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COLORADO DEPARTMEM OF HEALTH, Water Quality Control Division <br />Rationale -Page 4. Permit No. COG-500000 <br />V. TERMS AND COND177ONS OF PERMIT <br />batch plants located m any facility otherwise covered by this general permit: <br />Table V/-I - Ejjluent limits <br />Parameter <br />Limit Rationale <br />Flow, MGD Report a/ NA <br />TSS, mg/l 30/45 b/ State Ejjluem Regulations <br />pH, s. u. 6.5-9.0 c/ Water Quality Stardardr <br />Oil and Grease, mg/l 10 a/ State Effluem Regulations <br />Toro! Dissolved Solids, mg/l Report a/ Salinity Regulations <br />(Colo. River Bann only) <br />Total Phosphorus (as P), mg/l Report a/d/ But Professional Judgment <br />a/ Daily Maximum <br />b/ 30-Day Average/7--Day Amage <br />c/ Minimum-Maximum <br />d/ Phosphorus monitoring is required only for f~cilitier which discharge imo the following drainage basins: Chcrry Creek basin, <br />Chatfield Reservoir downstream of the USGS gage m Waterton and on Plum Creek, Dillon Reservoir basin (i.e., Ten Mile <br />Creek, Snake River, Blue Rim, all tributaries to the Dillon Reservoir), and Bear Creek basin. See the individual <br />Ccrtrfication Rationale for a determination as to whether monitoring is required. <br />b. Mineral mining and pranssing poim soum category - 40 CFR 436 - subparts E (gypsum), F (asphaltic <br />mineral), G (asbestos and wollartoniteJ, J (barite), K (fluorspar), L (salines from 6rinc lakes), M <br />(boraxJ, N (potash), D (sodium suljmeJ, V (bemonite), W (magncsite), X (diatomite), Y (fade), Z <br />(novaculite), and AF (tripoliJ; and asphalt batch plants located at any facility otherwise covered by this <br />genera! permit: <br />Limits -There shall be na discharge of process wastewater imo state waters. Discharge steal! consist of <br />stormwater only. <br />c. Mineral mining and processing poim source category - 40 CFR 436 -subpart AL (graphite): The <br />discharge of process wastewater from graphite mines is not covered by this permit. (Set Section V.A.2.d <br />of the Rationale.) <br />2. Discussion oFLimitmions: <br />a. Extcptians !o Federal Limits: The 40 CFR 436 includes some efffuem limitmions which are not as stria <br />ar those listed here. For example, the phosphate rock 7SS limit is less stria, and for many of the <br />subcategories which stare 'no discharge of process wastewmer,' an exemption to that limit is provided <br />during certain precipitation events and in conjunction with other conditions. However, this permit does <br />not include thue rclaxed limits. This it a general permit, designed to cover the widest possible range of <br />facilities with similar wastewater charaaeristits. In effcaively achieving this broad coverage, the permit <br />must also be relatively simple. Therefore, some of the more individualistic or complex permit limitations <br />are not included in this permit. <br />The Division does not belin+e that there are a sufficiemly large number of such facilities in Colorado to <br />warram including the exemptions in this general permit. If a percolate wishcs to take advamage ojthese <br />exemptions, the percolate must apply jot an individual permit. <br />b. Total Suspended Solids (T'SS).• The previous permit included 7SS limits based on the State Effluent <br />Regulations, 10.1.4, of 30 mg/l (30 day average) and 45 mg/l (7 day averageJ. Howe~+er, the definitions <br />of a 30 day amage or 7 day average colkd jot 3 samples to be taken in a 30 day or 7 day period, <br />