2009-09-29_PERMIT FILE - C1994082

• Permit No: C1994082
• IBM Index Class Name: Permit File
• Doc Date: 9/29/2009
• Doc Name: Drainage and Sediment Control Plan
• Section_Exhibit Name: Tab 13 Attachment 13-12
• Media Type: D
• Archive: No

February 1999 Yoast Mine * 13-12 Drainage and Sediment Control Plan ? 14
7.0 SMALL AREA EXEMPTION DESIGN
• A request to treat runoff from the planned topsoil piles under the small area exemption (SAE) regulations
(Section 4.05.2(3)) was approved by the CDRMS in 1999. Runoff from the stockpiles will be controlled by
constructing a small containment berm immediately down-gradient of the piles. The topsoil pile SAE
request is presented in Appendix 13-12.4, Small Area Exemption Design, of this Drainage and Sediment
Control Plan.
A small area exemption has been delineated for the ridge top to the north/northeast of the existing Pond
012. The SAE is an interim drainage control plan to be utilized until a final remediation plan is approved
and implemented. This interim plan will be implemented by regrading a portion of the rid e to to direct
drainage away from the south side of the ridge. The steps to imp ement 's mterim drainage control plan
• removing and leveling the existing dozer dips;
• eliminating the existing water bars that currently direct water toward the south side of the ridge;
• eliminating remnants of Postmine Channel YPM-23; and,
• installation of wattles or other similar products to slow runoff, allow sediment to drop out of the
runoff, and to direct the flow toward the north. The wattles or other products will be installed
along the ridge at approximate 150 foot intervals or be field fit as required.
Refer to Figure 13-12.4-1 for a graphic view of the conceptual plan.
8.0 STOCK POND DESIGN
• The construction of stock ponds is proposed in conjunction with the construction of various postmine
channels. Locations are shown on Exhibit 13-12.1A, Permanent Channel and Pond Watersheds. Since the stock
ponds are relatively small in size and there are no residential or commercial structures or mining operations
immediately below any of the stock ponds, they do not create a threat to public health and safety or threaten
significant environmental health.
SCC has constructed numerous stock ponds (temporary and permanent) in the Seneca II and II-W
reclaimed areas, which continue to function as designed and according to the applicable requirements of
Rule 4.05.9. Designs for the proposed stock ponds ST-1 and ST-2 are presented in Appendix 13-12.5,
Stockpond Emergency Spillway Design SEDCAD Results. A certified as-built of each stock pond will be
submitted following construction.
All stock ponds are located in reclaimed areas and are not primary sediment control structures. They are
relatively small with a storage capacity of not more than two (2) acre-feet and an embankment height no
greater than five (5) feet measured from the invert of the spillway to the upstream toe of the embankment.
The combined slope of all the embankments will be less than 5H: 1V with no slopes greater than 2H: 1V.
All stock ponds will contain a single open channel spillway designed to safely pass a 25-yr/24-hr
precipitation event. The spillway will be configured to have a minimum of one (1) foot of freeboard.
Riprap requirements were determined using the PADER Method and adding three (3) inches to account for
conservatism. Emergency spillway configurations and riprap size for each stock pond location is presented
in the Table 13-12.8, Stock Pond Spillway Summary.
LJ
Montgomery Watson Mining Group * 165 S. Union Boulevard Suite 460 * Lakewood Colorado 80228 * [phone]
TR-44 Revised 08/09