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2023 Cultural Resource Site Assessments for Collom Expansion Project Colowyo <br />Tetra Tech June 2023 32 <br />For Official Use Only: Disclosure of Site Locations Prohibited (43 CFR 7.18) <br />5.0 CONCLUSIONS/SUMMARY <br />In 2023 Tetra Tech conducted the third round of cultural resource site assessments for 15 <br />previously identified cultural resource sites (Sites 5MF.969, 5MF.1652, 5MF.3996, 5MF.4003, <br />5MF.4006, 5MF.4008, 5MF.4010, 5MF.5417, 5MF.5418, 5MF.5419, 5MF.6088, 5MF.6098, <br />5MF.6116, 5MF.6128, and 5MF.6130) as part of the Colowyo Coal Company’s Collom Project. <br />Colowyo has committed to avoid the sites during all present and future mining related activities. <br />Through the Colorado DRMS, OAHP mandated that assessments be repeated at four-year <br />intervals for a minimum of 12 years. Tetra Tech conducted the initial round of assessments in <br />2015 (Karpinski and Dugmore 2015) and a second round in 2019 (Karpinski et al. 2019). <br />In 2023 Tetra Tech completed the third round of assessments. All 15 sites were found to be in <br />similar condition to their most recently reported assessment condition in 2019. Overall, vegetation <br />coverage was significantly denser in 2023 than in previous visits due to a very wet winter. Each <br />wash in the valley bottoms was full during the revisit and prevented the physical revisit of all <br />portions of Site 5MF.6128. The flooding was occurring within, but not adversely affecting the <br />center of Site 5MF.4008. Site 5MF.3996 has had a part of the wash bank naturally slump into the <br />wash. However, no artifacts or other cultural material were observed in the sediments exposed <br />by the wash; therefore, the impact from the slump is considered minimal. Site 5MF.1652 was still <br />accumulating aeolian sediments resulting in the burial of all previously documented cultural <br />features. The added sediment is not considered to be an impact to the site. The cairn at Site <br />5MF.5419 that was not relocated in 2019 was relocated in 2023. The cairn was found under a <br />stand of dense vegetation growth. No changes to the cairn were noted compared to the 2015 <br />revisit. The topmost portion of the mining topsoil pile is visible from the cairn at Site 5MF.6116. <br />However, the change in the site viewshed is not significant and is not impacting the site setting. <br />Tetra Tech does not recommend any additional work at the assessed sites. Colowyo should <br />continue to avoid the sites during the development of the Collom Project. In the event it is <br />discovered that any of the monitored sites have been inadvertently impacted between mandated <br />assessment events, contact the Colorado OAHP at (303) 866-3392.