The Colowyo Mine: A Case Study for Successful Mine Reclamation

By Juan Garcia
Technical Services Manager, Colowyo Mine
Martin Stearns
Senior Environmental Planner, Colowyo Mine

In northwestern Colorado, U.S., coal mining has been a critical part of the culture and economy since the turn of the 20th century. The history of the Colowyo Mine (Colowyo), currently operated by Western Fuels-Colorado, LLC, and owned by Tri-State Generation and Transmission Association, Inc. (Tri-State), dates back to 1908 when the underground Collom Mine operated in the 24-foot-thick Collom coal seam. Starting in 1976, Colowyo transitioned to a highly efficient multiseam dragline and truck-shovel surface mine that today produces approximately 2.5 million tons per year of high-quality, low-sulfur, sub-bituminous coal that is used for coal-fired electrical generation.

The coal produced from Colowyo feeds Craig Station, the second largest coal-fired baseload power plant in Colorado. This power station uses modern emissions control technologies to produce approximately 1300 MW, or one third of the coal-fired electricity generated in Colorado. The electricity generated at Craig Station is an important component of the Tri-State portfolio of power generation. Tri-State is a not-for-profit wholesale power supplier to 44 electric cooperatives and public power districts serving 1.5 million members throughout 200,000 square miles in Colorado, Nebraska, New Mexico, and Wyoming.

The state of Colorado is known nationally for its snow skiing, big game hunting, fishing, hiking, sightseeing, rafting, and many other types of outdoor recreation—an industry that yields $13.2 billion in state revenue each year.1 Colorado has 53 mountain summits in excess of 14,000 feet (4267.2 m) and vital water derived from the Colorado watersheds sustains municipalities and agricultural industries in vast areas of the arid southwestern U.S. In recent years, the state’s population has grown at twice the national average. Thus, meeting increasing energy demand in Colorado must be done in a way that minimizes impacts on the natural world. In line with such values, Colowyo practices responsive resource extraction with minimized harm to the environment and a dedication to reclaiming the land to a beneficial use that is comparable to or better than the land use that existed prior to mining.

The Colowyo mine has provided coal to produce reliable, cost-effective electricity for nearly four decades while minimizing the environmental footprint.

The Colowyo mine has provided coal to produce reliable, cost-effective electricity for nearly four decades while minimizing the environmental footprint.

Colowyo is a mature mining operation composed of the active South Taylor Pit, the fully mined out West Pit undergoing reclamation, and substantial areas that have already undergone successful reclamation. Reclamation begins as soon as mining in a particular area is finished, minimizing the environmental impact and footprint of the mine at any one time.


Colowyo’s reclamation objective is to restore the mined area to a land use capability equal to or better than the land condition that existed prior to mining. This commitment begins with the Tri-State Board of Directors, which has made reclamation projects a priority and has dedicated the necessary resources to ensure completion at or above industry standards. The desired end results of all reclamation practices are to stabilize the soil, maintain hydrologic and vegetation resources, and restore the approximate original contour of the mined area. Ultimately, the goal is to return the mined areas to a condition that can support its original use as rangeland and the watersheds to their approximate pre-mining character. In general, the long-term appearance and usefulness of the mined area will be similar to that which would have been encountered prior to any mining.

Land currently undergoing the reclamation process at Colowyo

Land currently undergoing the reclamation process at Colowyo

Colowyo has worked cooperatively through the years with Colorado State University, the University of Idaho, the Colorado Division of Reclamation, Mining and Safety (CDRMS), the Colorado Department of Parks and Wildlife, and the U.S. Bureau of Land Management to develop innovative reclamation techniques, including the following practices:

  • Hauling topsoil immediately from the salvage area to the final reclamation surface to preserve soil nutrients and seed sources within the topsoil;
  • Chisel-plowing the newly spread topsoil to break up soil compaction to help prepare an optimum seed bed;
  • Using a rangeland drill to plant a diverse mix of shrub/grass/forb seeds below the soil surface;
  • Seeding only in the fall so the seed lies dormant through the winter and germinates in the spring to take advantage of snow melt precipitation and the spring growing
    season; and
  • Placing discontinuous contour furrows in the topsoil when seeding to capture and hold precipitation to sub-irrigate plant root zones.

The Colowyo site has won numerous reclamation awards for outstanding professionalism and performance in conducting mining and reclamation operations, use of innovative approaches in addressing reclamation problems, successfully obtaining environmental permits approving work in several excess spoil disposal fill areas, supporting longstanding efforts to reestablish shrubs on reclaimed mined land through the testing of various seeding and planting techniques, and innovative topsoil replacement methods to enhance shrub establishment and develop beneficial and diverse wildlife habitat. In fact, since 2010, Colowyo has received six Colorado Mining Association Environmental Stewardship and Pollution Prevention awards and three Colorado Division of Reclamation, Mining and Safety Excellence in Reclamation awards.


The reclamation process at Colowyo begins with the salvage of topsoil before mining commences. Topsoil salvage ensures that soil rooting material, with the associated nutrients and organic matter, is transferred back to the land after mining has ended. Thus, during reclamation much of the area that is temporarily disturbed by mining is covered by soils that provide an excellent source of plant growth media. These soils are deep, dark, and loamy with physical and chemical properties well suited for revegetation. Topsoil is either directly hauled from salvage areas or hauled from topsoil stockpiles and uniformly distributed over the entire regraded landform.

Backfilling and regrading operations, also important during reclamation, are conducted according to the reclamation plan approved as part of the CDRMS permit to mine. These operations return the surface topography to the approximate original pre-mining contours. Post-mining drainages are constructed to reestablish stable drainage basin areas, land profiles, and channel configurations. These drainages are designed to ensure the channels and associated drainage basins remain stable and are not prone to erosion. Contour ditches may be placed in drainage basins to route surface flow to rock-lined channels. These are especially important immediately after topsoil placement and seeding while vegetation is becoming established to prevent or minimize erosion of the topsoil resource.

Diverse vegetation types are selected based on the post-mine land use approved in the mining permit. Since Colowyo’s post-mine land use is rangeland, the reclamation areas are seeded with native species of grasses, forbs, and shrubs to reestablish vegetative communities such as sagebrush, juniper, grassland, and riparian. The eventual size and location of these various post-mine vegetative communities are based on factors such as surface topography, elevation, and the direction the landform is facing. Variable depths of topsoil may be replaced in targeted areas to best meet vegetative requirements. Studies have shown that establishment of some shrubs is enhanced by the placement of shallower (4–8 inches) topsoil depths. This potentially precludes the establishment of thick stands of grasses that can out-compete shrubs and forbs for soil moisture and nutrients. Conversely, thicker (12–18 inches) layers of topsoil can enhance the establishment of predominantly grassland communities.


Reclaimed mine lands are becoming an increasingly important land use component within the Colowyo mining area. Over 2400 acres of reclaimed land, which continues to expand, provides year-round habitat to local birds and both small- and big-game wildlife populations, including small mammals, birds of various species, elk, mule deer, and pronghorn antelope. It is quite common to observe young animals and birds of every species that were born on or in the near vicinity of the reclaimed mine lands.

Native elk on Colowyo reclaimed mine land

Native elk on Colowyo reclaimed mine land

This final surface configuration provides home and shelter for all wildlife. The regrading and revegetation plan reestablishes diverse food sources, establishes escape cover, creates south-facing slopes that do not accumulate deep snow levels, which aids wintering animals, and creates small drainages and water catchment areas where stock ponds and small catchments provide necessary water.

Ultimately, there are two measures of successful mine-land reclamation: full reclamation bond release and the establishment of the targeted post-mine land use. Colowyo has received full bond release on 987 acres by achieving the regulatory-mandated standards set by the CDRM. These bond release standards include requirements for vegetative diversity, density, and production, as well as soil stability and essential hydrologic function. True vegetative success is ultimately measured by the ability of the vegetation to be self-sustaining and flourish under all natural weather conditions without the aid of any artificial intervention. All bond-released areas readily meet this stringent criterion.

The newly reclaimed rangeland is composed of the two primary subcomponents: livestock grazing or grazing land and wildlife habitat or greater sage grouse (GSG) brood-rearing habitat. GSG habitat preservation or reestablishment was of particular concern since the bird species had been identified as potentially eligible for Federal Endangered or Threatened Listing status. On 22 September 2015, the U.S. Department of the Interior determined that the GSG does not require Endangered Species Act protection, but regardless of that decision, Colowyo will continue to reestablish quality wildlife and grouse habitat. Livestock grazing has always been precluded at Colowyo on reclaimed areas to ensure that vegetation is well established. In the future, livestock grazing will be introduced to coincide with regional land use.

Colowyo will continue to reestablish grouse habitat during reclamation.

Colowyo will continue to reestablish grouse habitat during reclamation.

Indigenous wildlife, such as elk, mule deer, and pronghorn antelope, have already discovered the abundant food resources and secluded habitat available on the reclaimed mine areas and have established either seasonal or year-round residency. Sage, sharptail, and dusky grouse; songbirds from many diverse species; hawks, eagles, owls, and falcons; and many other bird species have already reestablish occupancy in the reclaimed areas as the vegetation has matured. Small mammals such as chipmunks, ground squirrels, cottontail rabbits, jackrabbits, weasels, voles, and mice all find refuge and home in the mined reclamation areas.

Taken collectively, these many indicators point to a true reclamation success story that Colowyo is proud to be a part of and glad to share. Colowyo has always been open in sharing best reclamation practices with other coal mining companies, state and federal regulatory agencies, and academia to ensure that healthy and self-sustaining post-mine environments exist long after mining has ceased. Colowyo continues to work toward building a proud reclamation legacy for all generations to use and enjoy.


  1. Colorado Office of Economic Development. (2015). Tourism & outdoor recreation,

The lead author can be reached at


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