STATE OF NEW HAMPSHIRE

STATE IMPLEMENTATION PLAN REVISION 

CARBON MONOXIDE LIMITED MAINTENANCE PLAN 

for the 

THE CITY OF MANCHESTER AND THE CITY OF NASHUA 

CARBON MONOXIDE MAINTENANCE AREAS 

August 1, 2012 

29 Hazen Drive 

P.O Box 95 

Concord, NH 03302-0095 

www.des.nh.gov
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Table of Contents 

1 Introduction 4 

2 Background 4 

3 Limited Maintenance Plan Option 5 

3.1 Attainment Emissions Inventory 6 

3.2 Demonstration of Continued Attainment 8 

3.3 Monitoring Network/Verification of Continued Attainment 10 

3.4 Contingency Plan 12 

3.5 Conformity Determination under Limited Maintenance Plans 13 

4 Conclusion 15 

5 Public Record & Comment 15 

List of Tables 

Table 1 Winter Day CO Emissions for Hillsborough County, 2008 7

Table 2 CO Emissions for Hillsborough County, 1999 – 2008 8 

Table 3 CO Emissions for New Hampshire, 1999 – 2008 8 

Table 4 1 and 8-hour Design Values by year (Manchester & Nashua) 9 

Table 5 1 and 8-hour 2nd Highest Concentrations by year (Manchester & Nashua) 10 

Table 6 Manchester CO Conformity Determination Projection 14 

Table 7 Nashua CO Conformity Determination Projection 14

 

List of Figures 

Figure 1 Annual 1-hour 2nd Highest Concentrations, (Manchester & Nashua) 10 

Figure 2 Annual 8-hour 2nd Highest Concentrations, (Manchester & Nashua) 10

 

Attachments 

Attachment 1 Memorandum: “Limited Maintenance Plan Option for Nonclassifiable CO 

Nonattainment Areas”; Joseph W. Paisie, Group Leader; Integrated Policy and 

Strategies Group; October 6, 1995 

Attachment 2 Letter from Anne Arnold, EPA Air Quality Planning Unit: Air Quality 

Conformity: Statewide Transportation Improvement Program Amendment Number 1 

(2011 – 2014 STIP); to Kathleen O. Laffey; May 4, 2011 

Attachment 3 Memorandum: Limited Maintenance Plan Option for Moderate PM10

Nonattainment Areas; Lydia Wegman, Director; August 21, 2001 

Attachment 4 Public Notice 

Attachment 5 Proof of Publication 

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1. Introduction 

The City of Manchester (Manchester) and the City of Nashua (Nashua) were designated 

nonattainment by the U.S. Environmental Protection Agency (EPA) for carbon monoxide (CO) 

in 1980 (45 FR 24869 and 48 FR 29479, respectively). The National Ambient Air Quality 

Standard (NAAQS) for CO is 9.0 parts per million (ppm) for an 8-hour average concentration 

and 35 ppm for a 1-hour concentration, not to be exceeded more than once per calendar year. In 

1991, following passage of the Clean Air Act Amendments of 1990 (CAA), both cities were 

classified “nonattainment” and “not classified” (56 FR 56694) although ambient monitoring 

showed NAAQS attainment had been achieved by that time. In February 1999, the State of 

New Hampshire submitted a formal CO redesignation request as part of a CO Maintenance 

Plan for Manchester and Nashua and, effective January 29, 2001, EPA redesignated 

Manchester (65 FR 71078) and Nashua (65 FR 71078) from CO nonattainment, to CO 

attainment and approved New Hampshire’s CO Maintenance Plan. 

Significant progress continues to be made in reducing CO levels across the northeast including 

the Manchester and Nashua areas. Dramatic reductions in CO levels from more fuel-efficient 

and cleaner operating vehicles, improved (OBD II) vehicle diagnostic equipment and cleaner 

burning fuels have cut CO emissions despite growth. No violations of the CO NAAQS have 

been recorded in the Manchester or Nashua areas since 1986 and the highest level of CO in 

either town in the last three years has been less than one half of the CO NAAQS. In addition to 

the downward trend shown by the monitoring data, the state has performed mobile source 

modeling and conformity analyses that indicate winter CO emissions in Manchester and 

Nashua will not reach even half of the CO Conformity Budget as far into the future as 2035, 

well beyond the end of the maintenance plan. 

Section 175A of the CAA requires a demonstration of continued attainment for at least ten 

years following EPA’s redesignation to attainment. Eight years after the redesignation, a state 

must submit a revised maintenance plan demonstrating attainment for the ten years following 

the initial ten-year period. Although New Hampshire’s 1999 redesignation submittal was 

developed as a 20-year maintenance plan starting with the CO redesignation effective date, the 

New Hampshire Department of Environmental Services (DES) is submitting this State 

Implementation Plan (SIP) revision under the limited maintenance plan option as described in 

an October 6, 1995, U.S. EPA guidance memorandum (“Option Memo”) (Attachment 1).1

 

This maintenance plan is being submitted to cover the second 10-year maintenance period 

starting January 29, 2011 and running through January 29, 2021.

 

2. Background 

The cities of Manchester and Nashua were designated CO nonattainment areas on April 11, 

1980. Pursuant to Section 107(d)(1)(C) of the CAA , the cities retained their designation of 

nonattainment for CO under the law even though that at the same time, the cities were 

1

 Memorandum: “Limited Maintenance Plan Option for Nonclassifiable CO Nonattainment Areas”; Joseph W. 

Paisie, Group Leader; Integrated Policy and Strategies Group; October 6, 1995 

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classified as “not classified” since ambient monitoring data for the areas showed attainment of 

the CO NAAQS. In 1987, the State of New Hampshire initiated a basic CO 

Inspection/Maintenance (I/M) program in Nashua and 11 surrounding towns. That program 

was designed to cease operating on January 1, 1995, at which time the State legislature allowed 

it to end. On February 1, 1999, DES submitted a revision to the SIP to remove the Nashua I/M 

program. That program was replaced with controls consisting of the existing federal Tier 1 

emission standards for new vehicles and the federal reformulated gasoline program. Because 

the Manchester and Nashua areas were “not classified” under Section 172, the CAA set forth 

the applicable requirements for nonattainment areas. The CAA required such an area to 

achieve the standard by November 15, 1995, and both cities have fulfilled this requirement. 

On February 2, 1999, DES submitted a request to redesignate the cities of Manchester and 

Nashua from CO nonattainment areas to CO attainment areas. EPA approved the redesignation 

in November, 2000 (65 FR 71060). As part of the redesignation request, the State submitted a 

maintenance plan as required by 175A of the Clean Air Act, as amended in 1990. Elements of 

the Section 175A maintenance plan included a base year (1990 attainment year) emission 

inventory for CO, a demonstration of NAAQS maintenance, a plan to verify continued 

attainment, a contingency plan and an obligation to submit additional information 

acknowledging that the maintenance plan would remain in effect through the year 2020, as 

required by the CAA. The redesignation request established a Manchester motor vehicle 

emissions budget of 55.83 tons per day and a Nashua motor vehicles CO emission budget of 

60.13 tons per day to be used in determining transportation conformity in the Manchester and 

Nashua areas. 

On May 30, 2007, DES submitted a modification of the approved Nashua maintenance plan, 

discontinuing CO monitoring in Nashua, which was approved by EPA on September 10, 2007 

(72 FR 51564). Under that modification, DES agreed to continue to collect and review CO 

monitoring data from nearby Manchester. In the event monitoring data showed CO levels in 

Manchester reached 75% of the federal 1-hour or 8-hour NAAQS CO limit, an operating 

monitoring site in Nashua would be re-established and DES would resume analyzing and 

reporting monitoring data. New Hampshire is now proposing to discontinue CO monitoring in 

Manchester and to rely instead on the monitoring station in nearby Londonderry. 

3. Limited Maintenance Plan Option 

On October 6, 1995, EPA published the Joseph W. Paisie Limited Maintenance Plan Option 

Memo. Based on that guidance, the core elements of a Limited Maintenance Plan are: 

 Attainment inventory identifying the levels of emissions in an area;

 Maintenance Demonstration showing that design values do not exceed 85% of the 

NAAQS; 

 Monitoring to verify continued eligibility; 

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 Contingency Plan identifying measures to be adopted in the event of a NAAQS 

violation; and

 Conformity Determination discussion.

3.1 Attainment Inventory

Regarding the attainment inventory, the Option Memo notes that “[t]he State should develop an 

attainment emissions inventory to identify a level of emissions in the area which is sufficient to 

attain the NAAQS. This inventory should be consistent with EPA’s most recent guidance on 

emissions inventories for nonattainment areas available at the time and should represent 

emissions during the time period associated with the monitoring data showing attainment. The 

inventory should be based on actual ‘typical winter day’ emissions of CO.” To this end, DES 

has prepared an attainment inventory for year 2008 for Hillsborough County which 

encompasses the cities of Manchester and Nashua. 

The 2008 attainment inventory is subdivided into the following general emissions categories: 

 Point Sources, which represent discrete facilities. These sources usually must meet 

certain emission criteria to be included as point sources and generally represent larger 

facilities. 

 Area Sources, which represent facilities and activities too numerous and widespread to 

be inventoried individually but which collectively may account for significant 

emissions. 

 Non-Road Mobile Sources, including aircraft, locomotives, commercial marine vessels, 

construction vehicles, lawn & garden equipment, and other mobile vehicles and 

equipment that are not meant to be operated on roadways. 

 On-Road Mobile Sources, including cars, trucks, buses, motorcycles, and other vehicles 

that operate on public roadways. 

The methodologies used in preparing the 2008 emissions estimates are summarized in the 

following paragraphs. 

For point sources, affected facilities in New Hampshire are required to report their emissions 

on an annual basis. The reporting requirements for these facilities are provided under New 

Hampshire’s air regulations, its state air permitting program, and the Air Emissions Reporting 

Requirement. Data submitted by these facilities are extensively cross-checked and quality 

assured by DES staff before eventual submittal to EPA. The point source data contained in 

New Hampshire’s 2008 attainment inventory originated from the quality-assured 2008 data 

from all reporting point sources in Hillsborough County. 

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The methodologies used to estimate emissions for area source categories come primarily from 

EPA’s Emissions Inventory Improvement Program (EIIP). Calculations for many area source 

categories are based on variables such as population, employment, and fuel consumption data. 

Descriptions of the methodologies for specific area source categories can be found in EIIP 

Volume 3, Area Sources, which is available at EPA’s Clearinghouse for Inventories and 

Emissions Factors website at http://www.epa.gov/ttn/chief/eiip/techreport/volume03/index.html. 

Seasonal adjustment factors from Table 1.4-3 of EIIP Volume III were used to derive winter 

season day estimates for the applicable source categories (e.g. residential heating). 

For the non-road mobile category, DES used EPA’s NONROAD2008a model to estimate 

2008 emissions for those equipment types that are included in the model. The NONROAD 

model was run for a winter season day. For commercial aircraft and airport ground service 

equipment, the Federal Aviation Agency’s (FAA’s) Emissions & Dispersion Modeling System 

(EDMS) was used. Standardized methodologies and references were employed for equipment 

types not included in the EDMS or NONROAD models (e.g., locomotives and commercial 

marine vessels). 

For on-road mobile sources, DES used MOVES2010a with VMT and other road related data 

provided by the relevant metropolitan planning organizations (MPOs) as well as vehicle 

population data obtained from the New Hampshire Department of Safety, Division of Motor 

Vehicles. 

Estimated winter day CO emissions for the 2008 attainment inventory are shown in Table 1. 

Table 1 - Winter Day CO Emissions for Hillsborough County, 2008 

Category CO emissions (tons per winter day) 

Point 0.6* 

Area 37.1 

Non-Road Mobile 40.0 

On-Road Mobile 165 

Total 242.7 

*Estimated tons per average day 

On-Road Mobile emissions generated using MOVES2010a 

Tables 2 and 3 illustrate annual CO emissions in the Manchester and Nashua area 

(Hillsborough County) and statewide. As Table 2 demonstrates, the total 2008 Hillsborough 

County emissions from all sources are estimated to be 77,311 tons with all mobile sources 

estimated to contribute 40,576 tons or 52% of the total.

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Table 2 - CO Emissions for Hillsborough County, 1999 – 2008 

CO emissions (tons per year) 

Category 1999 2002 2005 2008 

Point 184 143 191 92 

Area 12,822 12,864 13,210 13,384 

Non-Road Mobile 32,162 29,216 26,776 23,259 

On-Road Mobile 92,831 58,379 58,666 40,576 

Total 137,999 100,602 98,841 77,311 

Sources of Data

1999 and 2002: National Emissions Inventory data from EPA's Air Data website. 

2005: 2005 National Emissions Inventory, Version 2 downloaded from EPA's CHIEF website. 

2008: 2008 National Emissions Inventory, Version 1.5 downloaded from EPA's EIS Gateway. 

Table 3 - CO Emissions for New Hampshire, 1999 - 2008 

CO emissions (tons per year) 

Category 1999 2002 2005 2008 

Point 4,923 2,724 4,754 3,357 

Area 78,133 74,099 73,706 47,798 

Non-Road Mobile 123,530 124,801 119,322 104,887 

On-Road Mobile 345,413 294,533 236,990 174,154 

Total 552,000 496,157 434,772 330,196 

Sources of Data

1999 and 2002: National Emissions Inventory data from EPA's Air Data website. 

2005: 2005 National Emissions Inventory, Version 2 downloaded from EPA's CHIEF website. 

2008: 2008 National Emissions Inventory, Version 1.5 downloaded from EPA's EIS Gateway. 

From 1999 to 2008, CO mobile source emissions declined by 49% in Hillsborough County 

and by 22%, statewide. Monitored levels of CO have continued to decrease over the last 

decade and the modeled emissions of CO from on-road sources mirror this downward trend. 

The availability of cleaner cars through the Federal Motor Vehicle Control Program, 

together with the addition of local transportation controls such as New Hampshire’s 

Inspection & Maintenance Program, including an annual On-Board Diagnostics inspection, 

have resulted in decreased emissions and, hence, lower CO concentrations. 

3.2. Demonstration of Continued Attainment 

According to the Option Memo, “[t]he maintenance demonstration requirement is 

considered to be satisfied if the monitoring data show that the area is meeting the air quality 

criteria for limited maintenance areas (7.65 ppm or 85% of the CO NAAQS) . There is no 

requirement to project emissions over the maintenance period. EPA believes if the area 

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begins the maintenance period at or below 85 percent of exceedance levels, the air quality 

along with the continued applicability of PSD requirements, any control measures already 

in the SIP, and Federal measures, should provide adequate assurance of maintenance over 

the initial 10-year maintenance period. 

When EPA approves a limited maintenance plan, EPA is concluding that an emissions 

budget may be treated as essentially not constraining for the length of the maintenance 

period because it is unreasonable to expect that such an area will experience so much 

growth in that period that a violation of the CO NAAQS would result.” DES interprets this 

to mean that such an area is no longer required to demonstrate conformity to a CO motor 

vehicle emissions budget. 

To qualify for the limited maintenance plan option, the CO Design Value for the area must 

be at or below 7.65 ppm (85% of the NAAQS 8-hour level of 9 ppm), based on at least 8 

consecutive quarters (2 years) of data used to demonstrate attainment. Observation of the 

second highest 8-hour concentration is also an indicator of the area’s proximity to violating 

the standard. 

2000 to 2010 1-hour and 8-hour Design Values and 1-hour and 8-hour second highest CO 

concentrations for Manchester and Nashua are summarized in Tables 4 and 5. The annual 

1-hour and 8-hour second highest concentrations are represented graphically in Figures 1 

and 2. In all cases, the design values and second highest concentrations are significantly 

less than the 7.65 ppm threshold specified in EPA guidance, thus making each area eligible 

for the limited maintenance plan option. 

Table 4 - 1-hour and 8-hour Design Values by year (Manchester and Nashua)* 

Manchester Nashua 

Bridge St Pearl St Main St 

Year 1-hr 8-hr 1-hr 8-hr 1-hr 8-hr 

2000

2001 7.1 3.6 8 4.1 

2002 3.7 2 6.5 4 

2003 4.8 3.4 6.2 4 

2004 4.8 3.4 6.2 4 

2005 2.8 1.8 6.1 3.2 

2006 8.1 3 9.1 3.2 

2007 8.1 3 9.1 2.4 

2008 6 3.5 

2009 6 3.5 

2010 3.2 2.4 

* Note: Because CO Design Values are based on the higher value between one year and the previous year, there is no design 

value for 2000, the first year in which data was recorded. 

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Table 5 – 1-hour and 8-hour 2nd high concentrations by year (Manchester and Nashua) 

 Manchester Nashua 

 Bridge St Pearl St Main St 

Year 1-hr 8-hr 1-hr 8-hr 1-hr 8-hr 

2000 7.1 3.6 8 4.1 

2001 4.6 3.1 6.5 4 

2002 3.7 2 5.9 3.7 

2003 4.8 3.4 6.2 4 

2004 2.2 1.4 4.3 2.8 

2005 2.8 1.8 6.1 3.2 

2006 8.1 3 9.1 2.4 

2007 2.6 1.8 3.7 2.2 

2008 6 3.5 

2009 3.2 2 

2010 3.1 2.4 

Figure 1 - Annual 1-Hour 2nd Highest 

Concentrations - 2000 - 2010

2001 2002 2003 2004 2005 2006 2007 2008 2009 2010

Figure 2 - Annual 8-Hour 2nd Highest 

Concentrations - 2000 - 2010

0

1

2

3

4

5

6

7

8

9

10

2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010

Parts per Million

Manchester 

Nashua 

NAAQS

0

5

10

15

20

25

30

35

40

2000

Parts per Million

Manchester 

Nashua 

NAAQS

3.3. Monitoring Network/Verification of Continued Attainment 

With respect to monitoring, the Option Memo reads: “To verify the attainment status of the 

area over the maintenance period, the maintenance plan should contain provisions for 

continued operation of an appropriate, EPA-approved air quality monitoring network, in 

accordance with 40 CFR 58. This is particularly important for areas using a limited 

maintenance plan, because there wi11 be no cap on emissions.” 

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As part of this Limited CO Maintenance Plan, New Hampshire is proposing to discontinue 

monitoring CO at its Manchester site. In lieu of operating that site, DES plans to track CO 

using data collected from the following sources: 

1. CO monitoring will continue year-round at the Londonderry Moose Hill station in 

Londonderry. The Londonderry Moose Hill Station came online on January 1, 2011 

as an NCore2

 superstation measuring a wide variety of pollutants. DES worked 

closely with EPA to carefully select this site due to its central proximity to 

Manchester and Nashua. The Londonderry station measures PM 2.5 (continuous 

and filter-based) Nitrogen Oxides, Ozone, Sulfur Dioxide (trace) and Carbon 

Monoxide (trace) as well as wind speed, wind direction and relative humidity. 

2. New Hampshire’s emissions inventory tabulates CO emissions from point, area and 

mobile sources. As demonstrated earlier (see Table 1), New Hampshire has been in 

attainment for CO since 1999 and the vast preponderance of NH CO emissions are 

from mobile sources. New Hampshire will continue to provide a multi-source 

inventory every 3 years that will be used for identifying CO mobile source 

emissions trends within the state. 

A review of over 8,600 hourly samples taken since the Londonderry station came online 

shows 1-hour CO levels varying from 0.0 ppm to a high of 2.65 ppm at 2:00 AM on 

January 11, 2011. Because design values are based on two years of data, and the 

Londonderry station has been operating for only 15 months, it is not yet possible to 

calculate the maximum and second maximum 8-hour design values over two years as 

protocol requires. Using 15 months of values averaged over 8-hour non-overlappping 

periods, the maximum 8-hour highest and 2nd highest CO Design Values, are 1.77 and 1.23 

ppm, respectively. Similar to the Nashua and Manchester station results, these levels are 

well below the CO NAAQS. The relatively short period of Londonderry station operation, 

however, makes it impossible to determine if there is a general downward trend in CO 

levels, as demonstrated by 10 years of data from the Nashua and Manchester stations. 

 

Should the present downward trend of mobile source CO emissions reverse, and in the 

event the second-highest CO concentration in any calendar year monitored in Londonderry 

reaches 50 percent of either the federal 1-hour or 8-hour NAAQS for CO, New Hampshire 

will, within six months, reestablish a CO monitoring site in Manchester consistent with 

EPA siting criteria and resume analyzing and reporting those data. New Hampshire 

commits to implement its contingency program in Nashua in the event that a CO violation 

is monitored at the re-established Nashua monitoring site at any time during the 

 

2 One of the most significant changes in the EPA air monitoring regulations was the requirement to establish 

National Core (NCore) multi-pollutant monitoring stations. These stations will provide data on several pollutants 

at lower detection limits and replace the National Air Monitoring Station (NAMS) networks that have existed for 

several years. 

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maintenance period. If the Manchester CO monitor measures a violation of the either the 

federal 1-hour or 8-hour NAAQS for CO, contingency measures will be implemented in 

Nashua as well, until a re-established CO monitor in Nashua shows that the area is in 

attainment of the CO standard. 

3.4. Contingency Plan 

According to the Option Memo, “Section 175A of the CAA requires that a maintenance 

plan include contingency provisions, as necessary, to promptly correct any violation of the 

NAAQS that occurs after redesignation of the area. These contingency measures do not 

have to be fully adopted at the time of redesignation. However, the contingency plan is 

considered to be an enforceable part of the SIP and should ensure that the contingency 

measures are adopted expeditiously once they are triggered by a specified event. The 

contingency plan should identify the measures to be promptly adopted and provide a 

schedule and procedure for adoption and implementation of the measures. The State should 

also identify specific indicators, or triggers, that will be used to determine when the 

contingency measures need to be implemented. While an exceedance of the NAAQS is an 

acceptable trigger, States may wish to choose a pre-exceedance action level as a trigger. By 

taking early action, a State may be able to prevent any actual violation of the NAAQS and, 

therefore, eliminate any need on the part of EPA to redesignate an area back to 

nonattainment.” 

DES believes that specific contingency measures are not needed at the present time, since 

the current CO levels are so far below the NAAQS, and since emissions from mobile 

sources, the dominant source of CO in the State and Manchester and Nashua regions, are 

decreasing in spite of increasing population. As mentioned, previously implemented 

contingency measures and emissions reductions strategies have proven successful, and 

these will be continued through the maintenance period. These include: 

 Vehicle Inspection/Maintenance (I/M) - Although federal regulations (40 CFR 

51.350) required New Hampshire to implement an I/M program with tailpipe 

emissions testing, New Hampshire’s program of anti-tampering inspections for pre1996 vehicles less than 20 years old and an OBD II inspection on all model years 

1996 and newer has provided superior environmental benefits to expensive and 

onerous tailpipe testing. New Hampshire will continue its EPA-approved OBD II 

program as a SIP strengthening measure. 

 Vehicle Miles Traveled reductions – Reducing vehicle use and traffic congestion, 

and their associated emissions, are key state and local transportation objectives. 

DES will continue to work with DOT and regional MPOs to identify effective 

congestion and emission reduction project and programs such as such as traffic 

signal coordination, increased mass transit, RideShare, anti-idling and other traffic 

management strategies. 

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 Emissions reductions – New Hampshire continues to enjoy the benefits of the 

Federal Clean Fuel Programs that resulted in reduced CO emissions. In keeping 

with President Obama’s 2009 national fuel economy and emissions policy, DES and 

local MPOs are actively promoting low emissions vehicles and emissions reductions 

strategies such as anti-idling programs and park & ride lot construction as part of 

their long range transportation plans. 

Because New Hampshire proposes to discontinue monitoring CO in Manchester, it will 

adopt a more stringent contingency threshold or “trigger” than indicated in the 2007 SIP 

revision. As indicated in Section 3.3 above, New Hampshire will monitor CO levels using 

the Londonderry Moose Hill station and emissions inventories. In the event the secondhighest CO concentration in any calendar year monitored in Londonderry reaches 50 

percent of the federal 1-hour or 8-hour NAAQS for CO, New Hampshire will, within six 

months of recording such concentrations, reestablish the CO monitoring site in Manchester 

consistent with EPA siting criteria, and resume analyzing and reporting those data. New 

Hampshire commits to implement a contingency program in Nashua in the event that a CO 

violation is monitored at the re-established Nashua monitoring site at any time during the 

maintenance period. If the Manchester CO monitor measures a violation of the either the 

federal 1-hour or 8-hour NAAQS for CO, contingency measures will be implemented in 

Nashua as well, until a re-established CO monitor in Nashua shows that the area is in 

attainment of the CO standard. 

3.5. Conformity Determination under Limited Maintenance Plans 

In discussing conformity, the Option Memo reads: “The transportation conformity rule 

(Determining Conformity of Federal Actions to State or Federal Implementation Plans; 40 

CFR 93; amended 1998) and the general conformity rule (Requirements for Preparation, 

Adoption, and Submittal of Implementation Plans; 40 CFR 51; adopted 1994) apply to 

nonattainment areas and maintenance areas operating under maintenance plans. Under 

either rule, one means of demonstrating conformity of Federal actions is to indicate that 

expected emissions from planned actions are consistent with the emissions budgets for the 

area. Emissions budgets in limited maintenance plan areas may be treated as essentially not 

constraining for the length of the initial maintenance period because it is unreasonable to 

expect that such an area will experience so much growth in that period that a violation of 

the CO NAAQS would result. In other words, EPA would be concluding that emissions 

need not be capped for the maintenance period. Therefore, in areas with approved limited 

maintenance plans, Federal actions requiring conformity determinations under the 

transportation conformity rule could be considered to satisfy the ‘budget test’ required in 40 

CFR 93.118, 93.119, and 93.120 of the rule. Similarly, in these areas, Federal actions 

subject to the general conformity rule could be considered to satisfy the ‘budget test’ 

specified in section 93.158 (a) (5) (i) (A) of the rule.” As this is guidance, final and binding 

determinations regarding the eligibility of areas for the limited maintenance plan option will 

only be made in the context of notice and comment rulemaking actions regarding specific 

redesignation requests. 

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In recent conformity determinations (see attachment 2: May 4, 2011 letter to FHWA 

Administrator Ms. Kathleen O. Laffey from EPA Air Quality Planning Unit Manager Anne 

E. Arnold) the Southern NH MPO and the Nashua MPO have demonstrated that 

transportation conformity for the Manchester and Nashua CO attainment areas and the 

motor vehicle emissions for future years are consistent with the 2010 motor vehicles 

emissions budgets of 55.83 tons of CO per winter day in Manchester and 60.13 tons of CO 

per day in Nashua (Tables 6 and 7). In fact, the projected CO emissions are less than half 

of the budgets in both areas.

Table 6 – Manchester CO Conformity Determination Projection 

Carbon Monoxide Analysis Summary for the City of Manchester 

Year CO tons/day (winter) CO Budget (tons/day) 

2012 28.80 55.83 

2017 26.65 55.83 

2026 26.38 55.83 

2035 27.66 55.83 

 

 

Table 7 – Nashua CO Conformity Determination Projection 

Carbon Monoxide Analysis Summary for the Nashua 

Year CO tons/day (winter) CO Budget (tons/day) 

2012 28.73 60.13 

2017 26.11 60.13 

2026 25.51 60.13 

2035 26.64 60.13 

 

Consistent with Mr. Paisie’s and Ms. Arnold’s memos, DES will use the Interagency 

Consultation (IAC) process to inform the New Hampshire Department of Transportation 

(NHDOT) and MPOs that, upon approval of the limited maintenance plans, CO emissions 

budgets will no longer be constraining for transportation conformity because of the low 

levels of emissions, continued CO reductions resulting from 2000 Maintenance Plan 

reduction measures implementation, and expected growth during the maintenance period. 

EPA further discusses the implications of a Limited Maintenance Plan (LMP) on 

conformity requirements in an August 21, 2001 guidance memorandum to EPA Regional 

Air Directors (see attachment 3: Lydia Wegman memorandum; Limited Maintenance Plan 

Option for Moderate PM10 Nonattainment Areas). That memo reads in part, “Emissions 

Budgets in LMP areas may be treated as essentially not constraining for the length of the 

maintenance period because it is unreasonable to expect that an area satisfying the LMP 

criteria will experience so much growth during that period of time such that a violation of 

the PM10 NAAQS would result. While this policy does not exempt an area from the need to 

affirm conformity, it does allow the area to demonstrate conformity without undertaking 

certain requirements of these rules. For transportation conformity purposes, EPA would be 

concluding that emissions in these areas need not be capped for the maintenance period, 

and, therefore, a regional emissions analysis would not be required.” As this guidance 

14
15

suggests, New Hampshire will still be subject to CAA requirements to ensure CO 

conformity in LMP areas, but MPOs will not be required to provide regional analyses as 

long as LMP conditions are met. However, this is not to say that MPOs no longer have 

responsibility for ensuring individual transportation projects do not cause or contribute to 

any new localized CO violations. As per 40 CFR 93.116, project sponsors will still be 

required to perform hot-spot analyses for FHWA/FTA projects to demonstrate no new local 

violations will be created as a result of the projects. 

4. Conclusion 

CO levels in the Nashua and Manchester maintenance areas have remained under the CO 

standard as a result of national and local control strategies implemented. In fact, the current 

design value for both areas is less than half the standard. The current design values in the areas 

have remained below the standard since both areas were designated and are expected to 

continue to maintain compliance with the standard. New Hampshire has verified that the 

emission controls adopted to maintain the standard continue to be permanent and enforceable, 

that there are no new significant sources of carbon monoxide or increases in background 

emissions and that the state has in place a program to identify sources of exceedance and 

address any violation through enforcement and implementation of a contingency plan. 

This plan satisfies New Hampshire’s obligation under Section 175A(b) of the CAA to submit a 

plan for maintaining the national primary ambient air quality standard for CO for the next ten 

years beyond the current maintenance plan. 

5. Public Record & Comment 

In accordance with 40 CFR 51.102, public participation in this request was provided as follows: 

Notice of availability of the complete document and a notice of opportunity for the public to 

submit written comments and request a public hearing were published on June 22, 2012, in the 

UNION LEADER and posted on the DES website at 

http://des.nh.gov/organization/divisions/air/tsb/tps/msp/categories/hot.htm. 

The comment period closed at 4:00 PM on July 23, 2012. During that period, a public hearing 

on the proposed plan was not requested. The only comments received on the proposed plan 

were from EPA by letter dated July 19, 2012. EPA stated that, in the unlikely event monitors 

should ever measure a violation or concentrations such that the design value exceeds 85% of 

the CO NAAQS, a full maintenance plan must be developed. In addition, EPA noted that the 

effective date of the CO redesignation was January 29, 2001, thereby establishing January 29, 

2021 as the end of the 20-year maintenance period. The plan was revised to reflect this date. 

A copy of the legal public notice can be found as Attachment 4 and a copy of proof of 

publication can be found as Attachment 5. 
ATTACHMENT 1 







ATTACHMENT 2 



ATTACHMENT 3 
 

1This memorandum is intended to provide EPA's preliminary views on how certain moderate PM10 nonattainment

areas may qualify to submit a maintenance plan that meets certain limited requirements. Since it represents only the Agency's

preliminary thinking that is subject to modification, this guidance is not binding on States, Tribes, the public, or EPA. Issues

concerning the applicability of the limited maintenance plan policy will be addressed in actions to redesignate moderate PM10

nonattainment areas under § 107 of the CAA. It is only when EPA promulgates redesignations applying this policy that those

determinations will become binding on States, Tribes, the public, and EPA as a matter of law.

 

2Moderate PM10 areas that do not meet the applicability criteria of this policy, and all serious PM10 nonattainment

areas, should submit maintenance plans that meet our guidance for submission of a full maintenance plan as described in the

September 4, 1992 memorandum, “Procedures for Processing Requests to Redesignate Areas to Attainment,” from John

Calcagni, former Director of the Office of Air Quality Planning and Standards (OAQPS) Air Quality management Division to the

Regional Air Division Directors (hereafter known as the Calcagni Memo).

MEMORANDUM

SUBJECT: Limited Maintenance Plan Option for Moderate PM10 Nonattainment Areas 

FROM: Lydia Wegman, Director 

AQSSD (MD-15) 

TO: Director, Office of Ecosystem Protection, Region I 

Director, Division of Environmental Planning & Protection, Region II

Director, Air Protection Division, Region III

Director, Air, Pesticides & Toxics Management Division, Region IV

Director, Air and Radiation Division, Region V

Director, Air Pesticides & Toxics, Region VI

Director, Air and Toxics Division, Regions VII, IX 

Director, Air Program, Region VIII 

Director, Office of Air Quality, Region X

I. What is a Limited Maintenance Plan?

This memorandum sets forth new guidance1 on maintenance plan submissions for certain

moderate particulate matter (PM10) nonattainment areas seeking redesignation to attainment (see

section IV for further details on qualifying for the policy). If the area meets the criteria listed in this

policy the State may submit a maintenance plan at the time it is requesting redesignation that is more

streamlined than would ordinarily be permitted. This new option is being termed a limited maintenance

plan (LMP)2. 

II. Why is there a need for a limited maintenance plan policy?
2

 

3

 Dr. Shao-Hang Chu's paper entitled "Critical Design Value and Its Applications" explains the CDV approach and is

included in its entirety in Attachment A. This paper has been accepted for publication and presentation at the 94th Air and

Waste Management Association (A&WMA) Annual Conference in June 2001 in Orlando, Florida.

Before the U.S. Court of Appeals for the District of Columbia handed down its decision

vacating the 1997 PM10 national ambient air quality standards (NAAQS)(see American Trucking

Associations, et al. v. Environmental Protection Agency (EPA), 175 F.3d 1027 (D.C. Cir. 1999), we

were prepared to make case-by-case determinations that would make the 1987 PM10 NAAQS no

longer applicable in any area meeting the standards. In taking actions to remove the applicability of the

1987 NAAQS, we would have removed, as well, the nonattainment designation and Clean Air Act

(CAA) part D requirements from qualifying areas. As a result of the D.C. Circuit’s decision, for areas

subject to the 1987 NAAQS, the only route to recognized attainment of the NAAQS and removal of

nonattainment status and requirements is formal redesignation to attainment, including submittal of a

maintenance plan. Since many areas have been meeting the PM10 NAAQS for 5 years or more and

have a low risk of future exceedances, we believe a policy that would allow both the States and EPA to

redesignate speedily areas that are at little risk of PM10 violations would be useful. 

III. How did EPA develop the approach used in the LMP option?

The EPA has studied PM10 air quality data information for the entire country over the past

eleven years (1989-1999) and has determined that some moderate PM10 nonattainment areas have had

a history of low PM10 design values with very little inter-annual variation. When we looked at all the

monitoring sites reporting data for those years, the data indicate that most of the average design values

fall below 2 levels, 98 μg/m3 for the 24-hr PM10 NAAQS and 40 μg/m3 for the annual PM10 NAAQS. 

For most monitoring sites these levels are also below their individual site-specific critical design values

(CDV). The CDV is an indicator of the likelihood of future violations of the NAAQS given the current

average design value and its variability. The CDV is the highest average design value an area could

have before it may experience a future exceedance of the NAAQS with a certain probability. A

detailed explanation of the CDV is found in Attachment A3 to this policy which, because of its length, is

a separate document accompanying this memorandum. 

We believe that the very small amount of variation between the peaks and means in most of the

data indicates a very stable relationship that can be reasonably expected to continue in the future absent

any significant changes in emissions. The period we assessed provides a fairly long historical record

and the data could therefore be expected to have been affected by a full range of meteorological

conditions over the period. Therefore, the amount of emissions should be the only variable that could

affect the stability in the air quality data. We believe we can reliably make estimates about the future

variability of PM10 concentrations across the country based on our statistical analysis of this data

record, especially in areas where the amount of emissions is not expected to change. 

IV. How do I qualify for the LMP option ?
3

 

4The methods for calculating design values for PM10 are presented in a document entitled the “PM10 SIP Development

Guideline”, EPA-450/2-86-001, June 1987. The State should determine the most appropriate method to use from this Guideline

in consultation with the appropriate EPA Regional office staff.

 

5

If the EPA determines that the meteorology was not representative during the most recent five-year period, we may

reject the State’s request to use the LMP option and request, instead, submission of a full maintenance demonstration.

To qualify for the limited maintenance plan option, an area should meet the following 

applicability criteria. The area should be attaining the NAAQS and the average PM10 design value4 for

the area, based upon the most recent 5 years of air quality data at all monitors in the area, should be at

or below 40 μg/m3 for the annual and 98 μg/m3 for the 24-hr PM10 NAAQS with no violations at any

monitor in the nonattainment area5. If an area cannot meet this test it may still be able to qualify for the

LMP option if the average design values of the site are less than their respective site-specific CDV. 

We believe it is appropriate to offer this second method of qualifying for the LMP because,

based on the air quality data we have studied, we believe there are some monitoring sites with average

design values above 40 μg/m3 or 98 μg/m3, depending on the NAAQS in question, that have

experienced little variability in the data over the years. When the CDV calculation was performed for

these sites we discovered that their average design values are less than their CDVs, indicating that the

areas have a very low probability (1 in 10) of exceeding the NAAQS in the future. We believe it is

appropriate to provide these areas the opportunity to qualify for the LMP in this circumstance since the

40 μg/m3 or 98 μg/m3 criteria are based on a national analysis and don’t take into account each local

situation.

The final criterion is related to mobile source emissions. The area should expect only limited

growth in on-road motor vehicle PM10 emissions (including fugitive dust) and should have passed a

motor vehicle regional emissions analysis test. It is important to consider the impact of future

transportation growth in the LMP, since the level of PM-10 emissions (especially from fugitive dust) is

related to the level of growth in vehicle miles traveled (VMT). Attachment B (below) should be used

for making the motor vehicle regional emissions analysis demonstration. 

If the State determines that the area in question meets the above criteria, it may select the LMP

option for the first 10 year maintenance period. Any area that does not meet these criteria should plan

to submit a full maintenance plan that is consistent with our guidance in the Calcagni Memo in order to

be redesignated to attainment. If the LMP option is selected, the State should continue to meet the

qualifying criteria until EPA has redesignated the area to attainment. If an area no longer qualifies for

the LMP option because a change in air quality affects the average design values before the

redesignation takes effect, the area will be expected to submit a full maintenance plan. 

Once an area selects the LMP option and it is in effect, the State will be expected to recalculate

the average design value for the area annually and determine if the criteria used to qualify for the LMP
4

will still be met. If, after performing the annual recalculation of the area’s average design value in a

given year, the State determines that the area no longer qualifies for the LMP, the State should take

action to attempt to reduce PM10 concentrations enough to requalify for the LMP. One possible

approach the State could take is to implement a contingency measure or measures found in its SIP. If,

in the next annual recalculation the State is able to re-qualify for the LMP, then the LMP will go back

into effect. If the attempt to reduce PM10 concentrations fails, or if it succeeds but in future years it

becomes necessary again to address increasing PM10 concentrations in the area, that area no longer

qualifies for the LMP. We believe that repeated increases in PM10 concentrations indicate that the initial

conditions that govern air quality and that were relied on to determine the area’s qualification for the

LMP have changed, and that maintenance of the NAAQS can no longer be assumed. Therefore, the

LMP cannot be reinstated by further recalculations of the design values at this point. Once the LMP is

determined to no longer be in effect, a full maintenance plan should be developed and submitted within

18 months of the determination. 

Treatment of data used to calculate the design values.

Flagged Particulate Matter Data:

Three policies allow PM-10 data to be flagged for special consideration:

 

• Exceptional Events Policy (1986) for data affected by infrequent events

such as industrial accidents or structural fires near a monitoring site;

• Natural Events Policy (1996) for data affected by wildfires, high winds,

and volcanic and seismic activities, and;

• Interim Air Quality Policy on Wildland and Prescribed Fires for data

affected by wildland fires that are managed to achieve resource

benefits.

We will treat data affected by these events consistently with these previouslyissued policies. We expect States to consider all data (unflagged and flagged)

when determining the design value. The EPA Regional offices will work with

the State to determine the validity of flagged data. Flagged data may be

excluded on a case-by-case basis depending on State documentation of the

circumstances justifying flags. Data flagged as affected by exceptional or

natural events will generally not be used when determining the design value. 

However, in order for data affected by a natural event to be excluded, an

adequate Natural Events Action Plan is required as described in the Natural

Events policy.

Data flagged as affected by wildland and prescribed fires will be used in

determining the design value. If the State is addressing wildland and prescribed

fire use with the application of smoke management programs, the State may
5

submit an LMP if the design value is too high only as a result of the fire-affected

data.

We are in the process of developing a policy to address agricultural burning.

When it is finalized we will amend the LMP option to account for the new

policy. 

V. What should an LMP consist of?

Under the LMP, we will continue to satisfy the requirements of Section 107(d)(3)(E) of the Act

which provides that a nonattainment area can be redesignated to attainment only if the following criteria

are met:

1. The EPA has determined that the NAAQS for the applicable pollutant has been 

attained.

2. The EPA has fully approved the applicable implementation plan under section 110(k).

3. The EPA has determined that the improvement in air quality is due to permanent 

and enforceable reductions in emissions.

4. The State has met all applicable requirements for the area under section 110 and part

D.

5. The EPA has fully approved a maintenance plan, including a contingency plan, for the

area under section 175A.

However, there are some differences between what our previous guidance (the Calcagni

memo) recommends that States include in a maintenance plan submission and what we are

recommending under this policy for areas that qualify for the LMP. The most important difference is

that under the LMP the demonstration of maintenance is presumed to be satisfied. The following is a

list of core provisions which should be included in an LMP submission. Note that any final EPA

determination regarding the adequacy of an LMP will be made following review of the plan submitted in

light of the particular circumstances facing the area proposed for redesignation and based upon all

available information.

a. Attainment Plan

The State’s approved attainment plan should include an emissions inventory (attainment

inventory) which can be used to demonstrate attainment of the NAAQS. The inventory should

represent emissions during the same five-year period associated with the air quality data used to

determine whether the area meets the applicability requirements of this policy (i.e., the most recent five

years of air quality data). If the attainment inventory year is not one of the most recent five years, but

the State can show that the attainment inventory did not change significantly during that five-year period,

it may still be used to satisfy the policy. If the attainment inventory is determined to not be

representative of the most recent 5 years, a new inventory must be developed. The State should
6

review its inventory every three years to ensure emissions growth is incorporated in the attainment

inventory if necessary. 

b. Maintenance Demonstration 

The maintenance demonstration requirement of the Act will be considered to be satisfied for the

moderate PM10 nonattainment areas meeting the air quality criteria discussed above. If the tests

described in Section IV are met, we will treat that as a demonstration that the area will maintain the

NAAQS. Consequently, there is no need to project emissions over the maintenance period. 

c. Important elements that should be contained within the redesignation request

1. Monitoring Network Verification of Continued Attainment

To verify the attainment status of the area over the maintenance period, the

maintenance plan should contain a provision to assure continued operation of an

appropriate, EPA-approved air quality monitoring network, in accordance with

40 CFR part 58. This is particularly important for areas using an LMP because

there will be no cap on emissions.

2. Contingency Plan

Section 175A of the Act states that a maintenance plan must include

contingency provisions, as necessary, to promptly correct any violation of the

NAAQS which may occur after redesignation of the area to attainment. These

contingency measures do not have to be fully adopted at the time of

redesignation. However, the contingency plan is considered to be an

enforceable part of the SIP and the State should ensure that the contingency

measures are adopted as soon as possible once they are triggered by a specific

event. The contingency plan should identify the measures to be adopted, and

provide a schedule and procedure for adoption and implementation of the

measures if they are required. 

Normally, the implementation of contingency measures is triggered by a

violation of the NAAQS but the State may wish to establish other triggers to

prevent a violation of the NAAQS, such as an exceedance of the NAAQS.
7

3. Approved attainment plan and section 110 and part D CAA requirements:

In accordance with the CAA, areas seeking to be redesignated to attainment

under the LMP policy must have an attainment plan that has been approved by

EPA, pursuant to section 107(d)(3)(E). The plan must include all control

measures that were relied on by the State to demonstrate attainment of the

NAAQS. The State must also ensure that the CAA requirements for PM10

pursuant to section 110 and part D of the Act have been satisfied. To comply

with the statute, the LMP should clearly indicate that all controls that were

relied on to demonstrate attainment will remain in place. If a State wishes to

roll back or eliminate controls, the area can no longer qualify for the LMP and

the area will become subject to full maintenance plan requirements within 18

months of the determination that the LMP is no longer in effect.

V. How is Conformity treated under the LMP option?

The transportation conformity rule (40 CFR parts 51 and 93) and the general conformity rule

(58 FR 63214; November 30, 1993) apply to nonattainment areas and maintenance areas operating

under maintenance plans. Under either conformity rule one means of demonstrating conformity of

Federal actions is to indicate that expected emissions from planned actions are consistent with the

emissions budget for the area. Emissions budgets in LMP areas may be treated as essentially not

constraining for the length of the maintenance period because it is unreasonable to expect that an area

satisfying the LMP criteria will experience so much growth during that period of time such that a

violation of the PM10 NAAQS would result. While this policy does not exempt an area from the need

to affirm conformity, it does allow the area to demonstrate conformity without undertaking certain

requirements of these rules. For transportation conformity purposes, EPA would be concluding that

emissions in these areas need not be capped for the maintenance period, and, therefore, a regional

emissions analysis would not be required. Similarly, Federal actions subject to the general conformity

rule could be considered to satisfy the “budget test” specified in section 93.158 (a)(5)(i)(A) of the rule,

for the same reasons that the budgets are essentially considered to be unlimited.

EPA approval of an LMP will provide that if the LMP criteria are no longer satisfied and a full

maintenance plan must be developed to meet CAA requirements (see Calcagni Memo referenced in

footnote #2 for full maintenance plan guidance), the approval of the LMP would remain applicable for

conformity purposes only until the full maintenance plan is submitted and EPA has found its motor

vehicle emissions budgets adequate for conformity purposes under 40 CFR parts 51 and 93. EPA will

condition its approval of all LMPs in this fashion because in the case where the LMP criteria are not

met and a full maintenance plan is required EPA believes that LMPs would no longer be an appropriate

mechanism for assuring maintenance of the standards.

For further information concerning the LMP option for moderate PM10 areas please contact
8

Gary Blais at (919) 541-3223, or for questions about the CDV approach contact Dr. Shao-Hang Chu

at (919) 541-5382. For information concerning transportation conformity requirements, please contact

Meg Patulski of the Office of Transportation and Air Quality at (734) 214-4842. 
9

OAQPS/AQSSD/IPSG:GBlais:NPerry,x5628

G:\user\share\nrpfiles\wpfiles\beal\LMP.wpd
ATTACHMENT B: 

MOTOR VEHICLE REGIONAL ANALYSIS METHODOLOGY

The following methodology is used to determine whether increased emissions from on-road mobile

sources could, in the next 10 years, increase concentrations in the area and threaten the assumption of

maintenance that underlies the LMP policy. This analysis must be submitted and approved in order to

be eligible for the LMP option.

The following equation should be used:

DV + (VMTpi x DVmv) # MOS

Where:

DV = the area’s design value based on the most recent 5 years of quality

assured data in μg/m3

 VMTpi= the projected % increase in vehicle miles traveled (VMT) over the next

10 years

DVmv = motor vehicle design value based on on-road mobile portion of the

attainment year inventory in μg/m3

MOS = margin of safety for the relevant PM-10 standard for a given area: 40

μg/m3 for the annual standard or 98 μg/m3 for the 24-hour standard 

Please note that DVmv is derived by multiplying DV by the percentage of the attainment year inventory

represented by on-road mobile sources. This variable should be based on both primary and secondary

PM10 emissions of the on-road mobile portion of the attainment year inventory, including re-entrained

road dust.

States should consult with EPA regarding the three inputs used in the above calculation, and all EPA

comments and concerns regarding inputs and results should be addressed prior to submitting a limited

maintenance plan and redesignation request. 

The VMT growth rate (VMTpi) should be calculated through the following methods:

1) an extrapolation of the most recent 10 years of Highway Performance Monitoring System (HPMS)

data over the 10-year period to be addressed by the limited maintenance plan; and 

2) a projection of VMT over the 10-year period that would be covered by the limited maintenance

plan, using whatever method is in practice in the area (if different than #1). 

Areas where method #1 is the current practice for calculating VMT do not also have to do calculation

#2, although this is encouraged. All other areas should use methods #1 and #2, and VMTpi is
2

whichever growth rate produced by methods #1 and #2 is highest. Areas will be expected to use

transportation models for method #2, if transportation models are available. Areas without

transportation models should use reasonable professional practice. 

Examples

1. DV = 80 μg/m3

VMTpi = 36%

DVmv = 30 μg/m3

MOS = 98 μg/m3 for 24-hour PM-10 standard

80 + (.36 * 30) = 91 

Less than 98 – Area passes regional analysis criterion.

2. DV = 35 μg/m3

VMTpi = 25%

DVmv = 6 μg/m3

MOS = 40 μg/m3 for annual PM-10 standard

35 + (.25 * 6) = 37 

Less than 40 – Area passes regional analysis criterion.

3. DV = 115 μg/m3

VMTpi = 25%

DVmv = 60 μg/m3

MOS = 98 μg/m3 for 24-hour PM-10 standard

115 + (.25 * 60) = 130

More than 98 – Area does not pass criterion. Full section 175A maintenance plan required. 
ATTACHMENT 4 
STATE OF NEW HAMPSHIRE 

DEPARTMENT OF ENVIRONMENTAL SERVICES 

AIR RESOURCES DIVISION 

CONCORD, NH 

NOTICE OF PROPOSED REVISIONS TO THE STATE IMPLEMENTATION PLAN 

In accordance with N.H. Administrative Rule Env-A 204.01 and 40 CFR § 

51.102, notice is hereby given that the New Hampshire Department of Environmental 

Services, Air Resources Division (DES), intends to submit for the approval of the U.S. 

Environmental Protection Agency (EPA) the following proposed revisions to the New 

Hampshire State Implementation Plan (SIP) required by the federal Clean Air Act: 

• Replace New Hampshire’s existing Carbon Monoxide Maintenance Plan with the 

proposed Carbon Monoxide Limited Maintenance Plan for the City of Manchester 

and the City of Nashua Carbon Monoxide Maintenance Areas. 

• Discontinue monitoring Carbon Monoxide (CO) at the Manchester site and rely 

instead on data from the Londonderry Moose Hill monitoring station and NH 

emissions inventory. 

When an area (in this case Manchester and Nashua) that was previously designated as 

nonattainment for any of the pollutants for which EPA has established National Ambient 

Air Quality Standards (NAAQS) applies for redesignation to attainment status, the 

federal Clean Air Act requires DES to submit a maintenance plan as part of the 

redesignation request. This plan shows how the area will stay in attainment for the 

subsequent 10 years, and what steps DES will take if it does not. DES filed a 

maintenance plan for CO with EPA on December 3, 1998, and revised it in 2007. 

Over time, the CO levels in downtown Manchester and Nashua have decreased to the 

point that a future exceedance of the federal standards for CO is highly unlikely. In 

addition to the downward CO trend shown by monitoring data, the state has performed 

mobile source modeling and conformity analyses indicating low CO levels in Manchester 

and Nashua as far into the future as 2035, beyond the end of the maintenance plan. 

Therefore, DES is submitting a CO Limited Maintenance Plan that will discontinue CO 

monitoring in Manchester, instead relying on a CO monitoring station in Londonderry, 

mid-way between Manchester and Nashua, with contingency plans to reinstate 

monitoring in Manchester if CO concentrations rise to 50 percent of the NAAQS. 

Copies of all documentation pertaining to the proposed SIP revision are available for 

inspection online at: http://des.nh.gov/ under “Hot Topics”. The documents are also 

available for review at the DES offices at 29 Hazen Drive, Concord, N.H. Questions 

regarding the proposed SIP Revision or requests to view the documents should be 

directed to Paul Lockwood at (603) 271-5552 or paul.lockwood@des.nh.gov . 

The public is invited to submit written comments on the proposal, and DES will hold a 

public hearing if one is requested by July 23, 2012. Written comments and/or any 
requests for a public hearing filed and received no later than 4 p.m. on July 23, 2012, 

shall be considered by DES in making a final decision. Please submit comments or a 

request for hearing to Paul Lockwood, Transportation Analyst, PO Box 95, Concord, NH 

03302-0095, Fax (603) 271-7053, or to paul.lockwood@des.nh.gov. 

Thomas S. Burack 

Commissioner 

NH Department of Environmental Services 

Dated: June 23, 2012 
ATTACHMENT 5