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1 ' • Evaluation of tidal influence on one of the new wells • Interpretation of the distribution of hydrocarbon compounds in the groundwater beneath ' the site based on analytical results of groundwater sampling 2.0 FIELD METHODOLOGY ' This section summarizes the field techniques used for monitoring well installation, well development, groundwater sampling, aquifer testing and the tidal study A more detailed ' account of field activities is presented in the Field Report, Appendix A ' 2.1 Monitoring Well Installation The five new monitoring wells were installed on the sidewalks and in city landscaping planters ' surrounding the new San Joaquin County Human Services Agency building (Figure 2) The wells were drilled using a CME 550 auger drilling ng which is a relatively small and maneuverable type of drill Each well boring was initially drilled with an eight inch diameter auger down to ' the depth of saturation ( approximately 49 to 51 feet below ground surface (bgs)) and then reamed out to a diameter of ten inches to the total well depth to accommodate the four inch diameter well casing ' A split spoon sampler was used to collect soil samples from each boring for lithologic description Because all of the new wells were located off of the original tank site, no hydrocarbons were anticipated in the soil column and consequently no soil samples were collected for chemical analysis. The first boring drilled, MW-6, was sampled every five feet in order to develop a detailed lithologic log and to find the approximate depth to groundwater ' Subsequent well borings were sampled at ten foot intervals down to groundwater then sampled at five foot intervals in the saturated zone to develop a detailed log of the aquifer sediments Lithologic logs of each well boring are presented in the Field Report, Appendix A ' The monitoring wells were constructed of four inch diameter PVC casing and screen with a sand pack around the well screen, a bentonite seal above the sand and a combination bentonite/cement ' grout emplaced from the top of the seal to the ground surface A table of monitoring well specifications is presented in the Field Report, Appendix A Monitoring well development consisted of swabbing, bailing and pumping the wells until the ' water became relatively free of sediment The amount of water purged from each well was measured and recorded in the field notes Development water was containerized in 55 gallon steel drums and stored in a nearby parking lot ' The location and elevation of the new monitoring wells (top of PVC casing and ground elevation) were surveyed by a licensed surveyor The measurements were used to create the site ' maps and to calculate the groundwater elevations in each well The well head elevations are presented in the Field Report, Appendix A avrsrsrc wr 5 ob, I mm