POTABLE STORMWATER HARVESTING, THE ORANGE EXPERIENCE

John Boyd, Operations Manager, Orange City Council

Abstract Fresh water is one of the world’s most precious resources. If 100 litres represents the world's water, less than a half of one teaspoon is fresh water available for our use (Brac Systems, 2009). With the impacts of climate change and population growth, the way water is managed and conserved is of critical importance. Orange, as with many other areas of , has over recent years experienced the impacts of drought and limited catchment runoff. With our water supply falling to less than 27% we needed to be resourceful and find our own solution to securing water for the City. With local resources and the support of the community, Orange City Council has now established an innovative stormwater harvesting scheme that challenges the historical view of stormwater as a waste product of the city. Stormwater is now seen as one of the City’s most valuable resources.

Key Words: Potable, Reuse, Stormwater, Harvesting, Orange, Blackmans Swamp Creek

Introduction navigate through the approval and For 5 years Orange City Council has utilised consultation process. water restrictions as one of its main tools to conserve the City’s dwindling water supply. From inception this project was delivered Even though conventional water conservation within 18 months with the first water being measures had been put in place, by the end transferred to Suma Park on 14 April of 2007 water levels had fallen to 40% with 2009. no rainfall of consequence predicted. Concern was so great by this time that worst The Problem case scenarios were under investigation by Orange is a regional city of approximately the State Government including the 38,000 people situated 260km west of possibility of hauling water to the city by road . It is served by two water supply or rail. , being Spring Creek Dam of 4,500ML capacity and with a capacity By August 2008 the water supply fell to the of 18,000ML. The City’s annual water critically low level of 26.7%, however by this demand over the last 10 to 15 years has stage Council’s Technical Services been in the order of 6000ML per year Department was well on the way to delivering peaking at 7100ML in 2002. Although an innovative stormwater harvesting scheme Orange has a relatively high annual rainfall that is unprecedented in Australian local compared to surrounding areas, its location government. at the top of the catchment severely limits the safe yield from our water supply dams. This scheme, shown in Figure 1, ultimately proposes to harvest up to 40% of the City’s In recent years the impact of drought has had annual water needs from Blackmans Swamp some effect on our water storage levels, Creek and store this in Council’s main water however it would appear that a more supply, Suma Park Dam. The delivery of this significant influence on our safe yield has project was extremely challenging, not only occurred as a result of a change in the because of the urgency required to complete characteristics of our catchment which has the design and civil works but also to seen less runoff entering our dams from a given rainfall event. Figure 1 – Scheme overview

In 2005 Council was fortunate enough to see 2008, The Department of Commerce Suma Park Dam fill to capacity. However by investigated more radical alternatives such as late 2007 the city’s storage had fallen below carting of water to the city. This was quickly 40% and significant resources were directed rejected as unfeasible. Parallel to these towards reducing consumption. local investigations Council had significant input into the concept of a regional water In an effort to manage demand, Council’s supply strategy and began to promote the best practice pricing (user pays) was benefits of networking major water storages. augmented by introducing level five water Initiated by CENTROC (a regional group of restrictions, community and business councils) this study is currently looking at education programs and water loss water on a regional basis with a view to better strategies. managing the resource.

With no predictions of significant rainfall it The evolution of the stormwater was quickly seen that demand management harvesting solution may not be enough to cater for our current With a view to recommission Lake needs let alone the potential growth of the Canobolas, civil design commenced along city. As a result, investigations commenced with a Review of Environmental Factors into opportunities to augment the City’s water (REF). This was accompanied by regular supply. Given there are no rivers in close brainstorming sessions under the guidance of proximity to the city, the options initially the Director, Technical Services (DTS), with investigated included groundwater and the staff trying to optimise designs and reuse recommissioning of Council’s original water existing infrastructure. These sessions were supply dam, (450ML). incredibly productive with innovative solutions coming from all disciplines within the When the City’s water storage reached department. alarming levels of less than 27% in August Early in the community consultation process Blackmans Swamp Creek stormwater however, it became evident that the utilisation harvesting project (total project cost $5m). of water from Lake Canobolas would result in significant resistance from downstream To develop the project further and deliver it landowners which would slow the approvals by the target date of March 2009, two process to a point where other alternatives interrelated processes occurred needed to be explored. simultaneously. One involved consultation, approvals and water quality which was In the past, urban stormwater in Orange had predominately pursued by the DTS and only ever received cursory consideration for Geolyse; the other was the design and any form of reuse. However the level of construction of the scheme which was urgency now required saw a rapid coordinated by the Operations Manager and convergence on the significant flows in project managed by Council’s Water and Blackmans Swamp Creek as a potential Sewer Overseer. The design itself was also source of potable water. While the carried out by Geolyse ensuring co-ordination catchments leading to our dams were highly of the two activities. dependent on antecedent conditions the large impervious area of the city was seen to Consultation and downstream ecology produce consistent flows following any given rainfall event. Early in the development of the project it was seen that community consultation would Our first concern with the concept of reusing require a significant investment of time and stormwater was water quality and public resources. While the overwhelming feedback health. After brief informal discussions with a from the residents of the City was “Just get leading industry expert in water reuse, we on with it”, downstream residents were more developed a degree of confidence that this cautious as to the impacts of the proposal. project was indeed plausible. This was Of particular concern was the volume of complemented by Council’s design staff water allowed to pass downstream. demonstrating potential storage scenarios in close proximity to Blackmans Swamp Creek The estimated annual runoff in the suggesting an engineering solution was also catchment’s “developed state” is 11,800 possible. ML/year and while, through modelling, it could be shown that the catchment in its To further develop the concept, Council “natural state” would only have produced an engaged local engineering consultants average of 5000ML of runoff per annum (in “Geolyse” who developed a detailed effect the city is a net contributor to surface hydrological model. This model water runoff), all impacts on users and the demonstrated that through a staged downstream ecology had to be based on the development, 20 to 40 percent of the City’s current conditions. annual water needs could potentially be gained through stormwater harvesting from A reference group of downstream Blackmans Swamp Creek. landholders was developed and through this group Council was able to explain that it had The development of the Scheme a genuine intention of maintaining the health In response to the City’s dwindling water of the downstream waterways and minimising supply, the Department of Water and Energy the impacts on stock watering and irrigation (DWE) began to assist in the development of from the creek. Even though modelling solutions as they were identified. With developed by Council’s consultants showed confidence that stormwater harvesting was a that the impact on downstream users would key component of a package of solutions be minimal, Council was still required to (both structural and non structural) DWE make significant compromises before approved a $4.7m grant on a 50:50 basis agreement could be reached. These under Emergency Drought Funding. Of this, compromises now form part of the operating $2.5 million was targeted to deliver the rules for the harvesting project and are incorporated into the project’s REF. These operating rules ensure that harvesting To this end, Council’s Environmental only occurs during peak flows and that base- Scientist facilitated Risk Management and flows in Blackmans Swamp Creek remain Hazard and Critical Control Point (HACCP) unaffected. Analysis workshops with Council staff and representatives from bodies such as DECC, Approvals DWE and NSW Health. The intent of these workshops was to protect consumers by To gain approval for this project, concurrence systematically identifying any potential for from many government departments was contamination of the system and develop required. This was achieved with the measures to ensure that these are assistance of DWE and developing a addressed. comprehensive REF that showed how each condition would be managed. While some of these measures were operational, many are extensions of our The approvals process has effectively been existing programs aimed at improving the pursued in two stages. The first was approval quality of water leaving the city. to commence construction under an emergency licence that was granted in July In addition, Council was fortunate to have 2008 and allows harvesting until Council’s ozone and a BAC filter as part of its water water storage increases to 50%. Under this treatment plant. While we were confident stage 1300ML of water per year will be that water entering Suma Park Dam from the transferred to Suma Park Dam. scheme would be safe, this treatment offered an additional level of confidence when Given the capital to be invested in the project, pursuing approvals. Council also made provision to ensure that the project could supplement the water Design and Construction supply over the longer term and has now The design and construction of the harvesting applied for a permanent approval that will scheme was an iterative process that allow harvesting above the 50% storage required significant co-ordination for a level. number of reasons. Firstly, the design needed to evolve in parallel to the REF and Stage two proposes a larger harvest storage complement its recommendations. Secondly, and is targeting the extraction of 2200ML of the timeframe involved did not allow the water per year. This represents only 18% of design of the total project to be completed the flow in Blackman’s Swamp Creek but before actions needed to commence. 40% of the City’s annual usage. To facilitate the delivery of this project It is to be noted that Council was not required Council’s Sewer and Water Overseer was to obtain additional volumetric entitlement via assigned as project manager and all of his a water licence to extract from Blackmans normal duties redirected. A project team of Swamp Creek as our current licence to Council staff was identified consisting of extract 7,800ML of water per year from the contract supervisors, treatment plant Macquarie Catchment was seen to cover this operators, engineers and electricians. This sub catchment. team met on a weekly basis with Council’s consultants (Geolyse) to optimise designs Water Quality and program works. As there was little precedent for stormwater One of the first tasks to take place was the harvesting similar to that which Council was development of a detailed Gantt chart based proposing, there was a need to demonstrate on the concept designs. This Gantt chart, that all reasonable measures would be taken which was gradually refined, identified the to ensure the safety of the public and that the anticipated dates of approvals, estimated chance of contaminating our main water component delivery times and construction supply was minimised. durations. The use of this programming technique was invaluable in ensuring the The harvest weir (Figure 3) was constructed project was kept on schedule and on budget. using gabion baskets and an earth core. It utilises a 300mm diameter unrestricted pipe Detailed design and contract documents to maintain creek base flows at all times. Its were not only developed based sequentially construction was facilitated by diverting the on the works as they were to be undertaken, creek around the harvest site; this also but as much considering the tendering allowed the construction of the main pumping process and lead times for the delivery of station to occur concurrently. products. In some instances components such as pumps and transformers were anticipated to take many months to arrive on site.

Construction commenced in October 2008. The largest component of the project was the earthworks contract which was undertaken concurrently with pipe laying, Gross Pollutant Traps (GPT) construction and pump station construction.

Earthworks

The earthworks contract consisted of the Figure 3- Pump station and harvest weir construction of a 200ML holding pond (Figure This contract also required the construction of 2), two 17ML batching ponds a harvest weir a submersible pumping station to transfer and pumping stations. Council’s Contracts water from the holding dam to the batch Supervisor was responsible for the delivery of ponds (capacity 150L/s) and a second pump this component of the works. The earth wall well to transfer water from the batch ponds to required 107,000m3 of selected material and Suma Park Dam (capacity 150L/s). Between was ultimately protected by 2000m3 of riprap the harvest weir and batch ponds a small from Council’s adjoining quarry. shed was constructed to house a coagulant dosing plant. This shed has the capacity to incorporate an inline mechanical filter if required in the future.

Pipe laying

The pipe laying contract was relatively straight forward, however the contractor did experience issues with rock and saturated soil from an adjacent dam. This contract consisted of laying 855m of 600mm DCI pipe, 560m of 375mm DCI pipe and 340m of 300mm DCI pipe.

Harvest Pump Station and electrical work Figure 2 – 200ML holding pond and batch ponds

The two batching ponds also shown in Figure Council utilised a local subcontractor to 2 required 23,000m3 of excavation and were construct the harvest pump station. This lined with 2000m3 of riprap. They have two pump station has a capacity of 450 L/s with off-take levels to allow either a continuous two duty pumps and a standby pump each extraction of water or complete emptying with a 225 L/s capacity. All electrical works in after the testing of individual lots (batch connecting the pumps to controllers, mode). telemetry and programming was undertaken by Council staff who have expertise in this In essence water along Blackmans Swamp area. Creek first passes through a gross pollutant trap which removes larger contaminants. Gross pollutant traps It is then pumped from the harvest weir on Blackmans Swamp Creek at a rate of 450L/s to the 200ML holding pond where some settling occurs.

From the holding pond the water is treated with a coagulant and allowed to settle in one of two 17ML batching ponds. Following testing and meeting the target water quality criteria this water is then transferred to Suma Park Dam.

Operation to date has been extremely encouraging with no difficulty experienced in achieving water quality targets. The following Figure 4 - Dalton Street GPT in operation graphs illustrate some preliminary results for a storm event occurring on 13 April 2009 Two large Barramy gross pollutant traps were where 8ML of stormwater was harvested incorporated into the system, not only to after 12mm of rainfall. improve the quality of the harvested water but also to improve the downstream aquatic Samples identified below as BSC - T1 to T4 environment. The GPT shown in Figure 4 is are from Blackmans Swamp Creek taken located on Blackmans Swamp Creek and is sequentially through the storm event with an one of the largest of its type, with the capacity 3 automatic sampler located near the to treat up to 10m of water per second. harvesting point. Batch ponds 1 and 2 Figure 1 shows the location of the two GPTs. demonstrate water quality prior to transfer to Suma Park Dam. The Suma Park Dam System Operation Samples are taken from the dam wall and are The basic operation of the system is shown in assumed to be representative of the supply. the following flow chart (Figure 5).

• Water from Blackmans Swamp Creek passes through a GPT with a capacity of 10m3/s • Second GPT screens water from notheastern suburbs GPT

TOTAL PHOSPHOROUS • A 3 ML holding weir contains water to be extracted at 450 l/s by pump station one. • A base flow of 2 M/L a day is maintained down streem via an unrestricted pipe passing through the weir 0.6 Harvesting weir • Pumping commences when flow over weir reaches 1000 l/s and ceases when flow Target, 0.5 falls to 150 l/s 0.5 0.39 0.4 • Holding dam stores water extracted from Blackmans Swamp Creek. • Preliminary settlement occurs in the holding dam while waiting to be treated in the 0.3 batch ponds 0.18 0.16 200ML holding • Holding dam is required to allow water from its own catchment to pass to Blackmans 0.2 0.13 dam swamp creek when no harvesting is in progress 0.1 0.06 0.01 0.01 • Water is treated with poly aluminium chloride before entering one of two 17Ml Batch 0 ponds. The capacity to screen water through a disk filter is available if required at a

later date PhosphorousTotal (mg/L) BSC-T1 BSC-T2 BSC-T3 BSC-T4 Pond 1 Pond 2 Suma Batch ponds • Water is settled in batch ponds and tested for quality (Batch mode) (Batch Mode) • Water is proposed to be regularly tested for quality (Continious Mode)

• Once water quality is verified (Batch mode) water is transfered to Suma Park Dam at a rate of 150 l/s (13ML/day) Transferr to Suma Park

Figure 5 - System operation

LEAD TURBIDITY

150 1.2 125 Target, 1 130 1 106 110 99.7 0.8 90 0.6 70 50 0.4 Target, 30 Lead (mg/L)Lead

Turbidity (NTU) Turbidity 30 0.2 9.1 0.023 1.5 1.2 0.015 0.008 0.006 0.001 0.001 0.001 10 0 -10 BSC-T1 BSC-T2 BSC-T3 BSC-T4 Pond 1 Pond 2 Suma BSC-T1 BSC-T2 BSC-T3 BSC-T4 Pond 1 Pond 2 Suma

MANGANESE E Coli

1.2 2000 Target, 1 1800 1 1600 1400 0.8 1200 Target, 1000 0.6 0.465 1000 800 0.4 0.294 0.208 600 0.122 (CFU/100mL)Coli E 400 Manganese (mg/L)Manganese 0.098 0.2 38 70 68 0.009 0.009 200 33000 45000 56000 24000 0 0 BSC-T1 BSC-T2 BSC-T3 BSC-T4 Pond 1 Pond 2 Suma BSC-T1 BSC-T2 BSC-T3 BSC-T4 Pond 1 Pond 2 Suma

Currently water is transferred in batch mode NITROGEN where every 17ML batch is tested for quality 6 before being transferred to Suma Park Dam. Target, 5 5 Based on the results to date, we are 4 encouraged that our ultimate goal of 3 continuous transfer will be achieved. 2 1.6 0.8 0.7 0.8 0.8 0.8 1 0.6 Downstream water quality has also improved Total Nitrogen Total (mg/L) 0 as a result of water passing through the BSC-T1 BSC-T2 BSC-T3 BSC-T4 Pond 1 Pond 2 Suma Dalton Street GPT. During the first 139 days of operation 68,920kg of material was removed from the GPT after a total rainfall of 296mm. A breakup of the material removed is shown in Figure 6. SUSPENDED SOLIDS

350 323 300 250 200 141 150 94 100 78 Target, 50 50 1 1 4 0

Total Suspended SolidsTotal (mg/L) BSC-T1 BSC-T2 BSC-T3 BSC-T4 Pond 1 Pond 2 Suma

the Ploughman’s Creek catchment to the POLLUTANT COMPOSITION West of the City. 139 days 296mm of rainfall The Blackmans Swamp Creek project was 68,920 kg of material largely based around large pumps extracting from a small harvest weir.

34% As the Ploughman’s Creek Catchment is different and downstream users have different concerns new solutions are being 52% pursued. In particular investigations and modelling are 7% based around larger storages incorporating 7% wetlands. It is anticipated that this approach will improve capture efficiency and minimise pumping infrastructure while also retarding flood flows and improve water quality. Sediment Other Rubbish Organics Conclusion

Figure 6 - Dalton Street GPT Performance We believe that the work undertaken to date has initiated a major change in mindset with respect to the reuse of stormwater at a community level. In addition, the information The minimal impact on downstream users that will flow from the operation of the resulting from the operation of the scheme Blackmans Swamp Stormwater Harvesting can be seen in Figure 7. This shows the after scheme will assist other Councils and harvesting hydrograph compared with the authorities in managing this valuable predicted hydrograph at the weir location. It resource into the future. also shows the hydrograph development further downstream. References  Brac Systems, (2009). “Without water there is no life” Retrieved May 28, 2009 from http://www.bracsystems.com/environ ment.html

 Geolyse, (2008). “Blackmams Swamp Stormwater Harvesting, Review of Environmental Factors”. Prepared for Orange City Council.

 Devitt, C. (2009). “Stormwater Harvesting for Potable use in Orange, Figure 7 – Blackmans Swamp Creek Hydrograph NSW”, IPWEA NSW Division Annual Conference 2009. The future The success of this project so far has inspired Council to pursue other opportunities for stormwater harvesting, in particular from

Author Biography John Boyd is currently employed as Operations Manager with Orange City Council. John holds a degree in Civil Engineering from the University of Technology Sydney, a Post-graduate Diploma in Local Government Engineering and is currently studying for a MBA.

John commenced his engineering career in 1982 at Parkes Shire Council where he was employed as a Junior Engineer. In 1990 John took the position of Deputy Engineer at Narromine Shire Council and subsequently commenced work with Orange City Council as Works Manager in 1994.

Postal Address: John Boyd, Operations Manager, Orange City Council, PO Box 35 Orange 2800

E-mail: [email protected]

Website: www.orange.nsw.gov.au