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vv v Subject: Clarifications And Adedum Reference: Facility Site Code: 19093 Date: January 24, 2008 y Page 2 of 4 ` PSC agrees to move CPT -4 in a location along a north -south line with HI I, H10, and H16. However, to fulfill the investigation objective of addressing the data gap of soil concentrations in the southern direction from the source of the release, PSC would prefer to keep the location of CPT -4 close to the southern property boundary rather than moving the location approximately 10-15 feet north as recommended by EHD. PSC proposes to use a membrane interface probe (MIP) to vertically delineate impact to 100 feet below ground surface (bgs). This exploration tool will collect semi -quantitative data on concentrations of contaminants of concern (COC) as well as soil conductivity to profile impact and lithology for the full depth of exploration. A discrete soil sample will still be collected at 23 feet bgs to quantitatively assess the concentrations detected in H11. This sample will be analyzed for the COC; gasoline (TPH-g); benzene, toluene, ethyl benzene, and total xylenes (BTEX); methyl tertiary -butyl ether (MTBE), ethyl tertiary -butyl ether (ETBE), di -isopropyl ether (DIPE), tertiary amyl -methyl ether (TAME), tertiary butyl alcohol (TBA), and 1,2-dichloroethane V (1,2 -DCA). A revised Figure 10 from the original Work Plan showing the new proposed location for CPT -4 is included in the attached Addendum. The Addendum also presents a discussion on the revised CPT and MIP procedures. L 2. ETIC proposes to advance CPT -5 at the eastern edge of the former gasoline UST excavation about two feet east of borehole 2B. EHD believes CPT -5 would be A. better located haffivay between boreholes 2A and 2B, approximately in the center of the ,,former UST pit, and closer to borehole H9 where high concentrations of CO ere detected in groundwater samples and soil samples collected at 54 feet bgs in November 2006. In addition to collecting grab groundwater samples, soil samples should be collected to vertically delineate hydrocarbon contamination at the source area. PSC agrees to move CPT -5 in the location recommended by EHD. The method i of investigation proposed in the work plan is cone penetration testing (CPT). L. Cone Penetrometer rigs are not well suited for collection of multiple soil samples E l.{ i nom` to vertically delineate samples. In lieu of collecting soil samples at 5 -foot 5✓M-Z `A i intervals in CPT -5, PSC proposes to use the MIP to vertically delineate impact toM �. 100 feet bgs. A revised Figure 10 from the original Work Plan showing the new proposed location for CPT -5 is included in the attached Addendum. As previously mentioned, the Addendum presents a discussion on the revised CPT i- and MIP procedures. 3. ETIC proposes to advance CPT -6 approximately three feet west of borehole Hl; 4. and in addition to collecting grab groundwater samples, ETIC proposes to collect two soil samples at depths of approximately 30 and 35 feet bgs to laterally ` delineate hydrocarbon contamination north of the former gasoline UST \\\ excavation. EHD recommends CPT -6 be located in line with H9 and H16, approximately twelve feet north of borehole H16. In addition to collecting soil PHILIP ENVIRONMENTAL SERVICES CORPORATION 210 West Sand Bank Road, Columbia, IL 62236 i (618) 281-1543 Fax (618) 281-7020