2016-11-23_PERMIT FILE - C1981019 (2)

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Cultural Resource Site Assessments for Collom Expansion Project Colowyo 5MF.4010 — Prehistoric Lithic Scatter 5MF.5417 — Rock Cairn 5MF.5418 — Rock Cairn 5MF.5419 — Rock Cairn 5MF.6116 — Rock Cairn 5MF.6130 — Prehistoric Lithic Scatter 5MF.6088 — Prehistoric Lithic Scatter 5MF.6098 — Historic Homestead and Prehistoric Lithic Scatter Abstract Tetra Tech conducted the cultural resource site assessments for 15 previously identified sites (Sites 5MF.969, 5MF.1652, 5MF.3996, 5MF.4003, 5MF.4006, 5MF.4008, 5MF.4010, 5MF.5417, 5MF.5418, 5MF.5419, 5MF.6088, 5MF.6098, 5MF.6116, 5MF.6128, and 5MF.6130) as part of the Colowyo Coal Company's Collom Expansion Project. Two of the sites are determined eligible for inclusion on the NRHP and the remaining sites are listed as needing data prior to NRHP determination. All 15 sites were relocated and assessed during field work. Overall, Tetra Tech found the sites in similar condition to their most recently reported 2005 condition. Observed changes and/or impacts were from taphonomic forces typically faced by all archaeological sites throughout the region. No impacts were observed that were directly related to Colowyo mining related activities. All of the cairn sites are unchanged since the 2005 recordings. Impacts to sites with prehistoric components included minor to moderate livestock grazing activities and natural erosion forces. Site 5MF.4010 had the most significant impact to a prehistoric component. Natural erosion of the cutbank caused a large slump event burying the originally exposed in situ artifact scatter. However the slumping event did not affect the site's potential to contain intact subsurface cultural components. No changes to the site's NRHP status or additional work is recommended at this time. Impacts to sites with historic components included deterioration of artifacts and collapse of non -used or maintained structures. Site 5MF.4003 had the most significant impact of a historic component. Since 2005 Buildings 1 and 2 have been demolished and a large area of vegetation has been removed in the north end of the site. The reason and/or date of the post -2005 disturbance is unknown. The historic component has been previously determined to not contribute to the site's potential NRHP eligibility; therefore impacts to the historic component, regardless of origin, are considered not adverse. No change in the site's NRHP status or further work is recommended at this time. Additionally, Tetra Tech conducted GIS suitability analysis to define HPAs within Colowyo's permitted disturbance areas for the Collom expansion. The analysis classified 727 acres (approximately 30 percent) of the permitted disturbance areas as HPA. The areas have a high potential for the burial and preservation of cultural resources that could be impacted during mine related activities. Areas designated as MPA and LPA have a low to no potential for cultural resources to be buried, preserved, and to be encountered during mining related activities.