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### 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 let ter. Comments are written in italics and responses are written in regular font.

Comment: You have determined that the July 17, 1998, NOx RAC T Order for Merrimack Station MK2 satisfies the Regional Haze BART requir ement. The 1998 NOx RACT Order requires that MK2 emit no more than 15.4 tons of NO x per each 24 hour calendar day. In the BART analysis, 15.4 tons per day equates to 0.37 lb s/MMBtu of NOx. NHSC rejects your determination that the MK2 RACT Order satisfies BAR T. [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 o f the performance capabilities of Unit MK2, for reasons e xplained in the BART analyses of the Regional Haze SIP, Attachment X. However, a fter 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, whic h is incorporated into the nowadopted rule as a maximum allowable emission rate t o 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 Hampsh ire nonattainment program, particularly for NOx, a major component of both regional haze an d ozone. ARD is required by the Clean Air Act to timely establish a NOx emission limit fo r Merrimack Station MK2 that satisfies both the Regional Haze BART requirement and the nonattai nment 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 whate ver to fix a 0.37 lbs/MMBtu BART emission limit for NOx knowing that a more stringen t 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 Ambien t Air Quality Standards for ozone. It would be premature to issue a strengthen ed NOx RACT order for Unit MK2 before EPA has promulgated the revised standard s 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 requir ements for NOx in conjunction with the regional haze program or BART.Page 2 of 2

Comment: PSNH has increased the historic net generating capa city of MK2 from 320 MW to an ISO NE capacity claim of 338 MW. PSNH is curren tly operating MK2 at 332 MW...NHSC rejects the PSNH claim that the generation upgrade is enti rely due to increased efficiency of the replaced MK2 turbine 2. ARD has failed to exam ine 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 pe rmitting requirements, including New Hampshire’s New Source Review program. NHDES’s decision on this permitting action was documented in a letter to Pub lic 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 program s 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 "f lexibility" to operate the SCR at a much higher emission limitation. [Footnote 3: Data contained i n ARD files indicate that MK2 NOx removal is, on average, below the .37 lbs/MMBtu NOx RACT li mit.]

Existing ARD data does not support the PSNH claim t hat 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 critic al 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 ope ration.

 NHDES Response: In new data provided by PSNH (see Regional Haze S IP, Attachment X supporting documentation), the company applies an emission rate of 0.8 lb/MMBtu during low-load operations for the cal culation of NOx emissions, 30- day rolling average. This value, which NHDES consi ders 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 ordere d 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 sec ondary standard attainment program.

 NHDES Response: The determination of cost-effectiveness is not an absolute process but one that must be conducted in proper co ntext. The context for regional

haze is different from that for attainment/nonattai nment. In the case of the former, any judgment of cost-effectiveness (the process does have subjective elements)

involves consideration of total cost versus visibil ity 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 benc hmarks will be different

because the standards for ozone are health-based.