Cost-Effectiveness Metrics

BART is not necessarily the most cost-effective solution. Instead, it represents a broad 

consideration of technical, economic, energy, and environmental (including visibility

improvement) factors. For example, Oregon DEQ established a cost/ton threshold of $7,300 

based upon the premise that improving visibility in multiple Class I areas warrants a higher 

cost/ton than where only one Class I area is affected. In their BART proposal for the San Juan 

Generating Station, New Mexico used a range from $5,946/ton to $7,398/ton, and Wisconsin is 

using $7,000 - $10,000/ton as its BART threshold.1In its proposal to disapprove part of the 

North Dakota plan, EPA R8 stated:

In our BART analysis for NOx at Milton R. Young Station 1, we considered SNCR + ASOFA and SCR + 

ASOFA...We have concluded that SNCR + ASOFA and SCR + ASOFA are both cost effective control 

technologies and that both would provide substantial visibility benefits. SNCR + ASOFA has a cost 

effectiveness value of $687 per ton. While SCR + ASOFA is more expensive than SNCR + ASOFA, it has 

a cost effectiveness value of $2,569 per ton of NOx emissions reduced. This is well within the range of 

values we have considered reasonable for BART and that states other than North Dakota have considered 

reasonable for BART. Even with more frequent catalyst replacement, SCR would still be cost effective 

even at the high end of the range ($2,783 per ton) allowing for the most frequent catalyst replacement of 

one layer per year and allowing for the questionable costs of lost power generation revenue in TESCR 

Scenario 4. We also analyzed the SCR costs assuming the same baseline emissions of 9,032 tons per year 

used by North Dakota and determined that the high-end cost effectiveness value, assuming the most 

frequent catalyst replacement frequency, would be about $3,115 per ton of NOx reduced. All of these cost 

effectiveness values are well within the range of values that North Dakota considered reasonable in several 

of its NOx BART determinations, where predicted visibility improvement was considerably lower.

We have weighed costs against the anticipated visibility impacts at Milton R. Young Station 1, as modeled 

by Minnkota and the State. Both sets of controls would have a positive impact on visibility. As compared to 

SNCR + ASOFA, SCR + ASOFA would provide an additional visibility benefit 0.553 deciviews and 18 

fewer days above 0.5 deciviews at Theodore Roosevelt. We consider these impacts to be substantial, 

especially in light of the fact that neither of these Class I areas is projected to meet the uniform rate of 

progress. We also note that the 0.553 deciview improvement at Theodore Roosevelt is greater than the 

improvement in visibility that North Dakota found reasonable to support other NOx BART determinations 

in the SIP despite higher cost effectiveness values for the sources involved in these other BART 

determinations. Given the incremental visibility improvement associated with SCR + ASOFA, the 

relatively low incremental cost effectiveness between the two control options ($4,855 per ton), and the 

reasonable average cost effectiveness values for SCR + ASOFA, we propose that the NOx BART emission 

limit for Milton R. Young Station 1 should be based on SCR + ASOFA. 2

Although EPA R8 subsequently decided not to disapprove the ND plan, its reason for changing 

its proposal for NOX controls was due to issues of technical feasibility and EPA R8 did not 

change its determination that the costs cited above are “reasonable.” Also, in its proposed 

 

1

“The Department used cost-per-ton reduced as the primary metric for determining the BART level of control. The 

upper limit for this metric was $7,000 to $10,000 per ton, which reflects historical low-end costs for controls 

required under BACT.” BEST AVAILABLE RETROFIT TECHNOLOGY AT NON-EGU FACILITIES April 19, 

2010, WISCONSIN DEPARTMENT OF NATURAL RESOURCES

2 ENVIRONMENTAL PROTECTION AGENCY 40 CFR Part 52 [EPA–R08–OAR–2010–0406; FRL–9461–7] 

Approval and Promulgation of Implementation Plans; North Dakota; Regional Haze State Implementation Plan; 

Federal Implementation Plan for Interstate Transport of Pollution Affecting Visibility and Regional Haze AGENCY: 

Environmental Protection Agency (EPA). ACTION: Proposed rule. Federal Register / Vol. 76, No. 183 / 

Wednesday, September 21, 2011 
Federal Implementation Plan for Montana, R8 determined that it was cost-effective to spend 

$4,659/ton to control SO2 and $4,415/ton for NOX at the J.E. Corette power plant.3

In evaluating addition of SCR at the Four Corners Power Plant, EPA R9 stated:

EPA considers its revised cost-effectiveness estimates of $2,515 - $3,163/ton of NOx removed to be more 

accurate and representative of the actual cost of compliance. However, even if EPA had decided to accept 

APS’s worst-case cost estimates of $4,887 – $6,170/ton of NOx removed, EPA considers that estimate to 

be cost effective for the purpose of proposing an 80% reduction in NOx, achievable by installing and 

operating SCR as BART at FCPP. 4

EPA R6 agreed with our conclusion that $2,600/ton was a reasonable cost for adding SCR at 

SJGS:

We agree with the general contention that many individual cost items for the installation of SCR on the 

units of the SJGS were overestimated by PNM...We note that the NPS estimate of an average cost of 

$2,600/ton for the four units of the SJGS closely agrees with our own revised estimate. 5

EPA has determined that costs as high as $6,170/ton are reasonable, while some states use even 

higher thresholds.

In effect, EPA R8 is basing its Colstrip NOX BART decision solely upon actions taken by PPL

subsequent to the baseline period. While it is informative to consider how much additional 

visibility improvement would result from additional emissions controls (e.g., SCR), EPA should 

not allow BART sources to circumvent the BART process by claiming credit for interim 

emission reduction measures which bias the BART process against addition of more stringent 

controls later. If EPA R8 continues to rely upon such an incremental analysis, it must re-consider 

the decision criteria it uses to evaluate those incremental changes.

EPA R8 has placed undue weight on incremental costs, which it estimated at $5,770/ton for 

SOFA + SCR on Colstrip 1 and $5,877 on Colstrip 2. In discussing average and incremental 

costs, EPA BART Guidelines explain:

The average cost (total annual cost/total annual emission reductions) for each may be deemed to be 

reasonable. However, the incremental cost of the additional emission reductions to be achieved may be 

very great. In such an instance, it may be inappropriate to choose control B, based on its high incremental 

costs, even though its average cost may be considered reasonable.

Although EPA does not explain in its BART Guidelines what it considers “very great” and 

“high” incremental costs, it goes on to provide an example of how incremental cost is calculated, 

and explains:

The incremental cost of Option 1, then, is $20,000 per ton, 11 times the average cost of $1,900 per ton.

 

3 EPA R8 determined that the visibility benefits of those controls were not sufficient.

4 ENVIRONMENTAL PROTECTION AGENCY 40 CFR Part 49 [EPA–R09–OAR–2010–0683; FRL–9213–

7] Source Specific Federal Implementation Plan for Implementing Best Available Retrofit Technology for 

Four Corners Power Plant: Navajo Nation AGENCY: Environmental Protection Agency (EPA). ACTION: 

Proposed rule. Federal Register / Vol. 75, No. 201 / Tuesday, October 19, 2010

5 ENVIRONMENTAL PROTECTION AGENCY 40 CFR Part 52 EPA–R06–OAR–2010–0846; FRL–9451–1 

Approval and Promulgation of Implementation Plans; New Mexico; Federal Implementation Plan for Interstate 

Transport of Pollution Affecting Visibility and Best Available Retrofit Technology Determination AGENCY: 

Environmental Protection Agency (EPA). ACTION: Final rule. Federal Register / Vol. 76, No. 162 / Monday, 

August 22, 2011
The clear implication of EPA’s advice in the BART Guidelines is that incremental costs become 

a deciding factor only if they greatly exceed average costs. For Colstrip Units 1 & 2, the NPS 

estimates of $5,054/ton incremental costs of SCR are only slightly greater than SCR’s $4,760/ton 

average cost (which EPA agrees is cost-effective).

Although EPA R8 provides no insight in its Federal Register notice as to what criteria it used to 

determine BART, it is our understanding that EPA R8 requires any control option with an 

incremental cost that exceeds $5,000/ton to also achieve at least 0.5 dv incremental visibility

improvement. Not only is such an approach contrary to the BART Guidelines which explicitly

state that it is not necessary for a BART option to achieve 0.5 dv improvement, it exempts any

emission unit at a BART source with less than a 0.5 dv impact from BART.