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Table 12: Physical and biological parameters, Colorado Recreational Aquatic Life Class 1 Clsss 2 Class 1 Class 1 Primary Secondsry Ccld Water Warm Water Parameter Contact Contact Biota , Biota Class 2 Agriculture Domestic Water Supply , D.O. (mg/l)(1)(8) 3.0 3.0 6.0(2) 5.0 , 3,0 3.0 7.0 (spawning) pH (Std. Unns) (3) 6.5-9.0 6,5-9.0 6.5-9.0 . 5.0-9.0 Suspended Solids(4) Temperature (C) Max 20 C, with Max 30 C, with . 3 C Increase(S) 3 C Increase (5) Fecal Coliforms per 200(6) 2000(6) . 2000 l00ml (Geometrio Mean) * To bE! established on a case~by..case basis (1) Standards for dissolved oxygen are i-day minimal unless speci~ed otherwise. For the purposes of permitting, dissolved oxygen may be modeled for average conditions of temperature and flow for the worst case time period. Where dissolved oxygen levels less than these levels occur naturally, a discharge shall not cause a further reduction in dissolved oxygen In receiving water. (2) A7.0 mglliter standard (minimum), during periods of spawning cir cold water fish, shali be set on a case-by-case basisas defined in the NPDES permit for those dischargers whose effluent would afrect fish spawning. (3) The pH standards of 6.5 (or 5.0) and 9.0 are an instantaneous minimum and maximum, respectively to be applied as effluent limits. (4) Suspended solid levels wili be controlied by Effluent Limitation Regulations, Basic Standards, and Best Management Practices (BMPs). (5) Temperature shall maintain a normsl pattern of diurnal and seasonal fluotuations with no abrupt changes and shall have no increase In temperature of a magnitude, rate, and duration deemed deleterious ,to the resident aquatic life. Genereliy, a maximum 3 degrees Celsius Increase over a minimum of a four-hour period, lasting for 12 hours maximum, is deemed acceptable for dischargers fluctuating in volume or temperature. Where temperature increases cannot be m,alntained within this range using BMP I BA TEA and BPWTT control measures, the Division will determine whether the resulting temperature increases preclude an aquatic life classification. (6) Fecal coliform Is an indicator only. It may Indicate the presence of pathogenic organisms; however, fecal coliform counts from agricu"ure or urban runoff may not indicate organisms detrimental to human heslth. The bacteria standard Is based on the geometrio mean of representative stream samples. (7) For drinking water with or without disinfection. (6) T~e dissolved oxygen criteria is intended to apply to the epilimniqn and metalimnlon strata of lakes and reservoirs. Dissolved oxygen in the hypolimnion may, due to the natural condttions, be less than the table criteria, No reductions In dissolved oxygen levels due to oontrollable sources Is aliowed. Taken from Colorado Water Quality Control Commission 1993a 46