Hydropower has a reputation as the set-it-and-forget-it corner of the American grid. You pour the dam, you drop the water, and the powerhouse hums along for half a century while everyone argues about newer ways to make electricity. Then one pipe lets go, and you find out how much of that reliability was riding on a single run of steel.<\/p>\n
That’s roughly where Yuba County, California, finds itself. On September 1, Yuba Water Agency<\/a> awarded a $13.9 million contract to Hat Creek Construction & Materials for the hillside around its ruptured penstock, the mile-long, 14-foot-diameter pipe that fed New Colgate Powerhouse until one Friday afternoon in February. Crews are due to start this month and will keep working as long as the weather lets them.<\/p>\n The pipe itself is a separate job, and a much longer one.<\/p>\n Hat Creek’s contract covers stabilization material for the slope itself, a rock buttress along the penstock’s east flank and detention basins to catch runoff once the rain arrives. Senior engineer Matt Murray called the project “an important step in stabilizing the soil and slopes around our penstock” ahead of the rainy season. Which tells you the order of operations here. Before anyone rebuilds a mile of pipe on a California hillside, somebody has to make sure the hillside stays put.<\/p>\n On February 13, 2026, just before 3 p.m., the penstock ruptured near the top of its run above the powerhouse in Dobbins, about 45 minutes east of Marysville. A penstock, if you haven’t spent much time around hydro plants, is the downhill pipe. Water leaves New Bullards Bar Reservoir, travels almost five miles through a 26-foot-diameter tunnel bored through the mountain, then enters the penstock and drops about 800 feet over a single mile into the powerhouse. That drop is the whole point. The pressure it builds at the bottom is what spins the turbines.<\/p>\n When the pipe split, roughly 400 acre-feet of water sitting in the tunnel and penstock, about 130 million gallons, came down the hillside at once. The flow tore out sections of Lake Francis Road, damaged Pacific Gas & Electric transmission lines along with two shared switchyards, and swept mud and debris into the Yuba River above Englebright Dam. Ten people were working at the site that afternoon, according to officials. Five got out on foot, the rest were lifted out by helicopter, and one contract employee was hospitalized with serious injuries. That worker has since been released and is recovering at home.<\/p>\n The timing has its own wrinkle. The penstock had been shut down since October 1, 2025 for a major maintenance overhaul, and the South Yuba River Citizens League<\/a> reported that the failure came while a newly installed section was being tested during refill. Yuba Water says the cause remains under investigation by independent forensic engineers, that no conclusions have been reached about contributing factors, and that results are expected this fall.<\/p>\n New Colgate is the biggest thing Yuba Water owns. Federal licensing records list two vertical-shaft Pelton turbines with a combined 315 megawatts of installed capacity, while the agency’s own fact pages put peak output at up to 350 megawatts, enough for roughly 350,000 homes. Yuba Water describes them as the biggest single-cast Pelton wheels ever made.<\/p>\n A Pelton wheel is about the simplest idea in hydropower. Picture a ring of steel buckets with a high-pressure jet of water slamming into them, basically an overgrown water wheel. The catch is scale. Local reporting from before the incident put each wheel at 18 feet across, spinning at 180 rpm, and frankly, a casting that size is a manufacturing project in its own right. The Army Corps of Engineers is dealing with the same problem right now in Tennessee, where crews are swapping out a 22-foot turbine runner that had been spinning since 1957<\/a>.<\/p>\n Both wheels have been dry since February 13. Yuba Water sells this power wholesale into the California grid through CAISO, and the agency has warned that generation at the Colgate facilities could stay suspended for several years while recovery runs its course. It is covering the bill from financial reserves while the plant sits idle, and it has no residential ratepayers to pass costs to.<\/p>\n One small confession before we go on: Yuba Water’s older hydropower pages describe the penstock as 15 feet in diameter, while every incident document since February says 14. I’m going with the incident page, written by the people who have spent seven months staring at the actual pipe.<\/p>\n Because the site was buried, basically. The rupture left the deck above the powerhouse under a layer of sediment that topped 13 feet in spots, around 11,000 cubic yards of it, and pushed an estimated 60,000 cubic yards into the river channel below. Dam maintenance has a habit of turning up ugly surprises, like the Missouri River intake gates that recently came up 25,000 pounds heavier apiece thanks to zebra mussels<\/a>, but a powerhouse buried under its own hillside is a different order of cleanup.<\/p>\n Yuba Water has been working down that list all year. Crews cleared roughly 1,600 cubic yards of oily debris off Englebright Lake by early March, and the lake reopened to boaters in mid-March. Nordic Industries rebuilt the washed-out stretches of Lake Francis Road through July. Inside the powerhouse, teams have been cleaning and testing circuits for months, and the agency says many critical systems are already restored. The interior, luckily, was never fully inundated.<\/p>\nSo what let go in February?<\/h2>\n
Two giant Pelton wheels are sitting dry<\/h2>\n
So why has nobody touched the pipe yet?<\/h2>\n