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07/26/2001 10:17 4156590148 ESA PAGE 02 <br /> Fo-ironrmnial <br /> EA uucwFei <br /> July 26,2001 <br /> Ms. Dot Lofstrom,R.G. <br /> San Joaquin..County public Health Services <br /> Environmental Health Division <br /> 304 East Weber Street <br /> Stockton,California 95202 <br /> Subject: Proposed Groundwater Monitoring Well Locations <br /> Former Underground Storage Tank Site <br /> University of the Pacific(UOP)Physical Plant <br /> 1081 W.Mendocino Avenue,Stockton,California <br /> Dear Ms.Lofstrom: <br /> Enviromlmntal Science Associates(ESA)has prepared the attached map showing the proposed locations of <br /> four groundwater monitoring wells at the site referenced above. Ile purpose of the proposed wells is to <br /> further delineate the extent of methyl tertiary-butyl ether(lVME)in soil and groundwater. MTBE was first <br /> detected at the bottonk of the former UST excavation following the removal of a 4,000-gallon gasoline tank <br /> in April 2000. Concentrations of petroleum hydrocarbons(gasoline)were either not detected or at very low <br /> concentrations. The July 20M soil and groundwater investigation detected concentrations of up to 1,200 <br /> rOicrograrlas per liter(µg/L)MTBE in boring TP-4,and 160 ng L in boring TP-5. ESA's subsequent soil and <br /> groundwater investigation in January 2001 did not detect concentrations of MTBE in 10 borings installed <br /> outside of the former tank pit. <br /> Basad upon the results of previous investigations and in response to San Joaquin County Environroental <br /> Health Division(SICEM)well,installation request dated A.priI 25,2001,ESA.is proposing to install four <br /> groundwater monitoring wells at the locations shown on the attached map. Well locations were selected to <br /> monitor potential MTBE concentrations upgradient,downgradient,and erossgradient of the fanner tank pit. <br /> An additional well is proposed near boring TP-4 to monitor previously detected concentrations of MTBE is <br /> the fomes tank pit. ESA is submitting the proposed well location map in order to expedite future SJCEHD <br /> review of the well installation workplan. <br /> We have appreciated your assistance and the help we have received from your department throughout the <br /> course of this project. Following SJCEHD approval of well locations,BSA will submit a well installation <br /> workplan describing the proposed field work,well specifications,and field methodologies. If you require <br /> additional infornmdon or have questions,please call Ms.Jennifer Schulte or me at(415) 896-5900. <br /> Sincerely,-� <br /> fJ ,' <br /> y i <br /> Peter B.Hudson, (3. <br /> cc: John Forsythe,ESA Sacramento <br /> Crystal Steell,ESA Sacramento <br /> 223/ouch Scntc.Suice 1700 San kruacuco,Gdifamia 94304 (41P896-19W fox $94-0332 mail;en.stomewoe.cam <br />