06-3998. Draft General Conformity Determination for Proposed Operations of Southwest Airlines Co. at Denver International Airport, Denver, CO

AGENCY:

Federal Aviation Administration (FAA), Department of Transportation (DOT).

ACTION:

Notice of Draft General Conformity Determination.

SUMMARY:

The FAA is issuing this notice to advise the public that a Draft General Conformity Determination (DGCD) for Proposed Operations of Southwest Airlines Co. (Southwest) at Denver International Airport (DEN) has been prepared. In accordance with Section 176(c) of the Clean Air Act, FAA has assessed whether the emissions that would result from FAA's action in approving the proposed operation specifications (OpSpec) for Southwest's proposed operations at DEN conform with the Colorado State Implementation Plan (SIP).

DATES:

Submit comments on or before May 30, 2006.

ADDRESSES:

You may submit comments, identified by docket no. FAA-2006-24508 by any of the following methods:

• DOT docket Web site: Go to http://dms.dot.gov and follow the instructions for sending your comments electronically.
• Government-wide rulemaking Web site: Go to http://www.regulations.gov and follow the instructions for sending your comments electronically.
• Mail: Docket Management Facility, U.S. Department of Transportation, 400 Seventh Street, SW., Nassif Building, Room PL-401, Washington, DC 20591.
• Fax: [phone].
• Hand delivery: Room PL-401 on the plaza level of the Nassif Building, 400 Seventh Street, SW., Washington, DC, between 9 a.m. and 5 p.m., Monday through Friday, except Federal holidays.

After all comments are reviewed and addressed, a notice of availability of the Final General Conformity Determination will be published.

Instructions: All submissions received must include the agency name and docket number or Regulatory Information Number (RIN).

For Technical Information Contact: Joan Seward, All Weather Operations Program Manager, ASW-230.1, FAA SW Region Headquarters, 2601 Meacham Blvd., Fort Worth, TX 76137, telephone [phone], e-mail: [e-mail].

SUPPLEMENTARY INFORMATION:

In December of 2005, Southwest announced its intent to begin scheduled service at DEN commencing in January 2006. As required by Title 14 of the Code of Federal Regulations (14 CFR) 119.51, Southwest applied to the FAA to amend Southwest's OpSpecs to include DEN, thereby authorizing Southwest to conduct DEN service. The request to the FAA detailed Southwest's startup plans, commencing on January 3, 2006, with 13 daily landing/take-off cycles (LTO),^[1] equating to a total of 26 operations, and contained other information for the FAA to conduct the environmental review required under the regulations implementing the National Environmental Policy Act (NEPA) (40 CFR 1500-1508), section 176(c) of the Clean Air Act (40 CFR 93.150 et seq.), and by FAA Order 1050.1E, Environmental Impacts: Policies and Procedures. At that time Southwest indicated an interest in increasing operations to as many as 50 or 60 daily operations at DEN, but agreed to maintain operations at DEN below de minimis levels until a General Conformity Determination could be completed.

The FAA issued an OpSpec to Southwest for this initial level of activity accompanied by an environmental categorical exclusion dated December 14, 2005, determining that the daily 13 LTOs were below de minimis emission levels and were not regionally significant. Therefore, the no further determination was required under the General Conformity rule.

Southwest subsequently announced a scheduled increase of service planned for March 2006 with an additional 9 daily LTOs, bringing the total expected daily LTOs to 22. This General Conformity Determination addresses FAA's proposed Federal action to amend Southwest's OpSpecs to accommodate future operations as high as 60 daily LTOs at DEN (hereto known as the “Proposed Action”). The information presented in this DGCD demonstrates conformance with Colorado's SIPs and substantiates that the net emissions resulting from Southwest's increased service at DEN are not regionally significant.

Air Quality Designations for the Denver Metropolitan Area

DEN is owned and operated by the City and County of Denver, and is located within the Denver Metropolitan Area (DMA) for air quality planning purposes. The DMA is designated as attainment for the criteria pollutants sulfur dioxide (SO₂), nitrogen dioxide (NO₂), lead, and particulate matter with aerodynamic diameter of 2.5 micrometers or less (PM_2.5).

The DMA is an Environmental Protection Agency (EPA) designated attainment/maintenance area for the criteria pollutants carbon monoxide (CO), particulate matter with aerodynamic diameter of 10 micrometers or less (PM₁₀), and the 1-hour ozone national ambient air quality standard (NAAQS). In addition, DEN is located in an Early Action Compact (EAC) area for the 8-hour ozone standard, which has a deferred air quality designation date of December 31, 2006.

Pursuant to the Clean Air Act, Federal actions in nonattainment and maintenance areas are required to conform with SIPs to either bring an area into compliance with the NAAQS or maintain compliance with the NAAQS.

FAA approval to amend Southwest's OpSpecs for DEN constitutes a Federal action required to conform to Colorado's SIPs for CO, PM₁₀, and the EAC requirements for the 8-hour ozone standard.

General Conformity Applicability Analysis

Section 176(c) of the Clean Air Act prohibits the Federal government from engaging in, supporting, providing financial assistance for, licensing, permitting, or approving any activity that does not conform to an applicable implementation plan. A general conformity determination may be required for each pollutant where the net direct and indirect emissions in a nonattainment or maintenance area caused by the action exceed de minimis levels (40 CFR 93.151(b)). In addition to the de minimis applicability analysis, a conformity evaluation of Federal actions must also demonstrate the Proposed Action does not constitute a regionally significant action, which is defined as an action that contributes 10 percent or more of total basin-wide emissions.

DMA's pollutants of concern for general conformity purposes include CO, PM₁₀, and the precursors of ozone, namely volatile organic compounds (VOCs) and oxides of nitrogen (NO_X).^[2] An analysis must be performed to determine if the net annual emissions of these pollutants resulting from the Proposed Action exceed General Conformity de minimis thresholds. For DMA, the General Conformity de minimis thresholds are 100 tons per year for each pollutant of concern.

Emissions Inventory

To determine the net effect of the proposed project, an emissions inventory of reasonably foreseeable, direct, and indirect emissions caused by the Federal action was performed to calculate the difference between the Proposed Action scenario—Southwest's foreseeable maximum activity level at DEN, and the No Action scenario—no service by Southwest at DEN.^[3] The evaluation was performed using the FAA's Emissions and Dispersion Modeling System (EDMS) version 4.4. Under the Proposed Action, no facility improvements would required (e.g., new parking facilities, aircraft gates, etc.) to accommodate the Proposed Project. Therefore, the sources considered in the emissions inventory were limited to aircraft operations and supporting equipment (ground support equipment (GSE) and auxiliary power unit (APU)), surface transportation, and parking lots.

Aircraft and Supporting Equipment Emissions

Under the No Action alternative, Southwest's operations would not be introduced at DEN, therefore no emissions from aircraft operations would occur. Similarly, no change in either APU emissions or (GSE) emissions would occur. Although the extent and timing of potential increases in Southwest's flight activity in the Proposed Project are imprecise, the airline's business plan indicates that earliest possible calendar year that the maximum foreseeable aircraft activity of 60 daily LTOs could be achieved is 2007. Under the Proposed Action scenario, aircraft emissions were quantified based on this maximum foreseeable level and conservatively assumed to occur every day of the year for a total of 10,950 LTOs per year. To match Southwest's fleet and registered engines, emissions were calculated from CFM56-3B1, CFM56-3B2, CFM56-7B22, and CFM56-7B24 engines proportionately to the number of aircraft/engine combinations registered in Southwest's national fleet (see Table 1).

Table 1.—Southwest Aircraft Information and Potential Maximum Activity at DEN

Aircraft type	Engine	National quantity*	Percent of national fleet (percent)	Maximum daily LTOs	Maximum annual LTOs
B733/B735	CFM56-3B1	202	47.5	28	10,220
B733	CFM56-3B2	17	4.0	2	730
B737-700	CFM56-7B22	204	48.0	29	10,585
B737-700	CFM56-7B24	2	0.5	1	365
Totals		425	100	60	21,900
* BACK database, April 2005.

Southwest has indicated that it will use the available gate electrification at DEN. Gate electrification supplies power to an aircraft while parked at airport gates by enabling connection of the aircraft's systems to 400hz electrical power. The result is that the use of the aircraft's auxiliary power units (APUs) is reduced, which, in turn, reduces the associated combustion pollutants. Typically, with gate electrification, APU usage is minimized to approximately 8 minutes per LTO. Southwest employs Allied Signal model GTCP85-129 APUs on their B737-300s and Allied Signal model 1319B APUs on their B737-700s.

Southwest has identified the individual types and quantities of ground support equipment (GSE), and time duration dedicated to each aircraft LTO. Table 2 presents the GSE information that was used to calculate emissions for the Proposed Action scenario.

Table 2.—Southwest GSE Fleet Information per LTO at DEN

GSE description	Quantity	Fuel	Minutes of operation per vehicle per LTO
Aircraft Tug	1	Diesel	5
Baggage Tug	2	Electric	20
Lavatory Truck	1	Diesel	10
Baggage Belt Loader	2	Diesel	20
Hydrant Fueling Truck	1	Diesel	10
Source: Southwest Airlines, 2005.

Surface Transportation Emissions

Under the No Action alternative, Southwest's operations would not be introduced at DEN, therefore no additional emissions from increased surface transportation to/from DEN would occur. As a result of the Proposed Action, the employees of Southwest Airlines will induce new origin and destination (O&D) traffic to and from DEN. Over the years, the City and County of Denver has worked with the Denver Regional Council of Governments (DRCOG), which is the metropolitan planning organization (MPO) for the DMA, to include airport-related O&D traffic and emissions in DRCOG's regional traffic and air quality models, respectively. DRCOG estimates and forecasts vehicle miles traveled (VMT) for the region by compiling traffic data, population data, and employment data. Specifically, DRCOG estimates O&D traffic for DEN based upon data supplied by the City and County of Denver. DRCOG then models all traffic and associated emissions for transportation conformity purposes. This General Conformity Determination does not include emissions from Southwest Airlines employee traffic because DRCOG and the City and County of Denver have already taken steps to ensure that future employee traffic, such as Southwest's, and the associated future emissions are included in the conforming regional transportation plan for the DMA.

Parking Lot Emissions

In the No Action alternative, no additional parking lot emissions would be generated from passengers or Southwest employees. The increase in parking lot emissions resulting from the increased Southwest employee vehicular traffic to DEN associated with the proposed action was calculated using the assumption that each proposed Southwest employee would arrive and depart DEN daily in the employee's own vehicle.

Results of the Emissions Inventory

For determining general conformity applicability, the net increases of each pollutant of concern, if any, is determined by calculating the difference in emissions between the Proposed Action—taking into account not only additional emissions resulting from the action itself, but also any decreases in emissions which may result—and the No Action alternative. Table 3 presents the total emissions increase from the Proposed Action and the comparison to the General Conformity de minimis thresholds. The Proposed Action exceeds the de minimis thresholds for the pollutants of CO and NO_X. As a result, a General Conformity determination is required.^[4]

Table 3.—Net Emission Increases From the Proposed Action and Comparison to De Minimis Thresholds

[Tons per year]

Category	CO	VOC	NOX	SOX	PM10/PM2.5
Aircraft	260.798	22.754	195.110	19.413	2.199
APU	3.999	0.269	2.052	0.358	unavailable
GSE	2.543	0.660	6.889	1.216	0.530
Parking	<0.001	<0.001	<0.001	<0.001	<0.001
Total	267.339	23.682	204.051	20.985	2.728
de minimis threshold	100	100	100	not applicable	100
Source: FAA Emissions Dispersion Modeling System version 4.4.

Table 4.—Comparison of Proposed Action Emissions to the SIP Regional Inventories

Pollutants of concern	Units	Daily emissions from proposed action	Original SIP maintenance plan	SIP maintenance plan update	Is the proposed action regionally significant?
CO	(tons/day)	0.732	1,125.4 to 1,203.3	1,736.9 to 1,864.9	No.
PM10	(tons/winter day)	0.007	66.9 to 95.6	62.3 to 107.5	No.
VOC	(tons/summer day)	0.065	459 to 507	NA	No.
NOX	(tons/summer day)	0.559	308 to 332	303.3 to 353.3*	No.
* Updated regional NOX values were listed in the PM10 Maintenance Plan Update.

General Conformity Determination

Under the General Conformity regulations, the FAA can utilize a number of criteria for demonstrating conformity with SIPs. For this determination, the FAA believes it is appropriate to utilize the criterion of demonstrating that emissions for the Proposed Action are specifically identified and accounted for in the SIP maintenance plans under 40 CFR 93.158(a)(1). The FAA has reviewed specific SIP maintenance plan documentation to affirm that the City and County of Denver's airport emissions inventory for DEN was included in the SIP maintenance plans by the State and regional air quality agencies. In a letter dated April 5, 2006, the Colorado Department of Public Health and Environment confirmed the emissions associated with the Proposed Action are reasonably accounted for in the Colorado SIPs. The FAA recognized that the SIP maintenance plans for the DMA include the future aviation activity levels predicted for the airport. The aircraft emissions included in the Technical Support Documents for the 2000 CO Maintenance Plan, the 2001 PM₁₀ Maintenance Plan, the 2001 1-hour Ozone Maintenance Plan, and the 2004 8-hour Ozone Action Plan all rely on a Colorado Department of Aviation's aviation activity forecast that was prepared in 1999. From the forecasted activity levels, emissions were calculated and properly collaborated with the Colorado Department of Public Health and Environment for inclusion in the budgets listed in DMA's SIP maintenance plans.

Figure 1 provides the historical aircraft activity and future levels used to predict SIP emissions for future milestone maintenance years. Note that the future aircraft activity levels for DEN are extrapolated based on historical levels plus the addition of Southwest's proposed activity. The resulting aircraft activity levels are extrapolated forward to illustrate how the influence of the Proposed Action compares to the future aircraft activity represented in the SIP maintenance plans.

The addition of Southwest's increased aircraft activity levels directly affects the air carrier category at DEN. To better illustrate the influence Southwest will have on this category as it was represented in the SIP maintenance plans, Figure 2 isolates the air carrier category. The additional operations have been added to the actual trend line and compared to the future air carrier activity levels for future milestone years to demonstrate that the expected levels of operations are still below the air carrier aircraft activity levels represented in the SIP maintenance plans.

The FAA demonstrates that the total of the actual aircraft operations plus the proposed aircraft operations and associated emissions for Southwest is below the SIP's forecasted values, and therefore emissions attributed to flights by Southwest are already accounted for in the SIP emissions inventories. The FAA believes, and State representatives confirmed, that the total net emissions associated with the Proposed Action (including the aircraft emissions) are reasonably accounted for in the SIP maintenance plans. As a result, the Proposed Action demonstrates a conformance to the existing and updated SIP maintenance plans for the DMA.

References

40 CFR part 93 subpart B—Determining Conformity of General Federal Actions to State or Federal Implementation Plans.

EPA and FAA, General Conformity Guidance for Airports Questions and Answers, September 25, 2002.

Carbon Monoxide References

Colorado Department of Public Health & Environment, Air Pollution Control Division, Technical Support Document: Carbon Monoxide Redesignation Request and Maintenance Plan for the Denver Metropolitan Area, January 4, 2000.

Colorado Department of Public Health & Environment, Air Pollution Control Division, Carbon Monoxide Redesignation Request and Maintenance Plan for the Denver Metropolitan Area, January 10, 2000.

Colorado Department of Public Health & Environment, Air Pollution Control Division, Technical Support Document: Carbon Monoxide Maintenance Plan Revision for the Denver-Boulder Attainment Area, June 2003.

Colorado Department of Public Health & Environment, Air Pollution Control Division, Carbon Monoxide Maintenance Plan for the Denver Metropolitan Area, June 19, 2003.

Colorado Department of Public Health & Environment, Air Pollution Control Division, Technical Support Document: Carbon Monoxide Maintenance Plan Revision for the Denver-Boulder Attainment Area, September 2005.

Colorado Department of Public Health & Environment, Air Pollution Control Division, Carbon Monoxide Maintenance Plan for the Denver Metropolitan Area, December 15, 2005.

PM₁₀ References

Colorado Department of Public Health & Environment, Air Pollution Control Division, Technical Support Document: Colorado State Implementation Plan for PM₁₀, Denver Metropolitan Nonattainment Area, Emissions Inventories and Dispersion Model Results for the Maintenance Plan, Adopted April 19, 2001.

Colorado Department of Public Health & Environment, Air Pollution Control Division, PM₁₀ Redesignation Request and Maintenance Plan for the Denver Metropolitan Area, Adopted April 19, 2001.

Colorado Department of Public Health & Environment, Air Pollution Control Division, Revised Technical Support Document: Colorado State Implementation Plan for PM₁₀, Denver Metropolitan Nonattainment Area, Emissions Inventories and Dispersion Model Results for the Maintenance Plan, September, 2005.

Colorado Department of Public Health & Environment, Air Pollution Control Division, PM₁₀ Maintenance Plan for the Denver Metropolitan Area, Approved by the Colorado Air Quality Control Commission December 15, 2005.

Ozone References

Colorado Department of Public Health & Environment, Air Pollution Control Division, Technical Support Document: Colorado State Implementation Plan for Ozone, Denver Metropolitan Nonattainment Area, Emissions Inventories for the Maintenance Plan and Redesignation Request, Adopted January 11, 2001.

Colorado Department of Public Health & Environment, Air Pollution Control Division, Ozone Redesignation Request and Maintenance Plan for the Denver Metropolitan Area, Adopted January 11, 2001.

Colorado Department of Public Health & Environment, Air Pollution Control Division, Technical Support Document: Colorado State Implementation Plan for Ozone, Denver Metropolitan Nonattainment Area, Appendix C—Emissions Inventories for the Ozone State Implementation Plan, February 26, 2004.

Federal Register, USEPA approval of DMA's Ozone Action Plan, May 17, 2005.

Issued in Washington, DC, on April 20, 2006.

John M. Allen,

Deputy Director, Flight Standards Service.

Footnotes

1.  For clarification, the phrase “one round trip” is synonymous with a landing/takeoff cycle (LTO). The LTO consists of an aircraft taxiing from the terminal gate area to the runway, taking off by accelerating down the runway until 1,000 feet off the ground, climbing to the altitude of the local mixing height, returning on approach by descending from the mixing height to the runway, and finally completing the cycle by taxiing from the runway to the gate. An aircraft operation is defined as either a landing or a takeoff. Therefore, one LTO cycle is equal to two aircraft operations.

2.  Ozone is formed in the atmosphere rather than being directly emitted from sources. Ozone forms as a result of volatile organic compounds (VOCs) and oxides of nitrogen (NO_X) reacting in the presence of sunlight in the atmosphere. VOCs and NO_X are termed “ozone precursors” and their emissions are regulated in order to control the creation of ozone. Aircraft engine emissions data is in the form of “total hydrocarbons” or HC. For the purposes of this analysis, HCs are conservatively assumed equivalent to VOCs.

3.  For the purposes of this analysis, FAA has taken the conservative approach of considering the No Action scenario to include no Southwest operations at DEN. Although Southwest began initial operations at DEN in January of 2005, Southwest agreed to limit operations to levels determined to be de minimis to accommodate the preparation of a General Conformity Determination of up to 60 LTO's per day.

4.  Although not required because emissions are above de minimis, Table 4 provides the estimated emission contributions from the Proposed Action in comparison to the regional budget levels from the various SIP documents, both existing and future plans. The common assumption in these values is that the annual tons of emissions estimated from the Proposed Action are evenly distributed across 365 days of the year. The FAA is aware that contribution of emissions from the proposed Southwest activity will vary by day, week, month, and season. However, the overall daily emission contributions from the Proposed Action is so low relative to regional inventories that further estimates of daily emission contributions from the Proposed Action will not change the determination. Therefore, the emissions from the Proposed Action are not regionally significant.