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PREFERRED METHOD It is our understanding that San Joaquin County will review this evaluation and issue a`, comment letter on the chosen remedial method,and that the next step will.be to prepare a more detailed work plan to install the wells'and test the method. Upgradient Environmental Consultants'believes that groundwater-extraction is preferable to in-well air stripping on most counts,especially if significant cleanup is achieved within the first year.Like most consultants,we are familiar with this method and can respond , quickly to any difficulties that may arise,adjust or modify the system,change out any pumps or other parts that may require repair,and otherwise operate and maintain the- system as often as needed. The air stripping method would require contacting the vendor in Kansas and+would likely require bringing iri a specialist from their company to service -or repair the equipment. This would likely result'in longer delays in operationand higher costs,and would not provide as timely and convenient service to Valley Motors.The number of moving parts is greater for.the stripping method,creating the potential for more things to go wrong. Hence, from an ease of operation and reliability standpoint,we favor groundwater extraction. The most significant drawback with groundwater extraction is the,cost of water disposal, but if the pre-disposal treatment is successful it may be possible to reduce the frequency . of sampling after the system begins to demonstrate success,and also obtain a reduced- disposal rate from the City of Stockton. If so,c6sts could be less than anticipated. Furthermore,the disposal cost is tied to zthe volume of discharged water,and this volume cannot be reliably estimated before conducting a pumping test.Thus,the volume and disposal rate could be higher or lower than that shown in Table 2,depending on how fast the wells can actually be pumped. It is easier to adjust the pumping rate than it is in the in-well air stripping method,'which is another advantage of groundwater extraction. 1 _