June 15,2011 

Memorandum to the North Dakota Regional Haze SIP File 

Docket ID # EPA-R08-0AR-2010-0406 

Subject: August 3, 2010 Correspondence from the North Dakota Department of 

Health (Supplement No.1 to the North Dakota SIP for Regional Haze) 

From: Gail Fallon, Environmental Engineer 

Environmental Protection Agency, Region 8 

This is to document that EPA replaced pages in the original SIP submittal as 

requested per the subject correspondence. Attached to this memorandum is the one page 

containing errors which were removed. A copy ofthe subject correspondence and 

corrected pages is included in the docket. 
future emissions inventory was modified to reflect the control technology for each candidate 

source (A VS I EGU, A VS 2 EGU, Coyote EGU, and Tioga Gas Plant), and modeling was 

conducted using the revised future inventory for one source at a time. The reasonable progress 

goals in 40 CFR 51.308( d)( 1) requires improvement in the most impaired days. The most 

impaired days are defined in 40 CFR 51.301 as the average visibility impainnent for the twenty 

percent days with the highest amount of visibility impainnent. Therefore, modeling addressed 

the 20% worst days for both TRNP and L W A Class I areas. The results for each candidate 

source were compared with the results using the unmodified future emissions inventory (Table 

8.11) to detennine the additional visibility improvement due to the tested control technology. 

Modeled visibility improvement, for each candidate source/technology, is provided in Table 9.9. 

The single source controlled emissions (modeled tons per year) and annualized cost effectiveness 

(dollars per deciview) are also reported in the table. Reported visibility improvement (in 

deciviews) reflects the higher value for either TRNP or L W A. Note that visibility improvement 

reported for Coyote represents the total for both S02 and NOx control technologies, and the 

improvement reported for the Tioga Gas Plant represents the total for all 1920 and 2350 

horsepower engines. As shown in the table, predicted visibility improvement is very marginal 

for all candidate sources/technologies, and consequently cost per deciview is very high. 

Table 9.9 


Visibility Improvement and Cost Effectiveness 


Visibility Visibility 

Improvement Improvement Cost 

Source Pollutant 

Control 

Technolo2Y 

Emissions 

(TPy) 

(dv)* (0/0 *** Effectiveness 

TRNP LWA TR.~P LWA (S/dv)**

AVS1 NO. LNB+SNCR 2358 0.005 om 0.03 0.05 1,124,000,000 

AVS2 NO. LNB+SNCR 2,144 0.005 om 0.Q3 0.05 1,124,000,000 

Coyote S02 

NO. 

Wet Scrubber 

ASOFA+SNCR 

1,924 

5,871 

0.02 0.04 0.11 0.20 1,113,000,000 

TiogaG.P. 

1920 BHp Engines NO. LEC Retrofit 268 0 0.5 0 0.26 21,200,000 

2350 BHp Engines NO. SCR 33 

*The less efficient technologies evaluated would provide less improvement. 


**Based on the maximum visibility improvement (per source) at any Class I area in North 


Dakota. 


***Improvement (%) from baseline conditions. 


Time Necessary for Compliance 

Up to 6.5 years after SIP approval is necessary to achieve compliance (see EC/R report in 

Appendix I.l). Additional time may be necessary if nonnal maintenance outages do not coincide 

with the projected schedule. It is anticipated that all required changes could be implemented by 

2018 depending on the date of approval of this SIP. It is not anticipated that any of the 

remaining sources will be retired prior to 2018. 

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