More than four-and-a-half months after a March 22 megastorm unleashed heavy rains on Moccasin and Groveland, creating runoff and erosion that damaged millions of dollars worth of public infrastructure and utility-owned water works, Hetch Hetchy Water & Power contractors are still fixing $21 million in storm damage at Moccasin Dam and Reservoir.

Officials at the state fish hatchery just below Moccasin Dam and Moccasin Reservoir hope Hetch Hetchy, the utility giant based in San Francisco, will have the work done no later than March 1 so that they can begin raising more trout at Moccasin Creek Hatchery.

That March 22 storm tore up parts of Groveland, Priest Reservoir, the Hetch Hetchy company town of Moccasin, the dam, its spillway, the reservoir, the state fish hatchery and multiple roads, including highways 49 and 132.

Two people were killed during the height of the storm-generated runoff farther south in Mariposa County.

On Wednesday, Hetch Hetchy officials said they are working closely with the state Division of Dams Safety to ensure all repairs and improvements to Moccasin Dam and Reservoir meet or exceed standards. They hope to have Moccasin Dam and Reservoir back in operation by the end of this year.

Future may include bigger, more damaging storms

Five inches of rain fell in 24 hours at Priest Reservoir just up the hill from Moccasin, said Steve Ritchie, assistant general manager of water enterprise for the San Francisco Public Utilities Commission, which owns and operates Hetch Hetchy Water & Power.

Ritchie said the rain measured at Priest that day included 3 inches in a 4-hour period.

“This is the biggest storm we’ve ever seen there,” he said. “The dam and system were pushed to their limits, with the spillway being torn up, and the dam nearly getting overtopped, and it was seeping. So they were pushed right to their limits. But they survived. With climate change things will undoubtedly get worse.”

In addition, the Tuolumne River and Moccasin Creek watersheds experienced the seventh-wettest March on record, Ritchie said, so the ground was saturated before the March 22 rains came.

Crews at Moccasin are now working to fix and improve a cutoff wall inside Moccasin Dam, a diversion dam, an auxiliary spillway, where wire-mesh, rock-filled mattresses got tossed around during the storm, and a slide gate that allows water to be released rapidly from the dam.

Some of the $21 million has already been spent on immediate cleanup and response to storm back in March, on pressing matters including debris removal, erosion repairs, previous work on the diversion dam, and at Priest Reservoir where the hardest rains fell, Ritchie said.

“That doesn’t take into account what new work we have to do to be prepared for a future that may include bigger and worse floods, and improvements downstream for potentially bigger flows,” Ritchie said. “That will cost more in future.”

Moccasin Reservoir was built in 1929 and can hold just over 550 acre-feet, puny compared to Don Pedro just downstream, which holds 2,030,000 acre-feet when it’s full. A primary function of Priest and Moccasin reservoirs is hydroelectric power generation, Ritchie said. Moccasin Reservoir has been kept empty since the March 22 storm. Priest Reservoir can hold up to 1,950 acre-feet and it stands at about 2,220 feet elevation, above Moccasin at 915 feet above sea level.

Cutoff wall

The cutoff wall inside Moccasin Dam used to be 3 feet below the top of the dam, which is about 62 feet tall. Rains and runoff on March 22 raised the level of Moccasin Reservoir above the height of the old cutoff wall inside the dam, and that is one reason the dam began seeping, prompting public safety warnings from the Tuolumne County Sheriff’s Office and other local public safety people.

Workers at Moccasin are going to raise the height of the cutoff wall to within six inches of the top of the dam, Ritchie said.

Back in March, Hetch Hetchy workers at Moccasin had coincidentally shut down water deliveries to the Bay Area about 12 hours before the storm hit, for maintenance on the San Joaquin pipeline near Tesla.

“Some days it’s better to be lucky than to be good,” Ritchie said.

That shut off was just above the powerhouse at Moccasin and it was extended when the storm hit so that crews could clean up the mud flood that backed up into the tailrace of the powerhouse, where water comes out of the structure, Ritchie said. Water deliveries to the Bay Area resumed seven days after the March 22 storm.

The Hetch Hetchy Regional Water System serves about 2.7 million residential, commercial and industrial customers in the Bay Area, including all of San Francisco and San Mateo counties and portions of Alameda and Santa Clara counties.

Hatchery concerns

Downstream from Moccasin Dam on March 22, the state fish hatchery got slammed and more than a million fish were killed.

“Primarily there was damage to the fish hatchery,” Ritchie said. “We had some damage to Hetch Hetchy buildings, mud in the lowest parts of Moccasin.”

The state fish hatchery is on Hetch Hetchy property leased by the state, and the state owns all the buildings and equipment at the hatchery.

“We’re working closely with the hatchery,” Ritchie said. “We’ve helped them out. They are hoping to get the fishery back in operation by the first of March.”

A shutdown of Hetch Hetchy’s Mountain Tunnel is still scheduled January and February for interim repairs, Ritchie said. That schedule should allow more work time on Moccasin Dam and Reservoir to ensure the hatchery can get water no later than March 1.

The hatchery manager at Moccasin Creek is Justin Kroeze.

“Yes, we are waiting,” Kroeze said Wednesday. “We need water to get fish back in here. We need water in that reservoir to run water through here for our hatchery. It sounds like we’ll get water here by March.”

Still planting fish

Moccasin Creek Hatchery is owned and operated by the California Department of Fish and Wildlife, and when it’s up and running it produces millions of trout: rainbow, brook, golden and brown, though 95 percent are rainbow trout, Kroeze said.

March 22 storm damage at the hatchery, which lies downstream and below Moccasin Dam, totaled about $3.2 million, Peter Tira with state Fish and Wildlife said in updates earlier this year. That total is still accurate this week, Kroeze said.

“We just started epoxy coating our fish ponds, the concrete raceways that we raise the fish in outside,” Kroeze said. The raceways run parallel to Moccasin Creek. There are eight of them and they’re each 600 feet long.

“That equals about 95,000 square coat of concrete we’re applying epoxy coat to,” Kroeze said. “That will extend the life of the concrete and create a cleaner environment for the fish, which will increase our efficiencies of fish production.”

Moccasin Creek Hatchery is a key facility for the state Department of Fish and Wildlife. Before the storm hit, the state relied on Moccasin Creek Hatchery to supply trout to multiple Central Valley and western Sierra Nevada reservoirs and other bodies of water.

Kroeze said he and his crew at the hatchery have continued planting fish in multiple waterways all over Tuolumne County since the March 22 storm, thanks to help from other state hatcheries.

“Our focus is Tuolumne County,” Kroeze said. “That’s where our fished waters are. We are still planting fish.”

Truck drivers go from Moccasin to the Fresno hatchery multiple times a month and bring back large trucks full of water and fish, Kroeze said. The fish are transferred to smaller trucks and then planted at Pinecrest; Middle Fork Stanislaus from Dardanelle up to Kennedy Meadows; Stanislaus River Clarks Fork; Stanislaus River South Fork, from Frazier Flat Campground up through Strawberry; the Lyons Canal ditch at South Fork Road; and the Middle and South forks of the Tuolumne River.

Kroeze said last week the plants amounted to 6,000 pounds of fish every other week, which works out to about 12,000 half-pound rainbow trout. His crew staggers fish plants so that each location gets fresh, live trout every other week.

“Currently there are other hatcheries in the state raising fish for us right now,” Kroeze said. “When we get water here, we’ll transfer those partially-grown fish to the hatchery so we don’t have to start from eggs. We won’t have to start from scratch. We’re hoping that will be March 1, at the latest.”

Groveland still hurting too

Farther up the hill, Pete Kampa, general manager for Groveland Community Services District, said Wednesday the storm damage total for Groveland CSD from March 22 was about $1.3 million, and they have $400,000 in work still to do from the previous year’s storms. The utility agency hopes to get everything fixed and competed in the current 2018-19 fiscal year.

Short-term, Kampa and Groveland Rotarians and others in Groveland are trying to repair storm damage in the park near downtown so they can host the annual 49er Festival on Sept. 15.

Groveland CSD has received about $6,000 in cash donations, courtesy of Groveland Rotary efforts, to make repairs at Mary Laveroni Community Park, which sustained about $125,000 in storm damage March 22. A volunteer contractor has completed new sheetrock in the storm-damaged concession stand.

“We have completed mold remediation and sheetrock at the concession stand and Moyle Excavation will be starting the dirt work in the park tomorrow, with an estimated two-week construction period to completion before the 49er Festival,” Kampa said. “We have PH Electric preparing to replace the vendor electrical stations, outlets, and breakers damaged by flood waters.”

Current updates on March 22 storm damage totals from Tuolumne County and Caltrans were not available. That same violent weather event, its runoff and erosion turned creeks to rivers, tore out sections of Highways 49 and 132 near Coulterville, and resulted in the deaths of two people.

Contact Guy McCarthy at gmccarthy@uniondemocrat.com or 588-4585. Follow him on Twitter at @GuyMcCarthy.

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