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COLORADO DEPARTMENT OF PUBLIC HEALTH AND ENVIRONMENT. Water Quality Control Division Rationale, Page 5, COG-0500000 Sand and Gravel General Permit 1, pH - This parameter is limited by Water Quality Standards as the water quality standards of 6.5-9.0 s. u. range are more stringent than those specified under the Regulations for Effluent Limitations. 2. Selenium -The permit writer will review the application and determine if selenium must be limited and/or monitored to protect the classified uses assigned to the receiving water. If required, the permit writer will set these limitations equal to the appropriate water-quality standards. Selenium will be considered a pollutant of concernfor facilities operating in areas of shale deposits containing selenium (e.g. Mancos). 3. Metals- The permit writer will review the application and determine if metals parameters must be limited and/or monitored to protect the classified uses assigned to the receiving water. If required, the permit writer will set these limitations equal to the appropriate water-,quality standards. As many water quality standards for metals are listed as TVS, and based upon an equation dependent on the hardness of the receiving stream, the permit writer will obtain hardness data to-determine the appropriate metals limitations where appropriate. 4. Organics- The permit writer will review the application and determine if any organic parameters must be limited and/or monitored to protect the classified uses assigned to the receiving water. If required, the permit writer will set these limitations equal to the appropriate water-quality standards. S. Chemicals- The addition of chemicals (including release agents) to the discharge is not allowed unless expressly authorized by the Division. A release agent is a substance used to aid in the separation of the desired material from the substrate, and must be disclosed. To approve a chemical, the Division must have the associated MSDS sheet(s) provided with the application. If authorized all chemicals must be used and stored in accordance with the manufacturers' recommendations and in accordance with any applicable state or federal regulation. d. Salinity Requirements - All permit actions for discharges to surface waters in the Colorado River Basin must include salinity monitoring. Accordingly, the permit writer will perform an analysis, as set out in the paragraphs that follow, to determine which salinity requirements apply pursuant to the requirements of Section 61.8(2)(1) of the Colorado Discharge Permit System Regulations(Regulation No. 61). Multiple discharges covered from a single facility are subject to the limitation that would apply if there were a single discharge point. Based on the effluent data in the application from a new facility, the permit writer will make an assessment of the expected salinity load in the discharge (from concurrent flows at all outfalls) and if less than 1 ton/day or 366 tonsfyear, the calculation will be documented in the issued certification. For facilities discharging less than this threshold, quarterly monitoring will be required, as existed in the previous permit. For facilities that exceed the I ton/day or 366 tons/year threshold, a TDS limitation will be applied in the permit, unless the permittee demonstrates that it is not practicable to prevent the discharge of all salt. The Division will decide on this exception prior to the start of discharge and may require further actions by the permittee to reduce the salt load before approval of the discharge. In conformance with section 61.8(2)(1)(i)(A) of the Colorado Discharge Permit System Regulations. the permittee must submit a report that documents whether it is feasible to treat to these levels. The Salinity Regulations allow for a waiver of TDS limitations upon submittal of a report that demonstrates that achievement of zero salt loading or, in the event that is not achievable, discharge of less than one ton per day, is not economically feasible. There is no record that the permittee has previously submitted this report. If a report has previously been submitted, the permittee should submit a copy of this report. Quarterly monitoring for total dissolved solids will continue regardless. In conformance with the Colorado Discharge Permit System Regulation (Regulation No. 61). existing permits for discharges to the Colorado River basin incorporate total dissolved solids (TDS)as the monitoring parameter for compliance with the salinity requirements. Electrical conductivity (EC) may be substituted for TDS if a constant correlation exists between TDS and EC is established for the discharge, based on 5 paired samples, and approved by the permit writer. e. Phosphorus Regulations -Additional limitations for phosphorus may apply to discharges to surface waters in four watersheds - Dillon Reservoir, Cherry Creek Reservoir, Chatfield Reservoir, and Bear Creek Reservoir. Wasteloads (e.g., phosphorus) have been allocated in these regulations to various point and non point sources that discharge on these watersheds. If a discharge is to one of these areas, as defined in Regulations 71, 72, 73, and 74, the permittee will be required to obtain a wasteload allocation from the appropriate authority prior to certification under this general permit. f. Antidegradation -As set out in The Basic Standards and Methodologies of Surface Water, Section 31.8(3)(c)(ii)(C), an antidegradation analysis is required for all waters not designated as Use Protected, except in cases where the regulated activity 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 100:1 or more. Discharges permitted under this general permit are not normally temporary or short-term, thus, these discharges are not