HYDRO29057

• Permit No: M1988112
• IBM Index Class Name: Hydrology
• Doc Name: TABLE OF CONTENTS
• Media Type: D
• Archive: No

COLORADO DEPARTMENT OF HEALTH, Water Quality Control Division
Rationale -Page 18 Penni[ No. CO-0045675
~ Whole Effluent Toxicity (WET) Testing (Cont.)
The IWC for attfa[l 001c at the facility discharge flow rate of !10 gpm is 12.0 %, which represents a
wastewater concentration of 12% effluent to 88% receiving stream. Thus, chronic WET testing is applicable
for outfalls OOIa, 0016, and 001 c.
3) Chromic WET Monitoring: Since the facility's x~astewater source data and treated discharge data have very
low concentrations ojpollutants, and one WET testing (April 2000) has been perfanned for both species
which resulted in passing tests jar lethality arrd growth, the Division has determined of this time that there is
no reasonable potential for toxicity to occur in this discharge, thus no chronic lethality limitation has been
established for this permit. /n accordance with Section 6/.8 (2)(b)(i) ojthe Colorado Discharge Permit
System Regulations, the pennittee xil[ be required to conduct routine monitoring for chronic toziciry using
Ceriodaphnia sp. and fathead minnows. The results ojUre testing are to be repored on Division approved
forms. The penmittee will be required to conduct two types ojstatistical derivations on the data, one looking
for any statistically significan[ difference in toriciry betx~een the control and dre effluent concentrations and
the second identifying the /Czi, should one exist. Both sets ojcalrulations will look at the full range of
roriciry (letltaliry, growth and reproduction). !ja level of chronic toriciry occurs, such that there is a
statisticaly significant difference in the lethality (at the 95% confidence leveQ beM~een the control and any
effluent concentration less than or equal to the /nstrean Waste Concentration (/WC) and if the 1Cu < the
/WC, the pennittee will be required to follow the automatic compliance schedule identified in Pan /.A.4. (c) of
the permit, ijthe observed toriciry is due to organism lethality. /f the toriciry is due to diJJ'erences in the
grox~tlr of the fathead minnows or the reproduction of the Ceriodapltnia, no immediate action on the par of
the pennittee will be required. However, t/tis incident, along with other WET data, will be evaluated by the
Division and may form the basis for reopening the permit and including additional WET limits or other
requirements.
4) General /njonnation: The pennittee should read the WET resting sections of Part /.A. and /. B. of the permit
carefully. The permit outlines the test requirements and the required follow-mp actions the permi[tee must
take to resob~e a toxicity incident. The pennittee should read, along with the documents listed in Pan f.A.4 of
the permit, the Colorado Water OualiN Contra[ Division Biornonitoring Guidance Document, dated July /,
1993. This document outlines the criteria used by the Division in such areas as granting relief from WET
testing, modifying test methods and changing test species. The pennittee should be aware that sortie of the
conditions oudined above may be subject ro change if the facility experiences a change in discharge, as
outlined in Part I/.A.1 ojthe permit. Such changes shall 6e reported to the Division immediately.
S. Stonnwater Evaluation: Stormwater discharge pernrits are required for active and inactive rneml mining facilities as
covered under Standard Industrial Classification: (SIC) Code I0. This S/C Code includes raining, developing mines, or
exploring for metallic minerals (ores).
Division records indicate that Battle Mountain Resources, /tic. applied for and obtained coverage under a general
permit for Stonnwater discharges associated x~th metal mining for the San Luis Project. The CDPS certification
number is COR-040050. Stonnwater pennritting issues for this facility rill be handled separately by the Division's
Stonnwater Unit, although this permit may be reopened at a later date to incorporate stonrrwater provisions, if
deemed appropriate.
6. Economic Reasonableness Evaluation: Section 25-8-503(8) of t/re revised (June /985) Colorado Water OualiN
Control Act required 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 furtherance of the policies set jonh in sections 25-8-192 and 25-8-104. "
The Colorado Discharge Permit System Regulations, Regulation No. 6/, further define this requirement under 6I.II
and smte.• "Where economic, em~ironnnental, public health and energy impacts to the public and affected persons have
been considered in the classifications and standards setting process, permits written to meet the standards may be
presumed to have taken into consideration economic factors unless:
a) Anew permit is issued N~here the discharge was not in existence at the time ojthe classification and standards
ndemakdng, 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 ntlemaking. "