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Creating a Freshwater Fish Reef !

Submerging over 300 Root Balls in Spray Lakes

 

    In 1998, BVHD was contracted by TransAlta Corporation to finish a fish reef project that was started but not finished by another organization. The project involved submerging over 300 tree stumps that had been collected in piles, at a number of locations around the west side of the reservoir. Some anchors had been built by the group that first attempted to complete the job, but not nearly enough for the task at hand!

    The first attempt involved the use of a helicopter, but it was determined that the project could be completed in a more cost effective manner with a specially designed raft. The raft would incorporate two collapsible rubber truck tubes on the back end, so that the back side of the raft would sink when required. This would be achieved by using an air manifold control operated from a tow boat.

    Three sites were chosen for the submergence program, so that a number of reefs could be submerged in a cluster series. This would result in the creation of good fish habitat for lake trout on three different areas of the reservoir. The reefs would be positioned in a depth of 60 feet under maximum storage levels in the lake, so that during low seasonal levels, the reefs would still be 40 feet below the surface of the lake.

Getting the Job Done!

 

    A custom raft was constructed that could be towed to shoreline and loaded with anchors. Then the root balls could be cabled to the anchors and towed out to the submergence site, which was marked with a buoy at the appropriate depth. Fresh woody debris was threaded into the specially formed anchors to add extra stability for submergence and also provide added bio-mass and cover habitat (See photo below).

    Anchors that had been built by the previous group were used in addition to the custom built new anchors. A formula was created to determine the anchor weight required to submerge a given mass of wood in the root balls. Holes were drilled thru the base of the root balls and 1/4 inch galvanized steel cable was threaded thru the stumps and attached to the anchors.

    An air line and tow rope connected the raft to the tow boat. A control valve was operated from the boat, to remove and inflate air in the truck tire tubes on the underside of the raft. When the back side of the raft was submerged far enough under the surface of the lake, the anchors and load slid off into the depths.

Above: Duncan McColl readies the anchors on the raft, after they have been loaded with a wheeler truck.

Above: A load is submerged next to the marker buoy in 60 feet of water.

Above: Duncan McColl loads the raft with the anchors using a plywood ramp.

Spray lakes Fish Reef Project

Each concrete anchor weighed just over 200.lbs and had holes thru the side to add extra woody debris!

 

Some Anchors had 4 holes and others had 6 holes so that more woody debris could be added!

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