VISION: A concept of the Twin Waters West development.
VISION: A concept of the Twin Waters West development.

Toxic soil concern for major development

STOCKLAND faces significant acid sulphate issues on its Twin Waters West development site with the State Assessment and Referral Agency (SARA) seeking details of how it intends to treat 950,000 cubic metres of highly-contaminated soil.

The Department of Environment and Science has written to the developer saying the proposed ground disturbance fell within the "extra high level of treatment" category as described in the Queensland Acid Sulphate Soil Technical Manual (QASTM).

Treatment would require the use of more than 25 tonnes of calcium carbonate, the active ingredient in agricultural lime.

SARA said significant soil treatment was required to neutralise excavated soil (estimated liming rate of 16 - 143 kg lime per cubic metre of soil).

"For treatment of large volumes of material, neutralisation should occur on a treatment pad," the agency wrote.

"No information has been provided which outlines the construction of the treatment pad or how the applicant proposes to manage the treatment activities."

Concerns were also raised about groundwater which was currently only a metre deep and the proximity to surface water bodies and groundwater dependant ecosystems.

Stockland has been given until August 30 to respond to the State Government on the issue as well as matters relating to tides, stormwater discharge and responsibility for the ongoing maintenance of the constructed water body and discharge points to the Maroochy River.

In its letter to the developer's planners SARA advised that the Twin Waters West development application "has not adequately demonstrated compliance with the State Development Assessment Provisions".

The issues have been the subject of discussions between SARA, Stockland and its planner since early June.

SARA has advised a review of the development application documentation indicated the "potential for serious environmental harm to occur as a result of the proposed disturbance and potential oxidation of acid sulcate soils at the site".

"Insufficient information has been provided that demonstrates the risks associated with the disturbance of acid sulfate soils has been adequately considered and can be appropriately managed to prevent environmental harm," the State Assessment and Referral Agency wrote.

A spokesperson for developer Stockland said the company was preparing its response to the further information requests which they said was a normal part of the process post public notification.

"We're currently working through the points raised by the state and, given the comprehensive investigations we have undertaken on the site, we remain confident in the project," the spokesperson said.

"We will continue to work with the State government, Council and the community to finalise the further information required."

The referral agency noted the development application report had relied on the results of the historical acis sulphate soil investigationscompleted by environmental consultants.

"Although a brief summary of the findings of these investigations was included in the report, copies of the investigations, including the tabulated results of laboratory testing, has not been provided for review," SARA said. "Given that the applicant relies on this historical information to demonstrate that the site has been adequately investigated, it is considered warranted that copies of these investigations be provided to the department for review."

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