HYDRO24194

• Permit No: M1980244
• IBM Index Class Name: Hydrology
• Doc Name: AMENDMENT 1 RATIONALE CRIPPLE CREEK & VICTOR GOLD MINING CO A JOINT VENTURE BETWEEN PIKES PEAK MININ
• Media Type: D
• Archive: No

COLORADO DEPARTMENT HEALTH, Water Quality Control+Divis•
Rationale - Page 12. Permit No. CO-0024562.
5. Whole Effluent Toxicity (WET) Testing:(continued):
a) Purpose of WET Testing: Section 6.9.7 of the Regulations for
the State Discharge Permit System (6.1.0), 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.ll (1)(d) of the Basic
Standards and Methodologies.
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 (IWC): 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 statitically significant
difference in the mortality (at the 95X confidence level)
observed, for Ceriodaphnia sp. (water flea) and fathead minnows,
between the control and any effluent concentration less than or
equal to the Instream Wast Concentration (IWC) or 2) a species
mortality in any dilution of effluent (including 100% effluent)
exceed 50%. The IWC is determined using the following equation:
IWC = [Facility Flow (FF)/(Stream Low Flow (annual) + FF)] R 100%
Using the facility design flow of 2.58 MGD and the stream low
flow of 4.39 MGD, the IWC for the permittee is therefore 37.0%,
which represents a wastewater concentration of 37.0% effluent to
63.OY, dilution water.
In the event that exploration or active mining takes place in
the Carlton Tunnel, the facility design flow is expected to
increase to 3.76 MGD. The IWC for the permittee under these
circumstances is therefore 46.1%, which represents a wastewater
concentration of 46.1% effluent to 53.9% dilution water.