5 Colo. Code Regs. § 1002-71.9
The specific statutory authority for this adoption is Section 25-8-105 and 25-8-205, C.R.S. (1982).
Control of both point sources and nonpoint sources of total phosphorus is essential to protect the quality and uses of Dillon Reservoir over the long term. This regulation is based on a state-local partnership in controlling total phosphorus. This relationship is described in the water quality management plan for the basin. These regulations provide the basis for State actions in protecting Dillon's quality. Local regulations will be used to control nonpoint sources. Taken together these State and local regulations provide a mechanism for maintaining the quality of Dillon at the levels observed in 1982. As noted in Section 4.1.6 , the Division will determine whether the local regulations are as effective as assumed or whether the allowed phosphorus discharges in Section 4.1.3 need to be adjusted to compensate for their ineffectiveness. It is anticipated that local governments will cooperate in providing information and assistance in determining their effectiveness.
The 1982 trophic status of Dillon Reservoir is considered adequate to maintain all existing uses over the long term. It is based on a total phosphorus loading of 10,162 pounds, an inlake total phosphorus concentration of 7.4 ug/l in the top fifteen meters as a growing season average, and a water yield from the watershed of 212,000 acre feet. At higher water yields the total phosphorus loading and inlake concentrations are expected to be exceeded. The assumptions regarding the sources and amount of loading for Dillon Reservoir are contained in Table I., attached hereto.
Total phosphorus loading varies with the water yield from the Dillon watershed. For the purpose of determining progress in achieving phosphorus controls, 1982 will be used as the base year. Mathematical relationships contained in the "Clean Lake Study of Dillon Reservoir in Summit County, Colorado" will be used to index future yields of phosphorus to the 1982 base year.
The water quality standard for total phosphorus in Dillon Reservoir of 7.4 ug/l is found at 5 CCR 1002-8. The phosphorus allocations contained in this regulation are expected to be adequate through 1990. The allocation will be reexamined at that time.
Adopted June 12, 1984
Effective July 30, 1984
FISCAL IMPACT STATEMENT
on the Assignment of a Phosphorus (P) Standard to the Dillon Reservoir, Segment 3, of the Blue River
As a man-made impoundment, Dillon Reservoir is a large water supply reservoir of over 1,800 surface acres and serves over half of the water supply needs of the Denver Water Board. This basic use of the impoundment would continue essentially unaffected by the phosphorus limitation decisions of the Commission. Although algae development as a result of the introduction of nutrients such as phosphorus can create a considerable taste and odor problem for a water supply use, this standard renders such concerns improbable. Agricultural uses, to the extent they can be linked to Dillon Reservoir, are most likely immune to the decisions regarding phosphorus. The two remaining classified uses, cold water aquatic life and recreation, may be affected to some extent by the standard set, so that is where the discussion of Dillon Reservoir beneficial use values is centered.
Evidence submitted to the Commission concerning the direct market value of the reservoir in relation to recreation and aesthetic considerations indicates that over $500,000 is spent annually by recreationists in Summit County for activities relating to Dillon Reservoir and at least eleven million dollars worth of real property can be linked to the presence and quality of the impoundment. In addition, the indirect sales generated by the primary expenditures are in excess of four million dollars annually. Finally, government revenues generated by both property taxes and sales linked to Dillon are in excess of $90,000 per year. An important consideration should be stressed regarding these figures. They represent only the economic value of Dillon Reservoir to Summit County. It can be safely assumed that a great deal of economic activity, indeed the majority of the direct expenditures associated with recreating at the lake, occur outside of Summit County. Boat and other equipment purchases likely occur at the county of origin.
Although the Commission is unaware of any specific study that estimates the non-market value of Dillon Reservoir, the Commission takes note of several considerations regarding the non-market side. Lake Dillon has had summer visitation as high as 428,380 visitor days. Economic theory and practice suggests that it is reasonable to assume that these recreationists would be willing to spend more than their direct expenditures to enjoy the resource by the marginal difference in value they associate with their experiences at Dillon as opposed to what they perceive as substitutes, if any. A highly conservative estimate of willingness-to-pay would be the difference in transportation costs between traveling to Dillon and these substitutes. Additionally, welfare economic theory indicates that recreation as a human activity has a value relating to the time spent by recreationists. Using this time value approach, the Commission hearing evidence that suggests that the non-market value of Dillon could potentially be over eleven million dollars annually.
The Commission does not consider the best available economic evidence to be a complete portrayal of the potential economic impacts of a phosphorus standard. The Commission recognizes that there is a level of uncertainty regarding the linkages between nutrient loading and algal development even greater uncertainty surrounding the linkages between increased algal development and impairment of beneficial uses. However, the Commission is aware that there are such linkages and that they may be quite significant. Evidence was presented to the Commission that estimated and economic impacts of eutrophication. Using the years 1988 and 1993 for projections, testimony indicated that direct expenditure loss would be #305,900 and $527,600 respectively. Indirect sales and property expenditures would still grow in Summit County, but at a significantly lesser rate than if the reservoir's quality remained unaffected. Non-market losses attributable to eutrophication would be $157,500 in 1988 and $181,500 in 1993. Using the time-value/opportunity-cost approach, the loss due to eutrophication would be over 1.4 million dollars in 1988 and over 1.6 million in 1993. With these figures in mind, the Commission takes note that the social and economic costs of allowing Dillon Reservoir to become eutrophic could be over two million dollars annually.
The Commission heard testimony and received evidence concerning the costs to maintain the quality of Dillon Reservoir and found that the worst case approach, with no non-point source trade-offs, would cost slightly over 1.5 million dollars annually. With point/non-point trading, however, this figure is reduced to just slightly over three quarters of a million dollars annually. The Commission notes that those who would bear these costs, the municipal discharges, recognize the costs as reasonable in relationship to the benefits to be maintained.
The Commission recognizes that the economic value of Dillon Reservoir is quite substantial as is indicated by the best available evidence. Combining the market and the non-market values, Dillon already has accounted for tens of millions of dollars with several million dollars being added annually. The Commission notes that the potential losses which could result from less stringent controls could seriously impact this value. The Commission also recognizes that the costs to prevent these losses are significantly less than the potential losses and that those who would bear the costs are in support of this phosphorus standard. Although the Commission would caution against the natural temptation to directly weigh these cost and value-loss measures in a cost/benefit approach because the beneficial use values may be understated to a significant degree, these figures nonetheless demonstrate that maintaining the water quality at Dillon Reservoir is quite defensible on economic grounds. For these reasons the Commission finds that it has acted responsibly and that this regulation is economically reasonable.
5 CCR 1002-71.9