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 32010

Grand Forl(s, North Dakota 58208-3200 Re: Request for Alternative Monitoring Dear Mr. Graves: In your letter to Mr. Joshua Rickard ofmy staffdated February 16, 2010, you requested the approval ofalternative monitoring systems to the required continuous opacitymonitoring systems (COMS) for both the Unit I and Unit 2 stacks at the Milton R. Young Station locate9. near Center, North Dakota. Based onyour letter and subsequent conversations with Mr. Rickard, we understand Minnkota PowerCooperative, Inc. (Minnkota) proposes to install and operate continuous emissions monitoring systems for particulate rriatter·mass (PM CEMS) in lieu ofthe COMS currently required at40 CFR.§ 60.45(a). Thebasis for yourrequest 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 pursuantto a consent decree. Both FGD systems will "scrub" 100 

### % ofthe flue gas entering them arid Minnkotaindicates the flue gas exitingthe FGD systems.will be saturated with water vapor and some entrained waterdroplets, affecting COMS accuracy due to water interference. We have reviewed your letter, the applicable regulations, previous determinations and considered phone conversations between yourselfand Mr. Rickard. Based on ourreview, we determine the following: Installation and operation of·PM CEMS in lieuof C0MS: We approve the installation and operation ofPM CEMS in**li~u** of COMS required at 40 CFR 

### §60.45(a) and as required bythe April 2006 Consent Decree. This approval is granted underthe following conditions: 1) The PM CEMS installed are appropriate to the stack conditions atboth Units 1 and 2; 2) The PM CEMS is installed, operated and maintained in accordance with the manufacturer's recommendations, the applicable requirements of40 CFR 

### § 60.40**et~·** and the General Provisions at40 CFR 

### §§ 60.7

- 60.13;

### 3) The 

## PM CEMS are installedpriorto start.:.up ofthe 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 CFRPart 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 at40 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 ofPM will be reported based on athree-hourrolling average during source operation. Waive the requirementto install a COMS:

. We approve yourrequest to waive the requirement at 40 CFR 

### §60.45(a) to install a COMS. This waiveris conditional upon written agreement from Minnkota with the requirements above. Applicability ofthe current VE standards under40 CFR §60.40 

### etseq.: 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 ofMinnkotato demonstrate compliance with the opacity limits for purposes of40 CFR Part 60, Subpart D, even with the installation of PM CEMS. To address this requirement, we will allow Minnkotato demonstrate compliance with the opacity limit at 40 CFR § 60.42(b) by using visible emissions readings conducted in accordance with 40 CFRPart 60, AppendixA, Method 9 (M9). The M9 readings mustbe taken by acertified observer in accordance with the following conditions which will become effective upon installation ofthe 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, Minnkotacan begin taking monthly M9 readings;



### 23) Monthly M9 readings must be taken for at leastone hour each consecutive month but may be performed in no less than 30-minute intervals during regular source operation; 4) Records ofthe M9 readings that document an exceedance ofthe opacity standard must be submitted with the quarterly excess emissionreports required for the PM CEMS; and 5) Ifexcess emissions ofopacity 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 of40 CFR Part 60, Subpart D, under this alternative monitoring proposal, will focus on PM Emissions upon installation and certification ofthe PM CEMS. This does not, however, relieve Minnkota ofits 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 Minnkotato finalize its proposal to install PM CEMS in lieu ofCOMS at the M.R. Young Station. Ifyou 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 ofEnforcement, Compliance

and Environmental Justice

Joshua Rickard, EPA, Region8 Albion Carlson, EPA , Region 8

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