One of the city of Davis' busiest wells has been shut down after crews found extraordinarily high levels of manganese in the water.
City officials said it could be summer before the well is operating again at a cost of $2.6 million.
City engineers measured manganese levels in city Well 30 on Davis' west side at 1,700 parts per billion, far exceeding the maximum 50 parts per billion allowed in drinking water, city utilities officials said Monday. The manganese level soared again in follow-up tests to as high as 2,400 parts per billion, said the city's principal engineer on Tuesday.
"It's been creeping up in manganese," Dianna Jensen said of Well 30, but added that a 2,400 ppb reading was still "a bit of a surprise."
But the timing of the city's decision to shut down the well, days before Davis voters decide the future of the city's water supply in a special Tuesday mail-in election, has stoked both sides of the contentious issue.
Opponents on Wednesday attacked the city's decision as a conveniently timed ploy to scare residents and influence the Tuesday tally.
"We think it's very suspicious that city staff shut down Well 30," said Michael Harrington, a Davis attorney and a chief opponent of Measure I. "We think they're manipulating the water supply system," Harrington said. "It's a scare tactic."
Davis' Measure I asks Davis voters to proceed with a multimillion-dollar plan to join with Woodland to draw and treat water from the Sacramento River.
The estimated $245 million Surface Water Project is slated to provide a combined 30 million gallons a day to the two cities 12 million gallons a day for Davis, 18 million for Woodland to supplement the cities' groundwater.
One of the city's highest-producing wells and responsible for more than 10 percent of Davis' water supply, Well 30 is also the highest-producing well on Davis' west side, pumping some 2,300 gallons per minute in the high-demand summer months, Jensen said.
City water officials have been watching Well 30's manganese levels for some time, inspecting the well quarterly for contamination since 2008, Jensen said, far more frequently than state mandates requiring inspections once every three years.
Manganese is a required nutrient, according to the California Department of Public Health, but at very high levels can pose a neurotoxic risk, particularly to children, according to the department.
The well near Lake and Covell boulevards is one of 20 wells in a city that relies solely on groundwater. It's also the second of the city's six deep-water wells forced to shut down. The other is inoperable because of structural damage, Jensen said.
Measure I proponents seized on the timing of the troubled Well 30's shutdown this week and earlier water woes, saying it proves the need for the water project.
"The intermediate-level aquifers are failing. Now we're seeing deep-level aquifers have contamination as well," said Elaine Roberts Musser, chairwoman of the city's Water Advisory Committee and a main proponent of Measure I and the water project.
"We need to diversify our water portfolio. You can't keep relying on well water," Musser said. "What do you do if in the summer peak time you have to shut down a well?"
While Davis works to answer that question, the measure's opponents say the project is too expensive Davis' share of the costs is estimated to exceed $100 million.
They say Davis leaders haven't fully explored other less-costly options including working a water delivery deal with West Sacramento or a regional water plan with Woodland, West Sacramento and UC Davis.
Supporters say the project would ensure that Davis has a clean, long-term water supply while saving millions of dollars by joining forces with Woodland to comply with state clean-water requirements.
Meanwhile, treating and reopening Well 30 will be a costly fix. Jensen estimated the cost at $2.6 million.
Meanwhile, Davis is mulling its options.
Davis has an agreement with UC Davis to pull water from university wells if needed. The city may also be able to apply for a permit to use the well on a very limited basis, Jensen said. City staffers will soon talk with state Department of Public Health officials to determine the next steps.
In the interim, Jensen said Davis will have to fall back on lesser-quality wells, including wells with higher levels of selenium and other materials, she said.
"What it means for us is that we will be using wells that are lower down the list," she said.