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1 QUARTERLY MONITORING REPORT APRIL 1997 CANEPA S CAR WASH 6230 Paclfi0 Avenue Stockton CA April 17 1997 ' 3 0 QUARTERLY GROUNDWATER MONITORING - APRIL, 1997 The work conducted during the quarterly groundwater monitoring was outlined by Condor in ' Proposal for Site Evaluation and Groundwater Monitoring (April 8, 1996) The scope-of-work presented in the proposal was approved by Mr Ronald Rowe of the PHS/EHD Ori April 1 and 2, 1997, Condor personnel made field observations and collected groundwater samples from the eight (8) monitor wells at the site (see Figure 2, Appendix A for well locations) In addition, at the request of Mr Rowe, a groundwater sample was also collected from soil vapor extraction well SV-9 The order of sampling was MW-5, MW-4, MW-8, MW-6, MW-7, MW-3, MW- 2, SV-9, and MW-I All field equipment was decontaminated in the field with a solution of laboratory-grade, non-phosphate detergent and hydrocarbon-free water and rinsed with hydrocarbon- free water prior to use in each well All field instruments were calibrated to the manufacturer's Irecommended standards The water level in each well was measured to the nearest 0 01 foot with a standard battery-operated, flat-tape, water-level meter A new, disposable, polyethylene bailer was lowered Into each well to collect a field-Inspection sample The bailer sample was Inspected for floating product, sheen, discoloration and/or odor Floating product was not observed In any of the monitor wells during the groundwater sampling However, water levels in the wells were above the top of the well screens in the wells A slight petroleum odor was detected in MW-I and SV-9 Each well was purged with a dedicated bailer until at least three well-casing volumes of water were removed and until the pH, specific conductance, and temperature of the water had stabilized Groundwater Monitoring Field Forms are included in Appendix B Prior to sampling, the water was allowed to recover to at least 80%, of the pre-purge water level The purge water was discharged to 55-gallon drums and left on site to await disposal For each well • A groundwater sample was collected with a disposable, one-time-use polyethylene bailer The sample was transferred to two (2) 40-m1 glass VOA vials fitted with Teflon-lined caps Each vial was inverted and tapped to assure that no air bubbles wei e present IEach vial was labeled and placed in a cooler chilled with ice and delivered under chain-of-custody procedures to GeoAnalytical Laboratories, Inc , in Modesto, I California, within 24 hours of sample collection The results of laboratory analyses are discussed in Section 4 2 40 i iT7 LCy A A%JtiTIV l T3 Ir S1 L 1 0 4 1 Laboratory Analyses The groundwater samples were analyzed for total petroleum hydrocarbons, quantified as gasoline (TPH-G) by Method 50311LUFT and for benzene, toluene, ethyl benzene, and xylene (BTEX) and methyl tertiary butyl ether (MTBE) b} EPA Method 602 MTBE was detected by EPA Method 602 and confirmed by EPA Method 8260 in sorne of the groundwater samples collected during the 6 August 1996 monitoring event Because of this August, 1996, background data, the presence of Page -2- q0 CONDOR