Pine Lake Park Slope Restoration Project

The Sunset Supply Pipeline is one of several major water transmission lines that bring water to San Francisco's drinking water reservoirs. This pipeline is 60" in diameter and was placed into service shortly after World War II.  The air valve that failed was 8" in diameter, and the transmission line itself was not breached. 

Map showing approximate area along the Sunset Supply transmission line where air valve is located (in red)

Background:

In March 2024, an 8-inch air valve connected to a 60-inch water transmission line failed, just below the end of the 1700 block of Wawona Street, above the Pine Lake Park dog park.  

That transmission line feeds water from our treatment plant on the San Francisco Peninsula to the Sunset Reservoir, which is one of the largest serving the residents of the city.

Water streaming from the air valve caused a geyser above the area which then flowed down a steep slope into the park, scouring a path to the park below until the crews onsite were able to shut the leak down.

Within a week, SFPUC identified a construction contractor and an engineering consultant who were able to work with the agency to determine a scope and schedule for repairs, including the hillside and the dog park area.

Map is approximate and not to scale.  Blue area is the location of the impacted slope. Yellow area is the debris field.

The first phase of work to prepare for restoration of the area was to remove hazardous trees.  That included all trees that became dangerously undermined by the scouring action of the water.  This work began on March 11th, 2024 and was completed on March 21st, 2024.

The second phase of work involved covering the affected area of the slop with plastic sheeting to prevent further erosion. That work was completed on March 22nd, 2024.

During late 2024 and early 2025, the slope was first stabilized and then reconstructed. When finished, our contractor moved to the meadow to remove the debris field, repair irrigation lines and re-sod the meadow.