Four steps to cost-effective dam replacement

The existing dam’s concrete spillway was demolished and reconstructed one half at a time. Peterson Contractors Inc. built a causeway and cofferdam using sand from a nearby migrating sandbar. This eliminated the need to haul in hundreds of loads of material and made it possible to construct much of the cofferdam with just two equipment operators.

Air bladders consist of reinforced, layered rubber, approximately ¾ inch thick. Each bladder has special fittings that connect to embedded air piping via flexible connections.

Since much of the spillway concrete was removed, the dam required measures to maintain its stability (resistance to movement due to water pressure). The solution consisted of rock anchors drilled through the dam and into the underlying bedrock. The weathered and fractured bedrock below the dam was improved via a foundation grouting program.

Steel panels provide the strength necessary to hold back water and protect the rubber bladders from potentially damaging ice, debris, and sunlight. Steel anchor bolts, embedded into the underlying concrete, secure the panels, hinge, and bladders to the dam.

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