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HARLAN &ASSOCIATES, INC. <br /> CONSULTING HYDROGEOLOGISTS AND ENGINEERS <br /> 3900 South Wadsworth Boulevard,Suke 155 <br /> Lakewood,Colorado 80235-2205 <br /> (303)988-7270 • Fax(303)989-8188 <br /> October 22, 1996 <br /> Mr. Kevin Riordan <br /> District Ranger <br /> U.S. Forest Service <br /> P.O. Box 309 <br /> 620 Main Street <br /> Carbondale, Colorado 81623 <br /> Dear Mr. Riordan: <br /> Re: Coal Basin Mine Environment Site Assessment: <br /> Clarification of Issues Raised by U.S. Forest Service <br /> The purpose of this letter is to clarify, on behalf of Mid-Continent Resources, the issues <br /> raised by Mr. Jerry Thomas, Forest Engineer with the U.S. Forest Service, in his memorandum <br /> of September 10, 1996, to Messrs. Barry Sheakley and Bob Lawton. <br /> Baseline <br /> In this comment, a question is asked regarding standards for polychlorinated biphenyls <br /> (PCBs) which would serve as a basis for comparison with the reported analytical results. It <br /> should be emphasized here that PCB concentrations for all liquid and solid samples, except one, <br /> collected as part of the Coal Basin Mine environmental site assessment, were below the <br /> analytical laboratory reporting limits. The one exception was a sample from an electrical <br /> transformer which contained PCBs at 11 mg/l (parts per million), which is below the regulatory <br /> limit of 50 mg/l set under the Toxic Substance Control Act(TSCA) and, therefore, unregulated. <br /> This transformer has subsequently been removed. <br /> The standards for PCBs vary depending on the medium and agency involved. As noted <br /> previously, electrical transformers are considered to be PCB-containing if they contain greater <br /> than 50 ml/l total PCBs. <br /> The established standards for soils are less clear. Providing PCB contamination in soil <br /> did not occur as a result of a spill or leakage from a regulated transformer, our experience has <br /> been that cleanup levels for PCBs are set on a case-by-case basis, based on a risk assessment. <br /> If PCB soil contamination occurred as a result of a leak or spill from a regulated electrical <br /> transformer, it is regarded as hazardous under TSCA irrespective of the residual PCB <br /> concentration. <br />