Page 1 of 2 

New Hampshire Regional Haze SIP Revision 

Responses to Sierra Club’s Comments 

On November 22, 2010, the New Hampshire Department of Environmental Services (NHDES) 

received comments in a letter from Attorney Arthur B. Cunningham, representing the New 

Hampshire Sierra Club, on New Hampshire’s proposed rule Chapter Env-A 2300 Mitigation of 

Regional Haze. These comments were resubmitted on December 20, 2010. Below, NHDES 

responds to specific comments contained in that letter. Comments are written in italics and 

responses are written in regular font.

Comment: You have determined that the July 17, 1998, NOx RACT Order for Merrimack 

Station MK2 satisfies the Regional Haze BART requirement. The 1998 NOx RACT Order 

requires that MK2 emit no more than 15.4 tons of NOx per each 24 hour calendar day. In the 

BART analysis, 15.4 tons per day equates to 0.37 lbs/MMBtu of NOx. NHSC rejects your 

determination that the MK2 RACT Order satisfies BART. [Footnote 1: .37 lbs/MMBtu is 

almost four times the presumptive .1 lbs/MMBtu BART emission limit set forth in 40 CFR 51, 

Appendix Y.] 

 NHDES Response: The presumptive NOx limit is not representative of the 

performance capabilities of Unit MK2, for reasons explained in the BART analyses 

of the Regional Haze SIP, Attachment X. However, after receipt of new data from 

PSNH (see Attachment X), NHDES has determined that the appropriate BART 

emission limit for this unit is 0.30 lb/MMBtu, which is incorporated into the nowadopted rule as a maximum allowable emission rate to be measured on a 30-day 

rolling average basis. 

Comment: New Hampshire Department of Environmental Services-Air Resources Division 

(ARD) review of the Regional Haze BART requirement for Merrimack Station intersects with 

the legal necessity of ARD review of the New Hampshire nonattainment program, particularly 

for NOx, a major component of both regional haze and ozone. ARD is required by the Clean 

Air Act to timely establish a NOx emission limit for Merrimack Station MK2 that satisfies both 

the Regional Haze BART requirement and the nonattainment program. New Hampshire is 

delinquent in the establishment of both programs... 

The MK2 NOx emissions problem must be addressed in both the Regional Haze program and 

the nonattainment program. It makes no sense whatever to fix a 0.37 lbs/MMBtu BART 

emission limit for NOx knowing that a more stringent attainment NOx limit is due. 

 NHDES Response: NHDES acknowledges the need for review of the NOx RACT 

emission limit for Unit MK2. However, this review should be undertaken in the 

context of pending revisions to the National Ambient Air Quality Standards for 

ozone. It would be premature to issue a strengthened NOx RACT order for Unit 

MK2 before EPA has promulgated the revised standards and NHDES has 

considered the scope of emission reductions needed to meet those standards. On the 

other hand, there is an immediate need to establish a BART emission limit for Unit 

MK2. While the regional haze program must proceed without further delay, there 

exists no obligation to review nonattainment requirements for NOx in conjunction 

with the regional haze program or BART.
Page 2 of 2 

Comment: PSNH has increased the historic net generating capacity of MK2 from 320 MW to 

an ISO NE capacity claim of 338 MW. PSNH is currently operating MK2 at 332 MW...NHSC 

rejects the PSNH claim that the generation upgrade is entirely due to increased efficiency of 

the replaced MK2 turbine 2. ARD has failed to examine this generation upgrade and its impact 

on emissions.

 NHDES Response: Concerning work completed by PSNH during the 2008

Merrimack Station Unit MK2 outage (the MK2 Turbine Project), NHDES reviewed 

the proposed modification in accordance with its permitting requirements, including 

New Hampshire’s New Source Review program. NHDES’s decision on this 

permitting action was documented in a letter to Public Service of New Hampshire 

dated March 31, 2008, and references the provisions of 40 CFR 52.21(b)(21)(iv), 

commonly referred to as the “WEPCO Rule” Specific permitting actions are 

handled through the Department’s permitting programs and are not relevant to the 

BART analysis.

Comment: The MK2 SCR cannot be operated fulltime because of a temperature permissive. 

During start-ups, shutdowns and low load operations (below 230 MW net) the SCR cannot 

operate...PSNH asserts that the uncontrolled NOx rate is typically 1.0-1.5 lbs/MMBtu. PSNH, 

because of these concerns, insists that it needs "flexibility" to operate the SCR at a much higher 

emission limitation. [Footnote 3: Data contained in ARD files indicate that MK2 NOx removal 

is, on average, below the .37 lbs/MMBtu NOx RACT limit.] 

Existing ARD data does not support the PSNH claim that MK2 emits only 1.0-1.5 lbs/MMBtu 

during low load operations with the SCR shut down. ARD must examine the integrity of the 

PSNH low load emission claim because it is a critical part of the BART emission calculation as 

it exists in the proposed Regional Haze SIP...ARD must fix a NOx emission limit that fully 

accounts for the periods when the SCR is not in operation. 

 NHDES Response: In new data provided by PSNH (see Regional Haze SIP, 

Attachment X supporting documentation), the company applies an emission rate of 

0.8 lb/MMBtu during low-load operations for the calculation of NOx emissions, 30-

day rolling average. This value, which NHDES considers reasonable and conservative, 

was a factor in determining the BART emission limit of 0.30 lb/MMBtu.

Comment: PSNH, in its confidential submissions to ARD ordered released by ARD, asserts 

that it will be too expensive ($10,169 per ton at 0.34 lbs/MMBtu) if it cannot maintain the derate flexibility at 0.37 lbs/MMBtu...If the PSNH cost claims are correct, PSNH will not be able 

to meet its Clean Air Act obligations under the secondary standard attainment program. 

 NHDES Response: The determination of cost-effectiveness is not an absolute 

process but one that must be conducted in proper context. The context for regional 

haze is different from that for attainment/nonattainment. In the case of the former, 

any judgment of cost-effectiveness (the process does have subjective elements) 

involves consideration of total cost versus visibility improvement. For the BART 

analysis of Unit MK2, it was necessary to consider what constitutes a reasonable 

cost per ton to produce a small visibility benefit. When it comes to NOx reductions 

toward attainment of a new ozone standard, the benchmarks will be different 

because the standards for ozone are health-based.