Laserfiche WebLink
P.O. Box 187 <br />July 16, 2020 <br />f&BPPB& MINWB INC. <br />Craig, Colorado 81626 <br />Ms. Robin Reilley <br />Environmental Protection Specialist <br />Colorado Division of Reclamation, Mining and Safety <br />1313 Sherman Street, Room 215 <br />Denver, CO 80203 <br />Re: Trapper Mining Inc., Permit No. C-1981-010 <br />Permit Revision PR -09, Response to Adequacy Review No. 5 <br />Dear Ms. Reilley: <br />(970) 824-4401 <br />Enclosed are two copies of our response to Zach Trujillo comments to you of June 17, 2020. We are <br />referring to this as Adequacy Review No. 5 to Trapper's Permit Revision PR -09 application. With this <br />letter we are responding to Zach's geotechnical comments on the AOC Variance request. <br />Our formal responses are given below your comments as follows: <br />Truiillo Comment 1. During a Division pre -site visit and inspection in November of 2018, it was <br />observed that the A -pit is partially filled with compacted ash material. However, there was no <br />discussion or inclusion of this material in the stability analysis. Please provide the Division with <br />additional discussion about the ash material found in the A -pit and include it in the stability <br />analysis performed by AAI. <br />Trapper Response to Truiillo Comment 1. The rationale behind not simulating the fly ash already <br />deposited in the Ash -Pit was three -fold; (1) simulations of spoil backfill in all three analyzed pits <br />(L -Pit, F -Pit and Ash -Pit) kept the analysis simple and easy to compare, (2) the fly ash matrix is <br />anticipated to possess greater overall strength compared to spoils, making AAI's analysis <br />conservative from a global stability perspective, and (3) detailed depositional history of fly ash <br />deposit is unavailable, as some of the fly ash backfill have been deposited as -received, whereas <br />fly ash along the bottom of deposit have been mixed with spoils. <br />The fly ash deposited in the Ash -Pit have predominantly originated from the 3`d unit (60%) of the <br />Craig Power Plant, while fly ash from the 1St and 2" d units have supplied 20% each of the pit - <br />backfill. This fly ash has been characterized for chemical and engineering characteristics (Radian <br />Corporation, 1981 Study Report). The chemical analysis of the fly ash indicated that the' ash has <br />