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 DEPARTMENI~F HEALTH, Water Quality Control Division
Permit Number CO-0032751 Page 4 .
MONITORING SUMMARY AND OPERATING HISTORY: (Continued)
the levels for the 30 day average limit :is well as the daily maximum
limitations for total recoverable cadmiutu, total recoverable copper, total.
recoverable lead, and total recoverable ::inc. Division inspections of the
facility were made on Hay 23, 1988 and August 28, 1990. Both inspections
indicated that the facility has had. significant violations.
Previously, one Notice of Violation. and (:ease and Decist Order (NOVCDO) was
issued to the permittee on March 7, 1986 addressing previous concentrations of
cadmium during 1985 which exceeded the daily maximum total recoverable cadmium
limitation, as we 11 as the previous implf:mentation plan compliance schedule
for achieving the final limitations for f:otal recoverable zinc. Later, a
Stipulated Agreement was signed by the Division and the permittee, with
payment of the portion of a civil penalt;i which was not suspended. In regard
to the compliance schedule referred to itt the NOVCDO, as part of the
Stipulated Agreement, the permittee agreed to bring the discharge into
compliance with the final effluent limitations for zinc and cadmium by June 1,
1987. Later, as indicated in the previous rationale for Amendment No. 2 for
this permit, improvements at the facility were constructed during the summmer
and fall of 1987 arcd operational by the end of December 1987, including an
explanation of the No. 1 settling pond, completion of the No. 2 settling pond,
installation of rubber linings for the ponds, and installation of the new
filtration building.
A comparison of effluent concentrations during the period before the new
treatment system improvements (during 1987) and after the improvements (1988)
in Appendix B1 indicates no significant improvement in the cadmium, copper,
lead, or zinc effluent concentrations. Thus, exceedances for these four
parameter limitations have continued to occur since the new treatment system
improvements. The only month where there has been compliance with all permit
limitations during discharge was during August 1988. The permittee is
expected to attain compliance with the limitations of this permit.
APPLICABLE RULES AND REGULATIONS
A. Federal: Federal technology based effluent guideline limitations (BPT
and BAT: 40 CFR, Part 440.102 and 103) are applicable to this facility
because mining has previously taken place and is projected co occur again.
B. State: State Effluent Standards (SES) (10.1.0) apply co all discharges
in the state for parameters not superceded by Federal Effluent Guidelines
or Stream Standards. The SES apply t:o more conventional pollutants.
In addition, to these standards, the State must also apply the receiving
stream Water Quality Standards (WQS) which are appropriate for this
facility.
The WQS are applied based on a mass balance for each pollutant in
question. The variables used in the calculation are the allowable
in-scream level (WQS), the chronic stream low flow (30E3) or the acute
stream low flow (lE3), the effluent flow (Qeff)~ and the background
concentration (Camb)~ as shown in Appendix C. The effluent flow is for
both the Cross Mine and Caribou Mine discharge flows; these flows and the
mass balance equation are both included in Appendix C.