December 2009 Revision to Lowell COMaintenance Plan

Response to Comments Page 1 of 7 

### RESPONSE TO COMMENTS In November 2008, MassDEP issued for public reviewand 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 COmonitoring 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 from19 residents and public officials fromnearby 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 ofHealth, 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 WilliamF. 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 SIPrevision is at : www .mass.gov/dep/air/priorities/sip.htm#coDecember 2009 Revision to Lowell COMaintenance 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 COmonitoring is needed to protect public health in the Lowell area. Commenters are concerned that removal of the Lowell COmonitor would result in the loss of data needed to track ambient COlevels in Lowell and other communities in the Merrimack Valley. Response: MassDEPappreciates 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 COare 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 COmonitor in Lowell showed violations of the 8-hour COstandard. No violations of the 1-hour COstandard have been recorded in Lowell . The last violation of the 8-hour standard in Lowell was in 1984. Since then, monitored COlevels at the Lowell site have continued to decline to well below the NAAQS.2 MassDEPoperates three additional COmonitors located in Boston (Kenmore Square), Worcester, and Springfield. COlevels at these monitors are also well below both NAAQS for CO

. COis the only pollutant measured at the Lowell monitor, unlike the other COmonitoring 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 COmonitor. In a time ofbudget 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 maximum8-hour concentration . In 2007, the 2"d maximumin Lowell was 1 .6 ppm ; in 2008, it was 2.1 ppm, which is approximately 20%ofthe 8-hour 9.0 ppm standard. The maximum8-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 minimummonitoring requirements for CO . (See 71 Federal Register 61250 and 71 Federal Register 61301 .)December 2009 Revision to Lowell COMaintenance 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, MassDEPexpects 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 fromexisting 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: COis largely a mobile source based pollutant . (See Figure 1 below .) The highest on-road motor vehicle COemissions 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 COconcentrations, as COdisperses quickly. All of the COmonitors in Massachusetts are located in congested urban locations where the highest COconcentrations are anticipated. Highway traffic generally creates far less COemissions than slower traffic conditions. As discussed in the Proposed Lowell SIP Revision, the significant decrease in COconcentrations at each of the monitors in Massachusetts over the years is largely the result of reductions in CO emissions frommotor vehicles. Despite steady increases in population, economic development, and vehicle miles travelled, emissions of CO (and other pollutants) frommotor 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, COemissions fromon-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 ofthese on-road mobile source control programs .December 2009 Revision to Lowell COMaintenance Plan

Response to Comments Page 4 of 7 In Massachusetts, COemissions fromlarge 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 fromthe facility will cause or contribute to a violation of a NAAQS . Anticipated emissions froma 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. MassDEPdetermined that COemissions fromthe facility will not cause or contribute to a violation of the CONAAQS. Arequirement of the Conditional Approval is that stack emissions of CO, ammonia and nitrogen oxides fromthe 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 COemissions from this facility will not exceed allowable limits. Furthermore, it is highly unlikely that COemissions from elevated stacks would impact ground levels of CObecause 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, MassDEPwill require a demonstration that the facility will not cause or contribute to the violation of a NAAQS.

6 Because COemissions and concentrations generally are highest in colder temperatures, estimates are for a typical winter day. 7 The COemission limits for the facility include a CO limit of 38.6 tons per 12-month rolling period. By comparison, the annual COemissions for 2005 in Middlesex County fromon-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 COMaintenance Plan

Response to Comments Page 5 of 7 Figure 1

MASSACHUSETTS 2005 CO ESTIMATED

EMISSIONS (4,685 Tons perwinter day)

Off-Road Mobile 17%

Area 23% Stationary Point

1% On-Road Mobile 59%

Estimates are fromthe Massachusetts 2005 Periodic Emissions Inventory. http://www

.mass.gov/dep/air/priorities/addata .htm ) C . The Worcester COmonitor as a surrogate for Lowell Commenters questioned the suitability of using data fromthe 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 COconcentrations in Lowell for both the 1-hour and 8-hour average have increased over the past 2years at a higher rate than in Worcester. Response: For purposes of monitoring COconcentrations, 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 COlevels for Lowell and Worcester for this time period have a correlation coefficient of 0.86. The average 2°d high 8-hour COlevel for this period for Lowell is 4 .9 ppm ; for Worcester it is 4.8 ppm . The strong correlation ofmonitored COlevels in the two cities demonstrates that the Worcester monitor is an adequate surrogate for LowellDecember 2009 Revision to Lowell COMaintenance 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 COstandards, 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 COLevels 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 COLevels 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 StdDecember 2009 Revision to Lowell COMaintenance Plan

Response to Comments Page 7 of 7

D . Estimates of CO Emissions The EPAsubmitted comments agreeing with MassDEP's proposal . EPAalso 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 fromemission levels included in the 2001 Maintenance Plan for these cities. Response: MassDEPappreciates 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 COemissions 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, MassDEPdeveloped 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 EPAmobile models to estimate mobile source emissions and adopted revised methodologies for estimating emissions fromother 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 COemissions frommobile and other sources in the Proposed Lowell SIP Revision MassDEPis required to submit to EPAa 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 CONAAQS for an additional ten years after the ten-year 2001 Maintenance Plan expires in 2011 . In that second maintenance plan, MassDEPwill provide revised estimates of COemissions 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