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page 2 Memo to Susan Mowry Animas Mine Waste Pile T.R. area of the Animas mine, as a portion of their permanent program permit, No. C-055-82. That approval contained a stipulation requiring . performance of waste material shear strength testing, in order to verify strength values assumed in the geotechnical stability analysis contained within the original application. The technical revision application presents the results of that testing, completed by F. M. Fox, Inc. and submitted to the Division for review under separate submission. Utilizing these amended material shear strength values, the applicant's engineer now proposes to redesign the coal processing waste pile to maximize coal processing waste storage capacity. In completing the redesign and reanalysis of the coal processing waste pile, the engineer utilized a simplistic Homographic stability analysis technique developed by the U. S. Bureau of Mines for estimating the factor of safety for tailings embankments and impoundments. During the completion of the original pile's design analysis, the Division considered this technique acceptable, because of the conservative assumptions made concerning waste strength values and because of the relatively high safety factors projected. However, the proposed redesign of the coal processing waste pile ~repreaenta an increase in pile height from 145' to 320', and a volume increase from 1 million to 3 million cubic yards. It is my opinion that the proposed amended coal processing waste pile should be the subject of an appropriate sophisticated site-specific mathematical slope stability analysis, prior to approval of the proposed technical revision. Tesarik 6 McWilliams, authors of Bureau of Mines Report of Investigations 418564 (1981), relied upon by the applicant in analyzing the pile's stability, state on page 12 of their report; "The charts should be a useful tool in initial embankment design or field work where detailed stability analysis is not i~pera[ive., However, the charts are not meant to replace the use of elope stability models where time and resources are available." In the supplemental letter submitted by the applicant August 29, 1983, the applicant states: "Concerning the stability analysis of the revised design, it is recognized that a more sophisticated analysis should be performed, due to the increased height and steepness of the slopes. New refuse samples will be gathered and analyzed in the lab for the necessary stability parameters used in the deeign and also to compare with the previous results. Until this deeign is performed, it is requested that the pile be constructed to the elopes described in the revision up to the 2nd terrace. If the results of the stability analyses show that the elopes should be lessened, then the elopes already installed would be reworked to obtain the desired slope and all future slopes would be installed likewise." The applicant requests that a conditioned approval be granted to allow appropriate construction of the earlier portions of the coal processing waste pile, now under construction as a portion of the