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<" j ENVIRONMENTAL HEALTH SECTION

Gold Seal Center, 918 E. DivideAve.

# ~~ NORTH DAKOTA Bismarck, ND 58501-1947**~~** DEPARTMENT

### oj HEALTH 701.328.5200 (fax) www.ndhealth.gov
August 3, 2010

Mr. James Martin (8RA) Regional Administrator U.S. EPA, Region 8 1595 Wynkoop Street Denver, CO 80202-1129 Re: SupplementNo. 

### 1to theNorth Dakota StateImplementation Planfor Regional Haze DearMr. Martin: Accompanying this letter is a letter from Governor Hoeven to Administrator Jackson formally submitting a supplement to the North Dakota State Regional Haze State Implementation Plan. The supplement includes a Reasonable Progress analysis for the R.M. Heskett Station Unit 

### 2. Enclosed are two hardcopies and three electronic copiesofthe supplement. Also enclosed is a revised page 186 ofthe original Regional Haze State Implementation Plan which was submitted in March. Table 9.9 has been corrected to indicate the visibility improvement from the proposed changes at the Tioga Gas Plant would improve visibility 0.05 deciviews at Lostwood WildernessArea (not0.5 as indicated in the originalanalysis). If you have any questions, please have your staff contact Tom Bachman of my staff at (701)328-5188. 

# ;:;cJd

Terry L. O'Clair, P.E. Director DivisionofAirQuality 

### TLOITB:cse RECEIVED Ene: xc: Gail Fallon, EPA Region 8 U.S. EPA Region8 M'sOffice

Environmental Health Division of Division of Division of Division of Section ChiefsOffice AirQuality Municipal Facilities Waste Management WaterQuality 701.328,5150 701.328.5188 701.328.5211 701.328.5166 701.328.5210 Printedon recycledpaper.future emissions inventory was modified to reflect the control technology for each candidate source (AVS 1 EGU, AVS 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 impairment for the twenty percent days with the highest amount ofvisibility impairment. 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 determinethe additional visibility improvementdue to thetested control technology. Modeled visibility improvement, for each candidate source/technology, is provided in Table 9.9. The single source controlledemissions (modeled tons peryear) and annualizedcosteffectiveness (dollars per deciview) are also reported in the table. Reported visibility improvement (in deciviews) reflects the higher value for either TRNP orLWA. 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 consequentlycostperdeciviewis veryhigh.

Table9.9 VisibilityImprovementandCostEffectiveness 

### I Visibility Visibility 

# : Improvement Improvement Cost i Control Emissions 

### I (dv)* (% *** Effectiveness I Source Pollutant Technology (TPY) TRNP LWA TRNP LWA ($/dv)**

AVSI NO. LNB+SNCR 2,358 0.005 0.01 0.03 0.05 1,124,000,000 AVS2 NO. LNB+SNCR 2,144 0.005 0.01 0.03 0.05 1,124,000,000 Coyote S02 Wet Scrubber 1,924 0.02 0.04 0.11 0.20 1,113,000,000 NO. ASOFA+SNCR 5,871 TiogaG.P. 1920 BHp Engines NO. LEC Retrofit 268 0 0.05 0.26 

# I 0 21,200,000 2350 BHp Engines NO. SCR 33 

# I
*The less efficienttechnologiesevaluated 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 Necessaryfor Compliance Up to 6.5 years after SIP approval is necessary to achieve compliance (see EC/R report in Appendix 1.1). Additional time may be necessary ifnormal maintenance outages do not coincide with the projected schedule. Itis 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 priorto 2018.

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