5 Colo. Code Regs. § 1002-72.15
The Colorado Water Quality Control Commission adopted a phosphorus standard of 0.035 mg/l for Cherry Creek Reservoir on August 14, 1984. The Statement of Basis and Purpose for the 0.035 mg/l phosphorus standard (5 C.C.R. 3.8.11) notes that the standard was based upon water quality data and hydrologic conditions of 1982.
Control of both point and nonpoint sources of total phosphorus is essential to protect the quality and uses of Cherry Creek Reservoir over the long term. This regulation is based on a state/local partnership in controlling total phosphorus. This relationship is described in the Upper Cherry Creek Basin Water Quality Management Plan. These regulations provide the basis for state actions in protecting Cherry Creek Reservoir's quality. Local regulations will be used to control nonpoint sources. Taken together, these state and local regulations provide a mechanism for protecting the quality of Cherry Creek Reservoir, given modeling based upon the hydrologic condition of 1982.
Total phosphorus loading varies with the water yield from the Cherry Creek basin watershed. For the purpose of determining progress in achieving phosphorus controls, 1982 will be used as the base year. Mathematical relationships contained in the Cherry Creek Clean Lakes Study will be used to index future yields of phosphorus to the 1982 base year. At higher water yields the totals phosphorus loading and inlake concentrations may be exceeded. The 14,270 pounds equate to the inlake total phosphorus standard of 0.035 mg/l as a growing season average, and an inlake chlorophyll a concentration of 15.0 ug/l.
Total annual phosphorus pounds of 14, 270 are based upon the number and type of wastewater treatment facilities and land uses described in the Upper Cherry Creek portion of the 208 Water Quality Plan. These total annual pounds of phosphorus were determined through the use of the Canfield-Bachman model as described in the plan.
The allocation of phosphorus pounds for point source discharges are predicated upon nonpoint source controls, as outlined in Section 4.2.6 , being implemented throughout the basin and effectively removing 50% of the nonpoint source pollution. The purpose of Section 4.2.6 is to encourage a basin-wide approach to phosphorus controls. If the requirements of this provision are not met the Commission will consider the adoption of control regulations or permit requirements to insure compliance.
5 CCR 1002-72.15