PERMFILE107381

• Permit No: C1994082A
• IBM Index Class Name: Permit File
• Doc Date: 12/11/2001
• Doc Name: NPDES PERMIT YOAST MINE
• Section_Exhibit Name: TAB 15 APPENDIX 15-1
• Media Type: D
• Archive: Yes

COLORADO DEPARTMENT OF PUBLIC HEALTH AND EANlRONMEM, Water Qualiq• Control Division
Rationale -Page 9, Permit No. CO-0000221
Table VI-4 - Effluent Limitations jor Outjall 008
i Ducharge limitations
Maximum Concentrations
Parameter 30-Day Avg. Daily Max. Rationale
Flaw, MGD Report Repon Design Capacity
TSS, mg/f* 35 70 Federal EJfluem Guidelines
Total Recoverable Iron, mg/f 1.0 Report Water Quality Standards
Settleable Solids, mf/F* Report 0.5 Federal Effluent Guidelines
Oil and Grease, mg/f Report !0 State Effluem Regulations
pH, s.u. (minimum-maximum) N/A 6.5-9.0 Water Quality Standards
WET, Chronic Lethalip• N/A No Statistical State Effluent Regulations
Difference
Table VI-5 - Effluent Limitations jor Outjall 009
Discharge Limitations
Afarimum Concentrations
Parameter 30-Day Avg. Daily Max. Rationale
Flow, MGD Report Report Design Capacity
• TSS, mg/P* 35 70 Federal Effluent Guidelines
Total Iron, mg/f * 3.0 6.0 Federal Effluent Guidelines
Settleable Solids, mF/P* Report 0.5 Federal Effluent Guidelines
Oil and Grease. mg/f Report 10 Stare Effluent Regulations
pH, s. u. (mirsimum-maximum) A'/A 6.5-9.0 Water Quality Standards
Total Suspended Solids and Total Iron limitations are Priman~ Limitations, and Settleable Solids limitations are
Alternate Limitations. Exemption from these limitations due to storm events is subject to burden of proof
requirements -see section l'I.A.3.b).
2. Total Maximum Daily Load ~IMDL i .4nalvsis (lt'arer Oualin Based Effluent Limitatiansl: Water qualin• standard
(WQS) based total recoverable iron lirniratioru apply ro outfa/ls 004 and 008. In order to calculate WQS based
Limitations, a Total Alarirnurn. Daily Load (TA1DL) analysis +,as performed. !n most situations, a mass balance
equation is used ro determine the effluent cancenrrations that x~ould not violate the allowable instream
concentrations defined by the water quabn• smndards (except in the case of pH, where the limitations are set direcrlc
from stream standards or effluent regularioru +vithout using a mass balance approach). The mass balance equation
is:
~ ly- = MaQ, - A4,Q.
Q:
Where:
Q, = Upstream !ow flow (1 E3 or 30E3) from Table II!-2.
Qr = 30day average combined effluent flow for k004 and 008 (liighesr month from Table VI-8)
•
Q, = Combined dox•nsrream flow (Q, + Qr)
M, = Upstream background pollutant concerstration from section !I/.B.1.
MI = Utdmown; Maximum allowable effluent pollutant concentration calculated using mass balance equation
M3 = Maximum downstream allowable pollutant concemration (stream standard)