PERMFILE61538

• Permit No: C1980005A
• IBM Index Class Name: Permit File
• Doc Date: 12/11/2001
• Doc Name: NPDES PERMIT
• Section_Exhibit Name: TAB 7 APPENDIX 7-5
• Media Type: D
• Archive: Yes

COLORADO DEPARTMENT OF HEALTH, Water Quality Control Division
Rationale - Page 10. Permit No. CO-0000221.
~VI
TERMS AND CONDITIONS OF PERMIT
Following submittal of the initial six sets of monthly data, the
Division shall determine whether the permittee is required to submit a
report addressing the feasibility of salt removal, in accordance with
the salinity regulation. If the TDS report is required, the Division
shall so advise the permittee by letter and the report shall be
submitted within 180 days.
Ponds which treat mine water and/or spoil springs may discharge on a
routine basis and have a higher potential for contamination. Therefore,
for discharge point 005 (which will contain mine water), a TDS report on
the feasibility of salt removal shall be required before any discharge
is allowed tp take place from 005. If salt removal is found to be
viable, the permit may be amended to include appropriate additional
requirements. TDS monitoring shall be required on a quarterly basis.
5. Whole Effluent Toxicity (WET1 Testing
For this facility, acute WET testing is required at 002, 003, 004, 005, 006
and 008. Chronic WET testing is required at 004 and 008. (See Parts I.A
and I.B of the permit.)
•
a) Purpose of WET Testino: Section 6.9.7 of the "Regulations for the State
Discharge Permit System",.passed by the Water Quality Control Commission
(WQCC), has established the use of WET testing as a method for
identifying and controlling toxic discharges from wastewater treatment
facilities. WET testing is being utilized as a means to ensure that
there are no discharges "in amounts, concentrations.or combinations
which are harmful to the beneficial uses or toxic to humans, animals,
plants, or aquatic life" as required by Section 3.1.11 (1)(d) of the
"Basic Standards and Methodologies for Surface Waters'•.
Chemical analysis of effluent has provided only a partial evaluation of
the potential impact a discharge could have on the receiving stream.
Also, chemical analysis cannot evaluate the synergistic or antagonistic
effect of compounds. There are also compounds for which an accurate or
reproducible method of chemical analysis has not yet been developed, as
well as compounds which are just beginning to be evaluated for toxic
effects. WET testing will provide a more comprehensive means of
evaluating the toxicity of a discharge than could otherwise currently be
accomplished.
•
b) Instream Waste Concentration (IWC1: As a condition of the permit, the
permittee will be required to conduct routine monitoring for acute
toxicity. An unacceptable level of acute toxicity occurs when 1) there
is a statistically significant difference in the mortality (at the 958
confidence level) observed, for Ceriodaohnia sp. (water flea) and
fathead minnows, between the control and any effluent concentration less
than or equal to the Instream Waste Concentration (IWC) or 2) a species
mortality in any dilution of effluent (including 1008 effluent) exceeds
508. The IWC is determined using the following equation:
IWC = [Facility Flow (FF)/(Stream Low Flow (annual) + FF)] X 1001