Trail Alerts

For updates on work at the Harry Tracy Water Treatment Plant, please visit

Friday, November 18, 2011

Underwater Construction Continues in the Peninsula Watershed

San Andreas Lake, the reservoir just west of the City of San Bruno, is the site of a large regional water improvement project, however construction work is taking place beneath the surface of the water. Demolition of a 1930’s-era water transmission tunnel is in progress 40 feet underwater!

Divers are razing this structure underwater, yet one would never know walking around the lake.  From the shore of San Andreas Lake, the only sound one can hear is the diver’s air compressor and support equipment. The tunnel will be replaced with a new underwater intake structure in 2012 that will send water from the reservoir to the Harry Tracy Water Treatment Plant for distribution to our taps.

In addition to the divers, hikers on San Andreas Trail may see boats and yellow booms in the water connected to this construction. The yellow booms are called silt curtains: underwater “curtains” that protect water quality and keep species out of the work zone.

PG&E is also doing major work this autumn near the San Andreas Trail – water testing the gas pipelines. The PG&E work is an unrelated project and is expected to wrap up by Thanksgiving in this location.

At the Lower Crystal Springs Reservoir work site, next to the southern trailhead to Sawyer Camp Trail, divers are working nearly 100 feet beneath the water’s surface. To work at that depth, seven divers are required for one day’s work.  Each diver may spend 45 minutes underwater before resurfacing. Currently, the team is installing supports for new valves.

Marine construction in both reservoirs continues through 2013 as part of the Crystal Springs/San Andreas Transmission System Upgrade project. Please call us 24 hours at (866) 973-1476 with any questions.

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