SITE INFORMATION AND CORRESPONDENCE_FILE 2

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U-Haul #709-50 page 2 2701 N. Wilson Way, Stockton. Please be advised that monitoring wells with screened intervals greater than 20- feet in length are no longer approved. A monitoring well with a 20 feet well screen should be placed in the "C" casing interval to further investigate the lateral extent of the groundwater contamination found in MW-8C. EHD cannot state that the proposal to place MW-13's deeper screened interval from 130 to 150 feet bgs is adequate and necessary since there is no existing data to show that the screen should be placed in that interval. Until there is data to justify that screened interval, EHD will not approve the placement of that well casing. After the CPT work has been completed there may be justification for a well screened in that interval. The work plan proposes MW-14 "A" and "D" be constructed the same as MW-13 "A" and "D" and that it be placed south of Frontier Motel, approximately 250 feet south and down gradient of the closest U-Haul monitoring wells, MW-9 and MW- 10. Installation of a monitoring well with a 20 feet screen in the "B" casing interval may provide definition in this direction and will be approved as adequate and necessary. EHD will not approve the placement of a well screen from 130 to 150 feet bgs in this area either at this time. The work plan provides for no investigation in the area between the impacted Frontier Motel well and MW-913 and MW-10C. EHD considers the work plan to be inadequate by not investigating this area and recommends that U-Haul utilize this mobilization to investigate this area so that the data gaps currently existing in your reports can be completed. Please be advised that drillers have experienced difficulty with heaving sands and other construction problems when installing 'nested' wells deep into the saturated zone (-90 feet). "Nested" wells may also be more costly to install due to the extra installation time needed as well as the special sealing materials (coated bentonite) required. "Nested" wells are also more difficult and costly to destroy as is required once the well no longer serves a purpose. EHD will only approve nested well installations after U-Haul provides information that installation of "nested" wells instead of clustered wells is necessary and cost effective and provides assurance that they will be properly constructed and destructed. EHD has not directed nor required soil or ground water samples for this site to be analyzed by EPA Method 8310 (PAHs). Without EHD directives for such analyses, the costs incurred by U-Haul may not be reimbursed by the State Water Resources Control Board (SWRCB) Clean Up Fund. In addition to the proposed analyses for the soil samples, EHD will require selected soil samples to be analyzed for methanol (EPA 8015m) and ethanol (EPA 8260B).