STATE OF CALIFORNIA THE RESOURCES AGENCY ARNOLD SCHWARZENEGGER, Governor

CALIFORNIA ENERGY COMMISSION

1516 NINTH STREET

SACRAMENTO, CA 95814-5112

January 22, 2009

Tim Hemig Director, Environmental & New Business NRG Energy, Inc. 1817 Aston Avenue, Suite 104 Carlsbad, CA 92008

Dear Mr. Hemig:

CARLSBAD ENERGY CENTER PROJECT (07-AF C-6) AIR QUALITY DATA REQUEST SET 4

Attached are Data Requests 142-158, which wil l be docketed as Data Request Set 4 for the Carlsbad Energy Center Projec t (CECP) proceeding. These data requests are made pursuant to Title 20, section 1716(c) of the California Code of Regulations.

The following air quality data requests are issued in order for staff to more fully appreciate and understand potential CECP air emission conditions based on analysis conducted by the San Diego Air Pollution Control District (Dis trict). Specifically, staff seeks to follow-up on comments made by the applicant in its January 5, 2009 letter on the Dis trict’s Preliminary Determination of Compliance (PDOC). As you remember, staff i ndicated that clarifications (em bodied in this data request set) may become necessary during the Preliminary Staf f Assessment Workshop’s air quality discussion
held at the Carlsbad Sheraton on the evening of January 7, 2009.

Regulations allow 30 days for written responses to the enclosed data requests (meaning all data responses would be due to the Energy Commission st aff on or before February 23, 2009). If you are unable to provide the information requested, need additional time, or object to providing the requested information in the manner discussed abov e, please send a written notice to the Committee and me within 20 days of receipt of this not ice. The notification must contain the reasons for the inability to provide the information or the gr ounds for any objections (see Title 20, California Code of Regulations, section 1716 (f)). As always, if you have any questions, please call me at (916) 654-4894, or email me at mike.monasmith@energy.state.ca.us

.

Sincerely,

Mike Monasmith Siting Project Manager

Enclosure

cc: POSCarlsbad Energy Center Project, Data Request Set 4 Page 2 Technical Area: Air Quality

Author : William Walters and Keith Golden

Based on the San Diego Air Pollution Contro l District’s Preliminary Determination of Compliance (PDOC) and Carlsbad Energy Center LLC’s (applicant’s) subsequent January 5, 2009 comment letter, a number of operational scenarios were proposed that were not previously explained fully in the Applicat ion for Certification (AFC), subsequent data responses, or in the Project Enhancement and Refinement (PEAR) document. Staff needs additional information on these oper ational scenarios, including: what circumstances would require specific permit conditions that addre ss these operational scenarios; the emission limits necessary and the duration scenarios.

BACKGROUND: INITIAL COMMISSIONING AND SHAKEDOWN

In the AFC, Carlsbad Energy Center, LLC ( applicant) described a Commi ssioning period of 49 days for each turbine, and amended that to appr oximately 60 days for each turbine in the PEAR document. Yet, the PDOC allows for a Commissioning period of 120 days per turbine. In addition, the PDOC includes an additiona l 60 day period after Commissioning and before commercial operation called Shakedown, whic h had previously not been addressed in the AFC. Staff needs clarification as to the changes to the Commissioning per iod for the project.

DATA REQUESTS

142. Please describe whether the applicant requested the additional time for the Commissioning and Shakedown periods per new data/information from the turbine manufacturer (Siemens-Westinghouse), or if other relevant information resulted in the additional 60 days in the time peri od necessary for the Commissioning period

for each turbine.

143. If the additional Shake down period was requested by the applicant, then please provide a description of this Shak edown period and how it differs from Commissioning. Describe why it is necessa ry to have this additional period known as Shakedown before the project is deeming commercially operational.

144. Please identify whether the applicant would be willing to stipulate to the Commissioning period, without the additional Shakedown period, as identified in the PEAR document, or some other period(s) for one or both that are shorter than currently allowed in the PDOC.

BACKGROUND: TUNING

The PDOC defines tuning (Condit ion 13) as “adjustments to the combustion or emission control system that involves operating the com bustion turbine or emission control system in a

manner such that the emissions control equipment may not be fully effective or operational.” Staff needs clarifications as to what specif ic “adjustments to the combustion or emission control systems” will occur, why they will occur, and how often they will occur.Carlsbad Energy Center Project, Data Request Set 4 Page 3 DATA REQUESTS

145. Please describe why and what “adjustm ents” will be made to the combustor cans
and/or the Selective Ca talytic Reduction system.

146. Please describe the frequency these adjustments will be made and whether they

would occur at the time of the typical annual maintenance period.

147. Please define the NOx and CO emission concentrations and hourly emission rate (lb/hr) that are necessary during a t uning event. Please describe the turbine loading and operation of emission contro l systems during a tuning event. Also quantify the number of hours annually that the Combustion Turbine Generator (CTG) would be undergoing tuning and be subjec t to the higher emission limits.

BACKGROUND: TRAN SIENT LOAD CHANGE

Condition 15 of the PDOC defines a trans ient load change when the combustion turbine exceeds 50 MW per minute change. Subs equently, applicant’s January 5, 2009 comment letter states that at load changes as low as 5 MW per minute the NOx BACT levels of 2.0 ppm cannot be met. This would imply that at only times when the project is not subject to load changes could the turbine meet the 2.0 ppm limit. The applicant is requesting (through its January 5, 2009 comment letter) for 15 hours per year per turbine cumulatively for all qualifying conditions to exclude the 2.0 ppm hourly emission conc entration limit and replace it with a 12 ppm hourly concentration limit. Staff needs clarification of the various operational scenarios discussed in the applicant’s January 5, 2009 comment letter to fully understand what those scenarios are, how they would be known to occur, and their justification.

DATA REQUESTS

148. Please confirm that applicant’s propos ed condition XX from its January 5, 2009 PDOC comment letter (which describes four qualifying events/conditions for equipment operation), is meant to cover all transient load events where NOx emission exceptions are sought; and please revise the requested change so that it makes this point clear. In addition, please clarify that this qualifying event language is only for NOx, and is not being requested fo r any other pollutant, such as CO and

VOC.

149. Please discuss why the applicant would bid their project to meet either California ISO or SDG&E resource needs, when the project appears incompatible with the ramp rates required by the bid specificati ons. Please include in this discussion if changes could be made to the project to allow it to meet all the bi d specifications.

150. Should the project be excl uded from bidding on certain re source bids, or should the project be bundled with other gener ation resources (such as a simple-cycle peaker) to ensure all bid specifications can be met within the permit limits?

151. Please discuss when the California ISO w ould initiate the operation of the project
under Automatic Generation Control. Incl ude in this discussion how the California ISO would achieve control of the proj ect and what is meant by Automatic
Generation Control.Carlsbad Energy Center Project, Data Request Set 4 Page 4 152. Please provide historical circumstances within the last th ree years where the
California ISO has initiated control of a power plant under Automatic Generation Control. Please provide the documentation from the California ISO that such

Automatic Generation Control events occurred.

153. The January 5, 2009 letter requested that the 2 ppm NOx limit not apply during, “Rapid gas turbine load changes due to acti vation of a plant automatic safety or equipment protection system which rapidly decreases turbine load.” Please discuss why it is not sufficient to re ly on the District Rule 98 (Breakdown Conditions: Emergency Varianc e) instead of trying to fo rmulate a permit condition that appears to cover a br eakdown circumstance.

154. Please discuss why the initiation and s hutdown of the inlet air cooler would adversely affect complying with the 2 ppm NOx concentration. Please provide substantiation that a Siemens Rapid Resp onse SCC6-5000F turbine unit with an evaporative inlet air cooler needs an exempti on from the 2 ppm NOx concentration.

155. Please define the NOx and CO emission concentrations that are anticipated during the initiation and shutdown of the evaporat ive inlet air cooler. Also quantify the number of annual operation hours for this scenario.

156. The applicant requests in its January 5, 2009 PDOC comment letter the following language exempting the 2 ppm NOx concentration be added to the permit

conditions: “Events as the result of technological limitation identified by the operator and approved in writ ing by the District.” This language appears to be overly broad and open-ended. Please clarif y the intent of this language and the

technical reasons and “technol ogical limitations” that co uld arise that would be included under this exemption.

157. Please estimate the maximum hourly NO x emissions associated with the 12 ppm concentration requested for the qualified transient load events and confirm that, assuming both turbines are concurrently operating under the 12 ppm limit, that these emissions do not result in the potentia l for impacts greater than those already modeled and analyzed for worst-case 1-hour NOx emission events.

BACKGROUND: Permit Applicab ility Determination (PSD)

The San Diego County Air Pollution Control Distric t’s (District) Preliminary Determination of Compliance (PDOC) finding for PSD permi t applicability was based on the District’s interpretation of their own regulations rather than a strict interpretation of U.S.EPA PSD applicability emission calculation requirements. Since the District is not currently delegated PSD permitting authority from t he U.S.EPA, and the appl icant has not formally requested a PSD permit applicability finding from U.S.EPA staf f is concerned about th e validity of the PSD permit applicability finding. Staff needs the applic ant to provide a PSD applicability analysis, based on Federal PSD statute requi rements, in order to accu rately assess the PSD permit applicability and complete the Laws, Ordinances, Re gulations, and Statutes (LORS) findings for this project.Carlsbad Energy Center Project, Data Request Set 4 Page 5 It is staff’s belief through conversations with U. S.EPA staff that the per tinent section in the PSD regulation is 40 CFR Part 52.21 (b)(48)(i ), which specifies the requirements for determining baseline actual emissions from ex isting electric utility steam generating units, including requirements for non-comp liant operations and multiple emission units. The specific

issues most relevant to the assessment for the proposed project are the fact that the baseline must be based on the average annual emissions for a 24-month consecutive period that is the same for all of the multiple units, alt hough not necessarily the same 24-month period for each pollutant, and that the 24-month period mu st be within 5 years immediately preceding the actual construction date. Since the proj ect may not begin construction until sometime during 2009, it appears that woul d limit the period to the ma ximum 24-month emission period from no earlier than 2004 through the present.

DATA REQUEST

158. Please provide, according to federal PSD statute requireme nts for the actual emission baseline calculations for power plants, the applicant’s PSD permit applicability assessment for both NO 2 and PM10 emissions. Please note that staff will likely request that U. S.EPA review this assessment for concurrence.