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

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Cultural Resource Site Assessments for Collom Expansion Project Colowyo little to no material signature. Slope also influences sedimentary environment and whether the area is conducive to the burial and preservation of archaeological sites. Water is a critical resource in determining the location of both prehistoric and historic era sites; therefore as the perennial natural water source in the region, streams were included in the model. Water is difficult to transport; therefore intensive, repeat use localities tended to be located closer to perennial water sources. Sites away from water tend to be small, low use, and single activity oriented. Concerning site burial and preservation, the perennial streams in the immediate area tend to have associated low to moderate energy alluvial sedimentary environments. Low to moderate energy alluvial environments have a significant potential to bury and preserve cultural resources as exemplified by nearby sites 5MF.969, 5MF.3996, 5MF.4003, 5MF.4010, and 5MF.6098. Landform was selected to ensure significant topographic features (ex. cliffs, steep walled canyons, and narrow finger ridges) were captured in the analysis. Such landforms can typically be lost in purely slope - based Digital Elevation Models (DEMs) due to selected data intervals and the normalizing means to construct the DEM. Better definition of landforms assists in identifying both locations of preferred human activity and where sedimentary environments are conducive to the burial and preservation of cultural resources. Table 2. Selected Variables and Information Data Source Variable Source Slope Derived from U.S. Geological Survey (USGS) National Elevation Dataset (NED) 30 -meter Streams USGS National Hydrography Dataset (NHD) Landform Utah State University RS/GIS Laboratory - Ten Class DEM Derived Landform for the Southwest United States Each variable was broken down into one of four classification rankings for analysis integration and evaluation. The classification rankings ranged from high suitability (4) through low suitability (1) based on the specific characteristics defined for each variable (Table 3). Once each variable was classified and defined Tetra Tech used the ArcGIS Map Algebra raster calculator tool with 30 m cell size to divide the proposed disturbance area area into individual 30 m ranked cells based on the sum each variable's classification rankings. Each cell had the potential calculated value range of 12 (high) to 3 (low). As significant cultural resources spatially extend beyond a single 30 m cell, the resulting individually calculated cell values were refined by grouping sets of values into three suitability categories. The three categories are: Low Potential Areas (LPAs) (Calculated Values 3 through 6); Moderate Potential Areas (MPAs) (Calculated Values 7 through 8); and High Potential Areas (HPAs) (Calculated Values 9 through 12). The categories define the level of probability an area of cells has be suitable for the previously unknown subsurface cultural resources, if present, to be buried and preserved. Table 3. Variable Classification and Definitions Classification Slope Spring Distance Landform Ranking 4 0-5% 1-50m Preferred (Valley flats, nearly level plateaus or terraces) 3 5-11% 50-200m Acceptable (Gentle sloping ridges) 2 11-30% 200-500m Marginal (Marginal slopes) 1 >30% >500m Avoided (Very steep slopes, scarps, cliffs, canyons) Tetra Tech July 25, 2016 29 For Official Use Only: Disclosure of Site Locations Prohibited (43 CFR 7 18)