SITE INFORMATION AND CORRESPONDENCE_FILE 2

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• • San Joaquin County Environmental Health Department DIRECTOR Donna Heran,REHS 1868 East Hazelton Avenue H: Stockton, California 95205-6232 PROGRAM COORDINATORS Robert McClellan,REHS Jeff Carruesco, REHS,RDI C��iFOR i�`P Website: www.sjgov.org/ehd Kasey Foley,REHS Phone: (209)468-3420 Linda Turkatte,REHS Rodney Estrada,REHS Fax: (209) 464-0138 Adrienne Ellsaesser,REHS May 2, 2013 Nicole Arceneaux Chevron Environmental Management Company 6101 Bollinger Canyon Road, Room 5303 San Ramon, CA 94583 Subject: Former UNOCAL#6981 4707 Pacific Avenue Stockton, CA The San Joaquin County Environmental Health Department (EHD) has received a No Further Action Required Concurrence letter from the Central Valley Regional Water Quality Control Board (CVRWQCB) dated April 30, 2013 for the above subject site. It is now necessary to plan the destruction of all wells installed as part of your site investigation and remedial action, as the EHD will not issue a Case Closure Letter for this site until the wells have been properly destroyed and all onsite waste material have been removed and properly disposed of. The wells are to be destroyed within 90 days of the date of this letter. Please submit a work plan that details the conditions and construction of the wells and the methods and materials to be used to destroy them. To be issued a well destruction permit the proposal must comply with the San Joaquin County Well Standards requirements, including: • Wells that have laboratory data from the last groundwater sampling event that demonstrate the presence of any contaminants of concern are to be destroyed by removing all the contents of the original borehole (conductor casing, well casing, screen, filter pack, grout sealant); the cleared borehole is then to be sealed with neat cement by grouting from the bottom up to a depth of three feet below grade. • All wells with unknown construction and/or located in an area of known contamination are to be destroyed by removing all the contents of the original borehole as described above; the cleared borehole is then to be sealed with neat cement by grouting from the bottom up to a depth of three feet below grade. • Wells that have laboratory data from the last sampling event that report non-detectable concentrations of contaminants of concern, with acceptable laboratory detection limits, may be destroyed by pressure grouting with neat cement from the bottom up while leaving the well casing in place. Following that, a hole at least one foot larger in diameter than the originally drilled borehole shall be excavated around the outside of the well casing to a depth of 3 feet below the ground surface, and the well casing shall then