Boundary Dam Water Supply

(Pend Oreille County, WA)  Landau Associates assisted Seattle City Light with completion of a pilot study to evaluate whether groundwater resources around its Boundary Dam facility were present in sufficient quantities to support development of water supply wells to provide domestic and industrial water to the facility. The facility is located approximately 10 miles north of Metaline, Washington in an area where outcrops of limestone, dolomite, and shale extend several thousand feet deep. The Dam had historically used water from a seepage spring located in a hillside near its maintenance and service center. 

Landau Associates completed a pilot study that identified three different areas capable of providing domestic and industrial water to the Dam’s maintenance shop and powerhouse, as well as a nearby campground, and a scenic overlook. Following an assessment of local hydrogeology, eight pilot wells ranging from 250 to 800 ft deep were drilled around the facility. Aquifer pumping tests, including step-discharge, constant-discharge, and recovery tests were conducted at five of the wells to assess their long-term production capabilities and to provide information for future design considerations. 

Based on the results of the pilot study, Seattle City Light selected Landau Associates to oversee installation and development of a production well in an area with the potential to provide the greatest long-term yield base. Additional pumping tests conducted at the well indicated it was capable of providing a long-term uninterruptable source of water sufficient to meet the needs of the facility. 

Photo 3: Seattle City Light