GENERAL30475

• Permit No: C1981019
• IBM Index Class Name: General Documents
• Doc Date: 5/4/2007
• Doc Name: Proposed Decision & Findings of Compliance for PR2
• Permit Index Doc Type: Findings
• Media Type: D
• Archive: No

4.09.2.
In this regard, the Division approved the fills as disposal areas for excess spoil [Rule 4.09.1(1)]. The
Division approved fill designs. These designs aze found in Exhibit 19 of the Permit. Construction
approved was by end dumping excess spoil material in 50- to 100-foot horizontal lifts. Prior to
construction of the fills, all topsoil was removed from the azeas as well as clay subsoils beneath the
toe of the West F'it fill. Rock underdrains are constructed in natural drainage bottoms from the toes to
the heads of the fills. The fills are completed with 3h:ly outslopes and with 12-foot-wide terraces
constructed at approximately 100-foot intervals. Topsoil replacement and seeding completes the
reclamation. A series of survey monuments and groundwater piezometer wells are monitored
quarterly, with results reported to the Division.
Based upon the geotechnical analyses prepared by CTL/Thompson Inc. (September 5, 1991 and
Apri127, 1992) <trrd submitted by the Operator and based upon monitoring data from the Streeter Fill
at the Colowyo 1`dine, the Division found that the proposed W est Pit and Section 16 excess spoil fills
were designed in compliance with the requirement of Rule 4.09.2. Specifically, the fills were
designed to attai n static safety factors in excess of 1.5; material densities will be adequate to prevent
mass movement; end dumped lift placement and gravity segregation of spoil materials will preclude
the formation of deleterious voids within the fills; and no contamination of the rock underdrains
would occur [Rule 4.09.1(2)].
The use of vegetation and organic material as mulch or as an amendment to topsoil to control
erosion, promote growth, or increase moisture retention was approved [Rule 4.09.1(4)]. The
locations of the excess spoil fill disposal areas were approved [Rule 4.09.1(6)]. The use of terraces in
order to control erosion and enhance stability was approved [4.09.1(9)].
Two additional valley fills and two temporary overburden stockpiles are proposed for the South
Taylor area in Pl'2-02. The permanent fills are the West Taylor Fill and the East Taylor Fill. The
temporary overburden stockpiles are TS West and TS East. The information on the new valley fills
is contained in Permit Volume 12 in Sections 4.09, 4.10, 4.11, 4.12 and 4.13.
The West Taylor fill is a valley fill that will be located in the upper west fork of Taylor Creek. It will
contain approximately 10 million cubic yards of material from the initial box-cut for the South
Taylor Pit. The fill will have adurable-rock drain that will be build by gravity sorting of dumped
overburden materials. The initial construction of the fill will be accomplished by wing-dumping
material to establish the base of the fill followed by end-dumping of material to complete the fill.
Lifts of no more than 100 feet are proposed for the West Taylor Fill. Colowyo proposes to use
terrace ditches to divert water off of the face of the fill and to the relief drains on the side.
Additionally, 100-yeaz diversion ditches will route clean-water around the fill. Upon completion of
the West Taylor Fill the area will have the topsoil replaced and it will be revegetated per the
approved reclamation plan.
The East Taylor 1?ill is a valley fill that will be located in the upper east fork of Taylor Creek. It will
Proposed Decision and Findings of Compliance 4 May 2007
Permit Revision 02 Page 47