The Kennewick City Council awarded a contract this week to clean up silt left in the area behind the Zintel Canyon Dam.
A gully that's 50 feet wide and 24-feet deep in places was created behind the dam when the city was testing for an underground water storage project in May.
The dam was built for flood control in the 1990s.
Apollo Inc., which already did some work on the steeper portions of the ravine that was damaged, will be paid $46,796 for the next phase. It had the lowest of five bids for the project, which the city had estimated would cost about $97,000. The money will come from the city's water and sewer fund.
Cleaning sediment from behind the dam should take a matter of weeks, said Kennewick Public Works Director Cary Roe.
The city started emergency repairs behind the dam May 27. It also hired an environmental specialist to look at eroded areas that had become nests for migrating swallows.
The city likely will not be able to repair the areas where the swallows are nesting until the birds leave in the fall, Roe said.
The city estimates that it discharged 35 million to 40 million gallons of water during the testing project. It is planning to store more than 100 million gallons of water in an aquifer for summer use.
Kennewick has been working on the project since 2008 with the state Department of Ecology, which will pay for more than half of it.
The council also agreed to rezone 20 acres south of the dam near Reed Street and 48th Avenue.
The change will require a larger minimum lot size. Mayor Steve Young said it was being made so that horses could be kept on the property, because some of the land in the area is too steep for houses to be built.