In tandem with closing depleted areas at its Coal Hollow Mine, Alton Coal applied for a permit to begin new operations on an adjacent, federally owned parcel of land. Utah’s Division of Oil, Gas, and Mining (DOGM) requires that a revised mine plan meet certain regulations for containing stormwater runoff and controlling sediment. In particular, ditches must be sized to convey runoff at specific rates and sediment impoundments must meet capacity requirements. In this case, the revised mine plan addressed both the area of the mine being prepared for closure and the proposed expansion.
To meet DOGM’s detention-volume requirements for sediment control, Barr developed a hydrologic model and used it to (1) analyze the 400-acre watershed area that could be affected by past mining disturbances and (2) size ditches, culverts, and a sediment storage basin. The resulting sediment-management plan incorporated efficiency by using existing infrastructure where possible.
We started by conducting a drone survey of the watershed to obtain accurate topography, and then evaluated the most efficient routes for diverting runoff from undisturbed upgradient areas and around the mining operations. Bypassing the mined area prevents the water from picking up possible contaminants while reclamation activities are taking place.
A separate system collects runoff in the disturbed mine area and conveys it to a sediment impoundment structure, or storage basin. The basin was sized to contain the runoff volume of a 10-year, 24-hour storm, and features a decant structure that allows settling of sediment and eventual controlled release of runoff.
After the ditches and decant structure were built, we performed another drone survey to verify the system’s capacity and update as-built drawings for Alton Coal’s permit application. A hydrology and runoff-control report and accompanying reclamation design plans were part of the larger permit package submitted to DOGM.
Barr also used drones to survey the volumes of multiple pit and fill areas, which was critical for managing both the final mining operations and new reclamation activities taking place at the site.
In addition to permitting assistance and drone surveys, our services at Coal Hollow Mine encompassed a bond release; environmental compliance inspections; engineering assistance with mine planning, geotechnical investigations, and hydrologic and hydraulic analysis; and operational evaluations to improve mine production efficiency.