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Table 2: Aquifer Surfaces Variogram Properties <br /> <br />A uifer Surface Variogram <br />Model <br />Nu et <br />Sloe <br />Scale <br />Len th <br />Dawson top Linear 0 4.81 N/A N/A <br />Upper Dawson bottom Linear 0 2.10 N/A N/A <br />Lower Dawson top Linear 0 2.30 N/A N/A <br />Dawson bottom Linear 0 2.05 N/A N/A <br />Upper Dawson sands Linear 3,000 0.06 N/A N/A <br />Lower Dawson sands Spherical 1,070 N/A 1,600 14,000 <br />Dawson sands Spherical 4,000 N/A 6,000 7,500 <br />Denver top Linear 0 2.00 N/A N/A <br />Denver bottom Linear 0 2.58 N/A N/A <br />Denver sands Linear 4,000 0.42 N/A N/A <br />Arapahoe top Linear 0 1.80 N/A N/A <br />Upper Arapahoe bottom Linear 0 1.31 N/A N/A <br />Lower Arapahoe top Linear 0 1.63 N/A N/A <br />Arapahoe bottom Linear 0 2.50 N/A N/A <br />Upper Arapahoe sands Spherical 600 N/A 700 9,000 <br />Lower Arapahoe sands Exponential 400 N/A 400 2,500 <br />Arapahoe sands Spherical 1,900 N/A 2,100 24,000 <br />Laramie-Fox Hills top Linear 0 3.37 N/A N/A <br />Laramie-Fox Hills bottom Linear 0 2.80 N/A N/A <br />Laramie-Fox Hills sands Spherical 350 1 600 15,000 <br />The top, bottom, and net sand thickness surfaces were gridded on a 400-meter spacing. <br />The tops and bottoms were then contoured with a 100-feet contour interval, and the net <br />sand thickness is depicted as color-fill isopach maps. <br />1.2.4 Identification of Outlier Picks <br />After the initial contouring was performed, each surface was reviewed for picks causing <br />bull's-eye contours, defined by rings of closed contours greater than 200 feet higher or <br />lower than the surrounding surface. Such picks were evaluated, and if the bull's-eye <br />contours were caused by one isolated pick or by one pick that disagreed with nearby <br />picks, then the anomalous pick was removed from the dataset. All such picks were <br />excluded from the final gridding and are noted in Appendix B. <br />An additional way to check for potential outliers was to evaluate layer thicknesses of <br />both the aquifers and intervening aquitards. After all surfaces were gridded and initial <br />bull's eye picks were removed, layer thicknesses were computed by grid subtractions. <br />Each surface was subtracted from its overlying surface. For example, the bottom of the <br />Laramie-Fox Hills was subtracted from the top of the Laramie-Fox Hills to compute the <br />overall thickness of the aquifer. Likewise, the top of the Laramie-Fox Hills was <br />subtracted from the bottom of the Arapahoe to compute the thickness of the confining <br />layer between the two aquifers. Each thickness grid was then evaluated to identify areas <br />of negative thickness or areas of anomalous thickness. An example of an anomalous <br />thickness would be where the grid revealed an aquifer thickness of several hundred feet <br />SPDSS Phase 2 Task 42.2 TM -Final 8 <br />2/13/06 <br />