The Nursery site processes green waste which is produced by council operations and various landscape businesses into mulch. The stormwater runoff generated in the storage and processing area contains pollutants; it cannot be discharged offsite based on EPA’s Environmental Protection Policy. To achieve acceptable water quality standard, treatment of runoff is required.

 

Adelaide City Council is considering in-ground storage followed by treatment. However, potential issues are: Treatment system needs to cater for irregular storm events. Contaminated soil at site of proposed in-ground storage. Therefore, investigation and development of strategy are required for: Collection and treatment of contaminated runoff from the processing area on the nursery site; and Stormwater management for the reminder of the nursery site.

 

The runoff from the processing area can be solely considered as rainfall runoff. The drain running through the processing area is contaminated soils and green waste by-products. The processing area has not been bounded, and the runoff from the operation area flows freely into the drain. The existing Gross Pollutant Trap (GPT) is relatively small, which has limited inflow capacity (and subject to blockage from coarse solids / sediment) that is evident by water ponding. Overflow from the site (western end site) is via a GPT and small depression, occurs three to four times each year. There is an existing infiltration system at the nursery site, which was used for previous trials to improve water quality by treatment of River Torrens water. The system consists of:  Two 25 kL storage tanks, biological filtration system comprising five foam bio-filters, Pumps, Reticulation infrastructure and  an A-pump/rising main to extract and return treated water to River Torrens. This system is currently decommissioned. The bio-filtration system seems to be in poor condition with excessive accumulation within the modules.