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<br /> interval in the B zone and C zone wells were five feet in length. The screen slot size is 0.020-
<br /> inch and the wells were surge blocked to ensure an adequate sand pack was in place. Well
<br /> construction details are depicted on the well logs contained in Appendix A.
<br /> 22.4 Monitoring Well Development
<br /> ' Groundwater monitoring wells MW7c, MW8, MW9a, MW9b, and MW9c were developed on
<br /> March 17, 2004. Groundwater monitoring wells MW6c, MW10a, MW10b, and MW10c were
<br /> ' developed on April 21, 2004. Each well was purged until the extracted water was relatively
<br /> sediment free. Development logs are included in Appendix D. Purgewater was temporarily
<br /> stored on site in 55-gallon drums prior to disposal by Excell Excavating. Development logs for
<br /> ' MW6c, MW10a, MW10b, and MW10c were submitted in Monitoring Report Second Quarter
<br /> 2004, Jamar Service Station, 4075 East Main Street, Stockton, California.
<br /> ' 2.5 Groundwater Sampling and Analyses
<br /> ' On March 17, 2004, ATC personnel collected groundwater samples from MW1 through MW5,
<br /> MW6a, MW6b, MW7a, MW7b, MW7c, MW8, MW9a, MW9b, MW9c, and EWL On March
<br /> 16, 2004 fluid levels in the wells were measured utilizing an electronic water probe capable of
<br /> measuring with an accuracy of 11100 of a foot. Groundwater elevation data are presented in
<br /> Table 3. The samples were collected after purging a minimum of three well volumes and
<br /> stabilization of electric conductivity, pH, and temperature. Turbidity was visually observed and
<br /> recorded. Subsequent to purging, groundwater was sampled and transferred to appropriate
<br /> sample containers, using clean, disposable bailers with bottom emptying devices to reduce
<br /> volatilization. After samples were collected, dissolved oxygen (DO) concentrations were
<br /> measured.
<br /> On June 3, 2004, ATC personnel collected groundwater samples from monitoring wells MW 1
<br /> ' through MW5, MW6a, MW6b, MW6c, MW7a, MW7b, MW7c, MW8, MW9a, MW9b, MW9c,
<br /> MW10a, MW10b, MW10c, and EW1. Prior to collection of groundwater samples, the depth to
<br /> water, pH, electrical conductivity, and temperature were measured in groundwater purged from
<br /> ' the monitoring wells and recorded. Turbidity was visually observed and recorded. A minimum
<br /> of three well casing volumes were purged from each monitoring well prior to sampling. The
<br /> wells were allowed to recover and samples were collected from each well using disposable
<br /> polyethylene bailers. After samples were collected, dissolved oxygen (DO) concentrations were
<br /> measured.
<br /> Groundwatersamples were placed on ice and delivered under chain-of-custody documentation to_
<br /> y
<br /> Argon Laboratories for chemical analysis. Groundwater samples were analyzed for TPHg and
<br /> TPHd by EPA Method 8015B; BTEX by EPA Method 8021B; and MTBE, TAME, TBA, ETBE,
<br /> DIPE, 1,2-DCA, and EDB by EPA Method 8260. The analytical results for groundwater samples
<br /> are summarized in Table 4.
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