ARCHIVED REPORTS XR0003434 - Laserfiche WebLink

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Mr Dann L Rouse Exxon Company, U S A August 4, 1999 Page 3 Between May 26 and 27, 1999, Delta geologists observed Woodward Drilling advance eight soil ' borings and complete two of them as ground water monitoring wells onsite Soil borings SB-4 through S13-9 were advanced in the vicinity of the former UST basin to depths ranging from 26 5 to 36 5 feet bsg The borings for monitoring wells MW-9 and 1AW-10 were each advanced to a depth of 26 5 feet ' bsg The locations of monitoring wells and soil borings are shown in Figure 2 Each boring location was sampled and logged at a minimum vertical interval of five feet Sol] samples collected in the field were logged according to ASTM 2488-84 Unified Soil Classification System, visual manual method ' Additionally, each sample was screened in the field for the presence of petroleum hydrocarbon vapors using a Photoionization Detector(PID) Soil boring logs were prepared for each boring and are included as Enclosure C The boring logs included descriptions of soil types encountered, PID readings and methods used to advance and maintain the borings All ,oil samples collected were submitted to Sequoia Analytical (a Cali tom ia-certified laboratory) in Redwood City, California for analysis of benzene, toluene, ethylbenzene, and total xylenes (BTEX) ' using EPA Method 8020, total purgeable petroleum hydrocarbons (TPPH) as gasoline using EPA Method 8015 Modified, and methyl tertiary butyl ether(MTBE)using EPA Method 8260 Selected soil tramples were additionally analyzed for fuel oxygenates tertiary amyl methyl ether, tertiary butyl ' alcohol, di-isopropyl ether, 1,2-dibromoethane, 1,2-dichloroethane, ethanol, ethyl tertiary butyl ether, and MT BE by EPA Method 8260B 1bSoil Sample Analytical Results Soil samples collected from the boring for MW-9 were below the laboratory's reporting limits for all ' analyte , Samples from the soil boring for MW-10 were below the laboratory's limits for all analytes with the exception of MTBE reported at 0 018 milligrams per kilogram (mg/kg) in the soil sample collected at 16 5 feet bsg Benzene was detected in samples identified as SB-5-16 5 and SB-5-26 5 at ' 0 0831 mg/kg and 0 00367 mg/kg, respectively Detectable concentrations of TPPH as gasoline were reported in soil samples collected from the borings for SB-4, SB-5, S13-8, and SB-9 at concentrations ranging from 0 864 mg/kg (SB-4-11 5) to 797 mg/kg (SB-9-11 5) MTBE was reported in soil samples ' collected from borings for SB4 through SB-8 at concentrations ranging from 0 0056 mg/kg (SB-6-31 5) to 0 863 mg/kg(SB-4-16 5) Cumulative soil sample analytical results from drilling events by Delta are summarized in Table 1 Copies of the laboratory analytical reports with chain-of-custody documentation for the current drilling event are included in Enclosure C Well Construction Development,Measurements and Sam lin ' Groundwater monitoring wells MW-9 and MW-10 were each installed to a depth of 20 feet bsg Each well was constructed of 2-inch diameter flush threaded Schedule 40 PVC casing and screened with ' 0 010 machine slotted casing The screen interval begins at 5 feet bsg and extends to 20 feet bsg The annular space of each well was filled with No 2112 Lonestar sand from the total depth drilled to 6 inches above the top of the screen interval and a 1 foot bentonite seal was emplaced above the filter ' pack The remaining annulus was filled with a cement grout containing approximately 1-percent bentonite to within six inches of surface grade Monitoring wells MW-9 and MW-10 were completed at the surface with a flush grade 8-inch diameter traffic-rated well box set in concrete dyed to match the existing asphalt surface Well construction details are illustrated in Enclosure D