SITE INFORMATION AND CORRESPONDENCE

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}�, L A letter from the Sane Joaquin County Public Health Services - Environmental Health Division (PHS/EHD) dated March 7, 1994, stated that ",the former underground storage tank(s) cannot be recommended for final closure without further investigation to determine the full.extent of the soil and/or groundwater problem." In response to the letter from the PHS/EHD, GeoAudit was retained to assess soil and groundwater conditions at the site. 2.3 Initial Investigation I On April 27 and 28, 1994, eight soil borings were drilled �at they site. Three of the borings were completed as 2-inch groundwater monitoring wells. Soil samples were collected at five- foot intervals during drilling. A total of fourteen soil sampies were submitted to a state- certified laboratory for analysis. Total petroleum hydro4rbons (TPH as gasoline) were detected in ten samples at concentrations as great as 3,8001ppm (134-20); TPH as diesel was detected in twelve samples at concentrations as great as 9,000 pphi'(138-20). During drilling, L groundwater was encountered at a depth of approximately 20 feet.- i ; After installation, groundwater depth was measured and samples were collected from each L well. The hydraulic gradient was calculated to be 0.0006 Ift/ft, directed S 40° W. TPH as gasoline was detected in MW1, MW2 and MW3 at concentrations of 1,700 µg/L (ppb), 14,000 ppb and 2,600 ppb, respectively; TPH as diesel was detected in MW1, MW2 and MW3 at concentrations of 2,400 ppb, 9,200 ppb and 6,9aD0 ppb, respectively. Analytical results of all groundwater samples are included in Table �. y 3.0 PROCEDURES � 1 L 3.1 Monitoring Well Purge Procedures .I On August 5, 1994, groundwater monitoring procedures were performed at the referenced site. The depth to groundwater was measured in each well relati,a to the top of the casing using a Solinst water level meter (Table 1). The relative groundwater elevations and hydraulic gradient were calculated from these data. After water levels were measured, a 2-stage purge pump .I as used to purge each well of approximately 7 gallons of water to stabilize temperature, pH, and conductivity (Appendix A). Measurements were obtained using an ICM Water Analyzer1V1ode1 #52200. The purge water was stored on-site in 55-gallon DOT-approved drums.I.After,purging each well, a water sample was collected from each well using a new disposable plastic bailer. The samples were collected in 40-m1 EPA vials and Niter amber bottles. 1 Rip"P- r k �_QRS/A.91/92i-5 'i i ,3