December 2009 Revision to Lowell CO Maintenance Plan 

Response to Comments 

Page 1 of 7 

RESPONSE TO COMMENTS 

In November 2008, MassDEP issued for public review and comment a proposed revision to 

the Massachusetts Carbon Monoxide (CO) Maintenance State Implementation Plan (SIP) for 

the City of Lowell (Proposed Lowell SIP revision)'. In the Proposed Lowell SIP revision, 

MassDEP proposed to discontinue CO monitoring in Lowell and to use data from the 

Worcester monitor as a surrogate for purposes of determining when contingency control 

measures must be implemented under the SIP. 

MassDEP received comments from 19 residents and public officials from nearby 

communities opposing the proposal and one comment in support of the proposal. MassDEP 

has categorized and summarized the comments and provides its responses below. 

COMMENTERS: 

1 . Nicholas Waggener - N.Billerica 

2. Piage Impink - Tewksbury 

3 . 

4. 

5 . 

6. 

7. 

8. 

9. 

10. 

11 . 

12. 

Leo Manning - Chelmsford 

Rebecca Clarke & Thomas Hostage - N.Billerica 

Karyn Sliva - Tewksbury 

Lou-Ann Clement - Board of Health, Tewksbury 

Rep. James R. Miceli, 19 Middlesex District - Tewksbury and Wilmington 

Mary Anne Kochenderfer - Chelmsford 

Greg Eakman - Billerica 

Christine Kinnon -Board of Health, Tewksbury 

Caroline Ahdab - Pepperell 

William F. Williams - Town Manager, Billerica 

13. Robert M. Correnti - Selectman, Town of Billerica 

14. Geraldine E. Foskitt - N.Billerica 

15. Helena Pisetsky - Billerica 

16. Jeanne Landers - Billerica 

17. Lynn Santos, Consultant for Edward Camplese of the Billerica Watchers Group 

18. U.S . Environmental Protection Agency (EPA) Region 1, Boston -Anne Arnold, Manager, 

Air Quality Planning Unit 

19. State Senator Steven C. Panagiotakos 

'The Proposed Lowell SIP revision is at : www.mass.gov/dep/air/priorities/sip .htm#co 
December 2009 Revision to Lowell CO Maintenance Plan 

Response to Comments 

Page 2 of 7 

Summary of Comments Received and MassDEP Responses 

A. Public Health Impacts of CO 

Commenters stated that continued CO monitoring is needed to protect public health in the 

Lowell area. Commenters are concerned that removal of the Lowell CO monitor would 

result in the loss of data needed to track ambient CO levels in Lowell and other 

communities in the Merrimack Valley . 

Response: 

MassDEP appreciates the concerns of residents of Lowell and surrounding towns who have a 

strong interest in protecting public health in their communities. Protecting public health and 

maintaining air quality is fundamental to MassDEP's mission. In order to protect public health, 

the U.S . Environmental Protection Agency (EPA) sets National Ambient Air Quality Standards 

(NAAQS) for the most pervasive air pollutants . MassDEP must insure that air quality in 

Massachusetts meets the NAAQS. 

The NAAQS for CO are 9 .0 parts per million (ppm) averaged over eight-hours, and 35 .0 ppm 

averaged over one-hour. In the 1970s and early 1980s, measurements at the CO monitor in 

Lowell showed violations of the 8-hour CO standard . No violations of the 1-hour CO standard 

have been recorded in Lowell. The last violation of the 8-hour standard in Lowell was in 1984 . 

Since then, monitored CO levels at the Lowell site have continued to decline to well below the 

NAAQS.2 MassDEP operates three additional CO monitors located in Boston (Kenmore 

Square), Worcester, and Springfield. CO levels at these monitors are also well below both 

NAAQS for CO . 

CO is the only pollutant measured at the Lowell monitor, unlike the other CO monitoring 

locations where MassDEP measures multiple pollutants . Maintaining this single-pollutant 

monitor at a location where there have been no violations of the health-based NAAQS for over 

25 years does not provide meaningful public health protection. 3 MassDEP expends substantial 

resources to operate and maintain the Lowell CO monitor. In a time of budget constraints, 

MassDEP must focus its monitoring resources on pollutants and locations where there is a 

greater likelihood of elevated pollutant concentrations and associated public health impacts. 

Z Compliance with the NAAQS is based on the 2°d maximum 8-hour concentration . In 2007, the 2"d 

maximum in Lowell was 1 .6 ppm; in 2008, it was 2.1 ppm, which is approximately 20% of the 8-hour 9.0 

ppm standard . The maximum 8-hour concentration in 2007 was 2.1 ; in 2008 it was 2 .6 ppm. 

See Figures 2 and 3 on page 6. 

3 The U .S . EPA has explicitly recognized that where measured levels of pollutants are low, shutting down 

monitors may be allowed . On October 17, 2006, EPA published a final monitoring rule revising the 

minimum monitoring requirements for CO . (See 71 Federal Register 61250 and 71 Federal Register 

61301 .) 
December 2009 Revision to Lowell CO Maintenance Plan 

Response to Comments 

Page 3 of 7 

There are three air quality monitoring sites in the Merrimack Valley where MassDEP measures 

multiple air pollutants . These sites and the pollutants measured are : Lawrence (ozone, sulfur 

dioxide and fine particulate matter (PM 2.5)) ; Haverhill (PM 2.5); and Newbury (ozone, nitrogen 

oxides and PAMS4). These other monitors will continue to provide a comprehensive indicator of 

overall air quality in the Lowell and Merrimack Valley . 

MassDEP reviews its state-wide air quality monitoring network annually. During its next review, 

MassDEP expects to examine the existing statewide PM2.5 network to assess the potential for 

additional PM 2.5 monitors in various locations including Merrimack Valley . However, the 

deployment of any new monitors will be dependent on the resources available to support the 

overall monitoring program. 

B. Sources of CO Emissions 

Commenters are concerned about the potential public health impacts of additional CO 

emissions from existing and proposed new power plants, nearby highways (Routes 3, 495 

and 93) and industrial, commercial, and residential development in the densely populated 

Lowell area. The Montgomery L'Energia Lowell Power Plant installation and the 

proposed Billerica Energy Center peaking power plant in Billerica are of particular 

concern to the commenters. 

Response: 

CO is largely a mobile source based pollutant. (See Figure 1 below.) The highest on-road motor 

vehicle CO emissions occur when vehicles idle during congested traffic, generally around city 

centers. CO monitors must be located close to areas of congested traffic in order to measure the 

highest CO concentrations, as CO disperses quickly. All of the CO monitors in Massachusetts 

are located in congested urban locations where the highest CO concentrations are anticipated. 

Highway traffic generally creates far less CO emissions than slower traffic conditions . 

As discussed in the Proposed Lowell SIP Revision, the significant decrease in CO concentrations 

at each of the monitors in Massachusetts over the years is largely the result of reductions in CO 

emissions from motor vehicles . Despite steady increases in population, economic development, 

and vehicle miles travelled, emissions of CO (and other pollutants) from motor vehicles have 

been significantly reduced due to the adoption of state and federal mobile source control 

requirements . s These reductions have taken place in all counties in Massachusetts . As cleaner, 

newer vehicles replace older cars and trucks, CO emissions from on-road vehicles will continue 

to decrease. 

4 PAMS is a special designation for enhanced monitoring stations that are designed to gather information on the 

ozone formation process. For additional information see the MassDEP Annual Air Quality Reports at : 

www.mass.gov/dep/air/priorities/aqreports .htm#aqrept 

5 See the Proposed SIP revision, Footnote 1, (www.mass. og v/dep/air/priorities/sip.htm#co) for a list of these on-road 

mobile source control programs . 
December 2009 Revision to Lowell CO Maintenance Plan 

Response to Comments 

Page 4 of 7 

In Massachusetts, CO emissions from large stationary industrial sources ("stationary point 

sources"), including power plants, comprise less than 1 % of the estimated 2005 statewide CO 

winter day emissions inventory . b Furthermore, MassDEP does not issue an approval for the 

construction and operation of a new or modified facility if emissions from the facility will cause 

or contribute to a violation of a NAAQS. Anticipated emissions from a proposed facility, along 

with background pollutant estimates, are analyzed as part of a NAAQS compliance 

demonstration. 

In 2008, MassDEP issued to Montgomery L'Energia Power Partners LP a Conditional 

Approval for an 85 megawatt (MW) combined cycle peaking electric generating facility in Lowell. 

The facility submitted a NAAQS compliance demonstration as part of the approval process . 

MassDEP determined that CO emissions from the facility will not cause or contribute to a 

violation of the CO NAAQS. A requirement of the Conditional Approval is that stack emissions 

of CO, ammonia and nitrogen oxides from the facility be monitored and recorded by continuous 

emissions monitoring systems (CEMS) to determine compliance status with the emission limits 

for these pollutants . 

7 This monitoring requirement provides assurance that CO emissions from this 

facility will not exceed allowable limits . Furthermore, it is highly unlikely that CO emissions from 

elevated stacks would impact ground levels of CO because of dispersion. Billerica Energy 

Center, a 348-megawatt peaking plant, has been proposed for North Billerica but the project is on 

hold as of late 2009. If the project goes forward, MassDEP will require a demonstration that the 

facility will not cause or contribute to the violation of a NAAQS. 

6 Because CO emissions and concentrations generally are highest in colder temperatures, estimates are for a typical 

winter day. 

7 The CO emission limits for the facility include a CO limit of 38 .6 tons per 12-month rolling period. By comparison, 

the annual CO emissions for 2005 in Middlesex County from on-road motor vehicles are estimated to be more than 

175,000 tons . See Massachusetts 2005 Periodic Emissions Inventory : 

http ://www.mass. og v/dep/air/priorities/aqdata .htm ) 
December 2009 Revision to Lowell CO Maintenance Plan 

Response to Comments 

Page 5 of 7 

Figure 1 

MASSACHUSETTS 2005 CO ESTIMATED 

EMISSIONS (4,685 Tons per winter day) 

Off-Road Mobile 

17% 

Area 

23% 

Stationary Point 

1% 

On-Road Mobile 

59% 

Estimates are from the Massachusetts 2005 Periodic Emissions Inventory. 

http://www.mass.gov/dep/air/priorities/addata .htm) 

C. The Worcester CO monitor as a surrogate for Lowell 

Commenters questioned the suitability of using data from the Worcester monitor as a 

surrogate for Lowell, noting that Worcester is 40 miles away and that the Worcester area 

has a lower population density than Lowell and the Merrimack Valley. One commenter 

(#17) noted that the maximum CO concentrations in Lowell for both the 1-hour and 8-hour 

average have increased over the past 2 years at a higher rate than in Worcester. 

Response: 

For purposes of monitoring CO concentrations, a high traffic location in Worcester is an 

appropriate surrogate for a high traffic location in Lowell. Worcester is a larger city 

(pop. 175,454) with significantly higher economic activity and vehicular traffic than Lowell (pop. 

103,229), and the Worcester monitor is located at a high-traffic site . 

CO monitoring data from 1983 to 2008 for both Lowell and Worcester show that CO 

concentrations have compared very closely . The 2"d high 8-hour CO levels for Lowell and 

Worcester for this time period have a correlation coefficient of 0 .86 . The average 2°d high 8-hour 

CO level for this period for Lowell is 4.9 ppm; for Worcester it is 4.8 ppm. The strong 

correlation of monitored CO levels in the two cities demonstrates that the Worcester monitor is 

an adequate surrogate for Lowell 
December 2009 Revision to Lowell CO Maintenance Plan 

Response to Comments 

Page 6 of 7 

Furthermore, as demonstrated in Figures 2 and 3 below, the concentrations at both monitors are 

so significantly below the 1-hour and 8-hour CO standards, that a higher rate of increase in the 1-

hour and 8-hour maximums in Lowell in 2007 and 2008 is not a meaningful metric . 

Figure 2 

c 

0 

a 

a 

Maxirrxim 1-Hr CO Levels in Low ell and Worcester 

NAAQS = 35 PPM 

40.0 

35.0 

30.0 ~ 

0.0 ~ 

5.0 - 

25.0 

20.0 

15.0 

10.0 

-~- Low ell 

--s-- Worc20 

Worc22 

Worc23 

1-Hr Std 

Figure 3 

c 0 

a) a 

a - 

Maximum 8-Hr CO Levels in Low ell and Worcester 

NAAQS = 9.0 PPM 

10 .0 

9.0 

8 .0 

7.0 

6.0 

5.0 

4.0 

3.0 

2.0 

1 .0 

0.0 

OP m O 

m m O 

m m 

No 

O 

O 

N 

(V C? +t LO SD r+~ m 

O O O O O O Q 

(D O O O O [] O 

N N N N N N CV 

-+- Low ell 

--w-- Worc20 

Worc22 

Worc23 

-)K - 8-Hr Std 
December 2009 Revision to Lowell CO Maintenance Plan 

Response to Comments 

Page 7 of 7 

D. Estimates of CO Emissions 

The EPA submitted comments agreeing with MassDEP's proposal. EPA also commented 

that MassDEP should provide additional information on the source of its emission 

estimates and projections for Lowell and Worcester (page 5 of the Proposed Lowell SIP 

Revision), noting that the estimates differ significantly from emission levels included in the 

2001 Maintenance Plan for these cities . 

Response: 

MassDEP appreciates EPA's comments agreeing with the proposal to shut down the Lowell 

monitor and to use Worcester monitor data as a surrogate. 

EPA notes correctly that the CO emissions estimates in the 2001 Maintenance Plan differ from 

those in the Proposed Lowell SIP Revision. The 2001 Maintenance Plan estimates of CO 

emissions for 1996 and 2012 were developed using the methods and models that were current at 

the time the 2001 Maintenance Plan was developed and were based on the Massachusetts 1996 

Periodic Emissions Inventory. 

Subsequent to preparation of the 2001 Maintenance Plan, MassDEP developed the 

Massachusetts 2002 Base Year Emission Inventory and the 2005 Periodic Emissions Inventory. g 

In the 2002 and 2005 emissions inventories, MassDEP used the latest EPA mobile models to 

estimate mobile source emissions and adopted revised methodologies for estimating emissions 

from other source categories . Methods of projecting emissions to future years have also been 

revised since MassDEP developed the 2001 Maintenance Plan. MassDEP used these updated 

emission estimates and methods to illustrate trends in CO emissions from mobile and other 

sources in the Proposed Lowell SIP Revision 

MassDEP is required to submit to EPA a second maintenance plan for Lowell eight years after 

EPA's 2002 redesignation of Lowell to attainment . The second maintenance plan will need to 

provide for maintenance of the CO NAAQS for an additional ten years after the ten-year 2001 

Maintenance Plan expires in 2011 . In that second maintenance plan, MassDEP will provide 

revised estimates of CO emissions as of the plan submission date and projected emissions for a 

future maintenance year. 

$ The Massachusetts emissions inventories are at : http ://mass. ov/dep/air/priorities/aqdata .htm