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C~ AMENDMENT TO FINDINGS DOCUMENT COLOWYO COAL COMPANY COLOWYO MINE The original findings document for the Colowyo Mine approved the construction of an excess spoil fill in Streeter Canyon as an experimental practice. Specifically, it approved the construction of the fill in 100 foot end-dumped lifts, did not require the construction of durable rock under drains, and allowed for terraced benches spaced at 100 foot vertical intervals. It is the Division's position that the Streeter excess spoil fill need not be an experimental practice. Rule 4.09 of the Regulations of the Colorado Mined Land Reclamation Board for Coal Mining detail the environmental design and performance standards that must be met when disposing of excess spoil and underground development waste. This rule is very specific in detailing the standards that must be met when constructing an excess spoil fill. Colowyo's proposed spoil fill varied from the design standards in three instances; construction of lifts by end dumping, and in excess of 4 foot lift thickness, not constructing durable rock under drains, and the vertical distance between terraces exceeds 50 feet. Rule 4.09.1(3) does allow for an alternative to the generic design standards. Specifically, Rule 4.09.1(3) allows for construction differing from the design • standards if such alternatives are as environmentally sound and structurally stable as those fills built pursuant to 4.09. During the course of the original review two engineering studies detailing the structural stability of the fill .were submitted to the Division. These studies were conducted by CTL Thqmpson, Inc. and demonstrated that the fill was as structurally stable and environmentally sound as fills built as required under the design standards. At the time of the initial review, the Federal Office of Surface Mining had not approved 4.09.1(3). Given this, Streeter fill was submitted as an experimental practice and approved as such. The Division felt at the time of review that this request was merely a fill structure submitted with alternative design specifications and not an experimental practice. In addition, the Mined Land Reclamation Board stated in it's approval of the Streeter fill that when the alternative design regulation is approved, the construction techniques for the Streeter fill be approved as such. Rule 4.09.1(3) has been approved by the Office of Surface Mining and is now a part of the permanent Colorado Program. Monitoring to date has shown the fill is stable and not saturated. Given this, the Division is hereby changing the status of the Streeter fill from an experimental practice to an excess spoil fill designed and constructed under the alternative design standards set out in Rule 4.09.1(3). All monitoring requirements for the fill will remain as originally approved to insure the stability requirements of Rule 4.09 are met. In addition, this change in status does not release Colowyo from any liability or mitigation requirements in the event of a failure. • ML/ddt 1290E