Bently revamps dam at Mud Lake

MINDEN - New technology is being applied at the Mud Lake dam to ensure a safer structure.

Nearly a century after its construction, work is under way on the reservoir at Mud Lake and its dam.

The dam dates to 1902 when pioneer William F. Dressler erected a small, clay-filled dam south of Gardnerville to irrigate his lands. By 1909, Dressler was expanding the dam to create a reservoir with 10 times the capacity - to take it from its then 500 acre feet to a total of 5,000 acre feet. His vision: to put a thousand acres under cultivation, creating a greener, more bountiful Carson Valley, and to provide livelihoods for many families.

Bently Agrowdynamics owns the reservoir and surrounding lands. The company currently irrigates more than 1,000 acres with water from the reservoir.

"It has served its purpose, but modern technology can give us a safer dam," Don Bently said.

Bently plans to reconstruct the dam, based on the company's long-standing concerns related to earthquakes and the valley's vulnerability. Bently watches seismic activity regularly from Woodfords, Calif., to the Mammoth, Calif., area.

As a result of those concerns, Bently said he has insisted all new Carson Valley construction for his electronics corporation, Bently Nevada, be designed in excess of local building codes. He's requiring designs that can withstand 8 on the Richter scale - that's four times as severe as the tragic quake that devastated Izmit, Turkey, in August and over twice as severe as the 7.6 quake that hit Taiwan recently (the Richter scale is logarithmic - an 8.0 event is 10 times as strong as a 7.0 event).

Plans for the new dam are no different. The dam's new design features a concrete base, replacing the existing dam's non-concrete design.

To better use the land's natural contours for containing the reservoir, Bently plans to move the dam slightly downstream of its present location which will shrink the dam's length of nearly 2,000 feet to just over 950 feet. The new dam will not change the reservoir water level, and the capacity will remain the same.

Bently owns 2,646 acre feet of the water rights permitted to be stored. The Carson Water Subconservancy District has an easement to store 526 acre feet, or 16.6 percent of the total permitted rights. Bently would like to see the subconservancy district participate in the costs associated with the dam's reconstruction.

"If we're sharing the benefits of the water, then I think it's appropriate we also share in the costs associated with storing the water safely," Bently said.

After a 6.0 magnitude event, known as the Double Springs Flat earthquake, struck less than five miles from the dam in September 1994, the state's Division of Water Resources required that the company owning the dam at the time, Aqueduct I, conduct a routine safety inspection. It hired SEA Incorporated, Consulting Engineers, to conduct an appropriate geotechnical evaluation. Although their findings did not require the dam be rebuilt or repaired, the state put it on its list of "high risk" dams.

For Bently, who purchased the dam in 1996, the decision to reconstruct it was clear.

"Might not be tomorrow, or next year, or next decade," said Bently. "Doesn't matter. Eventually a quake will hit and we wish to be prepared."

Bently's concern, however, doesn't stop with his own dam. A similar structure, not owned by Bently, exists several miles upstream of the Mud Lake location on Indian Creek. The Harvey Lake reservoir and its dam is taller at 75 feet, compared to the 45-foot Mud Lake dam. Bently hopes California authorities will take a look at that site, because he believes non-concrete dams are obsolete.

"If an earth-filled structure is considered high-risk at Mud Lake, then a similar structure just a few miles away at Harvey Lake is likewise high-risk," he said.

Bently said that should a failure of the Harvey Lake dam occur and spill water into the Mud Lake reservoir, it would be inundated.

"Excess water for upstream will simply be diverted back into Indian Creek and on down to the East Fork of the Carson River ... failure of another dam upstream isn't going to affect mine."