Clover Bar Ravine

SITUATION

On the outskirts of Edmonton, Alberta, the Clover Bar ravine acts as a funnel for the runoff of several industrial companies including a paving company with large sand, gravel, and asphalt cold mix storage piles. There is also the highly turbid surface runoff from local roadways and parking lots during rain events. The problem is that in the ravine a fish-bearing stream receives the particulate laden water and flows directly to the North Saskatchewan River four kilometres away. Because the stream and river are fish-bearing, an environmentally friendly solution was needed, in accordance with the Department of Fisheries and Oceans as well as other environmental governing agencies.

The project was initiated by the City of Edmonton and in cooperation with Park Paving Ltd. was designed by Clearflow Consulting (now Clearflow Enviro Systems Group Inc.) as a pilot project to reduce NTU values and demonstrate the effectiveness of the polymer block products.

SOLUTION

An initial site inspection, including water and soil polymer optimizations was performed; this was used to determine the best polymer and installation procedure. In order to treat the turbidity a combination of site-specific polymer block blends were used to flocculate the particulate matter. These were placed in the streambed 5’ to 15’ apart utilizing the streams natural turbulence for optimum mixing.

Alternating between two different blends of polymer blocks provided the necessary polymer blend. To secure the blocks they were tied to sandbags using the integrated coconut rope; the sandbags also provided turbulence and a substrate for suspended particles to attach.

Downstream of the block, open-weave jute matting was laid down along the streambed and banks. This was the primary binding site for the suspended solids. Two men performed the installation in 8 hours using an ATV to access the area and carry materials in and out of the ravine.

RESULTS

NTU 79.0% reduction upon completion of the installation, turbidity downstream of the jute had visibly improved to the point that the bottom of the stream could be clearly seen. A week later a sample was collected showing a turbidity value of 4.2 NTU; well within acceptable discharge limits.