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• <br />DIVISION OF MINERALS AND GEOLOGY <br />Departmem of Natural Resour[es <br />1313 Sherman 51., Room 215 <br />Denver, Colorado 80203 <br />Phone: 1303) 866-3567 <br />FAX. 13031832-8106 <br />April 10, 1996 <br />To: Dan Hernandez <br />From: Janet <br />Roy Romer <br />Governor <br />lames 5. Lochhead <br />Executive Dneaor <br />Michael B. Long <br />Division Direcbr <br />Re: Seneca R Mine<C`-80-005, TR-30 <br />I have reviewed Seneca Coal Company's application for a reduction in topsoil replacement <br />thickness, TR-30. Seneca Coal Company was required to provide an accurate topsoil <br />balance as a result of Technical Revision No. 28. On January 9, 1996 Seneca Coal <br />Company submitted a Minor Revision, MR-47, indicating the topsoil balance determined <br />on December 1, 1995, would allow for a replacement thickness of 6" of topsoil over 627 <br />acres. The Division requested that this revision be submitted as a technical revision. Mr-47 <br />was withdrawn on 2/2/96 and resubmitted as a technical Revision No. 30 on 2/2/96. <br />Seneca Coal Company referenced a number of reference papers listed on permit pages 9-42 <br />to 9-43 to support the argument that 6 inches of topsoil would be sufficient. I did a card <br />catalog search via CARL at Colorado School of Mines, Colorado State University, Auraria <br />Campus, and Denver Public Library. Extremely few of these referenced papers were <br />available. <br />I was able to read Schuman and Power, 1980, "Plant Growth as affected by topsoil depth <br />and quality on mined lands". This study does not appear to support the claim that 6" topsoil <br />depth would be sufficient to achieve reclamation success at the Seneca II mine. The first <br />major discrepanry was the reseazch was conducted in the Northern Great Plains in North <br />Dakota. I found no information to permit me to extrapolate the papers results to <br />conditions present in Northwest Colorado. The paper provided no information on moisture <br />regime (Average Annual Precipitation), elevation, aspect or orientation of the study plots, <br />or frost free days i.e. growing season length. Another discrepancy, the study considered <br />variable depth of topsoil, (0, 8, and 24 inches of topsoil) overlaying varying depths of subsoil. <br />I believe that the shallowest depth of subsoil was 12" with increments up to 48 inches. This <br />would provide results with 0 inches topsoil and 12 inches subsoil having the least amount <br />of soil treatment. One of the study treatments utilized native grasses Blue grams (Bouteloua <br />gracile) and Side-oats grams (Bouteloua curtipendula). The study concluded that rooting <br />depth depended upon soil depth. This study did not observe roots penetrating into spoil <br />material. Seneca does not lay down a subsoil layer distinct from the topsoil layer. Topsoil <br />is applied directly over spoil. This study might substantiate the claim that 12 inches is <br />suitable or that 12 inches of subsoil overlain with 8 inches of topsoil is satisfactory but I <br />• III IIIIIIIIIIIII III <br />999 <br />STATE OF COLORADO <br />I~~~~ <br />DEPARTMENT OF <br />NATURAL <br />RESOURCES <br />