March 11, 2011

In Reply Refer To: AIR-3 SAC 06-01

Steve Royall SeniorPlant Manager Colusa Generating Station 4780 Dirks Road Maxwell, California 95955



### Re: Administrative Amendmentto Prevention ofSignificantDeterioration Permit for Colusa Generating Station, PSD PermitNo. SAC 06·01

Dear Mr. Royall:

This letter is in response to your request dated January 7, 2011 for technical corrections to the Prevention of Significant Deterioration (PSD) permit issued to the Pacific Gas and Electric Company (PG&E) on September 29,2008, as amended on March 19,2010, for the construction and operation of the Colusa Generating Station (CGS) in Colusa County, California. You state that several short-term emissions limits for "startup" periods in the PSD permit were incorrectly transposed and request that these emission limits be relocated to appropriately reflect facility operations during different startup periods. For the reasons discussed below, I am approving these corrections as administrative amendments to the PSD permit.

Specifically, you state that several ofthe pound per hour (lb/hour) emission limits in the PSD permit for nitrogen oxides (NOx) and carbon monoxide (CO) emissions during "startup" periods, as provided in the table in Condition X.E.5 of the permit, were placed incorrectly and should be relocated to appropriately reflect facility operations during "cold startup," "warm startup," and "hot startup" periods. I Condition X.E.5 establishes, among otherthings, the following emission limits during "startup" periods: (1) for NOx, 333.3 lb/hour during cold startup, 152.0 lb/hour during warm startup, and 249.90 lb/hour during hot startup; and (2) for CO, 373.61b/hour during cold startup, 370.3 lb/hour during warm startup, and 429.61b/hour during hot startup. You state that typical permit conditions for this type of facility provide for the highest emissions during a "cold startup," followed by lower emissions during a "warm startup" and the lowest emissions during a "hot startup." Accordingly, you request that we reverse the NOx limits for "warm" and "hot" startup (resulting in 249.90 lb/hour during warm

I Condition X.E. 9 of the PSD permit defines "startup" as the period beginning with ignition and lasting until the equipmenthas reached a continuous operating level and meets the permit limits specified in Condition X.D.3. of the permit. Condition X.E.9 also defines "cold startup," "warm startup," and "hot startup."startup and 152.0 lb/hour during hot startup), and that we transpose all three CO limits (resulting in 429.61b/hourduring cold startup, 373.61blhourduring warm startup, and 370.3 Ib/hour during hot startup).

We agree that a facility ofthis type generally requires the highest ofstartup emissions during a cold startup, followed by lower emissions during a warm startup and the lowest emissions during a hot startup. We also agree with your conclusionthat the startup emissions limits for CGS in Condition X.E.5 ofthe PSD permit appear to have been incorrectly transposed and that technical corrections are appropriate to reflect CGS's operations during these different startup events. These corrections to the PSD permit for CGS do not alter our prior BACT or ambient air quality impacts analyses and will not result in more than de minimis emissions Increases.

For these reasons, we are processing the corrections you have requested as administrative amendments to the PSD permit for CGS, effective immediately. In addition, we are updating the facility's address on the PSD permit. We have attached the amended permit. Ifyou have any questions, please contact Shaheerah Kelly ofour Permits Office at (415) 947-4156 or kellv .shaheerahupepa.gov

. Sincerely,

Deborah Jordan Director, Air Division

Enclosure: Amended PSD Permit

cc: Jon Maring, Pacific Gas and Electric Company, Roseville, CA Harry Krug, Colusa County Air Pollution Control District T. J. Gomez, Colusa County Air Pollution Control District Robert Fletcher, CaliforniaAir Resources Board Dale Rundquist, CaliforniaEnergy Commission Chris Davis, CaliforniaEnergy Commission Jerry Salamy, CH2M Hill