COMMISSION 
AGENDA MEMORANDUM                        Item No.          8g 
ACTION ITEM                            Date of Meeting       June 27, 2023 

DATE :     June 16, 2023 
TO:        Stephen P. Metruck, Executive Director 
FROM:    Keri Stephens, Director, Aviation Facilities and Capital Programs 
Eileen Francisco, Director Aviation Project Management 
SUBJECT:  S. 188th St. Tunnel Improvements (C801157) 
Amount of this request:              $29,600,000 
Total estimated project cost:         $34,500,000 
ACTION REQUESTED 
Request Commission authorization for the Executive Director to take all steps necessary as
identified in section 3.2.3 Resolution 3810 (Delegation of Authority) and include a Project Labor
Agreement to complete the S 188th  St. Tunnel Improvement project at Seattle-Tacoma
International  Airport  (SEA).  This  request  is  in  the  amount  of  $29,600,000  for  a  total
authorization of $34,500,000. 
EXECUTIVE SUMMARY 
The S 188th St. tunnel structure is located beneath Runway 34R and was originally constructed
in 1960. Based upon an existing easement the Port owns the S. 188th St. tunnel structure and
the City of SeaTac owns the S 188th St. roadway. This project has assessed the tunnel for
current code requirements. Based on the findings of that assessment, almost all the existing
systems are either deficient or non-functional. This project will address the structural condition,
lighting, and other systems to ensure the tunnel is brought back to a satisfactory level of
service. The budget increase is due to code required changes for ventilation. Additional ly, the
project will be utilizing management reserve for the budget increase, therefore, majority-ininterest
approval from the Airlines will not be required. 
JUSTIFICATION 
This project supports the Century Agenda strategic goal and objective to advance this region as
a leading tourism destination and business gateway by meeting the region’s air transportation
needs by delivering vital infrastructure in a sustainable and cost-effective manner. 
The life safety systems in the tunnel are original to its construction. These systems include
ventilation,  back-up  power,  and  fire  detection,  most  of  which  are  currently  missing  or

Template revised January 10, 2019.

             COMMISSION AGENDA – Action Item No. 8g                                   Page 2 of 5 
Meeting Date: June 27, 2023 
inoperable. Tunnel lighting, the sole exception, was partially replaced in the 1990s, however
many of the light fixtures have failed and replacement parts are no longer available. This
project will replace or restore these systems to reduce life safety risk, improve lighting, driver
and pedestrian safety and improve energy efficiency. 
Diversity in Contracting 
The project team has been working with the Diversity in Contracting Department and set 13%
aspirational goals for women and minority business enterprises (WMBE) participation in the
construction contract.  The design contract includes a 15% WMBE participation requirement
and is currently trending above the goal. 
DETAILS 
The tunnel is periodically inspected by Port of Seattle engineering in accordance with the
Washington State Department of Transportation’s Bridge and Tunnel inspections. The
inspection performed in 2018 daylighted concerns over the age and condition of multiple
tunnel systems. This and other elements initiated the process to first address the lighting
system. 
SEA later decided to expand the scope to further assess all the existing life safety systems. SEA
engaged a design consultant to assess the condition of the lighting and life safety systems. The
consultant produced a list of recommendations and those recommended for immediate action
formed the basis of the scope of work. 
Due to limits of the previous delegation of authority the condition assessment did not include a
Computation Fluid Dynamics (CFD) model of the tunnel. During design a CFD model was
performed, and it was discovered that the existing ventilation would need to be entirely
redesigned to meet today’s ventilation requirements.  The improvements will require the
closure of the existing tunnel vents which will impact airfield operations.  The project team is
conducting Safety Risk Management sessions with airfield operations, the FAA, and the airlines 
which will determine how best to manage the impacts.  This change, plus higher than
anticipated cost escalation, led to the increase in the project budget from $24,500,000 to
$34,500,000. 
Additional improvements for the tunnel such as  smoke control, fire suppression, egress
pathway improvements, airfield grading and drainage, hydrant stand pipes, seismic retrofitting,
and structural improvements to support additional airfield loading are planned under the
Sustainable Airport Master Plan Near term projects. 



Template revised June 27, 2019 (Diversity in Contracting).

             COMMISSION AGENDA – Action Item No. 8g                                   Page 3 of 5 
Meeting Date: June 27, 2023 
Scope of Work 
Scope of work for this project includes structural (crack sealing/spall repair), civil (signage),
electrical  (lighting,  power,  emergency  power),  mechanical  (ventilation,  fire  protection),
communication and special system (fire detection/alarm, carbon monoxide monitoring,
security, egress/traffic management) improvements. 
Schedule 
Construction start                                2023 Quarter 4 
In-use date                                       2024 Quarter 4 
Cost Breakdown                                     This Request           Total Project 
Design                                                  $3,050,000             $7,950,000 
Construction                                           $26,550,000            $26,550,000 
Total                                                        $29,600,000             $34,500,000 
ALTERNATIVES AND IMPLICATIONS CONSIDERED 
Alternative 1 – Defer scope to later projects or no action. 
Cost Implications: $2,710,000 
Pros: 
(1)   No additional costs incurred. 
Cons: 
(1)   Ignores critical life safety system deficiencies. 
(2)   Cost incurred to date would need to be expensed. 
This is not the recommended alternative. 
Alternative 2 – Replace existing lighting and backup power generation in the tunnel. 
Cost Implications: $8,200,000 
Pros: 
(1)   Addresses lighting deficiency. 
(2)   Lower capital investment by the Port. 
Cons: 
(1)   Ignores critical life safety system deficiencies. 
This is not the recommended alternative. 


Template revised June 27, 2019 (Diversity in Contracting).

             COMMISSION AGENDA – Action Item No. 8g                                   Page 4 of 5 
Meeting Date: June 27, 2023 
Alternative 3 – Bring lighting and life safety systems up to a satisfactory level of service. 
Cost Implications: $34,500,000 
Pros: 
(1)   Addresses critical life safety system deficiencies. 
(2)   Supports the 1960 easement agreement in that the Port would maintain the tunnel
and associated fire life safety systems. 
(3)   Improves lighting, air quality and general conditions inside the tunnel. 
(4)   Better protects the public, tunnel, and airfield from fire damage. 
Cons: 
(1)   Larger capital investment by the Port. 
(2)   Future projects may impact improvements. 
This is the recommended alternative. 
FINANCIAL IMPLICATIONS 
Cost Estimate/Authorization Summary              Capital        Expense           Total 
COST ESTIMATE 
Original estimate                                 $6,200,000               $0      $6,200,000 
Previous changes – net                         $24,500,000               $0     $24,500,000 
Current change                                 $9,975,000         $25,000    $10,000,000 
Revised estimate                               $34,475,000         $25,000     $34,500,000 
AUTHORIZATION 
Previous authorizations                          $4,900,000               $0      $4,900,000 
Current request for authorization               $29,575,000         $25,000     $29,600,000 
Total authorizations, including this request      $34,475,000         $25,000     $34,500,000 
Remaining amount to be authorized                    $0             $0             $0 
Annual Budget Status and Source of Funds 
This project (CIP #C801157) was included in the 2023-2027 capital budget and plan of finance
with a budget of $24,500,000. A budget increase of $9,975,000 was transferred from the
Aeronautical Allowance1 (CIP #C800753) resulting in zero net change to the Aviation capital
budget. The funding source will be the Airport Development Fund (ADF) and revenue bonds.
This project received Majority-in-Interest (MII) approval from the airlines in April 2021.  With
the budget increase, Port management elected to utilize the MII Management Reserve2 
1 The Aeronautical Allowance is included in the Capital Improvement Plan to ensure funding capacity for 
unspecified projects, cost increases for existing projects, new initiatives, and unforeseen needs. This ensures funding
capacity for unanticipated spending within the dollar amount of the Allowance CIP. 
2 The Signatory Lease and Operating Agreement (SLOA) requires airline’s approval for New Projects meeting the
Majority-In-Interest (MII) threshold. The Port may increase the budgets of New Projects up to an aggregate
additional $210,000 million dollars in Management Reserve without further MII review. 

Template revised June 27, 2019 (Diversity in Contracting).

             COMMISSION AGENDA – Action Item No. 8g                                   Page 5 of 5 
Meeting Date: June 27, 2023 
provision within the Signatory Lease Operating Agreement (SLOA) without requiring additional
MII approval from the airlines. 
Financial Analysis and Summary 
Project cost for analysis              $34,500,000 
Business Unit (BU)                  Airfield Movement Area 
Effect on business performance     NOI after depreciation will increase due to inclusion of
(NOI after depreciation)             capital (and operating) costs in airline rate base 
IRR/NPV (if relevant)                N/A 
CPE Impact                       $.11 in 2025 
Future Revenues and Expenses (Total cost of ownership) 
This project will have an impact on Aviation Maintenance annual operating and maintenance
(O&M) costs. Aviation Maintenance is looking to outsource the maintenance of all systems
being installed in the Tunnel. 
ATTACHMENTS TO THIS REQUEST 
(1)   Presentation Slides 
PREVIOUS COMMISSION ACTIONS OR BRIEFINGS 
April 27, 2021 – The Commission authorized design for $4,610,000. 
January 24, 2023 – The Commission authorized a design services contract amendment for
$1,200,000. 








Template revised June 27, 2019 (Diversity in Contracting).