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4. Analysis of stability to include the following: <br />• a. The review of available data on existing instability and <br />the monitoring of instability; <br />b. Preparation of stability models for each viable failure <br />mechanism in order to establish a probable range of <br />realistic factors of safety before and after subsidence; <br />c. Identification and characterization of the probable <br />worst-case scenario for failure and an assessment of the <br />impacts to the community, the environment, and so on. <br />5. Preparation of a report communicating the results of all <br />analyses and drawing conclusions from those results. <br />• 2.2 GEOLOGIC ENVIRONMENT <br />Coal mining in the Northfork Valley is associated with the <br />clastic sediments of the Mesa Verde Formation. These sediments <br />were derived from distant western sources principally from the <br />erosion of the Sevier Orogenic Belt in Utah. The sediments were <br />transported eastward and deposited on the western margin of the <br />western Interior Cretaceous Seaway. <br />During the Late Cretaceous, the Larimide Orogeny produced <br />mountain uplifts and deep structural basins. Many of the major <br />Larimide uplifts were the result of the rejeuvanation of Late <br />Paleozoic uplifts such as the Uncompagre-San Luis Highland. To <br />the north and west of the area lies the Piceance Creek Basin. <br />• This basin is a Tertiary/Larimide feature formed by the relative <br />5 <br />