SITE INFORMATION AND CORRESPONDENCE

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i FILE COPY 913 Fremont Valley Showcase,Page 2 1999 located approximately 5 feet westof W-2 were 1,300 ppm of,TPH g, and the results of the soil sample collected at 20 feet bsg were ND in TPH g and 0.010 ppm of Benzene. Analytical results of the groundwater samples-from MW 2 rose from 96 parts per billion (ppb) of TPH-g in March 1994 to 4010 ppb in December 1997, before a continuous decline. to 1,400 ppb of TPH-g in December 1999,while BTEX have steadily and consistently declined from 1994 to the present. Groundwater has been above the.screen'interval (15 feet bsg to 30 feet bsg) and the top of the sand pack(13 feet bsg) in MW-2 since March 1995. Analytical results of the groundwater sample from MW-5 which is screened from 5 feet bsg to 25 feet bsg (current groundwater depth is at approximately 10 feet bsg) were 2,500 ppb of TPH-g and 60 ppb of Benzene in September 1999, but have since fallen to 1,800 TPH g and . 5.2 ppb of Benzene in December.1999. Eleven soil borings were advanced at the site between 1995 and 1996 to define the lateral extent of the contamination. Analytical results of the grab ground water sample collected at 15 feet bsg from the easternmost boring,D-2,were 59, 3.0, 24, 3.6 ppb of BTEX and 5.1 ppb of TPH g,but were ND for any of the contaminants in the grab water sample collected at 24 feet bsg. These findings did not appear to have been taken into consideration in the . drawingof the isocencentration lines in the aforementioned Figure 4 of the report. Historical analytical results of the down-gradient well MW-4 have all been ND for BTEX, TPH g, as well as MTBE except for 0.3 ppb of Toluene and 0.9 of Xylenes in December 1997. Gradient direction of the groundwater has been consistently northeast toward MW 4. In a telephone conversation on June 2, 2000 with JJW,PHS/EHD recommended preparing a closure report that will justify issuance of a "no further action letter" if JJW believes the , site is ready for closure. The closure report should include lateral and horizontal definition of the contamination in both soil and groundwater,justification for that definition including the numbers used to derive the extents of the plume, overhead as well as cross-sectional maps/diagrams indicating the isoconcentration of the various contaminants,the mass calculation (including work) and the analytical results selected for the calculation, and any potential receptors (i.e. a receptor survey) within 2000 feet. In the mean time,you are required to continue to sample the wells on a quarterly basis and submit quarterly reports in accordance with California Code Regulation, Title 23,Division 3, Chapter 16,Section 2652' (d) If you have any questions,feel free to contact Jeffrey Wong at (209) 468-0335. Donna Heran, REHS,Director Environmental Health Division Jeffrey-Wong, REHS Zr�garetgotioJREHS LOP/Site Mitigation Unit IV Supervisor c: RWQCB, Central Valley Region- Marty Hartzell C.: 'JJW Geosciences,Inc. - Toni Mayen E