WENATCHEE, Wash. -

A crack in the Wanapum Dam on the Columbia River and the ensuing reduction of water levels have prompted crews to carry out about $7 million worth of work on fish ladders for chinook salmon.

The Wenatchee World reports that existing fish ladders at the Rock Island and Wanapum dams are being extended to allow the chinook to reach their spawning grounds.

Divers discovered a 65-foot crack across part of Wanapum Dam's concrete spillway in February, and workers have lowered the water level 26 feet to reduce pressure on the dam. That left the upstream exits of the fish ladders there high and dry -- unusable for the migrating fish.

At the Rock Island Dam 36 miles upriver, the ladders are usable for now, but crews are worried they won't be as levels drop farther this summer.

The Chelan Public Utility District will pay about $4.3 million to extend the ladders on the Rock Island Dam's Chelan and Douglas County shorelines. The Grant Public Utility District's cost to modify its ladders on the Wanapum Dam is estimated at $3 million. The work is expected to be completed by Tuesday.