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~I <br />TETRATECH RMC <br />January 28, 2003 <br />Mr. Jeff Gregg <br />Hall-Irwin Corporation <br />P.O. Box 2150 <br />Greeley, Colorado 80632 <br />Re: Hall-Irwin Corporation, The Shores Resource, Town of Firestone, Colorado, Stability <br />Analysis as Required by the Division of Minerals and Geology; Tetra Tech RMC <br />Job No. 80-0636.026.04 <br />Dear Mr. Gregg: <br />This letter has been prepared to address Mine Land Reclamation Board (MLRB) Construction <br />Materials Rule 6, Section 4, Subsection 19, Exhibit S -Permanent Man-Made Stmctures (6.4.19, <br />Exhibit S) for the above-referenced proposed aggregate mine. <br />The proposed mine will occupy the property located in Section 1 and Section 2, Township 2 North, <br />Range 68 West of the 6th Principal Meridian in Weld County, Colorado. The site is immediately <br />north of Weld County Road 48, west of Weld County Road 23, and east of Weld County Road 9'/<. <br />The St. Vrain River is to the north of the site. Land use in the area is mostly agricultural and rural <br />residential with newer encroaching residential and commercial developments. Numerous gas wells <br />are present in the area. <br />The Amended Mining Plan (attached for reference) for the project is to mine the site in a total of nine <br />phases, where Phases 1 through 3 have already been completely mined. Phases 4 through 9 range <br />from approximately nine to 58 acres in area. Two slurry walls will be constructed: one around <br />Phases 4, 5, 6 and 7 and the second around Phase 8 and 9. For our analyses, we have assumed that <br />the mine highwalls on the perimeter of each pod will be no steeper than 0.5:1 (horizontal to vertical). <br />Overburden stockpiles maybe placed on the perimeter of the mined areas. Phases 4 through 9 will <br />be reclaimed as lined ponds. Phases 1, 2 and 3 will be reclaimed as wetlands. <br />GEOLOGIC STRATA <br />The mine site is located in the alluvial valley of the St. Vrain River. Geologic mapping by Colton <br />(1978)1 indicates the mine will be in the Piney Creek Alluvium. The southeast part of the property is <br />in the Broadway Alluvium and will not be mined. The mapping indicates the bedrock underlying the <br />Colon, R.B., 19'78, "Geologic Map ojthe Boulder-Ft. Collins-Greeley Area, Colorado," USGS Map I-SSSG. <br />1900 S. Sunset Street, Suite I -F, Longmont, CO 80501 <br />Tel 303.772.5282 Fax 303.665.6959 <br />www.ttrmccom <br />