This week we wanted to find out more about stormwater quality treatment technologies, so we contacted The Shaw Group. They have installed over 150 Continuous Deflection Separation (CDS) systems across the Maritimes. CDS units improve water quality of stormwater runoff by removing sediment, floatables, oil and grease.
|CDS unit (image:www.shawpipe.com)|
CDS units have a screen filter that removes all floatable materials and a separate treatment chamber which captures sediment and hydrocarbons. Due to potential high volumes of trapped pollutants, maintenance on these systems is very important. At a minimum they should be maintained twice per year, which includes sucking out the floatable debris and sediment with a vacuum truck.
We went to visit Portland Hills Estates, a large development surrounding Russell Lake, where several CDS units are installed at different stormwater outfalls around the Lake. We saw a ‘56/40 unit’, the largest CDS system which can filter up to 56 cubic feet of water per second. This system is designed to capture the 1 in 25 year storm (as opposed the 1 in 100 year storm), and as a result it functions very effectively 80% of the time. The other 20% of the time surplus flows through a by-pass valve.
|Let's life the lid and see what is inside!|
|Wow! Tennis balls, water bottles and several other floatables from the development and neighbouring school are trapped by the CDS. These items would otherwise eventually end up in Russell Lake.|
|The stormwater outfall is virtually garbage-free!|
The impetus for filtering stormwater came from the Russell Lake community group who were concerned about how the Portland Hills Estates development would impact lake water quality. This concern lead to the developer, Clayton Development, including the purchase and installation of these systems into the development agreement. Using these CDS systems is now common practice for Clayton Development.