SITE INFORMATION AND CORRESPONDENCE_CASE 2

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. i • Sierra Lumber Manufacturers, Inc. (Case No. 2) Page 2 of 2 375 West Hazelton Avenue July 25, 2014 Stockton, California 95203 In Groundwater Monitoring Report — Fourth Quarter 2013, dated 10 February 2014, AGE has recommended the following: • Monitor and sample monitoring wells MW-12 and MW-13 bi-annually instead of semi- annually; • Monitor DPE-1 and DPE-2 monthly to evaluate remediation cleanup progress; • Incorporate MW-15 into the DPE remediation system; • Prepare a work plan to advance a minimum of three additional borings to define hydrocarbon impact in the Hydrogeologic Unit 4 (HU4), defined by AGE as between 60 and 72 feet below surface grade (bsg), south of MW-16 and east of MW-20 if additional assessment of soil and/or groundwater impact were a requirement for site closure; and • Continue operation of the DPE remediation system in accordance with the EHD directives by letter dated 10 October 2011. The EHD responds to the above recommendations as follows: • Based on historical groundwater analytical data collected from MW-12 and MW-13, the EHD approves the bi-annually sampling of these two wells; analyze the groundwater only for TPH-g, and benzene, toluene, ethylbenzene and total xylenes (BTEX); • The DPE remediation system is being monitored monthly and it is unclear what additional monthly monitoring AGE proposes for DPE -1 and DPE-2; please clarify; • As stated above, the EHD approves the 18 February 2014 addition of MW-15 to the DPE remediation system as was tentatively approved by email on 10 January 2014; and • Based on the groundwater analytical data collected on 01 January 2014 for MW-16 (screened between 65 and 70 feet bsg), MW-17 (screened between 90 and 100 feet bsg), and MW-20 (screened between 65 and 70 feet bsg), it appears that the groundwater plume is not defined south and east of the former underground storage tank (UST) location. The EHD directs that a work plan be submitted by 17 October 2014 to define the lateral extent of the groundwater plume. Conduct all work in accordance with the budgetary status of this site as established by the UST Cleanup Fund. If you have any questions, please contact Vicki McCartney at (209) 468-9852 or by email at vmccartney0sicehd.com. Sincerely, Victoria L. McCartney, REHS Nuel C. Henderson, Jr., PG Senior Registered Environmental Health ecialist Engineering Geologist c: Mr. Timothy J. Cuellar, Advanced GeoEnvironmental, Inc., 837 Shaw Road, Stockton, California 95215 Ms. Cori Condon, PG, CHg, California Regional Water Quality Control Board Central Valley Region, 11020 Sun Center Drive, Suite 200, Rancho Cordova, California 95670