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III IIIIIIIIIIIII III` 999 57A7E OF COLORA00 • qIC HARD D. LAMM. Govern o~ DEPARTMENT OF NATURAL RESOURCES D. Monte Pascoe, Executive Director MINED LAND RECLAMATION 423 Centennial Building,1313 Sherman Street Denver, Coloratlo 80203 Tel.(30$)Eg29~3567 April 1, 1982 TO: Mike Savage FROM: Jim Pendleton ~,_ RE: Trinidad Bas' 's Pr osed Excess Spoil Pile David C. Shelton Director (Overburden Pile No. 9) Pursuant to youz request, I have reviewed those portions of the Trinidad Basin mine original permit application and supplemental submittal which refer to the proposed excess spoil pile. I forward the following comments for your consideration regarding overburden pile No. 9. I have reviewed Table V-I, included in the original permit application. This table purports to define the material balance at the Trinidad Basin contour strip mine. Unfortunately, insufficient information is provided to allow me to completely understand the derivation of the potentially excess overburden spoil. The table completely defines excavated in-place volumes (coal, overburden and total pit volumes). It then presents a swollen overburden volume, assuming an overburden swell factor of 16~, for which no justification is presented within the permit application nor the supplemental submittal, Finally, it presents a cumulative overburden quantity, which I assume represents the overburden to be deposited, temporarily or permanently, outside the excavated pit areas. I cannot derive the cumulative overburden volumes presented in Table V-1 with the limited information provided. The applicant should amend Table V-1 to provide sufficient information con- cerning working pit volurr>es, in order to clarify the derivation of the cumulative overburden volume figures. The applicant should also provide a justification for the 16% overburden swell. In a mine such as Trinidad Basin, with extensive mining experience, a comparison of previously mined areas and existing spoil and backfill volume relations should allow derivation of a valid empirical overburden swell. Table V-1 also indicates that approximately 88,000 cubic yards of excess spoil will be generated from cuts No. 4, No. 5 and No. 6 within pit No. 4. The applicant proposes to dispose of this spoil in a permanent spoil pile referenced as "Overburden Pile No. 9". Additional spoil piles are temporary in nature and are utilized to achieve approximate original contour during backfilling and reclamation. However, the proposed design for "Overburden Pile No. 9", included within the response to adequacy review, indicates a design volume for the spoil pile of 54,528 cubic yards. The applicant should resolve the apparent 33,972 cubic yard discrepancy.