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Date October 15, 2003 ,F <br /> ARCO QUARTERLY GROUNDWATER MONITORING REPORT <br /> Facility No: 6100 Address: 25775 Patterson Pass Road,Tracy, CA <br /> i ARCO Environmental Engineer: Paul Supple <br /> Consulting Co./Contact Person: Stratus Environmental, Inc. /Jay R. Johnson, R.G. <br /> l <br /> � Consultant Project No: U6100-14-4 <br /> Primary Agency/Regulatory ID No: Nuel Henderson 1 San Joaquin County Environmental Health <br /> ii <br /> Department/1708 i <br /> BRIEF HISTORY <br /> Four gasoline UST's, one waste oil UST, and associated product piping were removed 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 t <br /> f February 1, 2000. The RWQCB denied the request, and requested a groundwater investigation. <br /> One soil boring (B-32) was drilled at the site to a depth of approximately 200 feet bgs in August 2000. 1 <br /> Groundwater monitoring well MW-1 was installed in this boring to a depth of approximately 115 feet bgs. j <br /> 1 f Following construction of the well, free product was observed in the well. Floating product has been <br /> li removed manually from the well on a weekly basis since September 2000. <br /> 4 <br /> t <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 /> I` hole geophysical log completed. An air rotary casing hammer rig was used to install a well (B-2 through <br /> E B-9) adjacent to each of the soil borings. I <br /> 5 <br /> i The dispensers and product piping were, replaced during the first quarter 2002. Delta collected f <br /> compliance soil samples between January,18 and February 11, 2002. Lateral conveyance piping was <br /> i installed to selected vapor and monitoring wells for future use in soil vapor extraction. Piping was stubbed <br /> f <br /> up in the northwest corner of the property which is the proposed future location of the treatment system <br /> ai I compound. <br /> { WORK PERFORMED THIS QUARTER(Third 2003): <br /> ij <br /> r <br /> 1. A Stratus technician conducted eleven site visits during third quarter 2003 to measure the <br /> thickness and remove floating product from well MW-1. When present, floating product in VW-4 <br /> was also measured and bailed. I <br /> 's <br /> 2. Stratus monitored all vapor extraction and monitoring wells for the presence of water and free <br /> product on September 18, 2003. Stratus returned to the site on September 19, 2003 and <br /> attempted to collect a water sample from every well where the presence of water was detected. l <br /> Groundwater samples were collected from wells MW-2, VW-6, and the domestic well. In most,of <br /> the other wells, the thickness of water in the well (if present at all) was not great enough to enter 4 <br /> the bailer, or sediment in the well prevented the bailer check valve from seating, allowing water to <br /> drain from the bailer before it could be retrieved from the well. k <br /> } . <br /> PABp-Arco for VRS161001Quarter1y120031Arco 6100_3Q03.doc 5ITeATUS <br /> .i <br /> I y <br />