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Mr. Marshall Cloud <br /> February 14, 2003 <br /> Page 2 <br /> Specific Comments <br /> 1.) Page 4-6, Table 4-1; Vapor Monitoring (VM) well VM0054 shows an initial <br /> baseline concentration of Tetrachloroethene (PCE) at 5000 parts per billion <br /> volume (ppbv), but post-phase 2 concentrations show concentrations of 9200 <br /> ppbv at the well. Please provide rationale in the report on why post-phase-two <br /> concentrations are almost twice as high as baseline after operating the <br /> extraction system for more than a month. <br /> 2.) Page 4-7, Table 4-1; Vapor Extraction well VE0044 Trichloroethene (TCE) see <br /> specific comment#1. <br /> 3.) Page 5-5, Table 5-3; This table shows that only 3.4 lbs. of PCE was estimated to <br /> be in Area 1. However, approximately 29.5 lbs of PCE has been removed from <br /> this area to date. Please discuss in the report why the remedial design severely <br /> underestimated the amount of PCE present in the vadose zone. <br /> 4.) Page 5-5, Table 5-3; Area 2, see specific comment #3. <br /> 5.) Page 5-23, Figure 5-7; The figure illustrates that TCE concentrations for Area 1, <br /> circuit 2 increased towards the end of Phase 2 operations. Please provide some <br /> rationale in the report for the jump in concentrations (i.e. system maintenance, <br /> temporary shutdown, etc,). <br /> 6.) Page 5-35, Figure 5-13; Area 2, circuit 2 see specific comment#5. <br /> 7.) Page 5-47, Figure 5-19; Area 3, circuit 2 see specific comment#5. <br /> 8.) Page 6-2, Section 6.3.5, last bullet; The focused operation phase calls for the <br /> shutdown of three SVE wells in the middle of an apparent TCE vapor plume. <br /> Please discuss in the report whether the conversion of VM0071 to an extraction <br /> well will provide a sufficient radius of influence to capture the remaining TCE in <br /> soil gas. <br /> If you have any questions or comments regarding this letter, please feel free to contact <br /> me at (916) 255-3713 or e-mail me at pmacnich(a-.dtsc.ca.gov <br /> Sincerely, <br /> -0 �' )Ve <br /> Peter MacNicholl <br /> Remedial Project Manager <br /> Office of Military Facilities <br /> cc: See attached page. <br />