SITE INFORMATION AND CORRESPONDENCE FILE 1

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•.s Messrs Larson and Trommer February 26, 2014 639 W. Clay Street, Stockton, CA Page 2 of 2 (AGE) characterized the impact as not delineated laterally and vertically. This information leads the EHD to infer that there may well yet be secondary source soil in the former UST No. 3 area. The case does not meet Policy groundwater criteria —the CUF holds that the case does meet the groundwater criterion through Class 2. The EHD does not consider the plume length to have been shown to be less than 250 feet. As noted previously, the intensely impacted MW-1 is approximately 30 feet east of the over-excavation limit and approximately 75 feet from MW-2 located north of the excavation in the area suspected of being most impacted. The benzene concentrations, when monitored on 23 July 2013, increased from 280 micrograms per liter (ug/1) to 2,300 ug/I over the 75-foot distance from MW-2 to MW-1, but the consultant drew the benzene plume boundary only approximately 15 feet downgradient from MW-1 despite the increasing trend from MW-2 and the total lack of HU-2 data downgradient from MW-1. The F_HD is of the opinion that the total plume length could well exceed 250 feet, which would not be consistent with meeting Class 2 criteria for plume length or benzene concentrations. The case does not meet Policy indoor air criteria —the CUF holds that the case warrants the Policy Exclusion for Active Service Stations. Even though the current fueling system is some 200 feet from the area of concern, the EHD will not contest the determination. It is the opinion of the EHD, based on available site data, that the site does not currently meet the LTCP criteria for closure at this time. At the very least, the downgradient extent of impacted groundwater should be determined; if the plume length exceeds 250 feet, remediation should be implemented to reduce benzene to less than 1,000 ug/I. If it can be shown that plume length is less than 250 feet, the site should be moved to closure. Questions or comments should be directed to Vicki McCartney at (209) 468-9852 or to Nuel Henderson at (209) 468-3436. Sincerely, Nuel Henderson, PG Engineering Geologist C: Victoria L. McCartney, REHS 2014 Review Summary Report (Sixth) Response CUF Claim No 8542.doc