Beaver Lake Dam – Admiralty Island AK

Description

The Civilian Conservation Corps built the Beaver Lake dam in 1936. The dam is part of the Admiralty Island Canoe Route. It was designed to raise the level of Beaver Lake and create a navigable channel that could be traveled by canoe between Beaver Lake and Lake Alexander.

A registration form of the National Register of Historic Places reports on the condition of the dam as of 1992: “The Beaver Lake Dam was built on the outlet stream of Beaver Lake, 75 feet down stream from the lake outlet. Its purpose was to improve the navigability of the canoe route by raising the level of Beaver Lake about three feet, thereby deepening the channel between Alexander Lake and Beaver Lake. Now, without maintenance, the dam still holds some water and effectively raises the level of Beaver Lake by one to two feet.

The dam was simply constructed using a twelve inch diameter log about 45 feet long as the main structural member or stringer. This log was wedged cross-wise in the stream at a narrow bedrock constriction, where the stream would other wise be less than one foot deep. Split planks about six feet long were nailed (using galvanized nails) to the top of the log at a 45 degree angle so that the tops of the split planks pointed downstream. Large rocks were placed in the water at the base of the split planks on the upstream side to hold the planks down against the force of the water. Rocks were also used to chink under the stringer and under the split planks, to further support the dam against water pressure.

While some of the chinking rocks have been displaced and the stringer has sagged, thereby lowering its effective height, the dam still raises the level of Beaver Lake. In some seasons the water level of Beaver Lake completely obscures the dam at its current effective height.”