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Date October 15, 2004 <br /> ARCO QUARTERLY GROUNDWATER MONITORING REPORT <br /> Facility No 6100 Address 25775 Patterson Pass Road, Tracy, CA <br /> ARCO Environmental Engineer Paul Supple <br /> Consulting Co/Contact Person Stratus Environmental, Inc /Jay R Johnson, R G <br /> Consultant Project No U6100-14-4 <br /> Primary Agency/Regulatory ID No Nuel Henderson 1 San Joaquin County Environmental Health <br /> Department/ 1708 <br /> BRIEF HISTORY <br /> Four gasoline UST's, one waste oil UST, and associated product piping were replaced in 1987 Between <br /> 1991 and 1995 a total of 31 soil borings were drilled to depths between 26 and 115 feet below ground <br /> surface (bgs) Twenty vapor extraction wells (VW-1 through VW-20) were installed in selected borings <br /> Pinnacle Environmental Solutions, Inc submitted a request for "No Further Action" to the RWQCB on <br /> February 1, 2000 The RWQCB denied the request, and requested a groundwater investigation <br /> One sod boring (B-32) was drilled at the site to a depth of approximately 200 feet bgs in August 2000 <br /> Groundwater monitoring well MW-1 was installed in this boring to a depth of approximately 115 feet bgs <br /> Following construction of the well, free product was observed in the well Floating product has been <br /> removed manually from the well on a weekly basis since September 2000 <br /> During August and September 2001, Delta advanced six onsite mud rotary soil borings (B-33 through <br /> B-38) to depths up to 140 feet bgs In each boring, soil samples were collected continuously and an open <br /> hole geophysical log completed An air rotary casing hammer rig was used to install a well (B-2 through <br /> B-9) adjacent to each of the sod borings <br /> The dispensers and product piping were replaced during the first quarter 2002 Delta collected <br /> compliance soil samples between January 18 and February 11, 2002 Lateral conveyance piping was <br /> installed to selected vapor and monitoring wells for future use in soil vapor extraction Piping was stubbed <br /> up in the northwest corner of the property which is the proposed future location of the treatment system <br /> compound <br /> Upon approval of RAP, Stratus installed two SVE systems to facilitate sod vapor extraction from wells <br /> VW-1, VW-3, VW-4, VW-6, VW-7, VW-8, VW-11, VW-12, VW-13, VW-14, VW-16, and MW-2 through <br /> MW-9 The SVE system was started for continuous operation beginning March 15, 2004 in accordance <br /> with San Joaquin Valley Air Pollution Control District's (SJVAPCD) authority to construct (N-5026-1-0 & <br /> N-5026-2-0) <br /> WORK PERFORMED THIS QUARTER (Third 2004) <br /> 1 Stratus conducted eight site visits during the third quarter 2004 to conduct operation and <br /> maintenance of the two SVE systems, to remove floating producting from well MW-1, if present, <br /> and to collect compliance discharge samples <br /> 2 Stratus prepared and submitted to SJCEHD, a Subsurface Assessment Report And Site <br /> Conceptual Model Update, dated September 3, 2004, documenting the findings of well installation <br /> and destruction activities conducted between February 2004 and April 2004 <br /> P 1Bp-Arco for URS\61001Quarter]y120041Arco_6100_3Q04 doc STRATUS <br />