Photo courtesy of the Nevada State Public Works Division

A view of Marlette Dam and Reservoir, facing northwest, on June 22. 2021.

U.S. Sens. Catherine Cortez Masto and Jacky Rosen of Nevada announced on Oct. 22 that the Federal Emergency Management Agency was making a $10 million grant "to enhance the safety and functionality of the Marlette Lake Dam, reducing the risk of a dam breach during an earthquake," according to a news release, the Nevada Appeal reported.

Grant sub-applicant the Nevada State Public Works Division has spent the last year fortifying the earthen dam, which dates to the 1800s. The mountain lake supplements Carson City's drinking water.

The State Public Works Division (SPWD) said total construction costs will be about $20 million. The state of Nevada has allocated $13.4 million for project planning and construction of the project.

Photo courtesy of the Nevada State Public Works Division

"SPWD is proposing to stabilize Marlette Lake Dam to reduce hazards from seismic events by enlarging the downstream embankment with fill, replacing the existing corroded and leaking outlet works and raising the crest of the dam to address freeboard deficiencies," according to a 2024 FEMA environmental assessment. "SPWD is also proposing to replace the aging spillway, which is currently undersized and open to snow and debris that could restrict emergency flows, with a covered concrete box culvert."

The assessment said, "The Marlette Lake Dam is in an area of high seismic hazard. Annual inspections indicate a high probability of a dam breach should there be an earthquake of magnitude 6.5 or larger because of the age and condition of the dam."

The assessment said a dam breach would not only impact the safety of nearby residents but could impact "the ecology and water quality of Lake Tahoe and the delivery of water to Carson City and areas of Storey County and Lyon County."

"SPWD assumes that the lake drawdown process would begin in October 2024 and end in March 2025, at the latest," the assessment reads. "Major project construction would extend from May 2025 through October 2025, after which the cofferdam would be removed to allow the lake to begin to refill, and the site would be stabilized and remain inactive during the following winter.

"In May 2026, final construction of the mechanical control building and minor appurtenances, in addition to capping, would be completed and the site would be restored by summer 2026. The lake is expected to take approximately six years to naturally refill, depending on annual precipitation."

Carson City is prepared for the anticipated impacts, with a local water treatment plant having its capacity raised.

Marlette Lake was created in 1873 when the dam was first built. The dam was raised to its present height of 45 ft. in 1959.

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