2018-09-05_GENERAL DOCUMENTS - C1981037

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GEC SEDIMENT LOSS GEC Minerals, Inc., was a mining company started in about 1977 to mine coal on lands leased from The Corley Company in Fremont County approximately 10 miles south of Florence, Colorado. The mining method used was surface strip mining. After initial mining in Section 24, T20S, R70W, the project moved to the W2SE4 Section 19 and W2NE4 Section 30, T20S, R69W affecting less than 100 acres. Two strip pits were developed known as the West Pit and East Pit with the overburden from these pits deposited in a spoil pile known as Chen's Hill, named after the mine manager. In the early 1980s GEC declared bankruptcy. Its mining permit, number C-1981-037, was terminated in 1984 by the State of Colorado, and its reclamation bond was forfeited in 1987. Seven years elapsed before the State initiated the necessary reclamation in 1994, and severe inflation during this time greatly devalued the forfeited bond and reduced the amount and quality of the reclamation performed by the State of Colorado. The main goal of post coal mining reclamation can be summarized as the prevention of erosion and loss of sediment from the affected area. Revegetation, grading of slopes, control of surface water runoff, and sediment ponds are major factors in achieving this goal. There have been no reclamation activities since the 1994 work. There was one sediment pond, designated as Pond A, located adjacent to County Road 92 at the north end of the permit area. This small sediment pond was completely filled with sediment within two years after the 1994 reclamation work. Subsequent State inspection reports have indicated the formation of gullies on the steep slopes of Chen's Hill and the East and West Pits as well as the destruction of the concrete drop structures in the drainage from the East Pit, but the sheer magnitude of the amount of erosion and sediment loss cannot be appreciated by reading of the inspection reports. Therefore, a survey of this area was undertaken to assess the volume of sediment loss and the number of gullies present. Utilizing a Leica GS15 RTK GPS survey instrument system with a nominal precision of plus or minus 0.03 ft., all of the significant gullies in the affected area were located. For this survey a significant gully is defined as being at least 2 feet wide and 1 foot deep. Some of the larger gullies were surveyed in great detail for all major breaklines in their entirety, and survey software was utilized to calculate the volumes. Lesser gullies were located at their midpoints for width, depth, and length in order to calculate the volumes. One gully on the east side of County Road 92 was also surveyed previously in 2015. It is important to note that all of the gullies have formed since the completion of the reclamation work in 1994. RESULTS The gullies in Table 1 were surveyed in great detail and the lost volume was calculated using survey AutoCAD software. The original post reclamation ground surface was assumed to be defined by the present shoulders on both sides of the gullies and the original surface was digitally modeled (ODM). The existing digital model surface (EDM) was subtracted from the original to yield the volume lost.