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C.-: %t.(')R.41)ti 1).7 PA :7J1[ -, %T OFPUBLIC IIL' 1LT1f A,VD !,`.61RC�.`;tll \T, lT;rtcr �htcrltn Cont-()I Division
<br />Rationale — Pgoe 7, Permit ,Vo CO- 0000131
<br />Ili. Acute WET Limits — Outfall 015: Mine drainage from coal mines in Colorado has shown toxicity to aquatic life
<br />in some cases. On this basis, the potential for toxicity exists for this outfall. The permittee will be required to
<br />conduct routine monitoring for acute toxicity using fathead minnows The permittee conducted an Aquatic
<br />Impairment Study in 1995 for ou fa11011 to determine whether the cause of toxicity to Ceriodaphnia V., which
<br />was determined to be total dissolved solids (TDS), was impacting the receiving water. The Division and EPA
<br />reviewed this study and determined that there was no discernible impact It was further determined that future
<br />testing using Ceriodaphnia sp. would be of little value. Thins, WET testing of Ceriodaphnia sp. was waived for
<br />outfall 011. The permittee indicates that the water quality of outfall 015 is similar to that of ou fall 011 and that
<br />toxicity would be exhibited only by TDS The Division has reviewed the available quality data and agrees with
<br />the permittee. On this basis, the waiver of Ceriodaphnia sp. testing is extended to ou fall 015.
<br />Oxbow Mining, LLC has conducted acute toxicity testing for fathead minnows for several years at outfal1011
<br />and has demonstrated that at a concentration of 100% effluent, the samples are not lethal to 50% of the
<br />organisms. Thus, the facility has demonstrated that it can meet an acute toxicity limit of L Cso >100 %, and this
<br />limit will become effective immediately.
<br />The permittee is required to conduct quarterly monitoring consistent with the frequency specifications in the
<br />Colorado Water Quality Control Division Biomonitoring Guidance Document dated July 1, 1993, the results of
<br />which are to be reported as an LCso., which is the concentration at which 50% or more of the organisms die. If
<br />the LCso occurs in a concentration of less than or equal to 100% effluent, the permittee is required to comply
<br />with the specifications identified in Part I.A. of the permit.
<br />iv. General Information: The permittee should read the WET testing section of Part I.A. of the permit carefully.
<br />The permit outlines the test requirements and the required follow -up actions the permittee must take to resolve
<br />a toxicity incident. The permittee should read, along with the documents listed in Part I.Af the permit, the
<br />.,. Colorado Water Quality Control Division Biomonitorin-e Guidance Document dated July 1, 1993. This
<br />document outlines the criteria used by the Division in such areas as granting relieffrom WET testing, modifying
<br />test methods and changing test species. The permittee should be aware that some of the conditions outlined
<br />above maybe subject to change if the facility experiences a change in discharge, as outlined in Part I1A.2. of
<br />the permit. Such changes shall be reported to the Division immediately.
<br />v. Outfalls 007, 009. 010. 012, 013 014 016 017 and 018: Ou falls 007, 009, 010, 012, 013, 014, 016, 017 and
<br />018 at the Sanborn Creek Mine and Elk Creek Mine wastewater treatment facilities do not receive a significant
<br />volume of toxic or industrial wastes and, in accordance with Regulation No. 61 Section 61.8(2)(b)(i)(B) of the
<br />"Colorado Discharge Permit System Regulations' the discharge does not have the reasonable potential to
<br />cause, or measurably contribute to, an excursion above any narrative standards for water quality. Therefore,
<br />WET testing is not a requirement for these ou falls. However, the Division reserves the right to reopen the
<br />permit to include WET testing, should facility conditions change or if new information becomes available.
<br />3. Stormwater: Stormwater from active or inactive coal mining operations that has been contaminated by contact with any
<br />overburden, raw material, intermediate products, finished products, byproducts or waste products located on the site of
<br />such operations is required to be covered by a Colorado Discharge Permit System (CDPS) permit in order to be
<br />discharged to State waters. This coverage may be obtained under either a CDPS Industrial Wastewater Discharge
<br />Permit or a CDPS Stormwater Discharge Permit. For facilities that have individual CDPS permits for discharge of
<br />process water, any applicable stormwater provisions can then be included in individual CDPS permits. The individual
<br />permit for discharge of process water for the Sanborn Creek Mine and Elk Creek Mine, CDPS permit (No. CO-
<br />0000132), contains stormwater provisions that differ from the provisions of the process waterportion, and are laid out
<br />in Part I.D.2 of the permit. Under the terms of the combined individual permit (CO- 0000132), Oxbow Mining, LLC will
<br />be authorized to discharge stormwater associated with industrial activity into waters of the State of Colorado.
<br />The terms and conditions of this permit, as related to stormwater discharges, include:
<br />a Senreeation ofStormwater Discharges: All discharges covered by the stormwater portion of this permit shall be
<br />composed entirely ofstormwater (except as discussed at Part I D. 2.d 2 of the permit). Stormwater which mixes with
<br />any process water is subject to process water controls. Discharges from sources other than stormwater must be
<br />addressed by the process water controls in this CDPS permit.
<br />b Storm water Management Plans (SWMPs): The put pose of a SWiVIP is to ulentify possible pollutant sources to
<br />storm water and to set out best management practices that, when implemented, will reduce or eliminate any possible
<br />Last Rev,scd 412812004
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