Document DwjrGVQdvO0zb6D45wrbzNyo

AR226-2588 rAndrBwirRartteh" ---- ' "'^n^02?^1"^ To; ex:: Subject: steve.virilllama@6pa.stata.oh.ue Bernard J Reilly/AE/DuPont@DuPont, Laura R Walter/AE/DuPont@DuPont, M. Ann Brad)ey/STB/DUP@DUP, David M Rurak/ABDuPont@DuPQnt Letter Response Forthcoming/RotoeonteQuestions Hi Steve, As per our phone conversation the other day, we will be sending our "Reply" to your Response to Comments/LHWA Investigation either tomorrow or Monday. The other day you also raised the issue of sample heating during use of the Rotosonic drilling method. Our "Reply" is going to include an offer to switch from geoprobe to rotosonic as this will ensure boring advancement to total depth/bedrock, I will be faxing a technical paper on the subject to you following this note. Note; there area number of papers on the subject, and basically all research on the subject conclude this is not a significant issue. Let me give you some summary thoughts on why I think use of rotosonic should not be a concern: Heat generation only occurs during excessive friction slutatlons. Commonly this would occur if a long stretch on unsaturated sand/gravel existed. At LHWA, the top 15 feet of unsaturated soils are moist/fine-grained clays/silts, which should not generate friction Issues. Once in saturated zone at 15 feet, any issue related to heat should go away. A geoprobe, which is very thin diameter, can generate more heat than rotosonie (though even that method should be a non<te6ue at LHWA). Actually, with gaoprobe. heat could become a factor at depth in sand and gravel where Increased point resistance is encountered and we have to uss more hammering action. C-8 is not volatile and heat shold have little impact on soil concentration. With rotosonic, the sample is collected at the center of a 4-inch soil cora where heat build-up is not a factor. This sums it up. As I indicated previously, we would like to go ahead and usa rotosonic for thfl investigation as this will ensure that the full scope Of work Is completed, If you have any additional questions/concerns, please don't hesitate contacting me. Andrew ASH0189B5 EID565487