The buildings are above the Fairchild Semiconductor Superfund site where toxics dumped or released by the Valley's original computer chip manufacturer are evaporating from the ground — mainly trichloroethylene (TCE), classified as a human carcinogen.
The air in the buildings — part of "The Quad" at 369 and 379 North Whisman Road — must be pressurized at all hours to keep the vapors from rising through the floors. But the system to pressurize the air failed sometime last year, exposing Google employees for two months, in November and December. Levels of TCE were as high as 7.8 micrograms per cubic meter (5 is EPA's limit) — levels that require long-term exposure to cause cancer, but are high enough to cause birth defects if women are exposed during the first trimester of pregnancy, EPA toxicologists say.
The report blames a faulty pressure sensor and improper settings on the building's heating, ventilation and air conditioning (HVAC) system, the result of changes made last fall to increase the building's temperature. The EPA report concluded that "the HVAC systems were operating in a manual mode (i.e., automatic system was overridden) in order to maintain the temperature in the buildings."
The result was a negative pressure in the buildings that drew vapors inside.
Several women who were pregnant while working in the buildings expressed concerns to Lenny Siegel, director of the Center for Public Environmental Oversight. All of their babies were born healthy, he said. There may be other pregnant Google employees there as well.
"The sales folks are down there and there are a lot of women," said Google employee Helen Tsao, who doesn't work in the buildings but whose home on Evandale Avenue is close to enough to the plume that TCE vapors were found inside on Monday. "I did hear about specific incidents of pregnant women who did not want to move down there."
While elevated levels were first discovered in the buildings in November, the problem wasn't found until Jan. 14, when "(n)egative pressure was observed across all exterior doorways in both buildings." It was also found that the "tenant's (Google's) automated HVAC system was reporting erroneous pressure readings" because of a faulty pressure "transducer," or sensor.
On Jan. 19 the problem was fixed, and vapor levels were reduced to trace amounts well below EPA limits, the report says.
To keep such an incident from happening again, "technicians programmed the building static pressure sensor readings to be alarmable," the report says, adding that email messages would be sent to Google's Facilities Operations team if the pressure in the building drops.
The EPA is currently developing a long-term plan for testing the air in the buildings. Before the air was tested last year, the buildings had not been tested since 2010, said EPA spokesperson David Yogi. He added that a "sub-slab depressurization" system is being designed to draw the vapors from the soil under the buildings and exhaust them above the roofline.
Pregnant women would be particularly at risk if the HVAC systems were to fail entirely. With ventilation systems off on Jan. 1, sampling results show concentrations well above the 5 micrograms per cubic meter limit at all of the workplace test locations at 379 Whisman, with levels as high as 120 micrograms per cubic meter. At 369 Whisman, limits were exceeded at four of five of test stations in the workplace, with levels as high as 30 micrograms per cubic meter with no ventilation.
The buildings were constructed before 2011, the year that the city began requiring sub-slab depressurization systems on new buildings in the area. Records show the buildings were also tested in 2003 and 2010, and levels were below EPA limits.
Google has promised to increase efforts to alert employees to the problem, creating an internal website with information and offering to meet one-on-one with employees who are concerned. The EPA has posted the Geosyntec report on the Google buildings online at tinyurl.com/geosyntec.
Michelle Le contributed to this report.