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_ u :pi -2`.n ..t� f a?_' V- ME Mr- fir. Chuck Cm-mel July 11, 1991 Page 4 in well R-13 would operate periodically for short periods of time. The hydrograph patterns are consistent for most of the wells. Some wells, however.appear to respond more dramatically to pumping from R-13 than others. Although R-13 has been i_r+tertnittcntly operated for the past two years, the water-level contour maps presented in Brown and Caldwell's quarterly monitoring reports for the site reveal a consistent pattern. The pattern is also consistent with earlier reports by Emcon Associates and also agrees with consultants'reports regarding a r_hevron station located cross gradient from the subject site. Figure 3 shows the groundwater, contour lines and flow direction based on measurements collected on February 11, 1991. Flow is predominantly to the northeast. The average gradient across the site is about 0.002. This pattern and magnitude of gradient has been observed in each seasc;n over the past several years, It is anticipated that the general groundwater flow direction and gradient will remain in a northeasterly direction. However,the groundwater flow pattern will be altered locally by the groundwater extraction system. Remedial Activity Details This section describes the groundwater extraction system and how it functions. Figure 4 is a - schematic diagram of the system components. The groundwater pump and treat system consists of one 12-inch extraction well. and one submersible pump capable of pumping approximately 12 gallons per minute. Groundwater is pumped into a free product separation tank, then discharged to the sanitary sewer. Discharge flow is by gravity from the tank overflow to the sewer. Two LEL meters are used; one is located in the well vault, and one is located at the discharge of the separation tank. Flow is measured at the pump discharge with a mechanical totalizing flow meter and all electronic flow indicator and recorder. A float switch placed in a"tee" at the sewer lateral will shut the system down if the sanitary sewer backs up. Another float switch on the product separation tank will shut the system down if the water level in the tank exceeds a set level. Sample ports we located at the pump discharge and at the separator tank overflow. The overall system status (LEL readings,flow rate,rain gauge, and status of the float switches) is recorded by a data logger. The system components can be monitored and controlled with a computer from any telephone by means of a telephone modem connected to the data logger and a telephone line. Brown and Caldwell �„liCSLLSif1'S