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California&gional Water Quality Co*l Board ` <br /> Central Valley Region <br /> Linda S.Adams <br /> 5'ecrem,yj6r Sacramento Main Office Arnold <br /> Environmental 11020 Sun Center Drive#200,Rancho Cordova,California 95670-6114 Sehwarzenegger <br /> Protection Phone(916)464-3291 •FAX(916)4644645 Governor <br /> http://w".waterboards.ca.gov/centralvalley <br /> To: Pamela C. Creedon FROM: Jim Barton <br /> Executive Officer Engineering Geologist <br /> Underground Storage Tanks <br /> Brian Newman Enforcement Unit II <br /> Supervisory Water Resources Control <br /> Engineer r <br /> SIGNATURE: <br /> RobertBusby <br /> Senior Engineering Geologist <br /> DATE: 13 December 2006 <br /> SUBJECT: NON-CONCURRENCE WITH SAN JOAQUIN COUNTY'S NO FURTHER <br /> ACTION REQUIRED DETERMINATION, SHELL NO. 204-7524-4404, 3011 W. <br /> BENJAMIN HOLT DRIVE, STOCKTON, (CASE #390557) <br /> On 30 August 2006, 1 received the San Joaquin County Environmental Health Department's <br /> (SJCEHD) Case Closure Summary (attached letter) for the Shell No. 204-7524-4404 (Shell), <br /> 3011 W. Benjamin Holt Drive in Stockton (Site, Figure 1, and SJCEHD Aerial Photograph 1B), <br /> with a request for concurrence from the Executive Officer of the Central Valley Regional Water <br /> Quality Control Board (Regional Board) to the no further action required determination. <br /> I reviewed the Case Closure summary and the Site file, and do not concur with the closure <br /> recommendation. Below is a summary of the Site history (Attached SJCEHD Chronology) and <br /> my comments. <br /> Background <br /> Shell conducted quarterly groundwater monitoring at the Site (Figure 2) from February 1994 <br /> through April 2006, but did not conduct groundwater remediation. Groundwater is very <br /> shallow at this Site. The groundwater elevation varied from four to nine feet below mean sea <br /> level (The depth to water varied from four to eighteen feet below ground surface, due to some <br /> of the monitoring wells located in the off-ramp of the elevated Interstate 5). The inferred <br /> direction of groundwater flow varied from North to Northeast at an average gradient of <br /> 0.003 feet/feet. <br /> There have been releases at two locations at this Site: <br /> • Release #1, from a first generation (Gen 1) of USTs removed in 1987 and 1996. Shell <br /> reported low levels of petroleum hydrocarbons in soil in 1990, and also in groundwater <br /> in 1994, and <br /> • Release #2, from a second generation (Gen 2) of USTs installed in 1996 approximately <br /> 120 feet Southeast of the Gen 1 tanks and removed in 2004. Shell reported high levels <br /> of MtBE in groundwater, which increased three orders of magnitude from 1996 to 1997. <br /> California Environmental Protection Agency <br /> C3 Recycled Paper <br />