PORT OF SEATTLE 
MEMORANDUM 
COMMISSION AGENDA               Item No.      7a 
STAFF BRIEFING 
Date of Meeting      April 1, 2014 
DATE:    March 14, 2014 
TO:     Tay Yoshitani, Chief Executive Officer 
FROM:    Michael Ehl, Director, Airport Operations 
Wayne Grotheer, Director, Aviation Project Management 
SUBJECT:  Airport Service Tunnel Renewal/Replacement 
SYNOPSIS 
The Airport Service Tunnel is located below the Airport arrivals drive, and runs the full
length of the main terminal. The tunnel supports the entire arrivals drive, critical portions
of the departure drive, houses a range of utilities essential to main terminal operation, and
provides access to the Central Loading Dock and Central Heating Plant. The loading
dock and heating plant reside in the middle of the tunnel, in the Central Area Structure,
which has already been seismically upgraded in 1997. The 2,500-foot-long tunnel was
designed, constructed, and commissioned in phases between 1968 and 1974. The Airport
Service Tunnel Renewal/Replacement project will bring the service tunnel structures up
to current seismic code and improve their earthquake safety. The work is part of an
ongoing program of seismic upgrades at the Airport that was accelerated to include the
Airport's roads and bridges following the Nisqually earthquake in 2001. Work would
include improvements to shear walls, improved column footings, beam reinforcement, 
and additional seismic bracing. Ongoing seismic upgrades at the Airport have included
upgrades to the main parking garage (1990), the central loading dock area (1997), main
terminal baggage and ticketing (1998 and 1999), Airport roads and bridges (2001), and
additional main terminal seismic retrofitting (2004).
Staff will return to request  Commission authorization to use design-build contract
delivery methodology and to develop preliminary design documents for this project on
April 22. This approach would allow staff to solicit and select a consultant team with
design-build contracting, structural design and geotechnical engineering experience to do
the preliminary design.  The consultant would identify and perform initial design on the 
seismic upgrades needed, and prepare the preliminary design specifications and planning
documents that will be used as the bridging documents to solicit, bid, and award a major
works design-build contract. 
BACKGROUND 
The service tunnel structure is complex, consisting of four different structural support
systems in seven different locations shown in Attachment A. One area, the Central Area
Structure, was upgraded in 1997 as part of the Ground Access and Seismic Improvements

Template revised May 30, 2013.

COMMISSION AGENDA 
Tay Yoshitani, Chief Executive Officer 
March 14, 2014 
Page 2 of 3 
project. The Service Tunnel Renewal/Replacement project will address the six remaining
portions of the service tunnel that have not been upgraded. 
In 2009, Kennedy/Jenks Consultants completed a condition assessment of the parking
garage and service tunnel to determine long-term major maintenance and seismic
reinforcement needs.  The condition assessment identified a number of seismic
vulnerabilities in every portion of the service tunnel, with the exception of the loading
dock area. 
CRITICAL NEED 
The service tunnel is an essential Airport facility and is structurally linked to other critical
Airport infrastructure.  For instance, the roof of the service tunnel forms the Airport's
arrivals drive, and supports portions of the departures drive. The tunnel provides critical
secured access to the Central Heating Plant and its supporting infrastructure, the central
loading dock for the terminal used by commercial delivery vehicles, and the employee
busing operation.  The tunnel is the structural support for multiple critical utilities,
offices, locker rooms, storage rooms, and emergency generators. The central loading
dock was previously upgraded seismically in 1997. A catastrophic failure during a
seismic event could significantly cripple Airport operations and those above and within
the tunnel. 
The service tunnel is one of the remaining major pieces of essential Airport infrastructure
that has not been strengthened or upgraded to current seismic building codes. The tunnel
was built by two contractors: the Main Terminal contractor and the North Airport
Expressway contractor. The Main Terminal contractor was responsible for construction
immediately in front of the terminal structure. The airport expressway contractor was
responsible for those portions of the tunnel extending beyond the terminal and interfacing
with the regional highway network.
The portions of the tunnel built by the terminal contractor were constructed to the seismic
building code standards of the time, but not to the more robust roadway seismic standard.
Seismic standards have changed greatly since the construction of the service tunnel, and
an update is needed.  Retrofitting the service tunnel will improve its survivability and
strength, while also extending the service life of the facility.
Without seismic upgrades, there are unreinforced portions of the service tunnel that will
be at risk of severe damage and/or localized failure during a seismic event. This in turn
could lead to localized failure of the departures drive.  The 2009 Kennedy/Jenks study
indicated that each section of the service tunnel had unique seismic deficiencies, with the
transition structures between the cast-in-place concrete sections and the sections
supported by structural framing being the areas of greatest risk. There are also failing
expansion and construction joints that are causing water-related deterioration and damage
to the tunnel. Unique design solutions will be required for different sections of the service
tunnel since the structural designs vary.

COMMISSION AGENDA 
Tay Yoshitani, Chief Executive Officer 
March 14, 2014 
Page 3 of 3 

Proposed improvements will include the strengthening of columns and their footings,
structural beam reinforcement, tying structural beams together, and adding shear walls
and panels. Other critical repairs within the tunnel include improving the drainage and
repairing failed structural and expansion joints that are allowing backfill material to move
through joints in the tunnel walls. 
DESIGN-BUILD PROJECT DELIVERY 
The service tunnel is a critical facility for Airport operations and must remain open with
limited disruptions 24 hours a day, 7 days a week. As a result, staff is recommending the
use of design-build contract delivery methodology.  The project would benefit from
designer-contractor collaboration to create opportunities for greater innovation,
efficiencies, unique design solutions, and highly specialized construction approaches to
improve constructability and phasing that are critical to minimizing operational impacts
during construction. Additionally, using a design-build approach allows the project to
design a segment, evaluate the efficacy of that design, and develop specific construction
techniques and staging strategies to construct that segment. This approach can then be
used to refine the design and construction methods of subsequent similar tunnel sections.
ATTACHMENTS TO THIS BRIEFING 
Attachment A  PowerPoint slides. 
PREVIOUS COMMISSION ACTIONS OR BRIEFINGS 
March 27, 2007  Parking Garage/Service Tunnel Pre-Design authorized.