Williams Brother Construction LLC, of Spokane, has won a $13.5 million contract for a major improvement project at the wastewater-treatment plant that serves the city of Clarkston, Wash.

The project, which was scheduled to start at the end of September, will include both installing some new equipment and rehabilitating some older machinery at the plant. The upgrades will enable the city to improve its processing of wastewater so that the treated effluent discharged into the Snake River is cleaner and meets state requirements, says Clarkston City Public Works Director Jim Martin.

The plant is located on 13th Street and Port Way, on the north side of Clarkston next to the river.

John Williams, president of Williams Brother Construction, says the project will include installing new pumps that circulate waste through the plant, blowers, screening equipment, and lift stations. It also will include constructing a new head works building at the front end of the wastewater treatment to screen and divert the effluent sludge, and installing grit removal structures and equipment.

The contractor also will build an additional aeration processing basin, which is a concrete structure with equipment for processing waste, among other upgrades.

Work is expected to be completed by early 2014. The Clarkston office of Meridan, Idaho-based Keller Associates Engineering Inc. designed the project.