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

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Cultural Resource Site Assessments for Collom Expansion Project Co/owyo 5.0 HIGH POTENTIAL AREAS Colowyo requested that Tetra Tech define High Potential Areas (HPAs) for the permitted disturbance areas defined for the Collom expansion. HPAs area are defined as having a high potential to bury and preserve previously un -identified subsurface cultural resources. The HPAs were developed using data collected during 2015 site assessments, disturbance area specific environmental data, and information gathered during other previous cultural resource work conducted in the area. The permitted disturbance area was subjected to Class III cultural resource inventory in 2005 and no significant cultural resource were identified within the area (Lowe et al. 2006). None of the 15 cultural resource sites revisited in 2015 are located within the permitted disturbance area. 5.1 Suitability Analysis Tetra Tech employed GIS -based suitability analysis as currently available on ArcGIS version 10.3 to define the HPAs for the permitted disturbance area. Suitability analysis is a raster -based GIS process designed to, given a specific goal/question, assist in determining the appropriateness of an area using a selected series of spatial data variables. The analysis combines assigned values of multiple selected variables to comparatively ranked locations within a defined area relative to their ability to fulfill that goal or answer a specific question(s). The modeler selects the rasters of variables known, or suspected, to most influence the suitability of a given area based on the overall question. The rasters are re-classified by the modeler to be comparable; weighted according to their influence; and added together to produce a single, unified raster ranking. The ranking is interpreted as the suitability of each raster to support a specified goal or contain a desired set of conditions. Analyzable variables cover a broad spectrum of spatial data sets including, but not limited to, physical, environmental, cultural, and economic data. For the current project, the analyzed question was where are conditions within the permitted disturbance area most suitable for cultural resources, if present, to be buried and preserved. The results are not a typical cultural resource predictive model designed to determine the location of evidence for human behavior across a given landscape. Instead the results are a specifically tailored analysis designed to meet the needs and requirements of the project. Tetra Tech utilized as a baseline information from previously completed suitability analysis (Malczewski 2003 and Oheim 2007), as well as, previously developed archaeological models similarly designed to our suitability model (Brandt et al. 1992; Duncan and Beckman 2000; and Warren and Asch 2000). 5.1.1 Variable Selection and Refinement The archaeological record is not a complete material representation of past human behavior, but a varying set of incomplete snapshots into the past. Archaeological research going as far back as the inception of the field has attempted to define variables that contribute to the preservation and/or removal of buried cultural resources. The identified sources of the variables range from natural to man-made. The extensive body of research has shown that a given variable's role, regardless of origin, in preservation or destruction is often dynamic, time bound, and locality specific. However, general overarching variables can be extrapolated from the research. The selected suitability analysis variables are: Slope, Streams, and Landform (Table 2). The three variables are known to influence human behavior across a landscape and affect the potential for an area to bury and preserve the cultural material. Slope was selected since humans prefer level ground for repeated, intensive use that tends to leave a significant material signature. Humans tended to only venture on to steeper terrain for specific and infrequent tasks that typically leave Tetra Tech July 25, 2018 28 For Officla! Use Only: Disclosure of Site Locations Prohibited (43 CFI? 7 18)