ARCHIVED REPORTS_XR0009752 - Laserfiche WebLink

Home Browse Search

t v 1� r A S S O C I A T E S I N C measured during the test were recorded by transducers and are contained in Appendix B with the AQTESOLVTm input data The aquifer thickness was assumed to be an average of 1198 feet, based ' on approximate length of the water column in the wells The Theis type-curve solution for a confined aquifer was used to estimate aquifer parameters The ' results are presented in Table 2 The calculated storage coefficients indicate the aquifer exists in an unconfined condition 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 Theis solution was 0 2983 The average hydraulic conductivity value (7 353 x 10-6 meters per second [m/s], or 0 6353 meters per day) ' calculated and presented in Table 2, falls at one end of the average range for fine to coarse sand (1 to 10"5 m/s) (Driscoll page 74, 1986) Time versus drawdown plots for each well are presented in Appendix C 3.4 Groundwater SampIinQ and Analysis Grab groundwater samples were collected from well MW-3 prior to beginning the pump test ' (MW3-1), after 24 hours (MW3-2), and at the completion of the pump test after the groundwater elevation had been allowed to recharge (MW3-3) 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 in an ice-chilled cooler, and shipped under chain-of-custody to State-certified Argon Laboratories for chemical analysis of TPHg, BTEX, and MTBE by EPA methods 8015/8020 Groundwater analytical results are summarized in Table 3, and laboratory data sheets are presented in Appendix D 3.5 Results of Groundwater Pumping Test The observed maximum drawdown in each of the observation wells was plotted against the distance of each well from well MW-3 (Figure 4) Based on ATC's experience at groundwater remediation sites, the radius of influence is typically the point where the drawdown in the observation ' well is at least 0 10 feet The maximum drawdown in well MW-1 was 0 13 feet which yields a radius of influence (ROI) for groundwater extraction at the site of approximately 85 feet (Figure 5) Laboratory results of the groundwater samples indicated that TPHg and benzene, toluene, ethyl- benzene, and xylenes (BTEX) were detected in the samples collected from MW-3 before, at 24- hours, and after the pump test Assuming 15,900 gallons of groundwater was extracted from MW-3, as stated in Section 3 2, and average concentrations of TPHg and benzene from the ' beginning, after 24 hours, and ending pump test samples, approximately 2 90 pounds of TPHg and 0 005 pounds of benzene were removed during the groundwater extraction pilot test as shown in the following equations S 1Env�ronmenta11626051reportslpump_test doc 4