PERMFILE133112

• Permit No: C1989074
• IBM Index Class Name: Permit File
• Doc Date: 12/11/2001
• Section_Exhibit Name: 4.05 Hydrologic Balance
• Media Type: D
• Archive: No

• 4,05.9Imnoundments
It is desired by both the landowner and the operator that the sediemnt pond be left as a
permanent impoundment after reclamation. It will be valuable in the post-mining use of
rangeland grazing. All items necessary to demonstrate that the pond meets applicable
requirements are listed below:
1) The quality of the impounded water is acceptable, as shown in the analysis of
discharge submitted for the NPDES permit and the annual reports submitted to the
Division. The pond was originally designed for a larger disturbed area than that
actually disturbed, therefore, it has extra capacity to detain sediment. Also, the original
pond design assumed that the disturbed area would have a high CN (disturbed). The
site has re-vegetated well, thus further reducing the sediment that enters the pond. Due
to these factors, it is clear that the pond will meet all applicable State and Federal
water quality standards.
2) The level of water in the pond is sufficiently stable for its intended use. The
surrounding area has historically been used as rangeland for over 100 years. The
biggest problem with the area is water supply during the drier summer and fall months.
All drainages in the surrounding area are ephemeral and dry up in the summer. The
• only way ranchers can supply water to sheep or cattle are through stock ponds, which
are very important during the summer months. When summer thundershowers strike,
Engleville Gulch may only flow for 4 to 5 hours, however, the mine sediment pond
may continue to hold water for 14 to 28 days after a single runoff event. Since
thundershowers are relatively frequent in the area during the grazing months, the pond
will contain water for the vast majority of the time. Over the past few years,
experience at the site has demonstrated that this has occurred. The inspection reports
of the DMG also note that water is generally seen in the pond, especially near the inlet
of the dewatering pipe.
3) As shown on Exhibit R -Plan View of Sediment Pond, the pond slopes are adequate
for animal access, especially along the path that leads to the pond from Collection
Ditch #1 at the southwest corner of the pond. The slopes for this access are less than
SH:1 V. The access is also safe because no large rip-rap has been used along this route
that would present a hazard to the animals. The route is easily negotiable.
4) The sediment pond design and construction ensure that the pond will detain runoff
water for all events up to the 10 year - 24 hour event for a period of 24 hours. In
actuality, this event is greater because the pond was originally designed to handle a

Revised for permit renewal 11/17/95