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Table 1-1 2005 Sampling Schedule San Joaquin County Human Services Agency 7Quarter I Monitoring Wells to be Sampled First MW-2,MW-2A and MW-9 ' Second MW-2,MW-2A,MW-3A,1%4W-4,MW-6,MW-7 and MW-9 Third MW-2,MW-2A and MW-9 ' Fourth MW-2,MW-2A,MW-3A,MW-4,MW-5,MW-6,MW-7,and MW-9 2.0 FIELD SAMPLING SUMMARY Groundwater samples were collected from monitoring wells MW-2,MW-2A,MW-3A,MW-4,MW-6,MW- 7, and MW-9 (Figure 1-1) on June 29 and 30, 2005 Groundwater sampling field data sheets for the monitoring wells are presented in Appendix B In addition,an equipment blank water sample and purge water discharge samples were 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 for total petroleum hydrocarbons as gasoline (TPH-g) analysis by United States Environmental Protection Agency (EPA) Method 801513/802113 The groundwater sample is transferred from the disposable bailer into 40-milliliter(mL)glass sample containers 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 form for delivery to the analytical laboratory Groundwater sample analyses are perfonned 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 and washing the outside of the pump Dedicated purge tubing is used for each well An equipment blank water sample is then collected by pouring laboratory-grade deionized ' water over and through the pump into 40-mL glass sample containers 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 monitonng well would 2