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TETRA TECH RMC <br />May 12, 2004 <br />RECEf VED <br />JUN 15 2004 <br />Mr. Mike Refer <br />Division of Minerals & Geology <br />Aggregate Industries, Inc. <br />West Central Region <br />1707 Cole Boulevard, Suite 100 <br />Golden, Colorado 80401 <br />Re: Tucson South Proposed Gravel Mine Slope Stability Analysis; <br />Tetra Tech RMC Job No. 19-3919.019.00 <br />Dear Mr. Refer: <br />This letter has been prepazed to address the Mine Land Reclamation Boazd (MLRB) Construction <br />Materials Rule 6, Section 4, Subsection 19, Exhibit S -Permanent Man-Made Structures (6.4.19, <br />Exhibit S) for the proposed Tucson South aggregate mine. This letter describes the project and <br />slope stability calculations carved out to evaluate the minimum distance between the edge of <br />mining and adjacent structures to avoid damage to the structure. <br />The proposed site will occupy approximately 289.3 acres in the South Half of Section 1 and <br />Northwest Quarter of Section 12, both within Township 1 South, Range 67 West of the 6th <br />Principal Meridian in Adams County, Colorado. The site is in the alluvial valley of the South Platte <br />River which meanders around the southeast and east sides of the proposed mine. Colorado <br />Highway 7 (160th Avenue) is south of the main part of the mine. It divides the main east and west <br />cells from the small southwest cell. Land use in the azea is mostly existing gravel mining, <br />agricultural, suburban residential, and rural residential. The City of Brighton lies one half mile to <br />the east. <br />The Mining Plan (attached) for the project shows the mining azea, test holes, and slurry wall <br />alignment. The slurry wall will be constructed azound the perimeter of the main east and west cells <br />which will be reclaimed as two ponds, all within the slurry wall perimeter. The small southwest cell <br />will be mined first by dewatering or dredging. The cell will serve as storage for silts from the <br />aggregate plant and will be reclaimed as farmland. <br />This report lists minimum safe setbacks from structures based on stability calculations. Actual <br />setbacks maybe greater due to permit limitations, zoning requirements, construction issues, <br />agreements with owners, extent of economically mineable aggregate, or other issues. <br />1900 S. Sunset Street Su¢e I -F, Longmont CO 80501 <br />Tel 303.772.5282 Fax 303.665.6959 <br />awnv.ttrmccom <br />