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L3 Pumping from New Extraction Well XW-1 An extraction well XW-1 will be constricted near MW-6, approximately 50-100 feet to the west of the existing MW-6, and located so as to minimize impact to the existing orchard. The extraction well will be designed according to Figure 4. The well will be drilled by a licensed well drilling contractor according to state regulations. Samples of aquifer material from the well will be collected every five feet below the water table and particle size analyses will be performed on at least three of the samples. The sandpack and screen slot size will be specified after results of the geologic logging and particle size analysis are available. T1iese materials will be chosen so as to maximize efficiency of the well. '11le well will be constructed and completed with a surface seal of at least 50 feet depth. 77ie necessary piping and electrical connections will be installed to the XW-1 site and pumping will commence at a rate of 20 gpm. Water will be transported back to the former rinsewater pond for treatment as described below. 3.4 'I3ie effect of pumping_on downgradient monitoring well MW-7 The model simulation shown in Figure 5 predicts that pumping from XW-t will contain the plume by creating a capture zone in the groundwater table that will enclose MW-7. The model predicts that the capture zone will have reached 300 feet beyond MW7 within a year. The effects of pumping should cause chloroform concentrations in MW-7 to return to background. It cannot be known at this time, when this will happen because actual pumping response may vary. Quarterly monitoring of MW-7 will continue, and decreases in chloroform concentrations after pumping has begun will be an indication that pumping is effective at containing the plume. 4. Disposal of Extracted Groundwater Water pumped from MW-4A and XW-1 will be aerated in the old rinse water pond and recirculated into the aquifer to provide oxygen to the bioremediation program. Water from XW-I will increase by four fold the amount of water returning to the pond (presently only water from MW-4A is aerated). As shown in Figure 5, the pumping activity at MW4-A and XW-I should recapture any water introduced through the pond. A Report of Waste Discharge (Appendix F) has been filed to document the ongoing practice of recirculating aquifer water from MW-4A through the pond and to prepare WDR for the additional quantities of water from pumping XW- 1. 'llic water being returned to the aquifer through the aeration pond is not only richer in oxygen, but it is also lower in chloroform than the groundwater being extracted. Sampling of pond water performed in May of 1994 indicated that water flowing into the pond from MW-4A contained 375 ug/l chloroform, whereas water from the surface of the pond which had passed through the aerator system contained only 32 ug/I chloroform. Venting of chloroform to the air in this manner L-a 1 1 CONDOR