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' Mr. Donald Rodgers - 2 - • 6 June 2007
<br /> 515 West Charter Way, Stooton, San Joaquin County
<br /> Maximum roundwater results in October 2006 in p /L were:
<br /> Well Screen TPH B T E X
<br /> MW-4RS 35-50 14,000 5,300 560 2200, 870
<br /> MW-4RD 75-80 1,600 230 55 58 230
<br /> VW-2D 11-23 30,000 5,600 1,300 1,500 5,900
<br /> 1-well screen interval in feet bgs 2—Benzene 3—Toluene 4—Ethylbenzene 5-Xylenes
<br /> Soil Vapor Extraction (SVE), conducted from February 2000 until October 2004, removed
<br /> approximately 3,244 pounds of TPHg and 4.9 pounds of benzene from the vadose zone soil.
<br /> In March 2006, nine direct push soil borings (MIP-1, -1a, -1 b, -2, -3, -4, -5, -6, and —7,
<br /> Figure 2) were advanced, using a real-time Membrane Interface Probe (MIP). The MIP
<br /> investigation showed locally high hydrocarbon responses from 25 feet bgs down through
<br /> 61 feet bgs, and approaching non-detect at 65 feet bgs, the maximum MIP depth investigated.
<br /> Soil samples for laboratory analyses were also collected from direct push soil borings (DP-3,
<br /> -4, -5, -6, -8, and —9, Figure 2). Maximum soil laboratory results were: TPHg, 5,900 mg/kg;
<br /> TPH as diesel (TPHd), 1,400 mg/kg; B, 5.5 mg/kg; E, 17 mg/kg; T, 14 mg/kg; and
<br /> X, 108 mg/kg. Analyses of one grab groundwater sample (MIP-1-W), collected from 24 to 27
<br /> feet bgs, reported. TPHg, 32,000 ug/L, TPHd, 24,000 ug/L; B, 2,960 ug/L; T, 885 ug/L;
<br /> E, 1,690 ug/L; and X, 7,520 ug/L. Petroleum hydrocarbon sheen was noted in two DP-9 soil
<br /> samples, collected between 47 and 54 feet bgs.
<br /> In a letter dated 24 January 2007, SJCEHD required the submittal of the following items by
<br /> 30 March 2007:
<br /> 1) A workplan to delineate the vertical extent of the petroleum hydrocarbons, and
<br /> 2) A feasibility study for remediation of groundwater;
<br /> 3) The sampling reduction from quarterly monitoring to annual monitoring for wells MW-2R
<br /> and MW-3R, and
<br /> 4) Submittal of all reports to GeoTracker.
<br /> The SJCEHD also required that quarterly monitoring continue until directed otherwise by that
<br /> agency.
<br /> On 30 April 2007, the SJCEHD issued written notice that the site would be transferred to the
<br /> Regional Board if the workplan and feasibility study were not received within 14 days. To
<br /> date, none of the required submittals have been made and quarterly monitoring has not
<br /> resumed.
<br /> I have conducted a preliminary case review and agree with the previous directions given by
<br /> SJCEHD. Therefore, you are to comply with all SJCEHD directives given to date, including but
<br /> not limited to:
<br /> • Submit a workplan for an additional investigation to delineate the vertical extent of the
<br /> petroleum hydrocarbon release to soil and groundwater by 20 July 2007. A report of
<br /> the investigation, due 20 September 2007, shall provide conclusions and
<br /> recommendations for additional investigation or remediation, if warranted.
<br /> • By 20 July 2007, submit a feasibility study for remediation of groundwater.
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