Two of the state’s four biggest sewage spills this winter came from an unlikely source – a tiny wastewater district near the rolling green hills and vineyards of Napa County.
The Lake Berryessa Resort Improvement District sent 6 million gallons of wastewater into streams, according to a state database. Only one utility district had a bigger spill than Berryessa, and that was the result of a PG&E power failure. The largest Berryessa spill was caused by a failure of its own system.
The wastewater went into tributaries of Lake Berryessa, which provides drinking water for Vallejo, Vacaville and other cities and flows into Putah Creek along the southern boundary of Yolo County. The lake is also a popular recreation spot whose surrounding area was designated in 2015 as the Berryessa Snow Mountain National Monument.
The district serves about 160 homes and businesses in the community of Berryessa Estates. It previously faced sanctions from federal and state regulators for illegally dumping millions of gallons of wastewater into creeks. District officials blame the spills on an aging treatment system, which they say is difficult to fix because the community’s moderate-income residents already pay high utility fees.
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Phillip Miller, Napa County’s deputy director of public works, said many sewer agencies have similar problems with old infrastructure. The county runs the district.
“All of these issues are coming to a head,” he said. “The district is a poster child for what’s happening across the state.”
Miller said the Berryessa spills did not put the public at risk because water agencies treat for pathogens. Utilities use chemicals, filters and other methods to make water safe for human consumption.
A bacteria in sewage, E. coli, can sicken and even kill people who swim in or drink contaminated water.
Alex Rabidoux, a supervising engineer at the Solano County Water Agency, which sells water from Berryessa to cities, said high lake levels this winter mean contamination of drinking water is extremely unlikely. However, in drier seasons, sewage spills from the district could harm the ecosystem in streams next to the district, he said.
Andrew Altevogt, assistant executive officer at the Central Valley Regional Water Control Board, said the recent Berryessa spills likely didn’t harm people because they were diluted by high creek levels during storms in January and February.
Still, the Berryessa district could face regulatory action. The board recently sent violation notices for winter sewage spills to 40 agencies and private entities, including the Berryessa district, the Sacramento Area Sewer District and the city of Placerville. The Sacramento Area Sewer District and Placerville acknowledged the violations when they reported the spills to the board earlier this year.
The notices ask the agencies to provide more information about the spills and their treatment systems. Board staff will use that information to determine how to proceed, Altevogt said, adding that the board generally prefers to work with agencies to address underlying problems rather than issue fines.
The board fined the Berryessa district $400,000 in 2005 for a series of violations, including a month-long spill of more than 4 million gallons of partially treated wastewater into Stone Corral Creek, records show.
In 2010, the board fined the district $375,000 for various violations, including spilling 3.8 million gallons of raw sewage and partially treated wastewater into streams. The board later agreed to waive the fine in exchange for promises to make system improvements.
The district was formed in the 1960s after the community was built, and the county took it over not long after. From 1965 to 1999, the district made no major capital upgrades, the county said a few years ago when it asked Berryessa Estates residents to approve a rate hike for improvements.
Residents passed the bond by a narrow margin, and they now pay $600 every two months for water and sewer service, effectively limiting the district from further rate increases, Miller said.
Located on Putah Creek just north of Lake Berryessa, the community is made up of a mix of working people and retirees with an average household income of $45,000, county officials said. Their homes are generally modest, and many appear to be manufactured units moved onto lots.
The district finished $3 million in improvements two years ago, adding capacity and new lines to the sewer system. The improvements were designed to handle the highest annual precipitation expected in a 100-year period, but did not contain this year’s flows, which were lower than the benchmark level, Miller said.
The district is trying to determine why the system faltered; officials suspect storm water seeped into storage ponds, limiting space for sewage. The district stores sewage in a series of ponds, putting it through a chlorine treatment process before eventually spraying it onto land.
Unlike some sewer districts, the Berryessa district cannot discharge treated wastewater into surface water. The Central Valley Regional Water Control Board prohibits such discharges on eight water bodies, including Lake Berryessa. Altevogt said that’s because the lake has a limited capacity to dilute sewage.
At the same time, the Berryessa district is limited in when it can spray wastewater on fields, such as when rain would make it run off into creeks. The requirements mean the district can run out of space in its storage ponds, as was the case during this winter’s storms.
As rain continued to pour, district officials said, they had no choice but to spray wastewater on land, and were unable to capture diluted wastewater runoff as required. That type of discharge accounted for the district’s largest spill, 4.5 million gallons in February, records show.
By comparison, when Folsom spilled an estimated 700,000 gallons of sewage into the American River in 2000, it prompted the Central Valley Regional Water Control Board’s biggest-ever fine, $700,000. The board also ordered widespread improvements in the city’s sewer system.
Line failures have also been a problem in Berryessa Estates. A spill of 1.5 million gallons in February was the result of a failed pipe weld, the district reported. Partially treated wastewater spilled for days before the break was discovered. A month earlier, slope erosion caused another pipe to disconnect from the main sewer tank, allowing 50,000 gallons of raw sewage to spill out.
A test showed E. coli levels next to Putah Creek at seven times the level of what is allowed in the district’s land application of sewage.
Miller said the district has received a $2 million state grant for some improvements, but must secure more grant funding to complete all the work needed to stop spills in the future.