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 DEPART:fENT OF HEALTH, Water Quality Control Division
Rationale - Page 11. Permit No. CO-0000221.
VI. TERMS AND CONDITIONS OF PERMIT
The flows and corresponding IwC for the appropriate discharge points
are:
Discharge Point Stream Low Flow (lE3) Facility Flow IWC
(10-yr 24-hr event)
002 0 MGD 3.89 MGD 1008
003 0 MGD 0.13 MGD 1006
004 0.45 MGD 2.18 MGD 836
005 0 MGD 1.51 MGD 1006
006 0 MGD 3.61 MGD 1006
008 0.45 MGD 1.87 MGD 816
As an example, the IWC for this permit for 002 is 1006, which represents
a wastewater concentration of 1006 effluent to 06 receiving stream.
c) Acute WET Testing: For discharge points 002, 003, 004, 006 and 008, at
this time the Division believes that there is no reasonable potential
for the discharge to interfere with attainment of applicable water
quality classifications or standards. The basis for this belief is that
these are discharges from existing sources, and the existing monitoring
data do not indicate any suspected toxicity problems. Therefore,
monitoring only is being required in the permit.
For discharge point 005, since it is a new source, and based upon the•
nature of mine mater, an acute tonicity limit would normally be
incorporated into the permit. However, the permittee has presented
irifcrmation indicating that the maximum expected pit inflow rate for
mine water is only 1 gpm. Since the volume of stormwater expected is
substantially higher, monitoring only is being required in the permit at
this time.
For any of the discharge points, if an unacceptable level of acute
toxicity is identified, the permittee is required to conduct a toxicity
incident response and identify a control program to eliminate that
toxicity, as identified in Part I.B. of the permit. Additionally, the
permit may be modified to incorporate an acute toxicity limit, as
provided in regulation.
d) Waiver of Requirements: Industrial facilities having simple effluents
of consistent quality, which can be totally characterized chemically,
may request a full or partial waiver of acute WET testing for the
remainder of the life of the permit, subject to Division approval, if
the first four quarters of testing show no pattern of toxicity.
e) Chronic WET Testing: The determination as to whether or not an
individual facility must conduct chronic WET testing is dependent upon
two factors: the ratio of the chronic stream Low flow (30E3) to the
design flow of the wastewater treatment plant and the aquatic life
classification of the receiving water. If the receiving water ie
classified aquatic life class 1, chronic WET testing ie always required