Skip to content

Los Osos Wastewater Collection System Project Areas B & C

Client: County of San Luis Obispo


Project Value: $31.7M

Project Description:  In 1983, the Los Osos groundwater basin, from which residential drinking water is pumped, was discovered to have high levels of nitrate, exceeding State standards. The high levels were partially due to the number of active sewage septic tanks in the area. This wastewater collection system project moved the community of Los Osos from a septic sewage collection and percolation system to a sewage collection system with tertiary treatment, improving water quality for Los Osos residents and Morro Bay proper. W.A. Rasic Construction installed 81,306 linear feet of gravity mains ranging in size from 9 to 18 inches in diameter, 17,515 linear feet of sewer force mains ranging in size from three to 16 inches in diameter, 283 concrete pre-cast manholes, 1,757 service laterals, and 27,019 linear feet of fiber optic conduit. The recycled water system included 27,264 linear feet of recycled effluent water force mains ranging in size from two to 12 inches, numerous wet wells, one pocket pump station, three duplex submersible pump stations, and one triplex submersible station. Further installations included an effluent disposal system that required preparing the effluent disposal site and installing 19,776 linear feet of subsurface horizontal perforated pipe, various arched infiltration chambers, and five monitoring wells. Project sequencing and traffic control measures focused on minimizing impacts on the local community were major project elements.