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-LiE (IF [CJ L CJF Lf?p 4iC ~c4pp LVI1' ~. .. ... DEPARTMENT OF NATURAL RESOURCES D. Mome Pascoe. E,<ecu uvr Dire nor n1 L'~ ED L.~~ D R ECL.4:11.4T1(1'~ 423 Centennial Building. 7373Sherman Street Denver, Colorado B02D3 Tel.(3D3) B?-3567 ~~ April 1, 1982 David C. Shelton Director , ~t~G~~ ~,u~,~. ~~ TO: Mike Savaoe ~Lt' FROM: Jim Pendleton RE: Trinidad Bas' 's Pr_osed Excess Spoil Pile (Overburden Pile No. 9) Pursuant to your request, I have reviewed those portions of the Trinidad Basin mine original permit application and supolerrental submittal which refer to the proposed excess spoil pile. I forward the following com;nents for your consideration regarding overburden pile No. 9. I have reviewed Table v-1, 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 oi~erburden I • 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. Finallu, it presents a cumulative overburden avantity, 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-I with the limited information provided. SA=G ~' The applicant should amend Table V-1 to provide sufficient information con- cerning working pit volumes, in order to clarify the derivation of the cumulative overburden volume fioures. 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 pre viousl_y mined areas and existino spoil and bar>cfill 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 wilt be generated from cuts No. 9, No. 5 and No. 6 within pit No. 9. The applicant proposes to dispose of this spoil in a permanent spoil Wile referenced as "Overburden Pile No. 9". Additional spoil piles are temporary in nature and are utilized to achieve approximate original contour during backfilling and recIamati on. However, the proposed design for "Overburden Pi le. NO. 9", . included within the response to adeouacy review, indicates z design volume for f the spoil pile of 59,528 cubic ya_*ds. The applicant should resolve the l„~ apparent 33,972 cubic uard discrepancu.