2005-07-26_REVISION - M2000016 - Laserfiche WebLink

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INTEROFFICE MEMORANDUM COLORADO DIVISION OF MINERALS AND GEOLOGY 1311 Sherman St., Rm. 215 Denver, CO 80203 TO: Gregg R. Squire <' Q ~_ __ FROM: Kathleen L. Sullivan, P.E. ~ ~~ SUBJECT: M-2000-016, Lafarge West, Inc.: Riverbend Operation, AM-01 Adequacy Review No. 4 DATE: July 25, 2005 CC: Carl Mount, DMG (via e-mail); Kate Pickford, DMG (via a-mail) This memo contains adequacy review comments to the applicant's June 24 (Second) and a portion of the July 12, 2005 (Third) adequacy responses to the Division's hydrology review of the Lafarge West, Inc.: Riverbend Operation 112(c) Amendment (AM-01) Application, File No. M-2000-016. The geotechnical comments are forthcoming. I have directed my comments to the applicant. The applicant may contact me with any questions-at-(-303}866-4060: - - Rule 6.4.3 EXHIBIT C -Pre-mining and Mining Plan Map(s) of Affected Lands Response 1 of the June 24, 2005 "Second Adequacy Review Response," states that all maps "have been modified to remove references to discharging to either the Lupton Bottom Ditch or Big Dry Creek." However, the new Mine Plan maps, Exhibits C2-C4, drawn by Tetra Tech RMC, still show "dewatering discharge" routed to these waterways. Please amend the maps to remove any incorrectly located symbols and to reflect discharge only to the South Platte River. 2. Affected area has not been identified on the new Mine Plan maps. Please revise the maps to identify the affected area, per Rule 6.4.3(d). Please insure that all disturbances, including topsoil/overburden piles, are within the affected area boundaries. As noted in the prior adequacy review, "Since much of the site is located within the 100-year flood plain of the South Platte River and a flood analysis and flood control plan have not been submitted, the mining operation must remain a minimum of 400 feet from the top of the riverbank. Both the Exhibit C -Mining Plan maps and the Exhibit F -Reclamation Plan maps must be amended to show the disturbance/affected area and 'mining limits' boundaries a minimum of 400 feet from the top of the bank of the river.° This means that all topsoil/overburden piles must be at least 400 feet from the top of the bank of the river as well. Please revise the maps accordingly. 3. Several topsoil/overburden stockpiles that flank Big Dry Creek and the Lupton Bottom Ditch are within the 100-year flood plain. Since they are near the edge of the flood plain, a full flood analysis may not be necessary to demonstrate they would not