SITE INFORMATION AND CORRESPONDENCE_FILE 3

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San Joaquin County OPO.0 IN,.0 Environmental Health Department DIRECTOR r. 2 1868 East Hazelton Avenue Donna Heran,REHS N: r � Stockton, California 95205-6232 PROGRAM COORDINATORS .,.i Robert McClellon, REHS Jeff Carruesco,REHS,RDI Website: Www.SJ9OV-Or91ehd Kasey Foley, REHS Phone: (209)468.3420 Linda Turkatte, REHS Fax: (209)464-0138 Rodney Estrada, REHS Adrienne Ellsaesser, REHS June 11, 2014 Mr. Paul Zumberge and Ms. Daren Zumberge Frontier Transportation, Incorporated 3577 West Philadelphia Chino Hills, California 91710 Subject: Frontier Transportation, Incorporated 425 Larch Road Tracy, California 95376 Dear Mr. Paul and Ms. Daren Zumberge: The San Joaquin County Environmental Health Department (EHD) has received and reviewed Revised Work Plan for Groundwater Remediation (revised work plan), dated 16 May 2014, prepared and submitted by your consulting firm, EnviroMonitoring Services, Inc. (EMS), on your behalf for the above-referenced site. By letter dated 20 March 2014, the EHD had approved the destruction of dual-phase extraction wells: DPE-4, DPE-5, DPE-7, DPE-9, DPE-10 and monitoring well MW-3R in addition to monitoring wells MW-6, MW-7, MW-10 through MW-12, and MW-14 through MW-16, previously approved by the EHD by letter dated 18 July 2013, and had directed a work plan be submitted to this agency to destroy these wells. In the revised work plan, EMS proposes to use eight-inch augers to over-drill MW-3R, MW-14 through MW-16, DPE4, DPE5, DPE7, DPE9 and DPE10 to total depth of each well; then seal the cleared borehole with neat cement grout from the bottom upward to the depth of three to five feet below surface grade (bsg) using a tremie pipe. EMS proposes to destroy MW-6, MW-7 and MW-10 through MW-12 by applying approximately 25 pounds per square inch (psi) of liquid grout pressure for ten minutes using a tremie pipe, prior to drilling out the top approximately three feet of the well with a two-foot diameter auger. Then EMS proposes to remove an additional six inches of soil below the new (top) of the cut-off casing before allowing the grout sealant to spill out of the top of the casing and form a twelve-inch-thick "mushroom cap" seal with six-inches below and six-inches above the top of the cut-off casing. The EHD approves the well destructions as proposed in the revised work plan. Although the revised work plan included most of what was proposed in Proposed Work Plan for Groundwater Remediation, dated 04 February 2014, and approved by the EHD by letter dated 20 March 2014, the revised work plan did state that before construction of the extraction wells, a continuous soil sample will be collected from six feet (instead of five feet) to sixteen feet bsg for field observation. The EHD approves this revision.