Document 4azkDorx14L2BR6Zw2rrwDyOQ

Atm,-m i INTEROFFICE MEMORANDUM Date: From: Dept: Tel No: 08-Apr-1998 02:34pm DAVID E. ELLIS ELLISDE Engineering (302) 892-7445 TO: Gregory A Chapman ( CHAPMAGA AT Al AT WWPS ) CC: ROBERT F. PINCHOT CC: Roger J. Zipfel CC: ANDREW S. HARTTEN CC: PHILIP A. PALMER ( PINCHORF AT Al AT WWPS ) ( ZIPFEL AT Al AT WWPS ) ( HARTTEAS )' ( PALMERPA ) Subject: RE: C-8 PACE Team Meeting Greg: Andrew Hartten and I spent some time together today reviewing our state of knowledge on the C-8 biodegradation investigation. After our last conference call Andrew and I were to gather information about physical properties of C-8 and the Washington Works aquifer for upgrading our estimates. Roger went back to 3M to probe further on the analytical program. fo e z3 C=3 _c~ Using a plot of distance from source vs. C-8 concentration we get a first order K of 0.002. If you use that rate constant and a ground water velocity of 365 feet per year you derive an apparent loss half life of 0.95 years. A ground water velocity of 100 feet per year gives a half life of about 3.5 years. This is where we were at the time of our last conference call. f "Cn. ZE 1.0 PO After our call John Gannon of Glasgow provided us a computer VJ estimated Koc for C-8 of 183,000. This is remarkably high, and would indicate that C-8 sorbs to the aquifer completely. John . and I spoke again today, and it turns out that he has newer information which indicates that this model doesn't work well for fluorocarbons. John thinks that Koc is still very high, but not nearly as high as 183,000. The only current way to get a realistic Koc would be to conduct a lab study. For the moment ]; have arbitrarily chosen to try using a Koc of 5,000. Does anyone have any feedback for us on Koc? 0.-5 "Q f n 'TvF' * J o Andrew is searching for an accurate measurement of the organic carbon content of the Washington Works aquifer. However, the range is probably 0.1% or below. For now we would guesstimate organic carbon to be about 0.05%. These updated estimates take us to a range of updated half life estimates. Without correcting for adsorption you would get a half life of 0.95 to 3.5 years. Correcting using our assumptions (which should be better validated) we estimate half lives ranging (j0 0 2 0 2 USEPA 7791 DE000545 from 13 years at 365 feet per year to 48 years at 100 ft per year. The estimates are quite sensitive to the adsorption corrections. Better estimates of either Koc or organic carbon will be very helpful. Roger's conversations with 3M indicated there was little further information to be gained there. We are left with no detection of dissolved C-7 or of dissolved fluoride to give us an independent confirmation of C-8 biodegradation. As soon as Andrew and I have more/better information we,'11 pass it along. We will be ready for your meeting in May. In the meantime please feel free to contact us. . Dave Ellis Andrew Hartten DE000546 C002Q3 USEPA 7792