UNITED STATES ENVIRONMENTAL P~OTECTION AGENCY 

REGIONS 

Ref: SENF-AT 

John T. Graves, P.E. 

Environmental Manager 

Minnkota Power Cooperative, Inc. 

1822 State Mill Road 

P.O. Box 13200 

1595 Wynkoop Street 

DENVER, CO 80202-1129 

Phone 800-227-8917 

http://www.epa.gov/region08 

DEC 2 3 2010 

Grand Forl(s, North Dakota 58208-3200 

Re: Request for Alternative Monitoring 

Dear Mr. Graves: 

In your letter to Mr. Joshua Rickard of my staff dated February 16, 2010, you requested 

the approval of alternative monitoring systems to the required continuous opacity monitoring 

systems (COMS) for both the Unit I and Unit 2 stacks at the Milton R. Young Station locate9. 

near Center, North Dakota. Based on your letter and subsequent conversations with Mr. Rickard, 

we understand Minnkota Power Cooperative, Inc. (Minnkota) proposes to install and operate 

continuous emissions monitoring systems for particulate rriatter·mass (PM CEMS) in lieu of the 

COMS currently required at 40 CFR .§ 60.45(a). The basis for your request is related to 

Minnkota installing a new wet flue-gas desulfurization (FGD) system on Unit I and upgrading 

the existing FGD system for Unit 2 pursuant to a consent decree. Both FGD systems will 

"scrub" 100 % of the flue gas entering them arid Minnkota indicates the flue gas exiting the FGD 

systems.will be saturated with water vapor and some entrained water droplets, affecting COMS 

accuracy due to water interference. 

We have reviewed your letter, the applicable regulations, previous determinations and 

considered phone conversations between yourself and Mr. Rickard. Based on our review, we 

determine the following: 

Installation and operation of· PM CEMS in lieu of C0MS: 

We approve the installation and operation of PM CEMS in li~u of COMS required at 

40 CFR § 60.45(a) and as required by the April 2006 Consent Decree. This approval is granted 

under the following conditions: 

1) The PM CEMS installed are appropriate to the stack conditions at both Units 1 and 2; 

2) The PM CEMS is installed, operated and maintained in accordance with the 

manufacturer's recommendations, the applicable requirements of 40 CFR 

§ 60.40 et~· and the General Provisions at 40 CFR §§ 60.7 - 60.13; 
3) The PM CEMS are installed prior to start.:.up of the boilers once the FGDs are iristtt!a;i-ill91ed.r.;---

4). Minnkota must certify the PM CEMS in accordance with performance specification 

11 (PS-1l)at40 CFR Part 60, Appendix A; . ~ . . ·. . .. · .. 

5) Quality.assurance/quality control requirements must be performed in accordance 

witl).,40 CFI{Part 60; Appendix F, Procedure 2; 

.{ ... • ~:) ~' :>-:;., . 

6) Compil~i~-~fth the PM emission limits at 40 CFR § 60.42(a), will be based on 

continuous three-hour rolling average periods during source operatiop; and 

7) Minnkota must meet all applicable reporting, recordkeeping and operational 

requiremen.ts urtder 40 CFR § 60.40 et seq. and the General Provisfons u.nder · 

40 CFR §§ 60.7 - 60.13. Quarterly excess emissions of PM will be reported 

based on a three-hour rolling average during source operation. 

Waive the requirement to install a COMS: . 

We approve your request to waive the requirement at 40 CFR § 60.45(a) to install a 

COMS. This waiver is conditional upon written agreement from Minnkota with the 

requirements above. 

Applicability of the current VE standards under 40 CFR § 60.40 et seq.: 

The opacity standards at 40 CFR § 60.42(b) shall remain applicable. The basis for this is 

that 40 CFR § 60.40~ gg. does not provide an option to waive an applicable opacity limit. 

Since the opacity limit at 40 CFR § 60.42(b) is an independently enforceable limit, we 

recognize it will be the responsibility of Minnkota to demonstrate compliance with the opacity 

limits for purposes of 40 CFR Part 60, Subpart D, even with the installation of PM CEMS. To 

address this requirement, we will allow Minnkota to demonstrate compliance with the opacity 

limit at 40 CFR § 60.42(b) by using visible emissions readings conducted in accordance with 40 

CFR Part 60, Appendix A, Method 9 (M9). 

The M9 readings must be taken by a certified observer in accordance with the following 

conditions which will become effective upon installation of the PM CEMS: 

1) Mirinkota will take weekly M9 readings, for at least 30 minutes each week, for six 

consecutive weeks during regular source operation; · 

2) If continuous compliance with opacity is demonstrated for six consecutive weeks, 

Minnkota can begin taking monthly M9 readings; 

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3) Monthly M9 readings must be taken for at least one hour each consecutive 

month but may be performed in no less than 30-minute intervals during regular 

source operation; 

4) Records of the M9 readings that document an exceedance of the opacity standard must be 

submitted with the quarterly excess emission reports required for the PM CEMS; and 

5) If excess emissions of opacity are identified, Minnkota must revert back to weekly 

M9 readings for six consecutive weeks, conducted in accordance with (1) above, 

or until continuous compliance with the opacity limit is demonstrated, whichever 

is longer. 

Monitoring/compliance protocol focus on Minnkota's PM emissions: 

We understand that the monitoring and compliance requirements of 40 CFR Part 60, 

Subpart D, under this alternative monitoring proposal, will focus on PM Emissions upon 

installation and certification of the PM CEMS. This does not, however, relieve Minnkota of its 

obligations to comply with the opacity limit at 40 CFR § 60.42(b). M9 readings conducted in 

accordance with the requirements outlined above will be the means by which Minnkota 

demonstrates compliance with the opacity limit at 40 CFR § 60.42(b). 

We look forward to working with Minnkota to finalize its proposal to install PM 

CEMS in lieu of COMS at the M.R. Young Station. If you have any questions related to this 

alternative monitoring approval letter, please feel free to contact Mr. Joshua Rickard at 

(303) 312-6460. 

cc: Terry O'Clair, NDOH 

7~:y, wt[p L 

\ r./ Cynthi~f5ds, Director D Technical Enforcement Program 

Office of Enforcement, Compliance 

and Environmental Justice 

Joshua Rickard, EPA, Region8 

Albion Carlson, EPA , Region 8 

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