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Project Quarterly Update Report February 21, 1992 Southland, 9110 Thornton Road, Stockton, California Page 2 2.0 WORK SCOPE Services performed by Groundwater Technology during this reporting period included the following ■ Installed one on-site and two off-site monitoring wells on September 16, 17, and 18, 1991 ■ Monitored on-site and off-site observation wells for depth to water and depth to separate-phase hydrocarbons on October 30, November 26, and December 23, 1991 ■ Analyzed groundwater samples collected from five monitoring wells, two monitoring- well clusters, and one pumping well on November 26, 1991 ■ Sampled groundwater from domestic wells 9036, 1912, 8968, 9140, 9156, 1927, and 9172 on October 30, November 26 and December 23, 1991 Note that the well name for 1927 was transposed to 9127 on the October 1991 and November 1991 laboratory reports 2.1 MONITORING WELL INSTALLATION On September 16, 17, and 18, 1991, one monitoring well was Installed on-site and two were installed hydraulically downgradient of the site to provide additional data on water quality Monitoring well MW-20 was Installed on site near the former tank pit location, and wells MW-18 and MW-19 were Installed off site on Connie Avenue (Figure 2) The boreholes for monitoring wells MW-18, MW-19, and MW-20 were drilled with 8-inch outer- diameter, truck-mounted, hollow stem auger equipment The boreholes were continuously cored from a depth of about 35 feet to a depth of about 60 feet for well MW-18 and 65 feet for well MW-19, ' and from a depth of about 5 feet to 65 feet for well MW-20 (approximately 15 feet below the water table) The continuous cores from the two off-site borings and one on-site boring were logged by a Groundwater Technology field geologist to confirm the site lithology, which appears to be laterally and vertically heterogeneous Soil samples were collected during drilling by driving a brass tube Into the continuous core at 5-foot intervals and where changes in Ifthology occurred The samples ' from the on-site boring were capped, taped, labeled, and placed on ice for delivery to a California- certified laboratory under standard chain-of-custody procedures In addition, samples were field- screened with a photo-ionization detector (PID) The results of the PID readings were used, in addition to visual field observations, to select the samples for laboratory analysis fLJ;_JL GROUNDWATER ' {�TECHNOLOGY, INC