PERMFILE139435

• Permit No: C1981019
• IBM Index Class Name: Permit File
• Doc Date: 6/14/1985
• From: MLRD
• To: COLOWYO COAL CO
• Section_Exhibit Name: Gulch A sed pond
• Media Type: D
• Archive: No

-2-
• 3. Vegetation: The dominant vegetation on the pond site consists almost
entirely of Basin Wildrye Elymus cinereus with a scattered understory of
' Big Sagebrush Artemisia tridentata and a few other minor species.
4. Land Use: Current land use in the area is coal mining on the adjacen'~
ridge, wildlife habitat, rangeland, and pasture land along the floodplain
of Good Spring Creek.
Pond Design
Hydrology calculations for the Gulch A Pond were done by Tipton &
-..Kalmbach, Inc. and subm.itted.to the Division in the original permit application.
During the Division's adequacy review of the permit, some specific concerns in
the methodology for hydrology calculations ~,vere noted and included in the
Division's adequacy letter to Colowyo. Copies of the data from the permit
application and copies of the concerns of the Division along with Colowyo's
response and data backup taken from Vol. 8 of the Co]owyo Permit, are included.
In addition to the changes proposed in Vol. 8, Colowyo feels the
fo]lowing changes in original design are necessary from both an operational
and regulatory compliance standpoint:
• 1. The do+~nstre~m side of the dam will be cov=red with rip rap to protect
the tie of the dzm from the possibility of Good Spring Creek cutting in
that direction.
2. The width of the dam is increased to accomodate an access ramp and increasa
the top width to accommodate future dredging operations. The increased
width will also ensure a more stable structure.
3. The invert is raised to 6613.8 to fulfill the regulatory requirement of a
nonclogging dewatering device no lo~~~er than the maximum sediment storage
volume. Colowyo has committed to remove sediment at 60% of the predicted
3 year sediment level. The 60o removal elevation is 6613.8.
4. The principal spillway is raised to 6619 to provide storage for both the
10 year 24 hour event and sediment volume at the 60% removal of the 3
year sediment yield.
5. A ':ey cut is included.
A summary of changes in design is presented in Table 2. A plan view
of the pond layout is shown in Figure 1, and cross sections of the dam and
emergency spillway are shor~m in Figure 2.