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COLORADO DEPARTMENT OF PUBLIC HEALTHAND ENVIRONMENT, Water Quality Control Division
<br />Rationale, Page 9, COG-0850000 Coal Mining General Permit
<br />For facilities that exceed the 1 ton/day or 366 day/year threshold, TDS limitations will be applied in the permit, unless the
<br />permittee demonstrates that it is not practicable to prevent the discharge of all salt. The Division will decide on this exception
<br />prior to the start of discharge and may require further actions by the perntittee to reduce the salt load before approval of the
<br />discharge. In conformance with section 61.8(2)(1)(i)(A) of the Colorado Discharge Permit System Regulations, the permittee
<br />must submit a report that docztments whether it is feasible to treat to these levels. The Salinity Regzlations allow for the
<br />waiver of TDS limitations upon submittal of a report that demonstrates that achievement of zero salt loading or, in the event
<br />that is not achievable, discharge of less than one ton per day, is not economically feasible. There is no record that the
<br />permittee has previously submitted this report. If a report has previously been submitted, the permittee shoz~ld submit a copy
<br />of this report. Quarterly monitoring for total dissolved solids will continue regardless.
<br />In conformance with the Colorado Discharge Permit System Regulation (Regulation No. 61), existingpermits for discharges to
<br />the Colorado River basin incorporate total dissolved solids (TDS)as the monitoring parameter for compliance with the salinity
<br />requirements. Electrical conductivity (EC) may be substituted for TDS if a constant correlation exists between TDS and EC is
<br />established for the discharge, based on 5 paired samples, and approved by the permit writer.
<br />e. Phosphorus Regulations -Additional limitations for phosphorus may apply to discharges to surface waters in foztr watersheds
<br />-Dillon Reservoir, Cherry Creek Reservoir, Chatfield Reservoir, and Bear Creek Reservoir. Wasteloads (e.g., phosphorus)
<br />have been allocated in these regulations to various point and non point sources that discharge to these watersheds. If a
<br />discharge is to one of these areas, as defined in Regulations 71, 72, 73, and 74, the permittee may be required to obtain a
<br />wasteload allocation from the appropriate authority prior to certification under this general permit.
<br />f. Antide~radation -Asset out in The Basic Standards and Methodologies of Surface Water, Section 31.8(3)(c)(ii)(C), an
<br />antidegradation analysis is required for all waters not designated as Use Protected, except in cases where the regulated activity
<br />will result in only temporary or short term changes in water quality, or where the ratio of the low flow to the facility flow is
<br />100.•1 or more. Discharges permitted under this general permit are not normally temporary or short-term, thus, these
<br />discharges are not exempted from an antidegradation review. Based on the information and data in the application, the permit
<br />writer will make an assessment of the low flow dilution ratio of the discharge to determine if antidegradation applies.
<br />Under this general permit, an antidegradation (AD) limit will be calculated as I S% of the Water Quality Standard. The
<br />permittee would then have the choice of this AD limit, or of anon-impact limitation (1VIL). The NIL is either the limitation
<br />contained as of September 2000, or maybe be determined by the use of an implicit limitation if a previous limit did not exist.
<br />The implicit limit is determined as the maximum e, ffuent concentration in the two years prior to September 2000 (later data may
<br />be substituted on a case by case basis if data is unavailable from this time period). Alternately, if data does not exist, a
<br />compliance schedule may be added to the permit to obtain such data, to determine the implicit limitation, and the permittee will
<br />be required to regz~est an amendment to the certification to evaluate the implicit limitation and the final antidegradation based
<br />of luent limit. An individual permit will be required where the permittee requests consideration of dilution and ambient water
<br />quality.
<br />In addition, the permittee may elect to perform an alternatives analysis. As this may be subject to public notice requirements, an
<br />individual permit will be required. See Regulation 31.8(3)(d) and the Division's Antidegradation Guidance document for more
<br />information regarding an alternatives analysis.
<br />g. Whole Effluent Toxicity (WET1-The Water Quality Control Division has established the use of WET testing as a method for
<br />identifying and controlling toxic discharges from wastewater treatment facilities. WET testing is being utilized as a means to
<br />ensure chat there are no discharges ofpollz~tants "in amounts, concentrations or combinations which are harmful to the
<br />beneficial uses or toxic to humans, animals, plants, or aquatic life" as required by Section 31.11 (1) of the Basic Standards and
<br />Methodologies for Surface Waters.
<br />The Division has found that discharges of pit pumpage, spoils spring water and similar sources from coal mines at similar sites
<br />have exhibited effluent toxicity and therefore WET limitations may be included in this permit for wastewater from coal mining
<br />operations. Wastewater from outfalls that contain surface runoff only will not be subject to WET testing regz~irements.
<br />Chronic WET testing will normally be incorporated into this permit. An exception may be made where the receiving stream has
<br />a low flow of zero in all months, and when the discharge is intermittent This exception is being made as a zero low flow stream
<br />will not nornially contain water and the discharge does not flow continuously, therefore, chronic conditions are not likely to
<br />occur. The exception shall be granted on asite-speck basis. In the case of this exception, acute WET limits will be added to
<br />the certification.
<br />h. Threatened and Endangered Species -The US Fish and Wildlife Service and the Division have entered into a Memorandum of
<br />Agreement (MOA) regarding discharges to federal T&E listed waters. Is this MOA, a permittee that discharges to a T&E water
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