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<br />• documentation. The Division recognizes a technical differentiation between excess spoil fills <br />and backfill associated with "Mountaintop Removal" mining. Area backfill slopes continue <br />above excess fills (plateau outslope) [Rule 4.26.2(3)] and the Division concurs with benches at <br />40-foot vertical intervals witlt overall slopes at 3h:ly or less as indicated on Figure 1. [Such <br />procedures provide for slopes within the factor of safety envelope of 1.3, and provide for erosion <br />control and constructability (Report, page 3)]. Please expand the CTL/Thompson Stability <br />Analysis and Geotechnical Recommendations for the Lorencito Surface Mine Phase 1 with a <br />correlation between pseudo-static earthquake coefficients and the seismic parameters associated <br />with adjacent blasting [Rule 2.05.3(6)(a)(vii)]. Please clarify the text of the Report (Page 2) <br />whereby six sedimentation ponds are to be built below the excess fills and eight aze shown on <br />Figure 1] <br />~J 11~~ Response - CTL/Thompson's pseudo-static analysis indicates a factor of safety of 1.3 is <br />1 maintained up to a horizontal acceleration of 0.125g. Since Terzaghi's earthquake ranking scale <br />~ refers to an acceleration of O.lg as a "severe" earthquake, LCC believes it is reasonable to <br />~~ assume that an ANFO blast of less than 740 lb per delay should be substantially less seismic than <br />a severe earthquake, and, therefore, that the fills should be stable. <br />Individual fill designs will be provided to the Division as soon as they are available. <br />35 Please reconcile the differences in volumes of fills 4 though 9 as estimated in Exhibit 16, <br />pages 5 through 9, and the CTL/Thompson Report, Job No. 32,611, of Permit Revision Ol. No <br />such summary was provided for the Lorencito (contour or steep slope mining) fills. Individual <br />designs as requested under Question 67 would answer many items of Question 91 as well. Each <br />design should show a plan view, surface drainage ways, provide the volume of the fill, toe and <br />top elevations, and a cross section showing slopes (surface and original), benches, subdrains, <br />keytivays, filter fabric, etc. (references to specific details on other drawings, pages etc. would be <br />acceptable) [Rule 2.05.3(6)]. F,ach design needs to be certified in accordance with Rule <br />2.05.3(6)(6). Each plan should carry the certification by the design engineer that the site had <br />been field verified, that head of hollow or valley criteria does/does not apply, and that seeps <br />were/were not present. Individual designs for ponds would be dimensioned drawings such as <br />shown on Figure EX 15-14, including all control elevations (including the bottom of the pond). <br />J ~ ~ Response -Individual design drawings for each fill are not available at this time. These will be <br />submitted as soon as they are available. CTL/THOMPSON did not calculate fill volumes. For <br />i ~ ~(~ their purposes, their only concern was that they did not exceed one million tons. <br />36. e CTL/Thompson stability analysis indicates that site conditions are considered generally <br />orable for construction of proposed sedimentation ponds. Please enhance your investigations <br />to determine that the sites are, in fact, favorable (in accurate, not general tetms).[Rule 4.05.9(6)] <br />~1 ry, ResQonse - As specified in the attached July 27, 2001, letter from CTL/Thompson, <br />~,~I„11'j,11` CTL/Thompson's observations and/or investigations at each of the sedimentation pond locations <br />~~ were favorable. In their opinion, they have made sufficient observations and investigations to <br />confirm stability. <br />