Vallejo parking garage may have led t...

Vallejo parking garage may have led to contaminated groundwater

Posted in the San Pablo Forum


Vallejo, CA

#1 Feb 1, 2013
Vallejo parking garage may have led to contaminated groundwater

The green metal bins next to Vallejo's new downtown parking garage will be part of the landscape for the foreseeable future due to contaminated groundwater associated with the project, officials said. The likely pollution culprit could be an old gas station which has long since disappeared from the downtown's waterfront, officials said. Soon after the waterfront parking garage opened in October, the state slapped the city with a violation for releasing contaminated groundwater into the Mare Island Strait. That unauthorized release, plus detection of contaminants, has presented something of a detour.

The three-story, 750-parking space structure on Santa Clara Street and Mare Island Way opened in October after months of delay. The city's task now is to try to determine the source of the groundwater contaminants, and file for a permit to treat and discharge the water into strait, state and city staff said. Meanwhile, the green bins will stay. Public Works Director David Kleinschmidt said the pollution is minor and the contaminants are "petroleum products," which point to the presence of a former gas station. "It's something in the ground adjacent to the parking structure. The groundwater is flowing through it and picking up contaminants," Kleinschmidt said.

Another likely factor is that the garage, which is partially underground, was built below the water table, said Stephen Hill, Toxics Cleanup Division Chief of the San Francisco Bay Regional Water Quality Control Board. "If they hadn't stuck their parking garage below the water table they wouldn't have to take all these steps," Hill said. "One might say it's an inevitable problem."

Kleinschmidt denied the underground construction is a factor, and said the problem stems from groundwater seeping into the structure's storm drainage system. Earlier steps may have been taken to deal with the issue, but the contaminated groundwater was not discovered until near the end of the garage's construction, Mercurio said.

"None of the initial testing indicated there would be contaminated groundwater," and so a specialized collection and treatment system was not designed into the project, Mercurio said. To compound matters, as the city was trying to deal with the situation, a large rain storm hit in October, sending 4,000 gallons of water into the strait, Mercurio said. The combination of the groundwater and the large volume of water overwhelmed the system, she said. "That's our challenge -- the groundwater and rainwater collection for the garage is combined," Mercurio said.

Kleinschmidt said the amounts of groundwater and various runoff fromthe planters and other areas are very small and the levels of contaminants "barely cross the threshold" of what can be discharged into the strait. The groundwater and other water associated with the garage had been previously being sent to Vallejo Sanitation and Flood Control District which had been releasing it into the strait through a city discharge permit, Mercurio said. Following the unauthorized release into the strait, the bins and a temporary treatment facility went up, and the city needed to take more steps to deal with the contamination.

A temporary arrangement has been made to send the water collected in the bins to Vallejo Sanitation and Flood Control District for discharge, Mercurio said. In addition, the city is working with an engineering firm to design an appropriate permanent collection and treatment facility which, will, eventually, allow the green bins to be removed, she added. Regional board chief of wastewater control Lila Tang said the city cannot yet meet the permit requirements and so must have the bins in place. "Until we can identify the source of the pollutants and remediate it those green structures will remain there," Kleinschmidt said.

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