In Stream Work using a Turbidity Curtain within North Saskatchewan River Stormwater Outfall Rehabilitation

OUTFALL 56 PROJECT

Location: North bank of the North Saskatchewan River within Dawson Park in Edmonton, Alberta

Client: City of Edmonton

Objective:  To confine sediment laden water, resulting from the implementation of a vegetated riprap application surrounding a storm water outfall on the bank of the North Saskatchewan River.

In the fall of 2007, Terra Erosion Control, working in conjunction with Kitchton Contracting 1963 Ltd of Edmonton, implemented a vegetated riprap application at Outfall 56 on the north bank of the North Saskatchewan River.  The project was administered by Jason McDiarmid RET of Stantec Consulting on behalf of the City of Edmonton. 

The design included a toe apron, as part of the riprap structure, to be placed into the river at the toe of the slope; therefore increasing the turbidity levels along the edge of the river.  In order to comply with the Department of Fisheries and Ocean’s (DFO) regulations prohibiting activities resulting in sediment laden water entering fish habitat the following measures were implemented; The work area within the river directly in front of the project site was partitioned off from the rest of the river using a turbidity curtain in order to contain the silt and sediment stirred by in water.

A rock vane was installed approximately five meters into the river using a walking excavator (spyder hoe) at the upstream end of the project area.  The purpose of the rock vane was to reduce the impact of river currents on the curtain.  A steel post was placed at the end of the rock vane to provide an anchor point for the curtain in conjunction with an existing concrete block on the shore.    

The curtain sections were assembled on the staging area adjacent to the project site.   The curtain was then manually launched into the river, upstream of the temporary rock vane, and positioned with anchors using a jet boat.  The other end of the curtain was then tied, at the downstream end, to the bank.  Weights along the bottom of the curtain kept it suspended in the river leaving a gap underneath to allow for fish passage.

The turbidity curtain was proven to be very effective at containing sediment laden water in front of the project site.  The curtain was removed after completion of the work using a spyder hoe, in conjunction with an excavator, to hoist it back up the bank.