Depending on the methods used, cleanup could take anywhere from 15 years to 50 years, said Raymond Chavira, project manager for the Environmental Protection Agency. The EPA is recommending the fastest method, which involves the use of microbes to break down the contaminants into non-toxic gases, while the slowest method relies entirely on natural bacteria to do the same.
CTS Printex, which still exists as Indiana-based CTS Corporation, is on board with the EPA's proposal to finish the cleanup quickly, once and for all, Chavira said.
The $1.8 million preferred alternative, which CTS would pay for, involves circulating the microbes in the most concentrated part of the groundwater, which measures 60 feet across and is 25 feet deep. The rest of the plume, which has relatively low levels of contaminants, would be cleaned through "natural attenuation" — broken down by the natural bacteria in the soil over the course of 15 years.
Lenny Siegel, director of the Center for Public Environmental Oversight, said it appears that the EPA was doing a good job in coming up with a plan for the site, with lessons learned from similar efforts at the MEW Superfund sites in Mountain View's Whisman neighborhood.
Most of the contaminants are moving north towards the Bay. The highest concentration of the plume is now under a parking lot in the middle of a small complex of commercial buildings at 935 Sierra Vista Ave. and against Highway 101, where the plume appears to have stopped flowing north, Chavira said. Checks of groundwater wells north of Highway 101 near Google headquarters have found little or no TCE, Chavira said.
"This mass is in the parking lot there," Chavira said of 935 Sierra Vista Ave. "We can install our system in there, inject the microbes into the ground and recirculate it. It could take less than a year. Once we get this, everything else is basically natural attenuation."
"If we don't do anything, it might be 30, 40, 50 years to reach maximum cleanup levels. But if we can do this, we think it will be 15 years," Chavira added.
Chavira said the EPA would take into account the input of residents. "If in the end they say, 'We really don't care if it's 50 years or 60 years,' we will consider that."
EPA tests homes for indoor air safety
When Regis Homes built dozens of three-story town homes at the east end of Plymouth Avenue, every home was built with a sub-slab system to prevent vapor intrusion, and every home was tested after construction for indoor air quality — a test every home passed, Chavira said.
Just across Plymouth Avenue, and closer to the "mass" of contaminants, is a housing complex at 917 Sierra Vista that was not found to have levels of indoor air contamination as a result of the plume that would warrant action, Chavira said. The Chinese Church in Christ across the street has not had its indoor air tested, but Chavira said the levels of contaminants in the plume, which sits under only a portion of the church, were below action levels. But if the church were to develop on its parking lot to the north, the EPA would have to review building plans, Chavira said.
The EPA is also coming up with possible requirements for future development over the plume which could be required to have expensive sub-slab systems to prevent vapor intrusion, depending on their location.
Another promising cleanup method uses pieces of scrap iron, buried in the water table, to chemically break down the TCE. This method could also take 15 years, but would cost $2.8 million, the EPA reports. Another alternative is to extract the groundwater and filter it for $4.4 million, but that's already been done and would likely be ineffective. Between 1987 and 1996, 106 million gallons of groundwater were extracted from the site and 99 pounds of TCE is believed to have been filtered out of the water, the EPA reports.
A meeting is scheduled for residents to give feedback to the EPA about its proposals on Wednesday, June 15. The meeting runs from 7 p.m. to 9 p.m. and will be held in the second floor plaza conference room at City Hall, 500 Castro Street.
For more information, EPA project manager Raymond Chavira can be reached at (415) 947-4218 or email@example.com.
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