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v California Regional Water Quality Control Board Winston H. Hickox Secretaryfor Environmental Protection Central Valley Region _ Robert Schneider, Chair LEC � �.1ty Davis Sacramento Main Office Governor Internet Address: http://www.swrcb.ca.gov/—rwgcb5 S E p 6 2003 3443 Routier Road, Suite A, Sacramento, California 95827-3003 Phone (916) 255-3000 • FAX (916) 255-3015 AVIRUNMENT HEALTH 25 September 2003 PERMIT/SERVICES Mr. William Barber Group Environmental Management Company 4850 East 49th Street Cuyahoga Heights, Ohio 44125 SOIL VAPOR INVESTIGATION, BP/ APPLIED AEROSPACE STRUCTURES CORPORATION, STOCKTON, SAN JOAQUIN COUNTY We have reviewed the 3 September 2003 Soil Vapor Investigation Vicinity of Well MW -5R (Report) for the BP/Applied Aerospace Structures Corporation (BP/AA) site in Stockton, submitted on your behalf by Parsons Engineering Sciences. Parsons conducted the investigation because trichloroethylene (TCE) pollution continues to be found seasonally in monitoring well MW -5R. Although BP/AA operates a groundwater extraction and treatment system, MW -5R is outside the capture zone. We are concerned that chlorinated solvents may be migrating off-site where there is no downgradient well. You conducted the soil vapor study to determine if there is a local source of the TCE. The survey consisted of advancing nine Geoprobe® borings and collecting soil gas from three to five depths in each boring. You also attempted to obtain grab groundwater samples from the borings, but were only successful in getting samples from borings SVB-8 and SVB-9. The groundwater sample from SVB-9 did not contain any volatile organic compounds (VOCs). The sample from SVB-8 contained 5.9 ug/l 1, 1 -dichloroethylene (1,1-DCE), 3.1 ug/1 of 1, 1 -dichloroethane, and 1.7 ug/l TCE. These values are similar to those found in the first quarter 2003 sampling event. The survey found very low levels of chlorinated solvents in the soil gas. The maximum concentrations detected were found 40 feet deep at sampling location SVB-8, which contained 2.96 mg/m3 of total chlorinated hydrocarbons, 2.64 mg/m3 of 1,1-DCE and 0.088 TCE. These amounts are orders of magnitude lower than those found in soil gas in the source area from a 4 December 2000 survey, which detected up to 1,980 mg/m3, 18 mg/m3, and 38.4 mg/m3 of total chlorinated hydrocarbons, 1,1-DCE and TCE, respectively. SVB-8 is located in an alley between two buildings. Additional soil gas sampling is unlikely to be beneficial because access is limited due to development on the property and because the results of the May/June 2003 sampling did not clearly show a source for the pollution. The Report recommends installing a downgradient monitoring well on the property southeast of MW -5R. We concur with this proposal as an interim measure to clarify whether chlorinated solvents are leaving the BP/AA property. However, if the downgradient well contains TCE or if the amount of TCE California Environmental Protection Agency ca Recycled Paper The energy challenge facing California is real. Every Californian needs to take immediate action to reduce energy consumption. For a list of simple ways you can do to reduce demand and cut your energy costs, see our Website at http://www.swrcb.ca.gov/rwgcb5.