Epic collaboration to prevent a sewer spill at South Lake Tahoe

SOUTH LAKE TAHOE, Calif. – This winter, Lake Tahoe has experienced the third-highest snowfall on record, with more on the way. Last week’s warm atmospheric river caused structural collapses, avalanches, and extensive flooding around South Lake Tahoe. Of particular concern is a flooded sewer pump station on the Upper Truckee Marsh. Epic collaboration resulted in a solution to address flooding and help prevent a sewer spill.

South Tahoe Public Utility District provides water and wastewater services for South Lake Tahoe. In anticipation of the storm, the District declared an emergency on March 7. As rain and slush continued to fall over the last week, water in the Upper Truckee Marsh rose several feet. A sewer pump station located on the edge of the marsh that usually pumps 150,000 gallons of wastewater per day, was pumping 1.5 million gallons per day by Saturday. The tenfold increase suggests the flooded station was pumping flood water out of the meadow and was on the verge of spilling.

The District worked with California Tahoe Conservancy and CalFire Incident Command to fly a drone over the marsh on Wednesday to help identify options for mitigating flood impacts. The water level in the marsh was 4.1 feet above lake level. During the 2017 winter storm, the marsh naturally breached the beach and flowed into Lake Tahoe. Following nature’s lead, the District, California Tahoe Conservancy, Lahontan Regional Water Quality Control Board, Tahoe Regional Planning Agency, CalFire, and Northwest Hydraulics determined that digging out this same channel would allow the marsh to flow into

On Wednesday evening, Haen Constructors mobilized a track-mounted excavator to access the beach bordering the marsh from the west end of Lakeview Ave. Rolling over more than 2 feet of snow along the beach, the excavator arrived at the location of the last marsh breach. A three-foot-deep channel was
dug into the sand and water from the marsh started flowing into the lake.
The District also built temporary containment structures around the flooded wastewater pump station and submerged manhole to reduce the amount of stormwater flowing into the sewer system. A bypass pump was installed to redirect some of the high flows to a different pump station. These approaches have been successful at preventing a sewer spill.

“Managing our complex wastewater operation requires an uncommon environmental sensitivity,” said John Thiel, general manager. “The support from partner agencies has been instrumental in identifying and implementing solutions to help our flooded facilities.”