2018-03-19_PERMIT FILE - C1981019 (2)

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Data Recovery Report for Three Sites at the Collom Project Colowyo Coal Company feature excavation was maintained using a sub -datum (usually southwest corner of the unit), string, line level, and tape measure. The feature's entire horizontal extent was then exposed by trowel scraping the surface sediments. The horizontal extent of the exposed feature was mapped, photographed, and a feature form was started. Once this initial documentation was completed, one half of the feature was excavated within 10 cm arbitrary levels in natural/cultural stratigraphy. After half of the feature fill was removed, the excavator completed a feature profile map and the profile was photographed and documented. Once all profile documentation was complete, the remaining half of the feature was excavated and feature fill from both halves was collected as outlined in Section 3.1.2. Any encountered artifacts, HAR, and large (> 1 cm) unmodified gravels were point plotted and mapped on the appropriate feature form map. Encountered artifacts within a feature were collected as outlined in Section 3.1.2. 3.1.4 Evaluative Testing Tetra Tech's PI directed the evaluative testing at each locality. The testing was done to define each site's cultural component's full horizontal and vertical extent using Shove Test Probes and Test Units. Testing was the only data recovery activity that extended beyond the Project's disturbance boundary into intact sediments. If found, the site portions outside of the disturbance area were to be protected during Project construction using the same avoidance measures employed for all other NRHP eligible or Needs Data cultural resources within Colowyo's permit boundary. Any site portions extending outside the disturbance area were also added to Colowyo's site list for cultural resources requiring regular interval monitoring as outlined in Exhibit 5, Item 3 - Cultural Resource Protection Plan for the Collom Mine Expansion. 3.1.4.1 Shovel Test Probes (STP) Initial testing was completed using several STPs oriented in parallel rows across the discovery's cultural manifestation and/or within adjacent intact sediments. Initial individual STPs were spaced 5 m (16 ft) apart. STPs were 30 cm in diameter hand dug holes excavated in 10 cm arbitrary levels below ground surface. If a STP encountered cultural material, a radial STP was completed in each cardinal direction and spaced 2.5 m (8.2 ft) from the positive STP. If radial STPs were positive, then additional STPs were placed at 2.5 m (8.2 ft) spacing in cardinal directions from the initial positive radial STP. All excavated sediment was sifted through % inch wire mesh. 3.1.4.2 Test Unit Excavation Based on STP results, the PI determined that only one test excavation unit was needed at any of the investigated locations. The one test excavation unit was opened at Site 5MF.8394 to further investigate a possible subsurface cultural component encountered in two STPs. The unit was placed to correlate to the overall site specific grid established using a Trimble GeoExplorer 6000 series GeoXH GPS unit. The 1 by 1 m unit was completed using manual excavation techniques and excavated in 10 cm arbitrary levels within natural stratigraphy. All removed matrix was screened through % inch wire mesh and all encountered artifacts collected as outlined in Section 3.1.2. The backdirt pile(s) were established in areas already disturbed and/or determined to be culturally sterile. The PI determined the encountered phenomena was non -cultural and excavation of the unit was halted. The back dirt was returned to the completed 1 by 1 m test unit. Tetra Tech February 2018 14