PERMFILE103125

• Permit No: C1982056
• IBM Index Class Name: Permit File
• Doc Date: 12/11/2001
• Section_Exhibit Name: Tipple EXHIBIT 10 NPDES PERMIT
• Media Type: D
• Archive: No

COLORADO DEPARTMENT OF PU~~IC HEALTH AND ENVIRONa1ENT, Water Q+wlin• Control Division
Rationale -Page 6, Permit No. CO-0036684
• Values for M! and Mj vary deper+ding on the background stream quality data (Mt) and tl+e applicable +sarer
quality standard (Mj). Tl+ese values are also shown in Table VI-3 a(orsg with the calculated effluent limitations
(Mz)•
Table VI-3 -- Surnrnary of Klass Balance Calculations
Parameter Stream Standard, (hf3), Effluent Concentration, (hf2),
Acute/Chronic Acute/Chronic
Iron (lR), m,q/P -/!.0 -/0.583
The TR /ton effluent limitation leas calculated using:
• design flaw of 0.473 MGD -equal to the sum of the 10-}'ear, 24-hour storm event equivalent volutrte of 0.46
MG plus the volume of spoils spring water shown on page 3 of the previous rationale (0.013 MGD),
• TR !tort stmtdard listed in section I1I.A.3. of this rationale,
• annual chronic loin flow listed in section !!l.B.2., and
• upstream concentration equal to 2.222 mg/P (mean ojdata supplied by pernitree jot station 27A).
Table VI-3 shows the effluent lirrritatiort that x~as calculated. Because this limitation is !Diver than the standard,
the standard shall apph~ in conjorntartce with regulations.
d) Anride¢radation: Since this permitting action will not result in an increase in any effluent concentration
limitation or effluent flow lirnimtion, the receiving water is not a "reviewable water", pursuant to section
3.1.8(3)(a) oJTl+e Basic Standards and Methodolo¢ies for Surface Water, based upon a finding oJno increased
water quality impact.
e) Sa[inin~ Reerdations: In compliance with dte Re¢rdarions (or Implementation of the Colorado River Salinin~
Standards Thro+t¢h the NPDES Permit Pro¢ram, total dissolved solids (IDS) ntatitoring is required. Hotvet•er,
the permittee has been granted authorization to subsitiute cond+tctit•irv for TDS. This monitoring shall accrtr on
a quarterly basis. Smnples shall be mken at the effluent discharge point. Salinity requirements are included in
Part 1.B.2. of the permit.
J) Wl+o(e Effluent To.ricity CIVET) Testir+¢: For this facilin~, chronic WET testing is required. (See Part /.A. of the
per»tit.) The previous permit required routine acute IVET monitoring jot the life of the permit and chronic IV£T
monitoring through Ma}• 30. 1994. Ho+rerer, Dnision regulations bare changed since that permit tivas written.
The current requirements are described below.
!) Purpose o(WET Testing: T)te Water Quality Caurol Division has established the use ojWET testing as a
method for identifying and controlling tonic discharges from wastewater treatment facilities. WET testing is
being utilized as a means to ensure that rJtere are no discharges of pollutants "in amounts, concentrations
or combinations which are Jtarn ful to the beneficial uses or toxic to humans, animals, plants, or aquatic
lije" as required by Section 3.1.11 (!) of the Basic Standards and Methodologies for Surface Waters.
2) Instream Waste Cor+certtrarion (IIVC): Where monitoring or limitations jot WET are deemed appropriate 6}•
the Division, chronic irtstrearn dilution as represented b}' the chronic IWC is critical in determining whether
acute or chronic conditions shall apply. For those discharges where the chronic IWC is greater than (>)
9.1 %, chronic conditions apply, where the IWC is less than or equal to (<_) 9.1 acute conditions apply.
The chronic /WC is determined using the jollowirtg equation:
IWC = [Faeilin• Flox~ (FF)/(Stream Chronic Low Flow (annual) + FF)J X 100%
The flows and corresponding IWC jot the appropriate discharge point are: