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August 1999 Settecn Con! Company * 1'onst Mrne Hnu/ Rand D Srn6rlin~ Annlvsrs ~ I • SENECA COAL COMPANY HAUL ROAD D STABILITY ANALYSIS 1.0 INTRODUCTION 1.1 PURPOSE: The purpose of [his calculation brief is ro estimate the static factor of safen• (FOS) for the steep portions of Haul Road D using available sod data obtained from the Geotechnical Investigation report for Haul Roads Y-,~ and 1'-B and Sediment Pond O10 and the proposed Haul Road D configuration. The Geotechnical Inyestigauon report can be found in attachment 13-~ m the Toast Ivhne Permit Document. There are nvo steep sections of Haul Road D, one from Sta. 0+00 to 6+20 and one from Sta. i3+00 to G2+00. Both these sections have grades greater than 10% for a length greater than 300 feet. For this report only the sections between station 0+00 to 6+20 were analyzed because there are no significant cuts or fills betveen stations i3+00 to 62+00. 1.2 METHODOLOGY: The static FOS for the steep portions of Haul Road D was estimated using a basic, one-dimensional equilibrium anaksis program called lST.1BL (v5.2). The FOS deternuned is the ratio of resulting resisting forces to driving forces. Resisting forces are the internal strength parameters of the soil • materials used in the construction of the cut and fill slopes. Driymg forces are produced by the weight of the material in the cut and fill slopes. For this anah'sis, a ctrndar failure mode was assumed. The FOS was calculated using the Bishop method. 1.3 PROCEDURE: The analysis was conducted using the proposed design configuration for Haul Road D as shown on Exhibit 13-11.1 of the 1"oast Done permit document (L.eidich, 1999). The analysis was run on the cross-sections at stations 2+87 and ~++50. The cross-sections are shown on the attached computer printouts. The fill and cut slopes are designed at approximately 2H:1 V. The maximum height of the fill and cut slopes m the steep portion of Haul Road D are approxunately 25 feet and ai feet respectivel}' The haul road D and immediate areas have been stripped of topsoil. The underlying subsoil appears to be a shghdy sandy to sandy day that is similar to the soils used in the analysis for Haul Road 1"-1 and T-2. The soil ropes and properties used in the analysis for Haul Road Y-l and I"-2 are included in .~ttachment,~ and summarized in Table 1: blomlgamrr}~ It~ulfan Amrrirm. Int. iGi Saulh Uniou Borr/ruarrl, Suve J 10 ' Ldkrwoad, Ca(orudo 80??8 • (303/ %G3-i li0 /; \8i I \rtFort\I Ioxlrwr/ D i dabr/ilt~ 08/?i/%'7 nh