Paper Presents an Overview of the Harvesting Scheme and Results from Its Initial Operational Phase

STORMWATER 2010 National Conference of the Stormwater Industry Association Conference Proceedings

CAPTURING THE STORM: GETTING STORMWATER OUT OF THE GUTTER

Author/s: Mr Chris J Devitt, Director Technical Services, Orange City Council Mr Martin D Haege, Senior Environmental Engineer, Geolyse Pty Ltd Ms Kerry B Fragar, Environmental Monitoring Consultant, Geolyse Pty Ltd

SUMMARY

Historically engineers have managed stormwater with pits, pipe, channels and basins; or more recently, vegetated swales, bioretention systems and constructed wetlands. Stormwater is no longer an urban by- product to manage and dispose of safely. Created in relatively large and consistent volumes with even small rainfall events, urban stormwater should be viewed as a legitimate water source that, as part of an integrated system, can reduce demand on potable supplies or even supplement potable supplies. Orange City Council s Blackmans Swamp Creek Stormwater Harvesting Scheme signals a revolution in the way urban stormwater runoff is viewed and utilised by water authorities and the general public. The project is the first large scale stormwater harvesting scheme in Australia which intentionally harvests stormwater for addition to drinking water supplies. The scheme helps underpin the security of Orange s future water supplies, ultimately capable of providing up to 2,000 megalitres per year, approximately 35% of the City s current annual water requirements.

Evolution of the harvesting scheme from conceptual design, approvals and construction through to operational reality involved a diverse range of disciplines and skill sets. The project involved engineers, environmental consultants, risk management and water quality specialists, community interest groups, construction teams and operational staff. Diversity of knowledge was required to overcome the lack of relevant guidelines and precedents for developing a groundbreaking scheme of this nature. This paper presents an overview of the harvesting scheme and results from its initial operational phase. It discusses the process involved in undertaking the project from conceptualisation through to operational reality and highlights the challenges faced throughout design, approval, construction and operational refinement. Operational data and experience has been applied to the design of a recently approved expansion of the scheme that will harvest water stormwater from the Ploughmans Creek system. This expansion will further reinforce stormwater as a key component of Orange s integrated water supply system.

INTRODUCTION

The city of Orange is located approximately 250 kilometres west of Sydney in the Central Tablelands of New South Wales. Challenges in operating a water supply system for the population of 38,000 are attributed to the city s location high in the catchment, the lack of any substantial river system and limited groundwater supplies. The city therefore relies on a network of creeks which traverse the area, requiring innovative water management.

Dry conditions over several years and subsequent well below average runoff saw the City s water supply levels drop gradually from the start of 2002. While it was understood that normal rainfall patterns were likely to eventually return and the storage levels rise, the water supply situation at the time was seen as a significant concern. A water restriction regime commenced in January 2003 and restrictions reached Level 5 in May 2008. In August 2008 Council s two supply storages dropped to less than 25% capacity which meant that without significant inflows, the City had approximately one year of water supply remaining. With the real potential of restricted water access, the future growth and development of Orange was facing challenges. In response, Orange City Council is pursuing an integrated package of non-structural and structural programs to help secure the city s water needs. Council s non-structural measures aimed at reducing Orange s water demand include the introduction of water restrictions, a leak detection and pressure reduction program, a

STORMWATER 2010 National Conference of the Stormwater Industry Association Conference Proceedings rainwater tank subsidy, an exchange program for showerheads, the installation of water saving devices in all Council buildings, liaison with large water users and extensive community education. As a consequence of these initiatives, annual water usage in Orange has dropped from a high of 7,100 ML in 2002 to 3,782 ML in 2009/2010. Structural initiatives considered included reconnecting historical water supplies, groundwater, extraction from disused mines, connection with adjacent local water utilities, stormwater harvesting from upstream and downstream catchments and regional water security initiatives. Stormwater harvesting emerged as a viable option worthy of detailed investigation. The Blackmans Swamp Creek Stormwater Harvesting Scheme (BSCSHS) is a key component of an integrated package of water security initiatives which is being implemented by Orange City Council.

SCHEME DEVELOPMENT

Conceptual Design

The scheme was first proposed in 2008 when various water supply options were being considered. This phase of the project involved dedication to brainstorming and the refinement of ideas amongst a team of engineering staff. Due to the urgency of this project and its unique nature, assessment of concepts was given high priority.

Stormwater harvesting options included harvesting from rural catchments upstream of the city or from various sites downstream of the city. The Blackmans Swamp Creek scheme was seen as the preferred option because:

The catchment generates large and regular flows even from small rainfall events, due to significant development existing in the catchment; The creek passes reasonably close to Suma Park Dam; and There was some existing infrastructure in place including utilisable access, adequate power supply and an existing pipeline.

The very high level of treatment provided by Council s main water filtration plant, which treats water from Suma Park Dam, was also seen as an advantage for any scheme responsible for adding a new water source to the dam.

Design of the scheme required a thorough understanding of the stormwater and creek system, including catchment characteristics, flow patterns, existing demands and stormwater quality. Extensive modelling was undertaken to determine creek flows and the scheme performance under various operating scenarios.

The urban area of Orange lies within two local creek catchments, the largest of which is Blackmans Swamp Creek, which covers about 34 km² to its junction with Summer Hill Creek. Blackmans Swamp Creek rises in rural land south of the city and flows through the central business district, heading in a north-easterly direction, passing immediately west of Suma Park Dam, the City s main water supply dam, before joining with Summer Hill Creek a kilometre downstream of the dam. Approximately 70% of the city falls within this catchment (refer to Figure 1). The catchment area of Blackmans Swamp Creek upstream of the harvesting point is 30.5 km2. The stormwater harvesting scheme holding pond, which is on an unnamed tributary to Blackmans Swamp Creek, has a further catchment area of 2.5 km2 (refer to Figure 1).

STORMWATER 2010 National Conference of the Stormwater Industry Association Conference Proceedings

Figure 1: Blackmans Swamp Creek catchment

Modelling of the catchment indicated that the average annual runoff passing the stormwater harvesting location is approximately 9,480 ML/year and ranges from 2,400 to 25,000 ML/year. The volume of runoff generated from rainfall events is dependent on antecedent conditions. Modelling indicates that on average, 10 mm of rainfall across the Blackmans Swamp Creek catchment produces approximately 140 ML of runoff, but this can range from 70 ML to 200 ML depending on antecedent conditions and rainfall patterns.

The harvesting scheme underwent several revisions during the approval process and in its current configuration is expected to harvest an average of 800 ML/year. This is about 15% of the city s current unrestricted demand. Additional stages will see the average harvest increase to around 2,000 ML/year.

Approvals

The scheme was defined as a stormwater management system under State Environmental Planning Policy (Infrastructure) 2007 that could be carried out by or on behalf of a public authority (Orange City Council) without consent on any land. Whilst development consent was not required to construct or operate the scheme, Council had an obligation under Part 5 of the Environmental Planning and Assessment Act, 1979 to consider the environmental impacts of the activity. A Review of Environmental Factors (REF, Geolyse, 2008) was prepared to assist in the determination process.

The REF provided a comprehensive outline of the project and concluded that the construction and operation of the scheme was unlikely to result in a significant adverse environmental impact. It was acknowledged that removing water from the system must have a downstream impact and the challenge was to adaptively manage the scheme s use so that the significance is minimised and that the needs of downstream users and the aquatic environment are not compromised (Geolyse, 2008).

The initial use of the scheme was linked to emergency conditions and harvesting will occur until the combined storage in Suma Park Dam and Spring Creek Dam exceeds 50%. Ministerial authorisation was required to allow

STORMWATER 2010 National Conference of the Stormwater Industry Association Conference Proceedings this. The authorisation only applies for such time that the emergency exists. The second stage is for the permanent use of the scheme and the topping up of Suma Park Dam whenever storage is less than 100%. Council has applied for a permanent water licence to operate the scheme on an ongoing basis.

Under both scenarios, harvesting is dictated by operating rules which limit when and how stormwater can be harvested. These include flow trigger points which define when harvesting can commence, maintaining base flows and establishing ongoing stakeholder engagement.

Water Quality Management

Managing water quality is a critical factor in the success of the harvesting scheme. Urban stormwater can include a range of pollutants that left untreated or unmanaged, pose a threat to the city s raw water supplies. The source of stormwater pollutants in an urban setting ranges from atmospheric deposition to direct discharge. Pollutant sources and whether they were present in the catchment were initially identified through a catchment audit and review of available quality monitoring data.

Design of the scheme included the creation of multiple barriers to manage possible contamination. These include catchment level, system level and operational level barriers.

The harvesting scheme includes an extensive monitoring program to ensure the water delivered to the City s main water supply dam meets quality targets. Samples are collected during each harvest event and allow quality comparison between the raw creek water, holding pond, the batch ponds following treatment and the main water supply dam.

Commissioning and Operational Refinement

The scheme was constructed in 5 months, commencing in October 2008 and commissioned in March 2009. The first harvest event occurred on 4 April 2009, with the first water transferred to Suma Park Dam on 21 April 2009. Operational data has been used to refine the scheme operation.

The scheme was initially run in batch mode. In this operational mode, each batch (34 ML) of treated harvested stormwater was sampled and held until laboratory results confirmed the water met the scheme quality targets.

Following the success of this initial batch mode, a continuous approach to treatment and transfer was undertaken to enable greater efficiency in the harvesting scheme. Strict quality targets were adhered to in this phase and in line turbidity meters and ongoing testing are indicative of treatment success in the continuous mode of operation.

SCHEME OVERVIEW

Objectives

The objective of the Blackmans Swamp Creek Stormwater Harvesting Scheme is to augment the City s potable water supply in a manner that protects both public health and the downstream environment. This is achieved by:

harvesting a portion of high flows from the creek; having adequate risk management systems in place to meet water quality objectives; and adaptively managing the scheme so that its impact is not significant and that the needs of downstream users and the aquatic environment are not compromised.

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Layout and Operation

The layout of the harvesting scheme is illustrated in Figure 2. Major components and how they operate are described below:

Two large Gross Pollutant Traps (GPTs); one located on Blackmans Swamp Creek at Dalton Street and the other on a major piped drainage line near Margaret Stevenson Park. These are designed to remove a portion of the larger pollutants from the runoff.

A rock and gabion harvesting weir located on Blackmans Swamp Creek, just upstream of the City s Sewage Treatment Plant. This weir has a capacity of approximately 3 ML at its spillway level. Its role is to create a weir pool during runoff events from which stormwater can be harvested. The weir includes an unrestricted 300 mm pipe to allow low flows to pass through.

Pump Station 1, which is located immediately upstream of the harvesting weir. This pump station has three variable speed pumps, each with a capacity of 225 L/s. A maximum of two pumps are used, with the role of the two duty pumps being rotated between the three pumps (combined harvest rate of 450 L/s). The main harvest pumps activate when flow in the creek downstream of the harvest weir reaches 1,000 L/s.

A 230 ML holding pond that is used to balance harvested stormwater flows with the treatment system. This holding pond is constructed across an unnamed watercourse that is a tributary to Blackmans Swamp Creek. The catchment above the holding pond is about 251 ha and includes developed industrial areas and open rural zoned land.

Pump Station 2, which extracts water from the holding pond and transfers it to the batch ponds. This pump station has a capacity of 150 L/s.

A treatment shed that includes flocculant storage and a dosage point. A flocculant (aluminium chlorohydrate) is added to the harvested stormwater as it moves from the holding pond to the batch ponds to promote settling of suspended particles and attached contaminants.

Two 17 ML batch ponds which are used in parallel and provide residence time for the treated water to settle.

Pump Station 3 with a capacity of 150 L/s to transfer treated stormwater to Suma Park Dam. The treated stormwater is transferred through an existing main towards Suma Park Dam, with an extension allowing discharge to the dam.

STORMWATER 2010 National Conference of the Stormwater Industry Association Conference Proceedings

Figure 2: Scheme Layout

Monitoring

The scheme is intensively monitored to obtain data to quantify the scheme performance in terms of harvest yields, changes to downstream flows and water quality. The monitoring system includes (refer to Figure 2):

Four rainfall pluvio stations across the catchment; Three stream flow gauging stations: upstream of Suma Park Dam, immediately downstream of the harvesting weir in Blackmans Swamp Creek and in Summer Hill Creek about 8.6 km downstream of the harvesting site (known as the Third Crossing); In-line flow meters in the transfer pipe from Pump Station 1 to the holding pond and in the pipeline from Pump Station 3 to Suma Park Dam; and Four main water quality monitoring points.

Water quality samples are obtained from the raw stormwater in Blackmans Swamp Creek just downstream of the harvesting weir (identified as Site 11), from Suma Park Dam (Site 14) to establish the existing quality of the water supply and from two depths at each of the two batch ponds (Sites 16 and 17). Samples can also be collected from the holding pond. This range of sampling sites allows comparison of quality of the untreated stormwater, treated stormwater prior to release and the quality of the water obtained from the natural catchment.

INITIAL OPERATION

The scheme was commissioned in March 2009, with the first harvest event occurring on 4 April 2009. The first harvested water was transferred to Suma Park Dam on 21 April 2009 following testing and verification that scheme water quality targets had been met. The following sections present a review of the first 16 months of the scheme operation.

STORMWATER 2010 National Conference of the Stormwater Industry Association Conference Proceedings

Quantity

There were 52 harvesting events between 4 April 2009 and 10 August 2010. The total volume harvested over this time was 906 ML which is equivalent to approximately 15% of the city s current annual water demand (under Level 5 restrictions). The 16 months in which the scheme has operated coincide with another dry period (i.e. less than the long term average annual rainfall).

Figure 3 shows the daily flow in Blackmans Swamp Creek as recorded at the stream gauge downstream of the harvesting weir. The difference between the inflow and downstream flow represents the volume extracted by the harvesting scheme.

Blackmans Swamp Creek

Inflow to Harvest Weir Downstream Flow in BSC

300

250

200 y a d / L

M 150 , w o l F

100

0 9 9 9 9 9 0 0 0 0 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 0 0 0 0 0 0 0 0 1 1 1 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 1 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 / / / / / / / / / / / / / / / / / / / / / / / / / / / 4 5 8 9 0 1 2 3 4 4 5 5 6 6 7 7 8 9 0 0 1 1 2 2 1 2 3 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 1 1 1 1 1 1 0 0 0 / / / / / / / / / / / / / / / / / / / / / / / / / / / 4 2 8 5 3 9 6 6 3 8 6 0 3 7 1 5 2 9 7 1 4 8 2 6 3 0 0 1 1 3 1 2 1 2 2 1 1 3 1 2 1 2 2 2 2 Figure 3: Daily flow Blackmans Swamp Creek 4 April 2009 to 3 April 2010

Quality

The two gross pollutant traps removed approximately 800 tonnes of litter, rubbish and organic matter from Blackmans Swamp Creek in the first year following installation.

Intensive monitoring of the scheme is establishing a database significant to the Australian stormwater industry. Monitoring has indicated that concentrations of analytes were significantly reduced in the batch pond samples compared to the raw creek water samples.

Table 1 provides a summary of some of the water quality data. This table includes the mean results for the raw creek water (during harvest events), the batch pond water following treatment and the water in Suma Park Dam. The data shows that while the raw stormwater quality varies between events, the relatively simple treatment process is resulting in water quality that meets the scheme targets and is predominantly of better quality than the water in the main water supply dam, in many cases also meeting Australian Drinking Water Guidelines prior to transfer to Suma Park Dam and advanced treatment for distribution. The operational data confirms that stormwater is a reliable and viable alternate water source for Orange.

STORMWATER 2010 National Conference of the Stormwater Industry Association Conference Proceedings

Table 1 Summary of example water quality data

Mean

Analyte Unit Scheme Raw Creek Suma Park Targets Water Batch Ponds Dam (Version 6) (n=89) (n=48) (n=10) (95%ile)

Total suspended solids mg/L 6 4 4 < 29 Turbidity NTU 8.5 1.64 3.71 < 30 Salinity µS/cm 116 119 204 < 300 pH pH units 6.06 7.48 7.65 6.5 to 8.5 BOD mg/L < 2 3 2 < 10 Total phosphorus mg/L < 0.01 0.012 0.048 < 0.2 Total nitrogen mg/L 0.3 0.80 0.85 < 2 Iron mg/L 0.5 0.04 0.13 < 0.3 Total Manganese mg/L 0.047 0.032 0.097 < 0.1 Lead mg/L 0.002 0.001 BDL < 0.05 Aluminium mg/L 1.67 0.12 0.04 < 0.2 Bromide mg/L < 0.01 0.023 0.045 < 0.1 Cadmium mg/L <0.0001 0.0001 0.00042 < 0.002 Oil and Grease mg/L < 2 3 BDL < 2 Escherichia coli CFU/100mL 120 81 19 < 1,000 Somatic coliphages pfu/100mL 170 90 40 < 1,000 Clostridium perfringens CFU/100mL 84 12 3 < 1,000 Total Petroleum Hydrocarbons µg/L < 220 125 BDL < 1000 Benzo(a)pyrene µg/L < 0.005 BDL BDL < 0.01 Naphthalene µg/L < 0.02 0.02 BDL < 16 Total PAHs µg/L 0.018 BDL BDL < 0.01 BDL = Below Detection Limits

CHALLENGES

Key issues raised during the assessment and approval of the scheme were the risk associated with transferring stormwater into the city s raw water supplies, acceptance of the concept and design, the effects on the downstream creek environment in terms of changes to flow regimes for downstream users and the potential impacts on creek ecology and the project s urgency.

STORMWATER 2010 National Conference of the Stormwater Industry Association Conference Proceedings

Water Quality Risks

Assuring consistent water quality was a key component in the success of the scheme and managing the risks to the community that accompany the collection of urban runoff for addition to potable supplies was a complex task. The absence of relevant established data relating to analysis and typical qualities of urban stormwater presented a challenge when assessing the nature of the catchment runoff and the range of potential contaminants to incorporate in the monitoring program. Therefore it was necessary to undertake a catchment audit and compare this to a range of guidelines available for various uses. A hierarchy of significance to the ultimate use of the harvested stormwater was developed, with the Australian Drinking Water Guidelines taking priority. This was a conservative approach given that harvested stormwater was to be added to natural catchment water before being treated to drinking water standards and distributed to the City. This conservative approach assisted in further building the confidence of regulators and the community. A treatment train approach was also utilised to incorporate a variety of barriers to pollutants entering the town water supply.

The harvesting scheme was designed with an integrated suite of catchment, system and operational barriers to manage water quality and the risks associated with using stormwater to supplement the water supply. These barriers include:

Catchment level implementation of plans and policies to protect stormwater quality including a Stormwater Management Plan, a Sewer Asset Management Plan and a Trade Waste Policy. The scheme provides an opportunity for community education regarding stormwater and catchment management. The primary Gross Pollutant Trap (GPT) is installed in a prominent location where residents can observe functioning and downstream benefits. Interpretative signage is installed at key locations throughout the scheme. System level a treatment train approach incorporating a series of system components designed to remove pollutants in the stormwater. Operational level operation of the system in a manner that optimises the quality of the stormwater.

Water quality risk management was formalised through the implementation of the Framework for the Management of Drinking Water Quality (NHMRC & NRMMC, 2004), which involved systematically assessing where and how contaminants may arise, how they may reach the consumer and how to protect the consumer from such contamination. The implementation of the Framework involved establishing a stakeholder group comprised of Council staff, NSW Health, the Department of Water and Energy, the Department of Environment, Climate Change and Water and technical advisors who assessed hazard identification, risk assessment and critical control points. This process identified 100 risks throughout the water supply system for which 17 control points and 10 supporting programs were defined to manage the residual risk.

A key component in the development of the drinking water quality risk management plan was demonstrating that the water supply system can adequately remove pathogens prior to delivering potable water to the community. Assessment of the water supply system, including the addition of the harvested stormwater, demonstrated that the barriers and process steps in place more than satisfy guideline requirements (refer to Table 2).

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Table 2- Pathogen log reduction values

Process Step Protozoa Viruses Bacteria

Holding Pond 0.5 0.5 0.5 Batch Pond 0.5 0.5 0.5 Suma Park Dam 1.0 1.0 1.0 Icely Road Water Treatment 4.5 9.0 10.0 Plant Total log reduction achieved 6.5 11.0 12.0 Log reduction required 4.9 5.5 5.4 Margin of safety 1.6 5.5 6.6 Source: adapted from Water Futures (2009)

Water quality targets are an essential component of risk management. The treated stormwater is analysed for 167 parameters for which quality targets have been set. Sources utilised in setting the targets included the Australian Drinking Water Guidelines (NHMRC & NRMMC, 2004), the Australian and New Zealand Guidelines for Fresh and Marine Water Quality (ANZECC & ARMCANZ, 2000), Australian Guidelines for Water Recycling (EPHC et al, 2008), Australian Runoff Quality: a Guide to Water Sensitive Urban Design (Engineers Australia, 2006) and Guidelines for Drinking Water Quality (WHO, 2008). The quality of water existing in and entering Suma Park Dam was also considered when setting the scheme targets.

Acceptance

The innovative nature of the stormwater harvesting scheme and subsequent lack of precedents meant that engagement of the community, stakeholders and authority departments was an essential component of the scheme development. Acceptance of the concept and trust in the processes involved in achieving water treatment to an acceptable level was critical. In addition to health risks, the scheme was required to be developed in a manner that caused minimal environmental impact to downstream ecology and other users. A group of stakeholders was established to facilitate the development of operational procedures and to encourage transparency and mutually acceptable solutions.

Community resistance to the concept of drinking stormwater was initially thought to be a significant challenge. However, through community education on the treatment processes and the necessity for securing the future of Orange s water supply, community acceptance was achieved relatively quickly and easily. Local and national media coverage, community information sessions, on-line surveys and explanatory signage at key locations were important factors in ensuring the concept of adding stormwater to the potable supply was widely accepted by residents. The predominant response was not one of concern about water quality but one of urging Council to proceed with the work as soon as possible.

Flow Regimes

Water licence holders downstream of the scheme raised concerns that stormwater harvesting would compromise their ability to access their water entitlement. Creek care and environmental groups were concerned that changes in flow regimes would impact on the creek ecology. Continuity of adequate flows

STORMWATER 2010 National Conference of the Stormwater Industry Association Conference Proceedings within the creek, including periodic high flow events that flush the system are considered important for conservation outcomes.

Excess harvesting of too much stormwater at inappropriate times has the potential to cause a significant impact downstream. The scheme therefore operates under a set of operating rules designed to prevent detrimental impacts from occurring. Low flow events in the system, being those that occur for more than 80% and 90% of the time, are untouched. It is the less frequent flows, those that occur for only 20% or 10% of the time that are reduced by the scheme. The intent is to harvest the peak from these higher flow events as conditions permit.

This impact is reflected in Figure 4 which shows the flow duration curves upstream and downstream of the harvesting weir for the 12 months from 4 April 2009 to 3 April 2010. These data show:

Low flows, or those occurring more than 90% and 80% of the time are not changed. These represent the base flow; There is no significant change in the daily flow until the less frequent flows, or those occurring 20% or 10% of the time; these are reduced by the harvesting scheme; and The maximum and peak flows are being reduced slightly which is a benefit to the downstream creek system in minimising erosion.

Data obtained from the scheme operation is used to inform the stakeholder group and forms the basis for possible modifications to the operating rules and management of water supplies.

Blackmans Swamp Creek

Downstream of Harvest Weir Inflow to Harvest Weir

300

250

200 y a d / L

M 150 , w o l F

100

0 0 10 20 30 40 50 60 70 80 90 100

% o f time flow is exceeded Flow duration curves 4 April 2009 to 3 April 2010

Urgency

The urgency of the project required efficient and thorough analysis of options as well as effective project management to secure relevant approvals and meet legislative requirements. Council formed a project team

STORMWATER 2010 National Conference of the Stormwater Industry Association Conference Proceedings of experienced staff and trainee engineers under the guidance of Council s Operation Manager. Consulting engineers provided a critical link between the detailed design and on-site construction. The team was given a clear mandate to focus solely on project delivery.

The works comprised eight separate major sub contracts ranging from bulk earthworks to complex electrical and pump installations. The team delivered the $5.0 million project on time and within budget, with no major contractual, OH&S or environmental issues. Council received the necessary authorisation from the Department of Water and Energy in July 2008 to commence construction under an emergency authorisation. Construction work commenced in October 2008 and was completed in 6 months, with the first harvested stormwater transferred to Suma Park Dam on 21 April 2009 (Figure 5). Delivery of the project from concept to operational reality took approximately 18 months.

Funding of the stormwater harvesting scheme was another significant challenge, with the project forecast to cost $5 million in capital works. State drought relief funding was secured, with Orange City Council and the State Government financing the project dollar for dollar. The use of existing infrastructure assisted in the financial viability of the project, with the utilisation of existing road access, adequate power supply and a pipeline connecting the creek and Suma Park Dam.

Figure 5: The first release of harvested stormwater flows into Suma Park Dam on 21 April 2009

FUTURE OPPORTUNITIES

Council is currently in the construction phase of establishing other harvesting schemes on additional local creeks which will utilise structural components of the BSCSHS. These additional schemes have the potential to add an average of about 700 to 800 ML/year to the scheme. The Ploughmans Creek Stormwater Harvesting Scheme is under construction and has a number of features which distinguish it from the Blackmans Swamp scheme. Operational data and experience has been applied to the design of the Ploughmans Creek scheme to

STORMWATER 2010 National Conference of the Stormwater Industry Association Conference Proceedings increase harvesting capacity and pre-treatment quality. The most significant of these changes is a series of constructed wetlands which will provide natural filtration as well as allow harvesting to occur for a longer period following rain events.

This expansion will further reinforce stormwater as a key component of Orange s integrated water supply system.

CONCLUSION

The BSCSHS is simple in concept and makes use of existing infrastructure. The scheme is a basic series of pumps and pipes which transfer water from one place to another. The complexity of the project lies in ensuring the scheme was designed and is operated in such a way that ensures the concerns of key stakeholders are met; ensures that drinking water quality is not compromised and demonstrates that stormwater can be accepted as a viable resource to supplement potable water supplies.

The project evolved from problem identification to operational reality within 18 months whilst meeting the necessary legislative, environmental and community consultation requirements, on time and within budget. The scheme has been in operation for 17 months, providing over 900 ML to the City s water supply and is an important milestone in the development of an integrated system designed to secure Orange s future water supply.

Extensive data collected from the scheme provides valuable information on stormwater quality from urban catchments and the effectiveness of simple stormwater treatment in supplementing potable supplies. The Blackmans Swamp Creek Stormwater Harvesting Scheme provides a model for consideration throughout Australia and abroad.

This original project involves using a sometimes forgotten water resource, urban stormwater, to supplement potable supplies. The critical water supply situation allowed Orange City Council to apply innovative thinking and to raise the profile of stormwater, getting stormwater out of the gutter and into the potable supply.

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REFERENCES ANZECC & ARMCANZ (2000). Australian and New Zealand guidelines for fresh and marine water quality. National Water Quality Management Strategy. Australian Government, Canberra, Australia. Dillon, P., Page, D., Pavelic, P., Toze, S., Vanderzalm, J., Barry, K., Levett, K., Regel, R., Rinck-Pfeiffer, S., Pitman, C., Purdie, M., Marles, C., Power, N. and Wintgens, T. (2008a). City of Salisbury s progress towards being its own drinking water catchment. Proc. IWA Intl Water Conf, Singapore, 23-27 Jun 2008. Dillon, P., Page, D., Vanderzalm, J., Pavelic, P., Toze, S., Bekele, E., Prommer, H., Higginson, S., Regel, R., Rinck-Pfeiffer, S., Purdie, M., Pitman, C. & Wintgens, T. (2008b). A critical evaluation of combined engineered and aquifer treatment systems in water recycling. Water Science and Technology 57(5): 753-762. Engineers Australia (2006). Australian runoff quality: A guide to water sensitive urban design. Engineers Australia Publications. EPHC NHMRC NRMMC (2008). Australian Guidelines for Water Recycling: Managing Health and Environmental Risks. Phase 2A. Augmentation of Drinking Water Supplies. (Environment Protection and Heritage Council, Natural Resource Management Ministerial Council and National Health and Medical Research Council), Canberra. Geolyse Pty Ltd (2008). Blackmans Swamp Creek Stormwater Harvesting Review of Environmental Factors. Orange City Council. NHMRC-NRMMC (2004). Australian Drinking Water Guidelines. National Water Quality Management Strategy. Australian Government, Canberra, Australia. Vanderzalm, J., Dillon, P., Marvanek, S. and Page, D. (2007). Over 100 years of drinking stormwater treated through MAR: assessing the risks of stormwater recharge on the quality of the Blue Lake. p616-625 in Procs ISMAR6, Phoenix 28 Oct-2 Nov 2007, ed. P. Fox, Acacia Publishing, Phoenix, Arizona. Water Futures Pty Ltd (2009). Water quality risk assessment and critical control points, Workshop summary paper Version 3. Orange City Council. World Health Organisation (2008). Guidelines for Drinking Water Quality, 3rd ed, Geneva.