Summary of Interagency Working Comments on Draft Language under 

EOs12866 and 13563 Interagency Review. Subject to Further Policy Review.

1

Comments on the Feasibility TSD, Employment Estimates of Direct Labor in Response to the 

Proposed Toxics Rule in 2015 document, and Preamble for the MATS Rule

1. MATS Feasibility TSD, Page 6 and Table 2: In this feasibility document1, it is stated: “EPA has 

adopted a single metric to represent all APC technologies in this analysis. Use of a single metric 

facilitates an extrapolation of historic deployment rate data for wet and dry FGD and SCR to 

assess feasible future deployment rates needed for the retrofit technologies projected for 

MATS. Such a single metric permits assessment of the overall combined feasibility of all APC 

retrofits projected. This metric should be regarded as “average,” not capturing the specifics of 

any particular site, but representing average difficulty across many projects.”

For the single metric mentioned above, EPA assumes that the industrial resources required for 

furnishing and installing each environmental control technology option for compliance with 

MATS can be projected as a percentage of the resources required for a wet FGD system, with 

this percentage being defined as a ratio of the capital costs for the control technology option 

and wet FGD scrubber. EPA has not provided any technical justification to prove that a cost 

ratio can be used for the determination of industrial resource requirement in this manner. We 

suggest that EPA add a reference in support of this assumption.

In support of the above concern, we also note that EPA has prepared and issued another 

technical support document2for MATS, which shows different resource requirements for the 

same technologies included in the first document. For example, comparing the information in 

Tables A-1 and A-2 of the second document to the information in Table 2 of the first document, 

the following discrepancies are obvious:

 In the first document, the resource requirements for fabric filter (FF) are shown at 30% 

of that for wet FGD. However, in Tables A-1 and A-2 of the second document, the labor 

and steel requirements for FF are listed at 52 and 63% of that for wet FGD, respectively.

 For SCR (see the comment below), the resource requirements are shown at 40% of that 

for wet FGD in the first document, whereas the second document lists the labor and 

steel requirements for SCR at 92% and 111% of that for wet FGD.

 The second document also shows that boilermaker hours required for FF and SCR are 

higher percentages of the total manhours, as compared to the boilermaker hours for 

wet FGD.

 

1

“An Assessment of the Feasibility of Retrofits for the Mercury and Air Toxics Standards Rule,” U.S. Environmental 

Protection Agency, Office of Air and Radiation, Final Draft, November 2011

2

“Employment Estimates of Direct Labor in Response to the Proposed Toxics Rule in 2015,”EPA Docket Number: 

EPA-HQ-OAR-2009-0234
Summary of Interagency Working Comments on Draft Language under 

EOs12866 and 13563 Interagency Review. Subject to Further Policy Review.

2

 The information provided in the second document is backed by references, one of which 

is a detailed study3conducted by EPA in 2002. In comparison, as mentioned above, no 

references are provided to back the assumptions in the first document.

 Use of the above capital cost ratio to define the resource requirements for FGD 

upgrades and ESP modifications appear to be even more questionable, since making 

changes to existing equipment at the plant site may be more resource intensive 

compared to optimized methods usually employed to shop manufacture and install new 

equipment. We are requesting EPA to specifically review their assumptions for these 

two options shown to be exercised by a large number of GW capacity.

2. MATS Feasibility TSD, Page 11: A proposed timeline for the installation of environmental 

controls within the allowable compliance time period has been presented on this page. Please 

note that certain plants complying with the CSAPR would also be installing controls, FGD, SCR, 

etc., in about the same timeframe as that for MATS. In addition, several industrial facilities will 

be installing similar controls to comply with the industrial MACT. There is a concern that the 

combined impact of these three rules could be greater than that envisioned by EPA in this TSD. 

Can EPA responds to this comment?

3. MATS Acid Gas Floor, General Comment: A commenter is concerned about the application of 

dry sorbent injection (DSI) as a viable acid gas compliance alternative to flue gas desulfurization 

(FGD), and that its use has been overstated. This is based on the pollution control 

configurations of the units in the MATS acid gas floor.

In the proposed rule, there were 130 units used to calculate the acid gas MACT floor for existing 

units – this represents the best performing 12%. Of this 131, 11 units (less than 10%) had DSI 

installed. These units are plotted in Figure 1 (“MATS Acid Gas Floor Units Employing DSI”).

The largest eight units in Figure 1 (Montrose Units 1, 2, and 3; Ghent Unit 1; Cardinal Units 1 and 

2; Conesville Unit 4; Mountaineer Unit 1) use DSI solely for the purpose of SO3 control, not HCl 

or SO2. For acid gas control (as proposed under MATS), all eight of these units have FGD 

installed. The remaining three units with DSI installed (Arapahoe Unit 3; Cherokee Units 1 and 2) 

may not be representative of the type of plant that EPA has assumed is willing to install this 

technology. 

Cherokee Units 1 (107 MW) and 2 (106 MW) are both smaller, older units that have proposed 

retirement dates (the units came online in 1957 and 1959, respectively). In addition, there is a 

569 MW NGCC being constructed onsite which is expected to come online in 2015. Therefore, 

these units are likely using DSI as a cheap compliance option until retirement. 

 

3

“Engineering and Economic Factors Affecting the Installation of Control Technologies for Multipollutant 

Strategies,” EPA-600/R-02/073
Summary of Interagency Working Comments on Draft Language under 

EOs12866 and 13563 Interagency Review. Subject to Further Policy Review.

3

Likewise, Arapahoe Unit 3 (44 MW, online in 1951) has DSI installed, but also has an announced 

retirement date. Similar to the Cherokee Power Station, there is a 480 MW NGCC pending 

approval by the Colorado Public Utility Commission at the Arapahoe Station. Therefore, it may 

be the case that Arapahoe Unit 1 does not view DSI as a long term solution, but as a cheap, 

temporary method to control SO2 emissions until retirement.

It does not appear that there are any units in the MACT acid gas floor that are using DSI as a 

long-term compliance solution for acid gas control. Therefore, the willingness of industry to 

adopt DSI as a viable alternative to FGD may have been overstated.
Summary of Interagency Working Comments on Draft Language under EOs12866 and 13563 Interagency 

Review. Subject to Further Policy Review.

4

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

0 200 400 600 800 1000 1200 1400

C

u

m

ulativ

e

C

a

p

a

city (%)

Unit Size (MW)

Mountaineer Unit 1: 

DSI used for SO3 

control

Conesville Unit 4: 

DSI used for SO3 

control

Cardinal Unit 1, 2: DSI 

used for SO3 control

Ghent Unit 1: 

DSI used for SO3 

control

Montrose Unit 1, 2, 3: DSI 

used for SO3 control

Cherokee Unit 1,2:

Proposed 2011 retirement 

569 MW NGCC permitted, online in 2015

DSI likely being used as cheap compliance

solution until retirement

Arapahoe Unit 3:

Proposed 2013 retirement 

480 MW NGCC pending CO PUC approval

DSI likely being used as cheap compliance solution 

until retirement
Summary of Interagency Working Comments on Draft Language under 

EOs12866 and 13563 Interagency Review. Subject to Further Policy Review.

5

Additional Comments on the Preamble

Page 318, Table 3: Clarifications are requested for the following emission limits:

Existing Unit designed for Coal >8,300 Btu/lb, Mercury, 1.2E0 lb/Tbtu (2.0E-2 lb/GWh): 

These emission limits are only equivalent when the gross plant heat rate is ~16,667 

Btu/kWh, or a 20.5% efficient plant. This is not representative of an existing unit. 

Therefore, these are really two different limits. Which one will an existing unit be held to?

Page 572: We refer to the statement on this page: “Only those units that begin 

construction, modification, or reconstruction after May 3, 2011, will be affected by the final 

rule.” Will this apply retroactively to units meeting these criteria that already have air 

quality permits? There is a legal precedent (Xcel case) for preventing retroactive application 

of new permit levels for units that have already obtained permits.