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� r�1 <br />REC ��r 'r <br />WWL Western Water & Lana, Inc. - <br />DIVISION OF R� <br />MINING AND SAFETY <br />December 19, 2013 <br />Mr. Travis Marshall <br />Colorado Division of Reclamation, Mining and Safety <br />1313 Sherman St. Room 215 <br />Denver, CO 80203 <br />RE: Response to DRMS PAR; Permit No. M- 77424, Logan Wash Mine Technical Revision No. 8: <br />Mine Water Infiltration <br />Dear Mr. Marshall: <br />Western Water & Land, Inc. (WWL) on behalf of Occidental Oil Shale, Inc. (OOSI) has prepared this response <br />to your Preliminary Adequacy Review (PAR) (October 11, 2013) of Technical Revision No. 8 for Mine Permit <br />No. M- 77424, Logan Wash Mine (September 26, 2013). Technical Revision No. 8 proposes to infiltrate mine <br />water discharge from two existing Colorado Discharge Permit System outfalls (permit no. CO- 0048816). This <br />mine water management will occur under provisions of Memorandum of Agreement (MOA) for the <br />Implementation of SB 181 Amendments to the Colorado Water Quality Control Act (25 -8 -101, et seq.) <br />Pertaining to the Regulation of Mineral Mines (Dec. 14, 2010). Infiltration will occur within waste rock of the <br />Lower Bench. <br />WWL has prepared various data and information to address each issue or clarification as presented in your letter <br />of October 11, 2013. Each issue is addressed separately below. <br />1. Due to the proposed infiltration of water into the waste rock the stability of the feature may be <br />compromised. Please provide an engineered slope stability analysis for the lower bench waste rock <br />pile. <br />Response: <br />A slope stability analysis of the lower bench was performed by a geotechnical engineer under <br />subcontract to WWL. The analysis utilized the well - known computer code PC STABL 5. The <br />general solution of slope stability using a 2 -D limiting equilibrium solution is assessed with <br />the code. The PC STABL 5 code is a DOS version of the STABL computer algorithm that <br />has been widely accepted for more than 30 years to analyze geotechnical slope stability. The <br />program was initially presented at Purdue University and has gained wide acceptance in the <br />geotechnical community since 1975. <br />The results of the computer simulations indicate that the addition of infiltration water to the lower <br />bench waste rock pile does not significantly decrease the safety factors associated with the existing <br />waste rock dump, i.e. with no infiltration occurring. Attachment A presents the detailed results of the <br />slope stability analysis study. <br />Applications to Earth Science 743 Horizon Court Suite 330, Grand Junction, CO 81506 <br />Phone: (970) 242 -0170 Fax: (970) 242 -0270 <br />