Introduction: Goals and Objectives-
 |
| Figure 1: Trempealeau County Study Area |
For the impact model, the lab considers the site placement's impact on factors related to its proximity to residential and school locations, environmental impact on local streams and wildlife habitats, and in considering if the placement will interrupt prime farmland locations.
The suitability model, contrastingly, considers the best placement on behalf of the industry. considering factors regarding the geology of the underlying surface, landcover, the water table, slope, and proximity to rail terminals of potential locations.
The combination of these two considerations will ultimately reveal a spectrum of placement options, ranging from most favorable sand mining site placement locations to least favorable. This lab will specifically focus its attention primarily on the lower half of the county to relieve geoprocessing time. A reference map of the study area is provided in Figure 1.
Methods:
Suitability Index:
The first series of maps developed attempt to narrow in on all the environmentally suitable areas for sand mine placement based on a ranking class system, where a value of 3 indicates areas which are highly suitable, and a value of 1 indicates areas of low suitability. A ranking table has been provided for each of the five factors being evaluated for suitability, revealing the details that make up each rank for each factor.
Geologic Criteria:
In Western Wisconsin, there are two key geologic formations most desirable for frac sand mining: the Jordan and Wonewoc formations. A map of west central Wisconsin bedrock was provided to students for locating these ideal locations. After converting the Trempealeau County feature class into a Raster file, a Reclass was performed on the new raster file to rank the underlying geology options as either suitable with a ranking of 1 (if Jordan and Wonewoc) or unsuitable with a ranking of 0.
Land Cover Criteria:
Obtaining the Land Cover information required a revisit to a previous assignment, where land cover data for Trempealeau County was previously downloaded from the NLCD website. Using this raster file, a reclass was performed, and the following land cover types were selected to fit the following suitability ranks shown in Chart 1.
Land cover types were prescribed a number of one, two, or three to represent their initial suitability for development. Wide spaces of flat, vacant land was prescribed a three, selected as highly suitable areas because they are areas that are readily available for build. Areas that were already highly developed or included water were prescribed a one, selected as areas that are not very suitable because they would either require clearing or filling to transform the area into a buildable location. Other areas were prescribed a value of 2, falling somewhere in the middle in terms of location convenience.
Railroad Proximity Criteria:
The location of the mining site would be most optimal in an area nearby to a pre-existing rail terminal for transport of the materials. The Euclidean Distance tool can be used to establish a raster file from exercise 5's railnodes shapefile, with a proximity ranking radius. From there, a reclass was performed to limit the distance ranking from 10 distance classifications to 3 distance classifications, with the nearest areas ranked as a value of 3 for high suitability, and the furthest areas ranked as a 1 for low suitability.
Slope Criteria:
Ideally, the location of the mining site would be built on relatively flat land. Using a DEM file depicting elevation, the slope tool and block statistics tool was used to assemble a slope raster file for reclassing. .
Water Table Depth and Stream Proximity Criteria:
The streams original feature class file was found in the Trempealeau County geodatabase. Students had to make a determination as to which types of steams risk impact and which are lower risks. The map derived for stream impact in this lab identifies the primary perennial streams as the highest impact risk as the main streams in the area that last year round. A separate feature class of this selection was generated, and from there, the Euclidean Distance tool was used to generate proximity ranges classified into three different ranks in reclassification.
Finally, the water table depth raster file was derived from the reclassing of a raster file provided in the class share folder.
Once all the data raster files were created and reclassified into their 3,2,1 suitability rankings, the data could then be compiled into one cohesive raster file indicating areas of suitability using the Raster Calculator tool to add all six prefabricated raster files together, and then multiplying the result by the landcoverExclusions raster file. This process is modeled in Figure 2 below:
Finally, the water table depth raster file was derived from the reclassing of a raster file provided in the class share folder.
Once all the data raster files were created and reclassified into their 3,2,1 suitability rankings, the data could then be compiled into one cohesive raster file indicating areas of suitability using the Raster Calculator tool to add all six prefabricated raster files together, and then multiplying the result by the landcoverExclusions raster file. This process is modeled in Figure 2 below:
 |
| Figure 2: Suitability for Sand Mining Index Raster Calculations |
Results:
