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ATTACHMENT I <br /> EPA COMMENTS ON THE DRAFT <br /> COMPREHENSIVE RI WORK PLAN (JAN 92) <br /> FOR DDRW-TRACY <br /> GENERAL COMMENTS <br /> GROUNDWATER <br /> 1. In the investigations of possible cross-contamination of the <br /> Lower Tulare Member of the Tulare Formation, possible <br /> "point" sampling of existing onsite water supply wells and <br /> off-site agricultural wells has been suggested. While it is <br /> desirable to gather analytical data on the water quality in <br /> the Lower Tulare, it is very important that it be done <br /> without introducing contamination into the Lower Tulare in <br /> the drilling for abandonment, purging and sampling <br /> procedures of these wells. The wells in question (1, 2 , 3 , <br /> 4 , 5, 6, AG-1, AG-2 and AG-3) are old wells which likely <br /> have some deterioration of the well construction material <br /> and which have been screened in multiple water-bearing <br /> zones, some in both the Upper Tulare and Lower Tulare <br /> Members of the Tulare Formation. <br /> 2 . Further downward migration and redistribution of TCE and PCE <br /> were noted in the area north of DDRW-Tracy at LM55, LM56, <br /> LM57 , LM66, LM67, LM81 and RASPO AG-3 . This downward <br /> migration causes increased concern for involvement of the <br /> Lower Tulare through cross-contamination from the onsite <br /> DDRW-Tracy water supply wells, the off-site RASPO <br /> agricultural wells and the Rose domestic well. The Work <br /> Plan should detail procedures for investigation, and if <br /> necessary, abandonment of these wells. <br /> 3 . Significant net increases in the reported detected levels of <br /> trichloroethene (TCE) and tetrachloroethene (PCE) in Upper <br /> Horizon wells in Contaminant Areas 2 and 3 were noted from <br /> February 1991 to August 1991. The significant increases in <br /> the shallow wells could indicate continued contribution of <br /> the contaminant at the surface or from contaminated near- <br /> surface soil. <br /> 4 . The analytical results shown in Table 2 . 2-3 (Rev. 1) for <br /> groundwater samples from RASPO AG-2 and RASPO AG-3 indicate <br /> the presence of PCE in both wells. There is no description <br /> in the text on the sampling of these wells. State where in <br /> the water column were the samples retrieved. State whether <br /> a well construction log available showing total depth, <br /> screened interval, or geologic log. <br /> I-1 <br />