SITE INFORMATION AND CORRESPONDENCE_FILE 2

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Response to SJCEHD's 8-19-08 Letter—Page)--" Joe's Travel Plaza,15600 S.Harlan Road 6 Mr. Dhoot (and his consultants, Stratus Environmental) do not disagree with this statement. In early 2006, a shift from northeasterly flow to northwesterly flow in the uppermost water-bearing zone was observed and has been fairly consistently observed since that time. Contaminant concentrations increased in water samples from MW13AB and began being detected in water samples from MW03, and have been detected in water samples from MW15A. This 1 demonstrates that the contaminant plume is mobile and undefined.7 7 See comment Nos. 4 and 5 above. Well MW-I 3A/B has shown a slight increase in MTBE but again, the data set for this well limits our ability to demonstrate that the same natural attention that is clearly occurring at all other site wells can also be reasonably assumed to be occurring at MW-13A/13. MW4-3 has shown a 90%decrease in MTBE concentrations from its highest concentration of 121 �g/l, (November 2006)to its current concentration of 12 [tg/L (September 2008). Well MW-15A has shown a 96.8%decrease in MTBE concentrations from its highest level of 71.8 n/L (March 2007) to its current concentration of 2.3 [tg/L (September 2008). The primary and secondary MCLS for MTBE are 13 and 5.0 µg/L,respectively. Thus, while there have been concentrations of MTBE detected in wells MWO-3 and MW-15A, both of these wells show >90% decrease in MTBE concentrations since their highest levels. The EHD must request concurrence from the Central Valley Regional Water Quality Control Board (CVRWQCB) on closure determinations. On August 2, 2007, Jim Barton from the CVRWQCB and I met with Sarah Salcedo and Gowri Kowtha from Stratus Environmental. At the meeting it was discussed that remediation by natural attenuation was probably not viable and that groundwater extraction and treatment may be the most viable option for the sites 8 In Stratus' Record of Meeting Notes, dated August 2, 2007 (which were transmitted to all meeting participants shortly after the meeting and no contradictory comments were received) Straws summarized this portion of the meeting as follows: Stratus presented monitored natural attenuation (MNA) as viable option, since MTBE is [the] only COC and is now only about 200 Rg/1 maximum. SJC/RWQCB indicated that.N4NA was probably not viable and suggested groundwater extraction. Stratus acknowledges that the group discussed, in detail, groundwater extraction and treatment and agreed that it was likely the most viable option fox the site,however, based on the attached Exhibits, all of which illustrate the diminishing MTBE concentration trends at the site, groundwater extraction no longer appears warranted. Contrary to what may have been discussed at the meeting, it is clear from the trends described above and shown in the attached Exhibits that natural attenuation has been very effective and is likely to continue to be an effective remedial method at the site. See also comments 4 & 5 above. There has been little change in site conditions since that meeting. In June 2007,the highest MTBE concentrations were in water samples from MWO-IX (190 µg/L) and in June 2008 the highest MTBE concentrations were in water samples from MWO-IX (120 µg/L):9 9 Well MWO-IX has shown an 83% decrease in MBTE concentrations from its highest concentration of 780 [tg/L (May 2003) to its latest concentration of 130 lig/L (September 2008). While 3