2003-02-04_REVISION - M1998013 - Laserfiche WebLink

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TETRA TECH RMC February 3, 2003 RECEIVED FEB 0 4 2003 Mr. Jeff Gregg Hall-Irwin Corporation P.O. Box 2150 Greeley, Colorado 80632 Division of Minerals and Cealogy Re: Hall-Irwin Corporation, The Shores Resource, Town of Firestone, Colorado, Review of Revised Amended Mining Plan in Regards to Structures within 200 feet of Mining, Tetra Tech RMC Job No. 80-0636.026.04 Dear Mr. Gregg: Previously, we performed stability analyses with regards to structures located within 200 feet of the Shores Resource. The results of our analyses were summarized in our letter of January 28, 2003. Subsequently, Hall-Irwin made revisions to the mining plan with regards to future oil/gas wells at the site. The minor revisions involve local changes in the location of the site slurry walls as well as local revisions of the areas to be mined. The revisions were required to allow areas for future oiUgas wells near the mine, The mining will not encroach within 150-feet of the proposed oiUgas wells. The minimum setbacks from structures within 200-feet of the mine in the revised plan are consistent with the setbacks used in our previous analyses. In light of this, the revised mining plan should not pose a hazard to nearby structures. LIMIATIONS Our review and previous analyses are based on regional geologic mapping, present mining plans, bore hole data, and stability analyses using typical soil strength parameters. Should the mining plans change or subsurface conditions vary from those portrayed in this letter, we should be contacted in order to re-evaluate the potential affects on man-made structures. Please call with any questions or comments. Sincerely, TET~RA/T~ CH RMC Gary Linden, R.G. Engineering Geologist cc: Danna Ortiz, Tetra Tech RMC (with Attachments) N \06]6 026\00\xstabl\Shwes SUbiliry Rcviud.ltr.doc 1900 S. Sunset Street. Suite I -F, Longmont, CO 80501 Tel 303.772.5282 Fax 303.665.6959 w~wv.ttrtnccom