After years of delay dating back to 2016, Marin Municipal Water District’s board has finally greenlit a major fix to one of the county’s oldest water lifelines. This month the board approved a plan to replace two aging pipeline crossings over San Geronimo Creek, clearing the way to shore up the North Marin Line that carries raw water from Kent Lake and Nicasio Reservoir to the valley’s treatment plant.
Under the updated design, one creek crossing will be hoisted onto a new steel truss and roughly 1,700 feet of new pipe will be routed beneath Sir Francis Drake Boulevard. Crews will also cut out the old pipe and concrete pilings in the creek. District officials say they are aiming for late summer construction so any in-stream work avoids sensitive nesting seasons.
What the project will do
According to Marin Water, the North Marin Line went in back in 1957 and the existing creek crossings are now near the end of their useful life. The current spans sit on concrete trestles in the creek, have a history of leaks, and no longer match modern standards for reliability.
The revised plan calls for one of the crossings to be replaced with a 36-inch pipe mounted on a single-span steel truss supported by drilled piers. A second segment of the line will be installed under Sir Francis Drake Boulevard for about 1,700 feet. The new truss will elevate the pipe roughly 2 to 3 feet above the adjacent ground at the creek bank, which is intended to cut down on in-channel work and bump up seismic resilience, according to Marin Water.
Board sign-off and price tag
Earlier this month, the Marin Municipal Water District board voted to approve the revised plan and authorized staff to move ahead with final permitting and procurement. District staff estimate the construction will cost somewhere between $3 million and $5 million. Board President Matt Samson noted that the project has been on hold since 2016…