Clover Bar Ravine Cleanup: Passive Floc Logs Cut Metals and Turbidity in Edmonton

The Clover Bar Ravine north of Edmonton, Alberta, drains an industrialized corridor straight into the North Saskatchewan Riverboth fish-bearing waters. City of Edmonton Risk Management sampling from 20042011 found metal concentrations exceeding CCME, Alberta Environment, and sewer-use guidelines, with an active upstream source of metals and sediment. Because the ravine supports fish and aquatic life, the city needed an eco-friendly treatment that could cut metals and turbidity without harming organisms.

The chosen approach was a passive system using site-specific APS Floc Logs. In June 2007, crews lined the streambed with open-weave jute, then placed 34 Floc Logs starting at the outfallalternating APS 703d#3 and 706b about 10 feet apart and tied to sand bags for hold and mixing turbulence. Natural fiber matting gave flocculated particles a place to attach and added erosion control. Anionic polyacrylamide Floc Logs bind suspended sediment, metals, and nutrients into settleable flocs while remaining nontoxic to aquatic life at the dosages used.

The train ran in summer 2007, 2008, and 2010 (skipped in 2009 for beaver flooding and in 2011 for embankment work). Sample pairs before and after Floc Logs showed clear drops in aluminum, copper, iron, lead, nickel, zinc, and TSSdownstream TSS as low as 4.2 mg/L in 2007, with visibility to the streambed. Metals concentrated in sediment near the first logs and tapered downstream. The passive system met regulatory turbidity and metal limits and proved an effective, low-maintenance cleanup for Clover Bar Ravine.