The salmon are back but recent damage to the Capitol Lake dam fish ladder is making their passage from Puget Sound to the hatchery in Tumwater more difficult.

A contractor hired by the Department of Enterprise Services will begin repairs on Thursday Sept. 12. It is unknown how long the work will take until the contractor – Rognlin's Inc. of Aberdeen – has a chance to inspect the ladder at low tide early tomorrow morning.

The repair work will require the closure of the sidewalk on the south side of Fifth Avenue and the temporary closure of one eastbound lane next to the dam. Enterprise Services will lower the lake by about two feet during the inspection and repairs.

The state has asked the company to expedite the repairs. Enterprise Services is coordinating the repairs with the Department of Fish and Wildlife.

While the exact cause of the damage, which was discovered on Sept. 5, is unclear, it was likely the result of logs and other debris passing through the ladder following recent storms.

The damage prevents salmon from entering the lake except at certain high tides. Some fish may also be able to pass through the dam gates when the water level of Budd Inlet and the lake are the same.

The fish ladder is the pathway used by hatchery chinook, wild coho and other sea-going fish to navigate past the dam when leaving and returning to the lake each year.

The fish ladder, which was constructed in the 1990s, consists of 11 pools or cells ascending from Budd Inlet to the lake. The water level in each cell is about one foot higher than the one below. Each cell is about 20 feet deep.

Four of the 11 cells are damaged, all beneath the Fifth Avenue bridge and nearly impossible to see from above. The failed cells create a height too high for the salmon to get over, according to the state Fish and Wildlife hatchery manager.

The cells are formed by walls made of thick boards stacked one on top of the other laying perpendicular to the concrete walls. Unlike the dam itself, water is always flowing through the fish ladder.

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