2005-06-24_REVISION - M2000016 (13)

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~1PARGE NORTH AMERICA AGGREtiATES, CONCRETE !L ASPHALT The drill hole records in electronic form were emailed to Kathleen Sullivan at the above address on May 5, 2005. Memo Item 8: Since mush 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 maintain 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" boumdaries a minimum of 400 feet from the top of the bank of the river. Exhibit C and Exhibit F have been revised to reflect boundaries a minimum of 400 feet from the top of the bank of the river. The original delineation of mining cells which reflect the 200-foot offset from the shoreline of the river also remain, with a note indicating that areas closer than 400 feet from the top of the riverbank will be mined upon approval of the bank stabilization, or flood analysis and flood control, plan. Rule 6.4.5 IiXH1BIT E -Reclamation Plan 8. Memo Item 9: The response by the Applegate Group qualitatively addresses anticipated impacts to eixisting wells only, and not to overall hydrologic balance (including impedance to ground water flow) or other structures such as homes, including potential basement flooding. The response also draws conclusions regarding the impact of the silt ponds based upon the groundwater modeling by AMEC Earth & Environmental, Inc. (AMEC). However, the hydrologic effects of creating silt storage cells were not modeled and quantifzed. The only mitigation measure offered is to possibly slightly deepen a natural drainage if Well Permit No. 163521 sees a ground water elevation increase "coupled with a physical injury to the well. " Please assess the potential impact of the silt storage ponds and commit to specific mitigation measures and trigger points for implementation of the mitigation measures. This also relates to comments in Exhibit G -Water Information section of this memo. See'comment 9 below. Rule 6.4.7 EXHINIT G -Water Information 9. The maps provided in the "Groundwater and Surface Water Evaluation "report prepared by AM1s'C (AMEC report) are too small of a scale to evaluate the model output. The applicant must provide a larger depiction of the ground water model, including maps on the scale of those submitted as Exhibits C and R Additionally, the Division needs a model that shows ground and surface water impacts ~~ For each cell during dewatering, t~ For each proposed clay-lines pit during dewatering and once lined, ~~ For each of the proposed silt storage ponds during dewatering, as they are filled, and once completely filled. The model should represent actual planned operations, including maximum potential disturbance to the hydrologic balance that may occur as a result of these mining operations; for LAFARGE NORTH AMERICA INC. 'Lafarge Construction Materials 10170 Church Ranch Way, Suite 200, Westminster, Colorado 80021 Telephone: (3031657-4000 Facsimile: (303) 657-4037