HYDRO24575

• Permit No: C1981019
• IBM Index Class Name: Hydrology
• Doc Date: 2/4/1999
• Doc Name: RATIONALE FOR PUBLIC NOTICE
• Permit Index Doc Type: NPDES
• Media Type: D
• Archive: No

COLORADO DEPARTMENT OF PUBLIC HEALTH AND ENVIRONNIEM, Water Quality Control Division
Rationale -Page 13, Permit No. CO-0045161
Prior to issuance of permit CO-0045161, srormwater discharges from the Co[owyo Mine were covered under
the General Permit for Coa[ Mining (certificatiors no. COG-850017). These discharges will be covered under a
genera! permit for stormwater discharges associated with metal mining activities-at the time that CO-0045161
becomes effective. Therefore, stormwater permitting issues for this facility will be handled separately by the
Division's Stormwater Unit, although this permit may be reopened at a later date to incorporate stormwater
provisions, if deemed appropriate.
4. Frnnpmic Reasonableness Evaluation: Section 25-8-503(8) of the revised (tune 1985) Colorado Water Quality
Control Act requires the Division to "determine whether or not any or all of the water quality standard based
effluent limitations are reasonably related to the economic, environmental, public health and energy impacts to
the public and affected persons, and are in furtherarsce of the policies set forth in sections 25-8-192 and
25-8-104. "
The Colorado Discharge Permit System Regulations, 61.0, further define this requirement under 61.11 and
state: "Where economic, environmental, public health and energy impacts to the public and affected persons
have been considered in the classifications and standards setring process, permits written to meet the standards
may be presumed to have taken into consideration economic factors unless:
a) Anew permit is issued where the discharge war not in existence at the time of the classification and
standards rulemaking, or
b) In the case of a continuing discharge, additional information or factors have emerged that were not
anticipated or considered at the time of the classification and standards ru[emaking. "
Furthermore, this is not a new discharger and no new information has been presented regarding the
classifications and standards. Therefore, the water quafiry standard-based effluent limitations of this permit are
determined to be reasonably related to the economic, environmental, public health and energy impacts to the
public and affected persons and are in furtherance of the policies set forth in Sections 25-8-102 and 104. !f the
permittee disagrees with this finding, pursuant to 61. II (b) the permittee should submit all pertinent information
to the Division during the public notice period
B. Monitoring
Effluent Monitoring.• Effluent martitoring will be required as shown in Tables VI-4 and VI-S. Monitoring for
outfalLs 001 a -OIOa shat! occur at the otufalls from final ponds prior to entering the immediate receiving waters.
Initial monitoring for outfalis 0026, 0046, 0076, 0086, 0096 and OIOb shall occur within the pit (for outfall
0026, within the Washbay Pond) at a location representative of where pumping would originate (far outfall
0026, just prior to the discharge point from the Washbay Pond to the Work Area Pond). If limitations are met
with this initial sampfe and pumping occurs, monitoring would then occur at the outfa[[ of the pump from the pit
(for autfal[ 0026, from the Washbay Pond outfal[) to the associated sedimentation pond in conformance with the
monitoring frequencies specified in Part I.B. 1. of the permit.
Table VI-4 -Monitoring Requirements for OutfalLr OOla, 002x, 003a, 004a, OOSa, 006a,
007a, 008a, 009a, OIOa
Pa~wrteter tSleasurement Frequency . Stimple.Type
Flaw, MGD Weekly Instantaneous
or Continuous
Total Suspended Solids, mg/P Monthly Grab
Total Iron, mg/P Monthly Grab
Settleable Solids, m1/F Monthly Grab
Oi[ and Grease, mg/P Weekly Visual a/
pH, s. u. LVeekly In-situ