One of the principal requirements regarding backfilling and grading is to return disturbed lands back to their approximate original contour. (VIP 6) The final land surface must be stable, not prone to landslides or erosion and blend into the surrounding natural topography. Finally, the land surface must be compatible with the intended postmining land use. The inspector must evaluate whether backfilling and grading operations meet the postmining topography approved for the permit. Slope steepness, direction, drainage intensity, and slope stability are parameters which must be evaluated by the inspector. To generate up-to-date contours, recent high resolution stereo satellite imagery can be used to derive a Digital Surface Model (DSM). Using appropriate GIS tools, a minimum contour interval of 2 meters (6.5 feet) can be generated from currently available satellite imagery. The figure below depicts contours generated from stereo satellite imagery that can be evaluated in a GIS and compared to the approved the post mine contour map. These maps provide a quantitative tool to help the mine operator correct slope contour issues if they exist.
Elevation Counters from stereo satellite imagery overlaid on a Digital Surface Model at the McKinley Mine site.