Lake Sacajawea Flushing

Client—Longview, Washington

Following construction of the City’s new regional water treatment plant, an alternative means of providing “flushing water” to Lake Sacajawea needs to be implemented. Gibbs & Olson evaluated alternatives to provide flushing water which included: identifying water sources that could potentially be used to supply flushing water; developing design concepts and cost estimates for each alternative; identifying environmental and permitting issues associated with implementing the alternatives; and recommending one alternative with an implementation schedule. The recommended alternative includes modifying the existing intake on the Cowlitz River and providing new intake fish screens. Improvements also include installing four new submersible pumps capable of pumping up to 6,000 gpm and providing a SCADA control system to open and close slide gates at Lake Sacajawea. Extensive permitting was required prior to construction of the $1.7 million improvements.