SOUTH LAKE TAHOE, Calif. — Rain on snow events bring unique challenges to wastewater operations at Lake Tahoe. As streets and meadows flood, stormwater seeps through manholes and into the sewer system. This inundates wastewater pump stations and the wastewater treatment plant, increasing the risk of sewer spills.

During this week’s atmospheric river, South Tahoe Public Utility District worked every day around the clock to address challenges and ensure reliable water and wastewater services.

On Friday night, an avalanche on the south end of Fallen Leaf Lake destroyed the district’s back-up generator building that supplies power to wastewater pump stations. 

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“Providing reliable wastewater services is all about redundancy, meaning we have a back-up plan for all our facilities,” said Manager of Field Operations Chris Stanley. “When an avalanche took out the powerlines and the back-up power supply, we had to get creative.” 

On Saturday morning, district staff assessed the damage and brought in a generator to power the pump station that services Stanford Camp. They continue to refuel the generator daily, while checking in and out with El Dorado County Sheriff’s Office for avalanche safety.

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Throughout town, flooded streets and meadows continue to impact sewer operations. Of particular concern, is a sewer pump station located on the meadow in the Al Tahoe neighborhood. On Saturday morning, the station was under multiple feet of water. Working with a local contractor, Haen Constructors, the district built a temporary containment structure around the station and installed pumps to divert stormwater. The district is also installing containment structures and sandbags around flooded manholes in the meadow to reduce inflow into the sewer system.

Collaboration is key during emergency situations. The California Tahoe Conservancy, Cal Fire, Lahontan Regional Water Quality Control Board, Tahoe Regional Planning Agency, Northwest Hydraulics, and the district are working together to identify options to help alleviate flooding impacts in this area.

South Lake Tahoe’s wastewater treatment plant is designed to treat up to 7.7 million gallons per day and averages 4.5 million gallons per day in March. At the height of this storm, up to 13.5 million gallons per day of wastewater were flowing into the plant. 

“The plant did exactly what it is designed to do to protect our environment during this massive storm,” said General Manager John Thiel. “We treated what we could and pumped the excess influent to our emergency retention basins, which can hold over 54 million gallons.” 

During this storm cycle, approximately 7 million gallons were stored in the emergency retention basin and will be drawn down once flows into the wastewater treatment plant subside.

South Lake Tahoe’s recycled water is exported to Alpine County where it is stored in a reservoir during the winter and released for agricultural irrigation in the summer. In recent weeks, heavy snow and ice buildup blocked irrigation canals causing localized flooding. The district is working with another contractor, White Rock Construction, to clear ditches of ice to alleviate flooding and prepare for releasing water from the reservoir this spring.

With another storm on the horizon, the district continues to stage back-up pumps and generators to ensure reliable service. 

Please help keep stormwater out of the sewer system by running sump pumps to storm drains and keeping manhole covers closed. 

For questions or concerns about South Lake’s wastewater system, visit stpud.us or call 530-544-6474.

Source: STPUD