Developers are planning to dump a staggering 22.7 million tonnes of soil at Penrith Lakes in a controversial bid to raise the flood-prone site by up to three metres. The goal is to elevate the land to protect future developments from extreme flooding, but the proposal is already under fire.

The site, located at 89-151 Old Castlereagh Road, sits within the Hawkesbury-Nepean floodplain, one of Australia’s most dangerous flood zones. The proposed changes would see the site raised by an average of 1.32 metres, with some areas elevated by nearly three metres. 

A consortium of major players, including Boral, Holcim, Hanson, and the Kerry Stokes-owned Seven Group owns the Penrith Lakes site. They want to develop the site for housing, commercial uses and recreation spaces however, its location on a floodplain has made these ambitions increasingly contentious.

The developers submitted the proposal as a State Significant Development which effectively streamlines the planning process and bypasses local council assessment. They argue that raising the land levels would protect future development against a one-in-500-year flood, a measure far exceeding current planning levels.

Developers already have approval to bring in 13 million tonnes of fill but want to increase this by 9.7 million tonnes, arguing it would safeguard the eastern portion of the site against catastrophic floods while causing “no fundamental change” to existing flood behaviour. However, many remain unconvinced.

Regulators, including the Environmental Protection Authority, Penrith Council, and the Department of Planning, have called for detailed studies, particularly a comprehensive flood analysis.

 “The modification application as submitted proposes to import fill to enable part of the Penrith Lakes site to be flood-immune in the 0.2% AEP flood event,” wrote the Department of Planning in a letter to the developer.

 “The additional fill is proposed to be over the 0.2% AEP flood level for much of the site, with the fill being more than 2.5m above the identified 0.2% level. The Department requires rationale for filling to such a significant amount above the 0.2% flood level,” it said. The Department added it wanted more information about the proposed final landform at the site.

Critics also point to the short exhibition time for public feedback. The community was given just 13 days to review and respond to the plans, which closed in late November.

NSW Premier Chris Minns has publicly opposed building on flood-prone land, warning that such developments pose serious risks to safety, insurance, and financial stability. “You’re putting people and communities in danger,” Minns told the Hawkesbury Post in 2023. Despite these warnings, large-scale projects like Penrith Lakes continue to move forward, fuelling accusations of double standards.

Tens of thousands of Hawkesbury residents, living below the one-in-500-year flood level, face heavy fines for importing fill to raise their flood-prone properties, while large developers appear to operate under far more lenient standards. A one-in-500-year flood would reach 20.2 metres at Windsor, surpassing the 19.7 metres recorded during the historic 1867 flood, the largest ever to hit the region.

The developers’ report, prepared by consultants Water Technology, insists the project will have no major impact on flood behaviour at the site. However, the study fails to assess potential downstream impacts on Hawkesbury communities, nor does it consider the effects of climate change or changes to stormwater runoff. 

“Given these minor increases which occur in extreme flood events, the model results indicate no fundamental change to the existing flood behaviour at the site,” the report claims.

The Penrith Lakes Scheme, established in 1987 under a Deed of Agreement with the NSW Government, was intended to transform the area into a model of urban living. However, shifting flood mapping and growing concerns about safety have repeatedly challenged this vision. 

Former Penrith MP Stuart Ayres, who once promoted the vision of homes “as far as your eye can see,” later reversed his stance, publicly stating that large-scale development was no longer feasible.

Ayres now serves as CEO of the Urban Development Institute of Australia’s NSW branch, a vocal critic of stricter floodplain planning restrictions.

The developer was granted approval in 2014 to bury 23,500 cubic metres of waste - including concrete, tyres, plastics, and demolition debris - on-site rather than removing it. This included 12,000 cubic metres of asphalt and road materials. 

The broader issue of flood management across the Hawkesbury-Nepean Valley remains unresolved. Successive governments have failed to deliver meaningful mitigation measures, from the controversial - and unfunded - Warragamba Dam wall proposal to debates over raising flood planning standards. Increasing these standards, such as shifting from one-in-100-year to one-in-200-year flood levels, could devastate property values in flood-prone areas, making insurance and banking services inaccessible.

This artist's impression of the Penrith Lakes project was included in the new modification application by developer consultant ARUP.

The maps below compare flood impacts at the site. The first illustrates current flood modelling depths for a 1:500 event, while the second shows the projected impact after adding 22 million tonnes of fill.

The image below shows the current zoning at the site. The large pale blue area is currently unzoned.

The map below shows the site subject to the new development application.