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California Regional Water Quality Control Board Central Valley Region • Steven T. Butler,Chair Gray Davis ,Vinston H.Hickox Secretaryfor Sacramento Main Office Governor Environmental Internet Address: http://www.surcb.ca.gov/—rwgcb5 Protection 3443 Routier Road,Suite A,Sacramento,California 95827-3003 Phone(916)255-3000•FAX(916)255-3015 TO: GorOn L. Boggs FROM: Marty Hartzell UST Program Manager Associate Engineering Geologist DATE: 3 February 2000 SIGNATURE: SUBJECT: NONCONCURRENCE WITH SAN JOAQUIN COUN 'S NO FURTHER ACTION REQUIRED DETERMINATION, EGGIMAN'S HYDRAULIC, 1112 EAST HARDING WAY, STOCKTON I reviewed the 29 December 1999 Case Closure Summary for Eggiman's Hydraulic submitted by San Joaquin County Environmental Health Division (County), and the 14 October 1999 Closure Report prepared by ATC Associates, Incorporated (ATC). Two gasoline underground storage tanks (USTs) were removed from the subject site in April 1987. Six soil borings were completed in July 1997, and TPHg, TPHd, and BTEX constituents were identified at the subject site. The maximum concentrations found in soil samples collected in July 1997, show TPHg at,9,100 mg/kg and benzene at 0.90 mg/kg. MtBE was not found using EPA Method 8020 with detection limits ranging from 0.01 to 10 mg/kg. The lateral extent of soil contamination has been defirke,d to the immediate area surrounding the former USTs, however the vertical extent of soil contamination has only been defined to 30 feet below ground surface (bgs) in one soil boring. ATC stated that the minimum depth to groundwater is approximately 55 feet bgs as provided in the 1997 San Joaquin County Flood Control and Water Conservation report. No attempt has been made to reach groundwater. A well survey was completed, and fourteen wells were identified within 2,000 feet of the former UST area. The nearest well, an active irrigation well, is located approximately 800 feet west of the site at the State Hospital. The first well screen interval is from 79 to 83 feet bgs. ATC stated in the Closure Report that the groundwater flow direction is to the northeast, as determined from another site located one mile southwest of the site. While the irrigation well is in the presumed upgradient direction, groundwater gradients in this area are relatively flat, and the irrigation well may influence local flow directions. Based on the findings of TPHg at a maximum concentration of 9,100 mg/kg in soil, detectable soil contamination to 30 feet bgs, and groundwater levels at 55 feet bgs, a groundwater sample should be obtained. Therefore, San Joaquin County's closure recommendation is not appropriate at this time. For concurrence, Eggiman's Hydraulic must collect a groundwater sample near the former UST sites and analyze the sample for TPH, BTEX, and fuel oxygenates. Upon submittal,the analytical reports can be reviewed and evaluated to see whether further investigation is necessary. If the groundwater analyses show no further action is warranted, submit a revised closure recommendation, and a No Further Action Required letter can be issued. California Environmental Protection Agency �a Recycled Paper