We provided geotechnical and hydrogeological design plans to rezone the site from special rural to urban residential.

Calleya Residential Estate

Twenty-five kilolmetres away from Perth, you’ll find Treeby, a growing city surrounded by natural bushland and the Jandakot Water Mound—an underground aquifer supplying about 40 percent of Perth’s municipal drinking water. Above the aquifer, you’ll find the Calleya Residential Estate, one of Western Australia’s first residential developments to be constructed on top of a designated drinking water source.

Before construction began, we were commissioned to assist the rezoning from special rural to urban residential by providing detailed preliminary geotechnical and hydrogeological investigations. In a first-of-its-kind project, we used software called XP-SWMM (stormwater management modelling) to demonstrate how water would be managed on the site. We developed an innovative method of testing and screening existing soil, removing contaminants, and replacing the soil—by reusing existing soil, earthworks were minimized and building could begin sooner. And with housing lots sitting atop the aquifer, best-practice stormwater management allows water to drain slowly back into the aquifer, reducing the impact of fast water overflow and soil erosion.

By releasing housing lots to the market earlier than expected, our systems delivered cost-effective results for the client and the community. The Calleya Residential Estate project demonstrates that it’s possible to build a major residential development on top of an aquifer in a cost-effective, environmentally mindful way by reusing existing soil and designing effective drainage solutions to manage stormwater.