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~ ROBINSON BRICK ~ COMPANY ~ ~ ~ ~ ~ ~ January 7, 1988 ~~I I~~I~~~~~I~~~ ~~~ JAN b iy~g Mined Land Reclamation Division 423 Centennial Building 1313 Sherman Street Denver, CO 80203-2273 M~Ntt, ~nU ~E~AMATION DIVISION Re: Technical Revision to MLRD Permit #80-245, Hogback Mine Dear Sir: This technical revision (TR) will address two items: a change in the sequence of mining and a change in the reclamation plan. The enclosed Map Exhibit D-1, dated December 15, 1987, shows the ~~ of stages of mining. r, l.: yN ~ W Mining activities are currently located in Stage 1. The mining plan as stated in the current plan will not change--mining with concurrent reclamation will continue to the north through Stage 1 and into Stage 3, and then go to the south. With the acceptance of this TR, additional mining will start in Stage 2. The mining in Stage 2 will be in two steps. The first step will consist of the removal of about 30 feet of clay. Mining in this stage will begin at the northern portion of this stage and pro- ceed to the south and will include backfilling of the steeply dipping open-stopes. This step will be concurrent with the min- ing activities in Stages 1 and 3. The second step of Stage 2 will commence after all mining is completed in Stage 3. To illustrate this two-step procedure in Stage 2, refer to the following cross-sections: 1 Figure lA and 1B - These figures show typical cross- ` sections in Stage 2 based on the current topography. Figures 2A and 2B - These figures show the first step of mining where the upper portions of clay will be removed and the waste material will be used to backfill the open stopes. This will leave a highwall ranging from 20 feet to 50 feet; the average being 30 feet. The area being mined in this step consists of rock outcrops and open stopes so that there will be no topsoil to salvage. P.O. Box 5243 • 1845 West Dartmouth • Denver, Colorado 80217-5243 • (303) 781-9002