SITE INFORMATION AND CORRESPONDENCE_FILE 2

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Page 2 of 3 Avenue Former Unocal February 24, 2014 437 East Miner Avenue Stockton, CA 95202 Please submit a work plan proposal that details the condition and construction of the wells and methods and materials to be used to destroy them. To be issued a well destruction permit, the proposal must address the concerns of the EHD and the San Joaquin County Well Standards requirements, such as: • Wells that have laboratory data from the last sampling event that demonstrate the presence of any contaminants of concern remaining in groundwater are to be destroyed by removing all the contents of the well [well casing (except steel conductor casing), screen, filter pack, grout sealant]; the cleared borehole is then to be sealed with neat cement from the bottom upward to the depth of three to five feet below grade. • All wells with unknown construction and/or located in an area of known or suspected contamination are to be destroyed by removing all the contents of the well [well casing (except steel conductor casing), screen, filter pack, grout sealant]; the cleared borehole is then to be sealed with neat cement from the bottom upward to the depth of three to five feet below grade. • Wells that have laboratory data from the last groundwater sampling event that report non- detectable concentrations of contaminants of concern and with acceptable laboratory detection limits, and are not in areas of known or suspected soil contamination, may be destroyed by pressure grouting form the bottom upward, while leaving the well casing in place. The top three feet or more of the well shall be drilled out with an auger that is at least one foot larger in diameter than the auger originally utilized to install the well, and the soil around the cut-off casing removed to the depth of an additional six inches below the new 'top' of the cut-off casing. The grout sealant shall spill out of the top of the well casing to form a mushroom cap seal with at least twelve inches of neat cement grout poured six inches above and six inches below the top of the cut-off casing. • All groundwater displaced to the surface during grout installation shall be pumped out of the excavation to allow for EHD inspection and verification that the well has been properly destroyed. Contaminated groundwater pumped out of the excavation shall be containerized for proper disposal. • EHD records indicate the presence of 'nested' wells installed using ten-inch diameter augers. The EHD has found destruction results of nested wells are best obtained when augers larger in diameter than the original augers are used and centered on the deepest casing (which is off-center in the original borehole). The augers need to be sized sufficiently to reach out and remove all well casings, screens, filter packs and grout sealant installed during construction. • This site has wells located off-site in the City of Stockton right-of-way. Please submit a copy of a valid encroachment permit when submitting the EHD Well and Boring Permit Application form for these wells. • This site has wells located on an adjacent parcel. Please submit a copy of a valid access agreement when submitting the EHD Well and Boring Permit Application form for these wells.