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w Of_ 40 ._t' h, mm �� ai.,,�y,� _s .+�. .. '� �- x s �'Ir. Chuck Carmel July 11. 1991 Page 'r Ret.'ediation ,Schedule The groundwater extraction system h;u been operating at this site intermittently since mid-1984 and run continuously hctween April 1984 and March .1987. Due to modifications to the system, for both compliance and operational reasons,t:ie system was not operated full-time after March 1987• The system is now on-line and has been in full operation since June 5, I99I,pumping an average of 10.8 gallnns per minute(gpm), i lie effluent from the separator tank is sampled twice each month to monitor the hydrocarbon constituents and metals concentration. The system will remain ill full operation unless the tested constituents are found to be out of compliance based Or the analytical results of the effluent samples. The extraction process will be continued until the regulatory agencies determine that the hydrocarbon constituent concentrations found in groundwater samples from the groundwater monitoring wells have beer reduced sufficiently. ne hydrocarbon concentrations in the monitoring wells will continue to be monitored on a quarterly basis. An estimated schedule for reducing the hydrocarbon concentrations sufficiently W complete the groundwater remediation can possibly be determined after two to three quarters of sampling with the extraction system in operation. Pumping Test and Zero Line Definition As stated above,a step-drawdown pumping test was performed on the groundwater recovery well in August 1990. This section presents the results of this pumping test includIng a modeling analysis that was used to estimate a pumping rate which should be sufficient to continue to control .he hydrocarbon plume found beneath the site. The recovery well at the site(R-13)was pumped for 6 hours at variable rates and the flow rate and water level changes in the well were measured. The flow rates were mea_mtrd by reading the pump's flow meter and recording the total gallons pumped at predetermined time increments. Flow was adjusted using a gate valve. A digital stop watch was used to track tinme. Numerous flow readings were taken throughout the test to control the flow rate. Water levels were recorded using an electronic sounder and a pressure transducer controlled by a data logger (In-Situ Hermit). The data were subsequently downloaded to a portable field computer. The data recorded during the test are provided in Appendix C. The test consisted of three pumping steps plus water-level recovery. Figure 5 shows the test data in graphical form. Each pumping step lasted for 2 hours. During the first step, the average pumping rate was about 6.1 gpm. The flow rate was increased to 10.2 gpm for the second step, and subsequently increased again to 12.3 gpm for the third step. Less than 1.5 ft of drawdown occurred in the we'.1 during the entire test. Initial plans for the test had included a maximum 20- gpm flow rate. However, back pressure on the pump resulted in a maximum attainable rate of �- about 12.5 gpm. Brown and Caldwell �t