2017-08-16_PERMIT FILE - C1981019A

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Cultural Resource Historic Properties Treatment Plan for BK -1-072617 Colowyo Coal Company 2.0 SITE BK -1-072817 DISCOVERY BACKGROUND On July 26, 2017 Tetra Tech's cultural resource monitor was observing topsoil stripping activities associated with haul road construction to the west of Wilson Creek. Within the disturbance area the monitor observed a thermal feature located at approximately 30 cm below ground surface. The monitor immediately halted ground disturbance in the vicinity. Further inspection yielded an additional thermal feature and sparse artifact scatter consisting of heat altered rock, one medium size mammal bone, and one piece of debitage. The two thermal features are intact, but the few associated artifacts are in secondary context. The monitor flagged off a 100 foot (ft) [30 meter (m)] avoidance buffer around the finding and recorded all observed material. On July 28, Tetra Tech provided Colowyo with a discovery report detailing the finding in conformance with Discovery Notification section of Exhibit 5, Item 3 -Cultural Resource Protection Plan for the Collom Mine Expansion. On August 1, 2017, representatives of the OSMRE, Colorado Division of Reclamation, Mining, and Safety (DRMS), Colowyo, and Tetra Tech had a conference call to discuss the discovery and determine the path forward to handle the discovery. 3.0 TREATMENT METHODOLOGY Tetra Tech developed the following treatment methodology based on our prior experience working with similar sites throughout the region and in consultation with OSMRE. The structure of the methodology is based on OSMRE's direct outline discussed on the August 1, 2017 conference call. 3.1 Evaluative Testing Scope and Methods Tetra Tech will conduct evaluative testing to define the site's full horizontal and vertical extent. Intact sediments are still present to the south of the feature up to and beyond the project disturbance boundary. Additional intact sediments occur to the north of the haul road within and beyond the disturbance boundary on that side of the Project. The evaluative testing will take the form of shovel probe testing of all intact sediments remaining south of the features and on the north side of the already disturbed haul road within the disturbance boundary. Testing outside the disturbance boundary will occur only to establish the complete horizontal and vertical extent of the cultural component. Additional data recovery efforts (excavation units, feature recovery, mechanical stripping, etc.) will not be conducted outside the disturbance area as part of the HPTP (See Section 3.3.1). Shovel probe testing will be oriented in parallel rows with individual probes spaced 5 m (16 ft) apart. Shovel probes will be 30 cm in diameter hand dug holes using a spade shovel. Excavation will be conducted in 10 centimeter (cm) arbitrary levels below ground surface. All excavated sediment will be sifted through 1/4" screen. Any encountered cultural material will be collected, cataloged, and bagged with a proper identification and provenience information label. Each shovel probe will be completed to a depth of one 10 -cm arbitrary level into an identified residual sub- strata visible in the adjacent haul road base or at bedrock. All completed shovel probe locations will be GPS plotted and testing data will be collected on Tetra Tech's shovel probe test forms. Testing will begin closest to the discovery and extend outward. At least two sequential negative tests will be required to terminate shovel probe testing in any given direction In addition to identifying the horizontal and vertical extent of the discovery, the testing will also identify any potential additional intact subsurface cultural resources. The testing results will directly inform the application of data recovery measures outlined below in Section 3.3. The Tetra Tech August 8, 2017