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 New Hampshire Regional Haze SIP Revision 

Responses to EPA’s Comments 

On June 26, 2009, the New Hampshire Department of Environmental Services (NHDES) 

received comments from the U.S. Environmental Protection Agency (EPA) on New 

Hampshire’s draft final Regional Haze SIP, May 22, 2009. The following are NHDES’s 

responses to EPA’s comments. Comments are written in italics and responses are written in 

regular font.

General BART Comments

1. New Hampshire indicates it used the CALGRID model for assessing the visibility 

improvement expected from the installation of Best Available Retrofit Technology (BART) 

controls for its two BART sources, Merrimack station and Newington Station. The CALGRID 

modeling results indicated that the installation of a scrubber at Merrimack would only result in 

a visibility improvement of 0.1 deciview (dv) and switching to lower sulfur fuel at Newington 

would result in negligible visibility improvement. The reader is directed to Attachment X for 

additional discussion on this analysis. However, Attachment X does not provide any 

information regarding the performance or appropriateness of the CALGRID model for this type 

of application, the Attachment only discusses the use of CALGRID for ozone modeling 

purposes. 

The MANE-VU modeling results indicate that both BART sources are among the top 167 stacks 

impacting a MANE-VU Class I area. Therefore, it does not seem to make sense that 

controlling SO2 emissions by more than 90% at Merrimack would lead to a visibility 

improvement of only 0.1 dv and that 50% control of SO2 at Newington would result in 

negligible visibility improvement. Please include an explanation of how the CALGRID and 

MANE-VU modeling relate to each other, especially in respect to pre-control visibility impacts. 

Furthermore, New Hampshire may want to consider using CALPUFF to assess visibility 

impacts of potential BART controls. As noted in the BART Guidelines (40 CFR Part 51, 

Appendix V Section (IV)(D)(5D: 

“Use CALPUFF, or other appropriate dispersion model to determine the visibility 

improvement expected at a Class I area from the potential BART control technology 

applied to the source.” 

 NHDES Response: NHDES agrees with EPA that CALPUFF (or other appropriate 

dispersion model) is the recommended model for assessing maximum potential 

impacts of single sources to distant Class I areas. Consistent with that, CALPUFF is 

EPA’s preferred model for assessing visibility impacts during PSD impact studies for 

permitting purposes. EPA has subsequently recommended application of CALPUFF 

to visibility screening of individual sources. Because CALPUFF’s strength is in 

estimating maximum possible impacts, including visibility impairment, it is a 

preferred model for determining BART eligibility. In fact, New Hampshire and the 

other MANE-VU states used CALPUFF for BART eligibility screening because the 

model is conservative, effectively predicts potential worst case visibility impacts, and 

therefore represents the ideal scenario for BART inclusion analyses. NHDES 

believes that the BART guideline’s preference for use of CALPUFF is rooted in the 

need to include all potentially significant sources of visibility degradation. 
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NHDES disagrees with EPA that CALPUFF provides the best and most useful 

predictions of the visibility benefit of BART controls. Because of how the model 

handles wind fields without regard to visibility conditions, CALPUFF’s predictions 

can be very conservative and possibly oversensitive to changes in visibility 

conditions. When the modeling results are applied to calculate the benefits of 

emission controls, those benefits can be overstated by the inflation of deciview 

improvements and the calculated cost-per-deciview ($/dv) BART control metric. 

CALPUFF’s handling of background pollutants is indirect and rather mechanical in 

nature. As a result, it does not track how its modeled impacts relate to background 

visibility, best visibility, and worst visibility days. Extra effort by the modeler is 

needed to present a realistic modeling result that aligns wind directions with 

appropriate, manually entered background conditions. 

Unlike CALPUFF and other single-source dispersion models, regional grid models 

such as CALGRID excel at accounting for the impacts of widespread sources 

contributing to total visibility impairment. To that end, for the impact assessment of 

New Hampshire’s BART-eligible sources, NHDES originally chose to use 

CALGRID, the sister model to CALPUFF. CALGRID includes much of the same 

chemistry as CALPUFF but uses gridded dispersion as opposed to the puff dispersion 

used in CALPUFF. In fact, CALGRID includes about 20 percent more enhanced 

aerosol chemistry than CALPUFF and is therefore considered to be the more 

advanced model. Moreover, CALGRID easily isolates the 20% worst visibility 

days to allow a direct, realistic result without the need for manual adjustments. It is 

important to isolate these 20% worst visibility days because it is possible (and 

perhaps probable) that a targeted BART facility will not actually contribute its 

maximum impact on those days. CALPUFF always assumes maximum emissions 

impact at Class I areas on both best and worst days – conditions that may or may not 

happen in reality. While the CALPUFF model’s CALPOST post-processor has an 

option for application on 20% best visibility days, it does not isolate those 20% best 

days for analysis. It simply changes the background values used by the model to 

what is estimated to be appropriate background conditions. The post-processed 

results do not account for wind directions that may be preferentially included or 

excluded on such days. 

The BART guidelines suggest that models be used in a “relative” way to estimate 

the expected visibility benefits of BART controls. As explained above, while 

CALPUFF is EPA’s preferred model for visibility assessments of individual 

sources, it still has its weaknesses. The model is not designed to perform complex 

calculations in which a large number of emission sources are factored-in across 

several emission sectors. Compounding the problem is the fact that, in order to 

apply the model in a relative sense, the visibility assessment has to be done with a 

non-linear metric, the deciview. The guidance uses CALPUFF to estimate the 

benefits of BART controls on a single source under the conditions of 20% worst 

visibility days when, in fact, a multitude of sources actually contribute to visibility 

impact. The model can easily calculate the concentration benefits from the chosen 

source controls, but the conversion of the data into deciview units involves a nonlinear estimation. A CALPUFF post-processor allows a simple selection of 

background visibility conditions and then performs deciview benefit calculations in 

a crude way. 
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Because both EPA and the FLMs filed comments expressing their preference for 

CALPUFF modeling results, NHDES performed a limited set of CALPUFF runs for 

the New Hampshire BART-eligible sources under controlled and uncontrolled 

conditions. Rather than use CALPOST’s post-processing option for the 20% best 

and worst days, NHDES applied the CALPUFF modeling results in a relative way, 

in recognition of EPA’s guidance for BART modeling. NHDES normalized the 

CALPUFF modeling results and then applied the predicted concentrations to a 

logarithmic best-fit equation of the actual observed PM2.5-to-deciview relationship 

measured at Acadia NP, Great Gulf NW, and Lye Brook NW. Thus, CALPUFF 

was applied in a relative way using real observed data as the basis. At this point, a 

number of background visibility scenarios could be calculated from the resulting 

PM-mass-to-deciview equation. In accordance with BART guidance, the natural 

visibility condition (about 7 dv) was used for exemption purposes; and 20% worst 

visibility (22.8 dv) was used for assessment of BART control effectiveness. 

Merrimack Station Unit MK2: BART Eligibility Modeling

The BART eligibility modeling conducted by MANE-VU used natural visibility 

conditions (about 7 dv) to produce the most conservative modeling results to 

minimize sources from modeling out of BART. Under these conditions, uncontrolled 

emissions from Unit MK2 produce theoretical CALPUFF worst-case impacts of 

2.29 dv at Acadia National Park. EPA considers acceptable source exemptions 

when this form of conservative modeling indicates a source produces less than 0.5 

dv of impact. MANE-VU considers an exemption level of 0.2 to 0.3 dv to be more 

appropriate but prefers, and has applied, a more conservative exemption level of 0.1 

dv. CALPUFF modeling results for baseline emissions from Unit MK2 exceed all 

of these exemption levels. 

Merrimack Station Unit MK2: BART Benefit Assessment Modeling

The BART assessment modeling provides a comparison of visibility impacts from 

current allowable emissions with those from the post-control emission level (or 

levels) being evaluated. In accordance with EPA guidance, NHDES used CALPUFF 

to estimate the magnitude of the source’s impacts on visibility after implementation 

of BART controls. Results are tabulated for the average of the 20% worst visibility 

(in this case, about 22.8 dv) modeled days at each nearby Class I area. For any pair 

of control levels evaluated, the difference in the level of impairment predicted is the 

degree of improvement in visibility expected. 

For Merrimack Station Unit MK2, the CALPUFF-predicted visibility benefits from 

BART controls on 20% worst visibility days are as follows: 
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CALPUFF Modeling Results for Merrimack Station Unit MK2: 

Visibility Improvements from BART Controls on the 20% Worst Visibility Days 

Pollutant Control Level Acadia NP Great Gulf NW Lye Brook 

SO2 90% with FGD 0.17 dv 0.15 dv 0.08 dv 

NOx Additional 25% 

with SCR upgrade 0.02 dv 0.01 dv < 0.01 dv 

PM 99% with upgraded 

controls < 0.01 dv* < 0.01 dv* < 0.01 dv* 

 * below sensitivity limit of model 

While Unit MK2 was predicted to have up to 2.29 dv impact at Acadia National 

Park under natural conditions, the basis of the BART assessment evaluation changes 

to 20% worst visibility days. On those days, a 90% reduction in sulfur emissions at 

Unit MK2 results in only a 0.17 dv visibility improvement. At first these results 

may appear to be incorrect; however, on further examination, it is found that 

CALPUFF predicts the same amount of sulfate from Unit MK2 reaching Acadia 

under both best and worst visibility conditions. The difference is that there is greater 

than an order of magnitude more sulfate coming from other sources on the 20% 

worst visibility days, raising the background concentrations to much higher levels. 

Because the deciview scale is logarithmic, the same mass reduction of 0.26 μg/m3

 of 

sulfate from this one source results wide differences in deciview impacts for 

different background visibility conditions at opposite ends of the range. 

The above analysis indicates that CALPUFF and CALGRID have aligned better in 

their predictions than might be expected. This result may be attributed to the similar 

chemistry used in both models and to the specific circumstances of this case in 

which the prevailing wind direction on the 20% worst visibility days carries Unit 

MK2 emissions directly toward Acadia National Park. The big discrepancy occurs 

under best visibility days, when CALGRID (correctly) does not align the source to 

receptor, but CALPUFF (incorrectly) applies wind directions for worst visibility 

days to the best day calculations. 

Newington Station Unit NT1: BART Eligibility Modeling

The BART eligibility modeling conducted by MANE-VU used natural visibility 

conditions (about 7 dv) to produce the most conservative modeling results to 

minimize sources from modeling out of BART. Under these conditions, uncontrolled 

emissions from Unit NT1 produce theoretical CALPUFF worst-case impacts of 1.22 

dv at Acadia National Park. As in the case of Unit MK2, CALPUFF modeling 

results for baseline emissions from Unit NT1 exceed all of these exemption levels. 

Newington Station Unit NT1: BART Benefit Assessment Modeling

For Newington Station Unit NT1, the CALPUFF-predicted visibility benefits from 

BART controls on 20% worst visibility days are smaller than those for Merrimack 

Station Unit MK2: 
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CALPUFF Modeling Results for Newington Station Unit NT1: 

Visibility Improvements from BART Controls on the 20% Worst Visibility Days 

Pollutant Control Level Acadia NP Great Gulf NW Lye Brook 

1.0%-S Residual Fuel Oil 

(50% sulfur reduction*) 0.05 dv 0.04 dv 0.02 dv 

0.5%-S Residual Fuel Oil 

(75% sulfur reduction*) 0.07 dv 0.06 dv 0.03 dv 

SO2 

0.3%-S Residual Fuel Oil 

(85% sulfur reduction*) 0.08 dv 0.07 dv 0.04 dv 

NOx 50% with SCR 0.01 dv < 0.01 dv** < 0.01 dv** 

PM 99% with upgraded 

controls *** *** *** 

 * from maximum permitted level 

 ** below sensitivity limit of model 

*** Modeling for PM was not performed because existing controls may already be achieving greater than 90% 

reduction, and any visibility benefit would be below the model’s sensitivity limit. 

Notes on CALGRID Model Performance

As noted in EPA comments, CALGRID has been accepted in the past by EPA for 

photochemical modeling of ozone for SIP purposes. Over the past several years, 

most regional models have evolved in use and performance since their original 

photochemical use and now effectively model PM2.5 and visibility impacts. CMAQ 

and CAMx are two other regional grid models that are more commonly used than 

CALGRID; however, CALGRID has found a niche in the Northeast and in other 

parts of the world for use as a screening model. 

Formal performance testing for CALGRID’s ozone predictions was done prior to its 

use for PM2.5 and regional haze modeling. Rigorous statistical performance testing 

for PM2.5 was not done since CALGRID is only being used in a screening mode and 

simple comparative testing demonstrated that CALGRID performs reasonably in 

comparison to the REMSAD model. NHDES recognizes that EPA requires 

performance evaluations on a modeling platform before it can be applied to 

predicting SIP attainment of a NAAQS. Instead, CALGRID has been applied in 

SIP supportive and informational work. 

CALGRID testing for PM2.5 species was performed on a period of approximately

two weeks that included high PM and poor visibility days as well as relatively clean 

days. Most focus of the testing was on the OTR; however, performance in upwind 

areas was also noted because it’s an important source of emissions that transport 

into the OTR. As is typical for photochemical model performance, the models often 

did better on higher pollution days than on cleaner days, but overall performance we 

determined to be good and adequate for use. 

While no formal documentation of this testing was completed, plots and graphs that 

were created for the work have been added to Attachment X. NHDES concludes 

that CALGRID model performance for PM2.5 and regional haze is good and is thus a 

reasonable modeling tool to use for screening modeling. The Delaware Department 
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of Natural Resources and Environmental Control similarly reviewed the model’s 

performance and has accepted it for PM2.5 and haze modeling. 

It should also be noted that CALGRID predicts sulfates, nitrates, PM, and several 

organic species and reconstructs visibility according to the IMPROVE deciview 

equation. The CALPUFF processors do not predict organics and use a less refined 

process to predict visibility changes.

2. Implementation of the selected BART control strategies for each of the three pollutants 

(SO2, NOx, and PM2.5) at both BART facilities must be federally enforceable. The Regional 

Haze SIP must clearly indicate how this is being accomplished in each case. Specifically, the 

relevant rules or permits should be included as part of New Hampshire’s Regional Haze SIP 

revision or the SIP revision should cite specific rules or permits conditions that are already 

federally enforceable. 

 NHDES Response: The BART controls and enforceable provisions for Unit MK2 

and Unit NT1 are summarized in the tables below:

PSNH Merrimack Station Unit MK2 

Pollutant BART Controls / Emission Limitations Citations

NOX SCR (existing); 

NOx emission limit of 0.37 lb/MMBtu, calendar 

monthly average (proposed) 

Draft Title V Operating Permit (TV-0055); 

Administrative Rule Env-A 2300 

Mitigation of Regional Haze (proposed) 

PM Two ESPs in series (existing); 

TSP emission limit of 0.08 lb/MMBtu (proposed)

Draft Title V Operating Permit (TV-0055); 

Administrative Rule Env-A 2300 

Mitigation of Regional Haze (proposed) 

SO2 Fuel sulfur limits (existing); 

Flue gas desulfurization (FGD), with required 

SO2 percent reduction set at maximum 

sustainable rate, but not less than 90% as a 

calendar monthly average (in progress) 

Administrative Rule Env-A 1606.01 

Maximum Sulfur Content Allowable in Coal 

(existing); 

Temporary Permit for FGD system (TP-0008); 

Draft Title V Operating Permit (TV-0055) 

PSNH Newington Station Unit NT1 

Pollutant BART Controls / Emission Limitations Citations

NOX Overfire air and water injection (existing); 

NOx emission limits of 0.35 lb/MMBtu with oil 

and 0.25 lb/MMBtu with oil/gas, 24-hour 

calendar day average (existing) 

Title V Operating Permit (TV-OP-054) 

PM Electrostatic precipitator (existing); 

TSP emission limit of 0.22 lb/MMBtu (existing) 

Title V Operating Permit (TV-OP-054) 

SO2 SO2 emission limit of 0.50 lb/MMBtu, calendar 

monthly average, applicable to any fuel type or 

mix (proposed) 

Administrative Rule Env-A 2300 

Mitigation of Regional Haze (proposed); 

Title V Operating Permit (TV-OP-054) 
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BART Determination for PSNH Newington Station Unit NT1

3. For SO2 New Hampshire determined that the BART level of SO2 control for PSNH 

Newington Station unit NTI is to switch from 2% sulfur content by weight residual oil to 1% 

sulfur content by weight residual oil. 

PSNH Newington Station unit NT1 is a tangentially-fired steam generating unit. The Title V 

permit indicates that NTI can burn crude oil or No. 6 fuel oil at no more than 2% sulfur content 

by weight, No. 2 fuel oil at no more than 0.4% sulfur content by weight, or natural gas. Based 

on recent data submitted to EPA’s Clean Air Market Division, it appears that changing the 

enforceable sulfur-in-fuel limit from 2% sulfur No. 6 oil to 1% sulfur No. 6 oil will provide 

minimal reductions in SO2 emissions since average SO2 emission rates are near the levels 

emitted while burning 1% sulfur No. 6 oil. (See Table 1 below which contains 2007 data for 

PSNH Newington Station.) Thus, other fuel switching options should also be explored. These 

options include: (1) the use of natural gas, (2) the use of 0.3% sulfur No. 6 oil as recommended 

by the MANE-VU BART workgroup or (3) the use of No. 2 fuel oil at no more than 0.3% sulfur 

content by weight. 

NHDES Response: EPA has suggested greater use of natural gas and/or low-sulfur 

distillate fuel oil in place of residual fuel oil. The substitution of No. 2 distillate fuel 

oil for No. 6 residual fuel oil would not be not be practical for this facility because 

of the high capital costs involved. Burner replacements to allow the boilers to 

combust distillate fuel oil could exceed $20 to $30 million in direct capital costs, not 

including the additional costs of engineering and any required auxiliary equipment. 

Please refer to the next response in reference to the use of natural gas versus 

residual fuel oil. 

Reducing the permitted fuel sulfur limit to 1.0 % or 0.5 % would yield significant 

reductions in SO2 emissions at Newington Station. Note that from 2002 to 2007, the 

average annual sulfur content of #6 fuel oil burned at Unit NT1 ranged between 0.93 

and 1.53 percent by weight, with no discernable trend. For New Hampshire’s BART 

analysis, the following fuel sulfur values were assumed: 

Nominal %S 

(Permit Limitation) 

Assumed Actual %S 

(Chemical Assay) 

2.0 1.2 

1.0 0.8 

0.5 0.4 

 

Under these assumptions, switching from 2.0 %S (nominal) to 1.0 %S (nominal) 

residual fuel oil would produce a one-third reduction in sulfur emissions, and 

switching to 0.5 %S (nominal) residual fuel oil would produce a two-thirds reduction 

in sulfur emissions at this facility. The use of 0.3 %S residual fuel oil was briefly 

considered but not evaluated in detail because this fuel is in very limited use within 

the region, and its future availability and price are uncertain for northern New England. 

Its potential use will continue to be evaluated as the market for it in the region develops 

and supplies and prices can be better projected and assured. 

Currently, the only consideration of natural gas as a primary fuel source shown in the proposal 

is the statement, “In recent years, there have been sudden and dramatic swings in the price of 

natural gas relative to fuel oil as supply/demand have shifted. The future price and availability 

of natural gas are difficult to discern.” 
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Recent data from the Energy Information Administration, however, indicates the Average Cost 

of Natural Gas and Residual Oil are projected to remain comparable. (See Figure 1, “Historic 

and Projected Power generation Fuel Costs — National.”) Therefore, EPA recommends that 

greater consideration be given to the use of natural gas as the primary fuel at Newington 

station, with No. 2 fuel oil and/or No. 6 fuel oil being used as the secondary fuel, with a 

constraint on the number of gallons burned per year. 

 NHDES Response: Unit NT1 can be fired with either natural gas or liquid fuel (i.e., 

residual fuel oil or biofuel), or it can be co-fired with both types of fuel at the same 

time. However, because of physical limitations to the boiler design, the unit cannot 

operate at full capacity when fueled solely by natural gas. In order to reach 

maximum heat input, the boiler must either burn liquid fuel or be co-fired with both 

fuel types. (Unit NT1 can operate at up to approximately 50 percent of maximum 

heat input from natural gas, with no corresponding limitation on liquid fuel.) There 

is already a natural incentive for PSNH to operate Unit NT1 with natural gas 

(provided a reliable supply exists) whenever the price of natural gas is competitive 

with or less than the price of residual fuel oil.

In recognition of the dual-fuel capability of this unit, NHDES has prepared a draft 

rule that will reduce sulfur dioxide emissions by imposing an SO2 emission limit of 

0.50 lb/MMBtu for this facility regardless of fuel type. The rule would allow the 

facility the flexibility to burn natural gas and/or fuel oil in any feasible ratio, 

depending on market conditions. Past records indicate that to achieve the 0.50 

lb/MMBtu limitation when burning only residual fuel oil, an average fuel sulfur 

content of approximately 0.45 percent or less would be required. A 50:50 ratio of 

natural gas to fuel oil would require a fuel oil sulfur content of 0.9 percent or less.

If, however, it is not possible to utilize natural gas as the primary fuel type for this unit, then 

New Hampshire should explain why 1% sulfur No. 6 oil was determined to be BART, rather 

than the MANE-VU BART workgroup recommended sulfur fuel oil limit of 0.3% sulfur content 

by weight. This limit is currently required of facilities in Connecticut pursuant to Connecticut’s 

Section 22a-l74-19a regulation. 

Additionally, New Hampshire should explain why 0.5% sulfur fuel oil is not BART as well. The 

proposal indicates that the cost effectiveness of using 1% versus 0.5% fuel oil is the same at 

$1900/ton. This argues fur the implementation of 0.5% sulfur fuel oil. Also, other facilities in 

New England are currently limited to 0.5% for No. 6 fuel oil. (See the Title V permit for Salem 

Harbor Unit #4.) 

 NHDES Response: There is greater assurance today of the availability 0.5%-sulfur 

residual fuel oil than when the original BART determination was drafted. Maine, 

Massachusetts, New Jersey, and possibly other states within MANE-VU have already 

made commitments to require the use of 0.5%-sulfur residual fuel oil, thus ensuring 

the presence of a regional market for this commodity. The use of 0.3%-sulfur 

residual fuel oil in Connecticut does not guarantee the availability of this fuel in 

northern New England, which obtains its bulk oil shipments through different ports.

New Hampshire’s draft rule creating a sulfur dioxide emission limit of 0.50 

lb/MMBtu for Unit NT1 will cause a substantial reduction in emissions of this 

pollutant without concern for relative fuel supplies and prices, which are largely 

unknown. For the first regional haze progress report, to be submitted circa 2013, 
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NHDES will review fuel usage, fuel supplies, fuel prices, and plant utilization/ 

capacity factors to determine whether the proposed fuel sulfur limitation is still 

appropriate as BART control for Unit NT1. Should the review indicate a different 

BART control level, the facility’s Title V operating permit will be amended as 

necessary before its expiration date of March 31, 2012, fifteen months prior to the 

effective date of proposed BART control measures.

In table 1 below is a listing of all of the electric generating steam units in New England that 

were operational in 2007 and which use residual oil as their primary fuel. As illustrated in the 

table, most of the units have current SO2 emissions rates well below the emission rate proposed 

as BART for PSNIH Newington Station. 

 NHDES Response: The newly proposed sulfur dioxide emission limit of 0.50 

lb/MMBtu would fall below many of the SO2 emission rates listed in the table. 

4. For NOx, New Hampshire has determined that BART is met for Newington Unit I through 

use of the current suite of NOx controls; low NOx burners, an overfire air system, and water 

injection. New Hampshire indicates that the current emission limits are a daily average of 0.35 

lb/MMBtu when burning oil and 0.25 lb/MMBtu when burning a combination of oil and gas. 

The MANE-VU BART workgroup, however, recommended a level of NOx control for non-CAIR 

EGUs of 0.1 - 0.25 lb/MMBtu, depending on boiler and fuel type. Therefore, New Hampshire 

should analyze if a more stringent emission limit is appropriate for this unit. 

 NHDES Response: The MANE-VU BART Workgroup draft presumptive control 

levels are found in Appendix C of NESCAUM’s “Five-Factor Analysis of BART 

Eligible Sources: Survey of Options for Conducting BART Determinations,” June 1, 

2007 (special emphasis on draft). The presumptive limits are generally applicable

to BART facilities having greater than 750 MW capacity and may not be 

representative of smaller EGUs like Unit NT1. Also, the workgroup’s draft 

recommendations for non-CAIR EGUs do not take into account the effects of scale 

when a facility operates at very low utilization rates and capacity factors. 

In the case of Unit NT1, since 2006 the average annual capacity factor has been 

below 10 percent; and preliminary data for January through September of 2009 

indicate that the plant was effectively offline for all but the first month of the year. 

Consequently, the capital costs associated with SCR or SNCR to achieve a control 

level of 0.1 - 0.25 lb/MMBtu cannot be justified for this EGU at this time, especially 

on a visibility benefit basis. NHDES finds that the existing NOx RACT limits 

reasonably represent the sustainable performance capabilities of this unit and are 

sufficient as BART control levels for NOx on a 30-day averaging basis. 

In New England, there is a least one oil-fired electric generating steam unit with selective 

catalytic reduction installed (Unit #1 at Canal Electric in Sandwich, MA) and at least three oilfired electric generating steam units with selective non-catalytic reduction installed (Units #1 

and #2 at Norwalk Harbor Station in Norwalk, CT and Unit #3 at Middletown Station in 

Middletown, CT). 

 NHDES Response: While SCR or SNCR may be appropriate for certain oil-fired 

EGUs elsewhere in New England, the particular circumstances of Newington Station 

do not support the implementation of either technology as BART for Unit NT1. It is 

difficult to justify any significant capital expenditure in the context of the plant’s 

recent operating history and the limited visibility benefit that might be obtained.
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5. For PM the proposal indicates that the currently installed electro-static precipitator (ESP) 

is sufficient for BART, yet only cites a 42% control efficiency. According to the BART analysis, 

a rebuilt ESP can achieve collection efficiencies of more than 99%. Therefore, the BART 

determination should include an analysis of the feasibility of an upgraded or rebuilt ESP for 

this unit. Furthermore, the MANE-VU BART workgroup recommendation for non-CAIR EGUs 

is a PM emission rate of 0.02 - 0.04 lb/MMBtu. New Hampshire should provide greater detail 

as to why the state considers its current limit of 0.22 lb/MMBtu as sufficient for BART. 

 NHDES Response: The 42 percent efficiency value was obtained by comparing the 

PM emission factor from a 2001 controlled stack test report with an AP-42 emission 

factor for uncontrolled PM, and is therefore a crude approximation of particulate 

removal efficiency. NHDES has located a 1971 performance specification for this 

unit from Buell Envirotech Corp. The efficiency is stated as 93 percent under 

normal operating conditions and a maximum of 98 percent under design conditions. 

It is unknown whether these higher control rates are representative of the unit’s 

actual long-term performance. The emission rate calculated from the 2001 stack 

testing (the only data available) was 0.058 lb/MMBtu. This emission rate is within 

the expected range for a properly operating ESP at a plant like Newington and may 

be a better measure of performance than the stated efficiencies. 

The single stack test result is insufficient to support consideration of a BART 

performance level more restrictive than the current permit limit. The facility’s Title 

V operating permit requires that a compliance stack test for PM emissions be 

performed on Unit NT1 before the permit expires on March 31, 2012. NHDES will 

review the stack test results, and may request additional information from the 

facility’s owner, to ascertain the unit’s performance. NHDES will then incorporate 

any new limit, as appropriate, into a permit amendment by the permit expiration 

date. The permit expiration date precedes the effective date of proposed BART 

control measures by fifteen months.

BART Determination for PSNH Merrimack Station Unit MK2

6. For SO2, New Hampshire has determined that BART is the installation of flue gas 

desulfurization (FGD) controls and has issued a temporary permit to the facility which is 

included in Attachment EE of the submittal. EPA previously reviewed a draft of this permit and 

submitted comments to the DES in a letter dated March 3, 2009. We have reviewed the version 

of the permit included in the proposal and note that all of our previous comments have been 

adequately addressed. 

7. For NOx, New Hampshire has determined the year round use of selective catalytic 

reduction (SCR) is considered BART for Unit MK2. This determination seems reasonable. 

New Hampshire, however, states that its current federally enforceable limit for this unit is 0.86 

lb/MMBtu, while the MANE-VU recommended level of BART control for non-CAIR EGUs is 

0.1 - 0.25 lb/MMBtu, depending on the boiler and fuel type. A review of the data in the CAMD 

database indicates that MK2 is achieving an emission rate well below 0.86 lb/MMBtu. For 

example, the highest monthly average emission rate in 2008 was 0.30 lb/ MMBtu. Therefore, 

New Hampshire should impose a more stringent emission limit for this unit. 

 NHDES Response: Unit MK2 is required to meet a federal acid rain limit of 0.86 lb 
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NOx/MMBtu, an additional NOx RACT Order limit of 15.4 tons per calendar day, 

and a NOx RACT Order limit of 29.1 tons per calendar day for Units MK1 and 

MK2 combined. The 15.4 ton/day limit is more stringent than the acid rain limit: 

based on a gross heat input rating of 3,473 MMBtu/hr, the daily limit is equivalent to 

an emission rate of 0.37 lb/MMBtu (= 15.4 ton/day × 2,000 lb/ton ÷ 24hr/day ÷ 3,473 

MMBtu/hr). 

Since January 2001, the SCR on Unit MK2 has reduced NOx emissions to between 

0.15 and 0.37 lb/MMBtu (calendar monthly average), with a few excursions outside 

this range. Data available from the period of 1993 to early 1995, prior to operation 

of the SCR, provide a baseline for uncontrolled NOx emissions in the range of 2.0 

to 2.5 lb/MMBtu. Taken together, this information indicates that Unit MK2 

achieves a control level greater than 85 percent most of the time. 

The presumptive BART control level of 0.1 to 0.25 lb/MMBtu is applicable to 

power plants having greater than 750 MW capacity and may not be representative of 

smaller EGUs like Unit MK2. Because this unit’s cyclone boiler has a relatively 

high uncontrolled NOx emission rate, it follows that the controlled emission rate, 

even as control efficiencies approach 90 percent, would frequently exceed the 

presumptive norm attributed to larger EGUs. 

NHDES finds that the effective NOx RACT limit of 0.37 lb/MMBtu reasonably 

represents the sustainable performance capabilities of this unit and is also satisfactory 

as a BART emission limit for NOx on a calendar monthly averaging basis. Note, 

however, that PSNH may continue to have a monetary incentive to surpass the NOx 

RACT requirement because lower emissions allow the utility to accrue Discrete 

Emission Reductions (DERs) under New Hampshire rules. 

8. For PM New Hampshire has determined that the use of two currently installed ESPs is 

considered BART for Unit MK2. This seems reasonable. The proposal, however, indicates that 

the current air permit imposes a 0.227 lb/MMBtu limit, while the MANE-VU recommended 

level of BART control for non-CAIR EGUs is 0.02-0.04 lb/MMBtu. Therefore, New Hampshire 

should analyze if a more stringent emission limit is appropriate for this unit. 

 NHDES Response: The 0.227 lb/MMBtu limit derives from the formula established 

in Env-A 2002.06 and does not reflect the true capabilities of the ESPs serving Unit 

MK2 to control particulate emissions. Stack testing on three separate dates in 1999 

and 2000 (the most recent PM stack tests on this unit) found actual TSP emissions 

to be 0.043, 0,041, and 0.021 lb/MMBtu. 

The volume of field data is insufficient to establish a conclusive, long-term BART 

performance level of 0.04 lb/MMBtu or lower for this unit. Accordingly, NHDES 

has developed a draft rule that will hold TSP emissions to no greater than 0.08 

lb/MMBtu, but on a broader scope than required under BART: this standard will 

apply to Unit MK1 (not a BART-eligible facility) as well as Unit MK2. In the 

current draft Title V operating permit, Unit MK1 has a TSP emission limit of 0.27 

lb/MMBtu, or more than three times the proposed limit of 0.08 lb/MMBtu. 

Including Unit MK2 in the rule has the effect of reducing the allowable combined 

TSP emissions from the two coal-fired units at Merrimack Station to less than the 

total emissions that would be allowed if the limit for Unit MK2 were set at 0.04 

lb/MMBtu and the limit for Unit MK1 remained as is (377 lb/hr vs. 473 lb/hr). 
Page 12 of 13 

Other Comments

9. We recommend the 5th paragraph on page 6 be revised as follows: 

“About half of the worst visibility days in the New Hampshire Class I Areas occur in the 

summer when meteorological conditions are more conducive to the formation of sulfate 

from SO2 and to the oxidations of organic aerosols. In addition, winter and summer 

transport patterns are different, possibly leading to different contributions from upwind 

source regions. As a result, The remaining worst visibility days are divided nearly equally 

among spring, winter and fall. In addition, winter and summer transport patterns are 

different, possibly leading to different contributions from upwind source regions.” 

 NHDES Response: The recommended text revision has been made.

10. In Section 6.1.2, the Beyond-on-the way (BOTW) emissions scenario is described as 

“accounting for controls from potential regulations that may be necessary to meet attainment 

and other air quality goals, mainly for ozone.” Based on the list of measures provided on page 

123, it is unclear how New Hampshire expects to reduce area source emissions by 4,303 tons 

per year, as depicted in Table 6.3 2018 BOTW Emissions Inventory Summary for New 

Hampshire. 

 NHDES Response: The 4,303 ton/year reduction in SO2 emissions is attributable to 

the proposed BOTW control measure that reduces the sulfur content of residential 

and commercial distillate (heating) oil. The following description is taken from Part 

5.2.6 of MANE-VU’s Final Technical Support Document “Development of 

Emission Projections for 2009, 2012, and 2018 for NonEGU Point, Area, and 

Nonroad Sources in the MANE-VU Region” (Attachment N): 

“The BOTW control measure for heating oil is based on NESCAUM’s report entitled ‘Low 

Sulfur Heating Oil in the Northeast States: An Overview of Benefits, Costs and 

Implementation Issues.’ NESCAUM estimates that reducing the sulfur content of heating 

oil from 2,000 ppm to 500 ppm lowers SO2 emissions by 75 percent, PM emissions by 80 

percent, NOx emissions by 10 percent. The 500 ppm sulfur heating oil is not expected to 

[be] available on a widespread basis until 2012 at the earliest. These percent reductions 

were applied to residential distillate oil category (SCC 21-04-004-xxx) and commercial 

distillate oil category (SCC 21-03-004-xxx).” 

These SO2 control measures would precede additional required reductions in 

fuel sulfur content as delineated in MANE-VU’s low-sulfur fuel strategy. Such 

additional measures were included in the 2018 most recent emissions inventory 

(“best and final” scenario) as represented by the data in Table 6.4. 

11. The MANE-VU “Ask” includes a low sulfur fuel oil strategy. With regard to this strategy, 

on page 141 of New Hampshire’s proposal, the state indicates that it plans to revise its Env-A 

1604 regulation and a draft of the revised rule is provided in Attachment FF. These revised 

provisions will need to be adopted and submitted to EPA as a SIP revision so they may become 

a federally enforceable part of New Hampshire’s Regional Haze SIP. The proposal currently 

indicates that New Hampshire commits to revising this rule “at the earliest practicable date.” 

New Hampshire should include a schedule for adoption of the revised regulation. 

 NHDES Response: The revised Env-A 1604 fuel sulfur standards will be submitted 

to EPA as a SIP revision before July 1, 2013, when New Hampshire expects to 

begin implementing the MANE-VU low-sulfur fuel oil strategy. Well in advance of 
Page 13 of 13 

that date, NHDES will review with MANE-VU the appropriateness of the proposed 

fuel sulfur limits. The draft rule (amended, if necessary) will be distributed to 

stakeholders for comment prior to promulgation of the final rule. New Hampshire’s 

tentative schedule for rulemaking and adoption of the revised Env-A 1604 is as 

follows: 

Circulate rough draft of rule............................... January 2012 

Confer with affected stakeholders......................... February - June 2012 

Issue draft rule; initiate formal public process............ September 2012 

Adopt final rule.............................................. May 2013 

Rule becomes effective..................................... July 1, 2013 

In addition, the discussion of the low sulfur fuel oil strategy in Section 10.2.3 (page 98) of the 

proposal notes a concern for potential supply disruptions for residual fuels in northern states. 

This discussion also states, “MANE-VU has identified several mechanisms that could be 

implemented to address disruptions, including seasonal averaging and emergency waivers. A 

seasonal averaging approach would reduce potential supply constraints by allowing the use of 

higher-sulfur during periods of peak demand.” The proposal, however, does not further 

elaborate on whether or not New Hampshire plans to allow seasonal averaging and emergency 

waivers. If such provisions are allowed, then there should also be a mechanism to ensure that 

the use of higher-sulfur oil during peak demand times does not correspond with meteorological 

conditions leading to the 20% worst visibility days. 

NHDES Response: New Hampshire would follow procedures established by EPA in 

the event of a fuel supply emergency. As described at EPA’s fuel waivers website at 

http://www.epa.gov/compliance/resources/faqs/civil/fuelwaiver.html, the agency, with 

the concurrence of the Department of Energy, may temporarily waive a fuel or fuel 

additive requirement if doing so will alleviate the fuel supply emergency. Clean Air 

Act Section 211(c)(4)(C), which authorizes fuels waivers, specifies the criteria for 

granting a fuel waiver and the conditions that must be included in a fuel waiver. In the 

case of an emergency disruption of low-sulfur fuel supplies, NHDES would seek a 

short-term emergency waiver on fuel sulfur content. To the extent feasible, it would be 

the intent of any such waiver to moderate the degree of visibility degradation resulting 

from temporary use of higher-sulfur fuels in a supply disruption. The details would be 

worked out in response to the particulars of the emergency situation at the time of any 

waiver request.