COLORADO DEPARTMENT OF PUBIC HEALTH AND ENVIRONMENT
WATER QUALITY CONTROL COMMISSION
5 CCR 1002-71
REGULATION NO. 71
DILLON RESERVOIR CONTROL REGULATION

ADOPTED:
June 12, 1984
EFFECTIVE: July 30, 1984
AMENDED:
June 1, 1987
TRIENNIAL REVIEW: June 1, 1987
TRIENNIAL REVIEW: June 5, 1990
TRIENNIAL REVIEW: December 7, 1993
AMENDED:
May 13, 1996
EFFECTIVE: June 30, 1996
AMENDED:
July 14, 1997
EFFECTIVE: August 30, 1997
TRIENNIAL REVIEW: May 8, 2000
AMEMDED:
January 8, 2001
EFFECTIVE: March 2, 2001
TRIENNIAL REVIEW: March 14, 2003
AMENDED:
September 8, 2003
EFFECTIVE: November 30, 2003
AMENDED:
April 9, 2007
EFFECTIVE: May 30, 2007

1

 COLORADO DEPARTMENT OF PUBIC HEALTH AND ENVIRONMENT
WATER QUALITY CONTROL COMMISSION
5 CCR 1002-71
REGULATION NO. 71
DILLON RESERVOIR CONTROL REGULATION
71.0

DILLON RESERVOIR CONTROL REGULATION

71.1

AUTHORITY
The Water Quality Control Commission is authorized by section 25-8-205, C.R.S., to promulgate
control regulations to describe prohibitions, standards, concentrations, and effluent limitations on
the extent of specifically identified pollutants that any person may discharge into any specified
class of state waters.

71.2

DEFINITIONS
See the Colorado Water Quality Control Act and other Water Quality Control Commission
regulations for additional definitions.

71.3

(1)

"NONPOINT SOURCE" - any activity or facility other than a point source from which
pollutants are or may be discharged.

(2)

"DISPERSAL SYSTEM" - a system for the disposal of effluent, after final treatment in an
individual sewage disposal system, by a method which does not depend upon or utilize
the treatment capability of the soil.

(3)

“RESERVE POOL” – consists of total phosphorus credits that have not been allocated to
any discharger. The source of these credits may be previous phosphorus allocations for
facilities no longer in operation, reductions in existing discharger phosphorus allocations
listed in 71.3, nonpoint source control projects as described in 71.5, or other sources that
do not result in an increase to the total phosphorus load to Dillon Reservoir.

WASTELOAD ALLOCATION FOR TOTAL PHOSPHORUS DISCHARGE
The dischargers listed below shall not discharge more than the indicated amounts of total
phosphorus in any consecutive twelve month period except as provided in section 5 below.
Discharge

Allowed Phosphorus Discharge (lb./yr.)

Major Municipal
Breckenridge SD
Copper Mt Consolidated Metro District
Frisco SD
Snake River Plant
TOTAL

708.8
218
341
340
1,607.8

Minor Domestic
Bekkedal Subdivision
High Country Lodge

2.5
1.7

1

 71.4

MUNICIPAL AND DOMESTIC EFFLUENT LIMITATIONS

Keystone A-Basin
Keystone Summit House
Summit Motor Inn
Vail Pass Rest Stop
TOTAL

11.4
4.4
2.7
3.9
26.6

Reserve Pool

66.9

GRAND TOTAL
71.4

71.5

1701.3

MUNICIPAL AND DOMESTIC EFFLUENT LIMITATIONS
(1)

No new or existing municipal or domestic wastewater treatment plant treating more than
2,000 gallons per day in the Dillon Reservoir watershed shall discharge an effluent with a
total phosphorus concentration greater than 0.5 mg/l total phosphorus, as a daily
maximum. In the case of discharges from a dispersal system, this concentration must be
documented either entering or leaving the dispersal system. Notwithstanding the
discharge allowed by this subsection, the dischargers listed in section 3 shall not
discharge more than the amounts listed therein.

(2)

The total phosphorus discharged in the Dillon Reservoir watershed by municipal sources
and domestic sources, as shown in section 3, shall not exceed 1,634.4 pounds per year
except as provided in section 5 below.

(3)

Annual phosphorus allocations for site approvals and permits issued to new facilities after
July 30, 1984 shall be based on total phosphorus effluent quality of 0.2 mg/l based on a
30-day average and the design capacity of the treatment plant. However, such
allocations may only be used if they are offset by discharge credits for nonpoint source
controls obtained pursuant to section 5, below.

(4)

Subject to the other provisions in Section 71.4, new or existing wastewater treatment
facilities may obtain an additional phosphorus allocation for temporary or permanent use
by:
a.

Controlling nonpoint sources as outlined in Section 71.5(5) below;

b.

Utilizing available credits in the Reserve Pool; and

c.

Acquiring credits from another existing point source wasteload allocation, where
the existing wasteload allocation is reduced by a corresponding amount.

DISCHARGE CREDITS FOR NONPOINT SOURCES CONTROLS
(1)

The Water Quality Control Division is authorized by this regulation to issue point source
discharge permits incorporating point sources--nonpoint sources tradeoffs in the Dillon
reservoir watershed. Point source dischargers may control nonpoint sources of
phosphorus and receive a credit toward their point source phosphorus allocation.

(2)

Credit shall only be granted for control of nonpoint sources in existence as of July 30,
1984. The amount of credit will be determined by using site-specific data or a water
quality modeling approach for Dillon Reservoir, with review and approval by the Division.
One pound of credit will be granted for each two pounds of phosphorus controlled.

1

 71.6

(3)

(4)

(5)

71.6

71.7

CONTROL OF NEW NONPOINT SOURCES

To receive such credit, a point source discharger must apply to the Division with the
following information demonstrating compliance with guidelines or regulations adopted by
the Commission for control of nonpoint sources:
(a)

design specifications for the nonpoint source controls for which credit is sought;

(b)

the amount of total phosphorus which will be controlled;

(c)

proposed construction requirements;

(d)

proposed operation and maintenance requirements to assure continuous control;
and

(e)

proposed monitoring and reporting requirements.

The permit will specify the following conditions at a minimum:
(a)

the amount of point sources credit;

(b)

construction requirements;

(c)

monitoring and reporting requirements; and

(d)

operation and maintenance requirements.

No credits for nonpoint source controls shall be granted or incorporated into point source
permits under this section 5 unless and until regulations have been adopted and
implemented by local governments in the County, which regulations control contribution
of nonpoint phosphorus from new earth disturbance and the nonpoint source runoff
associated therewith.

CONTROL OF NEW NONPOINT SOURCES
(1)

The allowed point source phosphorus allocations in section 3 are based on the
assumption that Summit County and local governments in Summit County adopt
regulations that require best management practices or other methods of phosphorus
control which will result in pound for pound mitigation for all new nonpoint sources of
phosphorus. If the Division determines that nonpoint source controls are not adequate to
prevent exceedance of the phosphorus standard for Dillon Reservoir, the Commission
may reconsider the allowed phosphorus allocations in section 3.

(2)

The Division will report periodically to the Commission and to Summit County Local
Governments on the results of any inspections conducted to evaluate nonpoint source
controls.

MONITORING OF PHOSPHORUS IN DISCHARGES
(1)

Point Sources. All permits for point source discharges shall contain monitoring
requirements for total phosphorus. The frequency of monitoring shall be at least once
per month. The requirements shall provide for a 30-day average 7-day average, daily
maximum, or other measurement of phosphorus concentrations and loadings, as
determined by the Division.

2

 71.8

(2)

71.8

Nonpoint source controls. All permits granting credit for nonpoint source controls shall
contain monitoring requirements in accordance with guidelines and regulations for such
controls adopted by the Commission.

REPORTING
(1)

71.9

REPORTING

The Summit Water Quality Committee shall provide to the Water Quality Control Division
any information on water quality monitoring, point source loadings, nonpoint source
loadings and the status of nonpoint source control efforts, status of trades approved,
model updates, recommendations on any new or proposed expansion of wastewater
treatment facilities, and recommendations for improving water quality, as it becomes
available.

BASIS AND PURPOSE
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
Effective

June 12, 1984
July 30, 1984
FISCAL IMPACT STATEMENT
on the Assignment of a Phosphorus (P) Standard
to the Dillon Reservoir, Segment 3, of the Blue River

3

 71.9

I.

BASIS AND PURPOSE

INTRODUCTION
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.

II.

FISCAL IMPACT - BENEFITS
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. Nonmarket 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.

4

 71.10STATEMENT OF BASIS, SPECIFIC STATUTORY AUTHORITY AND PURPOSE NOVEMBER, 1995
RULEMAKING

III.

FISCAL IMPACT - COSTS
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.

IV.

CONCLUSION
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.

71.10

STATEMENT OF BASIS, SPECIFIC STATUTORY AUTHORITY AND PURPOSE NOVEMBER,
1995 RULEMAKING
The provisions of sections 25-8-201(1)(c) and (2); and 25-8-205 C.R.S., provide the specific
statutory authority for adoption of the attached regulatory amendments. The Commission also
adopted, in compliance with 24-4-103(4) C.R.S., the following statement of basis and purpose.

BASIS AND PURPOSE
This hearing was requested by the Summit Water Quality Committee. The purpose of the
request was to make several changes to the regulation. The first was to update point source
phosphorus allocations to reflect point source--nonpoint source tradeoffs that have occurred and
to remove point source allocations for minor domestic facilities which have been connected to
local sewer systems. These specific changes include adding eleven pounds to the Breckenridge
Sanitation District's phosphorus allocation in the regulation as credit for removing the nonpoint
source septic system in the LakeView Meadows subdivision. These credits are already reflected
in the Breckenridge Sanitation District's CDPES discharge permit. An additional 0.5 pounds of
credit is given for the Breckenridge Sanitation District's participation in the removal of the
nonpoint source septic system associated with the Breckenridge Ski Areas Peak 8 Restaurant.
Another change in point source phosphorus allocations results from combining the allocations for
the Quandry and Skier's Edge Condominiums, since these units are now served by a single
wastewater treatment facility and have a single discharge permit. The other changes are the
removal of the allocations for septic systems for Breckenridge Ski Areas Peaks 8 and 9, as these
areas are now serviced by the Breckenridge Sanitation District's main treatment plant, and
removing the allocations for the septic systems serving the Ski Tip Ranch and Snake River
Saloon because these areas are now serviced by the Snake River Wastewater Treatment Plant.
The second significant change in this rulemaking was to require that the determination of point
source phosphorus allocation credits for nonpoint source controls, as outlined in Section 4.1.5,
will be based on site-specific data on the amount of nonpoint source phosphorus controlled or on

5

 71.10STATEMENT OF BASIS, SPECIFIC STATUTORY AUTHORITY AND PURPOSE NOVEMBER, 1995
RULEMAKING

use of a water quality modeling approach which approximates the phosphorus poundage which
has been reduced. Previously these credits were to be "determined by guidelines or regulations
adopted by the Commission". However, the guidelines which have been used address only the
procedural aspects of implementing a point-nonpoint source phosphorus trade. No methodology
for quantifying credits for nonpoint source controls has been provided. Much of the rationale for
adopting the in-lake standard and associated phosphorus allocations was based on information
contained in the "Clean Lake Study of Dillon Reservoir in Summit County, Colorado" which
includes the Lake Dillon Water Quality model. It is therefore appropriate and consistent to
determine credits using the loading equations contained in this model, other appropriate modeling
of phosphorus reductions, or site-specific data for the nonpoint source control project which is the
basis for the point source credit request.
Since the Clean Lakes Study was completed the model has been updated to reflect information
generated by the on-going local water quality monitoring efforts. As a result of re-calibration of
the model it is estimated that a total annual phosphorus load in excess of 8,350 pounds, in
combination with a water yield from the watershed of 212,000 acre feet, will result in exceeding
the water quality standard of 7.4 ug/l total phosphorus, which is a growing season average for the
months of July, August, September, and October. Local water quality management efforts are
focused on preventing phosphorus loads from exceeding this quantity. Because it is likely that
monitoring will continue and that the model will be re-calibrated in the future to reflect additional
information, local entities requested that the credits be based on the most recent version of the
Lake Dillon Water Quality Model or a similar water quality, loading-based model that fulfills the
same, basic elements. The revisions adopted assure that this option is available, although not
mandated. The Division is required to review and approve any credits, if the request meets the
criteria outlined in 4.1.5 (3).
The third significant change made in this regulation revision deals with Section 4.1.6 Control of
New Nonpoint Sources. Language is now included which states that the point source
phosphorus allocations are based pm the assumption that county and local governments require
controls that achieve pound for pound mitigation for all new nonpoint sources of phosphorus.
The previous language in this section was unclear as to the intent for nonpoint phosphorus
control. Language was added to clarify that if the Division determines that nonpoint source
controls do not appear to be adequate to prevent exceedances of the Dillon Reservoir
phosphorus standard, then the Commission may reconsider the point source allocations. Any
evaluation data gathered by the Division on nonpoint source controls in Summit County will be
reported to the county or appropriate local governments. The sentence in the original rule about
the Division conducting periodic site inspections if at all possible was deleted as unnecessary,
although the Commission intends that the Division will monitor implementation of the rule to the
extent that resources permit.
The Commission also chose not to adopt in this hearing two proposals included in the hearing
notice. The original proposal would have established a "reserve pool" minor domestic point
source allocation for phosphorus. Discussion at the hearing raised issues regarding the
appropriate source of phosphorus for a reserve pool allocation, how the reserve pool would be
administered, and the disposition of removed allocations. Following further input from the
Division and the parties, the Commission has determined that is not necessary or appropriate to
establish a reserve pool at this time, particularly considering the difficulties in resolving these
issues.
The second proposal that the Commission chose not to adopt would have established a point
source to point source transfer mechanism for phosphorus allocations. Following further input
from the Division and the parties, the Commission has determined that it is not necessary or
appropriate to establish such a transfer mechanism at this time, particularly considering
unresolved issues regarding the potential impact of such a transfer mechanism on the total point
source phosphorus loadings to the reservoir.

6

 71.11STATEMENT OF BASIS, SPECIFIC STATUTORY AUTHORITY AND PURPOSE; JULY, 1997 RULEMAKING

PARTIES TO THE RULEMAKING HEARING
1.
2.
3.
4.
5.
6.

Summit Water Quality Committee
Ralston Resorts, Inc.
Intrawest/Keystone L.L.C.
City and County of Denver, Acting by and through its Board of Water Commissioners
Northwest Colorado Council of Governments
Grove Constructed Wetlands

71.11

STATEMENT OF BASIS, SPECIFIC STATUTORY AUTHORITY AND PURPOSE; JULY, 1997
RULEMAKING
The provisions of sections 25-8-202 and 25-8-401, C.R.S., provide the specific statutory authority
for adoption of the attached regulatory amendments. The Commission also adopted, in
compliance with section 24-4-103(4) C.R.S., the following statement of basis and purpose.

BASIS AND PURPOSE
The Commission has adopted a revised numbering system for this regulation, as a part of an
overall renumbering of all Water Quality Control Commission rules and regulations. The goals of
the renumbering are: (1) to achieve a more logical organization and numbering of the
regulations, with a system that provides flexibility for future modifications, and (2) to make the
Commission=s internal numbering system and that of the Colorado Code of Regulations (CCR)
consistent. The CCR references for the regulations will also be revised as a result of this hearing.
71.12

STATEMENT OF BASIS, SPECIFIC STATUTORY AUTHORITY AND PURPOSE; JANUARY,
2001 RULEMAKING

BASIS AND PURPOSE
This rulemaking is intended to update the regulation to reflect point source – nonpoint source
tradeoffs that have occurred in the Dillon Reservoir watershed and to combine all point source
allocations of the Breckenridge Sanitation District to a single total phosphorus allocation. These
changes include adding 40 pounds to the Copper Mtn. Consolidated Metro District’s phosphorus
allocation in the regulation as credit for the removal of nonpoint source septic systems in the Ten
Mile Creek drainage. These changes will not result in an overall increase in the total phosphorus
load to Dillon Reservoir because the increase in allowable point source load is offset by a two-fold
reduction in nonpoint source load.
Consolidation of Breckenridge Sanitation District (BSD) Phosphorus Allocations – BSD is the only
entity providing central sewer treatment service in the entire Blue River watershed upstream of
Dillon Reservoir. BSD currently owns and operates seven wastewater treatment facilities listed in
section 4.1.3 of the Control Regulation. Several of the BSD facilities have recently been
combined into a single more efficient treatment plant.
BSD has been a leader in phosphorus removal nationwide through a combination of advanced
treatment facilities and significant operational expertise. This rulemaking combines all total
phosphorus allocations for treatment facilities located in the BSD service area into a single total
phosphorus allocation to enable streamlined facility consolidation, flexibility in operation, and
improved reporting to the Division. A single total phosphorus allocation also updates the Control
Regulation to the current operations and permitting situation of the BSD. This request fits within
the original pollution control “bubble concept” outlined in the phosphorus management plan for
Dillon Reservoir and is wholly supported by the Summit Water Quality Committee.

7

 71.13STATEMENT OF BASIS, SPECIFIC STATUTORY AUTHORITY AND PURPOSE (September, 2003)

PARTIES TO THE RULEMAKING HEARING
1.

Summit Water Quality Committee

71.13

STATEMENT OF BASIS, SPECIFIC STATUTORY AUTHORITY AND PURPOSE (September,
2003)
The provisions of sections 25-8-202 and 25-8-401, C.R.S., provide the specific statutory authority
for adoption of the attached regulatory amendments. The Commission also adopted, in
compliance with section 24-4-103(4) C.R.S., the following statement of basis and purpose.

BASIS AND PURPOSE
Residential properties within the service area of the Frisco Sanitation District that have been
served by individual sewage disposal systems, were provided sewer service and connected to
the District's wastewater treatment system. The phosphorus load reduction achieved by sewering
these homes has been sold to the Copper Mountain Consolidated Metro District, which is located
in the Dillon Reservoir watershed and seeks to increase their annual allocation of phosphorus
allowed from their wastewater treatment facility.
The advanced treatment for phosphorus removal at the wastewater facility reduces the
phosphorus load per residence to a negligible amount. Studies done for in Summit County
indicate that a conservative estimate of phosphorus load per residential unit is one pound per
year from individual sewage disposal systems. The phosphorus from the individual systems are
considered a nonpoint source, and the residences have been confirmed as existing prior to 1984,
as required by 71.5 (2). The regulation provides that reduction of two (2) pounds of nonpoint
source phosphorus can be converted to one (1) pound of credit to a point source allocation.
There were 26 residences on individual sewage disposal systems that were connected to the
wastewater system of Frisco Sanitation District, which provides a point source allocation credit of
13 pounds per year. That credit was purchased from Frisco Sanitation by Copper Mountain
Consolidated Metro District. This purchase was done as an extension of the agreement between
Frisco Sanitation and Copper Mountain, whereby Copper Mountain purchased 40 lbs. of point
source credit in 1998/99.
The Commission received information in support of the 13 pound phosphorus credit from Summit
Water Quality Committee, Copper Mountain Consolidated Metro District, and the Frisco
Sanitation District. There were no comments in opposition to granting the 13 pound credit during
the written comment only hearing. The Commission approved the change to the point source
phosphorus allocation of Copper Mountain from 205 total pounds per year to 218 pounds per
year, and the increase of allowed total point source phosphorus load in the Dillon Reservoir
watershed from 1,621.4 pounds per year to 1,634.4 pounds per year.
71.14

STATEMENT OF BASIS, SPECIFIC STATUTORY AUTHORITY AND PURPOSE (Rulemaking
Hearing April 9, 2007 Effective May 30, 2007))
The provisions of sections 25-8-202 and 25-8-401, C.R.S., provide the specific statutory authority
for adoption of the attached regulatory amendments. The Commission also adopted, in
compliance with section 24-4-103(4) C.R.S., the following statement of basis and purpose.

8

 71.14STATEMENT OF BASIS, SPECIFIC STATUTORY AUTHORITY AND PURPOSE (Rulemaking Hearing April 9,
2007 Effective May 30, 2007))

BASIS AND PURPOSE
The Summit Water Quality Committee and WQCD agreed that the control regulation be amended
to include additional definitions and actions related to the current phosphorus trading provisions.
The specific amendments are as follows:
71.2

DEFINITIONS

A “Reserve Pool” was defined as total phosphorus credits that have not been allocated to
any discharger. This term will used in Section 71.4(4) for obtaining additional
phosphorus allocation by permitted dischargers.
71.3

WASTELOAD ALLOCATION FOR TOTAL PHOSPHORUS DISCHARGE

The Reserve Pool, as defined in Section 71.2, has been added to this list and has 66.9
phosphorus pounds assigned for an allocation. Pounds of phosphorus for this category
will come from other existing point source allocations listed in Section 71.3, or from
nonpoint sources as described in Section 71.5.
71.4

MUNICIPAL AND DOMESTIC EFFLUENT LIMITATIONS

Paragraph (4) was added to provide more flexibility in managing the reservoir water
quality. The paragraph describes how new or existing wastewater treatment facilities can
obtain additional phosphorus wasteload allocation through phosphorus trading as
described in Section 71.5, by utilizing credits in the Reserve Pool, or by acquiring
additional phosphorus allocation in a point source to point source trade with another
existing point source wasteload allocation described in Section 71.3.
71.8

REPORTING

This section was added to include reporting on various aspects of the control regulation
including the expansion of the phosphorus trading provisions. This information will be
used by the Division to evaluate the effectiveness of the phosphorus controls on Dillon
Reservoir and provide it to the Commission.
The Commission determined that the Reserve Pool can be supplied with phosphorus credits from
several past projects. These credits can be held in the Reserve Pool by the entity completing the
project for their own future use, sold or traded to another entity, or retired. The Phosphorus
Trading Guidelines being developed by the Summit Water Quality Committee, the Division, and
parties responsible for the phosphorus removal projects will guide how these credits may be
utilized in the future. All credits in the Reserve Pool have been calculated based on equations
and assumptions in the most recent version of the Lake Dillon Water Quality Model, and all are
subject to review and possible modification when the next version of the model becomes
available.
The Commission determined that the proposed amendments would not increase the total
allowable phosphorus load to Dillon Reservoir, or reduce the protection of designated uses
provided by the control regulation. The amendments would provide flexibility to the ongoing
phosphorus management strategies to address reservoir water quality.
PARTIES TO THE RULEMAKING HEARING
1.
2.

Summit Water Quality Committee
Vail Resorts Development Company

9

 71.14STATEMENT OF BASIS, SPECIFIC STATUTORY AUTHORITY AND PURPOSE (Rulemaking Hearing April 9,
2007 Effective May 30, 2007))

3,
4.

Intrawest Placemaking
Wright Water Engineers, Inc.

10