Reclamation to Conduct Geotechnical Study at Lake Tahoe Dam

Tahoe City, Calif. - The Bureau of Reclamation will begin a geotechnical research study this month at Lake Tahoe Dam as part of the Lake Tahoe Dam Rehabilitation Study. While the dam is currently safe to operate, the study is being conducted to evaluate alternatives for needed repairs.

Restoration repairs are needed to address deterioration in the 115-year-old dam structure, which was constructed prior to the introduction of air-entraining admixtures in concrete. The admixtures allow needed space for expansion and contraction of water molecules as the concrete goes through natural freeze-thaw cycles. As temperatures at the dam routinely drop below freezing at night and climb above freezing during the day, the dam experiences freeze-thaw cycles regularly, which are known to cause deterioration of the concrete. Additionally, analysis of the concrete in 2005 indicated signs of deterioration from alkali-aggregate reactions. Gate operations have also been affected as gates have become temporarily immobile or unable to close due to the concrete deterioration.

The geotechnical investigation is planned for mid to late April and will take about one week to complete. The geotechnical borings will be completed from a barge, impacting the Lake Forest Boat Ramp for one day before and after the drilling. The geotechnical research study will inform design considerations.

Lake Tahoe Dam accounts for approximately 72% of the storage in the Truckee River Basin. Flows are determined by a Federal Water Master as required by the Truckee River Operating Agreement. Visit https://www.usbr.gov/mp/lbao/programs/lake-tahoe-dam.html to learn more about Lake Tahoe Dam.