HYDRO25740

• Permit No: C1981010
• IBM Index Class Name: Hydrology
• Doc Date: 2/7/1994
• Doc Name: RATIONALE FOR PUBLIC NOTICE
• Permit Index Doc Type: NPDES
• Media Type: D
• Archive: No

COLORADO DEPARTMENT OF HEALTH, Wnrer Quality Control Division
Rnrimtale, Amendment No. 2 -Page 2 Permit No. CO-0032115
ll/. RECEIVING STREAA9:
Ou jnl( 0/5 is a new discharge added vin this amendment. li discharges to Flume Gulch, ar shown in amended Figure 4
of the permit. The gulch is tributary to the Yampa River and is within segment 3n ojthe Lower Yampa River. This
segment i.c clrusified: Use Protected; Aquatic Lije, Class 2 (warm); Reneation, Class 2,, Agriculture. Refer to previous
pernrir renewal rationale for additional information regarding the receiving waters.
Arrrirleerndntion: Because this segment is use protected, an antidegradation review is not required pursuant to 3./.8(3)
oj7he Bncic Standards and Methodologies for Surface Water.
IV. PURPOSE OFAMENDA9ENT.•
In letters dared August 17, 1993 and August 24, 1993, the permirree t nested the addition of one new outfnll, 015, for
the discharge of surface runoff and possible mine water; deletion ojn e water ar a source to outjalLr 003 and 006; and
ruldirion of mine water as a source to outfnll 013. The affected outja~ are noted ar such in the table above. The
permitree aLro requested that the legal and facility contacts 6e revised The contacts shown ors this amendment are those
specified in their request.
CHANGES TO EFFLUENT LIMITATIONS AND MONITORING I
6ecmece of there changes, the limitnrinrrs for ourjn[Lr 003, A76 and Ol hove changed, and limitations here been added
for ourjnll 015, as shown in Part I.A. ojthe pernrir. OurfalLs 003 nor 6 will no longer be authorized to discharge
urine Wnrer, outfnll 013 will now he nwhorized to discharge mine x»r and ourjnll 015 as added will be authorized to
rliachnrge surface runoff and mine Wnrer. Addiriorm!!y, for the purpn. ojsimplijying the permit, pons LA. nod 1. B. will
be revised to show the [inrirmiatc mrd monitoring requirerrrerus far en owfn!! in n different forntnr.
Vl. IVHOLE EFFLUENT TOXICITY (WET)
Al.co, nr rhic rime, the permit will be revised from the previous WET r buirements to the current WET requirements. The
Diris~ion i.c currently reopening all permits with older WET requireme, Its for this update. These requiremerus are
exp(nirred below.
Fur this facility, acute WET rerring i.c required. (See Parts LA and 1. f of the penult.)
I) Purpose of WET Teuine: 77te Wnrer Quality Conrral Division lrn.~ srnblished the use njWET testing ns a method jar
irlenrifving mrd enrrn~olfiug tonic disclmrgec from +vave+raer n~eni tear jncilitiec. WET resting i.c heing urilizr'd n.c n
ruenn.t ro ensure thin there are no di.cclrm~ges of pollmnnrs "in nn ants, concenn~ntious or conrbirrntioes mhiclr are
hmn ful to the heneytcinl u.cec or ro.ric ro humm~.c, mtinmLr, plane ar aqumic life" n.c required by Secrinu 1. 1. 1 l (I)
rf the Basic Stnndnrdc per! Medmrlnlopiea far Sur(nce Wnrerc.
2) ln.cn~enrn Wn.cte Concenrrnrimt (1WC1: Where monitoring or limo ions for WET are deemed appropriate by the
Di ri.rinn, chronic iavtream dilution ac reprecenred by the chroeir C i.r critical in determining whed~er acute nr'
clmwric conditions shall apply. For those discharges inhere the c Quit IWC is greater thou (>) 9. / 95, chrarric
cnnr/itions apply, where the /WC is less than or equal ro (<) 9.! cure condiriorrs apply. The chrarric IWC i.c
rlctermined using the jollo+ring equation:
IWC = (Facility Flmv (FFJ/(Stream Chronic Low Flow (nom 1) + FFj/ X 100%
71te flows and corresponding IWCfor the approprime rlisrhnrge r im are:
Discharge Points Chronic Low Flow, Facility Desig.Flow, IWC, (%)
30E3, (cfs) (cjs)
002, 005, 009, 0 ,mries 100
OI 1, 013, 015