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Geotogica(T�echnics Inc. C&B Equipment Page 4 Groundwater Monitoring Report—Site Closure Request Project No.336.2 f October 11,2000 F t 3.0 CONCLUSIONS AND RECOMMENDATIONS - SITE CLOSURE REQUEST r , Conclusions w , F The following conclusions can be made from review of the data: 1. Contaminant concentrations in MW-1 and MW-2 have exhibited fluctuating but stable E trends (not increasing) over the history of the project. r 2. The concentrations in MW-101 have decreased to non-detect suggesting that the deeper aquifer has not been impacted significantly and the contamination is undergoing natural F: M attenuation. 3. A thick fine-grained silty clay unit is present between 30 and 40 feet bgs. This unit i appears to form a significant low permeability barrier to vertical migration of chemicals. 4. The groundwater plume appears to be defined laterally. 5. The domestic well, which is located approximately 45 feet east of the former USTs, has r not been impacted by petroleum hydrocarbons. 6. The concentrations of MTBE in well MW-1, 18 -- 22 ug/l, are not indicative of a reformulated fuel release and do not warrant further remedial action. 7. The presence of ethanol in well MW-101, but no other well, is a result of using a weighted bentonite plug compound to establish a seal in the construction of the deep well. The coating of this material, "TR30/60 Pel Plug", contains 61.31% ethyl alcohol r = (ethanol). The MSDS sheet for the compound is included as Appendix D as support for rr this conclusion. 8. Groundwater consistently flows to the north-northwest between 0.004 and 0.0036 ft/ft. 9. Well surveys performed in 1997 and 2000 indicate that except for the new domestic well located approximately 175 feet NE of the former USTs, there is a lack of water well receptors in the immediate vicinity of this property. Ali Recommendations s The following recommendations are made: r_ I. Given the lack of receptors in this area, it is recommended that no further investigation or monitoring be performed. 2. Given the low permeability geologic unit below 30 bgs and the low concentration of chemicals in the groundwater, it is recommended that this site be considered for closure. r Site Closure Request 1 • In our "Spring Quarter 1998 Groundwater Monitoring Report" dated April 13, 1998, GTI requested site closure on behalf of C &B Equipment. r • In a May 15, 1998 facsimile correspondence responding to our site closure request, Mr. Ronald Rowe, Sr. EHS of the SJC PHS/EHD, directed the submittal of items contained in the Central Valley Regional Water Quality Control Board's (CVRWQCB) Appendix B Tri Regional Recommendations, Checklist of Required Data for Closure of Underground i