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• Quik Stop No 121 Closure Report CCI Project No 12118 Page 3 500 feet southeast of the site Subsurface conditions encountered at this location also consisted of alternating layers of clay, silty clay, sand and gravelly sand to a depth of approximately 43 feet Below this interval and extending to a depth of 62 feet, the soil became less granular and consisted of silty sand to silty clay and clay There were several localized areas of hard pan material CPT-2 was terminated at 62 feet due to refusal Groundwater in the vicinity of monitoring well MW-3 continued to contain the highest petroleum hydrocarbon concentrations at the subject site It appears some MTBE may have migrated to a lower portion of the A-aquifer,to a depth of 35 to 38 feet, as confirmed by the water sample collected at CPT-1 In addition,the water sample collected from CPT-1 was also reported to contain low concentrations of tetrachloroethene, a widely used dry cleaning solvent The source of the tetrachloroethene is not known No petroleum hydrocarbon concentrations were detected in the two water samples collected at CPT-2,which was located approximately 500 feet southeast of the site, in the direction of the City of Manteca's municipal well No 15 CCI collected information on the municipal well, which is 16 inches in diameter and was drilled to a depth of 360 feet in 1985 The well drillers' report, obtained from the State of California, Department of Water Resources, indicates the subsurface lithology consists of alternating layers of sand and clay to the bottom of the boring The well itself is perforated at two intervals, the first at 140 to 180 feet and the second at 205 to 265 feet A 2,000-gallon per minute(gpm) pump is used in the well CCI obtained a monthly production log from the City of Manteca The log indicates that during the months of May, June and July, 2000, the volume of water pumped from the well was approximately,24 million, 31 million and 40 million gallons, respectively On September 18, 2000, CCI submitted a Work Plan to install additional monitoring wells at the subject site From November 29 through December 29, 2000, CCI installed a total of four new groundwater monitoring wells and one recovery well This included one well located on the adjacent property, at 1190 W Louise Avenue, and four additional wells installed on the Qurk Stop Market site to monitor groundwater conditions at several different depths Based on the information obtained from the November and December 2000 investigation, as well as from previous investigations conducted at the site, it appeared the groundwater continued to be impacted with petroleum hydrocarbons, mainly in the vicinity of Quik Stop Market's fuel tanks on the southeast side of the site, near monitoring wells MW-3 and RW-1, and on the northwest side, at MW-1 Perimeter wells MW-2, MW-5 and MW-7 were free of detectable TPHg and BTEX compounds In January 2001, groundwater in the vicinity of monitoring wells MW-3 and RW-1 were reported to have the highest contaminant concentrations of TPHg and MTBE at the subject site • It appeared some TPHg and MTBE had migrated to a lower portion of the A-aquifer, at a depth