IPWEA Awards 2011

City of Greater Geelong – Grinter Stormwater Harvesting, Treatment & Reuse

Project Summary

Recycled stormwater and swimming pool backwash water has now replaced the potable water demand to sustain the irrigation requirements within Grinter Reserve, Geelong.  The innovative design diverts stormwater, roof water and backwash water through a treatment train then into a wetland before being reused as irrigation.  More than 30 million liters of potable drinking will be saved by this system and the sporting fields will now be drought proof.  The wetland has created a natural habitat for birds, fish and plants and the system is now treating the polluted stormwater that was previously flowing out to Corio Bay.

Project Description

Like many Councils Geelong was hit hard by the drought. Our water authority restricted all use of potable water on sports turf and as a result 56 sporting fields were closed due to being unsafe.  Grinter Reserve is one of the City of Greater Geelong’s bigger water user’s and following preliminary investigation it was identified as a potential site to capture and reuse alternative water.  Our primary objective was to secure an alternative water supply to drought proof the sporting fields and other uses within Grinter Reserve and save valuable drinking water.  While designing for this                                                                                                                                                                   objective we identified several other very beneficial opportunities, these included;

• The environmental benefit’s of reducing polluted stormwater and sewer discharge to the ocean.
• An unused and unattractive area of the reserve that attracted anti-social behavior and illegal rubbish dumping will be transformed into an aesthetically pleasing wetland and walking trail appealing to many visitors.
• The previous site offered very little biodiversity and it was proposed to create a natural habitat for birds, fish and indigenous plants.
• Spoil generated from the excavation will create a new sporting field or stage site within the Reserve.
• A walking path could link an interpretive signed tour of the project and create a pleasing experience.

The project’s outcome has exceeded our expectations in both recycled water yield for irrigation, aesthetic appeal for visitors and creating a habitat for flora and fauna.  In addition the site has interpretive signage and will become an educational experience for those interested in how the system functions.

A drought or water restrictions will not result in unsafe conditions or ground closure due to lack of irrigation at Grinter Reserve.  In addition, Council has the ability to irrigate space that may not have been considered prior to this project.  Additional active space for sport will encourage more participants and possibly other sports to the Reserve.

Several clubs are direct beneficiaries of this project.  The main user group of Grinter Reserve is the Newcomb & District Sports Club (Football & Cricket).  This club has 170 members and there grounds were closed during the worst of the drought severely affecting the clubs revenue, morale and participation.  Water restrictions and a drought will no longer affect this club.  The Geelong BMX Club’s base is also in the reserve and are now using the recycled water to wet down and consolidate their race track prior to club, state and national events.  This club has 60 members and in the past has needed to apply to the water authority to only receive a fraction of what they required to maintain the track.  A ‘Geelong East Men’s Shed group’ has recently formed who meet weekly in a newly constructed pavilion adjacent to the harvesting system.  This group will likely play an active role in looking after particular areas of the wetland and will likely require recycled water for gardens etc.  The Newcomb Whittington Moolap Riding Club who occupy 5 Hectares within Grinter Reserve have indicated they would like to irrigate there main show arena.

The system was very difficult to design because of the flat terrain and high water table.  Several innovative solution’s were incorporated into the project to capture and treat the stormwater.  We were adamant in our brief that the design wouldn’t require energy consuming transfer pumps and the system would be gravity driven.  The stormwater was diverted from a 200 hectare residential suburb then gravity fed along 500 meters of pipe through a gross pollutant trap then into a sediment pond already full of water.  Therefore the diversion pipework remains full of water at all times and it is only the height difference between the invert level of the diversion pit and the weir into the storage basin that pushes the water through.  The water flows through a marshland of varying depths to capture more sediment and remove nutrients etc before flowing into a 5 ½ million litre open storage basin.

The previous site was covered with noxious weeds adding very little biodiversity value to the area.  We planted 30,000 wetland plants propagated offsite from indigenous seed and genetic remnant vegetation growing within 30km of Grinter Reserve.

We were forced to be innovative with the spoil generated from the excavation as we didn’t have budget to cart it offsite to landfill.  An unused, rough area adjacent was used to create a flat pad shaped as a competition standard soccer field.  Other spoil was used to build a spectator mound along one side of the proposed soccer field that could stand hundreds of people if needed.  It has been discussed that the proposed soccer field site could also hold an entertainment stage or circus and the adjacent mound used to hold the spectators.

This iconic project has created many new working relationships for Council simply because it hasn’t been done before on this scale.  The project has enabled departments who wouldn’t normally require close liaison to work closely together to obtain the best outcome.  Four different departments will be involved in maintaining the asset including Parks, Irrigation, Environment and Drainage Works.

The total project cost was $860,000 which incorporates 10% design and investigation and the remaining construction.  The project’s inception was in 2008 as a concept idea and was commissioned and handed over in August 2010.  A payback analysis has been undertaken with this project using the cost of mains water saved which highlights that after 13 years the capital outlay for the project will be completely paid for.  Financially this project is attractive but most importantly the prime objective of drought proofing Grinter Reserve and conserving mains drinking water for better purposes has been met.  Participation by the hundreds of user’s of Grinter Reserve will not be restricted by the drought again which we anticipate will attract more active sport participants.  The reserve has even been transformed visually which will improve passive recreation for those interested in the aesthetic appeal of the wetland or the value of the flora and fauna.