2004-08-02_REVISION - M1999021 - Laserfiche WebLink

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CERTIFIED MAIL - Returu Receipt No. 7002 0860 0007 5578 7578 July 30, 2004 RECEIVED AGGREGATE ~ Mr. Carl Mount INDUSTRIES Division of Minerals and Geology AUG 0 2 2004 l/ 1313 Sherman Street, Room 215 Denver, CO 80203 /,/ Uiuision of Minerals and GeoloAY // Re: Permit No. M-1999-021 -Stegner Farms -Technical Revision Request ~/~ -O `f ~ Dear Carl: /~GS ~~ Aggegate Industries (AI) submits this letter, the enclosed drawing, and a check in the amount of $188.00 as a request for a technical revision to the above-referenced permit. The revisions proposed in this request are as follows: Installation of perimeter goundwater drainage system. During neighborhood meetings held by AI, neighbors expressed a continuing concern with potential impacts to goundwater levels after AI completes mining and is released from reclamation responsibility. While the original permit application documents proposed installation of a drain system around the exterior perimeter of a slurry wall around the excavation area prior to mining, final guidelines proposed in technical revisions to the application and approved by the Division provided for goundwater monitoring and subsequent installation of the drain based on performance standards for any mounding effect. Although the triggering events in the permit conditions had not been encountered, AI ageed during its neighborhood meetings to install a perimeter drain around the slurry wall prior to moving from the site and proceeded to develop the design and location of the drain in consultation with the neighbors and land owner. The final drawing incorporating the drain was completed July 26 and is submitted herewith as a part of this technical revision request. The location and design ofthe drain delineated on the enclosed, revised reclamation drawing will intercept goundwater from the upgadient side of the slurry wall on the north and west boundaries of the property through a perforated 8-inch pipe when goundwater level elevation increases to within two feet or less of the Bound surface elevation. The perforated pipe will then be transitioned to a solid pipe along the southern boundary of the property until it reaches a point approximately 600-feet from the east property boundary, at which point the solid pipe will be transitioned again to a 6-inch perforated pipe and set in a sand and gavel recharge trench at an elevation approximately 2.5 feet below the Bound surface. This re-charge area will continue along the downgradient side of the slurry wall for 600 feet. The proposed drain was initiated in an attempt to mitigate post-mining neighbor concerns, Aggregate Industries West Central Region, Inc. P O Box337231 Greeley Colorado 80633 36171st Avenue Greeley Colorado 80634 Telephone (970) 353-2005 Facsimile (970) 378-6856 An Equal Opportunity Employer