MUDGEE STONE COMPANY PTY LTD
ABN: 89 100 974 365
Oberon White Granite Quarry
Surface Water Assessment
Prepared by
GSS Environmental ABN 47 059 448 323
Specialist Consultant Studies Compendium
Part 1
November 2010 This page has intentionally been left blank SPECIALIST CONSULTANT STUDIES 1 - 1 MUDGEE STONE COMPANY PTY LTD Part 1: Surface Water Assessment Oberon White Granite Quarry Report No. 709/03
MUDGEE STONE COMPANY PTY LTD ABN: 89 100 974 365
Oberon White Granite Quarry
Surface Water Assessment
Prepared for: R.W. Corkery & Co. Pty. Limited 12 Dangar Road PO Box 239 BROOKLYN NSW 2083
Tel: (02) 9985 8511 Fax: (02) 9985 8208 Email: [email protected]
On behalf of: Mudgee Stone Company Pty Ltd PO Box 342 MUDGEE NSW 2850
Tel: (02) 6373 3939 Fax: (02) 6373 3766 Email: [email protected]
Prepared by: GSS Environmental Pty Ltd PO Box 907 HAMILTON NSW 2303
Tel: (02) 4920 3000 Fax: (02) 4961 3360 Mob: (0407) 910 841 Email: [email protected]
November 2010
GSS Environmental MUDGEE STONE COMPANY PTY LTD 1 - 2 SPECIALIST CONSULTANT STUDIES Oberon White Granite Quarry Part 1: Surface Water Assessment Report No. 709/03
FOREWORD
This Surface Water Assessment details the existing surface water environment, potential impacts and operational safeguards with regards to surface water management in relation to the proposed extension of existing extraction operations and increased production at the Oberon White Granite Quarry, located approximately 6km east-south east of Oberon, NSW. This report has been prepared in accordance with the “Brief for a Surface Water Assessment for an Environmental Assessment”, provided to GSS Environmental (GSSE) by R.W. Corkery & Co. Pty. Limited, relevant requirements provided within the Director-General’s Requirements issued by the Department of Planning for the Project and relevant guidelines.
COPYRIGHT
© GSS Environmental, 2010 and © Mudgee Stone Company Pty Ltd, 2010
All intellectual property and copyright reserved.
Apart from any fair dealing for the purpose of private study, research, criticism or review, as permitted under the Copyright Act, 1968, no part of this report may be reproduced, transmitted, stored in a retrieval system or adapted in any form or by any means (electronic, mechanical, photocopying, recording or otherwise) without written permission. Enquiries should be addressed to GSS Environmental.
GSS Environmental SPECIALIST CONSULTANT STUDIES 1 - 3 MUDGEE STONE COMPANY PTY LTD Part 1: Surface Water Assessment Oberon White Granite Quarry Report No. 709/03 CONTENTS Page
1 INTRODUCTION ...... 1-7 1.1 OVERVIEW ...... 1-7 1.2 SCOPE OF THIS REPORT ...... 1-7
2 LITERATURE REVIEW ...... 1-11
3 DIRECTOR-GENERAL’S REQUIREMENTS ...... 1-12
4 STUDY AREA ...... 1-14
5 METHODOLOGY ...... 1-14
6 SURFACE WATER ENVIRONMENT ...... 1-15 6.1 RAINFALL/CLIMATE ...... 1-15 6.2 LANDFORM ...... 1-16 6.3 VEGETATION ...... 1-16 6.4 SURROUNDING LAND USES ...... 1-17 6.5 SOILS/GEOLOGY ...... 1-17 6.6 SURFACE HYDROLOGY ...... 1-19 6.6.1 Regional Hydrology ...... 1-19 6.6.2 Local Hydrology ...... 1-19 6.7 SURFACE WATER QUALITY ...... 1-21 6.7.1 Regional Water Quality ...... 1-21 6.7.2 Local Water Quality ...... 1-22 6.8 SURFACE WATER FEATURES OF CONSERVATION SIGNIFICANCE ...... 1-22 6.9 GROUNDWATER CONNECTIVITY ...... 1-23
7 RELEVANT LEGISLATION, POLICY AND GUIDELINES...... 1-24 7.1 POLICIES AND GUIDELINES ...... 1-24 7.2 LEGISLATION ...... 1-24
8 KEY ISSUES/CONSTRAINTS ...... 1-25
9 SOIL AND WATER MANAGEMENT PLAN ...... 1-26 9.1 INTRODUCTION ...... 1-26 9.2 SOIL AND WATER MANAGEMENT PRINCIPLES ...... 1-27 9.3 CATCHMENTS OF THE PROJECT SITE ...... 1-27 9.4 ASSESSMENT OF CONSTRAINTS ...... 1-29 9.4.1 Introduction ...... 1-29 9.4.2 Riparian Lands ...... 1-29
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9.4.3 Erosion (Rainfall Erosivity & Soil Erodibility) ...... 1-30 9.4.3.1 Rainfall Erosivity ...... 1-30 9.4.3.2 Soil Erodibility ...... 1-30 9.4.3.3 Soil Characteristics...... 1-30 9.4.4 Surface Water Runoff ...... 1-31 9.4.5 Groundwater ...... 1-31 9.5 SOIL AND WATER MANAGEMENT ...... 1-31 9.5.1 Objectives ...... 1-31 9.5.2 Soil BMPs ...... 1-32 9.5.2.1 Sources of Erosion and Sedimentation ...... 1-32 9.5.2.2 Minimal Disturbance ...... 1-32 9.5.2.3 Planning Considerations ...... 1-33 9.5.2.4 Handling and Stockpiling of Topsoil ...... 1-33 9.5.2.5 Soil Respreading ...... 1-34 9.5.3 Water BMPs ...... 1-34 9.5.3.1 Introduction ...... 1-34 9.5.3.2 Clean Water Diversion ...... 1-34 9.5.3.3 Dirty Water Capture and Settlement ...... 1-36 9.5.3.4 Additional Sediment Protection ...... 1-38 9.5.4 Recommended Rehabilitation Works ...... 1-39 9.5.4.1 Rehabilitation of the Southern Batter ...... 1-39 9.5.4.2 Rehabilitation of the Southern Retention Basin ...... 1-40 9.5.5 Summary ...... 1-40 9.5.6 Maximum Harvestable Right Dam Capacity ...... 1-41
10 SITE WATER BALANCE ...... 1-41 10.1 INTRODUCTION ...... 1-41 10.2 INPUTS ...... 1-41 10.2.1 Rainfall/Runoff ...... 1-41 10.2.2 Groundwater seepage ...... 1-42 10.3 OUTPUTS ...... 1-43 10.3.1 Evaporation losses ...... 1-43 10.3.2 Dust Suppression ...... 1-43 10.4 WATER BALANCE ...... 1-43
11 SURFACE WATER MONITORING PROGRAM ...... 1-44 11.1 INTRODUCTION ...... 1-44 11.2 MONITORING LOCATIONS ...... 1-44 11.3 MONITORING PARAMETERS ...... 1-45
12 REFERENCES ...... 1-47
GSS Environmental SPECIALIST CONSULTANT STUDIES 1 - 5 MUDGEE STONE COMPANY PTY LTD Part 1: Surface Water Assessment Oberon White Granite Quarry Report No. 709/03 CONTENTS Page
APPENDICES Appendix 1 Dam 1 Design Volume ...... 1-51 Appendix 2 Dam 1 Catchment Yield ...... 1-55 Appendix 3 Type F Dam Design ...... 1-59 Appendix 4 Earth Bank Diversion Design ...... 1-63 Appendix 5 Dam 2 Design Volume ...... 1-67
TABLES Table 1 Director General’s Requirements ...... 1-12 Table 2 Rainfall Data for Oberon (Jenolan Caves Road Station 063293) ...... 1-15 Table 3 Annual Rainfall Statistics (BOM Station No. 063293) ...... 1-16 Table 4 Soil sample field test results ...... 1-18 Table 5 Soil sample laboratory results ...... 1-19 Table 6 Water quality results ...... 1-23 Table 7 Study Area Catchments ...... 1-29 Table 8 Recommended pasture mix ...... 1-33 Table 9 Diversion Channels design specifications (based on Manning’s Equation) ...... 1-36 Table 10 Summary of dam volumes ...... 1-41 Table 11 Annual average runoff generated ...... 1-42 Table 12 Water balance for the Oberon White Granite Quarry ...... 1-43 Table 13 Proposed Monitoring Locations ...... 1-45 Table 14 Monitoring Parameters ...... 1-46
FIGURES Figure 1 Locality Plan ...... 1-8 Figure 2 Study Area and Local Hydrology ...... 1-9 Figure 3 Study Area Catchments and Proposed Water Management Structures ...... 1-28
PLATES Plate 1 Soil Sample 1 - wall of channel in the inlet to southern retention basin ...... 1-17 Plate 2 Soil Sample 2 – adjacent to existing access road ...... 1-18 Plate 3 Drainage line south of existing extraction area, flowing to the retention basin ...... 1-20 Plate 4 Existing southern retention basin ...... 1-20 Plate 5 Inlet to the existing retention basin ...... 1-21
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GSS Environmental SPECIALIST CONSULTANT STUDIES 1 - 7 MUDGEE STONE COMPANY PTY LTD Part 1: Surface Water Assessment Oberon White Granite Quarry Report No. 709/03 1 INTRODUCTION
1.1 Overview
The Oberon White Granite Quarry is located approximately 6km east-southeast of Oberon on the NSW Central Tablelands (see Figure 1). R. W. Corkery & Co. Pty. Limited (RWC) has been engaged by Mudgee Stone Company Pty Ltd (‘the Proponent”) to prepare an Environmental Assessment (EA) for a proposal to extend the extraction and processing operations (“the Project”). RWC has engaged GSS Environmental (GSSE) on behalf of the Proponent to prepare a Surface Water Assessment for the Project. The Surface Water Assessment will form part of the overall EA to be lodged with the project application.
The Proponent proposes to extend their existing extraction and processing operations within Lot 2 DP 1089826 (“the Project Site”). The current approved area of disturbance for the quarry is approximately 1.4ha with a maximum production level of 25 000t per year. The proposed extension of the quarry would progressively extend the existing approved extraction area approximately a further 150m to 200m to the north and east. Extraction would progressively increase up to 250 000t per year over approximately 5 years. The Project Site covers an area of approximately 40ha, and includes:
an extraction area of 6ha; a 20m wide area for construction of a safety bund and channel around the northern and eastern boundary of the proposed extraction area; a site access road, internal haul road and access track; soil and water management structures; and an office, amenities and stockpiling area (see Figure 2).
The Project Site is currently accessed by an approved transport route. The route includes approximately 600m of a right of carriageway (located within the Project Site) and Ferndale Road which extends from the northern boundary of the Project Site to Hampton Road. The quarry is located in a largely rural area although a number of rural-residential properties are also located near the Project Site. The predominant land use of surrounding properties is agricultural though native bushland is located within and to the east and west of the Project Site.
Free dig and drill and blast methods would continue to be used to extract the granite material which is directly loaded into a mobile crushing plant. The extraction area would be progressively rehabilitated to a safe and stable landform. Rehabilitation would aim to return as much of the disturbed land as possible to its undisturbed capability.
1.2 Scope of this Report
This document fulfils the requirements outlined in the “Brief for a Surface Water Assessment for an Environmental Assessment”, provided by RWC, to prepare a report detailing both the existing environment and constraints relating to surface water management for the Project, as well as the potential surface water impacts and operational safeguards to be implemented.
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Figure 1 Locality Plan A4 / B&W
GSS Environmental SPECIALIST CONSULTANT STUDIES 1 - 9 MUDGEE STONE COMPANY PTY LTD Part 1: Surface Water Assessment Oberon White Granite Quarry Report No. 709/03
Figure 2 Study Area and Local Hydrology A4 / Colour
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The scope of this report is as follows.
1. Literature review of any previous surface water studies carried out on the Project Site and surrounding area, including the identification of any water quality or quantity objectives for local and regional catchments (see Section 2 and 6.7.1 – note, however, that information obtained from the literature review is also used throughout the document). 2. Assess any available surface water quality and quantity monitoring data from the area and the site (see Section 6.7.2). 3. Identify, or compile, appropriate meteorological data for the assessment to ensure that the assessment accounts for dry, average and wet years (see Section 6.1). 4. Detail the methodology of the surface water assessment and any assumptions made during the assessment (see Section 5). 5. Determine the context of surface water on the Project Site including drainage lines and patterns, catchments (local and regional), surface water retention on site, water quality and adjacent users (see Section 6.6). 6. Determine any surface water / groundwater interaction (see Section 6.9). 7. Identify any surrounding land uses which use and/or impact on local surface water quality or quantity (see Section 6.4). 8. Identify the key issues and constraints to be addressed in this Surface Water Impact Assessment (see Section 8.0). 9. Undertake an assessment of the potential impact on the Project Site, local and regional surface water quality and quantity at different stages of the Project (see Section 9.5.5). 10. Undertake a cumulative impact assessment with respect to surrounding land users (see Section 6.9 and 9.5.5). 11. Outline appropriate safeguards and mitigation measures including erosion and sediment control measures, to alleviate potential impacts and/or meet appropriate criteria during establishment, operation and final land use (see Section 9.0). 12. Assess the compatibility of the Project and its potential impacts against any catchment management plans, water quality objectives and policies (see Section 6.7.1). 13. Identify the need for ongoing monitoring and outline appropriate monitoring locations and parameters (see Section 11).
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The following project-specific documentation has been reviewed by GSSE as part of the Surface Water Assessment.
Preliminary Project Outline and Environmental Assessment for the Oberon Granite Quarry Proposed Extension, Mudgee Stone Company Pty Ltd, (September 2007) - The Preliminary Project Outline and Environmental Assessment provides a preliminary description of the Project, and identifies the key environmental issues of the site. Oberon White Granite Quarry Proposed Extension, Project Update (January 2008) – A number of adjustments were made to the proposed site layout and minor operational changes to those outlined in the Preliminary Project Outline and Environmental Assessment. This document confirmed these changes, primarily relating to the location of the office and amenities area, product stockpiles and internal haul road. Erosion and Sediment Control Plan - Oberon Lot 13 DP 603429, Mudgee Stone Company Pty Ltd (August 2005) - The Erosion and Sediment Control Plan details the erosion and sediment controls currently in use on site, including the use of a clean water diversion system, a sediment retention basin at the southern end of the site, and a grass filter zone. Site stabilisation and long-term site rehabilitation methods are also detailed in the plan. Statement of Environmental Effects (SEE) – Oberon White Granite Quarry, Mudgee Stone Company Pty Ltd (July 2003) - The SEE provides an overview of the approved development including the extraction methods, transport of excavated materials, the effects on the environment and appropriate mitigation and controls. Catchment Action Plan (CAP), Central West Catchment Management Authority (February 2007) - The Project Site is situated in the far southeast of the area covered by the Central West Catchment Management Authority. The CAP provides general descriptions of the Central West Catchment, which includes the Macquarie, Castlereagh and Bogan Rivers and their tributaries. The CAP identifies catchment issues and sets measurable management targets with respect to land practices and water quality (e.g. turbidity, temperature, blue green algae blooms and hazardous chemicals). The CAP notes that high levels of turbidity, salinity and nutrients have generally been reported across the catchment. Sydney Water Corporation Five Year Drinking Water Quality Management Plan 2005-2010 (Nov 2005) - The Duckmaloi and Fish Rivers supplement supply to the Grose River Catchment which contributes to Sydney’s Water supply.
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In addition to the project-specific documentation, GSSE has also identified the following literature as being relevant to the Project.
Managing Urban Stormwater: Soils and Construction Vol 2E – Mines and Quarries (DECC, 2008) in conjunction with the references to Vol 1 (Landcom, 2004). Both of these references are referred to in this report as the “Blue Book”. NSW State Rivers and Estuaries Policy (1993). Australian and New Zealand Guidelines for Fresh and Marine Water Quality, ANZECC (2000).
3 DIRECTOR-GENERAL’S REQUIREMENTS
The following requirements relevant to the Surface Water Assessment have been provided by the Director-General of the Department of Planning, and relevant Government Authorities. These requirements are listed in Table 1, including where they are addressed in this report.
Table 1 Director General’s Requirements
Page 1 of 3 Condition Condition Requirement Section in Surface Water Assessment where addressed Director General’s Surface and Ground Water 9 Requirements Including details of surface and groundwater impacts and a site water balance: details of the proposed water management system including creek diversions and sediment/water supply dams: and a contingency strategy setting out the measures that would be implemented to minimise impacts on the supply of water (quality and quantity) to the environment and surrounding landowners. Department of Surface Water 9.5.3.2 Environment and Outline sediment/surface water controls along the two (2) ephemeral Climate Change creeks that flow towards the south below the quarry operations Surface Water 9.5.3.2 & Ensure: 9.5.3.3 There is no pollution of waters (including surface and groundwater); Polluted water is appropriately collected and either treated or removed from the site; and Sediment runoff is managed through permanent sediment and erosion controls Surface Water 9.5.3.4 Document the measures that will achieve the above outcomes in both the construction and operational phases of the development and identify proposed water pollution controls
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Table 1 (Cont’d) Director General’s Requirements
Page 2 of 3 Condition Condition Requirement Section in Surface Water Assessment where addressed Department of Surface Water 9 Water and Energy Provide the following: An assessment of the impact of the proposal on the existing flow 9.5.3.3 & 9.5.3.4 regime (ie. flow quantity, velocity, frequency and duration) for all rainfall events up to a 100 year Average Recurrence Interval
(ARI). An assessment of impact on the fluvial geomorphology of the 9.5.5 watercourse including any erosion and sedimentation likely to be caused by the development. Measures to be implemented to guard against actual and 9.5.3.2 & potential environmental disturbances during the construction 9.5.3.3 and operation of the proposal. This is to examine the existing
sedimentation being caused by the runoff from the waste rock piles and the access roads, and future sediment sources.
A water management plan, which includes the engineering, 9 geomorphic and ecosystem identification and protection principles.
Details of any proposed surface water extraction, including 10.0 & purpose, location of any existing pumps, dams, diversions, cuttings & levees on the site & expected annual extraction 9.5.5 volumes, from both on site interception and external sources
Identify sources of surface water, proportions of flow resulting 6.9, 9.3, from groundwater accessions, and measures to protect and enhance ecosystem integrity, and the geomorphic integrity of 9.5.6 affected streams above, within and below the project site.
The location and design specifications for all clean water 9.5.3.2 diversions including channels, detention basins and outlet fixtures.
The location and design specifications for dirty water / 9.5.3.3 & 9.5.3.4 contaminated water circuit including channels, detention basins
and outlet fixtures.
Details regarding any dirty water / contaminated discharge 5.6 resulting from the proposed development.
Information on detailed water balance including inflows and 10 imports / exports to and from the proposed development. Details of the integrated water management system, including 10 an assessment of changes to the water balance under a range of conditions (including 10%, 50% and 90% wet years and severe storm events). Details of proposed water storage structures, including purpose, 9.5.3.3 & 9.5.3.4 location, design specifications (crest, bywash, discharge, low flow bypass provisions).
Designs assessing any requirement for artificial geosynthetic NA lining and leakage collection/detection systems and should be in
accordance with the requirements of the NSW State
Groundwater Policy framework.
Calculation of the catchment area, water storage structure 9.3 & 10 capacity (ML) and water storage surface area.
Calculation of the Maximum Harvestable Right Dam Capacity 9.5.6 (MHRDC). Estimate the MHRDC as it changes over the life of the 9.5.6 operations.
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Table 1 (Cont’d) Director General’s Requirements
Page 3 of 3 Condition Condition Requirement Section in Surface Water Assessment where addressed Department of Surface Water Water and Energy Details of stream order (using the Strahler System). 6.6.2 Estimate of evaporation rates and annual evaporation losses. 10 Details of pumps and intended extraction volumes from the 10 water storage structure/s. Details of any other persons/ party to be supplied (eg. volume, NA rate, purpose). Identify impacts on other licence users or 'basic rights'. NA Erosion and Sediment Control Plan prepared in accordance the 9 guideline manual 'Managing Urban Stormwater Soils and Construction' (Landcom 2004). Assessment of salinity hazards. NA Monitoring and Contingency Planning 11 Provide the following.
Monitoring program for assessment on surface water Contingency plans, in the event that surface and/or ground water behaviour does not follow modelling predictions for the site. Contingency plans linked to the monitoring program, with trigger levels nominated in the EA for assessment against water management criteria in the catchment.
4 STUDY AREA
As discussed in Section 1.1, the Project Site is located within Lot 2 DP 1089826. The Study Area for this Surface Water Assessment incorporates the:
Project Site (area within the property boundary of Lot 2, DP 1089826); and off-site catchment areas that drain towards the Project Site.
The Study Area is shown in Figure 2.
5 METHODOLOGY
The Surface Water Assessment undertaken as part of the EA for the Project involves three key steps, as follows.
1. Site inspection of the Project Site – The site inspection was undertaken on 28th November 2007 by Nicole Reilly and Andrew Hutton (GSSE), Scott Hollamby (RWC) and Scott Murdoch (Mudgee Stone Company). This site inspection allowed GSSE to gain an understanding of the Project Site, and provided an opportunity to discuss surface water issues and possible control measures.
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2. Existing Environment and Constraints Report – This report provides a summary of the existing environment and constraints to the Project relating to the management of surface water on the Project Site. The report is based on both the findings of a literature review of previous studies carried out on the Project Site and surrounding area, as well as outcomes of the site inspection. This report also identifies the key issues and constraints relating to surface water to be addressed in the Surface Water Impact Assessment. The Existing Environment and Constraints Report is incorporated as Sections 1 to 8 of this report. 3. Surface Water Assessment – This assessment uses the findings of the site inspection and the Existing Environment and Constraints Report to make an assessment of the impacts on surface water of the Project and details appropriate safeguards and mitigation measures. The design of all recommended surface water and erosion control structures in this report is undertaken in accordance with Blue Book requirements. The Surface Water Assessment is incorporated as Sections 9 to 11 of this report.
6 SURFACE WATER ENVIRONMENT
6.1 Rainfall/Climate
There are two Bureau of Meteorology (BOM) monitoring stations operating in the Oberon area for which records are available. The two stations are located at Oberon (Springbank) and Oberon (Jenolan Caves Road). The Jenolan Caves Road station is considered more representative of the Project Site, as it is located closer to the Project Site (approximately 2.3km to the west) and is at approximately the same elevation (1 190m AHD).
Rainfall data collected over the last 17 years at the Oberon Jenolan Caves Road BOM station (Station No. 063293) is summarised in Table 2. Whilst rainfall is reasonably well distributed through the year, there is a peak in Summer, with the lowest rainfall months being in Autumn and Winter. On average, January is the wettest month and April the driest, with the area experiencing an average 126.5 days of rain per year, and a mean total annual rainfall of 736mm. Table 2 Rainfall Data for Oberon (Jenolan Caves Road Station 063293) Highest Lowest Highest Mean Rainfall Mean No Days Month Monthly Monthly Recorded Daily (mm) of Rain Rainfall (mm) Rainfall (mm) Rainfall (mm) Jan 85.7 205.0 19.4 119.0 10.3 Feb 74.7 212.9 9.6 71.8 10.3 Mar 53.4 216.6 4.4 45.8 9.2 Apr 43.8 227.1 2.4 54.0 7.2 May 45.3 130.8 1.6 36.8 9.9 Jun 55.4 109.0 0.0 42.8 12.1 Jul 60.6 108.2 19.0 33.4 13.6 Aug 61.9 192.2 6.0 72.0 11.9 Sep 59.9 135.4 10.0 76.6 12.5 Oct 57.8 186.4 5.6 53.8 8.9 Nov 75.4 139.8 14.4 49.0 11.3 Dec 66.2 153.6 10.2 35.6 9.3 Year 736 - - - 126.5
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The warmest month of the year is also January, which has a mean maximum temperature of 24.0 ºC, whilst July is the coolest month with a mean maximum temperature of 8.4 ºC. The climate of Oberon is cool with frosts common in Autumn, Winter and Spring. Several snowfalls are generally experienced each year in Oberon.
Table 3 contains the rainfall statistics for the 10th percentile (dry), 50th percentile (average) and 90th percentile (wet) rainfall years from the BOM Jenolan Caves Road meteorological station. This data has been used in the development of a simple water balance for the Project Site, and will assist in the design of appropriate sediment and erosion control structures for the site.
Table 3 Annual Rainfall Statistics (BOM Station No. 063293)
10th Percentile (dry year) 523.4 mm
50th Percentile (median year) 743.4 mm
90th Percentile (wet year) 929.7 mm
6.2 Landform
The Project Site is located in an elevated region known as the Oberon plateau on the western fall of the Great Diving Range. The Project Site is located approximately 6km east-southeast of the township of Oberon, with the general topography of the area higher in the north and sloping downward towards the south in the direction of the Duckmaloi River, which lies approximately 800m from the Project Site. The elevation of the Project Site varies between 1110m and 1200m (AHD), whilst elevations of the proposed extraction area vary between 1135m and 1190m (AHD). Natural slopes within the Project Site range between 3º in the north to 30º south of the existing extraction area. The existing extraction area forms an amphitheatre into the side of the plateau which faces out towards the south.
6.3 Vegetation
The Project Site is located within an 85 ha patch of remnant vegetation. Surrounding areas of the Oberon plateau are characterised by extensive grassland as a result of clearing after European settlement in the late nineteenth century. Vegetation adjacent to the right of carriageway in the north of the Project Site consists of open grassland dominated by grasses, clovers, flatweed and bracken fern. The northern section of the Project Site is occupied by partially cleared open woodland and an understorey of native herbs and grasses. The southern section of the Project Site is dominated by various eucalypt species. The proposed extraction area also consists of a grassy understorey inclusive of various small shrubs and a midstorey of Silver Wattle. Both introduced and native species are present throughout the Project Site. Further detail relating to the vegetation within the Project Site is presented within the Flora Assessment for the Project (see Part 3 of the Specialist Consultant Studies Compendium).
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The Project Site is located within a rural area, with the surrounding land use predominately agricultural. Dense native bushland is, however, located within and to the east and west of the Project Site. The agricultural land use in the area has the potential to impact upon local and regional water quality, with the Catchment Action Plan for the Central West Catchment Authority (February 2007) noting that high levels of turbidity, salinity and nutrients have been reported across the Central West Catchment.
6.5 Soils/Geology
The alaskite resource is a granite derivative developed within the Rossdhu Granite, a small granite batholith of Carboniferous age. Alaskite is a granitic rock composed mainly of quartz and alkali feldspar, with few dark mineral components. The Rossdhu Granite occupies a surface area of approximately 10km2 as shown on the Oberon 1:100 000 geological map.
The soils of the more densely vegetated areas of the Project Site have been classified as Sandy or Silty Loams and Silty Clays with moderate organic content. Soil thickness varies with the soil profile within some areas of the existing extraction area, stockpiling area and site access road the soil profile being poorly developed and identified as thin (less than 0.2 m thick) or rocky. The soils are characteristically well drained with low to moderate fertility. The type of soils and the moderate slopes indicate the soils within the Project Site are sensitive to erosion without implementation of appropriate surface water and erosion control measures. This has been taken into account in the design of appropriate surface water management controls detailed in Section 9.5.
During the site inspection conducted at the commencement of the Surface Water Assessment for the Project, two soil samples were collected and sent to a laboratory for analysis. The first sample (SS1) was collected from the wall of the channel in the inlet to the southern retention basin (refer Plate 1), with the second sample (SS2) collected from a sample pit dug adjacent to the existing access road (refer Plate 2). The soil sampling locations are presented in Figure 2.
Plate 1 Soil Sample 1 - wall of channel in the inlet to southern retention basin
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Plate 2 Soil Sample 2 – adjacent to existing access road
Prior to the soils being sent to the laboratory, a number of field tests were conducted by RWC together with a number of additional surface samples. The results of these tests are summarised below. Table 4 Soil sample field test results EA Class & Notes pH Texture Colour SS1 – near southern sediment retention basin 0cm – 15cm (Class 7) 5.0 Sandy Clay Loam – small Very dark brown. Partial slaking (subclass 1) gravel throughout, loose. 30cm – 40cm (Class 7) 5.0 Loam Fine Sandy - gritty Light brown. Moderate slaking (subclass 2) and some gravel, loose. 1.2m – 1.5m (Class 7) 5.0 Fine Sandy Clay Loam – Light brown / grey Complete slaking (subclass 2) some grit and gravel, loose. brown. SS2 – southern part of the existing access road 0cm – 15cm (Class 7) 5.5 Silty Clay Loam – some grit, Brown. Partial slaking, slight swell no gravel, loose. (subclass 0 to 1). 35cm – 40cm (Class 7) 5.5 Silty Clay – some grit and Light brown / reddy Moderate to complete slaking limited gravel, loose. brown. (subclass 2). SS3 – northern limit of approved extraction area 0cm – 30cm (Class 8) 5.5 Light Sandy Clay – very Light brown / grey. No slaking or swelling gritty, no gravel, loose. SS4 – northwest area of proposed extraction area 0cm – 30cm (Class 7) 6.0 Fine Sandy Clay Loam – Dark brown. No slaking, slight swelling. minor grit, no gravel, loose. SS5 – northeast area of proposed extraction area 0cm – 30cm (Class 7) 5.0 Sandy Clay Loam –some Dark brown. Partial slaking (subclass 0 to 1). grit, no gravel, loose. 30cm – 40cm (Class 7) 5.5 Sandy Clay Loam – very Light brown. Moderate to complete slaking gritty, some gravel, loose. (subclass 2). SS6 – proposed stockpiling area 0-10cm (Class 7) 4.5 Light Sandy Clay Loam – Light brown. No slaking, slight swelling. some grit, no gravel, loose. Underlain by consolidated material.
GSS Environmental SPECIALIST CONSULTANT STUDIES 1 - 19 MUDGEE STONE COMPANY PTY LTD Part 1: Surface Water Assessment Oberon White Granite Quarry Report No. 709/03 The results of the laboratory analysis are summarised in the table below.
Table 5 Soil sample laboratory results
Lab Method C1A/4 C2A/3 P7B/1 Particle Size Analysis (%) P8A/2 P9B/2 No. Sample Id EC pH clay silt Very fine Coarse coarse gravel D% EAT (dS/m) sand fine sand sand 1 Oberon SS1 0-15cm 0.01 5.4 8 15 11 7 42 17 0 3(1) 2 Oberon SS1 30-40cm <0.01 5.4 15 14 12 9 32 18 25 5 3 Oberon SS1 120-150cm <0.01 5.6 11 14 16 9 42 8 44 5 4 Oberon SS2 0-15cm 0.02 5.7 is Is is is is 0 is 5 5 Oberon SS2 35-40cm <0.01 5.5 24 21 20 9 24 2 20 5
The laboratory results detailed in Table 5 indicate that the soil samples collected at SS1 (from the southern retention basin) are Type C soils. That is, less than 33 percent of the soil materials are finer than 0.02mm (i.e. clay and silt), and less than 10 percent of the soil materials are dispersible1. Type C soils are mostly coarse-grained, and will settle quickly in a sediment retention basin.
On the other hand, the laboratory results indicate the soil samples collected at SS2 (immediately adjacent to the existing access road) are Type F soils. That is, more than 33 percent of the particles are finer than 0.02 mm, and less than 10 percent of the soil materials are dispersible. Type F soils are mostly fine-grained, and require a much longer residence time to settle in a sediment retention basin.
The results of the laboratory analysis have been used to determine the most appropriate erosion and sediment control measures, including the design of appropriate sediment basins where required (see Section 9.5.3.3).
6.6 Surface Hydrology
6.6.1 Regional Hydrology
The Project Site is located within the Macquarie River Catchment in central New South Wales. The Macquarie and Bogan Rivers are the primary rivers within the catchment, of which the Bell, Talbragar, Cudgegong, Turon, Fish and Campbells Rivers are major tributaries.
The Macquarie River is primarily formed by the joining of the Campbells and Fish Rivers, which drain a high plateau area centred near Oberon. The Project Site, located approximately 6km east-southeast of Oberon is therefore located close to the head of the Macquarie River catchment.
6.6.2 Local Hydrology
The Project Site drains to the Duckmaloi River, which forms part of the Fish River catchment, a tributary of the Macquarie River. The Duckmaloi River is located approximately 800m south of the Project Site and flows in an easterly direction at this locality. Figure 2 illustrates the local hydrology within the Project Site.
1 Soils that are dispersible are those where the percentage clay plus half the percentage silt (roughly the fraction <0.005mm) multiplied by the dispersion percentage is equal to or greater than 10 (Landcom, 2004).
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A number of ephemeral drainage lines and poorly defined drainage depressions are located within the Project Site. The existing extraction area is located between two ephemeral drainage depressions which converge together to become a 1st order stream (Strahler System for ordering water courses). This southerly flowing drainage line forms immediately south of the extraction area and is an ephemeral tributary of the Duckmaloi River. The drainage line flows to an existing retention basin located on the southern boundary of the Project Site (refer Figure 2 and Plates 3 & 4).
At the time of the site inspection, a low flow was evident in this drainage line. The presence of some coarse sediment which had been washed down in recent rain from the southern batter of the extraction area was also evident in the drainage line. Some scouring and erosion of the channel at the inlet to the southern retention basin was also apparent (refer Plate 5).
Plate 3 Drainage line south of existing extraction area, flowing to the retention basin
Plate 4 Existing southern retention basin
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Plate 5 Inlet to the existing retention basin
The proposed extension to the extraction area would extend north directly adjacent the drainage depression located on the western edge of the existing extraction area. This southerly flowing ephemeral drainage depression is reasonably well defined where it flows along the boundary of the existing extraction area, however, towards the northwestern corner of the existing extraction area, where the topography becomes flatter, the drainage depression becomes less defined. A second poorly defined drainage depression also commences further to the west joining the drainage depression adjacent the extraction area approximately 50m north from the southern point of the existing extraction area (see Figure 2) Section 9.5.3 details appropriate management measures relating to these drainage lines including clean water diversion works. It is noted that the proposed extension area would not result in any further encroachment of the defined section of drainage lines adjacent to the western boundary of the existing approved extraction area.
A southerly flowing ephemeral drainage depression also commences almost immediately south of the proposed stockpile area flowing towards the proposed extraction area (see Figure 2). Again this drainage depression is well grassed and poorly defined given that it is at the top of the catchment. Clean water diversionary works would be required to divert this water from entering the active extraction area. Again, these works are discussed below in Section 9.5.3.2.
6.7 Surface Water Quality
6.7.1 Regional Water Quality
The Project Site is situated in the far southeast of the area covered by the Central West Catchment Management Authority (CMA). In February 2007, the Central West CMA published the Catchment Action Plan for the Central West Authority (CAP). The CAP identifies catchment issues and sets measurable management targets with respect to land practices and water quality. The water quality targets set by the CAP include the following:
By 2016, electrical conductivity (EC) readings in the 50th and 80th percentiles respectively will be: - Macquarie River at Carinda, 500 EC and 800 EC;
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- Bogan River at Neurie Plains, 550 EC and 1450 EC; and - Castlereagh River at Coonamble, 315 EC. By 2016, improve surface and groundwater system health across the catchments, as measured by: - a 5% reduction in the modelled result for suspended sediment; - temperature to be maintained or restored to within 2 degrees Celsius of median levels (ANZECC guidelines 1992); - a reduction in the duration of blue-green algal blooms duration above the high alert level; - no detection of hazardous chemicals above ANZECC guidelines, 2000; - faecal coliforms reduced below primary contact levels at key sites in the catchment; and - flow rules are in operation to meet the long-term extraction limit and environmental water requirements, as defined by Water Sharing Plans. By 2016, 1,200,000ha (13%) of the catchment area is managed primarily to maintain or achieve optimal vegetation condition, and all vegetation types are represented in the catchment.
It is noted that the Project Site is not in an area subject to a Water Sharing Plan.
6.7.2 Local Water Quality
During the site inspection, a water sample was collected from the southern retention basin, and sent to a laboratory for analysis by RWC. The results of this analysis are presented below in Table 6, along with the default water quality objectives from the Australian and New Zealand Guidelines for Fresh and Marine Water Quality (2000) (ANZECC), where applicable. The watercourses surrounding the Project Site are categorised as Upland Rivers according to ANZECC.
As shown in Table 6, the water results are generally consistent with the trigger values specified in the ANZECC guidelines. The zinc and iron levels are only slightly above those recommended in ANZECC. The pH, EC and suspended solids are all well within the recommended ANZECC guidelines.
6.8 Surface Water Features of Conservation Significance
A flora and fauna assessment of the Project Site has been undertaken by Gingra Ecological Surveys and Biodiversity Monitoring Services (see Parts 2 and 3 of the Specialist Consultant Studies Compendium). It is understood that no Endangered Ecological Communities, Groundwater Dependent Ecosystems, Critical Habitat, Endangered Populations or Threatened flora or fauna species were observed during surveys of the Project Site.
It is understood that the Duckmaloi River located south of the Study Area is a known platypus habitat.
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Table 6 Water quality results
Sample taken from Trigger Value for ANZECC Guidelines retention basin freshwater 28/11/07 ANZECC Table 3.3.2 (Trigger values pH 6.51 6.5-7.5 for South-East Australia, upland rivers) ANZECC Table 3.3.3 (Trigger values Conductivity (µS/cm) 79 30-350 for upland rivers) 2000 ANZECC Guidelines for Physio- Suspended Solids (mg/L) 5 <40 chemical stressors (freshwater) Total Alkalinity as CaCO3 (mg/L) 12 - Sulphate as SO42- (mg/L) 4 - Chloride (mg/L) 7.7 - Dissolved Major Cations Calcium (mg/L) <1 - Magnesium (mg/L) <1 - Sodium (mg/L) 12 - Potassium(mg/L) <1 - Total Metals Arsenic (ug/L) 2 24 ANZECC Table 3.4.1 Cadmium (ug/L) <0.1 0.2 ANZECC Table 3.4.1 Copper (ug/L) <1 1.4 ANZECC Table 3.4.1 Lead (ug/L) <1 3.4 ANZECC Table 3.4.1 Manganese (ug/L) 46 1900 ANZECC Table 3.4.1 Zinc (ug/L) 9 8 ANZECC Table 3.4.1 2000 ANZECC Guidelines for Iron (ug/L) 350 300 Recreational Water Quality & Aesthetics Ionic Balance Total Anions (meq/L) 0.55 - Total Cations (meq/L) 0.50 -
6.9 Groundwater Connectivity
A number of exploration boreholes were drilled as part of the preparation of a Statement of Environmental Effects for the quarry in May 2003. The bores were drilled to a maximum depth of 20m. Of the 29 exploration bores drilled, several bores intersected groundwater. The water intersected is believed to be representative of unconnected and perched water bodies, rather than a significant groundwater resource.
11 registered bores are located within a 3 km radius of the Project Site, although limited data is available from these bores. The closest bore, GW801330, is located 570m southwest of the extraction area on the periphery of the alaskite resource, with the elevation of the standing water level recorded at 1058m AHD. The water-bearing zone, as indicated by the bore log, is located within the granite.
No significant groundwater source is likely to be intersected by the extraction activities, as the lowest expected level achieved in the extraction area is 1 130m AHD. This is higher than the water level within the closest registered bore located within the Oberon Alaskite, at approximately 1058m AHD. Any minor seepage that may occur due to extraction activities would be collected by the proposed additional sediment retention basin at the base of the extraction area. Erosion and sediment control measures are discussed further below in Sections 9.5.3.3 and 9.5.3.4.
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The next closest registered bores to the south (GW056745) and to the northwest (GW801754) are located approximately 1.9km and 2.3km respectively from the proposed extraction area. Bore logs from these bores and geological maps confirm that these bores are located in geological units separate from the Rossdhu Granite, and it is therefore considered that these bores utilised by surrounding landholders would be unaffected by the proposed extension to the extraction area.
7 RELEVANT LEGISLATION, POLICY AND GUIDELINES
A number of government policies and guidelines relating to surface water management are applicable to the Project, as well as legislative requirements, and have been considered in this Surface Water Assessment. The relevant policies, guidelines and legislative requirements are summarised below.
7.1 Policies and Guidelines
The NSW State Rivers and Estuaries Policy contains state-wide objectives for the protection and enhancement of watercourses. The proposed surface water management should be consistent with the Policy objectives. The key aspect of this would be to demonstrate that there is no degradation of the Duckmaloi River as a result of quarry activities.
In NSW, the most relevant and comprehensive guidelines for the designs of stormwater controls are contained in the Blue Book (Volume 1). Volume 1 of the Blue Book contains prescriptive guidelines for what should be included in an Erosion and Sediment Control Plan (ESCP) and a Soil and Water Management Plan (SWMP). Many of the prescriptive guidelines will not be relevant to this project, however, the principles of surface water control, including the design of erosion and sediment control structures, would be adopted where applicable.
Water quality impacts will be assessed for aquatic ecosystems in accordance with the Australian and New Zealand Guidelines for Fresh and Marine Water Quality (ANZECC 2000). The watercourses within the site are considered to be slightly to moderately disturbed ecosystems as described in the ANZECC Guidelines and the elevation of the site places the site in the upland river ecosystem category.
The Central West CMA Catchment Action Plan 2006-2016 (February 2007) contains river health targets that will be considered as part of this assessment.
7.2 Legislation
The Protection of the Environment Operations Act 1997 (POEO Act) is relevant to the Project as it contains requirements relating to the prevention of the pollution of waters. In this regard the discharge of water from the Project Site would need to be controlled to an agreed standard to reduce the potential for pollution of the receiving waters. The existing quarry does not require an Environment Protection Licence (EPL) under the POEO Act, however an EPL would need to be obtained for the proposed operations, as the annual production would exceed the threshold level for a licence.
GSS Environmental SPECIALIST CONSULTANT STUDIES 1 - 25 MUDGEE STONE COMPANY PTY LTD Part 1: Surface Water Assessment Oberon White Granite Quarry Report No. 709/03 The Water Act 1912 and Water Management Act 2000 contain provisions for the licensing of water capture and use. If any dams are proposed as part of the water management, consideration must be given to whether the dams need to be licensed. If the dams are not within the harvestable right of the property, or are not specifically exempt dams, it is likely that they would need to be licensed. The Maximum Harvestable Right Dam Capacity (MHRDC) has been calculated for the Project Site, and is discussed in Section 9.5.6.
8 KEY ISSUES/CONSTRAINTS
The key surface water issues relating to the Project that have been identified are listed below, and are addressed in the following sections of this Surface Water Assessment.
1. Prevention of the inflow of water into the active work areas. This can be achieved by the diversion of clean water around the active extraction area. As discussed above, some clean water runoff would flow into the active extraction area without diversionary works. 2. Reduction of the potential for the transport of sediment off site into watercourses, and the flow-on impact of sedimentation on receiving waters, i.e. the Duckmaloi River. This can be achieved by a number of control and mitigation measures: a. Diversion of clean water (where possible) around the active work area as discussed above, as well as the capture and treatment of dirty water. The containment and treatment of dirty water should be relatively straight- forward via the installation of a sump in the southwest corner of the extraction area, and the installation of a sediment basin on the southern side of the extraction area. The southern retention basin would also remain, which can therefore serve as a ‘backup’ if required. b. Adequate stabilisation works of the drainage line bed and bank flowing into the southern retention basin will also need to be implemented to minimise any mobilisation and transport of sediment into the retention basin. c. Implementation of stabilisation and rehabilitation works of the southern batter of the extraction area to minimise/eliminate the mobilisation of sediment from this batter into the retention basin. It is understood that the visible sediment in the drainage line immediately south of the extraction area was raised as an issue during the planning focus meeting held on site. 3. The management of ephemeral watercourses in accordance with the expectations of the Department of Water and Energy. The proposed extension to the extraction area would result in extraction operations extending adjacent the ephemeral drainage depression located along the western edge of the existing extraction area. At the top of this drainage depression the topography becomes much flatter and is well grassed, with no clearly defined flow channel evident. Therefore it is considered that some clean water diversionary works would be warranted to avoid potential flows over the western extraction faces, particularly during larger rainfall events. This management measure is addressed in the following sections of the Surface Water Impact Assessment.
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4. The control of surface flows on rehabilitated areas to ensure minimal soils loss and adequate soil moisture for plant growth. Standard erosion controls would be implemented as part of the final landform, and the area would need to be managed after the cessation of extraction activities until the area can be declared to be stable.
9 SOIL AND WATER MANAGEMENT PLAN
The following Soil and Water Management Plan (SWMP) has been prepared to address regulatory requirements and the key surface water issues and constraints discussed above in Section 8. The SWMP incorporates the detail that is required within both a Water Management Plan, and an Erosion and Sediment Control Plan.
9.1 Introduction
In accordance with the Director General’s requirements, and in particular the requirements of the Department of Water and Energy (now NSW Office of Water (NOW)), this SWMP for the Project has been prepared in accordance with the Landcom document Managing Urban Stormwater: Soils and Construction, Vol. 1, 4th eds. (Landcom, 2004) (the ‘Blue Book’).
The SWMP incorporates:
an identification and categorisation of the water catchments within the Project Site; a description of the local soil types and their potential influence on the design and construction of water management structures; an assessment of constraints posed by the location of the Project Site and the characteristics of the local soils and surface water catchments; a description of the proposed soil and water management at the Project Site including: - soil and water management objectives; - soil best management practices; - water best management practices, including a description of the structures used on the Project Site to control and store water flows; and - a basic water balance for the Project Site. a Surface Water Monitoring Program (SWMonP).
For management purposes, the water within the Project Site has been divided into two classes.
(i) “Clean” water - surface runoff from undisturbed catchments or relatively undisturbed by extraction, processing or related activities. (ii) “Dirty” water - surface runoff from disturbed catchments such as the active extraction area, which could produce significant concentrations of suspended sediment.
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The principal objective of surface water management at the Oberon White Granite Quarry is to ensure that the water quality leaving the site meets the appropriate quality standards. This objective is intrinsic to erosion and sedimentation designs and controls, and is achieved by implementing the following principles.
Directing sediment-laden runoff into designated sediment control retention ponds. Diverting ‘clean water’ runoff unaffected by the operations away from disturbed areas and off site. Maintaining sediment control structures to ensure that the designed capacities are maintained for optimum settling of sediments. Implementing an effective revegetation, maintenance and monitoring program for the site.
9.3 Catchments of the Project Site
The Study Area can be divided into two main catchments, a clean water Catchment C (outlined in yellow in Figure 3), and a dirty water Catchment D (illustrated in brown in Figure 3) with a total area of 13.2ha. Catchment C has a total area of 8.0ha.
As can be seen in Figure 3, a number of small drainage depressions exist within the clean water catchment, and so for the purpose of designing diversionary works and appropriate erosion and sediment control measures, Catchment C has been divided into a number of sub- catchments, C1, C2 and C3. The recommended water management structures to be constructed in these sub-catchments are outlined in Section 9.5.3.2. The water within these catchments would be directed around the active extraction area and off site, via the southern retention basin.
Dirty water Catchment D consists of two sub-catchments, D1 and D2 with a total area of 9.6ha. Catchment D1 incorporates the proposed product stockpile area whilst Catchment D2 incorporates the proposed extraction area, safety bund and channel, surge stockpile and internal haul road together with a small area to the north of the extraction area limit which would contribute to runoff to the extraction area. Whilst the disturbance area within Catchment D2 would progress over time up to this proposed extent, a maximum disturbance area of 9.6ha has been used in the design of sediment control measures to ensure the worst case scenario is accounted for.
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Figure 3 Study Area Catchments and Proposed Water Management Structures A4 / Colour
GSS Environmental SPECIALIST CONSULTANT STUDIES 1 - 29 MUDGEE STONE COMPANY PTY LTD Part 1: Surface Water Assessment Oberon White Granite Quarry Report No. 709/03 A summary of the Study Area catchments is provided below in Table 7, and illustrated in Figure 3. Table 7 Study Area Catchments Catchment Area (ha) Related Disturbance Clean water catchments C1 1.2 Internal access track C2 2.2 - C3 4.6 - Total area 8.0 Dirty water catchments D1 3.6 Product stockpile area and site access road D2 9.6 Active extraction area and surge stockpile Total area 13.2
9.4 Assessment of Constraints
9.4.1 Introduction
As noted in the Blue Book, a proper assessment of site constraints is a prerequisite to the preparation and implementation of a SWMP. Constraints are classified as either:
(i) on-site, i.e. relating to soils, landforms, ecology, pollutants and hydrology occurring on the site of the proposed or approved activities; or (ii) downstream, i.e. relating to aquatic ecosystem sensitivity and the social and aesthetic values of the community.
Based on the identified constraints and opportunities, best management practices (BMPs) have been developed for the site to minimise the potential degradation of soil and water resources and/or other aesthetic/environmental assets while maximising the achievement of outcomes in accordance with principles of Ecologically Sustainable Development (ESD).
The recommended constraints to be addressed by the Blue Book are discussed in the sections below. These are in addition to the Project-specific constraints discussed in Section 8.
9.4.2 Riparian Lands
Waterfront Lands (formally known as Riparian Lands under the Rivers and Foreshores Improvement Act 1948) are those vegetated lands within 40 metres of waterbodies such as rivers, creeks, estuaries, lakes and wetlands. Development on riparian lands is constrained:
(i) to protect and enhance the social, economic, cultural, spiritual and heritage values of waterfront land for Aboriginal groups and the wider community; and (ii) to avoid or minimise land degradation, including soil erosion, compaction, geomorphic instability, contamination, acidity, waterlogging, salinity hazards and decline of native vegetation.
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The proposed extension to the extraction area would extend north towards the top of the catchments within the Study Area, and would not be within 40m of a river, creek, estuary, lake or wetland as defined by the Act. The proposed extension is adjacent to a number of small drainage depressions, as discussed in this Surface Water Assessment, however, these drainage depressions are minor, well grassed, located at the top of the local catchment, and are not marked as ‘blue lines’ on the 1:25,000 topographic map.
9.4.3 Erosion (Rainfall Erosivity & Soil Erodibility)
9.4.3.1 Rainfall Erosivity
The rainfall erosivity factor, R, is a measure of the ability of rainfall to cause erosion. It is the product of two components, namely:
total energy; and maximum 30 minute intensity for each storm.
Based on Map B - 2 of the Blue Book, the Project Site is located within a rainfall erosivity zone between 1,250 and 1,500 (a relatively low to moderate erosivity zone).
9.4.3.2 Soil Erodibility
Soil erodibility is a measure of the susceptibility of individual soil particles to detachment and transport by rainfall and runoff. Soil texture is the principal component affecting soil erodibility, but structure, organic matter and permeability also contribute. As discussed above in Section 6.5, the type of soils and the moderate slopes indicate the soils within the Project Site are sensitive to erosion without implementation of appropriate surface water and erosion control measures.
9.4.3.3 Soil Characteristics
Section 6.5 of this report provided a description of the type of soils to be encountered at the Project Site. According to the laboratory analysis of samples collected on site, and Blue Book classifications, the soil samples collected immediately adjacent to the internal haul road (SS2) are Type F soils, which are generally fine-grained soils with less than 10 percent of the soil materials dispersible. Type F soils are slow settling in wet basins.
The laboratory results of the soil samples collected at the southern retention basin (SS1) indicate the soils there are Type C soils, which are coarse grained soils, again with less that 10 percent of the soil materials dispersible.
Given that sample SS2 was collected in the vicinity of the active extraction area, the recommended sediment control measures described below in Section 9.5.3.3 have been designed based on the soil characteristics of the samples collected there, i.e. Type F soils. Designing a sediment basin to a Type F specification rather than Type C is also a more conservative method, and therefore this approach has been used.
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9.4.4 Surface Water Runoff
Given the relatively steep relief within several of the Project Site sub-catchments, surface water runoff will be an important consideration in the design and location of best management practice water storages and catchment/diversion structures.
The surface water runoff expected during average, wet and dry rainfall years is calculated in the water balance for the site (see Section 10.2.1).
9.4.5 Groundwater
As discussed in Section 6.9 no significant groundwater source is likely to be intersected by the extraction activities. Any minor seepage that may occur in the active extraction area would be collected by a sump in the southwest corner of the extraction area.
As the development and operation of the proposed extraction operations is unlikely to have a significant impact on local water tables, this will not constrain development of best management practice water management.
9.5 Soil and Water Management
9.5.1 Objectives
The principal objectives of soil and water management adopted in this surface water assessment are as follows.
(i) To manage the soil resources of the site to minimise the risk of erosion and maximise the potential use of any stripped/disturbed soil in ongoing rehabilitation of disturbed areas. (ii) To ensure appropriately designed and located water management structures are constructed and maintained to segregate “dirty” water from “clean” water. (iii) To ensure that “dirty” water captured within the disturbed catchment of the Project Site is retained and water appropriately treated to meet the water quality objectives as follows. pH - 6.5 – 8.5; Electrical Conductivity - <1,500 µs/cm; Total Suspended Solids - <50 mg/L; and Biochemical Oxygen Demand - <20 mg/L. (iv) To minimise erosion and sedimentation from all active and rehabilitated areas of the Project Site. (v) To monitor the effectiveness of surface water erosion and sediment controls and ensure the water quality criteria are met and that the Project Site has no adverse impact on water quality downstream, such as the Duckmaloi River.
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The following sub-sections have been structured and prepared to provide appropriate best management practices (BMPs) to maximise the potential to achieve each of these objectives.
Section 9.5.2 presents the soil BMPs to be adopted at the Project Site. Section 9.5.3 presents the water BMPs to be adopted at the Project Site. This section includes a description of water management within the Project Site, and in particular the water management structures to be installed. These include the construction of diversion banks to divert clean water around the active extraction area into existing drainage lines, the installation of a sump in the south western corner of the extraction area to collect dirty water, and the construction of sediment basins south of the product stockpile area and immediately below the extraction area.
9.5.2 Soil BMPs
9.5.2.1 Sources of Erosion and Sedimentation
During operations at the Project Site, erosion and sedimentation could potentially result directly or indirectly from the following.
a. Surface water runoff from active extraction areas, including areas cleared ahead of extraction. b. Surface water runoff from topsoil, overburden and product stockpile emplacements. c. Surface water runoff from rehabilitated areas prior to the successful establishment of vegetation. d. Runoff from haul roads, such as the internal haul road, at erosive velocities.
Minimising the area of soil exposed to surface water flows, either as cleared surfaces ahead of extraction, soil stockpiles or respread soils over rehabilitated surfaces, is the primary aim of soil management at the site. The secondary aim is to provide exposed soils with adequate protection to minimise disturbance caused by surface water flows. These aims are achieved through the adoption of the following BMPs.
9.5.2.2 Minimal Disturbance
Land disturbance would be minimised by clearing the smallest practical area of land ahead of extraction activities and leaving this disturbed for the shortest possible times. General vegetation clearing and soil stripping would not be undertaken until earthwork operations are ready to commence. All proposed erosion and sediment control measures would be implemented in advance of, or in conjunction with, clearing and stripping operations. Prior to clearing commencing, the limits of clearing would be marked by pegs placed at intervals on each side of the disturbed area or other similar system. All operations would be planned to ensure that there is no damage to any trees outside the limits to be cleared.
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9.5.2.3 Planning Considerations
As far as practical, ground disturbing activities should be scheduled such that the time from commencement to completion is less than 6 months. Where practicable, disturbance should begin at a point most distant from a waterway or drainage line and move closer. Cleared areas ahead of extraction should be restricted to the areas defined for each clearing campaign. Access to areas designated for ground disturbing activities should be limited to within 10 m (and preferably 5 m) of the designated area and identified with fencing, flagging or other methods. Prior to the commencement of any ground disturbing activities, upslope diversion banks (see Section 9.5.3.2) and downstream sediment fencing and / or other sediment retention structures (see Section 9.5.3.3) should be constructed / installed.
9.5.2.4 Handling and Stockpiling of Topsoil
Topsoil stripping should be undertaken when the soil is in a slightly moist condition thus reducing damage to soil structure, achieving a higher standard of revegetation and reduce maintenance requirements. The soil materials should not be stripped in either a dry or wet condition. Stripped material should be placed directly onto the disturbed areas and spread immediately if construction or extraction sequences, equipment scheduling and weather conditions permit.
If longer term stockpiling (i.e. greater than 6 months) is required, a maximum stockpile depth of approximately 3 metres should be maintained to preserve viability and reduce soil deterioration. Longer term soil stockpiles should be sown with the species recommended in Table 8 as soon as possible after stockpiling. Soil stockpiles should be constructed with a slope of <2:1(H:V) and the stockpile surface left roughened. Placement within natural or constructed drainage lines should be avoided, however, if unavoidable, upstream and downstream protection, in the form of diversion banks and downstream sediment retention structures should be constructed / installed prior to commencement of stockpiling.
Table 8 Recommended pasture mix
PASTURE SPECIFICATION Rate (kg/ha) Species Spring/Summer Autumn/Winter Japanese Millet 20 5 Ryecorn/Oats 5 20 Rhodes Grass 10 10 Couch Grass 10 8 Wimmera Ryegrass 5 10 White Clover 8 - Lucerne 5 - Sub Clover - 8 Serradella - 10 Consol - 2
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9.5.2.5 Soil Respreading
Before soil respreading, the ground surface should be scarified or ripped along the line of the contour to break any compacted and smooth surfaces and assist in keying the respread soil. Topsoil respread over areas of rehabilitation should be approximately 100mm on flat or shallow slopes (<4(H):1(V)) and no greater than 50mm on steeper slopes (>4(H):1(V)). The respread soils should be left with a roughened surface and sown with a non-persistent pasture species mix (devised in consultation with NOW) as soon as possible to stabilise the soils with long-term establishment of native grass and ground cover species consistent with existing vegetation communities.
9.5.3 Water BMPs
9.5.3.1 Introduction
Best management practices for water on the Project Site will consider:
(i) the diversion of clean water within a predominantly segregated clean water system; (ii) the capture and storage of dirty water within a segregated dirty water system; and (iii) the discharge of excess water from the Project Site. Detail is provided to the extent considered necessary to illustrate the concepts and objectives of water management implemented at the Project Site, and to describe the appropriate design and function of the various BMPs used to achieve these concepts and objectives.
9.5.3.2 Clean Water Diversion
Introduction A primary objective of water management on the Project Site is to segregate clean and dirty water flows, and diverting surface water flows away from the active extraction area is essential in achieving this objective. Uncontrolled water flows over disturbed areas of the Project Site would also greatly increase the risk of erosion. By diverting water flowing from undisturbed areas of the Project Site away from the active areas of disturbance, and directing this water at non-erosive velocities to stable areas in adjacent drainage lines, this risk would greatly be reduced.
As discussed above in Section 6.2, the general topography of the Project Site is higher in the north and sloping downward towards the south in the direction of the Duckmaloi River, which lies approximately 800m south of the Project Site. Therefore, without any control measures in place, clean water runoff generated at the top of the Project Site (to the north of the extraction area) would flow into the active extraction area.
The following section presents the surface water BMP structures to be employed on the Project Site to divert clean water. The proposed water management structures to be constructed are illustrated in Figure 3.
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Diversion Banks (Low Flow) These structures are simple earth banks which are generally constructed with a circular, parabolic or trapezoidal drain. They are designed to divert surface water flows from shallow to moderate slopes where the upslope length is less than 80m or within small or well vegetated catchments. Given that the undisturbed catchments within the Project Site are well grassed, a low flow diversion bank is deemed appropriate.
It is recommended that two clean water diversion banks be constructed. As discussed above, one diversion bank would be constructed to the north of the extraction area (within Catchment C1). This diversion bank would divert water flowing from the top of the clean water catchment and any overflows from Dam 1 around the western side of the active extraction area into Catchment C2. The location of this clean water diversion bank is presented in Figure 3.
A second diversion bank should be constructed in Catchment C2. As discussed above in Section 6.6, the proposed extension to the extraction area would extend directly adjacent the ephemeral drainage depression adjacent to the western edge of the existing extraction area. Towards the northern end of this drainage line (adjacent to the proposed extension) the drainage depression becomes much less defined, as the topography becomes flatter and well grassed at the top of the catchment, with no clearly defined flow channel evident.
Approximately 100m north of the northwestern corner of the approved extraction area, the second diversion bank should be constructed to divert clean water into the drainage depression further to the west. As discussed in Section 6.6, this western drainage depression joins with the drainage line adjacent the extraction area which converges with another drainage depression south of the extraction area to become a 1st order stream (Strahler System for ordering water courses), which is an ephemeral tributary to the Duckmaloi River.
The diversion banks should be constructed generally in accordance with Blue Book Standard Drawing SD 5-5 (attached as Appendix 4). A summary of the general design specifications is as follows.
Gradient of the diversion banks should be approximately 1%. Height of the bank should be at least 300mm. Channel depth should be at least 400mm. A level spreader (or sill) should be constructed at the bank discharge point to reduce the risk of erosion at this point. Within 10 days of construction, pasture should be sown to prevent erosion of the bank and drain.
Manning’s Equation was also used to determine the probable flow in the channel at a given depth and slope. A 50 year ARI was used in the design calculations, as recommended by version 2 of the Blue Book for Type D/F embankments and spillways, where the duration of disturbance is greater than 2 years. A summary of the diversion bank design details, and estimated water depth in the channels for both 10 year and 50 year ARI’s is summarised in Table 9.
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Table 9 Diversion Channels design specifications (based on Manning’s Equation) ARI Diversion Channel Channel Estimated Total depth Freeboard Velocity of Channel Slope base width water of channel (m) flow (m/s) (m) depth (m) (m) 10 year Northern 1% 1.0 0.19 0.54 0.35 1.07 (Catchment C1) Southern 1% 1.0 0.22 0.57 0.35 1.16 (Catchment C2) 50 year Northern 1% 1.0 0.26 0.62 0.36 1.47 (Catchment C1) Southern 1% 1.0 0.30 0.67 0.37 1.58 (Catchment C2)
The diversion banks should be inspected fortnightly, or following a significant rain event to ensure that they are capable of carrying the surface water flow of the catchment at non-erosive velocities or concentrations. In the event that significant erosion is observed, the diversion bank should be upgraded to cater for high flows in accordance with Blue Book SD 5-6.
Road Crossings The existing site access road would be retained as an internal access track. As can be seen in Figure 3, the diversion bank in Catchment C1 would cross this existing site access road. Despite the low flows expected in the channel, as detailed in Table 9 a pipe or culvert would be constructed under the road to allow light vehicles to cross whilst minimising potential for sediment mobilisation. Stabilisation works should be undertaken within the diversion channel, including use of geofabric and rock ballast, at the inflow and outflow points to the culvert.
Inspections of the culvert should occur at least fortnightly, with any maintenance work required completed within 7 days of the inspection.
Road Drainage Spoon drains are open drains constructed with a parabolic or trapezoidal channel and used to divert water flows from road side drainage to vegetated or otherwise erosion protected areas. The primary function of the spoon drain is to reduce the concentration and velocity of water flows within the road side drainage and, therefore minimise the potential for erosion and transport of sediment to discharge points. Given that some sections of the proposed internal haul road would be constructed at a relatively steep gradient (from a surface water management perspective), spoon drains should be constructed along these sections.
Each spoon drain should be inspected at least fortnightly with particular emphasis on the condition of land immediately down-slope of the discharge point. Any maintenance work should be completed within 7 days of the initial inspection.
9.5.3.3 Dirty Water Capture and Settlement
Introduction By ensuring surface water which falls or flows over disturbed areas within the Project Site (Catchment D) is captured in structures designed to allow for settlement of sediment in the water, the potential for downstream pollution of clean waters and/or lands would be minimised
GSS Environmental SPECIALIST CONSULTANT STUDIES 1 - 37 MUDGEE STONE COMPANY PTY LTD Part 1: Surface Water Assessment Oberon White Granite Quarry Report No. 709/03 and/or eliminated. The following sub-sections describe the design, location and construction of these structures aimed at diverting, capturing and settling dirty water on the Project Site.
Sediment Basins As can be seen in Figure 3, a small sediment basin (Dam 1) would be constructed in Catchment D1 immediately to the north of the proposed extraction area boundary. Dam 1 is to capture any runoff from the product stockpiling area as well as any water which may flow in the small section of ephemeral drainage depression, flowing towards the extraction area. A diversion bank would also be constructed in accordance with Blue Book specifications to divert water from the eastern part of Catchment D1 into Dam 1 (refer Figure 3).
Based on Blue Book specifications for a Type F sediment basin, the required size of this dam is 0.56ML. The calculations used to size this dam are attached in Appendix 1. The key assumptions used to calculate the sediment basin size are as follows.
Catchment area of the dam is 3.6 ha (Catchment C1, refer Figure 3). Design storm of 5 day, 90th percentile. This is based on the recommendations in version 2 of the Blue Book (Mines and Quarries), which recommends adopting a 90th percentile design storm event when designing a Type D/F basin where the duration of disturbance will be greater than two years.
To ensure Dam 1 is also of a sufficient size to capture a 1 in 100 year ARI rainfall event to prevent flooding of the active extraction area, the size of this dam was also estimated based on catchment yield in addition to assessing the required volume of this dam based on the Blue Book. The required size to contain a 1 in 100 ARI rainfall event based on catchment yield is 0.51ML (see Appendix 2 for the design calculations). This is slightly less than the required size based on the design specifications for a Type F sediment basin.
It is therefore recommended that, as a conservative approach, this Dam 1 be constructed as a Type F sediment basin with a minimum capacity of 0.56ML. To provide further redundancy, the sizing could be increased by 25% to 0.7ML which would allow the dam to adequately function in rainfall events beyond required design standards. The dam is to be constructed in accordance with Blue Book standard drawing SD 6-4, attached as Appendix 3.
In addition to Dam 1, it is recommended that a number of erosion and sediment control structures be constructed to manage dirty water within the active extraction area (Catchment D2).
An approximately 0.1ML sump would be constructed in the southwest corner of the active extraction area. This is the low point within the disturbance area, and therefore any dirty water generated within the extraction area from runoff or groundwater seepage would naturally flow to this sump, allowing for all water generated within the disturbed areas of the extraction area and internal haul road to be totally contained within the extraction area.
To allow for this water to be pumped or siphoned out of the sump if required for operational reasons, it is recommended that a sediment basin be constructed immediately south of the southern batter of the extraction area, as illustrated in Figure 3 (Dam 2). This sediment basin would also capture runoff from the southern batter of the extraction area; whilst rehabilitation works are still in progress (see Section 9.5.4).
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Based on Blue Book specifications for a Type F sediment basin, the required size of Dam 2 is 2.18ML. The calculations used to size this dam are attached in Appendix 5. The key assumptions used to calculate the sediment basin size are as follows.
Catchment area of the dam is 9.6ha. This is the maximum area within this catchment which surface runoff could potentially contact disturbed areas. Therefore the dam would be of sufficient capacity for the life of operation, ie. for the entire 6 ha extraction area. Design storm of 5 day, 90th percentile. This is based on the recommendations in version 2 of the Blue Book (Mines and Quarries), which recommends adopting a 90th percentile design storm event when designing a Type D/F basin where the duration of disturbance will be greater than two years.
It is noted that the design for Dam 2 does not take into account the capacity of the quarry sump and that sump would provide an initial ‘treatment’ of runoff from the extraction area.
As discussed above, a secondary retention basin exists at the southern end of the Project Site. At present, all runoff from the Project Site reports to this basin. This would continue to be the case with the proposed operations with the basin retained as ‘Dam 3’. With the implementation of the sediment control measures discussed in this SWMP, the water reporting to Dam 3 should be clean water. To ensure this is the case, some rehabilitation and stabilisation works would be required to Dam 3 itself, the inlet to the dam, and the southern batter of the extraction area. These are described below in Section 9.5.4.
A fortnightly inspection of Dams 1, 2 and 3 together with the quarry sump should be undertaken where the following information is recorded.
General condition. Evidence of overflow and condition of downstream catchment. Water colour, eg. highly turbid, brown, clear etc. Evidence of eroding surfaces. Evidence of sediment discharge. Approximate retained capacity.
9.5.3.4 Additional Sediment Protection
Introduction Additional sediment controls should be installed throughout the site (for example within the road side drainage of the proposed internal haul road) to reduce the velocity of flows, and therefore reduce the potential for erosion within channels and at the discharge points.
Sediment Fencing A sediment fence (also known as a silt fence) is a temporary barrier of geotextile filter fabric supported by steel wire and steel posts.
GSS Environmental SPECIALIST CONSULTANT STUDIES 1 - 39 MUDGEE STONE COMPANY PTY LTD Part 1: Surface Water Assessment Oberon White Granite Quarry Report No. 709/03 Sediment fences filter runoff flowing from the site, trapping the sediment and allowing filtered water to pass through.
Sediment fences have the following design limits.
The area draining to the fence is 0.6 ha or less. The maximum slope gradient behind the fence is 2:1. The maximum slope length behind the fence is 60m.
Generally, these structures should be installed prior to disturbance within a catchment, and should therefore be installed prior to the commencement of any construction activities, such as the preparation of the new product stockpile area. In addition, they may also be installed in response to elevated sediment discharge levels observed on the Project Site. Sediment fences should be installed on the downstream periphery of all stockpile footprint areas, including the product stockpiles at the north of the Site, and around the surge stockpile adjacent to the extraction area. The locations of these stockpiles are illustrated in Figure 3.
Maintenance More than any other structures, the additional sediment controls should be regularly inspected and maintained as these structures represent the final control point for water discharged from the Project Site. Each structure should be inspected fortnightly, or following significant rainfall (ie. greater than 25mm in 24 hours) and the general condition recorded, including:
whether the structure(s) has been damaged or not; amount of sediment present upstream and downstream; breaches of the structure(s); presence of eroding surfaces; and requirement for maintenance.
In the event maintenance is required, works should be completed within 7 days of the inspection.
Rehabilitation Ensuring that exposed and disturbed areas are rehabilitated as soon as possible and practical is essential in minimising the erosion potential of the site. A number of rehabilitation opportunities were identified during the site inspection, and these are discussed in Section 9.5.4.
9.5.4 Recommended Rehabilitation Works
9.5.4.1 Rehabilitation of the Southern Batter
During the site inspection the presence of coarse sediment was observed in the drainage line flowing south of the extraction area towards the existing southern retention basin (Dam 3). The source of this sediment is the exposed southern batter of the extraction area. To ensure that this source of sediment is stabilised, the implementation of rehabilitation works on the batter is recommended.
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The batter should be regraded to stabilise the batter, and seeded with endemic tree seed species, preferably collected from around the site. While the trees are establishing on the batter, any runoff from the batter should be collected and treated in the sediment basin constructed at the base of the wall (Dam 2), as discussed above.
9.5.4.2 Rehabilitation of the Southern Retention Basin
Some active gully erosion currently exists in the inlet channel to the southern retention basin, which will require some stabilisation works. In addition, as illustrated in Plate 4, some stabilisation works are required around the walls of the basin.
The recommended rehabilitation works consist of the following.
Strip existing topsoil from the drainage line and the side batters. Shape the side walls and inlet channel to the extent of gully erosion to ensure a more stable landform. Respread topsoil over the area. Sow the inlet channel and the side walls with an appropriate pasture mix (see Table 8). Secure jute mesh and bitumen to the original extent of the erosion in the drainage line.
These rehabilitation works should be undertaken in accordance with the recommended procedures in Section 9.5.2.
9.5.5 Summary
Based on the information provided above in relation to the proposed extension to the Oberon White Granite Quarry, and with the implementation of the recommended mitigation and control measures relating to soil and water management at the Project Site, it is anticipated that there would be minimal impact on surface water within and downstream of the Project Site as a result of the proposed operations. The key features of the proposed water management system are as follows.
All clean water would be diverted around the site, minimising the amount of dirty water to be captured and treated. All runoff from the site would pass through the existing southern retention basin (Dam 3). This basin should remain in place and serve as a ‘backup’ should there be an extreme rainfall event that exceeds the design capacities of the various erosion and sediment control measures. Minimal water would be used on site apart from some dust suppression water.
Table 10 provides a summary of the design specifications for the recommended water management structures for the Project.
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Table 10 Summary of dam volumes
Structure Type Capacity (ML) Dam 1 (sediment basin) Type F sed basin 0.70 Dam 2 (sediment basin) Type F sed basin 2.18 Quarry Sump - 0.1 Total 2.98
9.5.6 Maximum Harvestable Right Dam Capacity
The Maximum Harvestable Right Dam Capacity (MHRDC) has been calculated for the Oberon White Granite Quarry in accordance with the procedures outlined in the ‘Farm Dams Assessment Guide’ (NSW Department of Land and Water Conservation (DLWC), 1999).
The MHRDC for the Project Site based on a property area of 40ha is 3.8ML. The combined capacity of the dams recommended in this Surface Water Assessment is 2.98ML. In addition, the estimated capacity of the existing southern retention basin (Dam 3) is 1ML. Therefore, the combined dam capacity would be 3.98ML. This is slightly above the MHRDC, however, as the proposed sediment retention basins (Dams 1 and 2) and the quarry sump would be constructed for the purpose of “containment and recirculation of drainage, required by regulation to prevent the contamination of a water source” under the Farm Dams Policy, they would be exempt from the maximum harvestable right dam capacity.
10 SITE WATER BALANCE
10.1 Introduction
This section reviews site water requirements and available water storage against water availability to present a water balance for the Oberon White Granite Quarry. The water balance is provided for average, wet and dry years (10th, 50th and 90th percentile rainfall years).
As described above in Section 9.3, the Study Area can be divided into five catchments, C1, C2 and C3 and D1 and D2. Catchments C1, C2 and C3 are considered clean water catchments, with the runoff generated in these catchments to be diverted around the active extraction area and off site via Dam 3. Catchments D1 and D2 are dirty water catchments, encompassing the product stockpiling area, surge stockpile area, active extraction area, and the area just above the extraction area which would contribute runoff into the extraction area.
10.2 Inputs
10.2.1 Rainfall/Runoff
The water balance considers rainfall and runoff generated during low (annual 10th percentile), average (annual 50th percentile) and high (annual 90th percentile) rainfall years. The rainfall data has been obtained from the Bureau of Meteorology monitoring station at Oberon (station
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063293), which is considered to be the most representative of the Project Site. Rainfall is as follows.
Annual 10th percentile (dry year): 523.4mm Annual 50th percentile (average year): 743.4mm Annual 90th percentile (wet year): 929.7mm
Rainfall is reasonably well distributed throughout the year, although there is a peak in the winter months and early spring.
As discussed above, runoff generated in clean water catchments C1 and C2 would be directed around the active extraction area and offsite, via Dam 3. Runoff generated within C3 would also flow into Dam 3. A catchment yield of 0.3 has been estimated for the clean water catchments, given that these catchments are relatively undisturbed and well vegetated.2
A runoff coefficient of 0.5 has been estimated for the dirty water Catchment D1 and 2 given the disturbed nature of the catchment.3
The estimated runoff generated during average, wet and dry years in both the clean and dirty water catchments is detailed in Table 11.
Table 11 Annual average runoff generated Catchment Runoff (ML) Average Yr (50%ile) Wet Yr (10%ile) Dry Yr (90 %ile) C1 2.7 3.3 1.9 C2 4.9 6.1 3.5 C3 10.3 12.8 7.2 D1 13.4 16.7 5.7 D2 35.7 44.6 25.1 TOTAL RUNOFF 66.9 83.7 43.3
10.2.2 Groundwater seepage
Significant groundwater is not expected to be intersected during the extraction operation. Groundwater seepage has therefore not been included as an input to the water balance, as it is assumed that any water pooling in the active extraction area would be a result of runoff after a rainfall event, and this water would naturally drain to the sump in the southwest corner of the extraction area, and/or can be pumped to Dam 2 if required. Runoff entering the extraction area is accounted for in the runoff calculations for Catchment D2. In the event significant groundwater inflows into the extraction area are experienced, the water balance would need to be revised.
2 In the guidelines ‘Establishing Stable Drainage Lines on Rehabilitated Minesites’ released by the DLWC in 1999, a catchment yield of between 25%-35% is recommended for well vegetated natural catchments when looking at a long-term probability of exceedance of 2% of years. 3 The DLWC Guidelines mentioned above recommend a catchment yield of 55%-65% for overburden/mine spoil. A slightly less catchment yield of 0.5 has been applied in the water balance based on site observations that relatively little runoff accumulates in the active extraction area.
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10.3 Outputs
10.3.1 Evaporation losses
This Surface Water Assessment has recommended the construction of a number of storage dams; Dam 1, which would be a sediment dam in Catchment D1, and Dam 2, a sediment dam in Catchment D2 and the quarry sump. In addition, the existing southern retention basin in Catchment C3 would remain. It is assumed that the only loss from the dams would be evaporation, apart from some water for dust suppression which is discussed below. Evaporation losses have been calculated as the direct evaporation from the surface of the dams and sump.
The nearest BOM station to the Project Site, Oberon (Jenolan Caves Road) station does not collect evaporation data. Mean evaporation data was therefore obtained from the Bathurst BOM station (No. 063005), with the average yearly evaporation being 1347mm. The evaporation loss from the water storage dams has been calculated as follows:
Evaporation loss = Dam surface area * average yearly evaporation * 0.7.
It is estimated that the water storage dams and quarry sump would have a combined surface area of 885m2. A factor of 0.7 has been used to account for variations in the water level in the dams, and to account for the dams not always being full.
The combined annual average evaporation from the on-site dams and sump is therefore estimated at 0.8ML.
10.3.2 Dust Suppression No water would be used for washing of the extracted material, and therefore dust suppression would be the primary on-site water use, with annual average usage estimated to be approximately 15ML. This includes dust suppression on the access roads, hardstands and stockpile areas and during crushing. All water used for dust suppression would be non-potable water sourced from Dams 1 and 2 or the quarry sump.
The total annual output for the water balance is therefore estimated to be 15.8ML.
10.4 Water Balance
The water balance for average, wet and dry years is presented in Table 12.
Table 12 Water balance for the Oberon White Granite Quarry Inputs and Outputs Avg Yr (ML/Yr)Wet Yr (ML/Yr)Dry Yr (ML/Yr) INPUT: Combined runoff from 66.9 83.7 43.3 catchments C1, C2, C3, D1 & D2 OUTPUT: Evap. Losses and water 15.8 15.8 15.8 for Dust Suppression EXCESS 51.1 67.9 27.5
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As can be seen in Table 12, there is an excess of water in all scenarios. It is important to note, however, that the majority of this ‘excess’ water is clean water runoff that is being diverted around the active extraction area. This clean water has been included in the water balance as it would flow offsite via Dam 3. In addition, all dirty water collected on site would be directed to Dams 1 and 2, which would be constructed as a Type F sediment basin in accordance with Blue Book specifications. Therefore, as long as Dams 1 and 2 are maintained as per Blue Book requirements to ensure the dams continuously operate effectively as sediment basins, then any overflow from these dams would be clean water.
11 SURFACE WATER MONITORING PROGRAM
11.1 Introduction
The Surface Water Monitoring Program for the Oberon White Granite Quarry details a recommended program to monitor both the surface water quality downstream of the Project Site, and the effectiveness of the Soil and Water Management Program.
11.2 Monitoring Locations
The proposed surface water monitoring locations are as follows:
1. Dam 1; 2. Dam 2; 3. Dam 3; and 4. the Duckmaloi River, just upstream and downstream of the drainage line from the Project Site.
These locations have been chosen for the following purposes.
To identify the quality of water held in the dams on site. To assess whether the Project Site may be having any impact on the water quality of the Duckmaloi River. To assess the effectiveness of erosion and sediment control measures.
Table 13 identifies the proposed monitoring point locations, the type of monitoring point and with a brief description (where relevant) of the location and frequency.
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Table 13 Proposed Monitoring Locations Type of Frequency Location Monitoring Description of Location
Point Dam 1 Water Quality Proposed dam located above Quarterly extraction area Dam 2 Water Quality Proposed dam located below Quarterly extraction area Dam 3 Water Quality Existing dam located at southern Quarterly and within 24 boundary of site hours of any discharge*. Duckmaloi River Water Quality Upstream of the Project Site Annually (if creek flowing) and within 24 hours of any discharge*. Duckmaloi River Water Quality Downstream of the Project Site Annually (if creek flowing) and within 24 hours of any discharge*. Project Site water Erosion and All noted erosion and sediment Monthly and after management (erosion and Sediment control structures. significant rainfall events sediment control) structures Control * Up to four time per year
11.3 Monitoring Parameters
Table 14 presents the parameters that should be measured at each monitoring location.
The recorded values for the parameters measured should be assessed as a minimum against the water quality results and ANZECC trigger values presented in Table 6, and plotted to identify any trends over time. This information should be reviewed on a regular basis, ie. at least annually and should ongoing increases in relevant parameters be evident, the cause of this should be investigated and appropriate measures implemented.
The range of analytes measured should also be reviewed following the first 12 months of monitoring and a diagnostic set of analytes adopted for ongoing monitoring.
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Table 14 Monitoring Parameters Location Parameters Sampling Method Total Suspended Solids Dams 1, 2 and 3 pH Representative sample Electrical Conductivity pH Total Suspended Solids mg/L Total Dissolved Solids mg/L Specific Conductance μS/cm
CO3 (as CaCO3) mg/L
HCO3 (as CaCO3) mg/L Calcium mg/L Duckmaloi River Chloride mg/L Representative sample Iron (filterable) mg/L Potassium mg/L Magnesium mg/L Manganese mg/L Sodium mg/L
Sulphur (as SO4) mg/L
Total Hardness (as CaCO3) mg/L
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12 REFERENCES
ANZECC, Australian and New Zealand Guidelines for Fresh and Marine Water Quality (October 2000).
Catchment Action Plan (CAP), Central West Catchment Management Authority (February 2007).
DECC, Managing Urban Stormwater: Soils and Construction Vol 2E – Mines and Quarries (the Blue Book) (2008)
JAMMEL Environmental & Planning Services Pty Ltd, Erosion and Sediment Control Plan - Oberon Lot 13 DP 603429, Mudgee Stone Company Pty Ltd (August 2005).
Landcom, Managing Urban Stormwater: Soils and Construction – Vol 1, 4th Edition (the Blue Book) (2004).
The NSW State Rivers and Estuaries Policy (1992).
NSW Department of Land and Water Conservation, Farm Dams Assessment Guide (1999)
R.W. Corkery & Co. Pty Limited, Preliminary Project Outline and Environmental Assessment for the Oberon Granite Quarry Proposed Extension, Mudgee Stone Company Pty Ltd, (September 2007).
Waratah Scientific Services, Statement of Environmental Effects (SEE) – Oberon White Granite Quarry, Mudgee Stone Company Pty Ltd (July 2003).
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Appendices
(No. of pages including blank pages = 22)
Appendix 1 Dam 1 Design Volume Appendix 2 Dam 1 Catchment Yield Appendix 3 Type F Dam Design Appendix 4 Earth Bank Diversion Design Appendix 5 Dam 2 Design Volume
GSS Environmental MUDGEE STONE COMPANY PTY LTD 1 - 50 SPECIALIST CONSULTANT STUDIES Oberon White Granite Quarry Part 1: Surface Water Assessment Report No. 709/03
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GSS Environmental SPECIALIST CONSULTANT STUDIES 1 - 51 MUDGEE STONE COMPANY PTY LTD Part 1: Surface Water Assessment Oberon White Granite Quarry Report No. 709/03
Appendix 1
Dam 1 Design Volume
(No. of pages including blank pages = 4)
GSS Environmental MUDGEE STONE COMPANY PTY LTD 1 - 52 SPECIALIST CONSULTANT STUDIES Oberon White Granite Quarry Part 1: Surface Water Assessment Report No. 709/03
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GSS Environmental SPECIALIST CONSULTANT STUDIES 1 - 53 MUDGEE STONE COMPANY PTY LTD Part 1: Surface Water Assessment Oberon White Granite Quarry Report No. 709/03
GSS Environmental MUDGEE STONE COMPANY PTY LTD 1 - 54 SPECIALIST CONSULTANT STUDIES Oberon White Granite Quarry Part 1: Surface Water Assessment Report No. 709/03
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GSS Environmental SPECIALIST CONSULTANT STUDIES 1 - 55 MUDGEE STONE COMPANY PTY LTD Part 1: Surface Water Assessment Oberon White Granite Quarry Report No. 709/03
Appendix 2
Dam 1 Catchment Yield
(No. of pages including blank pages = 4)
GSS Environmental MUDGEE STONE COMPANY PTY LTD 1 - 56 SPECIALIST CONSULTANT STUDIES Oberon White Granite Quarry Part 1: Surface Water Assessment Report No. 709/03
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GSS Environmental SPECIALIST CONSULTANT STUDIES 1 - 57 MUDGEE STONE COMPANY PTY LTD Part 1: Surface Water Assessment Oberon White Granite Quarry Report No. 709/03
GSS Environmental MUDGEE STONE COMPANY PTY LTD 1 - 58 SPECIALIST CONSULTANT STUDIES Oberon White Granite Quarry Part 1: Surface Water Assessment Report No. 709/03
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GSS Environmental SPECIALIST CONSULTANT STUDIES 1 - 59 MUDGEE STONE COMPANY PTY LTD Part 1: Surface Water Assessment Oberon White Granite Quarry Report No. 709/03
Appendix 3
Type F Dam Design
(No. of pages including blank pages = 4)
GSS Environmental MUDGEE STONE COMPANY PTY LTD 1 - 60 SPECIALIST CONSULTANT STUDIES Oberon White Granite Quarry Part 1: Surface Water Assessment Report No. 709/03
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GSS Environmental SPECIALIST CONSULTANT STUDIES 1 - 61 MUDGEE STONE COMPANY PTY LTD Part 1: Surface Water Assessment Oberon White Granite Quarry Report No. 709/03
GSS Environmental MUDGEE STONE COMPANY PTY LTD 1 - 62 SPECIALIST CONSULTANT STUDIES Oberon White Granite Quarry Part 1: Surface Water Assessment Report No. 709/03
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GSS Environmental SPECIALIST CONSULTANT STUDIES 1 - 63 MUDGEE STONE COMPANY PTY LTD Part 1: Surface Water Assessment Oberon White Granite Quarry Report No. 709/03
Appendix 4
Earth Bank Diversion Design
(No. of pages including blank pages = 4)
GSS Environmental MUDGEE STONE COMPANY PTY LTD 1 - 64 SPECIALIST CONSULTANT STUDIES Oberon White Granite Quarry Part 1: Surface Water Assessment Report No. 709/03
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GSS Environmental SPECIALIST CONSULTANT STUDIES 1 - 65 MUDGEE STONE COMPANY PTY LTD Part 1: Surface Water Assessment Oberon White Granite Quarry Report No. 709/03
GSS Environmental MUDGEE STONE COMPANY PTY LTD 1 - 66 SPECIALIST CONSULTANT STUDIES Oberon White Granite Quarry Part 1: Surface Water Assessment Report No. 709/03
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GSS Environmental SPECIALIST CONSULTANT STUDIES 1 - 67 MUDGEE STONE COMPANY PTY LTD Part 1: Surface Water Assessment Oberon White Granite Quarry Report No. 709/03
Appendix 5
Dam 2 Design Volume
(No. of pages including blank pages = 4)
GSS Environmental MUDGEE STONE COMPANY PTY LTD 1 - 68 SPECIALIST CONSULTANT STUDIES Oberon White Granite Quarry Part 1: Surface Water Assessment Report No. 709/03
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GSS Environmental SPECIALIST CONSULTANT STUDIES 1 - 69 MUDGEE STONE COMPANY PTY LTD Part 1: Surface Water Assessment Oberon White Granite Quarry Report No. 709/03
GSS Environmental MUDGEE STONE COMPANY PTY LTD 1 - 70 SPECIALIST CONSULTANT STUDIES Oberon White Granite Quarry Part 1: Surface Water Assessment Report No. 709/03
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GSS Environmental