Making mud stick keeps our rivers clean
  • Wednesday 08 April 2009

A partnership between the Sunshine Coast Regional Council and members of the local development industry is closing the gap between the muddy realities of construction sites and community expectations for clean waterways and beaches.

Muddy water is not only an eyesore, it can suffocate fish, smother habitat and disrupt aquatic food webs.

Using new technology on an urban subdivision for the first time in Australia, Council and local civil contractor, Blacklaw Civil, consulting engineers, Coffey Geotechnics and developer, Urban Pacific, has successfully trialled a ‘state-of-the-art’ sediment capture basin and automated chemical dosing system to make sure soil stays on site where it belongs.

Initial monitoring of the basin at Urban Pacific’s Forest Glen development has shown 99% sediment removal efficiency.

Muddy water entering the basin at over 2000 turbidity units typically leaves the basin at less than 20 units. Coupled with tight erosion prevention measures, the new system has exceeded all expectations.

The new system has three elements -

  • a highly efficient sediment basin which minimises turbulence, trapping sediment more effectively
  • a chemical dosing system which is automatically triggered by rainfall
  • a floating outlet which draws clear water continuously from the surface of the basin and sends it to the creek nearby.

The chemical, calcium chloride, has no impact on the environment, but it binds to the small sediment particles and causes them to sink to the bottom of the basin.

Environment Portfolio Councillor, Keryn Jones said that with improvements to sewage treatment systems, and programs to revegetate river banks, the health of our waterways is now largely determined by the quality of water that runs off the land when it rains.

“Minimising sediment pollution from construction sites is one of the last remaining hurdles to getting our rivers back to a healthy condition” Cr Jones said.

“If you live on the coast you know how heavy the rainfall can be.

“Without proper planning and management a construction site can lose over 200 tonnes of soil from each hectare of disturbed land over a 6 month construction period. That’s 20 truck loads per hectare!

“The good news is this system makes mud stick where it needs to, on the site, instead of flowing into our rivers.

“The trapped sediment is removed, dried and returned for use as fill material on-site.

“The other benefit is that it’s cost effective, because it reduces down time and the need for constant hands-on management, making it of benefit to the construction and development industry as well as the environment.”