Impoundment structures hold water, sediments, or other liquid or semi-liquids and are designed to reduce the amount of Total Suspended Solids leaving the mine site. The inspector must determinine if impoundment structures are structurally stable and conform to the design approved in the permit. (VIP 12) They also need to know the water depth, the capacity and sediment load, and if discharges from the impoundment meet applicable effluent limitations. Using the spectral signatures of water or other impounded liquids, image classification techniques can identify certain impoundments as shown in yellow in below. However, caveats exist, including 1) empty impoundments cannot be identified using this technique, 2) ponds filled with wetland vegetation (for example. cattails or sedges) may not be identified and 3) deep shadows and rooftops may be confused with water, resulting in false positives.
Further, it is not possible to determine structural stability, or reliably identify leakage using this technique. These elements require an inspection on the ground. Also, impoundment embankments were not readily identified using the DSMs derived from the satellite imagery.
Impoundments can be mapped and the area can be measured, but at this time, these are the only reliable applications that can be conducted for impoundments.
Impounding structures shown in yellow at the McKinley Mine site.