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2.0 FIELD SAMPLING SUMMARY Groundwater samples were collected from monitoring wells MW-2, MW-2A, and MW-9 (Figure 1-1)on September 29, 2005 Groundwater sampling field data sheets for the monitoring wells are presented in Appendix B In addition,an equipment blank water sample was collected and submitted for analysis Prior to well purging, water levels are measured in all wells to collect data for potentiometnc contouring The standing water volumes within wells scheduled for sampling are calculated using water levels measured in each well at the time of sampling and total well depths A submersible pump attached to a dedicated discharge tube is then lowered into the well and used to purge three well casing volumes from each of the monitoring wells ' The temperature, pH, specific conductance, dissolved oxygen, turbidity, and oxygen reduction potential of the purge water are measured initially and during the purge process and recorded on a sampling data sheet The pump is then removed and a disposable bailer is lowered into the well for ' the collection of groundwater samples for benzene,toluene,ethylbenzene,and total xylene(BTEX) and total petroleum hydrocarbons as gasoline (TPH-g) analysis by United States Environmental Protection Agency(EPA) Method 8015B/8021 B The groundwater sample is transferred from the ' disposable bailer into 40-millihtcr (mL) glass sample containers pre-preserved with hydrochloric acid(HCl) Sample containers containing air bubbles are discarded and recollected Samples are then sealed in a plastic bag, placed with ice in an insulated chest, and logged on a chain of custody i form for delivery to the analytical laboratory Groundwater sample analyses are performed by Sequoia Analytical Laboratory in Sacramento, California The pump used to purge the wells is thoroughly cleaned prior to each use by placing it into a container of tap water with non-phosphate detergent, washing the outside of the pump,and running ' the soapy water through the pump The pump is then rinsed with clean tap water Dedicated purge tubing is used for each well An equipment blank water sample is then collected by pouring laboratory-grade deiomzed water over and through the pump into 40-mL glass sample containers ' pre-preserved with HCl The sampling procedure and analysis then follows that described above to ensure thorough decontamination practices Purge water from monitoring wells MW-2 and MW-2A has historically been stored in 55-gallon � drums staged at the loading dock of the San Joaquin Human Services Agency building at 145 South Sutter Street This water meets the requirements for transfer and disposal at a licensed treatment ' facility Due to a drop in contaminant levels in MW-2A,WESTON ascertained that the purge water from this monitoring well would meet discharge permit requirements for discharge to the sanitary ' sewer As stated in the existing discharge permit application, pending laboratory analysis of the purge water from these two monitoring wells would determine appropriate disposal As a result of these investigations and laboratory analysis, purge water from monitoring well MW-2A is now ' stored in the 500-gallon holding tank as described below Purge water from monitoring well MW-2 will continue to be stored in a staged 55-gallon drum for eventual transfer and disposal to a licensed treatment facility. 4