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 DEPARTMEN~F HEALTH, Water Quality Contro~ivision {
Permit Number CO-0032751 Page 12.
CHANGES TO PERMIT AND RATIONALE FOLLOWING PUBLIC NOTICE PERIOD: (Continued)
The following changes were made in the rationale:
page 3 - The facility discharge flow values were revised. In the Facility
Description section, the production rates were revised. Almost all of the
Wastewater Treatment Facility Description was changed. Slight changes were
made to the Monitoring Summary and Operating History section.
page 5 - The water quality standards in Table 1 were revised to reflect the
change to Table Value Standards (TVS) that are now in effect for segment 3.
The paragraph following Table 1 was revised to reflect the change in WQS to
Table Value Standards (TVS) that are now in effect for segment 3. Seasonal
discharge flow limitations were added in Table 2.
page 6 - The metals limitations in Table 2 were changed to monthly limits,
based upon revised WQS for dissolved metal parameters, revised ambient
concentrations for Coon Track Creek above the Caribou Mine discharge, revised
monthly low flow values for Coon Track Creek above the Caribou Hine, and
revised seasonal discharge values for the total flows from the Cross Mine and
the Caribou Mine. Monitoring for the metal parameters was increased to a
weekly frequency. The Discussion section an flow (A.) was revised to reflect
the updates.
page 7 - The Discussion sections on the metals (B.) was revised to reflect the
updates.
pages 8 and 9 - The Whole Effluent Toxicity (WET) Testing discussion was
changed to be consistent with the existing Regulations for the State Discharge
Permit System (Reference 3).
page 10 - A discussion of the additional monitoring requirements was added for
instream measurements of flow and total hardness for Coon Track Creek to
verify the assumptions made for redetermining the limitations of this permit.
In the table under Specific Compliance Requirements, the Whole Effluent
Toxicity (WET) reporting permit citations were revised. The permit expiration
date was changed.
Appendices A, B1, and C - These appendices were updated and revised.
Appendix D - This appendix was added to show the discharge monitoring report
data from the Caribou Mine.
Discussion of Comments and Chances
Fee Category: The fee category for flows from 50,000 up to 999,999 gallons
per day indicated on page 1 has not been changed. This fee is based upon the
higher monthly average flows of 60 to 84 gpm (or 86,400 to 221,000 gpd) which
have occurred during April through August, as indicated in Appendix B1.
Stream Low Flow Value and Ambient Water Quality Concentrations for Coon Track
Creek: As indicated on page 2 of the rationale, monthly chronic and acute
stream low flow values are now applicabl~a for Coon Track Creek. These values