UNDERGROUND tanks and contaminated soil at the old depot site in Donnybrook will be removed before a residential development goes ahead.

Donnybrook-Balingup Shire Council chief executive officer John Attwood said the old depot site is earmarked for future high density residential development.

However, disused underground petrol storage tanks at the site are causing concern. While the results of previous testing at the site showed no significant risk from the soil, groundwater results were inconclusive.

According to the shire’s February ordinary meeting minutes, hydrocarbons, a pollutant present in crude oil, were detected in close proximity to the storage tanks.

Mr Attwood said while the tanks held petrol in the past, they have not been used for some years, and would be removed as part of the development.

He said it was unclear whether the hydrocarbons came from the tanks.

“There was a power station there at some stage, it could be a small amount of leakage of oil over a period of years,” he said.

He said if this was found to be the case it would be removed as part of council’s requirements to make the site clean. There was also a possibility of some leakeage from the tanks.

“Until we do further investigation or take the tanks out we don’t know the extent of it or where the hydrocarbons have come from,” he said.

According to the shire, further sampling is needed in the area surrounding the tanks to determine the full extent of the plume.

A stormwater drain system in the area that discharges directly onto adjoining property is also located adjacent to potentially contaminating activities, including the old bowser, vehicle storage area and pesticide storage area.

A consultant employed by the shire has recommended that further investigations be undertaken to discover the extent of soil and groundwater contamination around the underground storage tanks and that soil testing is carried out in the area where the storm water drains discharge.

Additional groundwater monitoring bores will be installed and groundwater sampling undertaken to determine the extent of any residual groundwater hydrocarbon contamination after the removal of the tanks.

The removal will be done in consultation with DEC.