8 - 1 

8.0 Attainment Demonstration and Weight-of-Evidence 

As described in Section 4.1.1, all of Connecticut is classified by the EPA as moderate 

nonattainment for the 8-hour ozone NAAQS. EPA requires that states with moderate (and 

above) ozone nonattainment areas prepare and adopt SIP revisions demonstrating attainment of 

the 8-hour ozone standard using photochemical grid modeling and weight-of-evidence (WOE) 

analyses. States with moderate nonattainment areas are required to attain the 8-hour ozone 

NAAQS by June 15, 2010. Because the June 15, 2010 deadline occurs in the middle of the 2010 

ozone season, Connecticut and other states with moderate nonattainment areas must demonstrate 

NAAQS compliance for the preceding ozone season of 2009. 

Sections 8.1 through 8.4 of this document describe the procedures, inputs and results of the 

regional photochemical grid modeling exercise. Section 8.5 describes various WOE analyses 

used as supplements to the modeling results to determine the likelihood of attaining the 8-hour 

NAAQS in both the Greater Connecticut nonattainment area and the Southwest Connecticut 

portion of the NY/NJ/CT nonattainment area. 

CTDEP’s primary conclusions based on the results of the photochemical modeling and WOE 

analyses are: 

1) There is a high level of probability that the Greater Connecticut area will achieve 

attainment of the 8-hour ozone NAAQS by the end of the 2009 ozone season; and 

2) A credible case can be made that Southwest Connecticut will attain by the end of the 

2009 ozone season. The probability of attainment increases as additional emission 

reductions occur in each subsequent year, such that attainment by 2012 is highly 

probable. 

8.1 Background and Objective of the Photochemical Modeling 

The objective of the photochemical modeling study is to enable the CTDEP to analyze the 

efficacy of various control strategies, and to demonstrate that the measures adopted as part of the 

SIP will result in attainment of the 8-hour ozone standard by the June 15, 2010 deadline for 

moderate nonattainment areas. The modeling exercise predicts future year 2009 and 2012 air 

quality conditions based on the worst observed ozone episodes in the base year 2002 and 

demonstrates the effectiveness of new control measures in reducing air pollution. 

The photochemical modeling was performed as part of a regional partnership under the auspices 

of the Ozone Transport Commission (OTC), a multi-state ozone planning organization created 

under the CAA to assist EPA and the states from Virginia to Maine, the Ozone Transport Region 

(OTR), with the development and implementation of regional solutions to the ground-level 

ozone problem in the Northeast and Mid-Atlantic regions. The OTC Air Directors served as the 

Oversight Committee for the modeling process, providing overall direction for all aspects of the 

modeling and control strategy development. Day-to-day management and coordination of 

modeling activities was provided by the OTC Modeling Committee, with the following 

workgroups established to accomplish assigned tasks. The various committees and workgroups 

were comprised of state air quality agency staff members (including CTDEP representatives), 
8 - 2 

with support provided by OTC and the staff of the Mid-Atlantic Regional Air Management 

Association (MARAMA). 

Photochemical Modeling Workgroup

The Photochemical Modeling Workgroup was responsible for preparing the modeling 

assessment, collecting and processing model input data, setting up all model input files, 

performing model runs and interpreting and documenting the results of the modeling analyses 

The Workgroup also prepared and submitted all OTC SIP quality modeling system 

documentation to the Oversight Committee. 

Meteorological Modeling Workgroup

The Meteorological Modeling Workgroup was responsible for preparing and assessing 

meteorological fields for the OTR Modeling Domain. This Workgroup also worked with the 

Photochemical Modeling Workgroup to prepare all meteorological input files for the OTC SIP 

quality modeling system. 

Emission Inventory Development Workgroup 

The Emission Inventory Development Workgroup was responsible for obtaining and developing 

guidance for preparing 2002 and 2009 state emission inventories for all states in the OTR. 

MARAMA and the Mid-Atlantic/Northeast Visibility Union (MANE-VU) organizations 

provided funding for contractors and worked with OTR states to help prepare state-of-the-art 

2002 emission files, 2009 and 2012 CAA emission files and 2009 and 2012 Control Strategy 

emission files for the states in the OTR Modeling Domain. The Oversight Committee was 

responsible for obtaining emission inventories for non-OTR states in the OTR Modeling 

Domain. 

Control Strategy Development Workgroup 

The Control Strategy Development Workgroup was responsible for evaluating control strategies 

and recommending to the Oversight Committee a suite of measures for attaining the ozone 

NAAQS in the OTR. Control strategy evaluation and selection was coordinated with the OTC 

Stationary/Area Source committee and the OTC Mobile Source Committee. 

8.1.1 Conceptual Description 

EPA recommends that a conceptual description of the area’s ozone problem be developed prior 

to the initiation of any air quality modeling study. A “conceptual description” is a qualitative 

way of characterizing the nature of an area’s nonattainment problem. Within the conceptual 

description of a particular modeling exercise, it is recommended that the specific meteorological 

parameters that influence air quality be identified and qualitatively ranked in importance. 
8 - 3 

A conceptual description of the ozone air quality problem in the OTR was prepared by the 

Northeast States for Coordinated Air Use Management (NESCAUM)1 and is reproduced in 

Appendix 2A. A summary of key findings of the conceptual model was provided earlier in 

Section 2.0. 

8.1.2 Regional Modeling Protocol 

All aspects of the modeling effort were conducted in accordance with the modeling protocol 

developed by the OTC Modeling Committee (see Appendix 8A). The lead agency for 

coordinating and performing modeling runs for the OTC was the New York State Department of 

Environmental Conservation (NYSDEC). Modeling centers for the OTC included the NYSDEC, 

the University of Maryland at College Park (UMD), NESCAUM, the New Jersey Department of 

Environmental Protection (NJDEP) and the Virginia Department of Environmental Quality 

(VADEQ). Although NYSDEC was the lead agency for coordinating modeling runs, member 

states of the OTC, through participation on the OTC Modeling Committee and associated 

workgroups, managed the modeling project jointly. 

8.2 Modeling Platform and Configuration

The following discussion provides an overview of the air quality, meteorological, and emission 

modeling systems used for the analysis, as well as a description of model configuration and 

quality assurance procedures. Much of this discussion is based on modeling documentation 

prepared by NYSDEC2

 for the OTC states and boilerplate OTR summaries included as part of 

the Washington, D.C. draft ozone SIP.3 

8.2.1 Episode Selection 

Since it would be impractical to model every violation day, EPA has traditionally recommended 

targeting a select group of episode days for ozone attainment demonstrations. Such episode days 

should be (1) meteorologically representative of typical high ozone exceedance days in the 

domain, and (2) so severe that any control strategies predicted to attain the ozone NAAQS for 

that episode day would also result in attainment for all other exceedance days. 

While EPA’s suggested approach is perhaps feasible for isolated urban areas, such an approach 

is impractical in this case given the spatial extent of the regional ozone problem in the Northeast 

and the resulting size of the modeling domain. Also, selection of episodes from different years 

would require the generation of multiple meteorological fields and emissions databases, which 

would be an extremely difficult proposition given the modeling domain. 

Recent experience has shown that model performance evaluations and the response to emissions 

controls need to include consideration of modeling results from longer time periods, in particular 

 

1 The Nature of the Ozone Air Quality Problem in the Ozone Transport Region: A Conceptual Description

(NESCAUM, October 2006). 

2

 Modeling documentation prepared by NYSDEC is housed at: 

http://www.otcair.org/projects_details.asp?FID=101&fview=modeling. 3

 The draft Washington D.C. ozone SIP is located at: http://sharepoint.mwcog.org/airquality/default.aspx.
8 - 4 

full synoptic cycles or even full ozone seasons. The 2002 ozone season had a significant number 

of exceedance days spread over numerous ozone episodes. As a result, the OTC Modeling 

Committee decided to investigate the appropriateness of modeling the entire 5-month 2002 

ozone season with the OTC SIP Quality Modeling System. Results of that investigation, 

documented in a contractor report included as Appendix 8B,4

 demonstrate that 2002 episode 

days are (1) meteorologically representative of typical high ozone exceedance days in the 

domain, and (2) so severe that control strategies predicted to attain the ozone NAAQS for those 

episode days would likely also result in attainment for all other exceedance days. The total 

number of days examined for the complete ozone season far exceeds EPA recommendations and 

provides for better assessment of the simulated pollutant fields. 

8.2.2 Modeling Domain 

In defining the modeling domain, the following parameters should all be considered: location of 

local urban areas; the downwind extent of elevated ozone levels; the location of large emission 

sources; the availability of meteorological and air quality data; and available computer resources. 

In addition to the nonattainment areas of concern, the modeling domain should encompass 

enough of the surrounding area such that major upwind sources fall within the domain and 

emissions produced in the nonattainment areas remain within the domain throughout the day. 

The areal extent of the OTR modeling domain (see Figure 8.2.2.1) is identical to the national 

grid adopted by the regional haze Regional Planning Organizations (RPOs), with a more refined 

“eastern modeling domain” focused on the eastern US and southeastern Canada. The placement 

of the eastern modeling domain was selected such that the northeastern areas of Maine are 

included. Based upon the existing computer resources, the southern and western boundaries of 

the imbedded region were limited to the area shown in Figure 8.2.2.1. 

Figure 8.2.2.1: Modeling Domain Used for OTR Modeling 

 

4 “Determination of Representativeness of 2002 Ozone Season for Ozone Transport Region SIP Modeling,” 

ENVIRON, prepared for OTC, June 2005. (Report is contained in Appendix 8B.) 
8 - 5 

8.2.3 Horizontal Grid Size 

As shown in Figure 8.2.1.1, the larger RPO national domain utilized a coarse grid with a 36-km 

horizontal grid resolution. The imbedded eastern modeling domain used a grid resolution of 12 

km, resulting in 172 grids in both the east-west and north-south directions. More detailed 

descriptions regarding grid configurations are provided in Appendix 8C. 

8.2.4 Vertical Resolution 

The vertical structure of the air quality model is primarily defined by the vertical grid used in the 

meteorological modeling, which used a terrain-following coordinate system defined by pressure 

to create a total of 29 layers. The layer-averaging scheme adopted for the air quality modeling is 

designed to reduce the computational cost of the simulations, resulting in incorporation of 22 

layers in the vertical, of which the lower 16 layers (approximately 3 km) coincide with those of 

the meteorological model. Layer averaging has a relatively minor effect on the model 

performance metrics when compared to ambient monitoring data. Appendix 8C contains the 

vertical layer definitions for the meteorological and air quality modeling domains. 

8.2.5 Initial and Boundary Conditions 

The objective of a photochemical grid model is to estimate the air quality given a set of 

meteorological and emissions conditions. When initializing a modeling simulation, the exact 

concentration fields are unknown in every grid cell for the start time. Therefore, photochemical 

grid models are typically started with clean conditions within the domain and allowed to stabilize 

before the period of interest is simulated. In practice this is accomplished by starting the model 

several days prior to the period of interest. For this application, the air quality modeling for 2002 

began May 1, with the first 15 days assumed to be ramp-up days not used for performance 

evaluation or prediction purposes. 

The winds move pollutants into, out of, and within the domain. The model handles the 

movement of pollutants within the domain and out of the domain. An estimate of the quantity of 

pollutants moving into the domain is needed. These are called boundary conditions. To estimate 

the boundary conditions for the modeling study, three-hourly boundary conditions for the outer 

36-km domain were derived from an annual model run performed by researchers at Harvard 

University using the GEOS-Chem global chemistry transport model. The influence of boundary 

conditions was minimized by the 15-day ramp-up period, which is sufficient to establish 

pollutant levels that are encountered in the beginning of the ozone episode. 

8.2.6 Meteorological Model Selection and Configuration 

The Pennsylvania State University/National Center for Atmospheric Research (PSU/NCAR) 

Mesoscale Meteorological Model (MM5) was selected to produce meteorological data fields for 

the modeling analysis. MM5 is a non-hydrostatic, prognostic meteorological model routinely 

used for urban-scale and regional-scale photochemical regulatory modeling studies. Based on 

model validation and sensitivity testing, the MM5 configurations provided in Appendix 8D were 
8 - 6 

selected. Results of the NYSDEC’s detailed performance evaluation of the MM5 modeling used 

in conjunction with the OTC platform are provided in Appendices 8E and 8F.

8.2.7 Emissions Inventory and Model Selection and Configuration 

Significant regional coordination was required to assemble the emission inventories needed to 

produce the emission data fields required for the modeling analysis. Recognizing the need for 

developing multi-pollutant inventories across many states to support both ozone and fineparticulate SIP modeling requirements, the Northeast and Mid-Atlantic states agreed to combine 

efforts under the MANE-VU RPO umbrella to compile base year and future year emission 

estimates for all required pollutants into a common format. The states were joined in the 

inventory development effort by MARAMA, OTC and NESCAUM. 

Modeling inventories for the MANE-VU region were prepared, with the assistance of 

contractors, for the 2002 base year and the projection years of 2009 and 2012. The base year 

inventory was compiled using 2002 inventory estimates provided by the states. Projection year 

inventories account for any expected changes in economic activity as well the implementation of 

control strategies occurring after 2002. Inventories for adjacent areas outside the MANE-VU 

region were obtained from the corresponding RPOs. Detailed descriptions of the inventories are 

provided in Appendices 8G, 8H and 8I. 

The Sparse Matrix Operator Kernel Emissions (SMOKE, Version 2.1) Emissions Processing 

System was used for pollutant speciation and for allocating annual county-level emissions from 

the regional inventory to grid cells on an hourly basis. Detailed descriptions of SMOKE 

processing are included in Appendices 8J and 8K. 

8.2.8 Air Quality Model Selection and Configuration

EPA’s Models-3/Community Multi-scale Air Quality (CMAQ) modeling system was selected 

for the attainment demonstration primarily because it is a “one-atmosphere” photochemical grid 

model capable of addressing ozone at regional scale. EPA considers CMAQ to be one of the 

preferred models for regulatory modeling applications, citing the model in its ozone modeling 

guidance.5

 The CMAQ configuration is provided in Appendix 8L.

8.2.9 Quality Assurance 

All air quality, emissions, and meteorological data were reviewed to ensure completeness, 

accuracy, and consistency before proceeding with modeling. Any errors, missing data or 

inconsistencies were addressed using appropriate methods that are consistent with standard 

practices. All modeling was benchmarked at each of the OTC modeling centers through the 

duplication of a set of standard modeling results. 

 

5

 Guidance on the Use of Models and Other Analyses for Demonstrating Attainment of Air Quality Goals for Ozone, 

PM2.5, and Regional Haze; EPA OAQPS; EPA-454/B-07-002; April 2007; See: 

http://www.epa.gov/scram001/guidance/guide/final-03-pm-rh-guidance.pdf. Hereinafter referred to as EPA 

Guidance (2007). 
8 - 7 

Quality assurance activities were carried out for the various emissions, meteorological, and 

photochemical modeling components of the modeling study. Emissions inventories obtained 

from the RPOs were examined to check for errors in the emissions estimates. When such errors 

were discovered, the problems in the input data files were corrected. 

The MM5 meteorological and CMAQ air quality model inputs and outputs were plotted and 

examined to ensure accurate representation of the observed data in the model-ready fields, and 

temporal and spatial consistency and reasonableness. Both MM5 and CMAQ underwent 

operational and scientific evaluations in order to facilitate the quality assurance review of the 

meteorological and air quality modeling procedures. 

8.3 Model Performance Evaluation 

There are many aspects of model performance. This section will focus primarily on the methods 

and techniques recommended by EPA for evaluating the performance of the air quality model. It 

should be noted that the other parts of the modeling process, the emissions and meteorology, 

underwent a similar evaluation. As mentioned in Section 8.2.6, the NYSDEC conducted an 

evaluation of the MM5 meteorological model (see Appendices 8E and 8F). The remainder of 

this section focuses on the air quality model evaluation. 

The first step in the modeling process is to verify the model’s performance in terms of its ability 

to predict the ozone in the right locations and at the right levels. To do this, model predictions 

for the base year simulation are compared to the ambient data observed in the historical episode. 

This verification is a combination of statistical and graphical evaluations. If the model appears 

to be producing ozone in the right locations for the right reasons, then the model can be used as a 

predictive tool to evaluate various control strategies and their effects on ozone. The purpose of 

the model performance evaluation is to assess how accurately the model predicts ozone levels 

observed in the historical episode. 

The results of the model performance evaluation were evaluated prior to commencing modeling 

in support of the attainment demonstration. The performance of CMAQ was evaluated using 

both operational and diagnostic methods. Operational evaluation refers to the model’s ability to 

replicate observed concentrations of ozone and/or precursors (surface and aloft), whereas 

diagnostic evaluation assesses the model’s accuracy with respect to characterizing the sensitivity 

of ozone to changes in emissions (i.e., relative response factors). 

The NYSDEC, Division of Air Resources, conducted a performance evaluation of the 2002 base 

case CMAQ simulation (May 15-September 30) on behalf of the OTC member States. Appendix 

8M provides comprehensive operational and diagnostic evaluation results. Highlights of this 

evaluation are provided in the following sub-sections. 

8.3.1 Diagnostic and Operational Evaluation 

The issue of model performance goals for ozone is an area of ongoing research and debate. To 

evaluate model performance, EPA recommends that several statistical metrics be developed for 

air quality modeling. Two of the common metrics that are most often used to assess 
8 - 8 

performance are the mean normalized gross error and the mean normalized bias. The mean 

normalized gross error (MNGE) parameter provides an overall assessment of model performance 

and can be interpreted as precision. The mean normalized bias parameter (MNB) measures a 

model's ability to reproduce observed spatial and temporal patterns and can be interpreted as 

accuracy. EPA suggests the following criteria: an MNB of < ±15%, and an MNGE of < 35% 

above a threshold of 40-60 ppb. These results are presented in Table 8.3.1.1 below for the local 

nonattainment areas and in Tables 8.3.1.2 and 8.3.1.3 on a monitor-by-monitor basis averaged 

over all days for the 40 ppb and 60 ppb thresholds, respectively. Figure 8.3.1.1 shows the 

location of the monitors.

Table 8.3.1.1 Southwest CT and Greater CT Statistics for 8-hour Ozone 

Location 

Ozone 

Cutoff 

Threshold 

(ppb)

Mean 

Normalized 

Gross Error 

(MNGE) 

(%)

Mean 

Normalized Bias 

(MNB) 

(%)

SW CT Portion of NY/NJ/CT Area 60 13.52 2.46 

Greater CT Area 60 19.13 14.2 

Table 8.3.1.2 Individual Site Statistics for 8-hour Ozone Using 40 ppb Cutoff

Monitor 

AIRS-ID 

Ozone 

Cutoff 

Threshold 

(ppb) Site Name County Area 

MNGE 

(%) 

MNB 

(%) 

0900100171 40 Greenwich Fairfield NY/NJ/CT 13.94 3.75 

0900111231 40 Danbury Fairfield NY/NJ/CT 15.35 -2.77 

0900130071 40 Stratford Fairfield NY/NJ/CT 15.8 -0.03 

0900190031 40 Westport Fairfield NY/NJ/CT 14.67 2.28 

0900700071 40 Middletown Middlesex NY/NJ/CT 13.31 2.28 

0900930021 40 Madison New Haven NY/NJ/CT 15.37 5.25 

0900990051 40 Hamden New Haven NY/NJ/CT 15.99 -0.67 

0900310031 40 East Hartford Hartford Greater CT 13.36 2.59 

0900500051 40 Cornwall Litchfield Greater CT 17.75 -12.6 

0901100081 40 Groton New London Greater CT 31.94 29.51 

0901310011 40 Stafford Tolland Greater CT 12.53 -4.67 
8 - 9 

Table 8.3.1.3. Individual Site Statistics for 8-hr Ozone using 60 ppb Cutoff

Monitor 

AIRS-ID 

Ozone 

Cutoff 

Threshold 

(ppb Site Name County Area 

MNGE 

(%) 

MNB 

(%) 

0900100171 60 Greenwich Fairfield NY/NJ/CT 13.78 0.31 

0900111231 60 Danbury Fairfield NY/NJ/CT 13.44 -8.74 

0900130071 60 Stratford Fairfield NY/NJ/CT 17.09 -0.05 

0900190031 60 Westport Fairfield NY/NJ/CT 12.18 -1.76 

0900700071 60 Middletown Middlesex NY/NJ/CT 10.66 -3.71 

0900930021 60 Madison New Haven NY/NJ/CT 14.54 1.67 

0900990051 60 Hamden New Haven NY/NJ/CT 12.95 -0.99 

0900310031 60 East Hartford Hartford Greater CT 13.83 2.25 

0900500051 60 Cornwall Litchfield Greater CT 20.17 -17.7 

0901100081 60 Groton New London Greater CT 30.34 28.1 

0901310011 60 Stafford Tolland Greater CT 12.18 -8.71 

Figure 8.3.1.1. Location of Ozone Monitors in the Vicinity of Connecticut 
8 - 10 

The base year performance evaluation indicates that CMAQ model meets EPA’s suggested 

criteria for the 40 ppb threshold at all Connecticut sites except Groton, where the MNB exceeds 

+/- 15% (+29.1%). EPA’s suggested criteria for the 60ppb threshold are met at all Connecticut 

sites except Groton and Cornwall, where the MNB exceeds +/- 15% (+28.1% and –17.7%, 

respectively). 

The following statistics for the OTC domain have also been provided in Appendix 8M: 

1. Archive file containing time series of 8-hour average observed and predicted ozone 

organized by state; 

2. Observed and predicted composite diurnal variations of selected species, including but 

not limited to ozone at State and Local Air Monitoring System and National Air 

Monitoring System (SLAMS/NAMS) sites, ozone at Clean Air Status and Trends 

Network (CASTNet) and other sites, VOC species such as ethene, isoprene, 

formaldehyde and gas phase compounds such as CO, NO and NO2; 

3. Statistical evaluation of daily maximum 8-hour ozone at SLAMS/NAMS sites and 

CASTNet/other sites. Statistics are computed using two different thresholds for observed 

daily maximum ozone - 40 and 60 ppb. Statistics are computed by date (all sites on a 

given day) and by site (one site over all days); 

4. Statistical evaluation of daily maximum 8-hour ozone at SLAMS/NAMS sites that fall 

within nonattainment counties. Statistics are computed by nonattainment area. 

5. Statistical evaluation of daily average CO, NO, NO2, and SO2 at SLAMS/NAMS and 

other sites Statistics are computed by date and by site); 

6. Statistical evaluation of daily average ethene, isoprene, and formaldehyde at 

SLAMS/NAMS and other sites (statistics are computed by date and by site); 

7. Plots of composite time series for daily max 8-hour ozone, root mean square error and 

mean bias for illustrative purposes; and 

8. Tile plots of daily 8-hour maximum predicted ozone across the modeling domain 

compared with actual observations. 

8.3.2 Summary of Model Performance 

CMAQ was employed to simulate ozone concentrations for the 2002 season (May 15 through 

September 30). A comparison of the temporal and spatial distributions of ozone and its 

precursors was conducted for the study domain with additional focus placed on performance in 

the NY/NJ/CT and Greater Connecticut areas.

The CMAQ model performance for surface ozone is quite good overall, with low bias and error. 

Model performance is generally consistent from day to day. The results for the 2002 ozone 

season show that the modeling system tends to over-predict minimum concentrations and slightly 

under-predict peak concentrations. The over-prediction of minimum concentrations is not of 

great regulatory concern since attainment tests are based on the application of relative response 

factors to daily peak concentrations. However, prediction of minimum concentrations is still 

important to appropriately model regional transport and nighttime ozone removal processes in 

order to accurately estimate peak concentrations. 
8 - 11 

The model performance for the Southwest Connecticut portion of the NY/NJ/CT area and the 

Greater Connecticut area averaged over all stations and all days meet the guidelines suggested by 

EPA. The criteria for acceptable model performance are met on most individual days as well. 

No significant differences in model performance for ozone and its precursors were encountered 

across the OTC. While there are some differences across sub-regions, there is nothing to suggest 

a tendency for the model to respond in a systematically different manner between regions. 

Examination of the statistical metrics by sub-region confirms the absence of significant 

performance problems arising in one area but not in another, building confidence that the CMAQ 

modeling system is operating consistently across the full OTC domain. 

Overall, the modeling system does a good job of appropriately estimating 8-hour average surface 

ozone throughout the OTR and in the Southwest Connecticut and Greater Connecticut areas. 

This confidence in the modeling results allows for the modeling system to be used to support the 

development of emissions control scenarios to meet the 8-hour ozone NAAQS. 

As stated previously, the model performance for the 2002 ozone season meets all EPA 

guidelines, demonstrating that the modeling platform is appropriate for modeling emissions 

controls scenarios for the 8-hour ozone SIP. However, it must be remembered that CMAQ has 

been evaluated by using measures that reflect its ability to represent average conditions instead 

of its ability to respond to changes in emissions. Thus, it is likely that although CMAQ has met 

the traditional performance measures set out in the EPA guidance, it may actually under-predict 

the magnitude of ozone changes due to various control measures being modeled. This means 

that future year modeling results should be viewed not in the traditional sense as being exact, but 

should be seen as an upper limit to anticipated ozone levels. This observation will be explored 

more fully as part of the weight-of-evidence discussion in Section 8.5. 

8.4 Attainment Demonstration Modeling (Note: The Hearing Report contains material that 

is supplemental to the information in Section 8.4.)

The CMAQ modeling analyzes the potential for the Greater Connecticut area and the Southwest 

Connecticut portion of the NY/NJ/CT area to achieve attainment of the 8-hour ozone standard. 

The attainment demonstration is based on both the CMAQ modeling results and a number of 

additional weight-of-evidence analyses (provided in Section 8.5) that support the attainment 

modeling results. Details of the CMAQ modeling are provided in the following sub-sections. 

8.4.1 Modeling Inventories 

As described in Section 8.2.1, CMAQ modeling runs were completed for the 2002 baseline year 

and 2009 and 2012 projection years using inventories developed as part of cooperative effort by 

the MANE-VU states to support ozone, PM2.5 and regional haze planning activities. Modeling 

results presented in this document are based on projected emissions representing the OTC’s 

“beyond-on-the-way” (BOTW) control scenario, which is comprised of the suite of measures 

each state indicated were likely to be adopted as of the commencement of modeling runs in late 

2006. A full description of the inventories is provided in Appendices 8G, 8H and 8I. 
8 - 12 

8.4.2 Modeled Attainment Test (MAT) 

Consistent with EPA’s guidance,6 CMAQ modeled results were applied in a relative sense, 

assuming that measured values from the baseline period would decrease in proportion to 

modeled improvements between the baseline and future projection years. This “modeled 

attainment test” (MAT) was applied at each monitor using the following equation: 

(DVF)I = (RRF)I (DVB)I (MAT Equation)

Where: 

(DVB)I = the baseline measured concentration at site I, in ppb 

(RRF)I = the relative response factor determined as the ratio of CMAQ modeled 

results between the future year and the baseline year, calculated near site I 

(DVF)I = the estimated future design value for the year of interest, in ppb. 

The development of appropriate relative response factors (RRF) and baseline concentrations 

(DVB) are described below. 

Development of Relative Response Factors

The RRF used in the MAT Equation is determined by taking the ratio of the mean of the 8-hour 

daily maximum predictions in the future to the mean of the 8-hour daily maximum predictions 

with baseline emissions, over all relevant days at each monitor location. Consistent with EPA’s 

recommendations,7 “relevant days” were determined on a monitor-by-monitor basis using all 

days in 2002 with a maximum measured 8-hour value of 85 ppb or higher. All monitors in 

Connecticut recorded more than 10 days during 2002 with 8-hour ozone exceedances, satisfying 

EPA’s criterion for using the 85 ppb threshold. 

Development of Baseline Concentrations 

As indicated by the MAT Equation, the DVB at each monitoring site serves as the reality-based 

“anchor point” for estimating future year projected concentrations. EPA’s modeling guidance8

lists the following attributes that should be reflected in the methodology selected to determine 

appropriate DVB values:

1) Should be consistent with the form of the applicable NAAQS; 

2) Should be easy to calculate; 

3) Should represent the baseline inventory year; 

4) Should take into account the year-to-year variability of meteorology; and 

5) Should take into account the year-to-year variability of emissions.

EPA’s guidance also recommends that DVB values be determined using the average of the three 

8-hour ozone design values that include the baseline inventory year. Accordingly, given a 

 

6

EPA Guidance (2007) at page 20. 

7

 Ibid. at page 147. 

8

 Ibid. at pages 22 and 23. 
8 - 13 

baseline inventory year of 2002, the years used to calculate the DVB would range from 2000-

2004. The resulting DVB calculation uses the 2000-2002, 2001-2003, and 2002-2004 design 

value periods, with the year 2002 “weighted” three times, 2001 and 2003 weighted twice each, 

and 2000 and 2004 weighted once each. EPA concludes that this default method has the desired 

effect of weighting the projected ozone values towards the middle year of the 5-year period (i.e., 

the 2002 baseline emissions year) while also taking into account the emissions and 

meteorological variability that occurs over the full 5-year period.

The guidance also notes that the default weighting procedure emphasizes the importance of the 

meteorology experienced during the middle years of the 5-year period. As a result, EPA 

recommends that meteorological data for the five years be evaluated to determine if any extreme 

conditions have occurred during the period, especially for the middle years that receive extra 

weighting in the recommended DVB methodology. 

CTDEP has conducted such an evaluation for the 2000 to 2004 ozone seasons. Figure 8.4.2.1 

shows the number of days with maximum temperatures of 90°F or more (90+°F) at Bradley 

Airport in north-central Connecticut, using EPA’s default 5-year weighting method. The 5-year 

period ending in 2004 (i.e., with 2002 weighted three times) had the highest weighted number of 

90+°F days for any 5-year period over the last 30 years (i.e., 20 days, tied with 2003). 

Figure 8.4.2.1

Number of Days with Maximum Temperature 90+°F

(5-Year EPA Weighted Average Method at BDL)

0

5

10

15

20

25

1979198019811982198319841985198619871988198919901991199219931994199519961997199819992000200120022003200420052006

End of 5-Year Period

EPA Wtd Avg # of Days 90+°F

30-Year Average = 17 Days 90+°F

Figure 8.4.2.2 focuses on temperatures for the middle years (i.e., 2001 through 2003) that 

straddle the 2002 baseline year and which served as the design value period for EPA’s 8-hour 

ozone nonattainment designations. The 3-year period ending in 2003 experienced the highest 

average number of days with temperatures of 90°F or higher over the 30-year period (i.e., 22 

days, compared to the long-term average of 17 days). 
8 - 14 

Figure 8.4.2.2

Number of Days with Maximum Temperatures 90+°F

(3-Year Running Average at BDL)

0

5

10

15

20

25

197719781979198019811982198319841985198619871988198919901991199219931994199519961997199819992000200120022003200420052006

End of 3-Year Period

Avg # of Days 90+°F

30-Year Average = 17 Days 90+°F

Based on this analysis, CTDEP concludes that EPA’s default DVB weighting method should not 

be used for Connecticut due to the “extreme” meteorological conditions occurring during the 

middle years of the 5-year period. Instead, CTDEP has determined that a DVB method based on 

a non-weighted 5-year average of ozone concentrations (using 2000 through 2004 4th-high ozone 

values) more appropriately represents summer temperatures in Connecticut. Figure 8.4.2.3 

illustrates this point, showing that, when simple 5-year averages of 90+°F days are analyzed, the 

5-year period ending in 2004 is very close to the 30-year average of 90+°F days (i.e., 16 days 

compared to the long-term average of 17 days). 

Figure 8.4.2.3

Number of Days with Maximum Temperatures 90+°F

(5-Year Running Average at BDL)

0.0

5.0

10.0

15.0

20.0

25.0

1979198019811982198319841985198619871988198919901991199219931994199519961997199819992000200120022003200420052006

End of 5-Year Period

Avg # of Days 90+°F

30-Year Average = 17 Days 90+°F
8 - 15 

8.4.3 Unmonitored Area Analysis 

The State of Connecticut’s monitoring network, laid over the 12 kilometer CMAQ modeling 

grid, is depicted in Figure 8.3.1.1. This dense network of monitors covers virtually the entire 

state when the nine CMAQ modeling grid squares encompassing each of the monitors are 

considered. Also, the densest portion of the network is along the coastline, where Connecticut’s 

nonattainment issues are the most problematic. Thus, the existing monitoring network is 

adequate to detect high ozone levels and an analysis of unmonitored areas is unnecessary. 

8.4.4 Results of the Modeled Attainment Test 

Projected ozone levels in 2009 and 2012 were determined using the MAT Equation, including 

RRF values developed from the CMAQ BOTW modeling and CTDEP’s DVb values determined 

as described above. Results are summarized in Table 8.4.4.1, with the DVf values representing 

the CMAQ projected 8-hour ozone levels, with BOTW controls, in 2009 or 2012. Results are 

also displayed in Figures 8.4.4.1 through 8.4.4.3, showing the rapid improvement in ozone levels 

over the period modeled. 

Table 8.4.4.1: CMAQ Modeling Results for Connecticut for 2009 and 2012 

 

2009 CTDEP 2009 2009 BOTW 2012 CTDEP 2012 2012 BOTW

DVb BOTW DVf DVb BOTW DVf 

Monitor (ppb) RRF (ppb) Monitor (ppb) RRF (ppb) 

 Greater CT Greater CT 

East Hartford 85.0 0.876 74 East Hartford 85.0 0.826 70 

Cornwall 83.5 0.870 72 Cornwall 83.5 0.818 68 

Groton 87.8 0.879 77 Groton 87.8 0.831 72 

Stafford 89.0 0.867 77 Stafford 89.0 0.814 72 

 Southwest CT Southwest CT 

Greenwich 91.8 0.913 83 Greenwich 91.8 0.874 80 

Danbury 93.2 0.897 83 Danbury 93.2 0.853 79 

Stratford 95.4 0.919 87 Stratford 95.4 0.878 83 

Westport 91.4 0.909 83 Westport 91.4 0.868 79 

Middletown 93.4 0.888 82 Middletown 93.4 0.839 78 

Madison 94.4 0.905 85 Madison 94.4 0.853 80 

Hamden 93.8 0.912 85 Hamden 93.8 0.874 81 
8 - 16 

Figure 8.4.4.1 

Figure 8.4.4.2 

Figure 8.4.4.3 
8 - 17 

8.4.5 Conclusions for the Greater Connecticut Area 

As displayed in Table 8.4.4.1, all four monitors located in the Greater Connecticut moderate 

nonattainment are projected by the CMAQ model to reach attainment of the 85 ppb 8-hour ozone 

NAAQS by 2009. Predicted 2009 ozone design values range from a high of 77 ppb in Groton 

and Stafford to a low of 72 ppb in Cornwall. All monitors are projected to have design values 

below the low-end threshold (i.e., 82 ppb) where EPA’s modeling guidance recommends the use 

of supplemental weight of evidence analyses to demonstrate attainment. Therefore, with CMAQ 

projected concentrations well below both the NAAQS and WOE range, CTDEP concludes that 

there is a high probability that the Greater Connecticut area will achieve attainment of the 8-hour 

ozone NAAQS by the end of the 2009 ozone season. Improvements are expected to continue 

beyond 2009, with the CMAQ model projecting 8-hour ozone levels of 72 ppb or lower in the 

Greater Connecticut area by 2012. 

8.4.6 Conclusions for the Southwest Connecticut Area 

The CMAQ modeling projects that four of the seven monitors located in the Southwest 

Connecticut portion of the NY/NJ/CT moderate nonattainment area will reach attainment levels 

by 2009. The model predicts that residual nonattainment will remain in 2009 at three mid-coast 

monitors: Stratford (87 ppb), Hamden (85 ppb) and Madison (85 ppb). Finally, the CMAQ 

modeling projects that attainment of the ozone NAAQS will occur throughout all of Southwest 

Connecticut sometime between 2009 and 2012, with a peak design value of 83 ppb predicted in 

Stratford in 2012. 

All seven Southwest Connecticut monitors are projected by the model to have 2009 design 

values within the “inconclusive” range (i.e., 82 ppb to 87 ppb) where EPA recommends the use 

of supplemental weight-of-evidence analysis techniques to better assess the probability of 

attaining by 2009. Several WOE analyses are presented in the following section. The results of 

these analyses lead CTDEP to conclude that there is a credible case for attainment throughout all 

of Southwest Connecticut by the end of the 2009 ozone season. 

8.5 Weight-of-Evidence Analysis (Note: The Hearing Report contains material that is 

supplemental to the information in Section 8.5.)

By definition, models are simplistic approximations of complex phenomena. It is generally 

recognized that there is significant uncertainty associated with the results of photochemical grid 

modeling. In addition to the uncertainties associated with the dispersion and chemical response 

mechanisms built into the air quality model, the required meteorological, baseline and projected 

emissions, and air quality input data sets also contain their own levels of uncertainty that can 

affect the performance of the modeling system. These uncertain aspects of the modeling 

analyses can sometimes prevent definitive assessments of future attainment status especially 

when projected pollutant levels are at levels close to air quality standards. 

Due to these uncertainties, modeling results should not be used in a strictly deterministic fashion 

to determine “bright-line” compliance by comparing projected air quality levels directly with the 

ozone NAAQS. Modeling is more appropriately used as a probabilistic tool, along with other 
8 - 18 

available assessment techniques, to assess the likelihood of complying with the NAAQS by a 

certain deadline. Of course, a properly performing model which projects air quality in an area to 

be well above, or well below, the level of the NAAQS may warrant greater consideration among 

the mix of available other assessments when determining the likelihood of compliance. 

EPA addresses the modeling uncertainty issue in its modeling guidance,9

 recommending that 

WOE analyses be performed to better determine the likelihood of NAAQS compliance when the 

model attainment test results are “inconclusive”. EPA’s guidance establishes the “inconclusive” 

range for 8-hour ozone modeling as MAT results between 82 ppb and 87 ppb for the required 

attainment year. As described above in Section 8.4, 2009 CMAQ MAT results for the Greater 

Connecticut area are well below this “inconclusive” range, providing a high degree of confidence 

that Greater Connecticut area will comply with the NAAQS by 2009. CMAQ MAT results for 

the Southwest Connecticut area fall within the “inconclusive” range, warranting consideration of 

other evidence to assess the probability of attaining in that area by 2009. Therefore, the focus of 

the WOE study is on the Southwest Connecticut area. 

Several topics are included in the WOE discussion that follows below, including modeling 

uncertainties, air quality trends, comparison of modeled and monitored ozone levels, additional 

emission reductions not included in the CMAQ modeling and other important considerations. 

8.5.1 Modeling Uncertainties Indicate the CMAQ Model May Overpredict 2009 Ozone 

Levels 

Several contributors to modeling uncertainty may result in overestimation by CMAQ of 

projected 2009 design values. These include the inadequate incorporation by the modeling 

system of NOX emissions occurring during high electric demand days (HEDD), potential 

problems with the model’s treatment of aloft transport and difficulties simulating marine 

boundary layer and sea breeze effects. 

8.5.1.1 Modeling Uncertainty Related to HEDD Emissions 

Emissions from the electricity generating source sector vary widely both diurnally and on a dayto-day basis, dependent upon the demand for electricity and the emission characteristics of the 

mix of electric generating units (EGUs) dispatched to meet changing demand and reserve 

capacity requirements. The highest level of EGU emissions typically occur on hot summer days, 

when the demand for air conditioning results in dispatch of load-following and quick-start EGU 

peaking units, most of which emit NOX at much higher rates (per unit of heat input or power 

output) than base-load units. Unfortunately, these HEDD emissions often occur during the 

meteorological conditions most conducive to producing the highest levels of ozone. For 

Connecticut, the most favorable meteorological conditions for ozone production include high 

temperatures on sunny summer days, with lower level transport winds from the southwest and 

upper level transport winds from the west, regions rich with emissions from EGUs and other 

source categories.

 

9

 Guidance on the Use of Models and Other Analyses for Demonstrating Attainment of Air Quality Goals for Ozone, 

PM2.5, and Regional Haze; EPA OAQPS; EPA-454/B-07-002; April 2007; See page 98 of: 

http://www.epa.gov/scram001/guidance/guide/final-03-pm-rh-guidance.pdf. 
8 - 19 

The variability of EGU emission profiles in New England is depicted in Figure 8.5.1.1, which 

shows that daily EGU NOX emissions in New England on high ozone days can be more than 

twice what they are on low ozone days (e.g., 260 tons on Aug 14, 2002 compared to 130 tons on 

Aug 8, 2002). In Figure 8.5.1.2, similar variations in emissions are seen upwind from 

Connecticut in the metropolitan New York City-New Jersey area, with more than double the 

emissions on high ozone days compared to New England (i.e., maximum 590 tons in the NYC 

metro area compared to a maximum of 260 tons in New England). These New York City-New 

Jersey sources impact the key monitors along the southern and western boundaries of 

Connecticut. 

Figure 8.5.1.1 Daily NOX emissions from EGUs in New England 

Daily NOx Emission from EGUs in New England 

(June 1, 2002 - September 15, 2002)

0.0

50.0

100.0

150.0

200.0

250.0

300.0

1-Jun

3-Jun

5-Jun

7-Jun

9-Jun

11-Jun13-Jun

15-Jun

17-Jun19-Jun

21-Jun23-Jun

25-Jun

27-Jun

29-Jun

1-Jul

3-Jul

5-Jul

7-Jul

9-Jul

11-Jul

13-Jul15-Jul17-Jul

19-Jul21-Jul

23-Jul

25-Jul

27-Jul29-Jul

31-Jul

2-Aug

4-Aug

6-Aug8-Aug

10-Aug

12-Aug

14-Aug

16-Aug

18-Aug

20-Aug

22-Aug

24-Aug

26-Aug

28-Aug

30-Aug

1-Sep

3-Sep

5-Sep7-Sep

9-Sep

11-Sep

13-Sep

15-Sep

NOx Emissions from EGUs in New England (tons

Figure 8.5.1.2
8 - 20 

The CMAQ modeling system is not structured to capture the large day-to-day variability that 

occurs in actual EGU NOX emissions. Due to limitations in projecting temporal and spatial 

distributions of future EGU dispatch, EGUs are simulated by the modeling system using uniform 

NOX hourly profiles that vary only by month of the year and by day of the week, with no 

distinction made between the highest demand and lowest demand days. The difference between 

actual and modeled emissions is depicted in the example provided in Figure 8.5.1.3. Modeled 

emissions for Hudson County, New Jersey follow a day-of-week repeating profile for August 

2002. Note that modeled August 6 emissions of 37 tons are repeated one week later, on August 

13, in accordance with the day-of-week profile. Meanwhile, actual emissions vary considerably 

throughout the week depending on electricity demand, with the highest demand days producing 

NOX emissions almost twice those that were modeled. Ozone levels on August 13, 2002 were 

among the highest that year in Connecticut, with five of the state’s eleven monitors measuring 8-

hour values in excess of 120 ppb. 

Figure 8.5.1.3 Comparison of Actual and Modeled EGU Emissions for Hudson County, NJ 

37 36 34

31

25 24

33

37

71

47

54

69

37 35 36

32

0

20

40

60

80

100

6-Aug 7-Aug 8-Aug 9-Aug 10-Aug 11-Aug 12-Aug 13-Aug

NOX Emissions (Tons)

State Specific

Unit Specific

This large (i.e., factor of two) underestimate of EGU NOX emissions on high demand days has 

implications for CMAQ modeling results in both the baseline and future year modeling 

scenarios. Effectively doubling modeled levels of EGU emissions on high demand days (which 

are often high ozone days) increases the importance of the EGU sector relative to other source 

categories. As a result, post-2002 controls on the EGU sector, such as the CAIR program and 

potential HEDD strategies, may result in greater improvements in actual future year ozone levels 

than the current modeling results indicate. 

 Modeled Emissions

 Actual Emissions
8 - 21 

8.5.1.2 Modeling Uncertainty Related to CMAQ’s Response to Emission Reductions 

Two recent real-world examples provide an opportunity for assessing the capabilities of the 

CMAQ modeling system to properly respond to emission changes, especially from elevated 

EGU emission sources that are known to contribute significantly to ozone transport: 

• 2003 Northeast Power Blackout; and 

• Implementation of EPA’s NOX SIP Call. 

Detailed descriptions of these events have been developed by the State of Maryland, as presented 

in that state’s ozone SIP.10 Much of the related analyses are based on aircraft measurements of 

meteorological and pollutant parameters conducted by the University of Maryland along the 

eastern seaboard during the 2002 and 2003 ozone seasons (including the 2003 Northeast 

blackout period), as well as subsequent attempts to simulate each event with the CMAQ model. 

The summaries provided below are based on the descriptions provided in Maryland’s attainment 

demonstration. 

In both of these real-world cases, comparison of actual ozone reductions to CMAQ modeling 

results reveals that the CMAQ model underpredicted the level of measured ozone improvement 

associated with reductions in EGU emissions, possibly due to model problems with the 

simulation of elevated transport. These findings reinforce the possibility that post-2002 EGU 

reductions from the CAIR program and potential HEDD strategies may result in greater 

improvements in actual 2009 year ozone levels than indicated by the modeling results described 

in Section 8.4.5. 

2003 Northeast Power Blackout

Shortly after 4 p.m. eastern daylight time on August 14, 2003, a chain reaction triggered the 

shutdown of much of the generating capacity in the northeastern U.S. and southeastern Canada. 

This largest single electricity outage in North American history affected an estimated 50 million 

people, with 61,800 megawatts (MW) of electrical load lost in parts of Ohio, Michigan, New 

York, Pennsylvania, New Jersey, Connecticut, Massachusetts, Vermont and the province of 

Ontario. Many units shut down completely at the start of the blackout, with maximum impact 

reached a short time later, resulting in 531 units at 263 power plants being shut down. Most of 

these units remained shut down for 24 hours or more. 

Although many ground-based ozone monitoring stations were without electricity, the University 

of Maryland instrumented aircraft flew that day based on a forecast for high ozone. Airborne 

measurements were taken over Maryland and Virginia (outside the blackout area) and 

Pennsylvania (in the center of the area affected by the blackout) on August 15, 2003, 24 hours 

into the blackout. The data from these flights provided a rare opportunity to test the response of 

air quality models to a large, sudden drop in emissions. 

 

10 “Baltimore Nonattainment Area 8-Hour Ozone State Implementation Plan and Base Year Inventory”; 

SIP Number: 07-04; June 15, 2007; See: http://www.mde.state.md.us/Programs/AirPrograms/air_planning/index.asp. In particular, 

see Appendices G1, G8, G-9, and G-10 of the Maryland SIP. 
8 - 22 

Airborne measurements collected during the blackout show that ozone was 30 ppb lower 

throughout the lowest 1.5 km of the atmosphere and 38 ppb lower at ground level on that day, 

compared to measurements on a meteorologically similar day, August 4, 2002.11 Comparison to 

another day (August 3, 2005) that may have been even more similar to the blackout day, 

especially in regards to transport, found smaller differences in ozone, around 7 ppb. It is 

important to note that the August 3, 2005 flight occurred after the significant EGU NOX

reductions from the NOX SIP Call were implemented, which likely explains the smaller 

differences when compared to the blackout measurements.

The only identified CMAQ modeling study of the 2003 blackout event12 estimated that the 

blackout resulted in only 2.2 ppb of ozone reduction, far less than the 7 ppb to 38 ppb response 

determined by either of the above observation-based methods. These comparisons suggest that 

the model is not appropriately capturing the response in ozone due to changes in power plant 

emissions. 

EPA’s NOX SIP Call

EPA, in collaboration with researchers from several universities, is performing a CMAQ 

simulation of 2002 and 2004 summertime air quality to determine the benefits of the NOX SIP 

Call.13 The NOX SIP Call provided a large reduction in NOX emissions over a relatively short 

period of time, providing an opportunity to assess the performance of the CMAQ modeling 

system. 

The final manuscript has not yet been released, but preliminary results indicate that, although 

observed median 8-hour ozone levels improved by about 18 ppb during the 2002 to 2004 period, 

the CMAQ model only simulated a change of 8 ppb. If these results are not explained by other 

factors, they would suggest that the CMAQ model may underpredict changes in ozone, 

especially from reductions in sources of elevated NOX emissions that contribute to transport. 

The 2003 Northeast Blackout studies and EPA’s NOX SIP Call analysis highlight an apparent 

“stiffness” of the CMAQ model in properly responding to elevated NOX reductions. This 

suggests that the 2009 CMAQ predictions presented in Section 8.4 may be too high, not 

adequately accounting for the level of ozone improvements that can be expected from control 

programs such as CAIR. These findings also provide hope that the HEDD reductions being 

pursued by several Northeast states (including Connecticut) will provide significant additional 

ozone reductions that have not been reflected in the modeling results. 

 

11 Marufu,L.T., B. F. Taubman, B. Bloomer, C. A. Piety, B. G. Doddridge, J. W. Stehr, and R. R. Dickerson; 

 “The 2003 North American electrical blackout: An Accidental Experiment in Atmospheric Chemistry”; 

Geophysical Research Letters; Vol. 33, L22810, doi:10.1029/2006GL027252, 2006.. 12 Hu, Y. M. T. Odman, and A. G. Russell; “Re-examination of the 2003 North American electrical blackout impacts 

on regional air quality”, Geophysical Research Letters, Vol. 33, L22810, doi:10.1029/2006GL027252, 2006. 13 Gilliland et al; manuscript in preparation, 2007. 
8 - 23 

8.5.1.3 Modeling Uncertainty Related to Sea Breeze Circulations 

A sea breeze typically forms along coastlines during afternoons when the land is considerably 

hotter than the adjacent ocean or bay. The difference in temperature between the land and 

adjacent water body results in a pressure difference that drives the air circulation. Air flows 

from the high pressure over the ocean toward the low pressure over land. At night, the opposite 

may happen as the land cools below the ocean’s temperature, and a land breeze blows out to sea. 

Because the nighttime land and water temperature differences are usually much smaller than in 

the day, the land breeze is weaker than the sea breeze. Sea breezes typically only penetrate a few 

kilometers inland because they are driven by temperature contrasts that disappear inland. 

The coastal sea breeze can be an important ozone transport mechanism, sweeping ashore 

pollutants originally transported over the ocean parallel to the coastline. Ozone moving over 

water is, like ozone aloft, isolated from destructive forces. When ozone gets transported into 

coastal regions by sea breezes, it can arrive highly concentrated. Conversely, when the offshore 

air mass contains few pollutants, the sea breeze can draw clean marine air into coastal areas. 

Transport over the ocean is commonly observed downwind of the New York City metropolitan 

area during the summer months due the city’s proximity to the Atlantic Ocean and the Long 

Island Sound. The relatively cool summertime waters of Long Island Sound limit vertical 

mixing and deposition of ozone, often resulting in a concentrated ozone plume just offshore that 

is fueled by upwind emission sources located southwest of Connecticut. On days when a sea 

breeze forms in the afternoon, the shift in wind can bring high ozone concentrations to 

Connecticut’s coastal monitors. Given the small temporal and spatial scale of sea breeze effects, 

the CMAQ model is challenged to resolve this feature, thus introducing a significant level of 

uncertainly to projections at the coastal Connecticut sites. Furthermore, since the emissions 

contained in the offshore plume do not originate from CT sources, in-state reductions have little 

effect on coastal concentrations affected by the sea breeze. This further emphasizes the 

importance of upwind reductions to reach attainment in coastal Connecticut. 

The sea breeze effect along Connecticut’s coastline is depicted in the four pollution rose plots 

presented in Figure 8.5.1.3.1. These pollution roses represent the frequency of wind direction on 

the highest 10 percentile ozone concentration days from April 1 to October 31 during the years 

1997 to 2005.14 The winds on the highest ozone days point at the New York City metropolitan 

area at all locations along the Connecticut shoreline. Going along the Connecticut shoreline from 

the west (i.e. Greenwich) to the east (i.e., Groton), the predominant wind frequency direction 

(noted in red) shifts increasingly to the west, tracking the upwind location of the New York City 

metropolitan area. 

This analysis suggests that most high ozone events in coastal Connecticut are caused by 

emissions transported from upwind areas, rather than by in-state emissions. To the extent that 

any coastal nonattainment issues remain after 2009, additional upwind reductions will be 

necessary to achieve compliance. 

 

14 “The Nature of the Ozone Air Quality Problem in the Ozone Transport Region: A Conceptual Description”; 

NESCAUM; October 2006; See http://bronze.nescaum.org/committees/attainment/conceptual/. 
8 - 24 

Figure 8.5.1.3.1 Wind rose plots along Connecticut shoreline for the time period April 1 to 

October 31 during the years 1997 through 2005 

Each plot shows frequency 

of high ozone increases as 

the wind points up LIS 

towards emission -rich areas 

of the Northeast corridor.

8.5.2 Air Quality Trends Indicate the CMAQ Model May Overpredict 2009 Ozone Levels 

Emission reduction programs implemented over the last 25 years have resulted in significant 

decreases in peak ozone levels in Connecticut. The control strategies included in this SIP 

revision will continue to advance that progress. The following subsections briefly review the 

progress that has been made to date (see Section 3 for a more complete discussion) and examine 

how well the CMAQ model captures the progress that has been made since 2002, the baseline 

year used in the modeling analysis. 

8.5.2.1 Air Quality Trends Suggest Southwest Connecticut is on Track for Attainment 

As previously described in Section 3, measured levels of ozone and ozone precursor have 

dramatically decreased in Connecticut over the last 25 years. Figure 8.5.2.1 depicts the 

substantial reductions in 8-hour ozone design values that have occurred over that period at all 

monitors in the Southwest Connecticut Area.
8 - 25 

Figure 8.5.2.1 Trends in 8-Hour Ozone Design Values

for the SWCT Area

0

20

40

60

80

100

120

140

160

198119831985198719891991199319951997199920012003200520072009

Ozone Design Value (ppb)

Danbury Greenwich

New Haven Madison

Middletown Stratford

Westport 8-hour Ozone NAAQS

New Haven ozone measured at 3 locations.

1) 1983-1997 - State Street

2) 1999-2003 - Hamden

3) 2004-Present - Criscuolo Park 

The decline in peak ozone levels is apparent even when year-to-year summertime temperature 

fluctuations are considered. Figure 8.5.2.2 depicts the ratio of ozone exceedance days to the 

number of days with maximum temperatures of 90°F or more in Connecticut for the period from 

1975 through 2006. There were 2.2 to 8 times more exceedance days than hot days during the 

first ten years of the period (1975 to 1985). Ratios subsequently decreased to levels ranging 

from one to three exceedance days per each hot day through the 1990s. Most recently, the ratio 

has declined to one exceedance day or less per hot day since 2002. In 2006, the ratio was 0.81, 

with 13 exceedance days versus 16 hot days during the ozone season. 

Figure 8.5.2.2: Connecticut Statewide 8-Hour Ozone Standard

Ratio of "Unhealthy" to "Hot" Days through 2006

0.0

1.0

2.0

3.0

4.0

5.0

6.0

7.0

8.0

9.0

19751976197719781979198019811982198319841985198619871988198919901991199219931994199519961997199819992000200120022003200420052006

Ratio

Ratio 8-hr Exc Days : Days >=90 Deg. F (BDL)
8 - 26 

These improvements in ozone levels have resulted from continuing reductions in ozone precursor 

emissions in Connecticut, throughout the OTR and elsewhere. As is more fully described in 

Section 4.3, control programs included in Connecticut’s RFP demonstration are projected to 

result in 25% reductions in anthropogenic VOC emissions and 31% reduction in anthropogenic 

NOX emissions between 2002 and 2009, with considerable additional reductions projected 

through 2012 and beyond. 

The dramatic improvement in ozone levels since 1985 in the Northeast is displayed in a series of 

isopleth maps provided in Appendix 8N. The plots show the progressive reduction in both the 

magnitude and spatial extent of high ozone levels as the ozone plume has “retreated” towards the 

southwest due to the success of emission control programs. 

Finally, improvements in measured ozone levels suggest that Southwest Connecticut is on-track 

to achieve the necessary design value of less than 85 ppb to attain the 8-hour NAAQS by the end 

of the 2009 ozone season. Actual rate-of-progress towards the attainment goal is summarized in 

Figure 8.5.2.3. EPA used the 2003 design value of 102 ppb, measured at Stratford and Madison, 

Connecticut to classify the NY/NJ/CT area as moderate nonattainment for the 8-hour ozone 

NAAQS. Assuming improvements are achieved at an even rate over the 6-year period from 

2003 to 2009, ozone levels would need to decline by 3 ppb per year to achieve attainment by 

2009. Over the 3-year period from 2003 to 2006, this would require an improvement of 9 ppb, 

corresponding to a 2006 design value goal of 93 ppb. The highest measured design value in 

2006 was 92 ppb, suggesting the Southwest Connecticut area is on-target for attainment in 2009. 

Figure 8.5.2.3 Measured Improvement in Design Values Compared to Rate-of-Progress 

Needed to be On-Target for 2009 Attainment 

 1) Base Year (2003): Design Value = 102 ppb (measured in Stratford and Madison, CT) 

 2) Target Year (2009) Goal: Design Value ≤ 85 ppb 

 3) Desired Rate-of-Progress to Meet Target (assumes even rate): 

 2009 – 2003 = 6 years 

 102 ppb - 84 ppb = 18 ppb 

 18 ppb ⁄ 6 years = 3 ppb ⁄ year 

 4) Goal for 2006: 

 2006-2003 = 3 years 

 3 ppb ⁄year x 3 years = 9 ppb (ozone improvement goal) 

 102 ppb - 9 ppb = 93 ppb (ozone design value goal for 2006) 

 5) Status for 2006: Highest measured design value = 92 ppb (measured in Danbury, CT) 

 6) Conclusion: On-target for attainment in 2009 
8 - 27 

8.5.2.2 Ozone Improvements Outpace CMAQ Modeled Projections at Key Monitors 

As previously described in Section 8.4.3, CMAQ modeling for 2009 projects that only the 

Stratford, Madison and Hamden monitors in Southwest Connecticut will have design values 

exceeding the 85 ppb 8-hour ozone NAAQS. Model projections for the other four Southwest 

Connecticut monitors (and all four Greater Connecticut monitors) are below the level of the 

NAAQS in 2009. 

Measured 2006 design values provide a means to assess how well the CMAQ model is 

performing relative to actual measured ozone levels. Table 8.5.2.2.1 compares actual measured 

2006 design values to 2006 interpolated CMAQ modeling results at the key monitoring sites in 

Southwest Connecticut. The 2006 modeled values were determined by linearly interpolating 

between the 2002-era baseline design values (DVb) used as the anchor point in the modeling 

analysis and the CMAQ-modeled 2009 BOTW results. 

Table 8.5.2.2.1 Comparison of 2006 Actual Design Values to CMAQ Interpolated Results

CTDEP 

DVb 

2009 

CMAQ 

BOTW 

DVf 

Interpolated 

2006 

CMAQ DV 

Actual 

2006 

DV 

Are Measured 

Design Values 

Ahead or Behind 

Key SWCT 

Monitors 

(ppb) (ppb) (ppb) (ppb) Model Predictions? 

Stratford 95.4 87.7 91.0 88 Ahead 

Madison 94.4 85.4 89.3 88 Ahead 

Hamden 93.8 85.5 89.1 na na 

Danbury 93.2 83.6 87.7 92 Behind 

 na – not applicable (The Hamden monitor was moved to New Haven in 2004. The 2006 design value in New 

Haven was 77 ppb.) 

For the two key monitors at Stratford and Madison, actual 2006 design values are somewhat 

ahead of the interpolated CMAQ results for 2006. Stratford’s monitored 2006 design value is 88 

ppb, while linear interpolation between the 2002 modeling design concentration and the 2009 

CMAQ modeling results yields a “modeled” 2006 value of 91 ppb. Similarly, the actual 2006 

design value for Madison is 88 ppb, while the interpolated CMAQ results produce a “modeled” 

2006 value of 89 ppb. If these differences carry forward to 2009, Stratford’s 2009 modeled 

value of 87 ppb would translate to a possible 2009 design value of 84 ppb and Madison’s 

modeled value of 85 ppb would translate to a possible 2009 design value of 84 ppb, both in 

compliance with the 8-hour ozone NAAQS of 85 ppb. Note that the Hamden ozone monitor was 

moved to New Haven in 2004, so a similar comparison cannot be made for that site. The 2006 

design value at the New Haven site was 77 ppb, in compliance with the ozone NAAQS. 

 
8 - 28 

These findings are somewhat consistent with those observed in New Jersey, where all monitored 

design values in 2006 have already reached CMAQ modeled values for 2009. However, one 

monitor in Southwest Connecticut, located in Danbury, appears to be significantly behind the 

design value that might be anticipated by the CMAQ modeling. Danbury’s 2006 design value, 

92 ppb, is about 4 ppb greater than the interpolated CMAQ value of 88 ppb for 2006, raising 

doubts that the CMAQ predicted 2009 design value of 83 ppb will actually be realized at that 

site. It is worth noting that Danbury’s measured 2006 design value of 92 ppb is comprised of 

fourth-high concentrations of 86 ppb in 2004, 104 ppb in 2005, and 87 ppb in 2006. The 104 

ppb value from 2005 dominates the three-year design value average. The summer of 2005 

experienced 29 days of 90°F or higher temperatures, the 5th hottest summer in the last 30 years. 

As discussed further in the following subsection, ozone levels have improved to the point that the 

prospect for attainment in 2009 in Southwest Connecticut is strongly tied to the meteorological 

conditions that will occur during the summers of 2007, 2008 and 2009. 

8.5.3 Attainment Levels Have Been Achieved During A Previous Cool Summer 

The occurrence of one or more cool summers would increase the prospects of attaining the ozone 

standard in Southwest Connecticut by the end of 2009. For example, the 2004 summer 

experienced only 6 days with maximum temperatures of 90°F or higher (an average summer has 

17 days ≥ 90°F). As a result, all Connecticut ozone monitors, except for Danbury, recorded 4thhigh 8-hour ozone levels that were less than the 8-hour ozone NAAQS of 85 ppb. Note that 4thhigh values are used in the three-year design value calculation to determine NAAQS compliance. 

The Danbury 4th-high value in 2004 was 86 ppb, marginally greater than the standard. Emissions 

have decreased significantly since the 2004 ozone season, with a 20% reduction in ozone 

precursors expected between 2004 and 2009. Based on that level of emission reduction, if one or 

more of the summers of 2007, 2008 and 2009 are similar to, or even slightly warmer than the 

summer of 2004, compliance with the NAAQS could be achieved. 

8.5.4 “Clean Data” in 2009 would Qualify SWCT for Clean Air Act Extension Year(s) 

Section 181(a)(5) of the CAA provides a mechanism for states to apply to the EPA administrator 

for an extension of the attainment deadline: 

“Upon application by any State, the Administrator may extend for 1 additional year (hereinafter referred to 

as the "Extension Year") the date specified in table 1 of paragraph (1) of this subsection if- 

(A) the State has complied with all requirements and commitments pertaining to 

 the area in the applicable implementation plan, and 

(B) no more than 1 exceedance of the national ambient air quality standard level for 

 ozone has occurred in the area in the year preceding the Extension Year. 

No more than 2 one-year extensions may be issued under this paragraph for a single nonattainment area.”

The reference to “table 1” points to the classification categories and attainment dates specified by 

the CAA Amendments of 1990 for the now revoked 1-hour ozone NAAQS. Under the 1-hour 

NAAQS, compliance in a nonattainment area was determined based on a design value defined as 

the maximum recorded 4th-highest 1-hour concentration recorded at any monitor over the most 

recent three-year period (i.e., an average of one exceedance per year was allowed at a monitor). 
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Under the current 8-hour NAAQS, compliance in a nonattainment area is determined based on a 

design value defined as the average of the 4th-highest concentration recorded at a monitor each 

year over the most recent three-year period. This design value definition allows compliance to 

be achieved even with three or more exceedances of the 8-hour NAAQS in a given year, 

provided the three-year average of 4th-high values at each monitor is less than 85 ppb. 

Section 181(a)(5) of the CAA was written using the definitions of “design value” and 

“compliance” for the then applicable 1-hour ozone NAAQS and is not as easily interpreted in 

relation to the changed definitions of those terms for the 8-hour NAAQS. One reasonable 

interpretation for the 8-hour NAAQS would be that an area is eligible for a one-year extension of 

the attainment deadline if the maximum measured 4th-high concentration in the required 

attainment year (i.e., in this case, 2009) is less than 85 ppb. 

Based on this interpretation, and assuming that the nonattainment area does not have a 2009 

design value that fully complies with the NAAQS, Southwest Connecticut would be eligible for 

a one-year extension of the attainment deadline if the maximum recorded 4th-high concentration 

in 2009 at each monitor in the nonattainment area is less than 85 ppb. Section 181(a)(5) would 

also allow an additional extension year to achieve attainment, through 2011, if “clean data” were 

recorded throughout the nonattainment area in 2010. 

Section 181(b)(2) also exempts nonattainment areas that receive attainment deadline extensions 

from the “bump-up” provision of the CAA (emphasis added): 

“Reclassification upon failure to attain.- (A) Within 6 months following the applicable attainment date 

(including any extension thereof) for an ozone nonattainment area, the Administrator shall determine, 

based on the area's design value (as of the attainment date), whether the area attained the standard by that 

date. Except for any Severe or Extreme area, any area that the Administrator finds has not attained the 

standard by that date shall be reclassified by operation of law in accordance with table 1 of subsection (a) 

to the higher of- 

 (i) the next higher classification for the area, or 

 (ii) the classification applicable to the area's design value as determined at the time of the notice 

 required under subparagraph (B). 

No area shall be reclassified as Extreme under clause (ii).”

Based on the above discussion, Southwest Connecticut could reach attainment of the NAAQS in 

2011 and still comply with CAA requirements for moderate nonattainment areas. 

8.5.5 Modeling Does Not Include Several Important Emission Control Strategies

The CMAQ modeling conducted for the attainment demonstration does not account for several 

control strategies that are expected to provide additional emission reductions in the 2009 

timeframe, thereby increasing the likelihood that ozone levels in 2009 will be lower than the 

modeled levels reported in Section 8.4. The most important strategies, which are not at this time 

being proposed for inclusion in the ozone SIP, are summarized in Table 8.5.5.1 with discussion 

of some of the key Connecticut initiatives provided below. 
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Table 8.5.5 Additional Emission Control Strategies Not Included in the CMAQ 

Modeling 

Strategy Timing Comments 

High Electric Demand Day Reductions (HEDD) 2009 ozone 

season 

Northeast MOU in place; 

pursuing this initiative 

CT Energy Efficiency, Load Shifting & Clean 

Energy Programs 

Ongoing & 

Increasing 

CT Energy Bill of 2007 Programs 2008 Plans for peaking 

generation; 

Comprehensive plan for 

procurement of energy 

resources; 

Annual Assessment of 

energy capacity requirements, 

demand growth, 

environmental impacts, 

security and costs 

CT $1 Billion Commitment to Reduce Highway 

Congestion 

- Regional planning for commuter transport 

- Encourage port and rail freight use 

- Expand rail commuter service 

- Fuel cell study 

- Telecommuting/flexible employee 

scheduling 

2008 + Includes New HavenHartford-Springfield MA 

commuter rail line; other 

transit; telecommuting 

NYC Hybrid Taxi and Energy Efficiency 2007-2012 All hybrid taxi fleet by 2012 

OTC Auto Refinishing VOC Content Limits 2012 

(anticipated) 

Approximately 65% reduction 

in VOC emissions anticipated 

from the 2002 baseline for this 

sector. The requirements are 

now adopted in some 

California air quality districts. 

EPA National Measures 

- Aerosol Coatings 

- Consumer Products 

- Architectural Coatings (AIM) 

Group II VOC Control Technique Guidelines 

(CTGs) 

- Flexible package printing 

- Offset lithographic/letterpress printing 

- Industrial cleaning solvents 

Diesel Locomotives & Marine Diesel Engines 

Small Spark-Ignited Lawn & Garden and Marine 

Engines 

2009 

2009 

2009 

2009 

2009 starts 

phase-in 

Phase-in starts 

2009 Marine & 

2011 Nonroad 

Consumer products & AIM 

included in modeling only for 

OTR states. 

Rule amendment under 

development. 

Proposal published March 

2007 

Proposal published May 2007

NOX reductions from minor source asphalt 

production facilities 

2009-2010 State initiative under 

development 
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8.5.5.1 High Electric Demand Day (HEDD) 

As discussed in Section 8.5.1.1, emissions from the electricity generating source sector can vary 

widely on a day-to-day basis, depending upon the demand for electricity and the emission 

characteristics of the mix of electric generating units (EGUs) dispatched to meet changing 

demand and reserve capacity requirements. The highest levels of EGU emissions typically occur 

on hot summer days, when the demand for air conditioning results in dispatch of load-following 

and quick-start EGU peaking units, most of which emit NOX at much higher rates (per unit of 

heat input or power output) than base-load units. Unfortunately, these HEDD emissions often 

occur during the meteorological conditions most conducive to producing the highest levels of 

ozone. For Connecticut, the most favorable meteorological conditions for ozone production 

include high temperatures on sunny summer days, with lower level transport winds from the 

southwest and upper level transport winds from the west, regions with abundant emissions from 

EGUs and other source categories. 

While not specifically quantified in the modeling process, Connecticut worked with the Ozone 

Transport Commission (OTC) to design a high electric demand day strategy, which, when 

implemented throughout the OTC and aggressively targeted to the inner core, would achieve real 

air quality benefits.15 Due to the high cost of electricity at peak demand times and the need to 

assure reliability of supply, Connecticut’s energy planning and air quality planning are 

inextricably linked and being coordinated. Preliminary estimates indicate that current demand 

side reduction efforts have a 7 ton-per-day (tpd) NOX reduction benefit on peak days,16 and the 

State commitment to reduce peak demand will achieve a very significant further NOX reduction 

benefit on peak days. 

8.5.5.2 Reducing Peak Demand 

The current approaches to NOX control are not designed to effectively address short-term (e.g., 

hourly or daily) spikes in NOX emissions on high electric demand days. However, Connecticut 

has demonstrated that energy policies can be designed to significantly reduce peak electric 

demand and its resulting emissions. 

In September of 2006, Governor M. Jodi Rell addressed the peak demand issue in her “Energy 

Vision” for the state,17 setting a goal of achieving a 20% reduction in electric-peak consumption 

by 2020. Then, in June of 2007, she signed into law Public Act 07-242, An Act Concerning 

Electricity and Energy Efficiency (Energy Act),18 which includes three significant peak 

reduction measures. On the supply side, the Energy Act calls for mandatory decoupling of utility 

revenue from the sales of each electric and gas company in the next rate proceeding, thereby 

 

15 “Memorandum of Understanding Among the States of the Ozone Transport Commission Concerning the 

Incorporation of High Electrical Demand Day Emission Reduction Strategies into Ozone Attainment State 

Implementation Planning” March 2, 2007 and attached hereto as Appendix 8O. 

16 “Avoided Nitrogen Oxide Emissions from Energy Efficiency on High Electric Demand Days in Connecticut: A 

preliminary Analysis”, Resource Systems Group Inc. – March 2007, reproduced in Appendix 8P. 

17 “Connecticut’s Energy Vision for a Cleaner, Greener State,” September 18, 2006, available at 

http://www.ct.gov/governorrell/lib/governorrell/ctenergyvisionsept19.pdf . 18 Public Act 07-242, available at http://www.cga.ct.gov/2007/ACT/PA/2007PA-00242-R00HB-07432-PA.htm. 
8 - 32 

ending the incentive for electric utilities to sell more energy to increase profits. On the demand 

side, the Energy Act calls for the development of plans to implement time-of-use pricing with 

appropriate metering and network support (“smart meters”) to provide incentives for consumers 

to reduce electricity use at times of peak demand. The act will also reduce peak demand by 

providing rebates for the replacement of inefficient home air conditioning units with units that 

meet the federal Energy Star standard.

8.5.5.3 Energy Efficiency Measures 

The State’s efforts to promote Energy Efficiency (EE) as the “resource of first choice” have 

earned national recognition as Connecticut was named as one of the most energy efficient states 

in the country.19 When Governor Rell signed the Energy Act on June 4, 2007, she was building 

on existing exemplary demand reduction programs in effect in Connecticut. In addition to those 

mentioned above, several specific provisions of the Energy Act, when fully implemented, will 

result in additional emission reductions, which can be applied toward attainment. Some of these 

provisions include: 

• The mandatory assessment of energy efficiency and other clean energy resources, such as 

renewable energy, by Connecticut’s two major load serving entities – United Illuminating 

and Connecticut Light and Power; 

• A requirement that energy capacity needs must first be met through all available energy 

efficiency and demand-side resources that are cost effective, reliable and feasible; 

• The mandatory assessment of how best to eliminate or stabilize growth in electric 

demand; 

• The mandatory incorporation of the impact of current and projected environmental 

standards, including the ozone standard;

• All state building projects over $5 million must meet Leadership in Environmental 

Design Silver (LEEDS Silver) standards or better; 

• The creation of the first home heating oil conservation and efficiency program; 

• The adoption of appliance efficiency standards for nine additional products; and 

• The continued ramp-up of renewable energy portfolio requirements under which 20% of 

Connecticut’s energy shall be derived from renewable resources by the year 2020. 

Even without the legislative driver to reduce energy costs, per capita energy use in Conecticut, 

which has been constant at 250 million BTUs (75 MWh), is significantly lower than the average 

US consumption rate of 340 million BTUs (100 MWh). Only California and New York City 

have lower per capita consumption figures of 225 million BTUs (65 MWh).20 This low rate was 

achieved by Connecticut’s commitment to demand-side management. 

In Connecticut, the Energy Conservation Management Board (ECMB) advises and assists 

Connecticut’s electric distribution companies in the development and implementation of 

comprehensive and cost-effective energy conservation and market transformation plans. The 

 

19 “The State Energy Efficiency Score Card”, American Council for an Energy-Efficient Economy Report - Number 

E075, June 2007. 

20 The Connecticut Academy of Science and Engineering, “Energy Alternatives and Conservation,” December 2006. 
8 - 33 

ECMB utilizes the Connecticut Energy Efficiency Fund (CEEF) to provide financial support to 

homeowners and renters, small and large businesses, and state and local governments, for more 

efficient energy use. Measures include reducing lighting loads, installing more efficient air 

conditioning and cooling systems, improving insulation and replacing older motors and pumps 

with state-of-the-art high efficiency units. 

Additional support for demand-side management is provided by ISO-New England’s new 

Forward Capacity Market (FCM) Rules. Market Rule 1, and the new FWC rules, which take 

effect in 2010, will value EE and demand-side resources the same as traditional generation.21

EE measures have a lasting ‘cumulative’ effect on electric demand. The savings in the 

installation year of an EE measure continue for the duration of its known measured life, usually 

15 years. Therefore, efficiency savings installed one year can be added to the measures included 

in all of the proceeding years within its measured life. ECMB projected that $4 in future savings 

was generated from every $1 spent by CEEF in 2006, making for significant annual and 

cumulative totals. This concept is clearly shown in Table 8.5.5.3 below using data from the 

ECMB annual reports 2003 through 2006.22 The increased ECMB funding from the Energy Act, 

in conjunction with the ISO-NE FCM Rules should further increase NOX reductions in 2007. 

Table 8.5.5.3: Energy Savings and Emissions Reductions from CEEF Projects, 2003-2006 

YEAR Energy Saved in 

Thousands MWh 

CUMULATIVE 

ENERGY SAVED 

Thousands MWh 

NOX

reduced 

(Tons) 

Lifetime NOX Reduced 

from annual projects 

(Tons) 

2003 130.7 130.7 73 1151 

2004 291 421.7 112 1548 

2005 318 739.7 123 1702 

2006 328 1067.7 89 1243 

TOTALS 1067.7 1067.7 397 5644 

Although an assessment of reductions from EE measures is difficult to accomplish with a highdegree of precision, CTDEP with assistance from Resource Systems Group, Environmental 

Resources Trust (ERT) and DJ Consulting, LLC, developed a methodology designed to estimate 

NOX emission reductions on HEDDs resulting from EE and distributed resource measures.23 

CTDEP plans to further develop inputs to assess the effectiveness of this methodology in the 

belief that it will be an important tool moving forward. 

The adoption of Connecticut’s newest energy legislation, in addition to EE measures already in 

effect, demonstrates a firm commitment to EE by the State. While it is not yet possible to 

determine EE-associated emission reductions with the precision necessary for full federal 

approval and for SIP credit towards attainment of the 8-hour ozone NAAQS, this information 

and the future direction of Connecticut’s energy efficiency programs convey a compelling 

 

21 ISO-NE, Market Rule 1 and FWC Rules available at: http://www.iso-ne.com/index.html. 22 ECMB Annual Reports can be found at: http://www.ctsavesenergy.com/ecmb/documents.php?section=16. The 

ECMB 2006 Annual Report, March 2007 is reproduced in Appendix 8Q. 

23 The full report is reproduced in Appendix 8P. 
8 - 34 

argument that Connecticut’s EE programs are doing much to limit the growth of electricity 

demand and the otherwise high NOX emissions associated with such growth. 

The efforts Connecticut has made to reduce peak demand and encourage EE provide further 

weight-of-evidence that Connecticut could attain the 8-hour ozone NAAQS by 2009. 

8.5.6 Conclusions Based on Modeling and Weight of Evidence Analyses

CMAQ modeling performed by the OTC states and weight-of-evidence (WOE) analyses 

conducted by CTDEP indicate the following for the Greater Connecticut moderate ozone 

nonattainment area: 

• The CMAQ model projects that the 8-hour ozone NAAQS of 85 ppb will be achieved in 

the Greater Connecticut area by the June 2010 attainment deadline (as determined based 

on ozone levels at the end of the previous full ozone season, 2009). 

• Projected ozone levels throughout Greater Connecticut in 2009 are also less than the 

lower WOE boundary of 82 ppb, providing a high degree of confidence that the area will 

reach attainment by the end of the 2009 ozone season. 

The CMAQ modeling and WOE analyses indicate the following for the Southwest Connecticut 

portion of the NY/NJ/CT moderate ozone nonattainment area: 

• The CMAQ model projects that four of the seven monitors in Southwest Connecticut will 

achieve 2009 design values lower than the 85 ppb 8-hour NAAQS. CMAQ projects 

residual nonattainment at the other three Southwest Connecticut monitoring sites, with 

design values at all seven sites within the WOE bounds of 82 to 87 ppb. 

• Several forms of WOE analyses were conducted for Southwest Connecticut. Findings 

are listed below. 

o CMAQ modeling uncertainties regarding EGU HEDD emissions, EGU control 

strategy effectiveness, elevated transport, and sea breeze effects suggest that 

CMAQ predictions of 2009 ozone levels may be overestimated and that any 

residual nonattainment at coastal sites will require additional upwind reductions to 

achieve attainment. 

o Improvements in actual measured ozone levels over the last several years have 

outpaced CMAQ model predictions in northeastern states, including key monitors 

in Southwest Connecticut. These improvements suggest that measured design 

values in 2009 may be less than predicted by the CMAQ model and may be low 

enough to achieve attainment by 2009. 

o In 2004, Connecticut experienced a cool summer with 4th-high ozone levels at (85 

ppb in Danbury) or below (all other Connecticut monitors) the 8-hour ozone 

NAAQS. With significant emission reductions occurring between 2002 and 2009, 

a similar, or even slightly warmer summer, could produce ozone levels in 

Southwest Connecticut that meet the NAAQS. 
8 - 35 

o Section 181(a)(5) of the CAA provides a mechanism for up to two, one-year 

extensions of the June 2010 attainment deadline for moderate areas. Therefore, if 

“clean data” are recorded throughout the nonattainment area in 2009, Southwest 

Connecticut could be eligible for a CAA extension of the moderate nonattainment 

area attainment deadline to as late as the end of the 2011 ozone season. 

o Significant emission control programs not included in the CMAQ modeling 

should provide additional improvements in ozone levels. These include HEDD 

emission reductions strategies being pursued by Connecticut and other 

northeastern states, expanding energy efficiency programs, recent large financial 

commitments to mass transit and other efforts to reduce vehicle traffic and 

emissions, and EPA national efforts to further reduce VOC and NOX emissions 

from a number of stationary and mobile source categories. 

In conclusion, the results of the CMAQ modeling and WOE analyses suggest a high degree of 

confidence that the Greater Connecticut area will attain the 8-hour ozone NAAQS by 2009. In 

addition, a very credible case can be made for attainment of the NAAQS throughout Southwest 

Connecticut by 2009, with a greater level of confidence in each subsequent year, such that 

attainment is highly likely by the end of the 2012 ozone season.