After much public controversy, the computer chip makers who leaked the industrial solvent into the area's groundwater table eventually tested her home in 2003. Unacceptable levels of TCE vapors had made their way through the soil and into her home, and the polluters paid for a system to ventilate her cellar.
"TCE is carcinogenic to humans by all routes of exposure," and human health effects include kidney and liver cancer, lymphoma and various other reproductive, developmental and neurological effects, according to the EPA in a report issued in December.
In an Aug. 16 update to what is called a Record of Decision, the EPA has finally formalized the procedures used for Horton and others in order to protect residents and workers in northeastern Mountain View. The document pertains to a superfund site roughly bordered by Middlefield, Ellis and Whisman roads called the MEW.
On top of formalizing the plume map and, the updated document means that, building by building, a plan must now be in place to remediate unacceptable levels of toxic fumes in dozens of commercial buildings. And it is expected to be paid for by the polluters, or what the EPA calls "responsible parties."
Horton said she believed the EPA document is a model, and EPA project manager Alana Lee acknowledged that it was receiving a lot of attention from other EPA regions and EPA headquarters.
While EPA region 9 has been implementing many of the things called for the document for years, this document "protects you from the whim of politics," Horton said.
With the EPA being a creature of presidential politics, acceptable vapor levels and cleanup goals have sometimes changed in the face of political pressures.
"I think we are all at the whim of whatever president we have," Horton said. "You have so many instances where some politician or official says 'We've determine your home no longer qualifies or we've determined you are no longer unsafe at X parts per billion,'" Horton said. "But we've got it in this document."
Lee acknowledged that the document does make it more difficult to change the EPA's positions on the MEW plume, as a public process would be required.
Despite knowing of the problem for over a decade, 117 commercial buildings in the area and dozens of homes remain untested for toxic vapors.
The document was originally drafted in 1989, but only with last month's update does it deal with the most problematic vapor intrusion aspect of the TCE groundwater pollution. It is the result of the solvent TCE being released from leaky tanks into the groundwater by early computer chip makers located in the area. The companies responsible include Intel, Raytheon and Fairchild Semiconductor.
Lee said of the commercial buildings have yet to have their indoor air sampled, 36 of are located in the largely inhabited industrial park south of Highway 101. The others are located at Moffett Field, where many sit vacant awaiting redevelopment.
Unlike commercial buildings, the testing of homes above the plume is voluntary. That includes apartment buildings, such as the 64 units at 291 Evandale Ave., which went untested until recently — the results have yet to be released.
The EPA has sampled the indoor air of only 35 of 100 homes in the study area along the western edge of Whisman Road. Of those tested, only Horton's home was found with unacceptable levels of TCE vapors in the indoor air, likely because her home, built in the late 1800s, has an earthen cellar.
Lee said the EPA has notified homeowners in the past that they can have their indoor air tested, but many have chosen not to. Some feared it could affect their property values, Horton said.
Clearing the fumes
All that now stands between Horton and toxic fumes is a "remediation" system that ventilates and monitors the toxic fumes in her cellar that initially cost $4,500. Horton has lived in the house since 1975. While she did not want to get specific, she believes that it has had consequences for the health of some of her family.
About 75 percent of the toxics in the MEW plume had been cleaned up by the time Horton learned her home was affected. The last bit is likely to prove hardest to clean up. Systems that pump the water to the surface and filter out the TCE may soon be replaced by bacterial microbes that are injected into the groundwater to dissolve the harmful chemicals. The U.S. Navy is currently testing three different types at Moffett Field.
Lee said another update to the document will soon identify preferred cleanup alternatives for the future.
While homeowners were asked to comment on a draft of the document last year, only a half dozen did, including Horton. One expressed concern that homeowners were not notified of the problem.
The largest response to the draft came from a group of property owners in the MEW who made numerous formal, anonymous comments. Among their comments they called the EPA document "unnecessarily stigmatizing" for properties in the area. They also said that it should be made clearer that the cost of remediation is the responsibility of polluters.
Among the innovations in the document, Horton pointed to a partnership between the EPA and the city to require new buildings be built on top of a "passive sub slab" system which vents the vapors to the building's roof. The average "present worth" of such a system is $207,500 for a 20,000 square foot building and $36,500 for a home.
As for Horton, she was recently able to have the responsible parties pay for the electricity used by her remediation system. Soon, she hopes to be reimbursed for its past electricity use.
The Record of Decision can be found at www.epa.gov/region9/MEW.
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