SITE INFORMATION AND CORRESPONDENCE

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p, li i 305 Hutchins, Lode i# page 2 Mike Harper s active gas station(Bokides),did_detect Benzene for this date at 17 ug/r. Additionally, MTBE was detected in MW-5 for the sa 4 e date at 300 ug/l as well as DCA, DCE,TGE,and PCE. It has been the contention ofe consulting firm for the FDIC that constituentsof concern detected in Togo's wells have been directly relates!to the Bokides site. MTBE, Benzene, and DCA concentration levels have shown correlated patterns when the groundwater analyses have been evaluated. .1 MTBE iso-concentration maps�s have shown;an increasing concentration pattern as the groundwater flows southerly onto and through the Togo's site. With this in mind, PHS=EHD planed the Bokides site into the SWRCB Local Oversight Program(LOP) for investigation of their suspected unauthorized release from the UGTs located on their site; l Y I� PHS-EHD concluded in corres ondence,lanua 9, p ry 1996 that the soil still in place ori'the Togo`s site. at 25 feet below ground surface(` bgs):contained TPH-G concentrations as High as 6700 mg/kg in one area and 5000 mg/kg in another area and may be contributing to the groundwater degradation. Since a previous vapor extraction effort from VW-1 has proven to;be effective at reducing 11,000 mg/kg ofTPH-G soil contamination at boring "EB11-25"to non dEtect,'PHS-EHD required additional vappr extraction wells and a:soil vapor extraction test to be conducted at the other areas of concern. A vapor extraction test conducted on the newly installed vapor wells also indicated positive results. it PHS-EHD was preparing to approve this remedial activity when the LawrenceLivermore Study was released and the SWRCB recommended LOP agencies re-evaluate sites based on a"tow. dsk7 ;criteria. Based on a receptortsurvey, the levels of constituents of,,concern at the time;the real possibility that an up-gradieri source existed, and that no significant Benzene contamination was noted in the soil still ori-site, PHS-EHD concluded that vapor extraction.may not be the.:. ostcost- effective method when compared to natural attenuation over time` CVRWQCB recommendations include soil sampling for 1,2 DCA;-as well as TPH G`;.TIH-D,TPH MO, BTEX, and MTBE in"soils above the 1979 water level". Additional recommendations from the CVRWQCB includelf nq 12DCA is detected in soil samples above the 1979 water level,we cu (CVRWQCB)will conrvvith;isite closure....". This statement confirms that the CVRV1 00,does not consider that the primary constituents of gasoline require further investigation and remediation. The only constituent the CVRW. .QCB is concerned with is 1,2 DCA. The TRC discussers the existence and levels of 1,2 DCA in the groundwater extensively and concluded that 1,2 DCA is associated with the degradatlor� of PGE arid.TCE as well as a past additive used in;gasoline: Even;tf 1,20 CA is found in the soil at this site, the source of the 1',2 DCA in the groundwater maybe from the breakdown of the P..E and:TCE In addition,the only drinking water wells within 200616 et 9 ... of this site are up-gradient and it is not anticipated that they will be impacted by a release from this site. Remediation of the 1,2 IBCA in the groundwater does not appear to be cost-effective since the levels:in the groundwater at this time are inconsistent. li e