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1 Harding Lawson Associates December 20, 1994 1t6 256661 San,Joaquin County Mr Harlin Knoll Page 4 Because there is no Site B groundwater analytical data, the monitoring well for this site was installed adjacent to where the Site B UST was believed to be located The groundwater monitoring wells were installed on October 14, 1994, by Mitchell Drilling of Rancho Cordova, California Boring permits were obtained from SJCEHS prior to initiation of drilling activities The monitoring wells designated MW-A1 (Site A) and MW-B1 (Site B) were installed using hollow- stem-auger drilling techniques Monitoring well borings were drilled five to eight feet below the depth at which groundwater was first encountered. During drilling, soil samples were collected at five-foot- intervals using a split spoon sampler Samples were retained for logging purposes and logged in accordance with Unified Soils Classification System (USCS) presented on Plate 4 Soil samples were screened in the field for the presence of volatile organic vapors using a photoioruzation detector (PID) equipped with a 10 2 electron-volt lamp The PID was calibrated with an isobutylene standard Monitoring wails were constructed of schedule 40, 2-inch-diameter PVC Well screen consisted of 0 020 inch factory slotted screen Screened intervals extended from 6 to 16 feet bgs at the Site A well and from 5 to 20 feet at the Site B well The filter pack consisted of Lonestar No 3 sand and extended from the bottom of the screen to 1 foot above the top of the screen One to two feet of bentonite pellets were placed above the screened interval and the remaining space grouted to groundsurface with cement Surface completions consisted a water tight well box installed at ground surface and raised to promote drainage of surface water away from the box A representative of SJCEHS was onsite to inspect the grout and well completions as required Upon completion the wells lip were surveyed by a licensed surveyor and referenced to the existing momtonng well network datum The surveyor report is attached i The two new groundwater monitoring wells were developed and sampled on October 19, 1994 Prior to purging, the depth to water was measured in the two newly installed wells and two existing wells (WP-1 and WP-2) located at the south and north end of the facility (Plate 1) Morutoring wells MW- Al and MW-131 were purged and developed using a stainless steel bailer A minimum of eight well casing volumes were removed from the well prior to sampling Indicator parameters, pH, conductivity, and temperature were monitored and allowed to stabilize prior to sampling Groundwater samples from the bailer were decanted into laboratory supplied containers, labeled and placed in a ice chest containing ice The groundwater samples were submitted to California Analytical Laboratory Service of Rancho Cordova, California for analyses of total petroleum hydrocarbons as gasoline (TPHg) and BTEX by EPA Methods 8015 modified and 8020, respectively The groundwater sample collected from Site B was also analyzed for organic lead by the California Department of Health Services (DHS) Method ' All downhole drilling and sampling equipment were decontaminated between borings by steam cleaning Between sampling intervals, soil sampling equipment was washed in an alconox solution and rinsed with clean water Groundwater sampling equipment was decontaminated by steam cleaning prior to arrival onsite Borehole cuttings were stockpiled at the former corn refinery parking - lot Decontamination water was placed in a 55-gallon drum and stored onsite adjacent to the stockpiled soil i Fuel Oil Bunker Investigation J To assess possible impacts to soil from the bunker, HLA collected one soil sample from below each end (Plate 4) A concrete corer was utilized to drill through the bottom of the bunker at the sampling