C.R.S. § 25-8-304

(1) The owner or operator of any facility, process, or activity from which a discharge of pollutants is made into state waters or into any municipal domestic wastewater treatment works shall, according to standard procedures and methods prescribed by the division: (a) Establish and maintain records; (b) Make reports; (c) Install, calibrate, use, and maintain monitoring methods and equipment, including biological and indicator pollutant monitoring methods; (d) Sample discharges; (e) Provide additional reasonably available information relating to discharges into domestic wastewater treatment works.