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7-Eleven/Stockton 4 August 19n9 1986, five additional monitoring wells were installed (MW-5, MW- 6, MW-7, MW-8, and AW-9) , and sampling of the monitoring wells and nearby domestic wells was initiated. These preliminary � hydrogeologic investigations identified gasoline hydrocarbons adsorbed within the vadose-zone soil, dissolved within the groundwater, concentrated as separate-phase hydrocarbons (SPH) , and volatilized as vapors. The discovery of SPH within MW-1 and MW-4 prompted the :initiation of a groundwater remediation/abatement program. Initial work involved periodic hand bailing of SPH as requested by the San Joaquin Local Health District. In early July 1986, a ~ small-diameter, double-pumping system was installed in MW-4 to control the continued migration of SPH and to collect SPH from the well. In an attempt to obtain increased control on the SPH and dissolved-phase hydrocarbon plumes beneath the site, three recovery wells (PW-1, PW-2, PW-3) were installed between October .v and November, 1986. A deeper, 12-inch-diameter recovery well (PW-3) was installed on-site to replace the small-diameter monitoring well MW-4, which had been used in the interim as an M on-site recovery well. A 4-inch-diameter recovery well (PW-1) was also installed on the periphery of the cite between MW-9 and the domestic well at 9135 Connie Avenue. Recovery wel1 .PW 1 was installed to prevent the migration of dissolved hydrocarbons in domestic well 9135. Another 4-inch-diameter recovery well, PW-2, was installed downgradient and off site between domestic well _ 8968 and the previously installed 14W-8. This pumping well was installed in the event that it would be needed to prevent the migration of dissolved hydrocarbons toward domestic well 8968. PW-2 has never been used as a pumping well. -- �a GH� I�1�5511k k