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.. DIVISION OF MINERALS AND GEOLOGY Deparlmenl oI Natural Resources I31 J Sherman SI., Room 215 Denver, Colorado 80207 Phone: 1303) 866-756 FAX: 17031 83 2-81 06 DATE: July 25, 1996 TO: Joe Dudash iii ~iiiiiiiiiiiiiii~ STATE OF COLORADO II~ DEPARTMENT OF NATURAL RESOURCE Roy Romer FROM: Larry Routten ~ Governor dames 5. Lxhhead Execulire Direcra RE: Trapper Mine Topsoils Sampling Michael B. Long Division Director I thought I would summarize the results of Greg's recent topsoil sampling work at Trapper for you. I also have some recommendations as to what I think the results mean and what we should do with them. You, or course, can do what you want with my recommendations. Crop Land Reclamation Greg dug seven holes in three crop land parcels, representing 181.1 acres (one hole per 26 acres). Trapper is supposed to replace 18 inches of topsoil on these areas. Greg's digging found: Avg. depth 19.4" Std. Dev. 6.4" Range 9.5" (14", 19.3" & 24.75") to 28.5" One of the three parcels (CR-93) had an average of 14" of topsoil, based on only two sample holes. This parcel contains 127 acres. We should dig more holes in this parcel to better verify the depth of replaced topsoil. if some cropland parcels actually have less than 18" of topsoil, it is possible that hay production would be limited by the lesser thickness of the rooting zone. I am not familiar with the details of Trapper's vegetation sampling plans associated with bond release applications. However, if sampling data indicates that hay production on reclaimed cropland varies significantly between parcels, further investigation of replaced topsoil depths may be warranted. The Division should make verification of replaced topsoil depths on cropland a priority if and when crop land is reclaimed in the future. Because of the more intensive post mine land use, and the species selection on these area, the need for an adequate rooting zone is probably more critical than on range land at the Trapper Mine.