That was one big sloppy wet tropical kiss of a storm last week, and it fell hard on the Mother Lode.
Hundreds of local and state agency workers and contractors were out Tuesday in the mud and muck in Tuolumne and Mariposa counties, trying to assess how much damage was done and what can be done short-term to ease the wet, heavy punches landed by that three-day storm.
The biggest blow came Thursday last week.
Rainfall in Groveland and below at Priest Reservoir exceeded 4.8 inches on Thursday, according to Western Regional Climate Center data. Hetch Hetchy workers at Priest Reservoir measured 3.1 inches in a 4-hour period from 11 a.m. to 3 p.m. that day, March 22.
That kind of rain intensity is what unleashed havoc and chaos in Groveland and Moccasin, and it transformed itty-bitty creeks to raging, killer-size river floods, inundating ranches, tearing out roads and contributing to the likely deaths of two people whose remains have yet to be recovered in Mariposa County.
Storm damage costs were still being tabulated Tuesday. Tracie Riggs with the Office of Emergency Services in Tuolumne County said initial estimates for damage to county roads and other infrastructure range from $3.5 million to $5 million. Riggs emphasized these are preliminary estimates. County road crews and engineers have yet to visit every location damaged in the three-day storm last week.
“Right now we know that Ferretti Road is approximately $800K,” Riggs said. “Priest Coulterville Road is in worse condition and has six different locations that failed.”
There are more damages on Merrell Road and Marshes Flat Road and many more, Riggs said. All storm damage assessments are preliminary and will take time to finalize.
Tuolumne County is also working with Groveland Community Services District, various school districts, Tuolumne Utilities District, as well as the City and County of San Francisco, which owns Hetch Hetchy Water and Power.
Riggs said the City and County of San Francisco “has provided a high level estimate of $40 million in damages.” Mary Ellen Carroll, the emergency planning and security director for the San Francisco Public Utilities Commission, confirmed that in a phone interview.
“It’s the preliminary estimate,” Carroll said Tuesday afternoon. “That could change.”
Up in Groveland, business people, residents, volunteers and road workers were still knee-deep and deeper in some places helping clean up from last week’s storm.
Below the Miner’s Mart in Big Oak Flat, one Caltrans worker stood in a debris-choked draw he said he believed was Jackass Creek, helping spot another Caltrans worker in a Caterpillar track loader struggling to move mounds of tree roots mixed with mud.
They were just upstream from a line of 10 closely spaced, orange-and-white signs warning motorists of where the creek took a bite out of the shoulder of Highway 120.
“Sorry … We’re closed to due to flooding/clean up,” said a sign with two hand-drawn smiley faces out front of Mountain Sage Cafe and Nursery. “Thanks for understanding! Coffee Bar open Wednesday 3/28 @7am.”
Patti Beaulieu, store manager at Helping Hands and Furniture Barn, helped supervise a crew of volunteers cleaning up Furniture Barn, which was filled with muddy water more than 3 feet deep last week.
The volunteers included eight inmates from Tuolumne County Jail in Sonora. They started at 8 a.m. Tuesday and they plan to be there in Groveland for the next couple days, Deputy J. Richards with the Tuolumne County Sheriff’s Office said.
“We really appreciate the help,” Beaulieu said. “I don’t know how we would get through this otherwise. We had 20 volunteers yesterday.”
Beaulieu said she lost two 30-yard dumpsters full of donated chairs and couches, which ended floating and stacked up haphazard in two of the five rooms at Furniture Barn that got flooded.
The height of the storm last week was still a hot topic Tuesday.
Steve Ritchie, assistant general manager for water enterprise with San Francisco Public Utilities Commission, gave a presentation on the Moccasin dam and reservoir incident to the commission in San Francisco.
Hetch Hetchy water deliveries were already stopped for maintenance on March 22 when the major rain event occurred.
Nearly 5 inches of rain was measured for the day at Priest Reservoir with 3.1 inches in the 4-hour period between 11 a.m. and 3 p.m., Ritchie said. Moccasin Creek overflowed into Moccasin Reservoir. Both spillways at Moccasin Dam and the Foothill Tunnel, which runs under Don Pedro Reservoir, were used to dump water.
Moccasin Dam was inspected and significant seepage was noted, Ritchie said. He showed photos of water seeping out of the front of Moccasin Dam and said, “Seepage, that is extraordinary leakage. When you see that change in the water and there’s muddy flow, that is when you have great concerns about a dam.”
An emergency action plan was activated and evacuation orders were given for people living in residences downstream and for some Moccasin cottages, Ritchie said. Notifications were made to the state Division of Dams Safety and to Tuolumne County. Division of Dams Safety personnel arrived at Moccasin late in the afternoon.
Priest Reservoir was affected by the storm’s intensity as well, Ritchie said.
Follow up actions for Hetch Hetchy staff will include Moccasin Dam inspection with a consultant team, cleaning up Moccasin Reservoir and connected facilities, helping clean up and restore the state’s Moccasin Creek Hatchery, operated by the California Department of Fish and Wildlife, repairing potable water lines, inspecting tunnels and pipelines that may have been damaged and repair as needed, restoring Hetch Hetchy water deliveries by April 5, performing further investigations of Moccasin Dam and its spillways, and developing plans for repair of the dam and spillways.
Of the Moccasin Creek Hatchery, Ritchie said 90 percent of the fish there were killed in the storm event.
Rick Estrada with Caltrans District 10 walked a part of Highway 49 that remained closed Tuesday in Moccasin. Part of Highway 49 was undercut by high waters at Moccasin Diversion Dam.
“All the water was backing and it started creeping around the edge of the berm and eating away at the roadbed,” Estrada said Tuesday. “It goes under the roadbed 12 feet to 15 feet cut back. It’s 8 to 10 vertical feet under the road. There’s nothing holding it up. You can see the asphalt is already starting to fold down.”
Farther south on Highway 49, up in the switchbacks between Moccasin and Coulterville, Caltrans crews have spotlighted at least nine locations where it's clear the road will need to be repaired, Estrada said. Multiple crews were out inspecting culverts and roadbeds Tuesday.
About Moccasin Dam, Ritchie told the San Francisco Public Utilities Commission, “We inspect our dams routinely. The last five years of inspection records show the dam is in good shape. In this case this was an extreme hydrological event. Division of Dams Safety staff concurred that we were doing the right things. It was just a massive amount of water in a very short amount of time.
“We’ll be looking at the dam,” Ritchie said. “It was built in 1925.”
Hetch Hetchy Water and Power dates to 1913, when Congress passed and President Woodrow Wilson signed the Raker Act, which permitted the flooding of Hetch Hetchy Valley on the Tuolumne River in Yosemite National Park.
The building of Hetch Hetchy’s complex series of reservoirs, powerhouses, tunnels, pipelines, and treatment systems remain one of the most significant undertakings in Tuolumne County history. The Hetch Hetchy Regional Water System today 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.
Contact Guy McCarthy at email@example.com or 588-4585. Follow him on Twitter at @GuyMcCarthy.