Developer Stockland wants to build about 1000 homes on 115ha of land on Bong Bong Rd at West Dapto, part of a five-stage, 19,000-home development of the area, near an old coal mine.

But a former coal wash storage area may pose problems for “combustibility” and lead contamination, with asbestos also being detected in the soil.

An extensive remediation plan has now been prepared by consultant Cardno, which tested the land and identified four potential areas of environmental concern.

High on the list was the 16ha, 20m deep former coal rejects storage area, as well as old buildings, stockpiled materials, and spent munitions from the former Illawarra Gun Club to the east of the development site.

The main area of concern was the land near the former gun club, where lead was found in the surface soil at levels more than six times the accepted health limits.

Cardno said there were also concerns about “combustible content” of coal wash areas which would need further investigations.

But the consultant advised the land could be made suitable for residential use with further assessment and management.

“Further assessment and delineation of the lead concentrations in soil is recommended to assess the potential for the lead concentrations to pose a risk to human health and the environment in the context of a low density residential land use,” Cardno’s report stated.

“Further intrusive investigations” of soil, groundwater and surface water would be needed before the site could be made suitable for residential use.”

Other heavy metals were found in levels which were below the assessment criteria, Cardno’s report said, and while there had not yet been problems with coal wash combustion, it should be monitored.

“Geotechnical and contamination studies have established that the material within the [coal storage area] exceeds the allowable thresholds for combustion,” Cardno’s report stated.

The development application is open for comment until January 22.