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III IIIIIIIIIIIIIIII 999 blue ribbon '` coal company blue ribbon ccal company p.o. box 58 delta, Colorado 81416 (303)874-7561 z, ~i April 30, 1985 Susan Mowry Reclamation Specialist Colorado Mined Land Reclamation Division 423 Centennial Building 1313 Sherman Street Denver, Colorado 80203-2273 Subject: File HC-047-81, Mine Bench Monitoring Dear Susan: p41,v ~ i~;~5nn ~ _ , .. ~.1 .p,. ~'IrH 111 rr r:~~1• Stipulation No. 2 of the mine bench technical revision approval document requires that Blue Ribbon submit an acceptable monitoring program to the Division. The monitoring program is to include both slope stability monumentation and piezo- meters in order to verify the portal bench's stability and determine leachate quality. Two rows of slope stability monuments shall be installed. A row of four monuments shall be installed along the outside edge of both the lower and the upper bench resulting in a total of eight monuments. A drawing of a typical stability monu- ment is attached. The stability mounuments shall be monitored for vertical move- ment quarterly for the first year and annually in June for the next two years. The Division shall be advised if any unusual movement is detected in the stability monuments. Three piezometers shall be installed along the inside edge of the lower bench. The piezometers shall be extended through the coal waste approximately five feet into the recompacted colluvium. A drawing of a typical piezometer is attached. The piezometers shall be monitored for water level monthly for the first year and quarterly for the next two years. The design of the bench assumed that the under- drains would keep the phreatic surface below the coal waste embankment. The Division shall be advised if the phreatic surface is detected above the level assumed in the design.