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Pacific Aviation Consulting Inc.

PO Box 32, Port Hadlock

Washington 98339-0032

February 16, 2001

 

U.S. Army Corps of Engineers
Regulatory Branch
PO Box 3755
Seattle, WA 98124

Attn:  Jonathan Freedman, Project Manager

 Washington State Department of Ecology
Shorelands & Environmental Assistance Program
3190 – 160th Ave. S.E.
Bellevue, WA  98008-5452

Attn:  Ann Kenny, Environmental Specialist

 

Re:   Port of Seattle, Ref. No. 1996-4-02325

 

Dear Mr. Freedman and Ms. Kenny,

 This letter comprises comments regarding water resource elements of the Port of Seattle’s application for a Section 401 certification and Section 404 permit for the proposed Third Runway Project and associated construction.  These comments are submitted on behalf of Airport Communities Coalition, composed of the Cities of Burien, Des Moines, Federal Way, Normandy Park, Tukwila, and the Highline School District.

It is my expert opinion that a third air carrier runway at Sea-Tac is not the best solution to the Puget Sound region’s airport capacity needs, and in fact is harmful to the development of a good long-term solution.  Further, it is my opinion that there are obvious alternative runway configurations that would avoid or reduce the filling of wetlands needed for the Port’s proposed third runway.  These opinions derive from the following facts:

The existing Sea-Tac airport can continue to accommodate regional demand while the best long-term alternatives are being identified.  Needless filling of wetland and use of scarce national and local resources for the proposed third runway will harm the environment and the region and hurt the development of a good aviation system to serve the longer-term interests of the state and region.

My detailed comments are attached to this letter.

Sincerely,

Dr. Stephen Hockaday


Re:   Port of Seattle, Ref. No. 1996-4-02325,

Comments on Alternatives that Require Less Wetland and the Overall Public Interest

1.  Introduction

The revised application by the Port of Seattle to the US Army Corps of Engineers for a permit in accordance with Section 404 of the Clean Water Act contains revised wetland boundaries.  These boundaries include 50 wetland areas totalling approximately 18.37 acres.  14.23 acres in these 50 wetlands are proposed to be filled to construct an 8,500 feet long parallel third runway and associated works.

When considering whether or not to grant this permit, the US Army Corps of Engineers must consider whether there are other alternatives that meet most or all of the aviation need and which require filling of less wetland than the proposed alternative, or which require no filling of wetland.  The US Army Corps of Engineers must also consider whether or not the proposed activity is in the overall public interest.

If an alternative exists that meets most or all of the aviation need and which require filling of less wetland than the proposed alternative, and/or if the proposed activity is not in the overall public interest, the US Army Corps of Engineers may not grant the permit.

Examples of the wetland areas disclosed by the Port of Seattle in its latest permit application include:

Wetland

Area     Status         Remarks

A5-A8  Additional  Approximately 1,200 to1,600 ft south of the north threshold of proposed 8500 ft runway

W1,W2 Additional  Approximately 2,000 ft south of the north threshold on C/L of proposed 8500 ft runway

14          Original      Located in third Runway Safety Area (RSA)

35 a-d    Expanded   Grew from 0.18a impact area to 0.67a

35 e-f    Expanded   Grew from 1.68a  to 4.09a impact area (approx 2,500 ft from north threshold).

This report demonstrates that (1) there are alternatives which meet most or all of the aviation need and that require filling of less (or no) wetland than the proposed alternative, and (2) that the proposed activity is not in the overall public interest.  Therefore, the US Army Corps of Engineers should not grant the permit.

I base this report on review of the relevant application documents and my 30 years of experience in the aviation industry.  A full description of my qualifications and experience is given in my curriculum vita, attached.

2.  Alternatives Requiring Less Taking of Wetland

Alternatives that consist of a third runway that is different from that proposed by the Port of Seattle are feasible and require less taking of wetland.  These alternative third runways fall into two major classes: a length of less than 8,500 feet, and a lower elevation at the north end.  A third runway that has a combination of these classes is also feasible.

2.a.  Alternatives that include a third runway with a length of less than 8,500 feet

Several alternative lengths are available in the range from 6,000 to 7,500 feet.  Each of these alternatives are feasible and would require less taking of wetland than the proposed alternative.  Each alternative would have its southern threshold in the vicinity of Station 123+50, the southern threshold of the 8,500-foot runway proposed by the Port, and the north end would move south by 1,000 to 2,500 feet, thereby eliminating the need for some earthworks and reducing significantly the amount of wetlands taken.

As noted in the December 27, 2000 “Public Notice of Application for Permit”, the prime purpose of the project is “A third runway would allow Sea-Tac to operate two runways for landing during times of poor weather”.  As noted in the FEIS (page I-15), “arrival delay represents over 85 percent of total current delay experienced by an average flight.” A runway that provides sufficient length to allow Sea-Tac to operate two runways for landing during times of poor weather would therefore meet the defined purpose.

Runway landing length analysis was performed by the Port of Seattle as part of the preparation of the Master Plan Update.  The length requirements were established for landing weights that are 90 percent of maximum landing weight.  The runway length values are conservative, because landing aircraft typically have a decreased load of fuel and have landing weights that are significantly less than 90 percent of maximum landing weight.

Table 1 shows the percent of aircraft that can land on a third runway, based on Port of Seattle data and the conservative 90% of maximum landing weight assumption.

TABLE 1

Percent of Total Landing Operations Accommodated by 6000' and 6,700’ Runways

                                                            6,000’ Runway                                    6,700’ Runway

Aircraft            % in                  % Use                 % Use                          % Use               % Use

 Type                Mix                  Dry Rwy          Wet Rwy                      Dry Rwy           Wet Rwy

Commuter &

Smaller Air

Carrier (up

to C-III)            73%                      100%             100%                         100%                  100%

Larger

Air Carrier

(C-IV +)           20%                       43%                  0%                        100%                    96%

Cargo                 5%                       36%                25%                         100%                    86%

GA / Mil             2%                       70%                48%                         100%                  100%

All                    100.0%                   85%              76%                          100%                   98%

Sources:  P&D Aviation, Working Paper 1, Unconstrained Aviation Forecast Update (revised Jan. 2, 1997); P&D Aviation, Airport Master Plan Update for Seattle-Tacoma International Airport, Technical Report No. 6: Airside Options Evaluation (Sept. 19, 1994).

Note: C-III aircraft include F-28, ATR72, RJ70, B737, F100, B727, MD80/90 A319/320

         C-IV aircraft include  B757, 767, A310/321, A300, L101, DC10, B747/777, MD11/12, A330/340

Table 1 shows that even with the Port’s conservative assumptions, all aircraft other than some of the largest class of aircraft using the airport (C-IV) can land on a runway that is 6,000 feet or 6,700 feet in length.  The percent of all aircraft in the mix of traffic using the airport that could land on a third runway varies from 76% able to land on a 6,000 feet long wet runway, to as much as 100% that can land on a 6,700 feet long dry runway (according to Port of Seattle data).  As another runway (16L-34R) would be used by at least 50% of the landings in poor weather, a reduced runway length from 8,500 feet to 6,000 feet or 6,700 feet would not in any way reduce the capacity of the airport to operate two runways for landing during times of poor weather.  (Note that aircrew have discretion to choose a landing runway and that some wide-body aircraft may wish to land on a longer runway, such as Runway 34R, regardless of whether the third runway is 6,000 or 8,500 feet long.)

Table 2 shows the percent of aircraft that can also take off from a third runway, based on Port of Seattle data.

TABLE 2

Aircraft that could use a new runway of different lengths in 2010

Numbers and percentages of annual aircraft operations

Operation Type    2010 Forecast              6,000' Runway              6,700' Runway          8,500' Runway

Landing                        237,000             179,200-201,200           233,700-237,000      234,600

                                    (100%)             (76-85%)                      (99-100%)                    (99%)

Take Off                      237,000             78,200                         206,200                       213,300

                                    (100%)             (33%)                           (87%)                           (90%)

Total                             474,000         257,400-279,400       439,900-443,200            447,900

                             (100%)          (54-58%)                   (93-94%)                  (94%)

Sources:  Supplemental EIS, Table 1-2; Original EIS, Table II-3 and Page II-12; P&D Aviation, Working Paper 1, Unconstrained Aviation Forecast Update (revised Jan. 2, 1997); P&D Aviation, Airport Master Plan Update for Seattle-Tacoma International Airport, Technical Report No. 6: Airside Options Evaluation (Sept. 19, 1994), Tables 2-3 and 2-9, Figure 2-1, and Pages 2-6 and 2-18.

Table 2 shows that 87% of all aircraft using the airport can take off from a runway that is 6,700 feet in length.  This 87% is only 3% less than the 90% of all aircraft that can take off from an 8,500 feet long runway.  As another longer runway (16R-34L) is available for departures, it would be used by most departures in any event.  Therefore, a reduced runway length from 8,500 feet to 6,000 feet or 6,700 feet would not in any way reduce the capacity of the airport for departing aircraft.

Increasing the length of a new runway from 6,000 or 6,700 feet to 8,500 feet would provide only a minimal increase in the percentage of aircraft that could use a third runway and still would not permit its use by all aircraft. Any small benefit to be derived from an additional 1,000 feet to 2,500 feet of runway length would be far outweighed by the large increase in construction cost and the loss of wetlands.

2.b.  Alternatives that include a third runway with a lower elevation at the north end

Alternatives that include a third runway with a lower elevation at the north end are feasible and require less taking of wetland than the proposed runway. 

The threshold of Runway 34L has an elevation of 359 feet.  The threshold of Runway 16R has an elevation of   426 feet.  The proposed 8500' runway has threshold heights of 351 feet for Runway 34[west] and 411 feet for Runway 16[west].  It is clear that these are not the preferred runway threshold elevations.  Reducing threshold elevation below the proposed values decreases the amount of fill required to construct any runway alternative, and thereby reduces the taking of wetlands.  At 2500' spacing from 16L-34R, the existing ground level is at approximately 320 feet at the north end and 360 feet at the south end of the alignment of the proposed runway. 

Design considerations for reductions in elevation of the proposed runway include runway longitudinal gradient, connecting taxiway longitudinal gradient, ASDE visibility, FAR Part 77 approach surface clearances, and visibility from the control tower.  Alternative runway elevations are available that meet all of these requirements and cause less environmental harm.

Preferred runway elevations would permit a runway to be constructed within runway longitudinal gradient tolerances that is connected by taxiways to the rest of the airfield system and that permits Category 3 approaches.  Subject to this requirement, reductions in elevation, particularly those from the midpoint of the proposed runway to the north threshold of the runway can yield substantial reductions in wetland taking and construction cost by reducing fill and borrow requirements.

Preferred elevations are a function of runway length and location of the south threshold.  Additional study would be required to determine the optimal threshold elevation.   (Selection by the Port of a constant location for the north threshold of the runway in the EIS process maximized construction costs and environmental impacts of runway alternatives other than the maximum 8500' length.  Use of a constant location for the south threshold would provide a more objective evaluation of the cost and impact of alternative runway lengths that are less than 8,500 feet, down to 6,000 feet.)

Examples of alternative north runway threshold elevations for a third runway that would require less taking of wetlands are 340 feet for a 6,000 feet long runway and 320 feet for an 8,500 feet long runway.

 

3.  Alternatives Requiring No Taking of Wetland

There are several alternatives that eliminate the need for a third runway are feasible and require no taking of wetland.  The alternatives include use of existing regional airports, use of a new regional supplemental airport , moving commuter and regional aircraft operations to Boeing Field, and the application of advanced technologies.

 

3.a.  Use of existing regional airports

Several existing regional airports have excess runway capacity available to accommodate aircraft operations. 

The Puget Sound Regional Council (PSRC) Airport System Component of the 2001 Metropolitan Transportation Plan  (Draft 10/19/2000) shows these regional airports on Exhibit 4-23.  According to this Plan (Page 5-67), in addition to Sea-Tac, there are five smaller airports with commercial passenger service (including Boeing Field which has scheduled passenger service).

The runway length at Boeing Field is approximately 10,000 feet.  Other long runways at airports in the region include Paine Field (approximately 9,000 feet), and McChord AFB (approximately 10,000 feet).  Gray Army Airfield at Fort Lewis and Bremerton National Airport each have runways with a length of length 6,000 feet or more (Plan page 4-15).

The PSRC Airport System Component of the 2001 Metropolitan Transportation Plan  (Draft 10/19/2000) shows passenger forecasts on Page 5-68, and aircraft operations forecasts and capacity estimates on Exhibits 6-1 and 6-3 (after page 6-20).  These exhibits show that the airfield capacity of Sea-Tac today is 460,000 aircraft operations. 

The demand at Sea-Tac in 1998 was 408,000, and this is expected to grow to 474,000 in 2010 and 503,000 by 2015.  First, these data show that demand is less than capacity at Sea-Tac today.  Secondly, the data show that demand will exceed capacity by only 3% in 2010 and 9% in 2015 - - and only if it is assumed that all forecast passenger growth occurs at Sea-Tac, rather then being redistributed to other regional airports.

The same data for Snohomish Co. Paine Field show that airfield capacity is 288,000 aircraft operations.  In 1998, demand was 193,000 operations, increasing to 229,000 operations by 2015.  Therefore there is expected to be 59,000 excess capacity at Paine Field in 2015. 

In summary, in the future when demand may exceed capacity at Sea-Tac, excess capacity is available and additional demand may be accommodated at Paine Field, Boeing Field, and/or other regional airports; and a third runway at Sea-Tac, with its concomitant requirement for wetlands, is not needed.

3.b.  Use of a new Regional Supplemental Airport 

Construction of a new regional supplemental airport is another feasible means for providing airport capacity to meet future regional demand. 

The PSRC conducted an assessment of alternative potential sites for a new large regional supplemental airport in the early 1990s.  Twelve technically feasible alternatives were identified for a large airport with two 12,000 feet long parallel runways, separated by more than one mile.  None of the twelve alternatives gained political acceptance, due in part to the excessive scale and size of the proposed new airport.

Several of the twelve technically feasible alternative sites provide more than adequate space for a new small single runway regional supplemental airport with significantly less cost and less wetland impact than would occur either with the large size new airport examined by PSRC, or the third Sea-Tac runway proposed by the Port of Seattle.

A full assessment of these new small regional supplemental airport alternatives has yet to take place.  However it is clear that several of these alternative sites offer the opportunity to provide additional airport capacity, and would obviate the need for a third runway at Sea-Tac, with its wetland impacts.

3.c.  Full Use of Boeing Field

The south end of the main runway at Boeing Field is approximately four miles from Sea-Tac.  This distance is less than the distance between some of the runway thresholds at the Denver International Airport.  Boeing Field could be regarded operationally as part of Sea-Tac, and an opportunity exists for some Sea-Tac aircraft operations to move to Boeing Field, with an efficient passenger connection being established between the two airports. 

Sound Transit, the agency in charge of developing the Seattle region’s light rail system has developed plans, prepared an environmental impact statement, and executed a full funding grant agreement for the central link light rail system.  This light rail system will provide service between Seattle and Sea-Tac airport with several intermediate stops including the Boeing Access Road station that is at the south end of Boeing Field.  The link is scheduled to be open in 2009.

Excess aircraft operations capacity exists at Boeing Field today and will exist in 2015.  If additional capacity is required, the regional aviation system management actions proposed by PSRC in the Metropolitan Transportation Plan (page 7-7) could be implemented to divert general aviation aircraft to reliever airports and make additional room for Sea-Tac general aviation, commuter, regional jet, or other aircraft operations at Boeing Field.

The Boeing Field runway is in place, the rail link will soon be constructed, and the opportunity exists to take strategic management actions to make full use of existing facilities and avoid the need for a new runway at Sea-Tac, thereby avoiding any taking of wetlands.

3.d.  Application of Technological Solutions

A variety of technological solutions are available now or in the near future that can avert the need for construction of a third runway and its associated taking of wetlands.

Localizer Directional Aid ("LDA") approaches have already operated at Sea-Tac with conservative minimum cloud ceiling and visibility requirements.  Use of an LDA approach in conjunction with an ILS approach on adjacent closely spaced runways allows an additional arrival stream in weather minimums lower than those required for visual approaches.  This procedure has been in use for several years at St. Louis Lambert Field and more recently at San Francisco International Airport.  St. Louis has experienced a capacity gain of about 18 arrivals per hour (1993 Aviation System Capacity Report).   At the St. Louis and San Francisco airports, the poor weather minima required for such approaches have been set as low as 1,200-foot ceiling and 4 miles or less visibility.

Similar reductions in minima at Sea-Tac for LDA approaches would reduce the effect of poor weather conditions on arrival capacity from 44 percent of the year to approximately 15 percent of the year, thereby assuring higher capacity values for 85% of the year.  In addition, the highest delays occur when demand is highest, i.e. during the day (10 am to 9 pm) and in the summer (May though August).  In these high demand periods, IFR conditions only occur 2.8 percent of the time. In these peak traffic periods LDA approaches would reduce the effect of poor weather conditions on arrival capacity to 2.8 percent of the time, thereby assuring higher capacity values for 97.2% of the peak period.

As a result, full implementation of LDA approaches would allow Sea-Tac to operate successfully without a third

Runway, and thereby avoid wetland taking.

Additional New Technologies offer additional runway capacity benefits; including the use of Global Positioning System (GPS), Precision Radar Monitoring (PRM), Traffic Alert and Collision Avoidance System (TCAS) and Flight Management System (FMS) equipment and procedures to facilitate multiple approaches in poor weather conditions.  The FAA Office of System Capacity and Requirements ( in several publications, including the Aviation System Capacity Annual Report, Aviation Capacity Enhancement Plan, and Capacity Initiatives,) has identified Flight Management System, Global Positioning System, Precision Runway Monitor, and Traffic Alert and Collision Avoidance System technologies that are expected to permit increased arrival capacity for parallel runways by the year 2005:

FMS-flight path navigation procedures are expected to allow a reduction in weather minimums and offer alternative arrival paths for FMS-equipped aircraft. A conservative perspective on the results which could be achieved from the technologies listed above is that dual approaches could be made to Runways 16L and 16R, or 34L and 34R in some IFR conditions in the relatively near future. For example, FAA has already approved GPS non-precision approach to ¾ mile visibility (PSRC MTP, page 7-13). The resulting capacity increase could eliminate the need for a third runway and associated wetland taking.

3.e.  Application of Demand Management

The opportunity exists to take advantage of demand management, which is a naturally occurring phenomenon as airports become more congested.  Airlines and other aircraft operators make sound business decisions to reschedule flights outside of the peak periods, to use larger aircraft and thereby reduce the number of aircraft operations, and/or to use other regional airports with less congestion.  In addition, passengers may select alternative modes of transportation for shorter trips if travel times become competitive, either as a result of the decreased reliability of air travel, or by improvement of other modes.

In the DSEIS for the third runway, the FAA and the Port concluded that these types of  demand management actions would occur naturally in response to changes in the level of service and would enable the Airport to accommodate all of the passenger demand without the construction of an additional runway (DSEIS, page 2-7).  The FAA analyzed the impact of demand management (Seattle-Tacoma International Airport Capacity Enhancement Plan Update Data Package 11, page 46-48), and demonstrated that a reduction in peak traffic of 3 percent would save approximately 23 percent of delays to aircraft. 

The naturally occurring phenomenon of demand management will ensure that congestion never reaches the high levels predicted by the Port, and thereby assure that no third runway and its associated wetland taking is required.

4.  Comments on the Overall Public Interest of the Activity

4.a. Multiple commercial airport solutions that are in the public interest would be foreclosed

Multiple regional commercial airport solutions that are in the public interest would be foreclosed if the Port of Seattle proposed runway and associated airport development were constructed.  Regional financing capability for airport improvements would be significantly degraded by the approximately $2 billion investment that the Port plans to make on the third runway and other Sea-Tac construction.  The financing that would be committed to the third runway and other Sea-Tac improvements is likely to foreclose public tolerance and ability to pay for the expenditures needed to develop a truly regional airport system.

Ground access trips to Sea-Tac originate across the region and must traverse the congested freeway system adjacent to Sea-Tac to get to the airport.  A multiple airport system (like those existing in many other large communities such as Dallas or Houston) would reduce overall airport ground access travel , and thereby save passenger time, highway congestion, and regional air pollution.

Many studies confirm that airline ticket and airport parking prices are lower in communities where there is a choice of airports. (This lower ticket price phenomenon is well known, as demonstrated in the March 2001 AARP Modern Maturity magazine, which states:  “I have learned that the secret of scoring the cheap seats is to ask the right questions…..Is there an alternate airport nearby?  If you’re flying to Washington D.C., for example, consider landing in Baltimore, just 30 miles away.  Going to San Francisco? Check Oakland and San Jose.  Always ask about another airport nearby.  There could be a big difference in price.”)

The public is best served by the availability of alternatives and competition for services.  Concentration of  all commercial aviation activity in one location with one provider, precludes this competition and is not in the public interest, particularly when there are many other alternatives available with lower cost and less adverse environmental impact.

4.b. The capability of existing aviation facilities is being compromised by the proposed third runway

As noted in the PSRC Airport System Component of the 2001 Metropolitan Transportation Plan  (Draft 10/19/2000), the operation of Boeing Field is limited today by airspace interactions with Sea-Tac (Page 7-5).

Adding an additional runway at Sea-Tac, pointed directly at Boeing Field only 4 miles away, is bound to exacerbate this interaction. These airspace interactions were highlighted in an FAA sponsored report (Aviation Simulations Int'l, Inc., Impact of Boeing Field Interactions on the Benefits of a Proposed New Runway at Seattle-Tacoma International Airport (July 1992).

In essence, the airspace interactions between Boeing Field and Sea-Tac mean that any gains in capacity at Sea-Tac are obtained at the cost of a similar reduction in capacity at Boeing Field.  It is not in the public interest to build a third runway at Sea-Tac and cause environmental harm, while concurrently compromising the value of an existing public asset at Boeing Field that could be part of a better regional solution.

4.c.  Aircraft taxiing operational safety may be compromised with the Port of Seattle proposed runway

Aircraft taxiing operational safety may be compromised with the Port of Seattle proposed runway, and this is not in the public interest.  Currently, approximately 40% to 50% of aircraft using Sea-Tac must taxi across an active runway between the runway and the terminal building.

Aircraft crossing active runways without permission or as a result of a controller error are referred to as runway incursions.  Runway incursions are a serious safety hazard that is being addressed as an urgent matter by FAA.  A runway incursion, that caused a near-collision, occurred at Sea-Tac on January 21, 2001; as reported by King 5 television news (See Exhibit 1).

A third runway would increase the risk of runway incursions for aircraft using Sea-Tac, as any aircraft taxiing to and from the new runway would have to cross two active runways - - Runways 16L-34R and 16R-34L.  Depending on the use of the new runway, the number of aircraft crossing active runways could increase by 50% to 100%.  The runway incursion rate and collision risk would increase by at least this percentage as the new taxiway system is more complex, and there would be more scope for disorientation and/or errors by pilots and controllers.

A similar runway layout existed at Atlanta Hartsfield International Airport, where aircraft from a third runway had to cross two other runways to get to the terminal building. Eventually the terminal building was moved to a position between the parallel runways, in part to overcome this serious efficiency and safety flaw.

Constructing a third runway and increasing the risk of runway incursions and aircraft collisions by a factor of up to two times existing rates is not in the public interest, particularly when there are many other alternatives available with lower cost and less adverse environmental impact.


EXHIBIT 1

Near-Collision at Sea-Tac on January 21, 2001

(Source: King 5 Television News at  http://www.king5.com/detailtopstory.html?StoryID=12571)

Close call on Sea-Tac runway leaves passengers shaken                                                 January 22, 2001, 05:30 PM

 

SEA-TAC INTERNATIONAL AIRPORT - Two planes loaded with passengers came within “yards” of each other on a Sea-Tac runway early Monday morning, according to one eyewitness.

 REPORTED BY  Glenn Farley

 

 RESOURCES

 •  Sea-Tac Airport 

 •  Federal Aviation Administration 

 •  Video: Linda Byron reports on the rise in the number of runway incursions. 

 

At 12:45 a.m., Microsoft employee Keith Wintraub was aboard an American Airlines MD-80 when a nearly identical TWA MD-80 took off, right overhead.

“It was like the plane was taking off just above you,” he told KING 5 News. “I quickly turned my head and looked out the window, and it was clear this plane had just missed us. And as I looked up, there was the tail of the plane.”

The American jet was landing to the south and landed on Runway 16 Right. It came down most of the field, and then turned left on the Taxiway November. As he crossed Runway 16 Left, he was overflown by the TWA jet.

Control tower radar confirms the TWA jet passed over the American jet, but it's not clear exactly how close they were.

It was dark, and visibility was officially about one quarter mile with patchy fog. Wintraub says it was quite foggy.

“It was clear, first of all, that there was no margin for error,” he said. “I mean, if this plane for some reason had needed more space to take off, or had to abort its takeoff, we were right in a place to be T-Boned by this plane.”

TWA Flight 24 was taking off for St. Louis at about 12:45 a.m. Monday with 103 passengers and five crew members aboard.

The American plane, Flight 1991, had just arrived from Dallas with 63 passengers and five crew members.

A spokesman for American Airlines said they have been told by the FAA that their plane was cleared to taxi across the runway, and that TWA was cleared to take off.

It will now be up to an investigation to determine if the incident was caused by pilot error, controller error, or something else.


4.d.  Aircraft safety may be compromised by walls near the proposed third runway

Aircraft safety on the runway may be compromised by the proposed third runway; due to the high walls and embankment surrounding the new runway.

There would be a near vertical drop of approximately 170 feet on the west side of the proposed new runway, that would start less than 100 feet from the edge of the Runway Safety Area (RSA). 

Exhibit 2 (extracted from Exhibit C-115 of Stormwater Management Plan Appendix Q Dec 2000 Parametrix Inc.) shows the wall with a large aircraft added, located at the western edge of the RSA.  According to FAA (Appendix 8 of FAA Advisory Circular 150/5300-13 Change 6, Airport Design), the RSA enhances the safety of airplanes which undershoot, overrun, or veer off the runway, and it provides greater accessibility during such incidents.  An aircraft would be in the location shown on Exhibit 2 if it veered off the runway during an emergency but remained within the RSA (as envisioned by the FAA provision of a 500 feet wide Runway Safety Area).  Such an aircraft would only have to be off course by an additional 100 feet to the west to fall off the embankment and drop 170 feet into Miller Creek.

There is an additional near-vertical wall proposed to be constructed to the immediate north of the north threshold of the proposed third runway.  This wall is approximately 75 feet high, and results in a 75 foot drop from the end of the extended runway safety area to Miller Creek. Aircraft over-running the RSA during landings to the North would fall 75 feet into Miller Creek and/or Lora Lake.  Aircraft landing to the South that are more than 60 feet below the glide slope would crash into this near vertical wall.

In addition to these direct physical safety issues, there is also a concern about wind shear.  Aircraft wind-related operational safety may also be compromised by the proposed third runway.  There is the possibility that downdraft or updraft wind shear may be created or magnified by these 75 feet and 170 feet high walls adjacent to the proposed third runway, that may further compromise aircraft safety during landing or take off from the third runway. In the absence of a full assessment of these concerns, there is a concern that public safety may be at risk from these walls.

As a result, the reliance on walls as high as 170 feet to support the third runway is not in the public interest because they may compromise aircraft safety.

(Diagram prepared for the world wide web from Hockaday diagram on paper)

4.e.  Aircraft airspace operational efficiency or safety may be compromised

Aircraft airspace operational efficiency or safety may be compromised by the proposed third runway. Potential conflicts between aircraft using Boeing Field (BFI) and those using Sea-Tac would eliminate most of the potential value of a third runway.  Aircraft using a third runway at Sea-Tac in poor weather conditions would conflict with aircraft using Boeing Field, thereby reducing the usefulness of the additional runway at Sea-Tac. 

According to an FAA sponsored report (Aviation Simulations Int’l, Inc.,“Impact of Boeing Field Interactions”, Prepared for the FAA Northwest Mountain Region, July 1992), airspace interactions would occur in three situations:

·         North Flow Instrument Meteorological Conditions (Sea-Tac would not accommodate 2015 traffic even with a new runway);

·         South Flow Instrument Meteorological Conditions (Sea-Tac capacity gains from a new runway would be small and would reduce BFI Capacity); and

·         South Flow Visual Meteorological Conditions  (Sea-Tac capacity gains from a new runway are not assured).

The FAA report noted that, during Instrument Meteorological Conditions (IMC), horizontal separation must be maintained between Sea-Tac departures and BFI arrivals and between Sea-Tac departures and BFI departures.  Basically, no flights may go into or out of BFI while flights depart from Sea-Tac during IMC.  In the simulation, performed as part of the study, no Sea-Tac departures from any runway were allowed when a BFI arrival was within 4 nm of touchdown.  No BFI departure was allowed after a Sea-Tac departure until the Sea-Tac departure had passed BFI.

The new runway did not alleviate the impact of north flow interactions so this would become the limiting capacity.  At the highest, year 2015 demand level, the departure queue at Sea-Tac backed up, preventing all taxiing.  A single arrival to BFI stops the arrival flow onto the new runway for a significant period. For typical approach speeds (120 to 150 knots), the 10 nautical miles separation required between arrivals to the new runway is equivalent to 4 to 5 minutes, limiting the capacity of the new runway to 12 to 15 arrivals per hour when aircraft are using BFI.  There would be five hours each day with 10 or more arrivals per hour at BFI.  As a result, disruptions to the capacity of the new runway will be essentially continuous during these hours.

The FAA intends to use dependent instrument approaches to Runway 16L and the new runway.  Therefore, any disruption of the new runway arrival flow will also disrupt arrivals to Runway 16L, thereby also reducing its capacity.  Up to two aircraft could arrive on Runway 16L in each 10-mile gap between aircraft approaching the new runway.

Arrivals to Runway 16L are independent of BFI arrivals only when special procedures are in place. (P & D Aviation, Aviation Master Plan Update Technical Report No. 4, page 3-10.  In weather conditions which allow the BFI Air Traffic Control Tower (ATCT) to see the Sea-Tac arriving aircraft, visual separation is provided by the controllers and no loss in capacity is experienced.  This operating arrangement is known as Plan Alpha.  Cloud ceilings at BFI must be at least 2,500 feet for Boeing ATCT personnel to see Sea-Tac arrivals.  The yearly occurrence of south flow conditions with ceilings below 2,500 feet (no Plan Alpha) is approximately 17 percent.  However, the actual time of this impact on capacity is less because of special ATCT procedures.  Under these procedures, during certain weather conditions, and for pilots familiar with BFI, aircraft approaching Sea-Tac are advised to maintain 3,000 MSL until the BFI ATCT advises the FAA Terminal Radar Control facility (TRACON) that the landing of the other aircraft at BFI is assured.  At this point, the Sea-Tac approaching aircraft is given final approach clearance and authorization to land.  If the BFI approach pilot executes a missed approach, TRACON vectors the Sea-Tac approach back into the arrival stream and one arrival interval slot is lost in arrival capacity at Sea-Tac.  However, this situation occurs very rarely.  If the pilot's familiarity with BFI is unknown, the TRACON will leave an interval or empty slot in the Sea-Tac arrival stream in order to provide for a potential missed approach at BFI.  This situation results in the loss of one or two arrival intervals in the arrival capacity of Sea-Tac.  The frequency of this occurrence is dependent on arrival demand at the two airports and the percentage of low familiarity pilots in the arrival stream to BFI.  As demand increases, the frequency of occurrence will also increase.

BFI-Sea-Tac interactions also may occur in Visual Meteorological Conditions.  Presently, because of special procedures, the south flow arrival streams to the existing runways do not require a gap for BFI arrival because vertical separation exists between the normal approach streams, and controllers closely monitor the BFI arrivals for the first sign of a missed approach.  The proposed third Sea-Tac runway, however, is approximately 1,700 feet west of Sea-Tac Runway 16R so that arrivals to the third runway will cross the BFI arrival stream while the BFI flights are still airborne.  It has not as yet been determined whether the Plan Alpha procedures can be extended to permit the BFI arrivals to cross without a gap in the Sea-Tac Runway 17 arrival stream.

In a similar manner to the situation described for taxiing safety concerns, the addition of one more arrival or departure stream into the airspace increases the complexity of the airspace and increases the number of potential conflicts significantly.  These additional conflicts directly result in losses in efficiency and increases in controller workload, and may contribute to additional safety concerns in some situations.  As a result, the losses of efficiency and potential increases in risk are not in the public interest, especially when alternatives are available that cost less to construct, are more efficient, and have less environmental impact.

5.  Conclusions

A third air carrier runway at Sea-Tac is not the best solution to the Puget Sound region’s airport capacity needs, and is harmful to the development of a good long-term solution.  Obvious alternatives exist to the Port’s proposed third runway that would avoid or reduce the filling of wetlands; and other public interest concerns exist for the proposed third runway:

In addition, there are potential combinations of these alternatives that may yield even more benefit and have less adverse consequences than any individual alternative considered alone.  It is certainly true that alternatives exist which meet the aviation need and take less wetland or no wetland.  It is premature to approve any permit until there is complete assurance that the preferred alternative has been selected and that the public interest is being best served.