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Dudash,Joe From: Walker, Byron Sent: Thursday, January 27, 2005 12:02 PM To: Dudash,Joe Cc: Hernandez, Dan; Brown, Sandy Subject: TR-36, C-1996-083, Gob Pile Stability Review Dear Joe, I have completed my review of the Geotechnical Engineering Study, January 13, 2005, prepared by Lambert and Associates. Also reviewed was J.E. Stover and Associates letter of January 14, 2005 and page 13 of the proposed TR. Your memorandum to me of January 24, 2005 was also reviewed. The technical revision as submitted is acceptable as an interim report, but does not demonstrate compliance with Stipulation 16. The proposed flattening of the upper slope is presented as resulting in an acceptable stability factor of safety depending upon the gob strength characteristics used. Also, the acceptable stability of the existing pile is qualified as depending upon the gob strength characteristics used. With regard to the last paragraph, 2nd sentence, of the revised page 13, the report assures that the existing pile as constructed and with a future slope of 2.75:1 above the first 50 feet, and as it approaches 100 feet in height (see Figure F, a factor of safety of 1.489), would be stable. Figure E so indicates if it is 100 % coal gob, and Figure F indicates so if it is 75% gob. There is nothing that indicates if the % of coal gob drops below 75%. With your concurrence, I called Jim Stover. He acknowledged that the report does not demonstrate that the fill, as approved, will be stable with a minimum factor of safety of 1.5, nor that the report meets the requirement of the stipulation that the operator will determine site-specific characteristics of strength parameters of cohesion and angle of internal friction of coal processing waste materials (the mix) actually placed in the embankment. Such is the purpose of additional testing outlined in the cover letter of January 14, 2005. Please see me if you have any questions. All materials provided are returned (hand carried) to you Byron