HYDRO27818

• Permit No: C1982056
• IBM Index Class Name: Hydrology
• Doc Date: 10/10/2006
• Doc Name: July and August 2006 DMRs ‎(CO-G072272)‎
• From: Twentymile Coal Company
• To: DRMS
• Permit Index Doc Type: DMR’s
• Media Type: D
• Archive: No

~.. - - -
~ Twentymile Coal
°/i
2006
i Ivlr. Christopher Gates
/ ~ Environmental Protection Specialist
Colorado Department of Public Health and Environment
~ Water Quality Control Division -Permits and Enforcement
i
4300 Cherry Creek Drive South - WQCD-P-B2
Denver, Colorado 80222-1530
[phone]
29515 Routt County Road #27
Oak Creek, CO 80467
970.879.3800
Re: Twentymile Coal Company - Foidel Creek Mine, Application for Construction
Dewatering Wastewater Discharge
Dear Mr. Gates:
Twentymile Coal Company (TCC) is developing a new mine ventilation shaft. The 28-
foot diameter by approximately 1,300-foot deep shaft is being developed using
continuous excavation methods. In planning for and permitting the shaft development
project with the Colorado Division of Minerals and Geology (CDMG), TCC anticipated
some groundwater inflows during shaft excavation and designed anon-discharging
sedimentation pond to temporarily contain both disturbed-area runoff from the shaft pad,
and the minor quantities of groundwater anticipated during shaft excavation. In
conjunction with the shaft excavation activities, TCC has also developed several large
diameter (8-inch) boreholes, from the surface into the mine workings, to be used as
connections for mine utilities (power, clean-water, rock dust, etc.).
In designing the containment pond, TCC anticipated that any reasonable volume of
excess groundwater inflows could be pumped from the containment pond into one of the
drop boreholes, with a connection to the underground mine water system. Initially this
' system worked well, with periodic pumping maintaining stable water levels in the pond.
As shaft excavation has proceeded, however, a zone has been encountered where
relatively high (50 gpm) groundwater inflows have exceeded the design capacity of the
existing water handling system. Pond levels have been maintained, both by increasing
the pumping rate to the drop borehole and by pumping excess water to trucks, which haul
the water to an existing permitted discharge point.
Given that relatively high groundwater inflows have continued, TCC, with this submittal,
is requesting approval of a temporary Construction Dewatering Wastewater Discharge
Permit that will allow discharge from the existing containment pond to an unnamed
ephemeral tributary to Fish Creek. The attached application form provides laboratory
analysis results for the current raw discharge stream from the shaft excavation. The shaft