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2.6 UST Installation L In May 1994., tivo 12,000-gallon USTs and associated piping were installed at the site. The tank installation was performed by Goirrs Envirortrnental Construction of Sacramento, California. The southern tank is separated into h%,o 5,000-gallon and one 2,000-gallon sections. The tanks were installed in the same excavation from which the former USTs were removed. The stockpiled soil from the UST removal was used to backfill the eastern area of the tank excavation. The location of the new USTs are shown on Figure 2. A conductor casin was installed near the .center of the previous tank cluster during the g P g installation of the new tanks to facilitate the possible drillina, and installation of remediation wells in this area. v 3.0 PROCEDURES 3.1 Monitoring Well Purge Procedures GeoAudit recommended discontinuing-groundwater sampling from NIW-1. Analytical results front this well have consistently established that groundwater is not impacted in this «sell. Ms. Margaret Lagorio of the PHS/El-1D Verbally agreed to GeoAudit's recommendation, and only M\�1-2 and M\V-3 were sampled. _ On December 28, 1994, a 5olinst water leve! meter ,vas used to measure the depth to cyrourtdwater in the three monitoring wells (Table 1). After watef• levels were measured, PVC IP bailers were used to purge approximately 9 gallons of water from MW-2 and MW-3. Temperature, pH and conductlVity Were measured at one-gallon intervals using an lCM water analyzer. The pu-roe water was placed in DOT-approved drums and stored on-site. TABLE 1 RELATIVE GROUNDN ATER ELEVATIONS Arco Mini Mart 4511 Pacific A�,enue, Stockton, CA Relative Depth to Groundwater Relativ=e Groundwater Well Casino Elevation No. Elevation � - 3194 9194 L/94 3194 9194 12/94 MW-1 99.07 49.69 52.31 50.55 49.38 46.76 48.52 MW-2 98.02 48.91 51.53 49.76 49.11 46.49 48.26 MW-3 98.66 49.36 51.91 50.19 49.30 46.75 48.47 All meawremoils m lect G-1.1,"I Audis 5,rv—,.Inc. ARCO QR12 Nur-1.6