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COLORADO DEPARTMENT OF PUBLIC HEALTH AND ENVIRONMENT, Water Quality Control Division
<br />_ Rationale -Page 7, Permit No. CO-0000132
<br />iii. Acute WET Limits - Outfa11015: 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 permiuee will be required to
<br />conduct routine monitoring for acute toxicity using fathead minnows. The perminee conducted an Aquatic
<br />/mpairment Study in 1995 jot outfal1011 to determine whether the cause ojtoxicity to Ceriodaphnia sn., 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 Ceriodanhnia sn. would be of lime value. Thus, WET testing of Ceriodaphnia sp. was waived for
<br />outfa11011. The perminee indicates that the water quality ofoutfa11015 is similar to that ofoutfa11011 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 Ceriodanhnia sp. testing is extended to outfal1015.
<br />Oxbow Mining, LLC has conducted acute toxicity testing forfathead minnows for several years at outfall 011
<br />and has demonstrated that at a concentration oj100% ejjluenr, the samples are not lethal to 50% ojthe
<br />organisms. Thus, the jacility has demonstrated that it can meet an acute toxicity limit of LCsa >700%, and this
<br />limit will become effective immediately.
<br />The perntittee is required to conduct quarterly monitoring consistent with the frequency specifications in the
<br />Colorado Water Oualtry Control Division Biomonitorin2 Guidance Document. dated July 1, 1993, the results of
<br />which are to be reported as an LCso-, which is the concentration ar which SO% or more ofthe organisms die. If
<br />the LCsv occurs in a concentration of less than or equal to 100• effluent, the permittee is required to comply
<br />with the specifications identified in Pan I.A. of the permit.
<br />iv. Generallnformation: The permittee should read the WET testing section of Part LA. of the permit carefully.
<br />The permit outlines the test requirements and the required follow-up actions the permitiee must take to resolve
<br />a toxicity incident. The permittee should read, along with the documents listed in Part I.A.f. the permit, the
<br />Colorado Water Oualiry Control Division Biomonitoring 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 may be subject to change if the jacility experiences a change in discharge, as outlined in Part Il.A.2. of
<br />the permit. Such changes shall be reported to the Division immediately.
<br />Out(alls 007. 009. 010. 012. 013. 014. 016. 017 and 018: Outfalls 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 sign cant
<br />volume ojtoxic 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 nor have the reasonable potential to
<br />cause, or measurably contribute ro, an excursion above any narrative standards for water quality. Therefore,
<br />WET testing is not a requirement for these outfalTs. 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: Siormwaterfrom 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 pe»nits 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 Eik Creek Mine, CDPS permit (No. C0.
<br />0000132), contains stormwater provisions that difJerfrom the provisions of the process water portion, and are laid out
<br />in Part LD.2 of the permit. Under the terms of the combined individual permit (C0.0000132), 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. SeQreration ofStormwater Discharges: AJl discharges covered by the stormwater portion of this permit shall be
<br />composed entirely ofstormwater (except as discussed at Part LD1.d.2 of the permit). Stormwater which mixes with
<br />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 />6. Stormwater Management Plans (SWMPs): The purpose of a SWMP is to identify possible pollutant sources to
<br />stormwater and to set out best management practices that, when implemented, will reduce or eliminate any possible
<br />Lost Revised: 3/!9/2004
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