ARCHIVED REPORTS_XR0005906 - Laserfiche WebLink

Home Browse Search

' A letter from the San 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 23 Initial Investigation ' On April 27 and 28, 1994, eight soil borings were drilled at the site Three of the bonngs were completed as 2-inch groundwater monitoring wells Soil samples were collected at five- foot intervals during dnlling A total of fourteen soil samples were submitted to a state- certified laboratory for analysis Total petroleum hydrocarbons (TPH as gasoline) were detected in ten samples at concentrations as great as 3 800 ppm (134-20), TPH as diesel was detected in twelve samples at concentrations as great as 9,000 ppm (138-20) During drilling, ' groundwater was encountered at a depth of approximately 20 feet After installation, groundwater depth was measured and samples were collected from each well The hydraulic gradient was calculated to be 0 0006 ft/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 6,900 ppb, respectively Analytical results of all groundwater samples are included in Table 2 3.0 PROCEDURES ' 3.1 Monitoring Well Purge Procedures procedures were performed at the referenced site ' On May 6, 1994, groundwater monitoring p The depth to groundwater was measured in each well relative 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 was 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 Analyzer Model #52200 The purge water was stored on-site in 55-gallon DOT-approved drums 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 Miter amber bottles C-1.8-1 Add U. 4 Wpoa r,e,Seng Qwre%Ml -s