None of the contamination is threatening homes, but it is causing some concern about vapors penetrating commercial buildings.
The underground contamination from the "Hewlett-Packard 620-640 Page Mill Road Superfund Site" is detailed in a five-year review released Sept. 30 by the California Regional Water Quality Control Board San Francisco Bay Region.
It is the third five-year study of the site.
In addition to the increased concentration in a few areas, inspectors have also noted a slow decrease in contamination in other areas of the site, the report states.
The contaminated plume emanates from the former HP site and combines with contamination from two other locations: the former Varian Medical Systems, Inc., facility at 601 California Ave. and the former HP facility at 395 Page Mill Road.
The plume, which contains heavy metals and toxic chemicals known as volatile organic compounds (VOCs), has affected groundwater under parts of Stanford Research Park, the Palo Alto Mayfield soccer complex, Palo Alto Square, Fry's Electronics and the Palo Alto Courthouse, among numerous other businesses.
Contamination has not spread into the adjacent residential areas outside of the site, the report said.
The clean up has been ongoing since 1982, after HP detected a toxic leak from a 1,000-gallon underground solvent-storage tank at 620-640 Page Mill Road in 1981 and began remediation to remove the contamination from soil and groundwater. The company left the site in 1986 but continued its lease until 2007.
HP has reported a cumulative cost of $6,788,253 through October 2009 to clean up the contamination.
According to the report — which was created from monitoring done by Stantec, a company hired by HP and Varian — an area just south of the 620-640 Page Mill Road buildings showed trichloroethene (TCE) levels in groundwater increased by 75 percent.
Trichloroethene concentrations increased by 20 percent in a monitoring well near El Camino Real and Page Mill Road between 2005 to 2009. But trichloroethene levels have increased nearly 800 percent in the water collected from two bore holes near the well site at 2875 and 2865 El Camino Real (the northeast corner of El Camino Real and Page Mill Road), according to the report.
The groundwater is not used for drinking or bathing and so does not pose a risk of off-gassing vapors from showers and baths, but inspectors expressed concern about air vapors that could seep into buildings. Rising groundwater levels in some areas have re-saturated soils.
In some areas, contaminated water close to the soil's surface has brought toxic vapors into buildings, according to the report.
The plume extends 1,500 feet northeast under Oregon Expressway and runs from the HP 620-640 Page Mill Road site northward in a finger to California Avenue under the former Varian site. It flows east along Grant Avenue to Alma Street and the Oregon Expressway underpass, then south along Portage and Lambert Avenues, just shy of Matadero Canal, according to report maps.
The site contains contaminants in the soil including arsenic, gallium, trichloroethene (TCE), trichloroethane (TCA), 1,1 dichloroethene (DCE), tetrachloroethene (PCE) 1,2,4 trichlorobenzene and phenol. It was added to the federal Superfund site list in 1990.
The Regional Water Board approved decommissioning groundwater monitoring and extraction wells at the former Mayfield School site on El Camino in 2005. That site was redeveloped by Stanford University into the Stanford/Palo Alto Community Playing Fields soccer complex in 2006.
Inspectors have seen a slow decrease in toxic levels in many areas within the plume area. During the last five years, 880 pounds of VOCs were removed from the 620-640 Page Mill site. In the off-property study area, which includes the Oregon Expressway Underpass area, 1,267 pounds of VOCs were removed.
But because contamination levels have risen dramatically in some areas, Water Quality Control Regional Water Board inspectors want more monitoring and a better analysis of the extent of the contamination and if some areas are emitting vapors from underground.
Groundwater TCE concentrations have also increased in the area at the northwest corner of El Camino and Pepper Avenue. The groundwater is close to the surface and there is potential for contaminating vapors to enter buildings, inspectors said.
Vapor barriers have been tried, but their effectiveness is still not completely known, according to the report. In the Stanford Research Park, HP installed a vapor barrier under portions of the replacement building in 1994 and added a grated entrance to an underground parking area for increased ventilation. The current occupant, Wilson Sonsini Goodrich and Rosati, took indoor air samples in 2009 and found volatile organic compounds on the first floor at one location. None were detected on the second floor. Wilson Sonsini plans to conduct more indoor sampling to confirm its findings at the end of 2010, according to the report.
The study determined the potential vapor-intrusion areas should be re-evaluated within 18 months.
The Superfund site has been the subject of litigation. After the City Council approved a development at 195 Page Mill, Palo Alto residents Bob Moss and Tom Jordan filed suit, contesting the adequacy of the city's environmental review.
In October 2007, Santa Clara County Superior Court Judge Leslie Nichols agreed the city and developer Harold Hohbach had not adequately examined the project's environmental risks, specifically regarding vapors from groundwater contaminated with trichloroethylene and reversed the council's approval.
HP is required to submit its next five-year report to the water board by Feb. 1, 2015, inspectors said.
Read more online
The 58-page, five-year report is posted on Palo Alto Online. Go to the website and search for "Superfund."