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After a subsequent flight and re- measurement, the amount of subsidence was calculated from the <br />difference in elevation at each point that had the same X, Y coordinates. <br />(5) Topographic Base Map From the original DTM data with additional "breaklines" such as <br />drains and ridges digitized in the analytical plotter, a contour map at a 5 foot contour interval was <br />plotted at 1" =200' scale, with the contours being generated automatically from the digitized X, Y, Z <br />points. Contours within Red Wash valley were plotted at one foot intervals so that gradient changes <br />can be detected once subsidence began. In addition, major planimetric details such as roads and <br />rivers were compiled on the map. <br />This map was used for location purposes, and was generated from the original photography only. <br />(6) Subsidence Contours A scribed drawing was made at 1" =200' showing "subsidence <br />contours" at one foot intervals. These contours were based on the difference between the original <br />digital terrain model and subsequent models. BME proposed to provide three subsidence contour <br />maps, one for each survey following the baseline survey. <br />(7) Cross - Sections Cross - sections were generated along grid lines between X, Y coordinates, <br />showing the terrain profile. Profiles from different flights could be combined on one cross - section plot. <br />These were plotted on paper at V =200' H and 1 " =5' V, automatically on a computer- driven flatbed <br />plotter. A separate vertical scale was selected along the subsidence profile to allow a visual <br />recognition of the amount of subsidence. <br />Various cross- sections were produced, each to show the first and subsequent subsidence intervals <br />compared with the baseline data. <br />(8) Accuracy A total of 22 ground control points were monitored immediately prior to each <br />flight. BME completed a Third Order survey on the 22 ground control points, certified by a registered <br />land surveyor, licensed to practice surveying in the state of Colorado. The root mean squared error <br />of the difference in elevations determined from the aerial methods and from on -the- ground surveys <br />was within +/- 0.25 feet. 95% of the elevations differences at these 22 points was within +/- 0.8 feet. <br />(9) Coordination with Surface Observations and Other Monitoring Programs DRMS had <br />expressed concern regarding probable impacts to the hydrologic characteristics of Red Wash. To <br />alleviate this concern, BME install nine alluvial wells in Red Wash to define the alluvium characteristics <br />and any changes that might occur in Red Wash as a result of subsidence. The nine -hole installation <br />Permit Renewal #6 (04/2014) III -24 <br />