2010-06-28_REVISION - C1981019 (6)

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Rio Tinto Energy America Colowyo Coal Company, L.P. COLOWYO MINE 2009 PHASE III BOND RELEASE EVALUATION — YEAR 2 REVEGETATION UNITS IN PHASE III SAMPLING: REFERENCE AREAS: EP028 WPO01 MOUNTAIN SHRUB EP029 WP003 SAGEBRUSH EP030 WP004 EP031 WPOOS EP032 WP006 EP033 WP007 EP034 EP035 1.0 INTRODUCTION Cedar Creek Associates, Inc. (Cedar Creek) was contracted in 2008 and 2009 by Colowyo Coal Company (Colowyo) to evaluate revegetated units for Phase III bond release at the Colowyo Mine. Units included in this Phase III evaluation were established and reclaimed between 1996 and 2000 (with one very small area established in 1995). Sampling was performed in the interest of ascertaining progress toward revegetation success in general accordance with technical revision (TR -72) submitted by Colowyo and approved June 24, 2009. Revegetated areas evaluated in 2008 and 2009 consisted of all or part of 14 units comprising 203.1 acres in East Pit and West Pit. In addition, two reference areas (Mountain Shrub and Sagebrush) were sampled to provide cover and production comparison values to facilitate an evaluation of success for the reclaimed units. Phase III bond release data analysis and presentation by Cedar Creek occurred using standards for the post- mining land use subcomponent of grazing land. Sample points for Phase III bond release and reference areas evaluated in 2008 and 2009 are indicated on Maps 1 through 6. Field sampling for the directly measurable variables of ground cover, production, and woody plant density was systematically conducted from July 28 through August 3, 2008 and July 26 through July 31, 2009. Sampling occurred immediately following the peak of growth in July. Field efforts in 2008 and CEDAR CREEK ASSOCIATES, Inc. Page 1 Rio Tinto Energy America - Colowyo Mine 2009 Phase III Bond Release Evaluation — Year 2