New cracking at Twain Harte Lake dam worrisome

By Chris Caskey, The Union Democrat August 05, 2014 03:30 pm

Twain Harte Lake was drained over the weekend so cracks in the lake’s dam could be evaluated. Maggie Beck / Union Democrat, Copyright 2014.
Experts with the state of California continue to evaluate damage at the Twain Harte Lake dam, even as problematic movement in the granite that caused a leak on Sunday continued Monday.

Local and state crews worked on the granite formation known as The Rock throughout the day over what is now a drained Twain Harte Lake. The state dam safety team pressed forward on an assessment that engineers said could take days, weeks or longer depending on what they find.

Local sewer provider Twain Harte Community Services District also started bypassing a main sewer line near the dam serving the Twain Harte community.

As work continued, the cracking activity in the granite dome anchoring the dam continued in the morning with another loud popping noise and noticeable movement. Tom Trott, THCSD’s general manager, said district staff were on The Rock at the time.

Though not as significant as the explosion-like phenomenon that closed the dam on Sunday morning, the continued movement is concerning, especially as a special team from the state is evaluating what is causing the cracks and how they can be fixed — if at all.

“It does look like some cracks got bigger, and it does look like there are some new cracks,” Trott said.

Once the state’s assessment is complete, repairs to the concrete and metal dam adjacent the granite slab could take months, according to the California Department of Water Resources.

“It’s not going to happen overnight,” said Andrew Mangney, an engineer with DWR’s Division of Safety of Dams Central Region.

 

For the complete story, see the Aug. 5, 2014, edition of The Union Democrat.