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APPENDIX A

Regional Haze State Implementation Plan 

Periodic Review of Colorado RAVI Long Term Strategy 
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LONG-TERM STRATEGY REVIEW

OF 

COLORADO'S STATE IMPLEMENTATION PLAN 

FOR CLASS I AREA VISIBILITY PROTECTION

ADDRESSING REASONABLY ATTRIBUTABLE 

IMPAIRMENT

July 2007 

 (updated October 2007) 

I. STATE OF COLORADO’S PHASE I STATE IMPLEMENTATION PLAN FOR 

CLASS I VISIBILITY PROTECTION ADDRESSING REASONABLY 

ATTRIBUTABLE IMPAIRMENT 

The various elements of Phase I of Colorado’s Class I Visibility State Implementation Plan 

are spread throughout Colorado Air Quality Control Commission Regulation No. 3. All of the 

components of the Visibility SIP are important to long-term visibility protection of Class I areas 

in the State and are integrated in varying degrees into the LTS review and revision protocol. 

Therefore, each of the components is briefly discussed in this section. 

A. Existing Impairment. 

 The AQCC’s Regulation No. 3, Stationary Source Permitting and Air Pollution Emission 

Notice Requirements, includes provisions to address impairment within Class I areas reasonably 

attributable to existing major sources. 

Regulation No. 3 Part D §XIV.D provides for an affected FLM or the Division to certify 

visibility impairment in a Class I area due to an existing stationary source. Existing sources 

regulated under this program are those that were not in operation prior to August 7, 1962 nor for 

which construction was commenced on or after August 7, 1977, which have the potential to emit 

250 tons or more of an air pollutant regulated by the Division. 

The FLM or the Division may certify at any time that impairment exists in any Class I area. 
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If the Division reasonably attributes the impairment to an existing source, the Division must 

conduct a BART analysis and determine if additional emission limitations are required. If so, 

the source must apply for a BART permit from the Division. Once the permit is granted, the 

source must limit its emissions on a schedule not to exceed five years. At the time of Colorado’s 

Visibility SIP development, the FLMs did not indicate that potentially reasonably attributable 

types of visibility impairment were present in any of Colorado’s Class I areas. The Division 

concurred with the finding. However, in 1993 the USFS certified visibility impairment in the 

Mt. Zirkel Wilderness in northwest Colorado.1

 The certification has subsequently been resolved 

and is discussed below in section II.B.1.a. 

B. New Source Review. 

 Applicants for permits to operate as a major source must demonstrate that the proposed 

source will not have an adverse impact on visibility in any Class I area. Regulation 3 Part D 

§XIII.A sets forth a schedule for the participation of affected FLMs and consultation with the 

Division in the review process of such an analysis as part of the Prevention of Significant 

Deterioration (PSD) permitting application process. 

The Division is required to consider any FLM determinations that the proposed source would 

have an adverse impact on visibility in the Class I area (Regulation 3 Part D §V.A.6 and XIII.C). 

 The Division may independently make its own determination. If the Division does determine 

that its own or the FLM’s analysis demonstrates that an adverse impact would occur, the 

Division shall not issue the permit. 

In addition to the analysis, a source may be required to conduct monitoring to establish the 

condition of, and impact on, air quality related values (AQRVs) in the Class I area that may be 

affected. Monitoring can be required both before completing a permit application to construct 

and during the construction and operation of the source (Regulation 3 Part D §VI.A.3, §VI.A.4, 

§XIII.B). 

C. Consultation With Federal Land Managers. 

 Regulation No. 3 provides for participation by the FLMs in the new source review process. 

The FLMs may also make recommendations to the Division concerning integral vistas, identify 

impairment in any Class I area, and provide consultation concerning elements considered for 

inclusion in the monitoring strategy. The Division also is required to consult with the FLMs 

during development and review of the Phase I Long-Term Strategy (Regulation 3 Part D 

§XIV.F.1.a). 

D. Monitoring Strategy. 

 The monitoring strategy in the SIP is based on the following four goals: 

1. To provide information for new source visibility impact analysis. 

2. To determine existing conditions in Class I areas and the source(s) of any certified 

impairment. 
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3. To determine actual effects from the operation of new major sources or modifications to 

major sources on nearby Class I areas. 

4. To establish visibility trends in Class I areas to evaluate progress towards meeting the 

national visibility goal. 

Potential new major sources must conduct visibility analyses utilizing existing visibility data. 

 If data are adequate and/or representative of the potentially impacted Class I area(s), the 

permitees will be notified of the visibility levels against which impacts are to be assessed. If 

visibility data are not adequate, pre-construction monitoring of visibility may be required. 

If the FLMs or the Division certify existing impairment in a Class I area, the Division will 

determine if the documented visibility impairment can be reasonably attributed to emissions 

from an existing local stationary source. In making this determination, the Division will 

consider all available data, including the following: 

1. Data supplied by the FLM; 

2. The number and type of sources likely to impact visibility in the Class I area; 

3. The existing emissions and control measures on the source(s); 

4. The prevailing meteorology near the Class I area; and 

5. Any modeling that may have been done for other air quality programs. 

If available information is not sufficient to make a decision regarding “reasonable attribution” of 

visibility impairment from an existing source(s), the Division will initiate cooperative studies. 

Such studies could involve the FLMs, the potentially affected source(s), the EPA, and others. 

E. Phase I Long-Term Strategy. 

 The Phase I LTS is that portion of the Visibility SIP that is the State’s long-term strategy for 

making reasonable progress toward remedying existing and preventing future visibility 

impairment within the context of the Phase I program. 

EPA regulations require the State to: (1) develop a long-term strategy; (2) coordinate its LTS 

with existing plans and goals, including those of federal land managers, that may affect 

impairment in any Class I area; (3) demonstrate why the LTS is adequate for making reasonable 

progress toward the national goal and state why the minimum factors (listed in the next 

paragraph) were or were not addressed in developing the LTS; (4) consider the time necessary 

for compliance as well as the economic, energy, and non-air quality environmental impacts of 

compliance, the remaining useful life of any affected existing source, as well as the effect of new 

sources; (5) review its strategy no less frequently than every 5 years and consult with federal 

land managers during this process; and (6) report to EPA and the public on progress achieved 

toward the national visibility goal. 
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During development of the LTS the State must consider, at a minimum, the following six 

factors: 

 Emission reductions due to ongoing air pollution control programs. For example, the 

attainment and maintenance of National Ambient Air Quality Standards in the Denver 

metropolitan area and other non-attainment areas throughout Colorado may reduce visibility 

impairment in a number of Class I areas in the State. If this is the case, the State should 

explain how this would contribute to reasonable progress. 

 Additional emission limitations and schedules for compliance. For example, states may have 

to control other sources causing impairment not covered by BART to make reasonable 

progress toward the national goal. 

 Measures to mitigate the impacts of construction activities. This recognizes that nearby 

construction activities can contribute to impairment in Class I areas. If this appears to be a 

problem in Colorado, then the State should explain in its LTS what measures it will take to 

mitigate these impacts. 

 Source retirement and replacement schedules. The construction of new sources, which will 

ensure the early or scheduled retirement of older, less well-controlled sources, can greatly aid 

progress toward the national visibility goal over the long term. 

 Smoke management techniques for agricultural and forestry management purposes including 

such plans as currently exist within the State for this purpose. The LTS should discuss 

measures that would constitute reasonable progress in relation to this issue. 

 Enforceability of emission limitations and control measures. In some situations the 

enforceability of proposed or actual emission limitations and control measures on sources 

causing existing impairment may be an issue. 

F. Colorado’s LTS History and the Current Review and Revision. 

 Since the time the Colorado Visibility SIP was adopted by the AQCC in 1987, the LTS has 

been amended and/or reviewed on eight occasions: 

• The original 1987 LTS was reviewed and revised in August 1992. 

• After the 1993 certification of impairment at the Mt. Zirkel Wilderness Area, the EPA 

requested an informal LTS status report, which was supplied in December 1993. 

• The 1996-97 LTS was completed in two stages: 

o August 1996 -- focusing entirely on the Mt. Zirkel Wilderness Area 

certification of impairment and the incorporation of emission limitations for 

the Hayden Generating Station; and 
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o April 1997 -- addressing all other issues. 

• The LTS was comprehensively reviewed again in January 1999, but a SIP revision 

was not found to be necessary. 

• Following the Craig Consent Decree in early 2001, the LTS was again amended in 

April 2001 incorporating emission limitations, schedules, and reporting requirements 

for Craig Units 1 and 2. The State, the USFS, and EPA concluded that the 1993 

certification of visibility impairment involving Mt. Zirkel Wilderness Area was 

resolved.2,3

• The February 2002 LTS was comprehensively reviewed and the LTS portion of the 

SIP was updated and reorganized into a more readable format. 

• The November 2004 LTS was also a comprehensive review and minor SIP revision 

update. 

 

Past LTS reviews and SIP revisions are available from the Division. 

This current review is a report on the activities, actions, processes, and progress made with 

respect to the seven review categories within the context of the existing Phase I LTS, adopted by 

the Commission in November 2004. Colorado believes, based on an assessment of the State’s 

achievements with respect to these seven categories, that the current Reasonably Attributable 

Class I visibility program of the State of Colorado achieves reasonable progress toward the 

national visibility goal under Phase I of the visibility protection program. 

In a separate document is a SIP revision to the reasonably attributable part of the LTS. The 

revision is a relatively small series of amendments intended to reflect current conditions and 

plans. 
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II. REVIEW OF COLORADO’S LONG-TERM STRATEGY 

A. STATE AND EPA REQUIREMENTS 

State regulations require the Division to periodically report to the AQCC on the progress 

made toward the national visibility goal via the Phase I SIP. This report to the AQCC and the 

public is being submitted to fulfill these requirements. A SIP revision is contained in a separate 

document. 

EPA regulations require that the State provide this report to the public and the Administrator 

of EPA. Both EPA and State regulations require the report to include an assessment of: 

1. The progress achieved in remedying existing impairment of visibility in any Class I area. 

2. The ability of the long-term strategy to prevent future impairment of visibility in any 

Class I area. 

3. Any change in visibility since the last such report, or in the case of the first report, since 

plan approval, including an assessment of existing conditions. 

4. Additional measures, including the need for SIP revisions that may be necessary to 

ensure reasonable progress toward the national visibility goal. 

5. The progress achieved in implementing BART and meeting other schedules set forth in 

the long-term strategy. 

6. The impact of any exemption from BART granted to any facility. 

7. The need for BART to remedy existing impairment in an integral vista declared since 

plan approval. 

B. STEP-BY-STEP REVIEW 

Each element of the review is presented in detail below. 

1. PROGRESS IN REMEDYING EXISTING IMPAIRMENT OF VISIBILITY IN ANY 

CLASS I AREA. 

The Phase I Class I Visibility SIP is focused on source-specific or plume-type impairment 

from single or small groups of stationary sources, consistent with Phase I of the implementation 

of EPA’s visibility program. 

a. Visibility Impacts in the Mt. Zirkel Wilderness. 

 In July 1993, the USFS certified visibility impairment in the Mt. Zirkel Wilderness Area and 

named the Hayden and Craig power stations as suspected sources.1

 As noted, upon certification 

by a federal land manager of visibility impairment in a Class I area, the Division must determine 

if it can “reasonably attribute” the visibility impairment to one or more existing stationary 
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sources. If so, the Division must conduct a BART analysis and as a result may order emission 

limitations for each pollutant at the facilities. 

 The Division considered existing information available at the time of the USFS certification 

of impairment to determine if it could make a decision to reasonably attribute visibility 

impairment within the MZWA to the Hayden and/or Craig generating stations. The Division 

concluded that existing information was insufficient to reasonably attribute. The Division’s 

response was to collaboratively develop with other stakeholders the $3.5 million Mt. Zirkel 

Visibility Study (MZVS) in order to collect additional information. The MZVS was concluded 

in July 1996.4 

 For a complete review of the activities, studies, and events that have occurred in relation to 

this environmental matter, see the April 1997 and January 1999 LTS reviews (available from the 

Division). Below is a summary of the how the certification of impairment has been resolved. 

(i). Hayden Station. 

 The certification of impairment made by the USFS regarding the Hayden Station was 

resolved through a settlement process that began in late 1995. On May 21, 1996, the Sierra 

Club, State of Colorado, owners of Hayden Station, and Environmental Protection 

Agency/Department of Justice executed an agreement -- the Hayden Consent Decree.5

 On May 

22, 1996, the Decree was filed in federal district court. The court approved it on August 19, 

1996. The Decree was intended to resolve a number of issues, including a successful Sierra Club 

lawsuit against the Hayden Station, the needs of the State’s visibility regulatory program in 

relation to Hayden, and an EPA complaint against the facility. In addition, the Decree was 

intended to make progress toward reducing acid deposition in the Mt. Zirkel Wilderness. 

Emission limitations, construction schedules, and reporting requirements taken from the 

Hayden Consent Decree were incorporated into the Visibility SIP by the AQCC on August 15, 

1996. The State believes that these significant emission reductions effectively eliminate the 

sulfate and primary plume related visibility impairment in the MZWA that could be associated 

with the Hayden Station. The State further believes that the Hayden Consent Decree effectively 

resolves the certification of impairment brought by the USFS against the Hayden Station. The 

Forest Service has concluded that its complaint against Hayden has been satisfied. EPA 

approved this SIP amendment on January 16, 1997.6

The construction of Hayden’s control equipment progressed ahead of schedule. All 

compliance dates in the SIP and Consent Decree were met and the emission limitations for NOx, 

SO2, opacity, and particulate matter have been consistently achieved in actual operation. The 

relevant emission limitations and monitoring requirements have been moved into the facility’s 

Title V operating permit and the permit has been issued and the Consent Decree has been 

terminated. 

(ii). Craig Generating Station (Yampa Project). 

The certification of impairment made by the USFS regarding the Craig Station Units 1 and 2 

was also resolved through a settlement process that began in Fall 1999. After Hayden was 
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resolved in August 1996, attention turned to Craig Station Units 1 and 2. The Mt. Zirkel 

Visibility Study (MZVS) indicated to the Division that sulfate haze from Yampa Valley power 

plants occasionally entered the MZWA and along with regional haze contributed to visibility 

impairment. Thus, the focus to resolving the Craig Station portion of the certification was on 

reducing SO2, the precursor pollutant of sulfate, from Craig Station Units 1 and 2. The State 

preferred to resolve the visibility certification through negotiated settlement. If settlement 

seemed unlikely, the State was prepared to resolve the certification using the available regulatory 

tools. At a meeting in late 1996 between the State, Craig Owners, and EPA, the State agreed to 

temporarily delay pursuing regulatory action in order to foster the collaboration needed to jointly 

develop additional information on various SO2 emission reduction options and associated cost. 

Craig Station Units 1 and 2 at the time achieved 65% SO2 control; both EPA and the State 

believed that an improvement in the degree of control would resolve the certification. A joint 

study, known as the Craig Station Flue Gas Desulfurization Study (Craig FGD Study), became 

the focus for a negotiated settlement. The information could also be used as part of a BART 

determination if needed. The study was completed in August 1999.7

There were other issues involved and parties concerned with emissions from Craig Station 

Units 1 and 2. The USFS has strong concerns about local emissions of SO2 and NOx that may be 

associated with acid deposition and aquatic and terrestrial ecosystem effects in the MZWA. A 

1996 Colorado statute provides FLMs with an opportunity to assert impairment to Class I areas 

by air pollution adversely affecting non-visibility related qualities of the area, such as the aquatic 

ecosystem.8 The USFS did not trigger the law with an assertion related to MZWA and was 

awaiting the outcome of the resolution of the visibility certification and/or global settlement of 

all issues. In addition, the Sierra Club initiated a citizen lawsuit under the Clean Air Act in late 

1996 directed against Craig Station Units 1 and 2 regarding opacity issues. 

In Fall 1999, the Sierra Club, Craig Owners, EPA, the State, and the USFS began global 

settlement talks with an independent mediator. On September 22, 1999, EPA issued a SIP call to 

Colorado indicating the State had twelve months to resolve the certification regarding Craig 

Station Units 1 and 2.9

 The Craig Owners and Sierra Club concluded a Consent Decree and 

filed it with the federal district court on January 10, 2001. The court approved the agreement on 

March 19, 2001. The State resolved the certification of impairment for Units 1 and 2 of Craig 

Station by adopting emission limitations, schedules, and reporting requirements from the Craig 

Consent Decree into the Visibility SIP. The USFS concluded that, “the proposed reductions of 

both sulfur dioxide and nitrogen oxides will resolve all Forest Service issues relative to the Craig 

Stations and our 1993 Certification of Impairment.”10 The SIP was amended by the AQCC on 

April 19, 20012 and EPA published final approval of the SIP amendment after a public comment 

period.3 Work was completed on Unit 1 during 2003 and on Unit 2 in 2004. All compliance 

dates in the SIP and Consent Decree were met and the emission limitations for NOx, SO2, 

opacity, and particulate matter have been consistently achieved in actual operation. The relevant 

emission limitations and monitoring requirements have been moved into the facility’s Title V 

operating permit. The permit has been issued and the Consent Decree terminated.

(iii). Other Stationary Sources and the MZWA. 

The Division has found no evidence that other stationary sources potentially subject to 
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BART may reasonably be attributed to cause or contribute to visibility impairment at MZWA 

under Phase I of the EPA visibility program. The USFS certification of visibility impairment, 

related to the Phase I program, has been completely resolved. Regional haze that impacts any 

Colorado Class I areas, including MZWA, are addressed in the regional haze SIP. 

(iv). Monitoring and the MZWA. 

It is important to track the effect of the emission reductions at Hayden and Craig generating 

stations on visibility impairment near the Wilderness as well as on acid levels in sensitive lakes 

and the snowpack. Funding for and the collection of these data are provided variously by the 

USFS, U.S. Geological Survey, EPA, and the Division. Table 1 below provides a brief overview 

of monitoring activities in and around MZWA. 

Table 1 

Long-Term Visibility and Non-Visibility Air Quality Related Value Measurements 

In and Near the Mt. Zirkel Wilderness Area 

Instrument, 

Measurement, 

or Sampler 

1. Sponsor 

2. Funding 

3. History 

Purpose 

Continuous SO2

monitor at Buffalo 

Pass Tower* 

1. Colorado Air Pollution 

Control Division 

2. $9,800/year by CAPCD 

3. 9/97 through present. 

Measures frequency and magnitude of SO2 “hits” at Buffalo 

Pass as an indicator of the presence of Craig and Hayden 

emissions and potential impacts at the Mt. Zirkel Wilderness 

Area. The monitor provides hourly average SO2. The 

purpose of the monitor is to determine whether trends are 

occurring as emissions change at Hayden and Craig 20 and 40 

miles away, respectively, in the Yampa Valley. 

Continuous 

ambient 

nephelometer at 

Buffalo Pass 

Tower* 

1. US Forest Service 

2. $9,600/year by USFS 

3. 1994 through present. 

Measures frequency and magnitude of visibility episodes (the 

nephelometer measures light scattering, a component of 

visibility) at Buffalo Pass. This measurement provides hourly 

average light scattering but is subject to significant weather 

interferences. 

Automatic camera 

system 

1. US Forest Service 

2. $5,280/year by USFS 

3. 10/90 through present 

Three 35mm slides are taken each day and archived. The 

visual information can be used to document various types of 

visibility conditions and matched/collated with instrumental 

measurements. 

IMPROVE 

aerosol monitor at 

Buffalo Pass 

Tower* 

1. Initially USFS, now 

EPA, as part of the national 

IMPROVE visibility 

monitoring network. 

2. $14,000/year by EPA 

(for supplies and analysis) 

 $33,000/year by USFS 

(for support of all Buffalo 

Pass Tower monitoring 

operations) 

Measurements include 1-in-3 day sampling, 24-hour filter 

based PM2.5 (chemically speciated) and PM10 (mass only). 

Light extinction reconstruction is calculated from the various 

aerosol constituents. Measurement of overall reconstructed 

light extinction is used for episode identification as well as 

trends. These reconstructed extinction data will be compared 

between the before and after periods. While this measure is 

not as prone to weather interferences as the nephelometer, 

other challenges in analyzing these data include changes in 

regional emissions, climatic variation, wildfire, and the nature 
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Instrument, 

Measurement, 

or Sampler 

1. Sponsor 

2. Funding 

3. History 

Purpose 

3. 1994 through present of trying to distinguish episodic change in a 24-hour average. 

National Acid 

Deposition 

Program (NADP) 

sampler at Buffalo 

Pass Tower*. 

1. USFS 

2. $12,288/year by USFS 

3. 1984 through present 

Measurement of acid precipitation-related chemical 

constituents. The network collects data on the chemistry of 

precipitation for monitoring of geographical and temporal 

long-term trends. The precipitation at each station is collected 

weekly. It is then sent to the Central Analytical Laboratory 

where it is analyzed for hydrogen (acidity as pH), sulfate, 

nitrate, ammonium, chloride, and base cations (such as 

calcium, magnesium, potassium and sodium). 

Mercury 

deposition 

sampler at Buffalo 

Pass Tower* 

1. USFS 

2. $12,000/year by USFS 

3. 1997 through present 

Mercury deposition sampling is done through the NADP 

program. This site is sponsored and funded by USFS. The 

purpose is to measure mercury deposition. The sample is 

collected weekly and sent to the NADP’s Central Analytical 

Laboratory. 

Snowpack 

chemistry 

sampling in 

March or April of 

each year prior to 

spring snowmelt. 

1. USGS, NPS, USFS 

2. $115,000/year 

3. 1990 through present 

Annual measurement of snowpack chemistry prior to spring 

snowmelt and the release of acids during the “spring acid 

pulse.” The U.S. Geological Survey has been monitoring 

snowpack chemistry at more than 50 locations throughout the 

Rocky Mountain region, extending from northern New 

Mexico to northern Montana, annually since 1993. There are 

20 sites in Colorado, including several in and near the Mt. 

Zirkel Wilderness. Some sites in Colorado have been 

monitored since 1990. The purpose of the monitoring is to: 1) 

have an integrated measurement of acid deposition and snow 

chemistry over the snow accumulation months in high altitude 

areas associated with sensitive high altitude aquatic 

ecosystems; 2) determine whether trends are occurring in the 

snowpack chemistry; and 3) provide indicators of regional 

and/or local source emission changes. 

Lake sampling in 

Mt. Zirkel 

Wilderness (and 2 

other wilderness 

areas) during 

summer and fall. 

1. USFS/CDPHE/ USGS 

2. $62,000 

3. 1983 through present 

Measurements of acid precipitation-related chemical 

constituents as well as overall measures such as hydrogen ion, 

pH, and buffering capacity of 3 lakes in the Mt. Zirkel 

Wilderness. The purpose of the long-term monitoring of these 

lakes is to: 1) determine the natural variance in chemistry of 

the lakes; 2) determine whether trends are occurring in the 

chemistry of lakes in the Mt. Zirkel Wilderness, and 3) 

provide information on the ambient chemistry of lakes in the 

Wilderness. 

*Buffalo Pass monitoring tower is at the southern end of the Mt. Zirkel Wilderness. 

The measurements provide a reasonably comprehensive network to track the emission changes 

through different parts of key environmental systems, including atmospheric emissions, 
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visibility, precipitation, acid deposition, mercury deposition, snowpack and aquatic ecosystems. 

(v). Analysis of the Effects of the Hayden Generating Station Emission Reductions. 

 Using the data collected from the network described above, the Division and the USGS 

completed an analysis during 2004-2005 of the effects of the emission reductions at the Hayden 

Generating Station. At that time, Craig had just completed its emission capture upgrade and 

there were insufficient data to analyze to assess the additional effects of the Craig project. 

Therefore, the analysis focused on the reductions at the Hayden Generating Station. A final 

report will be completed during 2009 on the effects of the reductions at Craig as well as an 

assessment of the combined effect of the decreases in emissions from both facilities. 

Study Design. Environmental data were compared between a period “before” Hayden was 

controlled versus a period “after” Hayden was controlled.

The period before controls were installed at Hayden is defined as 1995 through 9/24/98. 

1995 is chosen as the beginning of the before period even though data extends earlier for a 

number of data sets. The before period is purposely constrained to limit the influence of regional 

emission changes over time as well as climate variation. 

Unit 1’s boiler was brought down on 9/25/98 to begin the tieing-in and integration of its 

various air pollution control systems. Unit 1 was re-started with emission controls on December 

21, 1998. Unit 2’s boiler was brought down on 3/7/99. It was re-started on May 20, 1999. 

However, intermittent problems with the SO2 controls could not be fixed until November 16, 

1999. The Craig Generating Station (Yampa Project) began its upgrades on September 13, 2003. 

 The three periods (i.e., before, during, after) are summarized in Table 2 below. Only the before 

and after periods were analyzed and compared. 

Table 2 

The Before, During and After Periods

Period Dates What 

Before 1995 through 9/24/98 This is the period before 

Hayden’s pollution 

controls began operating 

During 

(not analyzed) 

9/25/98 through 11/16/99 Pollution control 

equipment was being tiedin, integrated and debugged. 

After 11/17/99 through 9/12/03 Hayden’s equipment in 

routine operation and 

Craig had not yet begun its 

tie-in period. 

Confounding Factors. Because the collection of environmental data occurs in the real world, 

rather than in a laboratory where other changes can be held constant, there are several influences 
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the data analysts were aware might confound or mask the signal of Hayden’s emission change. 

All of the factors below contribute to make it more difficult to find and attribute the changes due 

solely to Hayden. 

o Climate 

 The before period was wetter than average and the after period was drier 

than average. There was a 30-40% decrease in precipitation between the 

two periods depending on measurement location. 

o Regional Haze 

 The after period was 17% more hazy. This is largely due to the decrease 

in precipitation and associated drought. Chemical analyses showed that 

almost all of the change between the two periods was due to particles from 

wildfires and increased dust. 

o Overall Yampa Valley Emissions 

 Hayden and Craig are in the same valley, therefore, emissions from both 

must be considered together since analysis techniques can’t identify the 

pollutants from one plant versus the other. Given Hayden’s specific 

reduction and the ongoing operation at Craig (before its upgrade), SO2

decreased in the Yampa Valley by 48% and NOx increased 7%. 

o Regional Emission Changes 

 Not only was there an emission change at Hayden, but large emission 

reductions of SO2 also occurred in the southwestern part of the U.S. For 

example: Arizona/39%, New Mexico/27%, Wyoming/18%, Texas/15%. 

o Atmospheric Chemistry 

 The atmospheric chemistry converting invisible SO2 gas to visible sulfate 

particles is not linear. That is, a one unit decrease in SO2 may not lead to 

a one unit decrease in sulfate. 

Results.

• Emissions 

o Sulfur dioxide (SO2) removal at Hayden has always been at least 85% over 30 

and 90 day rolling averages since the compliance period began. Nitrogen 

oxides (NOx) have decreased approximately 50% annually. The new 

particulate control system has completely eliminated the occasional black 

smoke-plume episodes that previously occurred. 

• Ambient SO2 as measured at Mt. Zirkel Wilderness Area 

o Decreased 40% due to the reductions at Hayden. 

• Haze at Mt. Zirkel Wilderness Area 

o Increased 17% due to the drought and increases in regional haze. This would 

have been worse without the reductions at Hayden. 

• Sulfate Particulate Haze 

o Overall decrease of 20% at Mt. Zirkel Wilderness Area. 

o Peak sulfate episodes were eliminated in the after data. This is a very 

important finding because it is the worst days that hamper enjoyment of clear 

visibility. 

o It is estimated that approximately half of the overall decrease is due to 
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Hayden’s reductions. The other half is due to the regional scale reductions in 

SO2. 

• Acid Deposition Measurements 

o Decrease in sulfuric acid deposition of approximately 20%. 

 Looking at other measurement sites, this decrease in sulfuric acid only

occurred at acid deposition sites downwind of Hayden. 

o Overall decrease in acid deposition at all sites, however, most of this is 

drought related due to an increase in dust elements in the rain and snow that 

buffer acids. 

• Snowpits 

o Small decrease in sulfuric acid at pits downwind from Hayden. 

o Overall decrease in acidity, again due to more dust elements in the snowpack. 

• Lakes 

o No change due to emission reductions in before versus after periods. This is 

expected because response time to an emission reduction of SO2 in a 

watershed is several years. Effects of drought were also visible in lake acidity 

(i.e., less acid due to increased dust elements). 

 In spite of the big challenges nature and other anthropogenic changes piled onto the study 

design, the USGS and the APCD see a strong signal decrease in episodic visibility impairing 

sulfate and acidic wet sulfate in and near the Mt. Zirkel Wilderness Area from the emission 

reductions at Hayden Generating Station. 

b. Regional haze. 

EPA published its final regional haze rule in July 1999.11 This review of the Phase I SIP is 

not related formally to the regional haze program. Nevertheless, such haze exists at all Colorado 

Class I areas and is the subject of the larger regional haze SIP document within which this LTS 

review is embedded and coordinated. 

c. Ongoing Air Pollution Control Programs. 

 Since the November 2004 LTS review/report several activities in ongoing air pollution 

control programs have occurred that are relevant to this review. 

(i). Rocky Mountain National Park Initiative. 

The National Park Service (NPS), other federal agencies, and academic researchers have 

actively pursued ecosystem and air quality monitoring and data collection programs in and near 

the Park for over twenty years. Through these efforts significant amounts of data have been 

collected. Findings from these data published in over 80 peer reviewed research articles 

document ecosystem changes from nitrogen (N) deposition on the east side of the Continental 

Divide including changes in the type and abundance of aquatic plant species, elevated levels of 

nitrate in surface waters, elevated levels of N in spruce tree chemistry, long-term accumulation 

of N in forest soils, and a shift in alpine tundra plant communities favoring sedges and grasses 

over the natural wildflower flora. 
15

Two-thirds of the Park is near or above treeline with shallow soils and granitic bedrock that 

are indicative of a fragile ecosystem environment. This environment is highly susceptible to 

changes induced by chemical contributions to soils and waters through atmospheric deposition. 

The Park’s enabling legislation and other key Congressional statutes mandate that natural 

resources at RMNP are to remain unimpaired for future generations. Thus, the Rocky Mountain 

National Park Initiative was created to study and promote action to remedy air quality issues 

facing the Park, primarily the adverse ecosystem impacts from increasing nitrogen deposition. 

Other air quality issues are being addressed by other means: visibility impairment by the regional 

haze program development and ozone by the Early Action Compact and SIP development 

process. 

Using a collaborative approach, the participating agencies -- the Colorado Department of 

Public Health and Environment (CDPHE), the U.S. Environmental Protection Agency Region 8 

(EPA), and the NPS -- have worked effectively to develop a Nitrogen Deposition Reduction Plan 

(Plan or NDRP). A public participation process facilitated by a Colorado Air Quality Control 

Commission (AQCC) Subcommittee has helped to involve the public, and a memorandum of 

understanding (MOU) has been used by the involved agencies to guide the Initiative’s progress 

leading to development of the Plan. 

The agencies have initially focused their efforts in developing the Plan on voluntary 

approaches first, together with programs that are pending or under way, in lieu of developing a 

new regulatory program to achieve nitrogen deposition reductions. The agencies believe this 

strategy has the potential to provide benefits in the near term to reducing nitrogen deposition. 

However, the agencies support a process to require regulatory measures specific to reducing 

nitrogen deposition if voluntary and anticipated reductions prove insufficient in making planned 

progress goals under this Plan. Development and implementation of a contingency plan is one 

mechanism supported by the agencies to ensure reduction of adverse ecosystem impacts in 

RMNP. 

The NDRP works to: (1) consider all available emission reduction options and programs for 

nitrogen-related emissions (primarily nitrogen oxides (NOx) and ammonia (NH3)); (2) provide a 

technical assessment of the state-of-knowledge of deposition components and trends, the 

emission sources, source areas, and atmospheric transport; (3) determine implementation 

measures for making progress and mechanisms to evaluate effectiveness of, and incorporation of 

new, control measures; (4) make recommendations for future needs as necessary to assure 

continued progress and achievement of Park goals; and (5) incorporate adaptive management 

principals for the consideration and use of new data and analyses as they become available. 

The Plan includes a critical load determination for nitrogen affecting the high alpine 

ecosystems in the Park that was established prior to the development of this Plan. The critical 

load for wet nitrogen deposition, set at 1.5 kg/ha/yr, is a threshold value above which significant 

harmful effects to sensitive ecosystem components occur. The critical load for wet nitrogen 

deposition east of the Continental Divide in RMNP represents an estimation of the concentration 

at which excess nitrogen deposition began causing harmful impacts on RMNP ecosystems. The 

Plan relies on a “glidepath” management approach to achieve the critical load goal in the Park by 
16

the year 2032 with interim milestones to be measured at five-year intervals. The first milestone, 

set for 2012, works to achieve a reduction that is consistent with an average rate of deposition 

reduction that will achieve the critical load by the year 2032 and reflects the potential benefit 

from planned state and federal emission reduction programs. 

The NDRP was approved by the AQCC in April 2007. Implementation of the Plan will 

likely benefit visibility at RMNP to an unknown degree. The Division maintains a website that 

is a clearinghouse for information related to the Initiative. The full NDRP and other technical 

documents may be found at 

http://www.cdphe.state.co.us/ap/rmnp.html

(ii). The Four Corners Task Force. 

After many years of concern about emissions growth in the Four Corners area and impacts on 

nearby Class I areas, the States of New Mexico and Colorado have convened an Air Quality 

Task Force to work on the air quality issues and challenges facing the Four Corners region. The 

Four Corners region is rich in coal and oil & gas reserves. Oil & gas production and coal-fired 

power plants result in large emissions of air pollution that may be degrading air quality. Specific 

concerns include National Ambient Air Quality Standards (NAAQS) and Prevention of 

Significant Deterioration (PSD) increment compliance, degradation of visibility, and increased 

deposition. 

The U.S. Department of Interior - Bureau of Land Management (BLM) and the U.S. 

Department of Agriculture - Forest Service (USFS) are currently responding to industry 

proposals for expanded development of oil and gas production in the region. There are two 

proposed coal-fired power plants: a 1,500 megawatt plant proposed on Navajo Nation lands and 

a 300 megawatt plant proposed north of Grants, New Mexico. Additionally, the population in the 

Four Corners region likely will continue to grow in coming years, resulting in even more air 

pollution and, specifically, more nitrogen oxide emissions. 

In response to these challenges, the affected states, tribes and federal land managers in the 

region have come together to begin to plan for control strategies for future air quality impacts 

from development. The concept of a Task Force emerged that would allow for a broad and 

inclusive collaborative process to regional air quality planning. 

The Task Force work groups are: 

• Oil and Gas, 

• Power Plants, 

• Other Sources, 

• Cumulative Effects, and 

• Monitoring. 

These workgroups are studying issues and creating lists of options to the Task Force about how 

to proceed. An executive/steering committee that includes representatives from the states of 
17

Colorado, New Mexico, and Utah, the U.S. Environmental Protection Agency, the U.S. 

Department of Agriculture - Forest Service, and the U.S. Department of the Interior - National 

Park Service and the Bureau of Land Management has been formed to help guide the Task 

Force's progress. Timelines for workgroup deliverables are being developed to ensure that all 

options developed are timely. The task force will work over a two-year period and deliver a 

final report by December 2007. 

The Task Force’s website is 

http://www.nmenv.state.nm.us/aqb/4C/index.html

(iii). New Oil and Gas Controls. 

On December 17, 2006, the Colorado Air Quality Control Commission (AQCC) adopted 

changes to oil & gas industry regulations to reduce emissions of volatile organic compounds 

(VOCs) from condensate tanks. VOCs are a precursor to ozone formation and secondary organic 

carbon particulate – a component of visibility degradation. 

New control requirements were established for condensate tanks in both the Front Range 

Early Action Compact Area and statewide. New reporting and recordkeeping requirements were 

also established. The new requirements are summarized below: 

Control Requirements: Front Range Ozone Early Action Compact (EAC) Area 

• Commencing May 1, 2007, companies in the EAC region must increase the control of 

VOCs from current 47.5 percent level to 75 percent for the summertime ozone season. 

• In addition, there are new reporting and recordkeeping requirements. 

Control Requirements: Statewide 

• Tanks standards: New and existing condensate tanks emitting 20 tons per year or more of 

VOCs required to control emissions by 95 percent commencing May 1, 2008. 

• Glycol Dehydrator controls: New and existing glycol dehydrators emitting more than 15 

tons per year of VOCs are required to control emissions by 90 percent commencing May 

1, 2008. 

• Table 3 contains engine standards for new or relocated engines from out-of-state 

commencing July 1, 2007. 

Table 3 

Engine Standards

Maximum 

engine 

horsepower 

Construction or 

relocation date 

NOx 

g/hp-hr 

CO 

g/hp-hr 

NMHC 

g/hp-hr 

100 - 500 hp January 1, 2008 

January 1, 2011 

2.0 

1.0 

4.0 

2.0 

1.0 

0.7 

Greater than 

500 hp 

July 1, 2007 

July 1, 2010 

2.0 

1.0 

4.0 

2.0 

1.0 

0.7 
18

Additional information about the new emission controls can be found at 

http://www.cdphe.state.co.us/ap/oilgas.html

(iv). Review of Ongoing Programs and Status of Redesignations. 

 The most comprehensive review of existing and ongoing programs as well as monitoring data 

and trends is contained in the Colorado Air Quality Control Commission’s 2006-2007 Report to 

the Public. This report in its entirety is included as Attachment 1. 

 As recently as 1995 Colorado had 12 “non-attainment” areas within the State for carbon 

monoxide, ozone, and/or PM10 health standards. Generally, all of these areas now maintain 

good air quality. This progress reflects the effects of local, statewide, regional, and national 

emission control strategies. This clean-up of Colorado’s non-attainment areas has also benefited 

Class I visibility conditions to some unknown degree. 

 In the summer of 2003, the Denver metropolitan area violated the 8-hour ozone standard. 

EPA has designated all or parts of 9 counties in northeastern Colorado as nonattainment for the 

8-hour ozone, though the nonattainment designation has been deferred with the adoption of the 

Ozone Action Plan by the Colorado Air Quality Control Commission in March 2004 under 

EPA's Early Action Compact provisions. High concentrations of ground-level ozone on Friday, 

July 20, 2007 appear to have put the nine-county Denver region in violation of the federal 

health-based, eight-hour standard for ozone. If monitoring results are verified, the region will 

likely be designated as "nonattainment" for ozone by the U.S. Environmental Protection Agency. 

A detailed plan to reduce ozone will be developed for submission to the EPA in 2008 by the 

Colorado Air Pollution Control Division, along with the Regional Air Quality Council and the 

North Front Range Metropolitan Planning Organization. This new plan, a federally -required 

State Implementation Plan for ozone, will require further reductions in ozone levels beyond what 

was required through an earlier Ozone Early Action Compact. 

The table below shows the designation status for Colorado non-attainment areas. 

Table 4 

REDESIGNATION and PLAN AMENDMENT STATUS REPORT – 4/2/07 

Redesignations Plan Amendments

PM10 

Aspen AQCC approved 1/11/01; EPA 

approved 5/15/03, effective 7/14/03 

None 

Canon City AQCC approved 10/17/96; EPA 

approved 5/30/00, effective 7/31/00 

None 

Denver AQCC approved 4/19/01; EPA 

approved 9/16/02, effective 10/16/02 

Plan amendment developed with MOBILE6 

to remove I/M from SIP; AQCC approved 

12/15/05; Governor submitted to EPA 

9/25/06 

AQCC approved 11/15/01; EPA None 
19

Redesignations Plan Amendments

Lamar approved 10/25/05, effective 11/25/05 

Pagosa 

Springs 

AQCC approved 3/16/00; EPA 

approved 6/15/01, effective 8/14/01 

None 

Steamboat 

Springs 

AQCC approved 11/15/01; EPA 

approved 10/25/04, effective 11/24/04 

None 

Telluride AQCC approved 3/16/00; EPA 

approved 6/15/01, effective 8/14/01 

None 

Carbon 

Monoxide

Colorado 

Springs 

AQCC approved 1/15/98; EPA 

approved 8/25/99, effective 9/24/99 

- Amendment to drop oxyfuels approved by 

AQCC 2/17/00; EPA approved 12/22/00, 

effective 2/20/01 

- Amendment using MOBILE6 to eliminate 

I/M from SIP and revise emission budget 

approved by AQCC 12/18/03; EPA 

approved 9/07/04, effective 11/08/04 

Denver AQCC approved 1/10/00; EPA 

approved 12/14/01, effective 1/14/02 

- Amendment using MOBILE6 to revise 

emission budgets approved by AQCC 

6/19/03; EPA approved 9/16/04, effective 

11/15/04 

- Amendment developed with MOBILE6 to 

remove I/M & oxyfuels from SIP; AQCC 

approved 12/15/05; Governor submitted to 

EPA 9/25/06 

Ft. Collins AQCC approved 7/18/02; EPA 

approved 7/22/03, effective 9/22/03 

Greeley AQCC approved 9/19/96; EPA 

approved 3/10/99, effective 5/10/99 

- Amendment using MOBILE6 to revise 

emission budget & to eliminate oxyfuels 

from the regulation/SIP & I/M from the SIP 

approved by AQCC 12/19/02; EPA 

approved 8/19/05, effective 9/19/05 

Longmont AQCC approved 12/19/97; EPA 

approved 9/24/99, effective 11/23/99 

- Amendment using MOBILE6 to revise 

emission budget approved by AQCC 

12/18/03; EPA approved 9/30/04, effective 

11/29/04 

- Amendment developed with MOBILE6 to 

remove I/M & oxyfuels from SIP; AQCC 

approved 12/15/05; Governor submitted to 

EPA 9/25/06 

Ozone 

AQCC approved 1-hour redesignation - 8-hour OAP updated to include periodic 
20

Redesignations Plan Amendments

Denver 

/Northern 

Front Range 

request and maintenance plan 1/11/01; 

EPA approved 9/11/01, effective 

10/11/01 

Early Action Compact 8-hour Ozone 

Action Plan approved by AQCC 

3/12/04; EPA approved 8/19/05, 

effective 9/19/05 

assessments; AQCC approved 12/15/05; 

Governor submitted to EPA 10/06 

- 8-hour OAP updated 12/17/06 by AQCC to 

incorporate Reg 7 oil and gas condensate 

tank and engine requirements. Governor’s 

submittal anticipated 

-Additional exceedances in 2007. SIP 

preparation in 2008. 

Lead 

Denver EPA redesignated Denver attainment in 

1984 

Nitrogen 

Dioxide 

Denver EPA redesignated Denver attainment in 

1984 

 

2. THE ABILITY OF THE LONG-TERM STRATEGY TO PREVENT FUTURE 

IMPAIRMENT OF VISIBILITY IN ANY CLASS I AREA. 

Generally, the State of Colorado considers its New Source Review and Prevention of 

Significant Deterioration (PSD) programs as meeting the long-term strategy requirements for 

preventing future impairment from proposed major stationary sources or major modifications to 

existing facilities. In addition, there are specific activities the Division has undertaken. 

a. Modeling Guidance. 

 The Division has published modeling guidance that presents methods for estimating impacts 

from stationary sources of air pollution. The guidance is intended to help permit applicants, air 

quality specialists, and others understand the Division’s expectations for the ambient air impact 

analysis and to prevent unnecessary delays in the permit process. It provides a starting point for 

modeling, but allows the use of professional judgment. The guidance contains sections on 

visibility modeling. In 2001, a technical peer review of the guidance was completed. A more 

general public review process was finished toward the end of that year. The finalized and 

updated (as of December 27, 2005) guidance document is available via the Air Pollution Control 

Division’s web site at: http://apcd.state.co.us/permits/cmg.html

b. Smoke Management. 

Colorado believes its smoke management program is protective of public health and welfare 

as well as Class I visibility. In 2005, the Division certified its smoke management program as 

consistent with EPA’s Interim Air Quality Policy on Wildland Prescribed Fire, May 1998. The 

program is described below. 

(i). Regulation No. 9. 
21

 Regulation No. 9 (Open Burning, Prescribed Fire, and Permitting) is the main vehicle in 

Colorado for addressing smoke management and preventing unacceptable smoke impacts. In 

addition to its permitting requirements, it implements Colorado Senate Bill 01-214 (“Concerning 

the Application of State Air Quality Standards to the Use of Prescribed Fire for Management 

Activities Within the State and Making an Appropriation Therefor”) that became law in 2001. 

The regulation also incorporates permitting and reporting requirements for all users of prescribed 

fire similar to those in the State’s past Smoke Management Memorandum of Understanding 

(MOU). The AQCC adopted the regulation on January 17, 2002. 

Regulation No. 9 is in eight sections: 

I. Scope 

II. Definitions 

III. Open Burning Permit Requirement 

IV. General Open Burning Permits 

V. Planned Ignition Fire Permits 

VI. Unplanned Ignition Fire Permits 

VII. Additional Requirements for Significant Users of Prescribed Fire 

VIII. Fees 

The rule applies to all open burning activity within Colorado, with certain exceptions. Section 

III specifically exempts agricultural open burning from the permit requirement. 

 After the scope and definitions sections, the rule has several sections regarding permitting 

and other requirements applicable to open burning of various types. Section IV contains 

requirements for a general open burning permit and associated permit conditions. Sections V 

and VI contain the permitting, information, modeling and reporting requirements, as well as a 

smoke risk categorization, and permit conditions for planned ignition prescribed fires to insure 

that prescribed fires neither violate National Ambient Air Quality Standards nor have 

unacceptable visibility impacts. These provisions are similar to the past voluntary agreements 

among signatories of the expired Colorado Smoke Management MOU for prescribed fire. The 

regulation, however, applies to all users of prescribed fire above a de minimus level project. The 

rule also specifies requirements regarding suppression of prescribed fire if monitoring and/or air 

pollution levels indicate that permit conditions, the burn prescription, and/or air quality standards 

have been or will be exceeded. The Division’s draft permits for large burns with a high smokerisk are subject to a 30-day public comment period and the opportunity for a public comment 

hearing before the Commission. The Division will disclose potential visibility impacts of these 

proposed fires and must consider comments when determining whether to grant, conditionally 

grant, or deny the final permit. 

 Sections VII and VIII are the elements of the regulation that implement SB01-214. Section 

VII addresses how significant users of prescribed fire (i.e., those that own or manage 10,000 

acres and generate at least 10 tons of PM10 annually from use of prescribed fire) must submit 

planning documents to the Commission. The regulation identifies the contents of the planning 

documents. The rule further requires that all such prescribed fire activities of significant users 
22

shall conform to the State standard to “minimize emissions using all available, practicable 

methods that are technologically feasible and economically reasonable.” SB 01-214 directs the 

Commission to hold a public hearing regarding each planning document and to develop any 

necessary comments and recommendations to bring the plans into consistency with the State 

goal. After July 1, 2002 the Division cannot issue open burning permits to significant users for 

lands whose planning documents and fuel management decision-making are inconsistent with 

Commission recommendations and comments. The Commission has had hearings on the 

planning documents of the U.S.D.A. Forest Service, U.S.D.I. Bureau of Land Management, 

Colorado Division of Wildlife, U.S.D.I. National Park Service, U.S.D.O.D. Fort Carson, U.S.D.I. 

Fish and Wildlife Service, U.S.D.O.D. Air Force Academy, Jefferson County, Banded Peak Area 

Ranches, Colorado State Parks, Colorado State Land Board, the Forbes/Trinchera Ranch, and the 

Denver Water Board. 

 Fees are discussed in section VIII. No fees are charged for general permits (local authorities 

may charge fees under their own authority). Significant users of prescribed fire pay fees of 

$59.98/hour to the Division for review of planning documents. Prescribed fire permitees pay for 

the cost of the prescribed fire program based on a cost distribution methodology. The Division’s 

Fiscal Officer calculated the cost of the program at the outset of the program beginning in 

calendar year 2002. The Statement of Basis, Specific Statutory Authority and Purpose of the 

regulation also specifies the Commission’s intent that the Division annually calculate the cost to 

administer the program and report to the Commission each August on program costs, 

projections, and revenues. If the cumulative cost varies more than 5% from the total fee amount 

in regulation, the Division will seek a fee change before the Commission in a properly noticed 

public hearing. In addition, the Statement indicates that any deficits not be funded by stationary 

source fees. The current cost of the program as stated in Regulation No. 9 is $174,585.08. 

 While not included in the rule, it is important to note that the statute also finds the prescribed 

fires of significant users conducted on lands the primary purpose of which is nonagricultural to 

be for “commercial purposes”. The effect is to subject any such activity conducted without a 

permit to significantly higher fines than previously (i.e., up to $100/day for “noncommercial 

purposes” and up to $10,000/day for “commercial purposes”). 

 In March 2004, the Commission approved changes to Regulation No. 9 allowing the 

permitting of Air Curtain Destructors (ACD) to be used for the narrow purpose of burning 

wildland fuels generated as a result of projects to reduce the risk of wildfire. The use of ACDs 

in lieu of pile burning will significantly reduce emissions from defensible space and other types 

of wildfire risk reduction projects. 

 

(ii). The Regulation and Visibility Protection. 

 Section III.A of the regulation requires anyone seeking to conduct open burning to obtain a 

permit from the Division. Regulation No. 9 also contains a number of factors the Division must 

consider in determining whether and, if so, under what conditions, a permit may be granted. 

Many of these factors relate to potential visibility impacts in Class I areas. For example, 

 the potential contribution of such burning to air pollution in the area; 
23

 the meteorological conditions on the day or days of the proposed burning; 

 the location of the proposed burn and smoke-sensitive areas and Class I areas that might 

be impacted by the smoke and emissions from the burn; 

 whether the applicant will conduct the burn in accordance with a smoke management plan 

or narrative that requires: 

o that best smoke management methods will be used to minimize or eliminate 

smoke impacts at smoke-sensitive receptors (including Class I areas);

o that the burn will be scheduled outside times of significant visitor use in 

smoke-sensitive receptor areas that may be impacted by smoke and emissions 

from the fire; and

o a monitoring plan to allow appropriate evaluation of smoke impacts at smokesensitive receptors.

The regulation requires all prescribed fire permitees to submit an application to the Division. 

Proposed planned ignition burns are compared to computer model output that indicates the air 

pollution (including visibility) impacts. A permit is granted only if the modeling run 

demonstrates that under the prescribed meteorological conditions for the burn there will be no 

unacceptable air pollution (including visibility) impacts. The Division reviews each permit 

application and determines if the burn can be conducted without causing unacceptable visibility 

impacts within Class I areas, as well as other smoke sensitive sites. In addition, the regulation 

provides that the Division may impose “permit conditions necessary to ensure that the burn will 

be conducted so as to minimize the impacts of the fire on visibility and on public health and 

welfare.” 

 Permitees are also required to report actual activity to the Division. Depending on the size 

and type of fire, reporting may be a daily requirement. At a minimum, each year all permitees 

must indicate whether or not there was any activity in the area covered by the permit and, if so, 

how many acres were burned. The Division annually prepares a report on prescribed burning 

activity and estimated emissions. Reports from 1990 through 2006 are available by contacting 

the Division. 

 As mentioned above, the regulation requires that the draft permit for any proposed prescribed 

fire rated as having a “high” smoke risk rating be subject to a 30-day public comment period. 

The notice for the public comment period must contain information relating to the potential air 

quality and visibility impacts at smoke sensitive receptors, including Class I areas. 

 The Division’s web site contains information about the various aspects of Colorado’s Smoke 

Management Program, downloadable forms and instructions, and links. It is also used to contain 

the notices for public comment periods for the draft permits subject to public comment. The web 

site underwent a major revision and updating during 2005. It is located at: 

http://www.cdphe.state.co.us/ap/smoke/

3. CHANGES IN VISIBILITY SINCE SIP APPROVAL AND ASSESSMENT OF 

EXISTING CONDITIONS 

Visibility monitoring is being performed in or near a number of Colorado’s Class I areas. 
24

The specific purposes of monitoring may vary, but generally include assessing existing 

conditions and trends as well as learning more about the sources of visibility impairment in 

Colorado’s Class I areas. 

The routine visibility monitoring performed in Colorado’s Class I areas are at IMPROVE, 

IMPROVE Protocol or IMPROVE Look Alike sites. IMPROVE is an acronym that stands for 

Interagency Monitoring of PROtected Visual Environments. IMPROVE is a cooperative 

visibility monitoring effort of the EPA, NPS, USF&WS, BLM, USFS, Western States Air 

Resources Council (WESTAR), Mid-Atlantic Regional Air Management Association 

(MARAMA), North Eastern States for Coordinated Air Use Management (NESCAUM), and the 

National Association of Clean Air Agencies (NAACA). IMPROVE Protocol sites are operated 

using the same equipment, procedures and analytical labs as other sites in the IMPROVE 

network across the country, allowing comparisons of data from all these sites. IMPROVE Look 

Alike sites are operated using the same equipment and procedures but may utilize different labs. 

 IMPROVE sites are funded by EPA. IMPROVE Protocol sites are funded by a sponsoring 

federal land management agency or state. IMPROVE Look Alike sites may be funded by private 

industry or other entity. IMPROVE and IMPROVE Protocol sites are operated by the NPS, 

BLM, or the USFS. The State of Colorado has funded a short-term IMPROVE Look Alike site 

but does not fund other IMPROVE or IMPROVE Protocol sites. IMPROVE has an extensive 

web site at: http://vista.cira.colostate.edu/improve. Graphically processed IMPROVE data as 

well as links to photographic images of various haze levels at Class I areas and meteorological 

data are found on the Visibility Information Exchange Web System (VIEWS) at: 

http://vista.cira.colostate.edu/views/

The types of visibility monitoring being performed in Colorado’s Class I areas and some of 

the results of this monitoring are summarized later in this section of the LTS review. The section 

is divided into three major parts: 

a. Monitoring Methods and Network -- a very brief discussion of each of the types of 

routine visibility monitoring performed in Colorado and a description of the monitoring 

network in place as of December 2006. 

b. Site-By-Site Data Summaries -- summaries of the routine data available as of April 2007 

collected by these methods, a short discussion of the data, and of possible data trends of 

each site (park or wilderness area). 

c. Overall Conclusions from the Routine Monitoring -- statements about visibility levels, 

sources, and trends in Colorado’s Class I areas. 

a. Monitoring Methods and the Network. 

 Routine visibility monitoring consists of three general components. The first, view 

monitoring, is used to document the visual quality of a scene. The second component, 

atmospheric optical monitoring, measures basic optical properties of the atmosphere (e.g., 

atmospheric extinction, light scattering) that relate to the atmosphere’s ability to cause visibility 

impairment. In some of Colorado’s Class I areas atmospheric extinction has been directly 
25

measured with a transmissometer. At one of the monitoring sites, a nephelometer monitors the 

scattering coefficient of ambient air. The third component of most routine visibility monitoring 

systems, particle monitoring, measures fine atmospheric particles that are responsible for 

visibility impairment. This third component is considered the core method for IMPROVE and at 

each site, at a minimum, is a chemically speciated fine particle monitor. Each general 

component of monitoring is described in more detail below. 

(i). View Monitoring. 

 Camera systems are used to document visibility in a view from a fixed location. A specially 

constructed camera system automatically takes slides or digital images of a view at regularly 

scheduled times each day (usually three times per day). The images provide a qualitative record 

of visibility conditions that exist at a site. 

Automated camera systems are in place at the following sites to monitor visibility conditions 

in or near the following Class I areas (the letters in parentheses below are how each site is 

referenced within the FLM and IMPROVE data and image management systems): 

• Shamrock Mines (SHMI) near the Weminuche Wilderness; 

• Maroon Bells-Snowmass Wilderness site in the White River National Forest 

(MABE); and 

• Mt. Zirkel Wilderness (ZIRK). 

In the past automated camera systems operated at the following sites (the letters in 

parentheses below are how each site is referenced within the IMPROVE data management 

system): 

• Colorado National Monument (COLM); 

• Dinosaur National Monument (DINO); 

• Great Sand Dunes National Park (GRSA); 

• Mesa Verde National Park (MEVE); 

• Rocky Mountain National Park (ROMO); 

• West Elk Wilderness (WEEL); 

• La Garita Wilderness (LAGA); 

• Eagles Nest Wilderness (EANE); and 

• Weminuche Wilderness (WEMI). 

In addition, camera systems have monitored at the following Class II wilderness areas: 

• Lost Creek Wilderness (at the Devil’s Head Fire Tower) (DEHE); and 

• Mount Massive Wilderness (MOMA). 

Once a multi-year visual record of site conditions is collected, the camera systems are 

removed and installed to document conditions at another site. A spectrum of various visibility 

conditions seen on the slides taken at a given site and relationship to other monitoring if 
26

available are archived onto a photo CD and/or uploaded to web sites. Images are available at: 

http://www.fsvisimages.com/

and 

http://vista.cira.colostate.edu/views/Web/IMPROVE/Data_IMPRPhot.htm

(ii). Atmospheric Optical Monitoring. 

 Atmospheric extinction describes the ability of particles and gases in the atmosphere to 

attenuate light over a given distance (e.g., per kilometer). Extinction occurs due to the scattering 

and absorption of light from gaseous and aerosol constituents of the atmosphere. A 

transmissometer is an optical visibility monitoring device, which can continuously measure 

atmospheric extinction. The instrument accomplishes the measurement by sending a light beam 

of known intensity to a distant receiver and measuring the resulting loss of light. A 

nephelometer directly measures the scattering component of atmospheric extinction. 

High relative humidity, rain and fog events reduce visibility. Data collected during periods 

experiencing such events are often excluded from transmissometer and nephelometer data in 

order that it reflect anthropogenic influences. Transmissometer data were collected at the 

following IMPROVE sites (the letters in parentheses below are how each site is referenced 

within the IMPROVE data management system): 

• Mesa Verde National Park (MEVE), through May 1993; and 

• Rocky Mountain National Park (ROMO), through October 2006. 

Nephelometer data are collected at: 

• Mt. Zirkel Wilderness (MOZI). 

(iii). Particle Monitoring. 

 Atmospheric particle monitoring is accomplished by a combination of particle sampling and 

sample analysis. Simultaneous particulate samples are collected in the four channels of the 

IMPROVE Particle Sampler: three PM2.5 samples (particles less than 2.5 microns in diameter) on 

different filter types (Teflon, nylon, and quartz) and one PM10 sample (particles less than 10 

microns in diameter) on a Teflon filter. The filters are subsequently analyzed for total mass, 

elements, organic and light absorbing carbon, ions, and optical absorption. Particulate 

monitoring is used to quantify and identify the air pollutants responsible for visibility 

degradation. Atmospheric extinction can be mathematically reconstructed from these chemically 

speciated aerosol samples – this is the core method EPA has selected for monitoring haze. 

Typically, an IMPROVE Sampler takes a 24-hour sample once every three days. The 

IMPROVE web site contains literature that indicates12 the overall uncertainty (defined as the 

ratio of the mean precision from all sources divided by the mean concentration) is 4% to 7% for 

most variables and >15% for organic carbon. These numbers reflect precision; accuracy is 

unknown. 

 Particulate monitoring with an IMPROVE Sampler is performed in or near the following 
27

Colorado Class I areas (the letters in parentheses below are how each site is referenced within 

the IMPROVE data management system): 

• Great Sand Dunes National Monument (GRSA). 

• Mesa Verde National Park (MEVE). 

• Weminuche Wilderness Area (WEMI). 

o This monitoring site also represents visibility conditions in La Garita 

Wilderness and Black Canyon of the Gunnison Wilderness. 

• Shamrock Mines (SHMI). 

o This site was installed in 2005 and is a supplemental site for assessing impacts 

to the Weminuche Wilderness Area from emissions activity in the Four 

Corners Area. 

• Snowmass/Maroon Bells Wilderness site in the White River National Forest (WHRI). 

o This monitoring site also represents visibility conditions in West Elk 

Wilderness, Eagles Nest Wilderness, and Flat Tops Wilderness. 

• Mount Zirkel Wilderness Area (MOZI). 

o This site also represents visibility conditions in the Rawah Wilderness. 

• Rocky Mountain National Park (ROMO). 

• Ripple Creek Pass (RICR). 

o This site is to the north of the Flat Tops Wilderness. It is funded privately by 

Shell Oil Company and operated by Air Sciences, Incorporated. 

• Douglas Pass (DOPA). 

o This site operated at the top of Douglas Pass near the Utah border for over 2 

years. It was funded by the Colorado Governor’s Office of Energy 

Management and Conservation and operated by Air Sciences, Incorporated. 

b. Routine Monitoring Data Summary. 

 A number of the visibility monitoring sites in Colorado’s Class I areas have been in operation 

for several years. Table 5 below is a summary of the types of monitoring and the dates when 

monitoring has occurred at each of the sites. 

Table 5 

Routine Visibility Monitoring 

SITE CAMERA TRANSMIS

-SOMETER

NEPHELOMETER IMPROVE 

PARTICULATE 

MONITORING 

SITE TYPE1

BLCA 

Black 

Canyon NP 

2/85-11/93 BLM - 

IMPROVE 

PROTOCOL 

 

1 IMPROVE Protocol sites are operated using the same equipment and procedures as other sites in the IMPROVE network 

across the country, allowing comparisons of data from all these sites. IMPROVE sites are funded by EPA. IMPROVE Protocol 

sites are funded by the sponsoring federal land management agency or state. Sites are operated by the NPS, BLM, or the USFS.
28

SITE CAMERA TRANSMIS

-SOMETER

NEPHELOMETER IMPROVE 

PARTICULATE 

MONITORING 

SITE TYPE1

COLM 

Colorado 

NM 

7/81-9/91 

 NPS – 

IMPROVE 

PROTOCOL 

COLP 

LouisianaPacific 

7/92-1/97 NPS - 

IMPROVE 

PROTOCOL 

DEHE 

Devil’s 

Head Fire 

Tower 

Lost Creek 

WA 

5/94-1/02 USFSIMPROVE 

PROTOCOL 

DINO 

Dinosaur 

NM 

9/79-2/81 

6/85-9/91 

NPSIMPROVE 

PROTOCOL 

DOPA 

Douglas 

Pass 

9/03-1/06 ColoradoIMPROVE 

Look Alike 

EANE 

Eagle’s Nest 

WA 

6/93-9/00 USFSIMPROVE 

PROTOCOL 

GRSA 

Great Sand 

Dunes NP 

7/87-4/95 5/88-present NPS - 

IMPROVE 

LAGA 

La Garita 

WA 

9/97-10/01 USFSIMPROVE 

PROTOCOL 

MEVE 

Mesa Verde 

NP 

9/79-4/95 9/88-7/93 3/88-present NPS - 

IMPROVE 

MOMA 

Mt. Massive 

WA 

7/97-11/01 USFS - 

IMPROVE 

PROTOCOL 

MOZI 

Mt. Zirkel 

10/90-

present (on 

12/93-present 12/93-present USFS - 

IMPROVE 
29

SITE CAMERA TRANSMIS

-SOMETER

NEPHELOMETER IMPROVE 

PARTICULATE 

MONITORING 

SITE TYPE1

WA Storm Peak)

RICR 

Ripple 

Creek Pass 

Flat Tops 

WA 

12/02-present Shell OilIMPROVE 

Look Alike 

ROMO 

Rocky Mtn. 

NP 

10/85-1/95 12/87-10/06 10/87-present NPS - 

IMPROVE 

SHMI 

Shamrock 

Mines 

Weminuche 

WA

11/05-

present 

USFS – 

IMPROVE 

PROTOCOL 

WEEL 

West Elk 

WA 

7/92-11/96 USFS - 

IMPROVE 

PROTOCOL 

WEMI 

Weminuche 

WA 

7/86-8/93 3/88-present USFS - 

IMPROVE 

WHRI/ 

MABE 

Maroon 

Bells/ 

Snowmass 

WA 

12/91-

present 

7/93-9/99 (channel 

A only) 

9/99- (full 

IMPROVE) 

USFS – 

IMPROVE 

PROTOCOL 

USFS – 

IMPROVE 

 In 2003, two temporary sites were installed in Western Colorado. The sites use IMPROVE 

protocols and equipment but are unable to utilize one of the analytical laboratories under 

contract to the long-term sites. As such, these temporary sites are known as IMPROVE Look 

Alike sites. One is at the north end of the Flat Tops Wilderness at Ripple Creek Pass and is 

funded by Shell Exploration and Production Company. The other was to the west of the first site 

nearly on the border with Utah at Douglas Pass. It has been discontinued. This site was funded 

by the Colorado Governor’s Office of Energy Management and Conservation. The sites were 

installed and operated by a consulting firm, Air Sciences, Incorporated. The Division has 

provided technical support and advice as needed. As data are processed from these sites, they 

are uploaded to the VIEWS site annually. Data analysis from these sites are included in the 

Regional Haze SIP Technical Support Documents (TSDs). 
30

 A new IMPROVE protocol site has recently (Fall 2005) been added to the network within 

Colorado by the USFS. The Shamrock Mines site near Vallecito and the Weminuche Wilderness 

is intended to supplement the existing Weminuche Wilderness site. Shamrock Mines is at a 

much lower altitude than the current site. NOx and ozone are also monitored at the new site. 

The USFS is concerned with the cumulative impacts of oil and gas development in the 4-corners 

region and believes the new location will better capture pollutants in the area. 

 For IMPROVE and IMPROVE Protocol sites in Colorado the camera, transmissometer, and 

nephelometer based data are collected, analyzed, and archived by Air Resource Specialists, Inc. 

(ARS), the contractor to IMPROVE, NPS, USFS and BLM for optical data. The particle data 

are collected, analyzed and archived by the University of California at Davis, the contractor to 

IMPROVE, NPS, USFS and BLM for particle measurements. For the IMPROVE Look Alike 

sites, Air Sciences, Inc. operates the sites and uses the same lab except for the University of 

California at Davis. Instead, RTI, Inc. is utilized. For all sites, the raw data may be downloaded 

from the IMPROVE or VIEWS web sites. 

c. Site-By-Site Data Summaries. 

Due to the extensive data analyses and displays within the Technical Support Documents and 

other sections of the Regional Haze SIP submittal, this LTS Review’s focus is solely on trends at 

sites with more than 3 years of data. Trends in the haze index, known as deciview (dv) are 

provided for both the Best 20% days each year and Worst 20% days each year. These plots have 

been copied from the VIEWS web site. An additional focus is on the data since the last LTS 

Review in 2004. 

(i). Mesa Verde National Park. 

 Processed IMPROVE Sampler data are available beginning in 1989 through 2004 at Mesa 

Verde National Park. Figure 1 presents annual average deciview for the best and worst days for 

each year of available data at the Park. 

The Best Days show no particular trend but are not degrading. The Worst Days appear to 

have an overall steady increase in impairment beginning in 1992 through 2000. 2001 is the 

lowest year on record and 2002/2003 are the worst years on record. 2004 again returns to low 

values similar to 2001. To explore these trends and the recent extreme variability further, Figure 

2 contains a speciated look at the Worst Days from 1989 through 2004. A qualitative summary 

of Figure 2 by pollutant shows that: 

• ammNO3f_bext (ammonium nitrate extinction) is an anthropogenic pollutant and a minor 

contributor to visibility impairment at Mesa Verde. Nitrate shows an increasing trend 

beginning around 1999 and continuing through 2004. 

• ammSO4f_bext (ammonium sulfate extinction) is an anthropogenic pollutant and a major 

contributor at the Park. Sulfate shows an overall decreasing trend over the years. 

• CM_bext (coarse mass extinction) is a moderate contributor and mostly consists of 

natural sources (e.g., wind blown dust). Coarse mass shows a lot of variability early in 

the record and again after 1999 likely corresponding to dust events and overall dry 

conditions. 

• ECf_bext (elemental carbon extinction) is both an anthropogenic and naturally occurring 
(e.g., wildfire) pollutant. It is a minor contributor at Mesa Verde with no particular trend 

but demonstrates more variability beginning in 2000. 

Figure 1: Mesa Verde National Park, Best and Worst Days, 1989 through 2004 

• OMCf_bext (organic carbon extinction) is largely a naturally occurring pollutant (e.g., 

wildfire). Over the period of monitoring at Mesa Verde, it starts fairly high early in the 

record then drops and begins a slow increase until 2000. Beginning in 2000, there is a 

period of “ups and downs” corresponding to the period of drought and wildfire in the 

West. Organic carbon emerges in recent years as the most important contributor to 

impairment and variability in impairment at Mesa Verde NP. 

• SOILf_bext (fine soil extinction) is largely natural (e.g., dust) with very low values early 

in the record at the Park with increases corresponding to the drought period. 

 The influence of drought and related emissions from wildfire and dust events is evident. 

Figure 3 examines precipitation at Mesa Verde National Park from 1990-1997 versus 1998-

2004. Average precipitation is around 6 inches lower in the more recent period and several 

years (1999-2002) have annual averages between 11.6 and 13.8 inches, reflecting the 

profound drought in the area. 

(ii). Weminuche Wilderness Area. 

Processed IMPROVE Sampler data are available beginning in 1989 through 2004 at 

Weminuche Wilderness Area. Figure 5 presents annual average deciview for the best and worst 

days for each year of available data at the Wilderness. 

 The Best Days show no degradation and a steady trend toward less impairment. The 

31
Worst Days appear to have a slight increase in impairment beginning in 1993 through 2000. 

2001 is the lowest year on record and 2002/2003 are the 3rd and 4th worst years on record. 2004 

again returns to low values similar to 2001. To explore these trends and the recent extreme 

variability further, Figure 6 contains a speciated look at the Worst Days from 1989 through 

2004. A qualitative summary of Figure 6 by pollutant shows that: 

Figure 2: Mesa Verde National Park, Annual Extinction Values by Aerosol Species, Worst 

Days 1989 through 2004 

Precipitation at Mesa Verde National 

Park

12

14

16

18

20

22

Inches of Precipitation

1990-1997 1998-2004

Figure 3: Precipitation At Mesa Verde National Park, 1990-1997 vs 1998-2004 

32
Figure 5: Weminuche Wilderness Area, Best and Worst Days 1989 through 2004

• ammNO3f_bext (ammonium nitrate extinction) is an anthropogenic pollutant and a minor 

contributor to visibility impairment at Weminuche. Nitrate shows an increasing trend 

beginning around 1997 and continuing through 2003. The 2004 value is less than recent 

years and is similar to what was measured in 2001. 

• ammSO4f_bext (ammonium sulfate extinction) is an anthropogenic pollutant and a major 

contributor at the Park. Sulfate shows an overall decreasing trend since 1998. 

• CM_bext (coarse mass extinction) is a moderate contributor and mostly consists of 

natural sources (e.g., wind blown dust). Coarse mass shows a lot of variability early in 

the record and again after 1999 likely corresponding to dust events and overall dry 

conditions. 

• ECf_bext (elemental carbon extinction) is both an anthropogenic and naturally occurring 

(e.g., wildfire) pollutant. It is a moderate contributor at Weminuche with a slight shift to 

lower values beginning in 1997. 

• OMCf_bext (organic carbon extinction) is largely a naturally occurring pollutant (e.g., 

wildfire). Over the period of monitoring at Weminuche, it starts fairly high early in the 

record then drops and begins a slow increase until 2001. Beginning in 2001, there is a 

period of large variability corresponding to the period of drought and wildfire in the West 

and particular fires near and in the Weminuche Wilderness. Organic carbon emerges in 

33
recent years as the most important contributor to impairment and variability in 

impairment at Weminuche. 

• SOILf_bext (fine soil extinction) is largely natural (e.g., dust) with very low values 

(similar to nitrate) early in the record at the Park with increases corresponding to the 

drought period. 

Figure 6: Weminuche Wilderness Area, Annual Extinction Values by Aerosol Species, 

Worst Days 1989 through 2004 

(iii). Great Sand Dunes National Park. 

Processed IMPROVE Sampler data are available beginning in 1989 through 2004 at Great 

Sand Dunes National Park. Figure 7 presents annual average deciview for the best and worst 

days for each year of available data at the Park. 

The Best Days show a little change and overall no degradation since 1999. The Worst Days 

appear to have a slight increase in impairment beginning in 1996 through 2000. 2001 is among 

the lowest years on record, followed by 2002: the highest on record. 2003 is the 4th worst and 

2004 again returns to low values similar to 2001 and among the lowest on record. To explore 

these trends and the recent extreme variability further, Figure 8 contains a speciated look at the 

Worst Days from 1989 through 2004. A qualitative summary of Figure 8 by pollutant shows 

that: 

34
Figure 7: Great Sand Dunes National Park, Best and Worst Days 1989 through 2004

• ammNO3f_bext (ammonium nitrate extinction) is an anthropogenic pollutant and a minor 

contributor to visibility impairment at Great Sand Dunes. Nitrate shows a slight 

increasing trend beginning around 2000 and continuing through 2004, with a dramatic 

exception in 2003 (among the lowest values on record). The 2004 value is the highest on 

record. 

• ammSO4f_bext (ammonium sulfate extinction) is an anthropogenic pollutant and a major 

contributor at the Park. Sulfate shows an overall decreasing trend since 1998. 

• CM_bext (coarse mass extinction) is a major contributor and mostly consists of natural 

sources (e.g., wind blown sand/dust). Coarse mass shows a huge amount of variability 

over its record with the “ups and downs” tracking closely with Organic Carbon in recent 

years. 

• ECf_bext (elemental carbon extinction) is both an anthropogenic and naturally occurring 

(e.g., wildfire) pollutant. It is a minor contributor at Great Sand Dunes NP with no 

discernable trend. 

• OMCf_bext (organic carbon extinction) is largely a naturally occurring pollutant (e.g., 

wildfire). Over the period of monitoring at Great Sand Dunes, it begins an “up and 

down” pattern in 1995 thru 2003. The pattern is broken by 2004 as its value continues in 

2003’s declining direction. 

• SOILf_bext (fine soil extinction) is largely natural (e.g., sand/dust) with very low values 

(similar to nitrate) early in the record at the Park with increases corresponding to the 

35
drought period. Fine soil, coarse mass and organic carbon emerge in recent years as the 

most important contributors to impairment and variability in impairment at Sand Dunes. 

Figure 8: Great Sand Dunes National Park, Annual Extinction Values by Aerosol Species, 

Worst Days 1989 through 2004 

(iv). White River National Forest - Maroon Bells/Snowmass Wilderness. 

 Processed IMPROVE Sampler data are available beginning in 2001 through 2004 at 

the White River site. Figure 9 presents annual average deciview for the best and worst 

days for each year of available data at the site. All other IMPROVE sites in Colorado 

have much longer data records, in most cases over 15 years. However, the White River 

site was installed during 2000, with the first complete data year in 2001. Based on the 

four years of processed data, White River is Colorado’s least impaired site compared to 

other IMPROVE locations in the state.

 The Best Days show a no degradation trend over the four years of data. The Worst 

Days spike-up in 2002 but return to the 2001 value in 2003 and decline further in 2004. 

To explore these trends, Figure 10 contains a speciated look at the Worst Days from 

1981 through 2004. A qualitative summary of Figure 10 by pollutant shows that:

36
Figure 9: White River National Forest, Best and Worst Days 2001 through 2004

• ammNO3f_bext (ammonium nitrate extinction) is an anthropogenic pollutant and a minor 

contributor to visibility impairment at the White River site. Nitrate shows a slight 

decreasing trend through 2004. 

• ammSO4f_bext (ammonium sulfate extinction) is an anthropogenic pollutant and a 

moderate contributor at the White River site. Sulfate shows an overall decreasing trend. 

• CM_bext (coarse mass extinction) is fairly moderate contributor and mostly consists of 

natural sources (e.g., wind blown sand/dust). Compared to other sites in Colorado 

examined previously, there has been little relative variability in course mass and it 

declined in 2003 and 2004. 

• ECf_bext (elemental carbon extinction) is both an anthropogenic and naturally occurring 

(e.g., wildfire) pollutant. It is a minor contributor at the wilderness areas represented by 

the White River site and has had only a small amount of variability in the four years 

monitored. 

• OMCf_bext (organic carbon extinction) is largely a naturally occurring pollutant (e.g., 

wildfire). Organic carbon is a moderate contributor at White River, with the exception of 

2002 when it spiked (likely due to upwind wildfire) and influenced impairment at the site 

more than the sum of the other pollutants combined. 

• SOILf_bext (fine soil extinction) is largely natural (e.g., sand/dust) with very low values 

(similar to nitrate). 

37
Figure 10: White River National Forest, Annual Extinction Values by Aerosol Species, 

Worst Days 2001 through 2004 

(v). Mt Zirkel Wilderness Area. 

Processed IMPROVE Sampler data are available beginning in 1995 through 2004 at Mt. 

Zirkel Wilderness Area. Figure 11 presents annual average deciview for the best and worst days 

for each year of available data at the Wilderness. 

 The Best Days show a no degradation trend over the 9 years of data (2000 was incomplete) 

with a fairly dramatic decline in impairment in recent years. The Worst Days do not exhibit any 

obvious trend; however, 2004 was the lowest on record. To explore these data further, Figure 12 

contains a speciated look at the Worst Days from 1995 through 2004. A qualitative summary of 

Figure 12 by pollutant shows that: 

• ammNO3f_bext (ammonium nitrate extinction) is an anthropogenic pollutant and a minor 

contributor to visibility impairment at Mt. Zirkel Wilderness Area. In recent years nitrate 

has increased and appears to be a moderate level contributor. 

• ammSO4f_bext (ammonium sulfate extinction) is an anthropogenic pollutant and a major 

contributor at the Park. Sulfate shows an overall decreasing trend since 1998. 

• CM_bext (coarse mass extinction) is a moderate contributor and mostly consists of 

natural sources (e.g., wind blown sand/dust). Compared to the more southern sites, 

coarse mass at Mt. Zirkel shows little variability over its record and an overall declining 

trend. 

38
Figure 11: Mt. Zirkel Wilderness Area, Best and Worst Days 1995 through 2004

• ECf_bext (elemental carbon extinction) is both an anthropogenic and naturally occurring 

(e.g., wildfire) pollutant. It is a minor contributor at Mt. Zirkel Wilderness Area with no 

discernable trend. 

• OMCf_bext (organic carbon extinction) is largely a naturally occurring pollutant (e.g., 

wildfire) and a major contributor to impairment at this site. Over the period of 

monitoring at Mt. Zirkel Wilderness, organic carbon exhibits considerable variability 

and, similar to most other Colorado sites, had large annual worst day values for 2002 and 

2003. 

• SOILf_bext (fine soil extinction) is largely natural (e.g., sand/dust) with very low values 

(similar to nitrate). 

(vi). Rocky Mountain National Park. 

Processed IMPROVE Sampler data are available beginning in 1991 through 2004 at Rocky 

Mountain National Park. Figure 13 presents annual average deciview for the best and worst days 

for each year of available data at the Park. 

 

 The Best Days show no degradation over time and a trend toward less impairment. The most 

recent years are the cleanest on record. The Worst Days reflect the drought and shift up from 

2000 through 2003. To explore these trends and the recent increase on the Worst Days further, 

Figure 14 contains a speciated look at the Worst Days from 1991 through 2004. A qualitative 

39
Figure 12: Mt. Zirkel Wilderness Area, Annual Extinction Values by Aerosol Species, 

Worst Days 1995 through 2004 

summary of Figure 14 by pollutant shows that: 

• ammNO3f_bext (ammonium nitrate extinction) is an anthropogenic pollutant and shifts 

from a moderate contributor to visibility impairment at Rocky to a major contributor in 

2001 and 2002. Values for 2003 and 2004 drop to more typical levels. Nitrate shows a 

decreasing trend from the beginning of the record through 2000 then the two-year spike 

occurs. Rocky Mountain National Park’s nitrate levels are higher overall than other 

IMPROVE sites in Colorado. The two-year spike is unusual given that nitrate is largely 

an anthropogenic pollutant. 

• ammSO4f_bext (ammonium sulfate extinction) is an anthropogenic pollutant and a major 

contributor at the Park. In contrast with other IMPROVE sites in Colorado, sulfate does 

not demonstrate an obvious declining trend over the data record. However, considering 

the period 1999 through 2004, there are 4 of the 5 lowest values in the data record. 

Similar to what was seen for nitrate, the sulfate spike in 2001 and 2002 may need further 

exploration. 

• CM_bext (coarse mass extinction) is a moderate contributor. In 2000, it spiked and for 

that single year it was a major contributor, along with organic carbon. Coarse mass 

emissions mostly consist of natural sources (e.g., wind blown dust). Coarse mass does 

not reveal an obvious trend over the record and there is a lesser reflection, compared to 

40
Figure 13: Rocky Mountain National Park, Best and Worst Days 1991 through 2004

 

 many other sites in Colorado, of the drought in recent years. 

• ECf_bext (elemental carbon extinction) is a both an anthropogenic (e.g., diesel 

emissions) and naturally occurring (e.g., wildfire) pollutant. It is a minor contributor at 

Rocky Mountain NP with no particular trend. 

• OMCf_bext (organic carbon extinction) is largely a naturally occurring pollutant (e.g., 

wildfire). Over the period of monitoring at Rocky Mountain National Park, the “ups and 

downs” seen at other sites also have occurred at Rocky as well as the large values during 

the peak drought years. 

• SOILf_bext (fine soil extinction) is largely natural (e.g., dust) with low values throughout 

the record at the Park. 

 In order to explore further the unusual nitrate and sulfate levels in 2001 and 2002, additional 

plots are presented below from the VIEWS website. They are the 2000, 2001 and 2002 annual 

composition plots for Rocky Mountain National Park. Each stacked bar represents a 24-hour 

sample. Each bar component is one of the species listed on the plot legend. The “W” over a bar 

means that sample is among the worst 20% impaired during that year. A “B” over a bar 

indicates that sample is in the 20% best visibility days during that year. Figure 15 is 2000 data. 

This is a fairly typical year for sulfate and nitrate at Rocky. There are no combined sulfate and 

nitrate episodes above 20/Mm-1 of extinction. Figure 16 is 2001 data. There are 9 sample days 

with combined sulfate and nitrate above 20/Mm-1. Figure 17 is 2002 data. There appear to be 7 

or 8 

41
Figure 14: Rocky Mountain National Park, Annual Extinction Values by Aerosol Species, 

Worst Days 1991 through 2004 

such days in 2002. It is important to note that these episodes, with 1 or 2 minor exceptions, do 

not occur when other pollutants are also peaking. The Division is hopeful that results from the 

ROMANS study, conducted by the National Park Service to examine nitrogen and sulfate 

emissions and precursors at Rocky Mountain National Park, will provide some insight about the 

sources and meteorological conditions that occurred in 2001 and 2002 that led to the 7-9 peaks 

of sulfate and nitrate per year. For more information about the ROMANS study see 

http://www.cira.colostate.edu/publications/newsletter/fall2006.pdf

42
Figure 15: Rocky Mountain National Park, Composition Plot by Aerosol Species for Each 

Sample in 2000

Figure 16: Rocky Mountain National Park, Composition Plot by Aerosol Species for Each 

Sample in 2001 

43
Figure 17: Rocky Mountain National Park, Composition Plot by Aerosol Species for Each 

Sample in 2002 

d. Overall Conclusions. 

 Colorado has among the best visibility in the country at its Class I areas and throughout other 

scenic and pristine parts of the State. However, on an episodic basis visibility can become 

impaired at all sites monitored. 

 Visibility on the best days is not degrading over time at any site in Colorado. This is good 

and important news as protecting the cleanest days is a critical aspect of the Class I visibility 

protection program. 

 Visibility on the worst days is a more complex assessment. Mesa Verde NP shows a slow 

and steady increase in impairment over time. Weminuche and Great Sand Dunes show a very 

slight increase in impairment. Rocky Mountain and Mt. Zirkel show little apparent trend. At all 

these sites the most recent years of complete data have large variation from year-to-year driven 

largely by the sustained drought in the West. In addition to direct impacts from the drought, 

fewer precipitation events equate to less of a potential for natural removal mechanisms (i.e., rain 

and snow storms) scrubbing particles out of the air. The data record for White River is too short 

to draw conclusions at this time regarding trends. 

4. ADDITIONAL MEASURES, INCLUDING SIP REVISIONS, THAT MAY BE 

NECESSARY TO ENSURE REASONABLE PROGRESS TOWARD THE NATIONAL 

GOAL. 

Substantive LTS SIP revisions occurred in August 1996, April 1997, and April 2001. The 

2002 SIP revision was to update outdated language and create a better overall organization of the 

LTS portion of the SIP. A minor update occurred in 2004. The Division does not believe 

extensive and substantive revisions are necessary at this time to ensure reasonable progress 

toward the national goal under Phase I of the Class I Visibility Protection Program. However, 

once again, small updates and edits are proposed in order that this part of the SIP does not 

44
45

become outdated. 

5. THE PROGRESS ACHIEVED IN IMPLEMENTING BART AND MEETING OTHER 

SCHEDULES SET FORTH IN THE LONG-TERM STRATEGY. 

Hayden. Emission limitations and schedules for Hayden Generating Station were adopted 

into the SIP on August 15, 1996 based on the Hayden Consent Decree. By terms of the Decree, 

Hayden Station must provide progress reports to the State concerning construction of new 

equipment and compliance with new emission limitations. The particulate and SO2 control 

equipment for Units 1 & 2 have been installed and are operating. All schedules in both the 

Decree and in the SIP regarding Hayden were met, some up to six months ahead of deadlines in 

the SIP and Consent Decree. Both units were in compliance for all pollutants by November 16, 

1999. The emission limits and reporting requirements have been integrated into Hayden’s Title 

V permit, as envisioned by the Consent Decree. As such, the court terminated the Decree in late2001. Since then Hayden has continued to operate the facility within its emission limits and has 

remained in compliance. 

Craig. Emission limitations and schedules for Units 1 and 2 of the Craig Station were 

adopted into the SIP on April 19, 2001 based on the Craig Consent Decree. By the terms of the 

SIP, progress reports must be provided to the State. 

Unit 1’s tie-in with its new equipment began on September 13, 2003 and completion of PM, 

NOx and SO2 upgrades were finished by December 19, 2003. Testing of the NOx upgrades 

continued through the end of 4th quarter 2003. SO2 removal has consistently been above 90% 

since mid-December 2003 (limit is 90%). The NOx limit is 0.30 lbs/Mmbtu annual average and 

the end of 2005 actual average was 0.279 lbs/Mmbtu. 

Unit 2’s tie-in began on March 13, 2004. The compliance period began on October 1, 2004 

for all subject pollutants. SO2 emissions from Unit 2 have also consistently achieved better than 

90% removal and the NOx annual average has been below the required 0.30 lbs/Mmbtu. 

The emission limits and reporting requirements have been integrated into Craig’s Title V 

permit, as envisioned by the Consent Decree. As such, the court terminated the Decree in late2005. Since then Craig has continued to operate the facility within its emission limits and has 

remained in compliance. 

6. THE IMPACT OF ANY EXEMPTION FROM BART. 

The Division has not made a reasonable attribution decision. The need for a BART analysis 

has not been triggered, therefore, exemptions were neither requested nor granted. 

7. THE NEED FOR BART TO REMEDY EXISTING IMPAIRMENT IN AN 

INTEGRAL VISTA DECLARED SINCE PLAN APPROVAL. 

There have been no integral vistas listed by either the federal land managers or the State since 

the plan was approved. Therefore, a discussion on the need for BART in such integral vistas is 

not necessary. 
46

IV. CONSULTATION WITH FEDERAL LAND MANAGERS 

The Division is required by federal and state law to provide at least 60 days to consult with 

the federal land managers during periodic reviews of the LTS. The Division is sending this 

report to the USFS and NPS at the time of the request for hearing before the Air Quality Control 

Commission. These agencies are the managers of all of Colorado’s Class I areas. 
47

 

V. ENDNOTES AND REFERENCES 

1. Letter to Honorable Roy Romer, Governor of Colorado, from Elizabeth Estill, Regional 

Forester, U.S. Forest Service Rocky Mountain Region, July 14, 1993. 

2. “Revision of Colorado’s State Implementation Plan for Class I Visibility Protection, 

Craig Station Units 1 and 2 Requirements,” adopted by the Colorado Air Quality Control 

Commission, April 19, 2001. 

3. “Clean Air Act Approval and Promulgation of Air Quality Implementation Plan Revision 

for Colorado; Long-Term Strategy of State Implementation Plan for Class I Visibility 

Protection: Craig Station Requirements,” 66 Federal Register, 35374. 

4 . Watson, J.G. and D. Blumenthal 1996, Mt. Zirkel Wilderness Area, Reasonable 

Attribution Study of Visibility Impairment; Volume II: Results of Data Analysis and 

Modeling, Part 1 of 2 -- Final Report; July 1, 1996. Desert Research Institute, University 

and Community College System of Nevada, 5625 Fox Avenue, Reno, Nevada 89506. 

5. In the United States District Court for the District of Colorado, Civil Action No. 93-B1749, Sierra Club, Plaintiff, vs. Public Service Company of Colorado, Inc., Salt River 

Project Agricultural Improvement and Power District, and PacifiCorp, Defendants, 

United States of America and State of Colorado, Plaintiff-Intervenors, Consent Decree, 

date lodged in Court, May 22, 1996, date entered in Court, August 19, 1996. 

6. “Clean Air Act Approval and Promulgation of Air Quality Implementation Plan Revision 

for Colorado; Long-Term Strategy of State Implementation Plan for Class I Visibility 

Protection, Part I: Hayden Station Requirements,” January 16, 1997, 62 Federal 

Register, 2305. 

7. “Craig Station FGD System Modifications – Analyses of Potential Alternatives, Project 

Design Basis and Cost Estimates”, EPA Contract #’s 68-D7-0001 – Phase # 1-005 & 9X0264-NALX, dated August 31, 1999. 

8. C.R.S. 25-7 Part 10, “Air Quality Related Values – Class I Federal Areas.” 

9. Letter to Honorable Bill Owens, Governor of Colorado from William P. Yellowtail, 

Regional Administrator, EPA Region 8; September, 22, 1999. 

10. Letter from Tom L. Thompson, Acting Regional Forester, U.S.D.A. Forest Service, 

Rocky Mountain Region to Margie Perkins, Director, Colorado Air Pollution Control 

Division, December 14, 2000. 

11. “Regional Haze Regulations,” July 1, 1999, 64 Federal Register 35714, (codified at Part 

40 Code of Federal Regulations sections 51.308 and 309). 
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12 . “IMPROVE Data Guide: A Guide to Interpret Data”, University of California Davis, 

August 1995.