HYDRO30633

• Permit No: M1977410
• IBM Index Class Name: Hydrology
• Doc Date: 7/9/1991
• Doc Name: RATIONALE FOR PUBLIC NOTICE
• Media Type: D
• Archive: No

COLORADO DEPARTMENT O~EALTH, Water Quality Control ~ision
Permit Number CO-0032751 Page 13.
CHANGES TO PERMIT AND RATIONALE FOLLOWING PUBLIC NOTICE PERIOD: (Continued)
Discussion of Comments and Changes:
Stream Low Flow Value and Ambient Water Quality Concentrations for Coon Track
Creek (cont.): are based upon the low flow value for Coon Track Creek above
the Caribou Mine. See page 2 of the rationale for the individual flow values
for each month. The ambient water quality values for Coon Track Creek are
derived from an assumed zero ambient based concentration for Coon Track Creek
above the Caribou Mine. A summary of the flow and water quality data from the
Caribou Mine discharge is included in Appendix D of this permit (Cross Mine)
file.
Facility Discharge Flow Values: Seasonal discharge flow values (0.036, 0.122
and 0.093 MGD) were determined for the Cross Mine discharge paint 001, as
indicated on page 2 of the rationale. This is based upon the discharge
monitoring report data in Appendix B1.
Monitoring Summary and Operating History: The first sentence in t;he last
paragraph of this discussion section at the end of page 4 of the rationale is
retained because the Division still concludes that no significant improvement
has occurred in the discharge water quality. Permit limitations are still not
in compliance, and this problem will need to be addressed and remedied as soon
as possible.
Discharge Point 001 Location: The permittee requested that the outfall
location be redefined as following the peat bog, prior to entering Coon Track
Creek. However, the location description of the outfall at Cross 14ine has not
been changed. The peat bog following the filter house is not considered part
of the treatment system; this natural existing bog is considered b:~ the
Division as waters of the State. Since there are no contributing :Flows in the
peat bog, the bog cannot be considered for a mixing zone.
Mercury: The permittee requested that the limitation and monitoring for
Mercury be deleted, based upon previous discharge monitoring report data that
was at or below the minimum level of detection (0.0001 mg/1). The Division
has not deleted the Mercury limitations and monitoring because levels above
the previous and proposed Mercury limitations have been reported for 4 months
during 1989 and 1990. These levels ranged from less than 0.0002 m~;/1 up to
0.0009 mg/1. Thus, this parameter still needs to be addressed in ~.he permit.
One additional change for this parameter is that the limitations artd
monitoring have been changed to Potentially Dissolved Mercury.
Whole Effluent Toxicity (WET) Testing Requirements: As requested try the
permittee, the Whole Effluent Toxicity (WET) Testing requirements were changed
in the rationale and the permit to be consistent with the existing Regulations
for the State Discharge Permit System (Reference 3).
Flow Measuring Device: Flow measurement at discharge point 001 ha:: been taken
with a five gallon pail and stop watch. This method is acceptable to the
Division, provided that values within lOX of the actual flow are mfeasured.
However, the permittee has also indicated that a 4 inch McKormich peter (with