Document g7VnXymB1n2egxo05ydOZJ89

2195 Front Street Logan, OH 4313S ONeEFftState rfOhio Environm ental Protection Agency Southeast District Office TELE: (740) 385-8501 FAX: (740) 385-6480 A R 2 2 6 -2 6 0 8 Bob Taft, Governor Christopher Jones, Director July 8,2002 Mr. Andrew S. Hartten, Project Director DuPont Engineering ' Barley Mill Plaza - Bldg. 27 Lancaster Pike & Rte. 141 W ilmington, DE 19805 ' Re: Response to Comments and Revised Proposed Sampling Investigation Plan for Little Hocking W ater Association Well Field, Washington County, Ohio June 2002. Dear Mr. Hartten: Thank you for your response to Ohio Environmental Protection Agency's and Little Hocking Water Association's comments on the proposed Sampling Investigation Plan for Little Hocking W ater Association's Well Field. Ohio EPA received your response to comments and revised plan on June 11,2002. The revised plan outlines DuPont's technical approach to determine the horizontal and vertical extent of C-8 in ground water and soil in the vicinity of test well TW-4. The Ohio EPA, Division of Drinking and Ground Waters has completed a review of the response to comments and the revised proposed plan. In addition, the Little Hocking W ater Association, Inc. and their consultants, Bennett & Williams Environmental Consultants, Inc. have reviewed the plan. Ohio EPA agrees with the proposed number o f borings and their locations, and the proposed method to collect soli and ground water samples. However, Ohio EPA believes that additional samples should be collected and analyzed to more thoroughly evaluate the vertical extent and concentration of C-8 at the two proposed locations where both soil and ground water will be sampled. Please see the following two comments: 1. DuPont proposes to collect soil samples from two borings in the vicinity o f TW-4 at the following depths: * at the surface * at the first encountered water (approximately 17 to 20 feet below grade) * at the top of the sand and gravel aquifer (estimated at 30 to 35 feet below grade) * at the bottom of the sand and gravel aquifer (estimated at 50 to 55 feet below grade) Printed oil Recycled Paper ASH028097 E ID 781377 EXD781377 The Ohio EPA agrees with these sample depths, however, the Ohio EPA believes additional samples are necessary to adequately characterize the vertical distribution o f C-8 from the surface to the approximate top o f the sand and gravel aquifer. This date will assist in evaluating the air to soil to ground water route of travel and the potential leaching o f C-8 from the fine grain alluvial soils. Soil samples should be collected at five foot Intervals from the ground surface to the top o f the sand and gravel aquifer, (i.e, approximate depths to be sampled include (5 ,1 0 ,1 5 , and 25 feet below the surface at the two selected locations). This w ill add about 8 additional soil samples for analysis. In addition, Ohio EPA request that DuPont collect soil samples at the remaining five foot interval depths from the two selected borings and retain these for possible future analysis. The decision to analyze these samples would be based on the corresponding water sample results. We recommend language be incorporated into the W ork Plan whereby either DuPont independently could analyze these soil samples or the samples could be analyzed If requested by Ohio EPA. 2. At the two locations where soil is to be sampled, the Work Plan proposes to collect ground water samples at the following depths: at the first encountered water (approximately 17 to 20 feet below grade) at the top o f the sand and gravel aquifer (estimated at 30 to 35 feet below grade) at the bottom o f the sand and gravel aquifer (estimated at 50 to 55 feet below grade). in order to evaluate tee surface water to ground w ater and the ground water flow pathways, the Ohio EPA request that DuPont collect ground wafer samples at these two locations from the first encountered water to the bottom o f the sand and gravel aquifer at five foot intervals. This will allow for evaluation o f potential differences In concentration along different flow lines within the aquifer. Recommendation 3. In addition to the indirect measurements o f river stage height proposed in the Work Plan, a direct measurement o f river elevation should be collected at Kraton Polymers. Jim Thrall, Senior Environmental Engineer with Kraton, indicated to Ohio EPA that a measuring point for river elevation is located on the Kraton property and with permission, DuPont can access this point. Piease contact Jim, in advance, at (740) 423-2278. ASH028088 E ID 781378 EID701378 Both Ohio ERA and the Little Hocking W ater Association would like the investigation to begin as soon as possible, therefore, if necessary, soil samples should be retained until the laboratory is able to analyze the samples, Ohio EPA will approve the proposed Sampling Investigation Plan provided Ohio EPA and DuPont agree on the number of samples to be collected to vertically profile C-8, If you have any questions, concerning the above comments, please contact me. Sincerely, Steven E. Williams Hydrogeologist Cc: Mike Preston, Ohio EPA, DDAGW, SEDO Sarah Wallace, Ohio EPA, DDAGW, SDQ Mr. Robert L. Griffin, P.E. Little Hocking W ater Association Ms. Linda Aller, Bennett & Williams file ASH02B099 E1D781379 E ID 781379