The City of Mandurah is fighting the claim by local environmental group Bouvard Coast Care that the proposed Tims Thicket spraying field could potentially pollute residential bore water.
Despite acknowledging the proposed spraying site would be located in an old landfill site, City chief Mark Newman denied the group’s claim that toxic chemicals and asbestos were buried in the site.
“The proposed area for the spray irrigation is an old landfill site that was used for the acceptance of inert material during the late 1990s,” he said.
“There is no evidence to support the residents’ concerns that the waste water would contaminate nearby aquifers.”
However, Bouvard Coast Care group members said there was photographic evidence of hard waste being dumped in the area, including gas bottles, white good, heavy metals, chemical drums and asbestos throughout the late 1990s.
The group was concerned that passing large quantities of waste water through the site, which is located on a highly porous Tamala limestone soil, could cause toxic contaminants to leach out into the water and seep down into the aquifer bellow.
Mr Newman said the treated waste water would be sprayed via a sprinkler system onto an area planted with Vetiver grass, a very efficient type of grass in removing nitrogen and phosphorus.
He said the system wouldn’t be used on a daily basis but rather during heavy rainfall periods when the facility’s ponds are more likely to fill up.
According to Mr Newman, the nearest house is located 1.2km east of the site with ground water flow in the area generally moving west towards the Indian Ocean.
He said the proposed facility upgrade would allow Mandurah to treat all liquid waste generated in the city, instead of having to transport it to Perth.
“Disposal of septage is a costly exercise for the community,” he said.
“The new facility would allow liquid waste from the region to be treated locally, thus bringing significant cost savings to residents.”
He said the City had worked with its waste management consultants to design the upgraded facility to meet with the current environmental standards and minimise any impacts on the environment.
“It’s disappointing that the Bouvard Coast Care group did not come to the City first with their concerns, we’re organising to meet with them to discuss their concerns,” he said.
The Tims Thicket waste management facility upgrade proposal is currently being assessed by the Department of Water and Environmental Regulation (DWER) and the Environmental Protection Authority (EPA).
However, in a public record document dated from July 2017, the EPA acknowledged the facility had impacted the area’s groundwater and said there was the potential for additional groundwater impacts if the facility wasn’t managed appropriately.
It is anticipated a resolution will be announced in the next few months.