Rendering of Los Osos pipeline connecting to State water that comes in along Hwy 1
On September 4 the Los Osos CSD Board awarded a contract to Water Systems Consulting (WSC) for $854 thousand to design the proposed 2.5 mile pipeline intertie project connecting the community to State water at Hwy 1.
Currently the town is 100% dependent on groundwater.The bid from WSC is over $200,000 more than an engineer’s estimate used by the CSD in their planning. The consultant highlighted the complexity of the project.
At the July 10, 2025, board meeting, the board received a report which summarized the current condition of the Los Osos Groundwater Basin.The results of a new baseline scenario indicated that pumping at current average rates and spatial distribution would cause seawater to intrude further into the Basin which is an indication that current average pumping and distribution is “not sustainable.”
At the meeting, staff also provided a Water Resiliency Intertie Project conceptual strategy to enhance the long-term approach to improve the groundwater basin’s water quality and seawater intrusion issues and improve the resiliency of the community’s water supply.
A decision has now been made to move forward on a detailed design of the pipeline even though funding for construction is not yet in place. The theory is to make the project “shovel ready” by moving ahead on detailed design. helping to attract federal, state and local funding including from the purveyors.
Three year construction schedule
The company WSC’s design completion schedule is January 2027, considerably longer than two rival bids but “might be more realistic” says a CSD memo. Construction could be completed in Sept 2028 – three years from now.
“The proposed intertie pipeline alignment is nearly 16,000 linear feet (LF) from the Chorro Valley Pipeline north of Highway 1 to LOCSD’s 16th Street tanks. The alignment navigates a critical arterial road between the coastal communities, environmentally sensitive areas, two bridge crossings, and varied soil conditions. The project presents an opportunity for water supply sustainability and reliability while also presenting numerous challenges” writes WSC.
The pipeline is expected to bring 200 to 600 acre-ft a year into the basin. The urban areas of Los Osos use about 1,000 acre ft through the three water purveyors and the ag acreage east of town uses around 650 acre-ft from wells.
Ron Munds, CSD manager, says the additional supply would be sunk to help push back seawater and make the basin more sustainable.
Strong community support for the project is expected with new estimates that current pumping of groundwater is allowing seawater to intrude into the Los Osos water supply.