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� v 0 ASS16 OCIATES INC The Cooper-Jacob type-curve solution for an unconfined aquifer was used to estimate aquifer parameters The results are presented in Table 3 Time versus drawdown plots using the Cooper- Jacob unconfined aquifer solution for each well are presented in Appendix E The obtained results for the storage coefficient using the Cooper-Jacob solution were a little lower than expected for an unconfined aquifer The storage coefficients for unconfined aquifers are typically between 0 01 and 0 3, while those for confined aquifers are typically between 0 00005 and 0 005 (Driscoll page 210, 1986) The average storage coefficient calculated using the Cooper- Jacob solution was 0 063 Although the storage coefficients were a little lower than expected, this method was considered appropriate for the site conditions, due to the lithology of the subsurface which shows a flowing sand layer (likely a high permeability) present in the top 10 feet of the aquifer, but a lean clay and elastic silt layer (lower permeability) present in the bottom 4 feet of the aquifer The calculated storage coefficients indicate the aquifer exists in an unconfined condition The average hydraulic conductivity values (0 072 meters per second [m/s]) calculated and presented in Table 3, fall within the average range for fine to coarse sand (1 to 10' m/s) (Driscoll page 74, 1986) 334 Radius of Influence of Aquifer Test The observed maximum drawdown in each of the four observation wells was plotted against the distance of each well from well MW2 Based on the observed data, the radius of influence for groundwater extraction at the site is less than 40 feet (Figure 5) Observation wells MW 1 and MW3 are located approximately 48 5 and 43 feet, respectively from pumping well MW2 and the groundwater elevation dropped less than one-tenth of a foot in each of these wells In general, a small radius of influence is expected for pumping in an unconfined aquifer 3_5 Groundwater Samnling and Analysis Grab groundwater samples were collected from well MW2 prior to beginning the pump test and at the completion of the pump test after the groundwater elevation had been allowed to recharge Groundwater samples were transferred to appropriate sample containers, using clean, disposable ' bailers with bottom emptying devices to reduce volatilization Sample containers were then labeled with sample identification, placed on ice, and shipped under chain-of-custody to State- certified Argon Laboratories for chemical analysis of TPHg and TPHd utilizing EPA method t8015 modified, and BTEX utilizing EPA method 8020 Groundwater analytical results are summarized in Table 2, and laboratory data sheets are presented in Appendix B • w 1130991reportslsumweli doe 5