HYDRO31631

• Permit No: C1981044
• IBM Index Class Name: Hydrology
• Doc Date: 1/7/1994
• Doc Name: RATIONAL FOR PUBLIC NOTICE
• Permit Index Doc Type: SEDIMENT POND INSPECTIONS
• Media Type: D
• Archive: No

COLORADO DEPARTMEiirT OF HEALTH, Water Quality Control Division
Rationale -Page 18, Permit iVo. CO-0034142
f. Whole EfRuent Toxicity /NET7 Terrine
For this facility, quarterly acute WET testing is required at OutfolLr 003, 022, and 024 (See Parts /.A and
LB of the pernit.)
(1) Purpose of WET Testine: The Watts Quality Control Division has established the use of W61'testing
as a n:etiSod for idenrifying and controlling tonic discharger from wastewater treatment facilities. WET
testing is being utilized as a means to ensure that there are no discharges of pollutants "in amounts,
concerttriuions or combinations which are harmful to the beneficial usu or tonic to humans, animals,
plants, or aquatic life" as required by Section 3.1.11 (I)(dJ of the 'Basic Standards and
Methodo,vgies for Surface Waters ".
(2J Instream Waste Concentration /IWCI: Where monitoring or limitations far WF.I' are deemed
appropriate by the Division, instream dilution as represented by the /WC is critical to determining if
acute or chronic rnnditions apply. For those discharges where the 1WC > 9.1 %, chronic conditions
apply. The IWC is detmnintd using the following equation:
IWC = (Facility Flow (FF)/(Stream Law Flow (annual) + FFJJ X 100°,6
7he1?ows and corresponding IWCjor the appropriate discharge point are.•
,.
Dischgrge Point ;..::: Clirnnic Lqw FTow, .30E3;::....Facility.Design;Flaw; ,(cjs) :' I.WC,. (%) . ;;. .
(efs)......
Outfal1003 42
Outfa11022 42
OutfaI1024 42
4.46 9. ti
0.9D 2. /
0.92 2. /
The /WC for this permit is listed above. Therefore chronic conditions are applicable to this permit for autfall 003, but, are
not applicable jot 022 or 024.
(3) Acute Biomonitorine: Outjalis 022, 024, because of the presence of rrtetair, the Division believes there
is reasonable potential for the discharge to interfere with attainment of applicable water quality
class cations or standards. Because ojthis condition, the acute toxicity limit has been incorporated
into the hermit and becomes effective January 1, 1997. Prior to the acute WET limit becoming
effective, the permiaee is required to conduct routine monitoring, the results of which are to be
reported as LCSO. /jthe LCSO 5 100% e~iuent, the per»unee is required to conduct the nuromatic
compliance schedule as identified in Parr 1. B. of the permit.
(4) Chronic Biornonitorine: Outfall 003 -Because ojthe presence ojmetais in the discharge, the Division
believes there is reasonable potential jot the discharge to interfere with attainment of applicable water
quality class cations or standards. Because of this condition, the chronic limit has been incorporated
into the hermit and becomes effective January 1, 1997. Prior to the chronic limit becoming effective,
the perm:'aee is required to conduct routine monitoring. The results ojthe testing are to be reported
on Division approved forms. The perminee will be required to conduct two types of statistical
derivatio:cs on the data, one looking jot any statistically sign cant difference in toxicity between the
control and the ejJluent concentrations and the second idenr Eying the IC2S, should one exist. Both
sets of calculations will look at the full range of tonicity (lethality, growth and reproduction). !ja
level of chronic [oziciry occurs, such that there is a statistically sign cant difference in the lethality
(at the 9.5% confidence level) between the control and any effluent concentration less than or equal to
the /nstream Waste Concentration (1WC) and if the lethality IC25 G the /WC, the permittee will lie