• Hydrologic Evaluation of Topsoiling for Rehabilitating Black Mesa Coal Mine Lands

      Postillion, Frank G.; Bureau of Land Management, Las Vegas, Nevada (Arizona-Nevada Academy of Science, 1980-04-12)
      Two experimental paired watersheds on Black Mesa Mine, in the Four -Corners region of Arizona were compared by several hydrologic variables in order to determine their relative capabilities for vegetative reestablishment. From July 1977 to the present, precipitation ranged from 5 to 7 inches; runoff was 7 times lower on the topsoiled watershed. Because of its structureless nature, the non-topsoiled watershed tended to crust and seal the surface. In general, the sediment yield was lower on topsoiled spoils; however, increased sediment yields were observed during intense storms, possibly reflecting the fact that the topsoil was not anchored to the underlying spoils. The non-topsoiled watershed was found to have a higher soil moisture at wilting point (13.8%) and high soluble salts (3,000-5,000 ppm), making water unavailable at higher suctions. The range of available water was higher on the non-topsoiled watershed. Tests indicated that most soil moisture water storage results from winter frontal storms of long duration. A vegetation survey indicated a more successful rate of seedling establishment (8.1 plants/m) on the topsoiled watershed, but with a high subsequent die off rate due to drought conditions. Mechanical treatment of and chemical amendments to spoils and topsoils are discussed. It is concluded that the practice of topsoiling will greatly enhance revegetation of mine spoils in arid environments. If it is necessary to directly revegetate spoil materials without topsoiling, salt and drought tolerant species are recommended.