HYDRO27467

• Permit No: C1981019
• IBM Index Class Name: Hydrology
• Doc Date: 11/1/2006
• Doc Name: Request for Relief from CDPS Water Qualilty Allowance Exceedence of TSS at Outfall 003A
• From: Colowyo Coal Company L.P.
• To: WQCD
• Permit Index Doc Type: NPDES
• Media Type: D
• Archive: No

nnntanons, rt rs necessary to prove that arscnarge occurrea 2vunm 4d Hours after precrpuanon greater than
the 10-year, 2~-hour event has stopped.
Relief from primary TSS limitations at OutfaI1003A: Please see 003A Exceedence Report attached to
this submittal for more detail and back-up information.
Rainfall was recorded at Colowyo on August 8, 2006, one and one half days before sampling was completed
at this location. Inflow into this pond is primarily in the form of stormwater runoff at this time. Colowyo
believes this specific incident of exceeding primary TSS limitations is due primarily to increased stormwater
runoff caused by a succession of storms over the course of the five days previous to the sampling date.
Colowyo performs PE reviewed pond inspections of all NPDES ponds on a quarterly basis as mandated by
CDMG/Colowyo Permit requirements. These quarterly inspections are reviewed by CDMG staff and
specific guidance, maintenance issues, and improvements are discussed as necessary with Coloywo's
assigned CDMG inspector (currently James Stark).
Outfall 003A was cleaned out in November 2005, and all sediment accumulation was removed at that time.
The available sediment volume storage capacity for the pond during the second quarter was approximately
89.1% of the As-built design storage, well below any tilt level for permit compliance. Ponds are tazgeted for
cleanout in the event one of two criteria are met; either the pond approaches 60% available storage capacity,
or the rate of sedimentation suggests the pond will receive enough sediment to reach 60% available capacity
during the course of the following year. As 003A pond has fulfilled the rate of sedimentation criteria for the
last several years, cleanout was identified as necessary and was scheduled for the fall of 2006
(October/November). As planned, sediment removal from this pond was completed during October 2006.
In an effort to further minimize issues with TSS limitations, Colowyo is in communication with GE Betz in
order to identify any acceptable products on the market that could be more effective at settling out
suspended materials. Testing is in progress to evaluate the relative effectiveness of these products.
Colowyo is currently evaluating opportunities for improving the manner in which stormwater enters the
pond. Modifications to in-pit drainage structures and conveyance ditches may be warranted if opportunities
for minimizing particle/sediment loading are discovered. This is an on-going process and improvements
will be implemented as they are identified.
Because Colowyo's ponds aze flow-through treatment ponds and not containment ponds, it is not possible to
impound waters for an extended period of time once discharge levels have been reached. These ponds were
designed to treat stormwater inflow for settleable solids to a level of 0.0 ml/I during a 10-year 24-hour storm
event.
It is Colowyo's belief that due diligence, good faith efforts and in-house procedures and practices were
followed prior to, during, and after the exceedence of TSS limitations reported from August 10, 2006
sampling and humbly request the grant of a waiver from said limitations as allowed by our CDPS Permit at
your discretion.
Thank you for your consideration. Please feel free to contact me if you have any questions or concerns. I
can be reached at [phone].
Sincerely,
To~enn o~
Environmental Engineer
Encls.
Copy: Jim Sark (CDMG)
NPDES Reports Binder w/encl
C.A. 22.7.2 w/enci
Colowyo Mine • 5731 State Highway 13 • Meeker, Colorado 51641
7 +l 970 824 1500 • F +l 970 824 1504 • www.rtea.com