endangered species YES . . . None identified within one year Environmental impacts severity level MEDIUM
Highest severity level MEDIUM
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Reasons for recommending a consequence category (refer ANCOLD Guidelines On The Consequence Categories For Dams October 2012) MUST include comments on the PAR (both permanent and itinerant), buildings, roads, other infrastructure and the natural environment downstream of the dam and the potential impacts arising from a dam break: (** Note** Provide photographs to support reasons for recommending consequence category)
Population at Risk (PAR) CONSEQUENCE CATEGORY =
PAR includes all those persons who would be directly exposed to flood waters within the dam break affected zone if they Significant (Note 2) took no action to evacuate
Note 1: With a PAR in excess of 100, it is unlikely damage will be minor, similarly with a PAR in excess of 1,000 it is unlikely damage will be classified as medium
Note 2: Change to 'High C' where there is a potential of one or more lives being lost
Completed By Date
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F.3 Consequence Assessment According to NSW Dam Safety Committee Guideline DSC3A, Section 5.2:
“Where potential loss of life (PLL) figures have not yet been estimated, an owner can base a tentative consequence category on PAR as in Table 2 of this sheet.”
Therefore, the consequence category of Upper Mole River Dam at this feasibility stage was determined as “Significant” and, based on the NSW Dam Safety Committee Guideline DSC3B, the accepted flood capacity was determined as the “outflow of 1 in 10,000 AEP flood”.
According to DSC3B, Table 5.1:
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Appendix G. Flood capacity and spillway design
G.1 Selection of acceptable flood capacity
For a hazard category of “Significant”, ANCOLD Guidelines on Selection of an Acceptable Flood Capacity for Dams (2000) states that the required fallback flood capacity is the 10-3 to 10-4AEP. New South Wales Dams Safety Committee guideline DSC3B, “Acceptable Flood Capacity for Dams, recommends the conservative end of the ANCOLD Guidelines. It should be noted that the recommended floods are outflow floods.
With regard to the above guidelines, the 10-4 AEP flood was selected as the accepted flood capacity for the Upper Mole River Dam.
The Dam Crest Flood (DCF) is determined based on the flood frequency curves below:
Figure G.1 : Flood Frequency Curve-FSL 490.5 mAHD
Figure G.1 above indicates that the inflow Dam Crest Flood (DCF) has Annual Exceedance Probability (AEP) between 1 in 100,000 and 1 in 200,000 years for various full supply levels.
G.2 Layout
The main criteria which govern the position of the spillway are the dam type, morphology of the site, geology and spillway length.
At the Upper Mole River site, due to the morphology of the river creating a bend downstream of the embankment, the spillway layout is selected at the left abutment.
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Review of the existing geological information for the dam and spillway site suggests that the saddle immediately east of the current spillway location appears geologically superior to the current spillway location.
G.3 Spillway length
The preferred configuration of spillway is a single uncontrolled ogee crest spillway, for a variety of reasons, including: · Reduced operational risks associated with gated spillway in a remote area · Reduced operational risks associated with additional secondary fuse-plug embankment · Low long-term maintenance costs in comparison with gated spillway · Provision of passage of debris
The spillway length is estimated for a range of dam crest elevation for all three FSL. Results are presented in Table G.1 below:
Table G.1 : Spillway Length Calculations
Spillway Length Dam Crest FSL (mAHD) (m) (mAHD) 12m Freeboard 473.0 59.0 485.0
483.0 59.0 495.0
490.5 59.0 502.5
10m Freeboard 473.0 483.0 80.0 483.0 493.0 80.0 490.5 500.5 80.0 8.5m Freeboard 473.0 481.5 105.0 483.0 491.5 105.0 490.5 499.0 105.0
Given that the rock is likely to be highly fractured, the spillway would require full lining as the rock is expected to be highly erodible.
Comparing the high cost of excavation and concrete lining the chute with the cost resulting from the raising the rockfill dam crest, also the risks associated with the construction of a concrete chute on a highly fractured bedrock, It is likely the narrower spillway would be the most cost effective option.
As a result, the 59m wide spillway and the dam crest option with12m freeboard on FSL is selected at this stage. However, to determine the most cost effective combination of spillway length and dam crest elevation, it is required to optimise the spillway length\costs versus the rockfill dam height\cost in future studies.
Flood routing calculations were carried out using an in-house developed spreadsheet employing forward difference algorithms to determine the outflow based on the hydrograph inflows. Spillway outflow in any
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particular time step is determined by the water elevation in the reservoir. The in-house calculations were validated using identical simulations in RORB software. The initial reservoir level is assumed at FSL.
The flood routing results for 10,000 AEP and 100 AEP flood events at various FSL are presented in Table G.2 below:
Table G.2 : Flood Routing Results
10,000 AEP Flood 1000 AEP Flood
Inflow Outflow Max Res. FSL (mAHD) Inflow Outflow Max Res. Water (m3/s) (m3/s) Water Level (m3/s) (m3/s) Level (mAHD) (mAHD)
473.0 4800 2,950 481.3 2800 1,658 478.8
483.0 4800 2,392 490.3 2800 1,298 488.0
490.5 4800 2,043 497.1 2800 1,084 494.9
G.3.1 Freeboard
Freeboard for embankment dams should include prevention of any overtopping of the dam by either frequent or infrequent high waves that might interfere with efficient operation of the project, create conditions hazardous to personnel, causes other adverse effects not necessarily associated with the general safety of the structure, or cause a dam breach and failure.
Appropriate freeboard is required to minimize the potential for dam overtopping and failure from wind-generated wave action.
New South Wales Dams Safety Committee guideline DSC3B, “Acceptable Flood Capacity for Dams, recommends the minimum freeboard of 0.3 m for embankment dams. This criteria is compared with the USBR DS-13(6)-2 September 2012 guideline on Embankment Dams-Freeboard.
The table below shows the calculations that are usually performed to derive the minimum and normal freeboard for new dams based on USBR DS-13(6)-2:
Type of Freeboard Approach to Freeboard Analysis
Minimum Select a design crest elevation the higher of: · MWRS + 3 feet (approx. 1m) · MRWS + runup and setup from a wind velocity exceeded 10% of the time Normal NRWS + runup and setup from a 100-mile-per-hour wind velocity (44.7 m/s)
Note: MRWS = maximum reservoir water surface, NRWS = normal reservoir water surface, IDF = inflow design flood.
In absence of wind probability curves, only the first criterion of minimum freeboard is compared with normal freeboard at this stage.
Minimum freeboard, normal freeboard and selected dam crest for all three FSL and 59m wide spillway are shown in Table G.3.
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Table G.3 : Dam Crest Selection
FSL (mAHD) 473.0 483.0 490.5
Minimum Freeboard(m) 1.0 1.0 1.0
Normal Freeboard(m) 2.14 2.20 2.27
MWRS (mAHD) in 10,000 AEP-Outflow 484.0 494.0 501.5
Dam Crest Resulting From Minimum Freeboard (mAHD) 485.0 495.0 502.5
Dam Crest Resulting From Normal Freeboard (mAHD) 475.1 485.2 492.8
Minimum Dam Crest based on DSC3B (mAHD) 473.3 483.3 490.8
Selected Dam Crest 485.0 495.0 502.5
G.3.2 Spillway Components
G.3.2.1 Spillway approach channel
The approach channel is sized to maintain low design approach velocities and head losses upstream of the ogee weir. Similarly, approach transitions are gradual to minimise flow disturbances and contraction losses.
The approach channel consist a straight 70m wide channel with 12m depth below the FSL and length between 175m to 212m in various FSL. The maximum flow velocity within the approach channel in 10,000 AEP flood event is calculated 2.7 m/s. With the available level of geological information regarding the bed rock, this velocity is considered appropriate at this stage.
The approach channel floor has a 1V:200H grade to allow drainage away from the ogee weir under low reservoir conditions.
G.3.2.2 Ogee Crest, Chute and Terminal Structure
The upstream control structure is an ogee shaped weir, which is commonly used on dam spillways around the world. The weir is nominally 59 m wide with crest level at FSL.
Supercritical flow is maintained once flow passes the crest as the downstream chute has adequate slope to ensure this.
The slope of the chute is defined due to the topography condition in order to reduce the excavation volumes.
As the 59m wide chute is situated in the highly fractured mudstone and the rock will likely be erodible due to closely spaced fracturing, the total 290m of the chute length is fully lined.
The chute walls are determined to pass the 1000 AEP flood with sufficient freeboard in comparison with the water surface profile for 10,000 AEP flood. The height of the walls varies from 3m to 2.5 m along the chute.
The dissipation of energy at the termination of the chute will be achieved with a flip bucket and plunge pool.
The flip bucket terminates the chute in a large radius curve that throws the water in trajectory shape downstream.
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Energy is dissipated as the flow jet breaks up in the air and as it enters the plunge pool downstream. The flip bucket design is considered to be the most economical type energy dissipator commonly used in spillway design.
Unless the jet impact area is located in extremely durable rock, a scour hole can be expected to occur at the impact point. In design process the following items are considered: · The toe of the dam is not eroded. · The slopes of the valley are stable and no slides will occur due to spray of the jet.
The plunge pool comprises a trapezoidal unlined pool downstream of the spillway and flip bucket. The base of the pool is approximately 50 m long by 80 m wide and excavated 20-25 m into the sound bed rock based on the current assumption of 10m depth of the weathered rock at spillway location. At the downstream end of the pool the channel invert rises back to river level. To identify the location that scour is likely to occur and the extent of pre-excavation of a plunge pool that will provide the most benefit, it is necessary to predict the trajectory of the jet from the flip bucket during a range of design flows. The Kawakami (1973) and USBR recommended method are compared and adopted for calculating trajectories of a free jet from the spillway.
The likelihood and extents of scour have been estimated using a variety of empirical methods. Some of these methods consider the strength of the rock (Annandale 1995, Van Schalkwyk 1994, Khatsuria 2005), while others do not (Mason 1985, USBR 1987, Yildiz & Uzucek 1994, Damle 1966, Chian Min Wu 1973, and Martins 1975, modified Veronese.
A physical model study would be helpful to determine the geometry of the flip bucket and extents of scour within the plunge pool.
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Appendix H. Environmental desktop assessment
H.1 Background Jacobs Group (Australia) Pty Ltd (Jacobs) was engaged by Water NSW to prepare a feasibility study to support the Expression of Interest (EOI) submission required by the NSW Government to apply for capital funding for a Mole River Dam under the National Water Infrastructure Development Fund (NWIDF).
H.2 Location The proposed location for the major water storage area is in the upper reaches of the Mole River in New South Wales (Figure H.1). Mole River is one of the Border Rivers and part of the Macintyre Catchment within the Murray Darling Basin, Northland Tablelands. Mole River is located within the Tenterfield Shire Local Government Area (LGA) and lies approximately 200km south west of Brisbane, Queensland. A disused arsenic mine is located downstream of the storage, and a tin mine is located along a tributary of the storage, Pyes Creek.
For the purposes of this assessment, several geographical extents were examined as part of the proposal (Appendix J). These extents are stated throughout the report and defined as:
· 100 GL capacity – inundation area of 775.26 hectares · 200 GL capacity – inundation area of 1180.8 hectares · 300 GL capacity – inundation area of 1440.63 hectares · Study area – area within a 100m buffer around the 300 GL inundation area (2022 hectares).
H.3 Aims and scope of review This report relates specifically to an assessment of potential environmental constraints within the proposed major water storage area of the Upper Mole River, including:
· Biodiversity · Contaminated lands · Water Quality · Heritage The aim of this report is to present all available data to identify and assess key values / constraints at the site. All work detailed within this report was based on desktop assessments and no site visits were undertaken. This is a preliminary assessment of site constraints and further work is required to adequately assess the full extent of impacts associated with the proposal.
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H.4 Biodiversity
H.4.1 Methods For the purposes of this assessment, several geographical extents were examined as part of the proposal. These extents are stated throughout the report and defined as:
· 100 GL capacity – inundation area of 775.26 hectares · 200 GL capacity – inundation area of 1180.8 hectares · 300 GL capacity – inundation area of 1140.63 hectares · Study area – area within a 100m buffer around the 300 GL inundation area (2022 hectares)
H.4.1.1 Literature and database review A background review was carried out, including database searches of the locality, encompassing a 10 kilometre radius from the study area (i.e. searches of the locality). This included searches of the following databases:
· Office of Environment and Heritage (OEH) Atlas of NSW Wildlife (10 kilometre search radius around the study area). · Department of Environment (DoE) Protected Matters Search Tool (a 0.5 kilometre buffer was used to ensure results applied to the study area as this tool is based on modelled habitat and not actual records). · PlantNET search tool for Rare or Threatened Australian Plant (RoTAP) species. · BRG-Namoi Regional Native Vegetation Mapping (Office of Heritage and Environment, 2015). · Fish Communities and Threatened Species Distributions of NSW (DPI, 2016). Literature relevant to the study area was also reviewed, and included the following:
· Preliminary Environmental Assessment (PEA) of Additional Water Supply Options Mole River and Severn River Dam Sites , NSW Department of Water Resources (NSW Department of Water Resources, 1990) · Nandewar biodiversity surrogates: vertebrate fauna (Andren, 2004). The database searches focused on identifying and listing the threatened flora and fauna species, populations and ecological communities previously recorded within the locality. Following collation of database records and species/community profiles, a ‘likelihood of occurrence’ assessment (Section H.10) was undertaken with reference to the broad habitats contained within the study area as identified by the desktop study.
H.4.1.2 Threatened species assessment State and nationally listed threatened species identified from the background reviews were considered in terms of their likelihood to occur in the habitats present within the study area based on their identified habitat requirements and matched to the habitats identified from the background searches. A ‘preliminary’ likelihood of occurrence of threatened species was determined according to the criteria described in Table H.1 and formed by records and/or habitat known or assumed to be present based on vegetation mapping. In undertaking this task, the precautionary principle was applied in an effort to mitigate this constraint. A flora and fauna survey would be required at a later stage to confirm the likelihood of occurrence. The full list of species identified from database searches and their ‘preliminary’ likelihood of occurrence are shown in H.10. Limitations of the assessment process are discussed in H.4.3.3.
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Figure H.2 : Native vegetation within study area - PCT database
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Figure H.3 : Native vegetation within study area - TSC Act
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Table H.1 : Likelihood of occurrence criteria for threatened species
Likelihood of Criteria occurrence Unlikely Species not recorded during field surveys and fit one or more of the following criteria: · Species highly restricted to certain geographical areas not within the study area · Species with specific habitat requirements that are not present in the study area. Low Species considered to have a low likelihood of occurrence in the study area fit one or more of the following criteria: · Have not been recorded previously in the study area/locality and for which the study area is beyond the current distribution range. · Have been recorded sporadically in the locality in the past but are considered a low likelihood to use the study area as habitat due to the absence of any high quality habitat features upon which the species depends. · Use specific habitats or resources not present in the study area. Moderate Species that fit one or more of the following criteria are considered to have a moderate likelihood of occurrence: · Have frequently been recorded in the study area/locality and are known to be present in the locality. · Are known to use specific habitats or resources that are present in the study area. · Species that are unlikely to maintain sedentary populations however may seasonally use resources within the study area opportunistically or during migration if the habitat is good quality. High Species that fit one or more of the following criteria are considered to have a high likelihood of occurrence: · Have frequently been recorded in the study area/surrounds. · Use habitat types or resources that are present in the study area and/or the habitats in the study area are in good condition. · Are known or likely to maintain resident populations in the study area. · Are known or likely to visit the site during regular seasonal movements or migration due to the presence of high quality habitats. Present A species known to occur in the study area based off high quality recent records (within the last 20 years) of high accuracy.
H.4.2 2.2 Results
H.4.2.1 Landscape context The study area is located in the New England Tableland Bioregion, with the eastern half in the Tenterfield Plateau sub-region and the western half in the Nandewar Northern Complex sub-region (Thackway & Cresswell, 1995). The study area is contained predominately within the Mole Valley Mitchell Landscape; however parts of the inundation area also enter into the Ashford Mole Valleys and Inverell Plateau Granites Mitchell Landscapes (Mitchell, 2002).
The study area has largely been cleared of the naturally occurring vegetation and is now characterised by extensive areas of agricultural land, both pasture and grazing, with patches of remnant and regenerating vegetation.
H.4.2.2 Native vegetation and fauna habitat
Native vegetation A review of aerial photography and available vegetation mapping (Office of Heritage and Environment, 2015) shows that the study area is largely composed of cleared agricultural land. Vegetation on the valley floor is almost totally absent (save riparian remnants) and some areas around the rivers banks have been replaced by improved pasture. The lower slopes are cleared to partially cleared, with remnant vegetation persisting in steeper areas higher up.
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The Mole River is lined by riparian vegetation, most likely of remnant nature. The PEA (NSW Department of Water Resources, 1990) lists the dominant species as mature River Oak (Casuarina cunninghamiana), Red Gum (Eucalyptus dealbata), River Red Gum (Eucalyptus camaldulensis), Melaleuca and Acacia species, with occasions of introduced species such as Willows (Salix sp.) and Peppercorn trees (Schinus sp.). The normally dense understorey has been replaced by a mixture of native and exotic grasses. This aligns with vegetation mapping (OEH 2015) that shows Plant Community Type (PCT) River Oak - Rough-barked Apple - red gum - box riparian tall woodland (wetland) of the Brigalow Belt South Bioregion and Nandewar Bioregion lining the bank of the river.
The alluvial floodplain and lower slopes can be seen from aerial imagery as containing variable amounts of scattered trees, a product of a history of disturbance. Based on the species reported in the PEA (DWR 1990) and local vegetation mapping and elevation, the vegetation communities present prior to clearing were likely a mixture of the grassy dry sclerophyll forests shown in Table H.2. Much of these areas have now been mapped as ‘Candidate Native Grasslands’ (Office of Heritage and Environment, 2015).
The upper slopes and steep hills of the study area contain significant remnants of native woodland. The PEA (NSW Department of Water Resources, 1990) lists dominant species as Broad-leaved Red Ironbark (Eucalyptus fibrosa), Silver-leaved Ironbark (Eucalyptus melanophloia), Grey Box (Eucalyptus moluccana), White Cypress Pine (Callitris columellaris), Black Cypress Pine (Callitris endlicheri), and Acacia species. Table H.2 lists the vegetation communities that are likely to occur within the study area based on regional vegetation mapping (Office of Heritage and Environment, 2015).
Table H.2 : PCT and legal status of mapped vegetation communities within the study area. Associated with Extent (ha) within a threatened Plant Community Type (PCT) study area* ecological community? River Oak - Rough-barked Apple - red gum - box riparian tall woodland (wetland) of the Brigalow Belt South Bioregion and Nandewar Bioregion (PCT ID 84) 491.79 No Grey Box grassy woodland or open forest of the Nandewar Bioregion and New England Tableland Bioregion (PCT ID 516) 5.63 No Grey Box shrubby open forest of northern parts of the Nandewar Bioregion and New England Tableland Bioregion (PCT ID 517) 69.59 No
Rough-barked Apple - White Cypress Pine - Blakely's Red Gum riparian open forest / woodland TSC Act and 1.23 of the Nandewar Bioregion and New England Tableland Bioregion (PCT ID 544) EPBC Act Wild Quince - Mock Olive - Rusty Fig - Iamboto - Sweet Pittosporum dry rainforest of rocky and TSC Act and 12.46 scree areas of the Nandewar Bioregion and New England Tableland Bioregion (PCT ID 547) EPBC Act Silver-leaved Ironbark - Black Cypress Pine +/- White Box shrubby open forest mainly in the northern Nandewar Bioregion (PCT ID 549) 578.54 No Tumbledown Red Gum - White Cypress Pine - Caley's Ironbark shrubby open forest of the Nandewar Bioregion and western New England Tableland Bioregion (PCT ID 562) 7.4 No
White Box - Silvertop Stringybark +/- White Cypress Pine grass shrub open forest of the southern TSC Act and 11.05 Nandewar Bioregion and New England Tablelands Bioregion (PCT ID 563) EPBC Act White Cypress Pine - Silver-leaved Ironbark - Caley's Ironbark open forest of the central Nandewar Bioregion and western New England Tableland Bioregion (PCT ID 564) 16.79 No Silver-leaved Ironbark - White Cypress Pine shrubby open forest of Brigalow Belt South Bioregion and Nandewar Bioregion (PCT ID 594) 177.25 No Tumbledown Red Gum - White Cypress Pine - Silver-leaved Ironbark shrubby woodland mainly in the northern Nandewar Bioregion (PCT ID 594) 1085.12 No
Blakely's Red Gum - Yellow Box grassy tall woodland on flats and hills in the Brigalow Belt South 34.08 TSC Act and
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Associated with Extent (ha) within a threatened Plant Community Type (PCT) study area* ecological community? Bioregion and Nandewar Bioregion (PCT ID 599) EPBC Act
Potentially Candidate Native Grasslands 2953.68 EPBC Act Not native (cleared land) 676.65 No *Calculations based on vegetation mapping (OEH 2015)
Fauna habitat Corresponding with the loss of native vegetation from the study area, the diversity and abundance of native fauna has likely reduced dramatically since European colonisation. The original fauna of the study area would have included a wide range of frogs, reptiles, birds and ground-dwelling and arboreal mammals including insectivorous and nectarivorous bats. Fauna habitat in the study area is now highly modified and limited with few areas that provide sufficient habitat for a high diversity of native fauna.
Areas of native vegetation in the study area are likely to provide habitat for a range of general fauna species. However much of the remnant vegetation has been subject to a history of disturbance and modification that has caused the removal of habitat features such as large dead trees and woody debris. As such habitat value through such areas may be low, however this should be appropriately determined during a site visit.
The highest areas of habitat value are likely to be the areas of remnant vegetation on the upper slopes. Much of these areas are also likely to be connected to larger patches of similar vegetation, forming habitat connectivity across the landscape facilitating fauna species that have large patch size requirements.
Fauna corridors Corridors are links in wildlife habitat composed (generally) of native vegetation that connects two or more larger areas of similar habitat. Based on regional fauna corridor mapping (Scotts, 2003); (Andren, 2004), the study area contains one ‘regional corridor’ and several potential ‘sub-regional corridors’. The regional corridor (known as “Pyes-ck”) is approximately 1.1 kilometres wide and dissects the centre of the study area in a north-south direction.
The “Mole River – Tenterfield Plateau” region has also been identified as a wildlife corridor for climate change. The Mole River – Tenterfield Plateau corridor extends east from the Bebo – Bonshaw corridor at Watsons Crossing. The corridor complex contains multiple arms that extend and link to the “Torrington” and “Torrington – Bolivia Hill” to the south, and Timbarra Plateau and Boonoo Boonoo – Bald Rock in the east (DECC, 2007a).
H.4.2.3 Aquatic ecology and habitats The Mole River is a seventh order stream (Strahler) that is one of the Border Rivers and part of the Macintyre catchment within the Murray–Darling basin. The Mole River is a tributary of the Dumaresq River (also seventh order), joining 44 kilometres North West of the proposed dam wall site. The Mole River may offer shelter, foraging and breeding habitat for a range of fauna, including amphibians, reptiles, fish and water birds as well as micro- and macro-invertebrates.
Within the study area, the Mole River has extensive history of disturbance from agricultural activities. The condition of remnant riparian vegetation around the river is unknown; however it is likely to be a highly modified version of the communities that were once lining the river. The lack of riparian vegetation and the history of agriculture and cattle grazing are likely to have increased erosion and slip throughout the study area, as well as impacted the water quality. It is likely that the watercourses within the study area are highly disturbed, with low- moderate water quality and supporting a potentially depauperate aquatic community.
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H.4.2.4 Threatened ecological communities
TSC Act listed ecological communities According to available vegetation mapping, no listed threatened ecological communities are likely to occur within the study area. However, based on a review of the profiles of the previously listed PCTs in the VIS Classification 2.1 database, one endangered ecological community listed under the TSC Act may be present in the study area (see Table H.3).
Table H.3 : TSC Act Threatened Ecological Communities potentially occurring in the study area
Plant Community Type (PCT) Threatened ecological community Status Extent (ha) within (TSC Act) study area* Rough-barked Apple - White Cypress Pine - Blakely's Red Gum riparian open forest / woodland of the Nandewar Bioregion and New England Tableland Bioregion (PCT ID 544) White Box - Silvertop Stringybark +/- White Cypress Endangered Pine grass shrub open forest of the southern White Box Yellow Box Blakely’s Ecological 34.08 Nandewar Bioregion and New England Tablelands Red Gum Woodland Community Bioregion (PCT ID 563) Blakely's Red Gum - Yellow Box grassy tall woodland on flats and hills in the Brigalow Belt South Bioregion and Nandewar Bioregion (PCT ID 599) Wild Quince - Mock Olive - Rusty Fig - Iamboto - Endangered Sweet Pittosporum dry rainforest of rocky and scree Semi-evergreen Vine Thicket in Ecological 12.46 areas of the Nandewar Bioregion and New England the Brigalow Belt South and Community Tableland Bioregion (PCT ID 547) Nandewar Bioregions
*Calculations based on vegetation mapping (OEH 2015)
Environment Protection and Biodiversity Conservation Act, 1999 According to the results of the Protected Matters Search Tool (PMST) (which are based on modelling), four threatened ecological communities listed under the EPBC Act may occur within the study area these include:
· Natural grasslands on basalt and fine-textured alluvial plains of northern New South Wales and southern Queensland. · New England Peppermint (Eucalyptus nova-anglica) Grassy Woodlands · Weeping Myall Woodlands · White Box-Yellow Box-Blakely's Red Gum Grassy Woodland and Derived Native Grassland It is unlikely that all of these threatened ecological communities occur in the study area. Based on mapped PCTs within the study area, at least two TECs listed under the EPBC Act may be present on the site (Table H.4).
Table H.4 : EPBC Act Threatened Ecological Communities potentially occurring in the study area
Plant Community Type (PCT) Threatened ecological community Status Extent (ha) within (EPBC Act) study area Rough-barked Apple - White Cypress Pine - Blakely's Red Gum riparian open forest / woodland White Box-Yellow Box-Blakely's Critically 34.08 of the Nandewar Bioregion and New England Red Gum Grassy Woodland and Endangered Tableland Bioregion (PCT ID 544) Derived Native Grassland
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Plant Community Type (PCT) Threatened ecological community Status Extent (ha) within (EPBC Act) study area White Box - Silvertop Stringybark +/- White Cypress Pine grass shrub open forest of the southern Nandewar Bioregion and New England Tablelands Bioregion (PCT ID 563) Blakely's Red Gum - Yellow Box grassy tall woodland on flats and hills in the Brigalow Belt South Bioregion and Nandewar Bioregion (PCT ID 599)
White Box-Yellow Box-Blakely's Critically Candidate Native Grasslands 2953.68 Red Gum Grassy Woodland and Endangered Derived Native Grassland Wild Quince - Mock Olive - Rusty Fig - Iamboto - Semi-evergreen vine thickets of Sweet Pittosporum dry rainforest of rocky and scree the Brigalow Belt (North and Endangered 12.46 areas of the Nandewar Bioregion and New England South) and Nandewar Tableland Bioregion (PCT ID 547) Bioregions *Calculations based on vegetation mapping (OEH 2015)
White Box-Yellow Box-Blakely's Red Gum Grassy Woodland and Derived Native Grassland Three mapped PCTs within the study area are known to be associated with the EPBC Act listed Critically Endangered Ecological Community (CEEC) White Box-Yellow Box-Blakely's Red Gum Grassy Woodland and Derived Native Grassland. However, if these PCTs are confirmed to be present, field based condition thresholds is required to positively determine if they meet the criteria for the EPBC Act listing.
The condition thresholds detailed in the National Recovery Plan for White Box-Yellow Box-Blakely's Red Gum Grassy Woodland and Derived Native Grassland (DECC, 2010) are intended to function as a set of criteria that assists in identifying when the EPBC Act is likely to apply to an ecological community. They provide guidance for when a patch of a threatened ecological community retains sufficient conservation values to be considered as a Matter of National Environmental Significance (MNES), as defined under the EPBC Act. This means that the protection provisions of the EPBC Act are focussed on the most valuable elements of Australia’s natural environment, while heavily degraded patches, which do not trigger the “significance test” of the EPBC Act will be largely excluded.
There is also the potential for cleared grassy areas that were once vegetated by White Box - White Cypress Pine - Silver-leaved Ironbark shrubby open forest of the Nandewar Bioregion to be a Derived Native Grassland (DNG) version of this TEC. (Office of Heritage and Environment, 2015) have mapped extensive areas within the study area as ‘Candidate Native Grasslands’, which may fall under the EPBC Act listing. DNGs are also subject to condition threshold assessments and are not able to be identified by a desktop assessment.
If patches of the vegetation communities are identified within the study area and are deemed to meet the condition thresholds listed under the EPBC Act, then further work is required to assess the significance of impacts. Vegetation diagnostic investigations are recommended using on-ground assessment of the understorey as well as tree cover following the BioBanking Assessment Methodology (Office of Environment and Heritage, 2014).
Semi-evergreen vine thickets of the Brigalow Belt (North and South) and Nandewar Bioregions One mapped PCT within the study area, Wild Quince - Mock Olive - Rusty Fig - Iamboto - Sweet Pittosporum dry rainforest (PCT ID 547), is known to be associated with the EPBC Act listed Critically Endangered Ecological Community (CEEC) Semi-evergreen vine thickets of the Brigalow Belt (North and South) and Nandewar Bioregions. If present, this TEC would be part of the Southern semi-evergreen vine thicket ('southern SEVT') vegetation association. There are no listed condition thresholds for this TEC. If PCT 547 is confirmed to be present, then it will come under the EPBC Act TEC listing.
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H.4.2.5 Threatened flora species A review of threatened flora databases returned the following results:
· According to the results of the PMST (which are based on habitat modelling), 18 threatened plants could occur in the study area. Twelve of these species are classed as ‘species or species habitat likely occur within area’. Six of these species are classed as ‘species or species habitat may occur within area’. · The database search results (OEH Atlas) did not return any records of threatened flora within a 10 km radius of the study area. Based on a ‘preliminary’ likelihood of occurrence assessment, the 15 threatened flora species listed in Table H.5 are considered moderately likely to occur in the study area based on the presence of suitable habitat. Field surveys are required to confirm the presence or absence of these plants and available habitat from the site.
Table H.5 : Threatened flora species with a 'preliminary' moderate likelihood of occurring in the study area
Species name Common name Status
EPBC Act TSC Act
Acacia macnuttiana McNutt's Wattle V V Acacia pubifolia Velvet Wattle V E Boronia granitica Granite Boronia E V Cadellia pentastylis Ooline V V Dichanthium setosum Bluegrass V V Diuris pedunculata Small Snake Orchid E E Eucalyptus caleyi subsp. ovendenii Ovenden's Ironbark V V Eucalyptus nicholii Narrow-leaved Black Peppermint V V Grevillea beadleana Beadle’s Grevillea E E Lepidium peregrinum Wandering Pepper-cress E E Prasophyllum petilum Tarengo Leek Orchid E E Prasophyllum sp. Wybong (C.Phelps ORG 5269) CE - Rutidosis heterogama Heath Wrinklewort V V Thesium australe Austral Toadflax V V Tylophora linearis E V
H.4.2.6 Threatened fauna A review of threatened fauna databases returned the following results:
· According to the results of the PMST (which are based on habitat modelling), seven birds, eight mammals, four reptiles and one fish could occur in the study area. · The database search results (OEH Atlas) indicate that there have been 23 threatened fauna species recorded in the locality in the past including 13 birds, 6 mammals, and two reptiles. There are no records of threatened fauna within the study area. No endangered populations are known from the locality. The study area is located within the Mole River - Tenterfield Plateau Corridor (DECC 2007). This corridor contains significant areas of key habitat for the Mole River fauna sub-region (Andren 2004). Approximately 4780ha of key habitat for Threatened species or species of conservation concern is mapped within the corridor.
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This fauna connectivity corridor likely contains suitable habitat for a large range of threatened fauna species including many woodland birds, mammals and bats. Andren (2004) compiled a list of threatened fauna species listed under the TSC Act that are known (12), likely (2) or potentially occurring (14) in the Nandewar key habitat for the fauna sub-region, Mole River.
Although no records of threatened species exist within the site, there may be potential for some species to occur in the study area that are known from the locality. Table H.6 lists the 27 threatened fauna species that are considered moderately likely to occur in the study area based on nearby records and mapped habitat. As no site visit has been undertaken, this is considered a ‘preliminary’ likelihood of occurrence only. These species would need to be targeted in field surveys during an impact assessment.
Table H.6 : Threatened fauna species with a 'preliminary' moderate likelihood of occurring in the study area
Status No. records in Species name Common name locality (Atlas EPBC Act TSC Act data)
Birds Anthochaera phrygia Regent Honeyeater CE CE 0 Artamus cyanopterus cyanopterus Dusky Woodswallow - V 3 Calyptorhynchus lathami Glossy-black Cockatoo - V 7 Chthonicola sagittata Speckled Warbler - V 3 Climacteris picumnus victoriae Brown Treecreeper - V 11 Daphoenositta chrysoptera Varied Sittella - V 1 Geophaps scripta Squatter Pigeon V E 0 Glossopsitta pusilla Little Lorikeet - V 6 Grantiella picta Painted Honeyeater V V 0 Lathamus discolor Swift Parrot E E 0 Melanodryas cucullata cucullata Hooded Robin - V 5 Neophema pulchella Turquoise Parrot - V 15 Ninox strenua Powerful Owl - V 1 Pomatostomus temporalis temporalis Grey-crowned Babbler - V 8 Stagonopleura guttata Diamond Firetail - V 10 Mammals Chalinolobus dwyeri Large-eared Pied Bat V V 0 Dasyurus maculatus Spotted-tailed Quoll E V 14 Miniopterus schreibersii oceanensis Eastern Bentwing-bat - V 17 Nyctophilus corbeni Corben’s Long-eared Bat V V 2 Petauroides Volans Greater Glider V - 0 Petrogale penicillata Brush-tailed Rock-wallaby V E 0 Phascolarctos cinereus Koala V V 1 Scoteanax rueppellii Greater Broad-nosed Bat - V 1 Vespadelus troughtoni Eastern Cave Bat - V 8
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Status No. records in Species name Common name locality (Atlas EPBC Act TSC Act data)
Reptiles Delma torquata Adorned Delma V - 0 Furina dunmalli Dunmall's Snake V - 0 Uvidicolus sphyrurus Border Thick-tailed Gecko V V 2
Fisheries Management Act (1994) listed aquatic species The database search results (OEH Atlas) indicate that there are no threatened fish species recorded in study area. However, a review of Fish Communities and Threatened Species Distributions of NSW (DPI 2016) shows that the Mole River is part of the indicative distribution of one endangered species and two endangered populations:
· Purple Spotted Gudgeon (Mogurnda adspersa) – endangered · Western population of Olive Perchlet (Ambassis agassizii) – endangered population · Murray-Darling Basin population of Eel Tailed Catfish (Tandanus tandanus) – endangered population Further survey work would be required to determine if the aquatic habitat within the study area is suitable for these species.
H.4.2.7 Migratory species The PMST report indicates that 12 listed migratory species may occur within the study area. The habitat within the study area is considered unlikely to form a substantial or ‘important’ habitat for migratory species. Therefore migratory species are considered to present a low constraint if they are present in the study area.
H.4.3 Potential impacts Based on this high-level desktop assessment, a summary of potential impacts associated with the three dam capacity options are provided below.
H.4.3.1 Native vegetation and fauna habitat Direct impact to native vegetation and fauna habitat as a result of inundation based on the three dam capacity options are displayed in Table H.7. Dam capacities of 100GL, 200GL and 300GL will result in the inundation of 346.84 hectares (from 7 PCTs), 559.66 hectares (from 11 PCTs) and 907.19 hectares (from 12 PCTs) of native vegetation respectively. Without undertaking a site assessment of the study area, it is assumed that much of this vegetation will contain suitable habitat for a range of threatened flora and fauna species.
As expected, the 300GL capacity option has the largest impact on native vegetation and fauna habitat. Table H.7 shows impact areas and the percentage of that community within the locality (10 km radius around study area) that will be impacted. PCTs that stand to incur the largest impact on their local extent include:
· Blakely's Red Gum - Yellow Box grassy tall woodland – 15.8% to 35.7% reduction · White Cypress Pine - Silver-leaved Ironbark - Caley's Ironbark open forest – 16.3% to 23% reduction · Silver-leaved Ironbark - Black Cypress Pine +/- White Box shrubby open forest – 4.3% to 20.9% reduction · River Oak - Rough-barked Apple - red gum - box riparian tall woodland – 6.6% to 13.5% reduction The inundation of this vegetation would result in the loss of potential habitat for a range of threatened flora and fauna species. Based on this assessment 27 threatened fauna species and 15 threatened flora species may occur within the proposed inundation areas and be impacted by the proposal. It is unlikely that all these species
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will be present onsite, however without adequate field surveys the precautionary principle must be applied. It is therefore also not possible to quantify impacts the threatened fauna or flora at this stage.
Table H.7 : Summary of direct impacts to native vegetation
Area (ha) impacted within inundation Extent (ha) Percent cleared area (percentage of community within within locality within Border Plant Community Type (PCT) locality)* (10km)* Rivers/Gwydir CMA 100 GL 200 GL 300 GL
River Oak - Rough-barked Apple - red gum - box riparian tall woodland 164.35 225.74 334.83 (wetland) of the Brigalow Belt South Bioregion and Nandewar 2489.42 60% Bioregion (PCT ID 84) (6.6%) (9.1%) (13.5%)
Grey Box grassy woodland or open forest of the Nandewar Bioregion 0.80 1.12 2.08 379.89 85% and New England Tableland Bioregion (PCT ID 516) (<1%) (<1%) (<1%)
Grey Box shrubby open forest of northern parts of the Nandewar 0.06 1.53 0 11763.61 75% Bioregion and New England Tableland Bioregion (PCT ID 517) (<1%) (<1%)
Rough-barked Apple - White Cypress Pine - Blakely's Red Gum 0.16 0.65 riparian open forest / woodland of the Nandewar Bioregion and New 0 94.46 65% England Tableland Bioregion (PCT ID 544) (<1%) (<1%)
Wild Quince - Mock Olive - Rusty Fig - Iamboto - Sweet Pittosporum 0.04 dry rainforest of rocky and scree areas of the Nandewar Bioregion and 0 0 250.79 20% New England Tableland Bioregion (PCT ID 547) (<1%)
Silver-leaved Ironbark - Black Cypress Pine +/- White Box shrubby 53.07 144.82 260.15 1246.99 55% open forest mainly in the northern Nandewar Bioregion (PCT ID 549) (4.3%) (11.6%) (20.9%)
Tumbledown Red Gum - White Cypress Pine - Caley's Ironbark 2.04 4.91 shrubby open forest of the Nandewar Bioregion and western New 0 95.02 40% England Tableland Bioregion (PCT ID 562) (2.1%) (5.2%)
White Box - Silvertop Stringybark +/- White Cypress Pine grass shrub 0.48 1.97 open forest of the southern Nandewar Bioregion and New England 0 1404.51 45% Tablelands Bioregion (PCT ID 563) (<1%) (<1%)
White Cypress Pine - Silver-leaved Ironbark - Caley's Ironbark open 11.75 12.32 16.57 forest of the central Nandewar Bioregion and western New England 72.08 70% Tableland Bioregion (PCT ID 564) (16.3%) (17.1%) (23%)
Silver-leaved Ironbark - White Cypress Pine shrubby open forest of 56.36 77.00 113.74 2150.15 55% Brigalow Belt South Bioregion and Nandewar Bioregion (PCT ID 594) (2.6%) (3.6%) (5.3%)
Tumbledown Red Gum - White Cypress Pine - Silver-leaved Ironbark 47.53 76.21 141.36 shrubby woodland mainly in the northern Nandewar Bioregion (PCT ID 5957.77 40% 596) (<1%) (1.3%) (2.4%)
Blakely's Red Gum - Yellow Box grassy tall woodland on flats and hills 12.98 19.72 29.36 in the Brigalow Belt South Bioregion and Nandewar Bioregion (PCT ID 82.28 30% 599) (15.8%) (24%) (35.7%)
Total 346.84 559.66 907.19 25986.97 - Candidate Native Grasslands 385.82 555.72 872.43 - - Not native (cleared land) 42.61 65.42 116.73 - - *Calculations based on vegetation mapping (OEH 2015)
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H.4.3.2 Threatened ecological communities Direct impacts to threatened ecological communities (TECs) as a result of inundation based on the three dam capacity options are displayed in Table H.8. At least two TSC Act TECs and two EPBC Act TECs are likely to be impacted by the proposed options.
Table H.8 : Summary of direct impacts to threatened ecological communities
Extent (ha) impacted within inundation areas* Threatened Ecological Community (TEC) 100 GL 200 GL 300 GL
TSC Act White Box Yellow Box Blakely’s Red Gum Woodland (Endangered Ecological Community) 12.98 20.36 31.99 Semi-evergreen Vine Thicket in the Brigalow Belt South and Nandewar Bioregions (Endangered Ecological Community) 0 0 0.04
EPBC Act White Box-Yellow Box-Blakely's Red Gum Grassy Woodland and Derived Native Grassland (Critically Endangered) 12.98 20.36 31.99 Semi-evergreen vine thickets of the Brigalow Belt (North and South) and Nandewar Bioregions (Endangered) 0 0 0.04
Candidate Native Grasslands (Critically Endangered) 385.82 555.72 872.43 *Calculations based on vegetation mapping (OEH 2015)
H.4.3.3 Recommendations The next phase of the biodiversity assessment requires a detailed ecological investigation of the sites to ground-truth vegetation mapping, determine the potential for threatened species at the site and assess the extent and condition of the threatened ecological communities. This investigation would serve to inform an impact assessment, and the need for ecological offsets. A detailed site inspection would also enable the determination of Key Fish Habitat based on the Policy and Guidelines for fish habitat conservation and management (DPI 2013) which details the applicable policies and guidelines used for developments and other activities affecting fish habitats.
The EP&A Act imposes obligations on developers and consent authorities to assess and consider the impacts of proposed development on threatened species and communities considered as having a moderate to high likelihood of occurrence on the development site during the development assessment process. For threatened biodiversity listed under the TSC Act the threatened species assessment is undertaken as outlined under Section 5A of the EP&A Act (known as the 7-part test). The document Threatened Species Assessment Guidelines: The Assessment of Significance (DECC 2007) outlines a set of guidelines to help applicants/proponents of a development or activity with interpreting and applying the factors of assessment in the 7-part test.
Additionally, if threatened species and/or threatened ecological communities listed under the EPBC Act are determined to have a moderate to high likelihood of occurring within the development site, then they may be subject to Assessments of Significance to determine the potential impact of an activity. Any future development will need to consider whether a referral is required due to a potential significant impact on MNES. For threatened biodiversity listed under the EPBC Act, significance assessments would need to be completed in accordance with the Matters of National Environmental Significance Significant Impact Guidelines 1.1 (SIG 1.1) (DoE 2013).
It is important to highlight that the potential biodiversity constraints identified in this desktop assessment are precautionary and preliminary only. The next phase of the biodiversity assessment requires a detailed ecological investigation of the sites to ground-truth vegetation mapping, determine the potential for threatened species at the site and assess the extent and condition of the threatened ecological communities. This
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investigation will inform the impact assessment and also guide potential opportunities for retaining vegetation for ecological offsetting purposes.
H.5 Contaminated lands The following section outlines the results of a high level review to assess potential contamination risks associated with the project. The objectives of the contamination assessment were to assess potential areas of environmental concern (with respect of contamination) to support the environmental assessment for the project.
The potential for contamination has been considered in context of historical and current activities/operations likely to have been undertaken within and/or adjoining the predicted inundation extents and assessed with respect to contamination source, migration pathway and receptor relationships by development of a preliminary risk assessment (PRA). The PRA provides a matrix where contamination potential/risk can be quantified through intrusive investigations (should risks be identified).
The potential contamination risks have been assessed in context of impacts to human health and the environment associated with the construction and operation of the project, including areas which would be affected by inundation during operation of the project.
H.5.1 Methods The following information sources were reviewed to assess potential contamination sources within and/or adjacent to the inundation extents associated with the project.
· Grafton 1:250,000 Geological Series Sheet SH56-6 · Mineral Councils of Australia (2010) Strategic Framework for Managing Abandoned Mines in the Mineral Industry (MCA 2010) · Department of Primary Industries (September 1990) Mole and Severn River Dam Sites Summary Report on First Stage Investigations (DPI 1990) · Rich. E and Rosen. S (May 1991) A Preliminary Historical and Archaeological Survey of the Upper and Lower Mole River Dam Options (Rich and Rosen 1991). A summary of the findings of the information review is provided below.
H.5.1.1 MCA, 2010 An excerpt from the MCA (2010) report is provided below.
“The Mole River Arsenic Mine is located 34 kilometres west of Tenterfield in northern New South Wales. The mine was the second largest production site for arsenic products in New South Wales up to its closure in 1940. Whilst works were carried out in 2002, studies by Nguyen et al (2006) from the University of Queensland concluded that the site is ‘still very unstable’ and that ‘potentially large amounts of water soluble arsenic species could be discharged into surrounding ecosystems by chemical and mechanical weathering’. Water testing showed that contaminants from the site were found in the nearby Mole River.
The Derelict Mines Program (DMP) is administered by the Department of Industry and Investment and manages mine sites where no company, organisation or individual can be found to be responsible for the rehabilitation of a site. Due to the contamination risk, the Mole River Arsenic Mine was prioritised for works by the DMP. The Border Rivers – Gwydir Catchment Management Authority (CMA) have a charter to improve the health of water catchments. In 2007–2008, under their Point Source Pollution Incentives, the CMA prioritised funds towards a rehabilitation project at Mole River. The CMA was aware of the risks posed by the Mole River Arsenic Mine and was keen to support remediation of the site.
A works program was jointly developed by the DMP and the CMA. A core aim of the works was to improve the water quality leaving the site while effectively managing the significant heritage items. The rehabilitation plan resulted in improvements to surface drainage and the prevention of the movement of contaminants by encapsulating contaminated material on site. All disturbed areas were revegetated to ensure surface stability.
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Monitoring to date has shown a significant increase in surface stability and an improvement in water quality leaving the site”.
H.5.1.2 DPI, 1990 A summary of the DPI (1990) report with respect to potential contamination is provided below.
The report indicated that the larger dam option would impact upon the abandoned Mole River arsenic mine and waste dumps. Whilst the waste dumps were likely to contain high levels of arsenic and possibly significant levels of other toxic metals, a study undertaken by the NSW Department of Mines in 1977 (study not available for review during the preparation of this assessment) concluded that stream sediment draining from the mine workings had a negligible effect upon quality of sediment in the Mole River.
The report indicated that water quality problems could arise during flood events which could result in unacceptable levels of arsenic within the local area of the reservoir associated with contact with waste dumps and inundation of the mine and that consideration should be given to either bunding and/or removal of tailing materials.
In context of the current inundation extents, it is understood that Mole River arsenic mine is located close to the intersection of Mole River Road and Potters Road near the north western inundation extent. The DPI (1990) report discussed risks with respect to concentrations of arsenic in sediments and the potential impacts to water quality from arsenic and other heavy metals associated with localised inundation. There is the potential for soluble arsenic and other toxic compounds (namely metals and sulphur) to be present in mine workings, tailing and refining wastes.
H.5.1.3 Rich and Rosen, 1991 A summary of the Rich and Rosen (1991) report with respect to potential contamination is provided below.
Tin Mining and Smelting Tin mining and smelting began in the region in the late 1800’s. Tin mining was undertaken by the Heffernans in the early 1900’s along Pyes Creek located was located with the Upper Mole dam option.
In context of the current inundation extents, it is understood that Heffernans tin mine is located adjacent to Pyes Creek within the southern eastern portion of the inundation extent. From a review of the Grafton 1:250,000 Geological Series Sheet, the geological unit underlying the reported mine location comprises lower permian undifferentiated granites and granodiorites which occurs as a relatively small isolated unit within the area. The isolated extent of this geological unit is likely to support localised tin mining operations.
It is possible that tin and other toxic compounds (namely other heavy metals) could be present in mine workings, tailing and smelting wastes.
Arsenic Mining and Refining Arsenic was discovered in the Mole River around 1920 and mining commenced in 1924. The mining lease of the Mole River arsenic mine covered an area of 80 acres with an additional 40 acres for prospecting. Arsenic refining at the site comprised furnaces, flues and acid reclaiming plants. Arsenic was also mined at Pyes Creek between 1923 and 1924, although the exact location of this mine is not known.
By 1931, it was claimed that the mine consisted of several mines hundreds of feet deep. Four furnaces and associated flues were present at the mine site during its peak production. At this time, the mine was producing 20 tonnes of pentoxide and 15 tonnes of white arsenic per week.
In 1935, “the big blow” resulted in 5 tonnes of arsenic per day being blown over an area extending 6 miles from the mine for 2 weeks (i.e. 70 tonnes of arsenic released over the two week period). During the “big blow”, arsenic was deposited in the river, trees were defoliated and soils contaminated. The arsenic from the “big blow” killed livestock and affected numerous people. An injunction was served to the mine, stopping work on the deposit.
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Arsenic processing continued at the site between 1935 up until close in 1940 with arsenic sourced from Wiluna in Western Australia. The process produced arsenic trioxide which was pumped into vaults on site, heated to remove water to create “marbles”. Fuel for the processing was sourced from wood and later from coke.
Between 1929 and 1935, 2,850 tonnes of arsenious oxide and arsenic pentoxide was produced at the site.
Remnants of the arsenic mine were reported to be located in the near proximity to the inundation extent within the north western portion of the project area. Considering the scale of the arsenic mining detailed in the information above (80 acres for mining and 40 acres for prospecting), it is possible that mining and refining occurred across a larger regional area. From a review of the Grafton 1:250,000 Geological Series Sheet, the geological unit underlying the reported mine location comprises permo-carboniferous black silicified mudstones and siltstones which extends regionally. The regional extent of this geological unit could support the potential for arsenic mining to extend further than the known and isolated location of the Mole River arsenic mine (including the mine workings reported to be undertaken at Pyes Creek).
There is the potential for arsenic and other toxic compounds (including sulphur) to be present in mine workings, tailing and refining wastes.
Tobacco Farming and Curing Tobacco growing and curing in the Mole River commenced between 1929 and 1930.
It is understood that large quantities of pesticides are used in tobacco cultivation. Pesticide residues may be present with areas of cropping, curing and storage. Tobacco curing sheds are known to be present within the south eastern inundation extents.
H.5.2 Results
H.5.2.1 Potential Contamination Sources Based on the review of the above information sources, historical sources of potential contamination could be present within and/or adjacent to the inundation extents as detailed follows:
· Localised contamination associated with tin mining and smelting may be present within the inundation area. Potential contamination sources could include heavy metals and other toxic compounds in mine workings, tailings and smelting wastes. More diffuse levels of tin and associated compounds may also be present associated with the deposition of particulates associated with smelting activities. These contaminants may also be present in surrounding soils, sediments within waterways and as dissolved metals in surface waters. · More widespread contamination (in comparison to tin mining) associated with arsenic mining and refining. Arsenic mining and refining activities are known to have occurred adjacent to but could have also extended in the inundation area. Potential contamination sources could include heavy metals and other toxic compounds including sulphur and acid materials in mine workings, tailings and refining wastes. These contaminants may also be present in surrounding soils, sediments within waterways and as dissolved phase contamination in surface waters. A documented arsenic release (big blow in 1935) contaminated soils and waterways adjoining the mine. Site rehabilitation works were undertaken at the mine site in the early 2000s. The rehabilitation works stabilised the mine site only to prevent the transport of arsenic contaminated sediment into the Mole River. It is understood that arsenic contaminated materials are still present on site. No information was provided with respect to the rehabilitation and/or remediation of areas outside of the mine site, namely those areas impacted by the 1935 big blow. · Disperse pesticide residues may be present in soils in areas formerly used for tobacco cultivation. More localised and potentially more concentrated pesticide residues in soils may be present in the vicinity of curing sheds and storage areas. The risk of significant pesticide contamination to be present within sediments and surface waters of waterways is likely to be low as soil particles are likely to have been bound by vegetation associated with cultivation and natural vegetation and also because pesticides are generally insoluble.
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H.5.2.2 Receptors Based on our understanding of the project, possible receptors to contamination (if present) are considered to be the following:
· Workers associated with the construction of the dam and associated infrastructure · Environmental receptors adjacent to and downstream of construction activities · Environmental receptors within inundation extents · Agriculture utilising dam water (irrigation and/or stock watering) · Recreational users of the dam (swimming and/or fishing).
H.5.3 Preliminary Risk Assessment The Preliminary Risk Assessment (PRA) provides a qualitative (Level 1) risk assessment based on identifying potential contaminant sources–pathways-receptor linkages.
The PRA has been developed in general accordance with the requirements for a qualitative risk assessment as outlined in AS/NZS 4360:2004 Risk Management Guidelines and the National Environment Protection (Assessment of Site Contamination) Measure 1999 (as revised 2013) guidelines.
H.5.3.1 Conceptual Site Contamination Model The following conceptual site model (CSM) has been developed to outline potential contamination source/pathway/receptor relationships which may be present within and/or adjacent to the inundation extents. If any of the above relationship items do not exist, then there is no risk. The CSM is outlined in Table H.9.
Table H.9 : Conceptual Site Contamination Model Source Contaminant Distribution Exposure Receptor
Tin Mining and Smelting Heavy metals, Shallow soils, sediments, INH, DER, ING Construction workers, beneficial users of dam water hydrocarbons (mainly PAH surface waters (agriculture), environmental receptors and future in slag materials) recreational users within the inundation extent
Arsenic Mining and Heavy metals, sulphur, Shallow soils, sediments, INH, DER, ING Construction workers, beneficial users of dam water Refining acids surface waters (agriculture), environmental receptors and future recreational users within the inundation extent
Tobacco Farming and Pesticides, hydrocarbons, Shallow soils INH, DER, ING Construction workers, environmental receptors and Curing heavy metals future recreational users within the inundation
Notes INH - Outdoor inhalation of soil/dust particulates DER - Dermal contact with soil/dust ING - Incidental ingestion of dust particulates PAH – Polycyclic Aromatic Hydrocarbons
H.5.3.2 Risk Assessment The following provides a preliminary risk assessment (qualitative risk assessment) for human and environmental receptors associated with potential contamination from the sources as detailed in the conceptual site model. The risk assessment has included a consideration of the sources of risk, negative consequences and the likelihood that those consequences may occur with the resulting risk analysed by combining consequences and their likelihood.
The process for the assessment of consequence, likelihood and associated risk levels are provided in Table H.10, Table H.11 and Table H.12 and below with the risk ranking detailed in Table H.13.
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Table H.10 : Consequence Scale
Level Descriptor Consequence on Health Consequence on Health
Major off-site release, long term environmental 5 Severe Single fatality or permanent disability. damage.
Major off-site release, short to medium term 4 Major Chronic health issues. environmental damage.
Off-site release, no significant environmental 3 Moderate Short to medium term health issues. damage.
Major on-site release, with some on-site 2 Minor Minor short term health effects. environmental damage. No off-site release.
On-site release. Containable with minimal 1 Negligible No measurable health effects. damage. No off-site release.
Table H.11 : Likelihood Scale
Level Descriptor Description Frequency
A Almost Certain Frequent occurrence Daily
B Likely Regular occurrence Weekly
C Possible Random occurrence Monthly/Yearly
D Unlikely Unlikely occurrence Yearly
E Rare Almost impossible Once every 100 years
Table H.12 : Risk Matrix
Consequence Level Likelihood Level
1 2 3 4 5
A Moderate High High Very High Very High
B Moderate Moderate High High Very High
C Low Moderate High High High
D Low Low Moderate Moderate High
E Low Low Moderate Moderate High
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Table H.13 : Risk Ranking
Exposure Source Receptors to Contamination Consequence Likelihood Risk Ranking Pathways
Soils contaminated by historical INH, DER, ING Construction workers Minor (2) Unlikely (D) Low tin mining and smelting
Sediments contaminated by Construction workers, environmental historical tin mining and DER, ING receptors and future recreational users Moderate (3) Unlikely (D) Moderate smelting within the inundation extent.
Construction workers, beneficial users Surface water contaminated by of dam water (agriculture), historical tin mining and DER, ING environmental receptors and future Minor (2) Unlikely (D) Low smelting recreational users within the inundation extent.
Soils contaminated by historical INH, DER, ING Construction workers Moderate (3) Unlikely (D) Moderate arsenic mining and refining
Sediments contaminated by Construction workers, environmental historical arsenic mining and DER, ING receptors and future recreational users Moderate (3) Unlikely (D) Moderate refining within the inundation extent,
Construction workers, beneficial users Surface water contaminated by of dam water (agriculture), historical arsenic mining and DER, ING environmental receptors and future Moderate (3) Unlikely (D) Moderate refining recreational users within the inundation extent.
Construction workers, environmental Soils contaminated by historical INH, DER, ING receptors and future recreational users Minor (2) Unlikely (D) Low tobacco farming and curing within the inundation extent
H.5.4 Potential Impacts - Risk to Human Health There are no very high to high perceived risks to human health or the environment from any of the potential contamination sources from the site or adjoining areas. Moderate perceived risk to human health and/or environmental receptors exists for the following receptors:
· Moderate Risk – Exposure of construction workers, beneficial users of dam water (agriculture), environmental receptors and future recreational users within the inundation extent to contaminated soils, sediments and surface water (if present) during construction and operation of the project. The moderate risk is generally associated with the potential for more widespread operations associated with arsenic mining (compared to the more localised tin mining operations) and the potential for ingestion of contamination (e.g. bio-magnification of contamination in fish for consumption and use of contaminated water for irrigation of crops and watering of livestock). Based on the understanding of historical land use of the site, a number of potential contamination sources have been identified which could pose an exposure to human health and/or environmental receptors during construction activities and operation of the project.
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To quantify these potential risks, it is recommended that a sampling and analysis program be developed which targets potential contamination sources which could be disturbed as part of construction and operation of the project.
H.6 Water Quality The following section outlines the results of a high level review to assess the existing water quality and likely impacts associated with the options for the proposed major water storage area within the Upper Mole River.
H.6.1 Methods Assessment of likely and potential impacts of the proposed Mole River Dam options on surface water quality included review of readily available literature relating to the study area. The review was used to obtain background information on the existing water quality, catchment history and land use to aid in interpreting the existing conditions. This included searches of the following data sources for available water quality data:
· Tenterfield Shire Council · Murray Darling Basin Authority · NSW Department of Primary Industries (DPI) Water · Bureau of Meteorology Water Data Online Database · State of the Catchment Report 2010 – Border Rivers-Gwydir Region (Office of Environment & Heritage (OEH) (2011) Previous reports relevant to the study area were also reviewed, and included the following:
· Preliminary Environmental Assessment (PEA) of Additional Water Supply Options Mole River and Severn River Dam Sites, NSW Department of Water Resources (DWR1990) · Additional Water Supply Options Water Quality Considerations, NSW Department of Water Resources (DWR 1990a) The online database searches did not yield recent water quality data (<10 years old) from the Mole River (or surrounding tributaries), thus the following section focusses on general water quality and landuse conditions of the surrounding basin, and identifies potential impacts associated with the proposed storage.
H.6.2 Results
H.6.2.1 Landscape context The Border Rivers catchment includes the Dumaresq, Severn, Macintyre and Mole Rivers in NSW with the Dumaresq and Macintyre Rivers forming the border between NSW and Queensland. The headwaters of the Macintyre River originate in Northern NSW and the river becomes the Barwon River where it crosses the jurisdictional boundary between Queensland and New South Wales. The catchment covers an area of 49,500 square kilometres, of which just under half (24,500 square kilometres) is in the NSW portion of the catchment. The catchment has summer-dominant rainfall with high variability, resulting in variable river flow from season to season.
Mole River is contained within the Border Rivers catchment and flows north-west through a deeply incised valley, to the confluence of the Dumaresq River on the New South Wales and Queensland border. Within the upper extents, Mole River is narrow and steep sided valley becoming wider and more open downstream.
The land use history in Mole River was predominantly logging, tobacco harvesting, arsenic, tin and gold mining (Rich & Rosen 1991). Current land use within the region is largely agriculture, including dryland farming and irrigation.
H.6.2.2 Water Quality
General Water Quality
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NSW Department of Water Resources (DWR) (1990a) reviewed water quality within the Mole River with respect to Upper and Lower Mole River Dam siting options. Mole River water quality monitoring was conducted from 1974 - 1988. The data are not representative of existing water quality as it is more than 30 years old and would not capture the influence of catchment changes to water quality since that time. Additionally, the 1974-1988 Mole River Water Quality data was determined insufficient to enable detailed assessment of water quality and did not show any clear trends (DWR 1990a).
General water quality conditions within the wider basin are now better understood. The Border Rivers (NSW) Water Quality and River Flow Objectives (2006) identify the general conditions within the broader catchment. Generally, water quality within the catchment is often poor wherever intensive agricultural industries and/or rural residential developments are present. Agricultural chemicals (for example, pesticides) have been commonly detected in many of the rivers, especially downstream of irrigated cotton and some broadacre crops. Increased sedimentation and high nutrient concentrations are major water quality issues in most streams. Data collected within the Mole River at Donaldson between 2005 – 2008 as part of the 2010 State of the Catchment Report (OEH 2010) indicated elevated total phosphorus concentrations with 94% of sampling events exceeding the recommended Australian and New Zealand Guidelines for Fresh and Marine Water Quality developed by the Australian and New Zealand Environment and Conservation (ANZECC) and Agriculture and Resource Management Council of Australia and New Zealand (ARMCANZ) (ANZECC/ARMCANZ 2000).
Water quality impacts associated with mining As discussed in Section 3, a number of mines including arsenic and tin have occurred within the immediate catchment for Mole River. There is some uncertainty around the exact locations and extents of both mines and further detailed investigations would be required to ascertain the potential impacts upon water quality associated with:
· Tin mining and smelting resulting in heavy metals and other toxic compounds. These contaminants are likely to be localised, but may also be present in surrounding soils, sediments within waterways and as dissolved metals in surface waters. · Arsenic mining and refining resulting in heavy metals and other toxic compounds such as sulphur and acid materials in mine workings, tailings and refining wastes. These contaminants may be more widespread than the tin mine, and may also be present in surrounding soils, sediments within waterways and as dissolved phase contamination in surface waters. It is understood that arsenic contaminated materials are still present on site. No information has been found with respect to the rehabilitation and/or remediation of areas outside of the mine site, namely those areas impacted by the 1935 big blow. A study conducted by Ashley & Lottermoser (1999) found stream sediments within a radius of 2 km of the mine displayed arsenic metal enrichments double the concentration of the mean background concentrations from the surrounding area. This enrichment has been caused by erosion and collapse of waste-dump material into local creeks, seepages and ephemeral surface runoff, and erosion and transportation of contaminated soil into the local drainage system. Prior to remediation in 2007-2008, water samples from a mine shaft and waste-dump seepages were acidic, with low pH (4.1) and high arsenic concentrations. Maximum arsenic concentrations (up to 13.9 mg/L) significantly exceeded the Arsenic (As(v)) ANZECC/ARMCANZ (2000) default trigger values for Arsenic (As(v)) (0.0013mg/L). The rehabilitation of the Mole River Arsenic Mine was identified in the SOC (OEH 2010) as a target to improve river health and water quality prior to 2015.
H.6.3 Potential Impacts A number of potential water quality impacts have been identified in relation to the operation of the proposed dam:
· Algae problems are likely for each option given the surrounding land use and high nutrients levels within the surrounding streams. Irregular and variable flows typical of the region may increase residence times and decrease flushing periodically, increasing the time available for algal growth (DWR 1990a). Algal blooms and cyanobacteria impacts will affect water quality for consumption, water availability to landowners downstream and to visual amenity. Algal problems may also be observed downstream due changes to flow and flushing of Mole River.
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· Turbidity levels within the storage are likely to be high resulting from a combination of surrounding soils, erosion and irregular runoff (DWR 1990a). · Thermal stratification may occur within deeper storages in the summer season. Thermal stratification can result in the deoxygenation of the poorly mixed bottom layers, resulting in the release of nutrients from sediments and the production of hydrogen sulphide. The 300GL option has the greatest risk in relation to thermal stratification, as it is the deepest storage option. · Deep water storages can also increase the likelihood of cold water pollution. Many older dams release water from the bottom of the reservoirs where temperatures and dissolved oxygen concentrations are low and nutrient concentrations are high. Releases of changed water quality conditions can affect long distances downstream and can result in a wide range of impacts, such as a disruption to fish breeding and distribution patterns as many native fish will not breed in colder water. · Salinity may increase in storages over a period of time due to evaporation. The amount of increase depends upon the surface area of the storage and the amount of flow through it. Storages with long retention times will have a greater potential for evapo-concentration of salinity than storages with short retention times. The 300GL option has the greatest risk in relation to salinity, as it has the largest surface area. · As the dam will store additional water, the water flow regime downstream will change. Downstream flow changes, resulting from the proposed dam will need to be managed in order to maintain environmental features and water supply requirements. Environmental factors to consider includes river flows in dry seasons, protecting inundation patterns of flood-dependent ecosystems, native fish, wetlands, water requirements for riparian and floodplain vegetation. Changes to flow (volume and velocity), the wetted area, water quality, bathymetry and substrate and riparian vegetation are likely. · Fine sediments will be captured and deposited behind the dam wall rather than being transported downstream. The dam will reduce downstream sediment transport and change the geomorphology of the waterway.
H.6.3.1 Recommendations The next phase of the water quality assessment requires detailed water quality monitoring of the waterways within the Mole River catchment to determine the existing water quality. Comprehensive monitoring needs to occur over wet and dry weather periods, and include monitoring of temperature, turbidity, conductivity, pH, dissolved oxygen, dissolved and total metals, nutrients, suspended solids and chlorophyll-a. Detailed studies targeting heavy metals and other toxic compounds associated with the tin and arsenic mines are also required. These investigations would determine the suitability of the site for inundation, and inform the environmental impact assessment.
Subsequent investigations are required to ascertain anticipated operation and design of the Dam (such as offtake level), so that environmental flows modelled on the natural flow regime can be designed and implemented to manage downstream impacts.
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Figure H.4 : Study area showig approxiate location of arsenic and tin mines
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Figure H.5 : AHIMS sites
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H.7 Aboriginal and non-Aboriginal Heritage The purpose of this Aboriginal and non-Aboriginal heritage desktop assessment was to contextualise the broader scope of the history and general landform of the area, identify those heritage assets already registered within the study area, identify areas with the potential to contain heritage values within the assessment area and make recommendations for the further investigation and management of heritage values if required.
H.7.1 Aboriginal heritage desktop assessment The following sections describe the environmental conditions of the assessment area and the method used to gather information and identify any Aboriginal cultural heritage values within the assessment area.
H.7.1.1 Geomorphology, geology and hydrology The Mole River assessment area lies within a larger landform called the New England Tableland which consists of a stepped plateau of hills and plains partially divided uplifted peneplain. This dissection distinguishes the east and west flowing rivers. The area to east and west of the main divide is composed of an erosion surface called Laterite Surface (Rosen, 2009). Carboniferous and Permian age sedimentary rocks compose the New England fold belt. Tertiary basalt flows cover most of the bedrock and subsequent erosion by the basalt had previously exposed sands that contained precious stones and tin ores. Geology of this region largely dictates topographical formation.
The Great Escarpment located toward the eastern edge of the New England Tableland bioregion is characterised deep crevices within the plateau shaped by coastal streams. Extending beyond this, boulder outcrops and rounded tors typify the granite country and then mostly continuous planar characterises the basalt country. Within the basalt country, however the generally planar area is interrupted by sporadic peaks surrounding former eruption areas (OEH, 2015).
Soils surrounding the rock outcrops within the assessment area are composed of siliceous sands and these morph into red earth, erosional low fertility soils. However, richer organic soils occur close by sedgelands and support forest and woodland growth (OEH, 2015). The organic soil cover of the area facilitates and ideal environment for agricultural and pastoral pursuits (Rosen, 2009).
Mole River is one of the major river systems composing the Borders Rivers catchment and as such part of the Murray-Darling Basin (Department of Primary Industries Water, 2017). The convergence of the Bluff and Deepwater Rivers mark the formation of the Mole River, approximately 6 km west of the New England highway between Tenterfield and Deepwater and then continues to flow to the North West and joins up with the Dumaresq River on the NSW/QLD border (Grose and Holics, 1990).
Characterised by steep, rocky hillslopes and native woodland dominated crests, the upper Mole river site catchment area covers roughly 1402 km2. At the intersection of Deepwater and Bluff Rivers the area is typified by hilly terrain. These rivers continue for 71 km and then begin to morph into the Dumaresq River. Comprised within the upper Mole River area are nine distinct waterholes linked by narrow gravel riffle areas. Conversely, the lower Mole river catchment is slightly larger than the upper Mole River catchment area comprising an area of around 1563 km2. Parabolic rocky, wooded slopes and mountains typify this area. This area includes fifteen waterholes connected by narrow riffle areas. Each of the areas demonstrates a dendritic drainage catchment, where the tributary systems divide from the main stream like limbs of a tree (Grose and Holics, 1990).
H.7.1.2 Aboriginal cultural context Aboriginal occupation of NSW is likely to have spanned at least 20,000 years with late Pleistocene occupation sites have been identified at Shaws Creek in the Blue Mountain foothills (14,700 BP, Kohen et al. 1984), Mangrove Creek and Loggers Shelter in the Sydney Basin (c.11,000 BP, Attenbrow 1981, 2004). Aboriginal occupation of the New England Tablelands dates back at least 9,000 years, according to radiocarbon dates obtained during archaeological excavation of the Graman A2 rock shelter, located approximately 90 km west of Mole River. Other Aboriginal sites in the area with evidence of early occupation include the Graman B1 rock shelter (c.5,400 years BP), the Bendemeer 2 rock shelter (c.5,000 BP), and the Moore Creek 4 and Moore Creek 6 rock shelters near Moore Creek (c.4,000 BP) which are located to the south of Tenterfield, near Tamworth (McBryde 1977:227,229).
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Ethnographic sources indicate while a number of Aboriginal groups occupied the Mole River region at the time of European contact, the Ngarabal people traditionally occupied the south of the assessment area, from Bolivia south to Stonehenge in Glen Innes LGA (MacPherson 1905:679; Tindale 1974). In an interview for an anthropological study undertaken in 1998, elder Keith Byrne indicated that the northern boundary of Ngarabal territory was marked by the Mole River, and that the north eastern boundary was within Bolivia Station (Kerr et al. 1999:25). Parts of the assessment area may have also occupied by the Jukambal in the south east and Gee- en-yun in the north (Tindale 1974; Gardner 1978 [1842-54]:245; MacPherson 1905:679). Tindale’s descriptions of tribal boundaries are based on the distribution of language groups in this area, which are derived largely from linguistic evidence published from 1854 to 1969; however, the boundaries are approximate, and probably varied over time (Tindale 1974).It should also be recognised that traditional land were not delineated by treaties but rather defined by the people who occupied them and their associated traditions.
Social groups which shared religious and traditional customs often partook in trade and developed similar artistic motifs. In particular, the emu footprint motif is suggested to reflect the path of the Dreaming ancestors throughout the land between Bendeeer and Mt Yarrowyck (Hudson, 1996).
The earliest known evidence for Aboriginal occupation of the New England Tableland is dated to the third millennium B.P. in the Bendemeer area. However, more recent research indicates this occupation most likely extended beyond this (Connah, Davidson and Rowland, 1977). The Aboriginal population size during this the pre-contact is estimated to range between 1,150 and 1,350 people. It should however, be noted that estimates of Aboriginal population size during this time are likely inaccurate owing to estimates reflecting only European observations of Aboriginal people at the time. Furthermore, estimates also disregarded the decimated population size as a result of smallpox (Byrne, 1989).
During summer flowering plants such as honey pots, Apple Berry, gebung, wild parsnip and spreading bracyloma were utilised by Aboriginal people of the area for subsistence purposes. Other plants such as bearded heath, ferns, Australian bluebell and saw-sedge were also available year round for food. The Gwydir and Rocky Rivers provided access to shellfish, fish, waterbirds and their eggs for those living closer to the riverine environments. Conversely, those groups that resided on the more rugged terrain utilised kangaroo, possum and wallaby as principal food resources. In particular, the Anaiwan people are suggested to have lined nets between trees to catch kangaroos and dug within the area to recover yams and other roots (Hudson, 1996). Hunting grounds, fishing waters, tribal districts and burial grounds were distinguished using drawings on rocks or stone. A drawing or cutting of a particular animal within a particular area indicated a known hunting ground for that respective animal. For example, a print or picture of an emu on a rock or stone would indicate that that particular area was ideal for hunting of emu (Hudson, 1996). Moreover, firestick farming was also used as a principal strategy for subsistence purposes and also for maintenance of grassland (Hunter, Hawes and Sonter, 2012).
H.7.1.3 Historical land use Prior to 1839 the New England region was considered outside the limits of NSW settlement. Those people that squatted in outer limit areas such as this were required to pay a 10 pound licence fee, but owing to the remoteness of the region this law was not properly enforced. Between 1848 and 1858 new stations were established between 1848 and 1858 along the eastern falls and from this settlement and tenure of the land began to quickly proliferate (Rich and Rosen, 1991). An increased demand for Australian wool in the British market resulted in an influx of British capital which motivates growth of the NSW colony. In particular, the Mole Station was registered in 1848 under the Bank of Australasia and assessed by Macdonald as comprising 55,000 acres holding 892 sheep. This quickly expanded to over 60,000 acres with 10 horses and 16,000 sheep (Rich and Rosen, 1991).
The Mole River area is thought to have been regularly visited by the famous bushranger ‘Thunderbolt’. An assortment of saddles, bridles and gear discovered within the steep gorge known as ‘Kelly’s Gunyah’ are suggested to evidence occupation by the bushranger for episodic periods of time (Rich and Rosen, 1991).
The area was used for tin procurement after Charles Pattison discovered tinstone between Beardy Creek and Pye’s Creek in 1872 (Walker, 1966). The population gradually increased in response to subsequent tin discoveries, before collapsing when tin resources were identified in the Torrington district, eventuating in the production of a smelter and the district becoming a renowned tin production area (Rich and Rosen, 1991).
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The 1920s saw the primary era of arsenic mining for the Mole River area. The arsenic resource availability within the area was initially discovered by Dick Patching and Archie Nemes with a mine developed in 1924 when it was deemed there was sufficient demand for it, primarily related to the use of arsenic to control and kill prickly pear vegetation. This increased demand perpetuated the proliferation and development of the mine. During the depression, associated buildings and sheds were constructed to facilitate 24 hour mining operation (Rich and Rosen, 1991). An infusion of sulphur into the industrial processes eroded the iron baffles and resulted in the ‘big blow’ of arsenic in 1935. For a period of over two weeks, arsenic was leaked into the air and this resulted in the death of stock, illness of people and contamination of rivers, soils and vegetation. In 1935, the mine was closed but production continued at the processing site. The Mole river arsenic mine is the only mine in NSW opened exclusively for the mining of arsenic and was the largest producer in the state at the time of its peak production (Rich and Rosen, 1991). Contact between the the Aboriginal occupants of the Tablelands and European colonists was initially harmonious however this harmony did not continue for long and eventually skirmishes between the Anaiwan and the colonists occurred and resulted in the loss of hunting grounds and hunting resources and this perpetuated a cycle of continuous retaliation to the attacks from either side (Rosen, 2009).
Preliminary assessment of the Aboriginal heritage aspect of the Upper Mole River study area involved the use of the ‘extensive search’ feature of the Aboriginal Heritage Management Information System (AHIMS) to identify known Aboriginal cultural sites within the study area. Following this, previous heritage, archaeological, historical reports were examined and synthesised to contextualise the Aboriginal heritage of the study area. Based on these a predictive model was then developed to propose what site types and their associated characteristics may be identified pending further investigation of the study area.
Managed by the OEH and regulated under section 90 of the NPW, the AHIMS comprises a database of identified Aboriginal cultural places. An extensive search was undertaken by Alok Pradhan (Environmental Scientist, Jacobs) on 21 July 2017 using a shapefile of the assessment area. It should be recognised that the AHIMS database recognises only officially recorded Aboriginal sites and there does not necessarily provide accurate location coordinated if a complete recording of Aboriginal sites within the area.
The extensive search identified four Aboriginal sites within the Upper Mole River assessment area (refer to Table H.14). These four sites were recorded by E. Rich in 1991 and included artefact scatters comprising an assortment of flakes, cores and some formal tool types such as backed blades. Some of these artefacts also demonstrated evidence of retouch and usewear. The material composition of these artefacts included rhyolite, siltstone, quartz and chert.
Table H.14 : AHIMS sites within the Mole River assessment area
AHIMS ID Coordinates (AGD Zone Coordinates (AGD Zone Site types 56) - Eastings 56) - Northings
12-1-0013 383510 6774200 Open camp site 12-1-0014 383570 6773880 Open camp site 12-1-0015 383620 6773690 Open camp site 12-1-0016 383550 673820 Open camp site
H.7.1.4 Previous archaeological reports In 1991 a report on the upper and lower Mole River Dam options was undertaken which detailed several Aboriginal sites within the assessment area (Water Resources, 1991). Aboriginal sites included open artefact scatters and shelters interpreted to reflect camping and stone tool manufacture. Over time most sites have been disturbed and damaged diminished the archaeological research potential significantly. The low density artefact scatters identified within the assessment area are largely exposed or eroding from shallow soils and are predominantly compose of quartz, chert and grey to black siltstones. Three shelters were also identified, one of which confirmed as an Aboriginal sites while the other two are purported to contain archaeological deposits which may require further investigation. The NSW Department of Water Resources compiled a preliminary environmental assessment of additional water supply options for the Mole and Severn River Dam Sites in 1990
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(Water Resources Commission, 1990). The then proposed lower Mole River storage area would submerge NPWS Aboriginal Site 12-1-2 (AHIM reference not specified) consists of two stone working areas on the Kaloola property and suggested to reflect campsites as well as stone manufacture areas (McNamara, 1983). The artefacts recovered from this particular site included flakes, cores, grinding stone and biface artefacts. Another site of cultural value - 12-1-3 is located north of the storage site. However, it was proposed that location of this site meant it would not be affected by inundation.
Rosen and Rich (1991) compiled a report detailing an archaeological and historical survey of the Upper and Lower Mole River Dam Options. The report identified several open artefact scatters suggested to represent camping grounds and three shelter/cave sites. Within these sites over 400 artefacts were identified, of which quartz comprised the predominant material composition type, followed by mudstone, siltstone and chert. These included a variety of cores, bipolar artefacts, backed blades, flake tools and large pebble tools. Other Aboriginal cultural heritage sites referred to within the assessment area included a scarred tree and an Aboriginal burial. However, the precise location of these additional cultural sites is not yet specifically known (Rosen and Rich, 1991).
An Aboriginal heritage study was conducted by Australian Museum Business Services in relation to the Tenterfield Local Government Area. The analysis incorporated identification of registered Aboriginal cultural places and contextualised these through ethnographic and historic synthesis of the region. The analysis for registered Aboriginal cultural places within the Tenterfield Local Government area identified 174 previously reported sites. These were comprised predominantly of artefact scatters with lesser inclusions of culturally modified trees, ceremonial rings, art, Aboriginal Ceremony and Dreaming sites, Potential Archaeological Deposits, stone arrangements, Aboriginal resource and gathering artefacts, conflict sites, stone quarry artefacts, burials and combinations of those above. Final recommendations of this report indicated that owing to the extensive variety of Aboriginal cultural places within the region the local aboriginal stakeholder communities should be consulted to determine the relevant extent and cultural significance of those places within the region (AMBS, 2013).
H.7.1.5 Predictive modelling Previous reports indicate the potential for other archaeological sites and deposits to be identified within particular landscape contexts with the Mole River assessment area.
H.7.1.6 Predicted site types and potential locations · Low density artefact scatters or isolated artefacts are the most likely site type to be found within the assessment area. These will tend to be situated close to watercourses or in or around potential shelter areas and more obvious in eroded plateau areas. · Scarred trees are a likely site type in older growth woodlands and may be found in association to Aboriginal ceremonial grounds, burials and artefact manufacture sites. · PADs may be apparent in basal slopes in those terrestrial contexts not located directly nearby waterways. · Potential burials within the area may be characterised by parabolic shaped earth mounds with scarred trees and/or other cultural material with the direct vicinity of the area.
H.7.1.7 Predicted site characteristics · Stone artefact material types will most likely include an assortment of quartz, chert, rhyolite and siltstone. · Artefact assemblages will primarily be comprised of flakes, flaked pieces and core artefact types. However, sporadic inclusion of some specific/formal artefacts types may be distinguishable depending on the quality of raw material and contextual integrity of the site. These may include: bipolar cores, backed blades and other retouched implements. · Surface artefact material most likely does not necessarily reflect the extent on the in situ archaeological deposit. · Exposed open archaeological sites contextual integrity is most likely disturbed owing to previous land use.
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H.7.1.8 Aboriginal heritage recommendations The desktop review of Aboriginal cultural heritage values within the assessment area indicates the area is likely to contain sites of high cultural and archaeological significance. The assessment area contains evidence of Aboriginal occupation in the form of isolated finds and artefact scatters. Four open camp sites were registered in AHIMS within the assessment area. Many of the reports indicate these scatters do not represent the full extent of these Aboriginal cultural deposits and indicate that other cultural sites, such as scarred trees or even burials may be also located within certain contexts of the assessment area. The full extent of Aboriginal cultural heritage values cannot be determined through the literature review and AHIMS searches as the area has not been subject to systematic archaeological survey. Where this has occurred within the broader area, a range of sites with Aboriginal cultural heritage significance have been identified. Therefore, it is recommended that than an Aboriginal Cultural Heritage Assessment Report is undertaken which includes an archaeological survey of the assessment area alongside relevant Aboriginal stakeholders. The objective of the ACHAR is to:
· determine whether or not the project is likely to harm Aboriginal objects · assess the significance of potential impacts to any identified Aboriginal heritage or potential archaeological deposit present in the assessment area · ensure the cultural heritage values of the assessment area are protected from the effects of works through avoidance or protection as much as is practicable · Recommend mitigation and management actions to protect cultural heritage values as required · Provide advice on the consequences of affecting those constraints (e.g. approvals/ permits required) and mapping of any relevant constraints. The ACHAR and archaeological survey and consultation should be compliant with the Code of Practice for Archaeological Investigation of Aboriginal Objects in NSW (DECCW 2010b) and the Aboriginal Cultural Heritage Consultation Requirements for Proponents (DECCW 2010c).
H.8 Non Aboriginal desktop assessment
H.8.1 Background to the assessment The assessment area does comprise some items considered to be historically important, however many of these are not officially registered owing to their contaminated and/or dilapidated condition. These items and the relevant history of the study area are detailed below.
H.8.2 Method Initial assessment of the non-Aboriginal heritage aspect of the Upper Mole River assessment area involved a search of various heritage registers such as the State Heritage Register, State Heritage Inventory, relevant Section 170 Heritage and Conservation Registers Local Environmental Plans, National Trust of Australia (NSW) list, Register of the National Estate, Commonwealth Heritage List, National Heritage List, and World Heritage List and any other available registers. However, with the exception of Arsenic Mine no non-Aboriginal heritage sites were listed for the upper Mole River assessment area. Following this, previous archaeological, heritage and historical reports were reviewed to compile a synthesised overview of non-Aboriginal heritage within the area, a historical context/background and proposed significance assessment for any non-Aboriginal heritage sites found within the assessment area.
H.8.3 Historical context It wasn’t until forty years after European settlement of the Sydney and Parramatta regions that economy necessitated the expanse of settlement toward the Great Dividing Range and Bathurst. Gradually, occupation steadily extended beyond the mountain to facilitate grazing of stock (King, 1957). Surveyor General John Oxley and his party examined the course of the Macquarie River in 1818. Their six month expedition comprised the Bathurst area, Warrumbungle Ranges, the Port Macquarie Coast and finally the Moonbi Range. The Moonbi Range borders the New England Tableland (Campbell, 1978).
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Following this, under the direction of Governer Darling botanist Allan Cunningham was set to explore the area in April of 1827. It was during his return of his exploration of the area that Cunnigham crossed the Dumaresq River just west of Tenterfield near the Mole River Valley. Soon settlement of the wider area began to ensue and this catalysed the further exploration of the area, including that of Mole River by pastoralists, their employees and associated agents (Rich and Rosen, 1991).
H.8.4 Heritage context
H.8.4.1 Mole River Arsenic Mine Located 34km west of Tenterfield, the Mole River arsenic mine constituted the second largest production site for arsenic in New South Wales until the 1940s. An assessment in 2007-2008 for a proposed remediation initiative identified a number of significant heritage features. As such, a section 139 Exemption was granted to the New South Wales Heritage Branch to proceed with rehabilitation works (Strategic Framework for Managing Abandoned Mines in the Minerals Industry, 2010). The heritage item consists of a brick and timber abandoned arsenic mine. Although the opening date for the mine specifically is not known it is suggested to have begun around 1916 to facilitate the production of arsenic to use as poison to eradicate the proliferation of prickly pear vegetation. Owing to the dilapidated condition of the site the Corkill (1998) account claimed the site posed no archaeological significance and that although technical significance of the site was apparent its toxic condition meant that recording was the only avenue in which its significance could be explored.
H.8.4.2 Previous studies Water Resources Commission Department of Primary Industries compiled a report 1991. Within this report, a historical and archaeological survey was also undertaken. During the study several historic and Aboriginal sites were identified. The historic heritage places recognised within the area included the Mole Arsenic Mine; Tobacco curing barns composed of cypress pine and mud; the Pyes Creek tin mine and associated processing buddles, and the shepherd huts and sites. Pastoral heritage is reflected by both the lower and higher region, however owing to its inclusion of the arsenic mine the lower region should be considered an area of greater heritage sensitivity (Water Resources, 1991).
A preliminary environmental assessment of additional water supply options for the Mole and Severn River Dam Sites conducted by the NSW Department of Water Resources in 1990 indicated that the Mole River arsenic mine holds historical significance and would likely be affected by the then proposed dam development. The location of the development meant that the Arsenic Mine would most likely be inundated (Grose and Holics, 1990).
In 2013 Niche Environment and Heritage Pty Ltd undertook a historical heritage assessment of the then proposed route options for the Bolivia Hill area for the New England Highway development. The assessment identified 20 non-Aboriginal heritage items including an Angel Memorial, Jackson’s homestead Site, Harry and Lenny memorial, hut remains, Johnson Memorial, the mine shaft, the former bridge, the quarry, the Stone Rubble Creek Crossing, the Timber Creek Crossing, the Telegraph Line remains, the former Bolivia township, the former house site, the brickyards, the culvert, the police reserve, the former public school site and reserve, the travelling stock routes, the Bullock Track and the former road/current highway. Owing to the historic significance of these items being affected by the development extensive field survey and archaeological recording of the sites was recommended (Niche Environment and Heritage, 2013).
Non-Aboriginal sites of heritage value were also identified in the Rich and Rosen (1991) Preliminary Historical and Archaeological Survey of the Upper and Lower Mole River dam options report. The Arsenic mine was suggested to be of historical significance to the area alongside tobacco curing barns, the Pyres Creek tin mine and shepherds huts.
Rich and Rosen (1991) identified several historic heritage sites within the Mole River area including the cottage site, smithy site, the woolshed, the tennis court, the school site, the selectors hut and post office, the shepherd’s hut site, the shepherd’s grave, the mine and processing works, the manager’s office, the selector’s hut and school and the tobacco curing barns at Mole Station. Surrounding this the station area they also identified; the dingo fence at Wynella, the house/cottage, selector’s hut site, the selector’s hut and dairy site, the woolshed,
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the tin mine and buddles, the miner’s hut and the corn sheller in the Bondonga, Alister, Braeside and Pyes Creek areas (Table H.15).
Table H.15 : Description of Historic Heritage sites detailed in Rich and Rosen (1991)
Site Location History/Description Condition Significance
Cottage Site L1 3/7763 67/7995 Weatherboard Fair Social significance – cottage constructed building structure in several stages additions demonstrate changing lifestyles of the occupants. Comprises part of the squatting phase at Mole River Original Mole 7/7791 67/7988 Tankstands and Fair to good. Minor Station site L2 original chimney archaeological remaining from significance. homestead Original Mole 3/7792 67/7974 Original site of All buildings and Minor station Smithy Site smithy surface evidence archaeological L3 has been removed. interest Mole station 3/7790 67/7973 Woolshed typical of Good - Woolshed Site L4 its kind Former Tennis 3/7850 67/8010 Depressed flattened overgrown Minor social Court area with one significance concrete block remaining Second Mole River 3/8005 67/7970 Stumps of tank All buildings Local social School Site L6 stand and concrete removed significance clocks still present. Selector’s Hut and 3/8040 67/7910 Vertical board Intact externally, Possible regional Post Office Item L7 dwelling with gutted internally social significance corrugated iron roof. Believed to be built by Jacobsen the selector of the property. Darby’s Hut Site L8 3/7990 6/8160 Hut of shephard Largely demolished Possible regional Darby who was significance as employed by the demonstrative of station between shepherding lifestyle 1880 and 1900. within the area. Darby’s Grave L9 3/8040 67/8175 One post in ground. No physical Potential to Posited grave if evidence represent shepherd Darby shepherding lifestyle who was employed and thus possible at Mole station regional significance between 1880 and 1900 Mole River Arsenic 3/7925 67/7950 Remains of arsenic Partially intact State significance Mine and works mine and works.
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Site Location History/Description Condition Significance Item L10 Mine was largest and scientific value. producer if arsenic in NSW. Mole River Arsenic 3/7990 67/7950 Location where All buildings Potential to provide Mine workers camp workers and their removed insight into domestic families lived living conditions of workers and their families. Mole River Arsenic 3/7948 67/7945 Concrete slab and Building removed Related to arsenic Mine Manager’s office still evident with minimal original mine. Demonstrates Office and structure evident separation of Residence Site L12 manager from workers. Selectors Hut and 3/7905 67/7985 Hut made of Externally fair. Local significance 1st School L13 corrugated iron and Internally gutted. and regional bush timber significance Dog Proof Fence 3/8100 67/7900 Dog proof fence Maintained Local significance including timber for safe sheep fence and wire farming netting Tobacco Curing 3/7730 67/8250 Made from cypress Good but roof needs Only known tobacco Barns site L15 pine logs and repair curing barns in corrugated iron. Tenterfield area Constructed in 1930s for curring locally-grown tobacco. Bondonga 3/6955 67/8481 Asbestos cement Good Local significance Homestead No. 1 cladding on timbre Site L16 frame. Five rooms with hallway and veranda. Constructed by Alexander Wyrrand Watt in 1928 Bondonga House 3/6972 67/8454 Weatherboard Good Minor local No. 2 Site L17 house. Original signifcance section moved from Swamp Oak Creek in 1930 to serve as workman’s cottage. Hut of William 3/6935 67/8525 Hut removed. Site of Some artefacts Low Heffernon Jr Site selectors huts – scattered but site L18 William Heffernon not ploughed Jr. Hut and Dairy of 3/6880 67/8540 Hut removed. Some Hut and dairy Local significance William Heffernan footings and removed representing Snr Sit L19 concrete fireplace historical phase of still remain. Site of selectors hut selectors huts –
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Site Location History/Description Condition Significance William Heffernon Snr. Fred’s Hut site L20 3/6885 67/8525 Constructed on Poor Some significance sawn timber walls as part of historical and corrugated iron phase of selectors roof. Two rooms. hut Most likely built for the selector Joe Connolly. Steve Manser’s 3/7200 67/8515 Reported as the Buildings Local interest House Site L21 location of the demolished house of Steve Manser. Braeside 3/8040 67/7920 Edwardian style Good Local significance Homestead Site house, constructed L22 in 1936. Braeside Woolshed 3/8036 67/7910 Woolshed Good Local interest. Site L23 constructed in 1920. At the time part of Mole Station. Slab hut 3/8425 67/7503 Hut of split slabs Fair Regional and bush poles. significance as an Originally part of example of slab McAlister’s constructed hut of selection. nineteenth century Hume Bro’s Site U2 3/8620 67/7380 Complete farm site. Most buildings May have been removed though occupied by Alf and ruins of slab still Herb Hume. evident Selector’s Hut Site 3/8653 67/7394 Posts and stone Most of the building Physical evidence of U3 fireplace still remain removed selection phase of hut. Site of selectors hut Shepherd’s Hut 3/8315 67/7425 Shepherds hut. Most of the building Potential to shed Site U4 Shepherds graves removed. insight of also reported to be shepherding present. lifestyle. Pyes Creek Tin 3/8125 67/7240 Shafts with extant Not yet discerned Mine and Buddles timber work and set U5 of four buddles. Heffernans tin mine probably operated during 1920s. Pyes Creek Miner’s 3/8181 67/7233 Remains of miners Building removed Potential to provide Hut Site U6 hut information on lifestyle of miners Corn Sheller 3/8170 67/7405 Horse-powered corn Fair Sheller may be a sheller. Martins rare piece of company operated equipment
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Site Location History/Description Condition Significance 1885-1905
Rich and Rosen (1991) report provided a detailed significance assessment pertaining to these sites (Table H.15) indicated that Mole Valley structures and sites pose historic significance through their incorporation settlement of the region alongside a variety of historical themes including selection, tin mining, arsenic mining and tobacco growing. Aesthetic significance of the mining sites is suggested to be demonstrated through their representativeness of technical achievement in the production of their associated resources. Social significance of the station lies within its tourism value for the Caldwell family touring and thus also the local community. Finally, scientific significance lies within the homesteads of the squatters, managers and homesteads (Rich and Rosen, 1991).
H.8.4.3 Register search results While various heritage places are listed for the wider Tenterfield area only one site lies directly within the upper Mole River assessment area. A search of the Tenterfield Local Environmental Plan 2013 – Schedule 5 indicated one main heritage item: the Mole River Arsenic Mine (refer Table H.16).
Table H.16 : Registered Historic Heritage Sites
Item Address Property Significance Item number Listings description
Arsenic Mine Potters Road Lot 1, DP Local I010 Local 187765 Environmental Plan
H.8.4.4 Non Aboriginal heritage recommendations The toxic and derelict condition of the arsenic mine renders the archaeological significance of the site non- existent. Therefore, the site should be avoided where possible. If impacts to the site are proposed through the conduct of the project, site should be thoroughly photographed and recorded where possible and the land rehabilitated to counter the effects of arsenic contamination and facilitate a safe environmental condition before any development may proceed.
H.8.5 Summary and Recommendations Preliminary desktop assessment of the Aboriginal heritage importance of the Aboriginal upper Mole River assessment area indicates that evidence of Aboriginal occupation is evident in the form of isolated finds and artefact scatters. Four open camp sites were registered in AHIMS within the assessment area. Many of the reports indicate these scatters do not represent the full extent of these Aboriginal cultural deposits and indicate that other cultural sites, such as scarred trees, may be also located within certain contexts of the assessment area.
Based on this it is recommended that an ACHAR is undertaken including an archaeological survey of the upper Mole River assessment area in consultation with the relevant Indigenous stakeholders. The ACHAR will determine the relevant extent of existing registered Aboriginal cultural places and evaluate if any more are apparent within the area and would be impacted by the project.
The ACHAR and archaeological survey and consultation should be compliant with the Code of Practice for Archaeological Investigation of Aboriginal Objects in NSW (DECCW 2010b) and the Aboriginal Cultural Heritage Consultation Requirements for Proponents (DECCW 2010c).
Conversely, the non-Aboriginal proponent of this heritage assessment indicates that the sole heritage listed site should be avoided where possible. However, if it is deemed necessary for the Arsenic mine to be disturbed as a
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result of development, the site should be thoroughly photographed and recorded and the land be sufficiently rehabilitated before development may proceed.
H.9 Conclusion This desktop review provides a preliminary assessment of potential environmental constraints related to the proposed major water storage proposal on the Mole River. As no field surveys have been undertaken as part of this assessment, a precautionary approach has been taken to ensure that all potential constraints are considered.
H.9.1 Biodiversity Subject to further site examination and review, the main biodiversity constraints within the study area are likely to be threatened species and threatened ecological communities.
Twelve vegetation communities have been identified within the study area by review of OEH (2015) regional vegetation mapping. These communities correspond with two threatened ecological communities (TECs) listed under the TSC Act and at least one (possibly two) TECs listed under the EPBC Act:
· White Box Yellow Box Blakely’s Red Gum Woodland, which is listed as an endangered ecological community under the TSC Act and critically endangered under the EPBC Act. · Semi-evergreen Vine Thickets – is listed as endangered under the TSC Act and EPBC Act. The ecological communities within the study area are likely to be degraded due to historical disturbances, however vegetation that meets listing definitions for state and commonwealth TECs represent high ecological constraint.
No threatened species have been recorded on the site in the past, although there is potential for the site to contain habitat suitable for 15 threatened flora and 27 threatened fauna species. However, a conservative approach was taken for this desktop assessment and a field investigation is required to determine whether the site is suitable for these species.
Dam capacities of 100GL, 200GL and 300GL will result in the inundation of 346.84 hectares (from 7 PCTs), 559.66 hectares (from 11 PCTs) and 907.19 hectares (from 12 PCTs) of native vegetation respectively. Without undertaking a site assessment of the study area, it is assumed that much of this vegetation will contain suitable habitat for a range of threatened flora and fauna species.
As expected, the 300GL capacity option has the largest impact on native vegetation and fauna habitat. PCTs that stand to incur the largest impact on their local extent include:
· Blakely's Red Gum - Yellow Box grassy tall woodland – 15.8% to 35.7% reduction · White Cypress Pine - Silver-leaved Ironbark - Caley's Ironbark open forest – 16.3% to 23% reduction · Silver-leaved Ironbark - Black Cypress Pine +/- White Box shrubby open forest – 4.3% to 20.9% reduction · River Oak - Rough-barked Apple - red gum - box riparian tall woodland – 6.6% to 13.5% reduction The next phase of the biodiversity assessment requires a detailed ecological investigation of the sites to ground-truth vegetation mapping, determine the potential for threatened species at the site and assess the extent and condition of the threatened ecological communities.
H.9.2 Water Quality Current water quality within the Mole River catchment is largely unknown due to a lack of contemporary water quality data. Based on the water quality within the Border Rivers-Gwydir Catchment, nutrient concentrations are expected to be high, and increased sedimentation may occur throughout the waterways within the region. The previous tin and arsenic mines within the broader catchment area create uncertainty with regards to toxic heavy metal concentrations within the catchment, and the impacts that may occur upon inundation. Detailed studies concerning the contribution of heavy metals and other toxic compounds associated with the tin and arsenic mines are required.
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Potential impacts to water quality in relation to the three options (100, 200 and 300 GL) are relatively consistent, with the key differences identified in the increased potential for thermal stratification in the 300GL option due to increased depth, and the potential for increase salinity concentrations due to the increased surface area for evapo-concentration. From a water quality perspective, the 100GL option has the lowest environmental impact. Downstream impacts to water quality and broader aquatic environment will be consistent across the three options and will include changes to geomorphology, flows, wetted area and vegetation.
The next phase of the water quality assessment requires comprehensive water quality monitoring to determine the existing water quality.
H.9.3 Contaminated lands The contamination assessment indicates that potential contamination could be present within and/or adjacent to the inundation extents in respect to:
· Contamination associated with tin mining and smelting including heavy metals and other toxic compounds. These contaminants may also be present in surrounding soils, sediments within waterways and as dissolved metals in surface waters. · Contamination associated with arsenic mining and refining. Potential contamination sources could include heavy metals and other toxic compounds including sulphur and acid materials in mine workings, tailings and refining wastes. These contaminants may also be present in surrounding soils, sediments within waterways and as dissolved phase contamination in surface waters. It is understood that arsenic contaminated materials are still present on site. No information has been found with respect to the rehabilitation and/or remediation of areas outside of the mine site, namely those areas impacted by the 1935 big blow which dispersed toxic materials throughout the catchment area. · Disperse pesticide residues may be present in soils in areas formerly used for tobacco cultivation. The risk of significant pesticide contamination to be present within sediments and surface waters of waterways is likely to be low as soil particles are likely to have been bound by vegetation associated with cultivation and natural vegetation and also because pesticides are generally insoluble. There are no very high to high perceived risks to human health or the environment from any of the potential contamination sources from the site or adjoining areas. There is a moderate perceived risk to human health and/or environmental receptors within the inundation extent from contaminated soils, sediments and surface water during construction and operation of the project to the following receptors:
· Exposure of construction workers · Beneficial users of dam water (agriculture) · Environmental receptors · Future recreational users The moderate risk is generally associated with the potential for more widespread operations associated with arsenic mining (compared to the more localised tin mining operations) and the potential for ingestion of contamination (e.g. bio-magnification of contamination in fish for consumption and use of contaminated water for irrigation of crops and watering of livestock).
To quantify these potential risks, it is recommended that a sampling and analysis program be developed which targets potential contamination sources which could be disturbed as part of construction and operation of the project.
H.9.4 Heritage Open sites of low-density artefact scatters are prevalent within the landscape and the literature indicates that other Aboriginal cultural material such as scarred trees are also evident within the area. Further investigation is recommended to determine the full extent of those scatters identified within the assessment area and identify any other Aboriginal cultural places, such as scarred trees, that are referred to in the literature. Most of the historic heritage previously reported within the assessment area has degraded to such a degree that that most evidence of the original structures is no longer evident. Upon searching the historic heritage databases only the
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Arsenic Mine is officially registered as a historic heritage item. The contaminated condition of the site, however, means that any scientific value ca only really be photographed or recorded visually with notes and any prospective development would necessitate rehabilitation of the environment in and around the mine.
Overall, the Aboriginal Heritage component of the assessment area requires further investigation while the non- Aboriginal heritage component includes only the Arsenic Mine as an officially listed heritage site.
.
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H.10 Flora and fauna database search results
Status No. records in Preliminary likelihood of Species name Common name Distribution and habitat EPBC locality occurrence TSC Act Act
Flora
Acacia macnuttiana McNutt's Wattle V V MacNutt's Wattle occurs only on the New England Tablelands and just extending onto the North West Slopes. Found in widely PMST Moderate – study area may scattered locations in the Tenterfield area and west to around Torrington. MacNutt's Wattle grows in dry forest or woodland and provide suitable habitat for this heath vegetation, usually on granite or metasediments and often near streams. species.
Acacia pubifolia Velvet Wattle V E Velvet Wattle occurs in NSW and QLD. In NSW it is known from two main populations, one north of Emmaville and the other near PMST Moderate – study area may Warrabah National Park. Velvet Wattle generally grows in dry shrubby woodland on granite and metasediment soils. provide suitable habitat for this species.
Almaleea cambagei Torrington Pea E V The majority of Almaleea cambagei populations occur within Torrington State Conservation Area on the New England Tablelands, PMST Low – unsuitable habitat in study with a few populations potentially occurring in the adjacent agricultural lands. The species is also reported from Girraween National area. Park in Queensland. It is known from fewer than 15 populations and has a highly restricted distribution with an extent of occurrence of approximately 88 square km. Usually grows in wet heath and acid swamp areas and along watercourses on granite, above 900 m altitude. Associated species include Baeckea omissa, Epacris microphylla, Callistemon sieberi, Leptospermum and Restio species.
Boronia granitica Granite Boronia E V Granite Boronia occurs in scattered localities on the New England Tablelands and North West Slopes north from the Armidale area PMST Moderate – study area may to the Stanthorpe district in southern Queensland. It can be locally common in appropriate habitat (e.g. Torrington). Grows on provide suitable habitat for this granitic soils amongst rock outcrops, often in rock crevices, and in forests and woodlands on granite scree and shallow soils. species. Important site characteristics include low precipitation and high levels of solar radiation. This semi-arid soil environment will have selected the more xerophytic species from the available regional assemblage of rainforest species.
Cadellia pentastylis Ooline V V Occurs along the western edge of the North West Slopes from north of Gunnedah to west of Tenterfield. Also occurs in Queensland. PMST Moderate – study area may The natural range of Ooline is from 24ºS to 30ºS in the 500 to 750 mm per annum rainfall belt. Forms a closed or open canopy provide suitable habitat for this mixing with eucalypt and cypress pine species. There appears to be a strong correlation between the presence of Ooline and low- to species. medium-nutrient soils of sandy clay or clayey consistencies, with a typical soil profile having a sandy loam surface layer, grading from a light clay to a medium clay with depth.
Dichanthium setosum Bluegrass V V Dichanthium setosum has been reported from mid-coastal to inland NSW and Queensland. Dichanthium setosum occurs on the PMST Moderate – study area may New England Tablelands, North West Slopes and Plains and the Central Western Slopes of NSW, extending west to Narrabri. provide suitable habitat for this Dichanthium setosum is associated with heavy basaltic black soils and red-brown loams with clay subsoil. species.
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Status No. records in Preliminary likelihood of Species name Common name Distribution and habitat EPBC locality occurrence TSC Act Act
Diuris pedunculata Small Snake Orchid E E Confined to north east NSW. It was originally found scattered from Tenterfield south to the Hawkesbury River, but is now mainly PMST Moderate – study area may found on the New England Tablelands, around Armidale, Uralla, Guyra and Ebor. The Small Snake Orchid grows on grassy slopes provide suitable habitat for this or flats. Often on peaty soils in moist areas. Also on shale and trap soils, on fine granite, and among boulders. species.
Eucalyptus caleyi Ovenden's Ironbark V V Eucalyptus caleyi subsp. ovendenii occurs from west of Guyra to west of Tenterfield on the New England Tablelands of NSW. PMST Moderate – study area may subsp. ovendenii Localities include ‘Moorabinda’ station and the western half of Torrington State Conservation Area. Grows in grassy woodland on provide suitable habitat for this dry, shallow soils of moderate fertility. Associated species include Eucalyptus melliodora, Eucalyptus dealbata, Eucalyptus albens, species. Eucalyptus melanophloia and Geijera parviflora.
Eucalyptus nicholii Narrow-leaved V V This species is sparsely distributed but widespread on the New England Tablelands from Nundle to north of Tenterfield, being most PMST Moderate – study area may Black Peppermint common in central portions of its range. Found largely on private property and roadsides, and occasionally conservation reserves. provide suitable habitat for this Planted as urban trees, windbreaks and corridors. Typically grows in dry grassy woodland, on shallow soils of slopes and ridges. species. Found primarily on infertile soils derived from granite or metasedimentary rock.
Grevillea beadleana Beadle’s Grevillea E E Known from four separate areas, all in north-east NSW: the Torrington area west of Tenterfield, Oxley Wild Rivers National Park, PMST Moderate – study area may Guy Fawkes River National Park and at Shannon Creek south-west of Grafton. Open eucalypt forest with a shrubby understorey. It provide suitable habitat for this is usually found on steep granite slopes at high altitudes, although the population at Shannon Creek is at a lower elevation on species. sandstone.
Lepidium peregrinum Wandering Pepper- E E Thought to be extinct until recently rediscovered in NSW and Queensland. Targeted searches conducted in 2001 confirmed the PMST Moderate – study area may cress species occurs in scattered refugia in north-eastern NSW (near Tenterfield) and south-eastern Queensland. The largest site provide suitable habitat for this containing most of the known Lepidium peregrinum population is in a designated Travelling Stock Reserve. The largest population of species. Wandering Pepper Cress occurs in an open riparian forest on the banks of the Tenterfield creek at Clifton. Sandy alluvium is the main soil type at the site.
Prasophyllum petilum Tarengo Leek E E Natural populations are known from a total of five sites in NSW. These area at Boorowa, Captains Flat, Ilford, Delegate and a newly PMST Moderate – study area may Orchid recognised population c.10 k SE of Muswellbrook. Grows in open sites within Natural Temperate Grassland at the Boorowa and provide suitable habitat for this Delegate sites. Also grows in grassy woodland in association with River Tussock Poa labillardieri, Black Gum Eucalyptus aggregata species. and tea-trees Leptospermum spp. at Captains Flat and within the grassy groundlayer dominated by Kanagroo Grass under Box- Gum Woodland at Ilford (and Hall, ACT).
Prasophyllum sp. CE - Endemic to NSW, it is known from near Ilford, Premer, Muswellbrook, Wybong, Yeoval, Inverell, Tenterfield, Currabubula and the PMST Moderate – study area may Wybong (C.Phelps Pilliga area. A perennial orchid, appearing as a single leaf over winter and spring. Flowers in spring and dies back to a dormant provide suitable habitat for this ORG 5269) tuber over summer and autumn. Known to occur in open eucalypt woodland and grassland. species.
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Status No. records in Preliminary likelihood of Species name Common name Distribution and habitat EPBC locality occurrence TSC Act Act
Prostanthera Torrington Mint- V E Currently known from a single granite outcrop in the Tenterfield area of the New England Tablelands. Within its only current known PMST Low – unsuitable habitat in study staurophylla bush population, the species occurs in shallow skeletal soil in rock crevices. The site is an exposed granite outcrop near the mountain area. summit, with skeletal gritty loam soil. Kunzea parvifolia is dominant around the outcrop, with Prostanthera staurophylla and Leptospermum variabile scattered amongst the Kunzea.
Rutidosis heterogama Heath Wrinklewort V V Recorded from near Cessnock to Kurri Kurri with an outlying occurrence at Howes Valley. On the Central Coast it is located north PMST Moderate – study area may from Wyong to Newcastle. There are north coast populations between Wooli and Evans Head in Yuraygir and Bundjalung National provide suitable habitat for this Parks. It also occurs on the New England Tablelands from Torrington and Ashford south to Wandsworth south-west of Glen Innes. species. Grows in heath on sandy soils and moist areas in open forest, and has been recorded along disturbed roadsides.
Thesium australe Austral Toadflax V V Found in very small populations scattered across eastern NSW, along the coast, and from the Northern to Southern Tablelands. It is PMST Moderate – study area may also found in Tasmania and Queensland and in eastern Asia. Occurs in grassland on coastal headlands or grassland and grassy provide suitable habitat for this woodland away from the coast. Often found in association with Kangaroo Grass (Themeda australis). species.
Tylophora linearis E V Majority of records occur in the central western region. Records from Goonoo, Pillaga West, Pillaga East, Bibblewindi, Cumbil and PMST Moderate – study area may Eura State Forests, Coolbaggie NR, Goobang NP and Beni SCA. Grows in dry scrub and open forest. Recorded from low-altitude provide suitable habitat for this sedimentary flats in dry woodlands of Eucalyptus fibrosa, Eucalyptus sideroxylon, Eucalyptus albens, Callitris endlicheri, Callitris species. glaucophylla and Allocasuarina luehmannii. Also grows in association with Acacia hakeoides, Acacia lineata, Melaleuca uncinata, Myoporum species and Casuarina species.
Tylophora woollsii Cryptic Forest E E The Cryptic Forest Twiner is found from the NSW north coast and New England Tablelands to southern Queensland, but is very rare PMST Low – unsuitable habitat in study Twiner within that range. Known on the Tablelands from the Bald Rock and Boonoo Boonoo areas north of Tenterfield. This species grows area. in moist eucalypt forest, moist sites in dry eucalypt forest and rainforest margins. * Distribution and habitat requirement information adapted from: Australian Government Department of the Environment http://www.environment.gov.au/biodiversity/threatened/index.html NSW Office of Environment and Heritage http://www.environment.nsw.gov.au/threatenedspecies/ Department of Primary Industries – Threatened Fish and Marine Vegetation http://pas.dpi.nsw.gov.au/Species/All_Species.aspx + Data source includes Number of records from the NSW Office of Environment and Heritage Wildlife Atlas record data (Accessed November 2012); and Identified from the Protected Matters Search Tool (PMST) Australian Government Department of Sustainability, Environment, Water, Populations and Community http://www.environment.gov.au/epbc/pmst/index.html Key: EP = endangered population
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Status No. records in Preliminary likelihood of Species name Common name Distribution and habitat EPBC locality occurrence TSC Act Act
CE = critically endangered E = endangered V = vulnerable M = migratory
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Appendix I. Cost Estimate Schedules
I.1 Cost Estimate for Rockfill Dam
Item Rate MEERA Description Unit Qty Cost Sub-total Cost Sub-total Cost Sub-total No. (2017)
100 GL 200 GL 300 GL 100 GL 200 GL 300 GL
1 DAM WALL & SADDLE DAMS 1.1 Zone 1 (Earthfill) win/place m³ 427,000 561,000 $40 $11,360,000 $17,080,000 $22,440,000 284,000 1.2 Zone 2 (Filter) - win/import/place m³ 146,000 191,000 $80 $7,760,000 $11,680,000 $15,280,000 97,000 Zone 3A (Earth & Rockfill) - 1.3 m³ 1,484,000 1,947,000 $60 $59,220,000 $89,040,000 $116,820,000 win/import/place 987,000 1.4 Zone 4 (Riprap) - win/sort/place m³ 13,300 17,500 $40 $356,000 $532,000 $700,000 8,900 1.5 Spoil unsuitable excavations to stockpile m³ 286,000 343,000 $20 $4,340,000 $5,720,000 $6,860,000 217,000 1.6 Cut-off Trench Foundation Preparation item 1 1 1 $230,210 $220,000 $250,000 $300,000 1.7 Foundation Grouting bags 5,800 5,800 $270 $1,566,000 $1,566,000 $1,566,000 5,800 1.8 Grout Cap m³ 1,225 1,325 $660 $709,500 $808,500 $874,500 1,075 1.9 Dental Concrete m³ 14,300 17,100 $570 $6,213,000 $8,151,000 $9,747,000 10,900 1.10 Crest Roadway m³ 1,401 1,524 $80 $99,360 $112,080 $121,920 1,242 1.11 Roadway Sealing m² 2,300 2,500 $10 $21,000 $23,000 $25,000 2,100 1.12 Roadway Guardrail - Main Dam m 930 1,020 $180 $149,400 $167,400 $183,600 830 1.13 U/S Seepage Blanket - Main Dam m 490 530 $160 $68,800 $78,400 $84,800 430 1.14 D/S Toe Drain - Main & Saddle Dams m 490 530 $130 $55,900 $63,700 $68,900 430 1.15 D/S Slopes Topsoiling/Grassing m² 32,000 38,000 $8 $182,400 $243,200 $288,800 24,000 $92,321,000 $135,515,000 $175,361,000 2 SPILLWAY & APPURTENANT WORKS 2.1 Excavation m³ 1,510,000 1,042,000 $20 $54,800,000 $30,200,000 $20,840,000 2,740,000 2.2 Control Crest m³ 1,000 1,000 $880 $880,000 $880,000 $880,000 1,000 Preparation of Floors (incl. anchorage & 2.3 m² 31,400 29,500 $180 $6,318,000 $5,652,000 $5,310,000 drainage) 35,100 2.4 Preparation for Walls (incl. anchorage & m² 3,800 3,800 $120 $540,000 $456,000 $456,000
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drainage) 4,500
2.5 Concrete supply m³ 17,200 16,300 $340 $6,596,000 $5,848,000 $5,542,000 19,400 2.6 FWG Trashrack Structure (Concrete) item 1 1 $49,640 $49,640 $49,640 $49,640 1 2.7 Sloping Spillway Section item 300 300 $1,160 $348,000 $348,000 $348,000 300 2.8 Apron Concrete (incl. dissipator blocks) item 650 650 $1,160 $754,000 $754,000 $754,000 650 2.9 Training Walls - Intermediate Section item 2 2 $413,300 $826,600 $826,600 $826,600 2 2.10 Training Walls - Apron Section item 2 2 $826,590 $1,653,180 $1,653,180 $1,653,180 2 2.11 Excavation - D/S Discharge Pit m³ 14,000 14,000 $8 $110,600 $110,600 $110,600 14,000 2.12 Rockfill Protection - D/S Discharge Pit m² 1,000 1,000 $120 $120,000 $120,000 $120,000 1,000 2.13 Fish Passage (per vertical metre) m 60 68 $300,000 $15,000,000 $18,000,000 $20,250,000 50 $87,996,000 $64,898,000 $57,140,000 3 M&E ITEMS - GATES Fixed Wheel Gates (FWGs) - Outlet 3.1 item 2 2 $63,790 $127,580 $127,580 $127,580 Works 2 3.2 Outlet Conduit - FWGs item 1 1 $177,810 $177,810 $177,810 $177,810 1 $305,000 $305,000 $305,000 4 M&E ITEMS - OTHER 4.1 FWG Hoists (Winches) item 2 2 $29,140 $58,280 $58,280 $58,280 2 4.2 FWG Hoist Portal Frames item 2 2 $26,740 $53,480 $53,480 $53,480 2 4.3 FWG Guides item 4 4 $9,020 $36,080 $36,080 $36,080 4 Water Supply Conduit, Slide Gates, 4.4 item 1 1 $421,810 $421,810 $421,810 $421,810 Valves 1 4.5 Trashracks - Water Supply item 5 5 $7,790 $38,950 $38,950 $38,950 5 4.6 Trashrack Guides - Water Supply item 2 2 $9,020 $18,040 $18,040 $18,040 2 4.7 Riparian Outlet Pipes, Valves, etc. (RHS) item 1 1 $273,610 $273,610 $273,610 $273,610 1 4.8 Misc. Valves & Minor Pipework, etc. item 1 1 $54,670 $54,670 $54,670 $54,670 1 4.9 Electrical Works - General item 1 1 $311,260 $311,260 $311,260 $311,260 1 4.10 Control Boxes item 4 4 $12,470 $49,880 $49,880 $49,880 4 4.11 Pump Station - Water Supply item 1 1 $330,640 $330,640 $330,640 $330,640 1 4.12 Conduit Connection to Pump Station item 1 1 $95,800 $95,800 $95,800 $95,800 1
IS207200-0000-ZM-RPT-0001 I-2 Feasibility Study Report
$1,743,000 $1,743,000 $1,743,000 5 MISCELLANEOUS 5.1 Fencing & Gates item 1 1 $211,740 $211,740 $211,740 $211,740 1 5.2 Instrumentation item 1 1 $301,430 $301,430 $301,430 $301,430 1 5.3 Seepage Weir - Main Dam item 1 1 $19,300 $19,300 $19,300 $19,300 1 5.4 Seepage Weirs - Saddle Dams item 3 3 $9,640 $28,920 $28,920 $28,920 3 5.5 Storage Level Recording System item 1 1 $7,540 $7,540 $7,540 $7,540 1 5.6 SCADA item 1 1 $88,370 $88,370 $88,370 $88,370 1 Misc. Stairs, Ladders, Platforms, 5.7 item 1 1 $53,720 $53,720 $53,720 $53,720 Metalwork 1 $711,000 $711,000 $711,000 6 ROADS Site access Roads, 6m wide asphalt 6.1 m 750 750 $110 $82,500 $82,500 $82,500 surfaced 750 Gravel roads to be relocated - Johnstons 6.2 m 7,200 7,200 $110 $792,000 $792,000 $792,000 Rd 7,200 Gravel roads to be relocated - Upper 6.3 m 3,800 3,800 $110 $418,000 $418,000 $418,000 Mole River Rd 3,800 $1,293,000 $1,293,000 $1,293,000
7 STRUCTURES SUBTOTAL (PC1) $184,369,000 $204,465,000 $236,553,000
8 PRELIMINARIES & DIVERSIONS 8.1 Establishment/Disestablishment 20.00% $36,873,800 $40,893,000 $47,310,600 8.2 Environmental Management 0.75% $1,382,768 $1,533,488 $1,774,148 Safety & Construction Traffic 8.3 0.75% $1,382,768 $1,533,488 $1,774,148 Management 8.4 Diversion/Stream Care 1.00% $1,843,690 $2,044,650 $2,365,530 Other Diversion Works (Channel & 8.5 1.00% $1,843,690 $2,044,650 $2,365,530 Conduit) $43,327,000 $48,049,000 $55,590,000
9 TOTAL PRIME COST (PC) $227,696,000 $252,514,000 $292,143,000
10 NON-CONSTRUCTION INTANGIBLES 15.50% $35,293,000 $39,140,000 $45,282,000 (NCIs)
IS207200-0000-ZM-RPT-0001 I-3 Feasibility Study Report
11 ENVIRONMENTAL OFFSETS Ha 1,050 1,163 $20,000 $13,800,000 $21,000,000 $23,260,000 690 $13,800,000 $21,000,000 $23,260,000
12 CONTINGENCIES 30.00% $68,309,000 $75,754,000 $87,643,000 (30% of PC)
13 TOTAL PROJECT COST $345,098,000 $388,408,000 $448,328,000
IS207200-0000-ZM-RPT-0001 I-4 Feasibility Study Report
I.2 Cost Estimate for Roller-compacted Concrete Dam
Item MEERA Description Unit Qty Rate (2017) Cost Sub-total Cost Sub-total Cost Sub-total No.
100 GL 200 GL 300 GL 100 GL 200 GL 300 GL
1 DAM WALL
1.1 Excavation for dam wall m³ 56,860 68,360 $20 $862,000 $1,137,200 $1,367,200 43,100 1.2 Foundation Curtain Grouting bags 7,500 7,500 $270 $2,025,000 $2,025,000 $2,025,000 7,500 1.3 Grout Cap m³ 750 750 $660 $495,000 $495,000 $495,000 750 1.4 Blanket or Extra Grouting item 1 1 $1,299,720 $1,299,720 $1,299,720 $1,299,720 1 1.5 Drainage m 3,650 3,650 $180 $657,000 $657,000 $657,000 3,650 1.6 RCC in Dam m³ 419,060 549,760 $310 $86,211,000 $129,908,600 $170,425,600 278,100 1.7 U/S Facing Concrete (GERCC) m³ 18,214 21,880 $400 $5,520,400 $7,285,600 $8,752,000 13,801 1.8 D/S Facing Concrete (GERCC) m³ 27,321 32,820 $400 $8,280,600 $10,928,400 $13,128,000 20,702 1.9 Gallery Concrete m³ 3,200 3,200 $1,160 $3,712,000 $3,712,000 $3,712,000 3,200 1.10 Crest Road Surface Seal m² 2,808 3,060 $10 $24,840 $28,080 $30,600 2,484 1.11 Guardrailing m 936 1,020 $180 $149,040 $168,480 $183,600 828 1.12 Intake Tower Base Concrete m³ 500 500 $960 $480,000 $480,000 $480,000 500 1.13 Intake Tower Concrete m³ 600 600 $1,820 $1,092,000 $1,092,000 $1,092,000 600 1.14 Downstream Apron Slab (incl. anchors) item 1 1 $826,590 $826,590 $826,590 $826,590 1 1.15 Cut-Off m³ 60 60 $960 $57,600 $57,600 $57,600 60 $111,693,000 $160,101,000 $204,532,000 2 APPURTENANT WORKS
2.1 Baulks for Intakes item 36 36 $32,610 $1,173,960 $1,173,960 $1,173,960 36 2.2 Trashracks for Intakes item 6 6 $19,180 $115,080 $115,080 $115,080 6 2.3 Baulks/Trashracks Lifting Frame item 1 1 $14,150 $14,150 $14,150 $14,150 1 2.4 Bulkhead Gate & Lifting Frame item 1 1 $59,470 $59,470 $59,470 $59,470 1 2.5 Valve Block/House item 1 1 $820,840 $820,840 $820,840 $820,840 1
IS207200-0000-ZM-RPT-0001 I-5 Feasibility Study Report
2.6 Control House (Operations) item 1 1 $129,970 $129,970 $129,970 $129,970 1 2.13 Fish Passage (per vertical metre) m 60 68 $300,000 $15,000,000 $18,000,000 $20,250,000 50 $17,313,000 $20,313,000 $22,563,000 3 SPILLWAY
3.1 Control Crest m³ 1,020 1,020 $880 $897,600 $897,600 $897,600 1,020 3.2 Floor Slabs (incl. anchorage & drainage) m² 17,000 17,000 $320 $5,440,000 $5,440,000 $5,440,000 17,000 3.3 Wall Slabs (incl. anchorage & drainage) m² 7,000 7,000 $390 $2,730,000 $2,730,000 $2,730,000 7,000 3.4 Cut-Off/ Flip Bucket m³ 36 36 $960 $34,560 $34,560 $34,560 36 3.5 Downstream apron slab Item 1 1 $19,843,450 $19,843,450 $19,843,450 $19,843,450 1 3.6 Downstream training walls Item 2 2 $2,755,300 $5,510,600 $5,510,600 $5,510,600 2 $34,456,000 $34,456,000 $34,456,000 4 M&E ITEMS
4.1 Outlet Penstocks - 900 dia. item 2 2 $287,280 $574,560 $574,560 $574,560 2 4.2 Guard Valve ( Butterfly) - 900mm item 2 2 $180,570 $361,140 $361,140 $361,140 2 4.3 Outlet Valves (FDCV) - 750mm item 2 2 $235,360 $470,720 $470,720 $470,720 2 4.4 Outlet Valves (FDCV) - 300mm item 1 1 $123,140 $123,140 $123,140 $123,140 1 4.5 Misc. Valves & Minor Pipework, etc. item 1 1 $177,810 $177,810 $177,810 $177,810 1 4.6 Valve House Gantry Crane - 10t travelling item 1 1 $207,790 $207,790 $207,790 $207,790 1 4.7 Misc. Equipment - pumps, ventilation, etc. item 1 1 $333,680 $333,680 $333,680 $333,680 1 $2,249,000 $2,249,000 $2,249,000 5 MISCELLANEOUS
5.1 Fencing & Gates item 1 1 $324,690 $324,690 $324,690 $324,690 1 5.2 Instrumentation item 1 1 $188,360 $188,360 $188,360 $188,360 1 5.3 Seepage Weir item 1 1 $30,330 $30,330 $30,330 $30,330 1 5.4 Storage Level Recording System item 1 1 $23,860 $23,860 $23,860 $23,860 1 5.5 Lift item 1 1 $553,700 $553,700 $553,700 $553,700 1 5.6 SCADA item 1 1 $147,240 $147,240 $147,240 $147,240 1 5.7 Misc. Stairs, Ladders, Platforms, Metalwork item 1 1 $268,460 $268,460 $268,460 $268,460 1
IS207200-0000-ZM-RPT-0001 I-6 Feasibility Study Report
5.8 Electrical Works item 1 1 $622,640 $622,640 $622,640 $622,640 1 $2,159,000 $2,159,000 $2,159,000 6 ROADS Site access Roads, 6m wide asphalt 6.1 m 735 735 $110 $80,850 $80,850 $80,850 surfaced 735 Gravel roads to be relocated - Johnstons 6.2 m 7,200 7,200 $110 $792,000 $792,000 $792,000 Rd 7,200 Gravel roads to be relocated - Upper Mole 6.3 m 3,800 3,800 $110 $418,000 $418,000 $418,000 River Rd 3,800 $1,291,000 $1,291,000 $1,291,000
7 STRUCTURES SUBTOTAL (PC1) $169,161,000 $220,569,000 $267,250,000
8 PRELIMINARIES & DIVERSIONS 8.1 Establishment/Disestablishment 20.00% 0 $36,873,800 $40,893,000 $47,310,600 8.2 Environmental Management 0.75% 0 $1,382,768 $1,533,488 $1,774,148 8.3 Safety & Construction Traffic Management 0.75% 0 $1,382,768 $1,533,488 $1,774,148 8.4 Diversion/Stream Care 1.00% 0 $1,843,690 $2,044,650 $2,365,530 8.5 Other Diversion Works (Tunnel, Plug, etc.) 1.00% 1 $1,843,690 $2,044,650 $2,365,530 $43,327,000 $48,049,000 $55,590,000
9 TOTAL PRIME COST (PC) $212,488,000 $268,618,000 $322,840,000
10 NON-CONSTRUCTION INTANGIBLES 15.50% 0 $32,936,000 $41,636,000 $50,040,000 (NCIs)
11 ENVIRONMENTAL OFFSETS Ha 1,050 1,163 $20,000 $13,800,000 $21,000,000 $23,260,000 690 $13,800,000 $21,000,000 $23,260,000
11 CONTINGENCIES 30.00% 0 $63,746,000 $80,585,000 $96,852,000 (30% of PC)
12 TOTAL PROJECT COST $322,970,000 $411,839,000 $492,992,000
IS207200-0000-ZM-RPT-0001 I-7 Feasibility Study Report
Appendix K. Concept design drawing – BRC, 1990
IS207200-0000-ZM-RPT-0001 K-1
Feasibility Study Report
Appendix L. Concept design – Jacobs, 2017
IS207200-0000-ZM-RPT-0001 L-1 Capacity (ML) Full Supply Dam Crest Spillway Crest Length Level (mAHD) Level (mAHD) Length (m) (m)
PROTECTION WORKS Option 1 100,000 473.0 485.0 59 414
SPILLWAY
MOLE RIVER
EXISTING TRACK
DAM EMBANKMENT
OUTLET STRUCTURE
INLET TOWER
BRIDGE
INLET AND OUTLET PLAN STRUCTURES NOT SHOWN SCALE 1:2000
CLIENT WATERNSW TITLE PROJECT UPPER MOLE RIVER DAM - 100GL OPTION MOLE RIVER DAM FEASIBILITY STUDY GENERAL ARRANGEMENT
B 14/09/2017 LH MB SM FINAL ABN 37 001 024 095 and ACN 001 024 095 DRAWN DRAWING CHECK REVIEWED APPROVED Jacobs Group (Australia) Pty Ltd L. HELLBERG A 30/07/17 LH DRAFT 11th Floor, 452 Flinders Street Tel: +61 3 8668 3000 MELBOURNE, VIC 3000 Fax: +61 3 8668 3001 DESIGNED DESIGN REVIEW SCALE DRAWING No REV AUSTRALIA Web: www.jacobs.com REV DATE DRAWN REV'D APP'D REVISION DRAWING NUMBER REFERENCE DRAWING TITLE A. FARHADI DATE DATE 1:2000 IS207200-0000-CI-DG-0001 B NSL CL Chute wall
WEATHERED ROCK FSL 473.0 EL 461.0
Ogee spillway Plunge pool Chute El 420 Flip bucket
LONGITUDINAL SECTION THROUGH SPILLWAY SCALE 1:2000
10 Crest level - 485mAHD 1.5 1 Earthfill core 1.5 2A Fine filter FSL - 473mAHD 2B Coarse Filter 1.75 3 Rockfill 4 Rip rap 1 1.75 1 GROUND LEVEL 1 1
Unlined spillway wall WEATHERED ROCK 0.3 0.3 Outlet Structure
Concrete-lined spillway wall Cofferdam Channel invert level - 435mAHD
2 2 1 Ogee spillway 1 Mudstone / siltstone Grout curtain
TYPICAL SECTION FOR 100GL OPTION SCALE 1:1000
SECTION THROUGH SPILLWAY SCALE 1:2000
Capacity (ML) Full Supply Dam Crest Spillway Crest Length Level (mAHD) Level (mAHD) Length (m) (m)
Option 1 100,000 473.0 485.0 59 414
CLIENT WATERNSW TITLE PROJECT UPPER MOLE RIVER DAM - 100GL OPTION MOLE RIVER DAM FEASIBILITY STUDY GENERAL ARRANGEMENT
ABN 37 001 024 095 and ACN 001 024 095 DRAWN DRAWING CHECK REVIEWED APPROVED Jacobs Group (Australia) Pty Ltd L. HELLBERG A 30/07/17 LH DRAFT 11th Floor, 452 Flinders Street Tel: +61 3 8668 3000 MELBOURNE, VIC 3000 Fax: +61 3 8668 3001 DESIGNED DESIGN REVIEW SCALE DRAWING No REV AUSTRALIA Web: www.jacobs.com REV DATE DRAWN REV'D APP'D REVISION DRAWING NUMBER REFERENCE DRAWING TITLE A. FARHADI DATE DATE AS SHOWN IS207200-0000-CI-DG-0002 B