COMMISSION 
AGENDA MEMORANDUM                        Item No.          8c 
ACTION ITEM                            Date of Meeting     November 10, 2020 
DATE:     October 19, 2020 
TO:        Stephen P. Metruck, Executive Director 
FROM:    Tina Soike, Engineering Director 
Janice Zahn, Assistant Engineering Director, Construction Services 
SUBJECT:  Concourse C New Power Center (CIP #C800724) Change Order Over $300,000 
ACTION REQUESTED 
Request Commission authorization for the Executive Director to execute a change order to
Contract MC-0319131 Concourse C New Power Center for relocation of the 400 Hz Power system 
conduits from Gate C 9 Passenger Loading Bridge (PLB), Seattle-Tacoma International Airport for
an estimated amount not-to-exceed $600,000.00. 
EXECUTIVE SUMMARY 
This change order request requires no additional budget (zero dollars) because it can be
accommodated within previously authorized budgets, and it requires no additional time (zero
days) because it can be accommodated within existing contract schedule parameters. Funding
for this work will be transferred from the PLB program (CIP#C800793) to Concourse C New Power
Center project (CIP #C800724).  Total authorized by Commission for the PLB CIP#C800793 is
$13,000,000.00.  Total  Authorized  for  Concourse  C  New  Power  Center  CIP#C800724  is
$10,500,000.00. Final costs are still under negotiations, but if the full not-to-exceed amount of
$600,000.00 were to be issued as a change order, this would represent 5.7% increase to the
Concourse C New Power Center budget and over 10% of the major construction contract value.
Commission action is required under the General Delegation of Authority because the value of
the change order is estimated to exceed $300,000 and potentially 10% of the contract value. 
This change order work to reroute existing 400Hz conduits is required to complete the PLB
replacement at Gate C9. The location of the existing and proposed new 400 Hz conduits are
within the same project footprint as the Concourse C power center project. To reduce the risk to
both projects with multiple contractors in the same location, executing this work by the
Concourse C New Power Center contractor is the recommended alternative. 

Description of Change Order 
This change order will remove and relocate four existing 400Hz conduits attached to the fixed 
walkway portion of the C9 PLB. These conduits will be removed from the C9 PLB and relocated

Template revised September 22, 2016.

COMMISSION AGENDA  8c                                              Page 2 of 5 
Meeting Date: November 10, 2020 
to new supports along the Concourse C building. Removing and relocating these 400Hz conduits
will allow replacement of the C9 PLB without shutting down the 400 Hz power for an extended
period of time to 8 other operating gates and significantly affecting airline operations. 
Background 
The proposed pathway of the relocated conduits shares the same working space as the
Concourse C Power New Center project currently under construction. The PLB project schedule 
overlaps with the Concourse C Power Center and both projects are in the same physical
workspace with significantly increase risks to both projects. To avoid multiple contractors
working in the same space and reduce or eliminate the risk of increased cost and time impacts
for both projects, the best alternative is to perform the work as a change order to the Concourse
C New Power Center project. 
The PLBs at Sea-Tac Airport have a high utilization in comparison to airports with comparable 
annual enplanements. In 2019, Sea-Tac Airport processed approximately 336,000 passengers per
bridge, well above the average of the top 20 airports of approximately 220,000 passengers. The
PLBs that are being replaced are at, or near, their end of life. Any unplanned downtime due to
PLB or fixed walkway failure impacts airlines and customer service. 
Gate C9 is one of the two bridges that will be replaced in 2021. The Gate C9 bridge has the
additional difficultly that the power lines to the 400 hz generators, and the resulting distribution
lines to eight (8) other Concourse C gates, run along the fixed walkway section of the Gate C9
PLB. In order to safely replace the fixed walkway section, the cables and conduits need to be
removed and rerouted; after which, the conduits and cables can be reconnected. This method
would leave eight (8) gates without gate 400 hz power for approximately 3 to 4 months while the
bridge is replaced and reconnected. Relocating the 400 hz in advance will avoid airlines having to
run their engines or operate diesel generators to maintain 400 hz supply at the other 7 gates 
while the gate C9 bridge is replaced. This relocation work must be completed by June 30, 2021, 
to prevent overlap with the PLB bridge replacement project. 

FINANCIAL IMPLICATIONS 
There is no additional funding being requested in this memo. Previously authorized funding will
be transferred from CIP #C800793 to CIP #C800724. 




Template revised September 22, 2016; format updates October 19, 2016.

COMMISSION AGENDA  8c                                              Page 3 of 5 
Meeting Date: November 10, 2020 

ALTERNATIVES AND IMPLICATIONS CONSIDERED 
Alternative 1  Perform work as separate major works contract at an estimated cost of $700,000
to $1,000,000 
Pros: 
(1)   Direct cost of work will be based on competitive bids. 
(2)   Minimal (overnight) 400Hz power outages to all supplied Concourse C gates. 
Cons: 
(1)   The cost of a separate major works contract would exceed the cost of a change order.
Performing this work as a separate major works contract would result in additional
administrative costs to prepare and issue bid documents and manage the contract. For
projects of this size, these costs typically range from 33% to 50% of direct construction
costs ($200,000 to $300,000 additional). 
(2)   A separate major works contract would result in delays to the replacement of the C9
PLB and would impact Alaska Airline Operations by delaying return of the C9 PLB to
service. The time required to complete design (currently at 60%), procure a contractor 
and complete this work under a separate contract is estimated to be a minimum of 9
months, which would result in a completion date of August 2021 at the earliest.
(3)   Additional risks to both projects due to concurrent work. A separate contract would
result in two contractors in the same area; this would result in a significant amount of
coordination, with a potential to incur schedule delays and increased cost to the
Concourse C New Power Center project. 
(4)   Increases risks to Concourse C New Power Center projects cost and schedule. 
This is not the recommended alternative. 
Alternative 2  Perform 400Hz relocation work utilizing small works contracts and Port crews at
an estimated cost of $550,000 to $650,000. 
Pro: 
(1) Provides the Port more flexibility in gate management. 
Con: 
(1) Cost of work would exceed small works authority ($300K) resulting in additional soft cost
to segregate the work into multiple disciplines (Civil/Mech/Elect.) and manage additional
contracts. 
(2) Requires shutdown of 400 hz gate service to 8 gates for the duration of PLB replacement.
(3-4 months) Airplanes at these gates would not be able to plug into electrical power. The
Port would need to provide temporary/portable generators run on fossil fuel to supply
400hz power at eight (8) gates while the existing system is being relocated. 

Template revised September 22, 2016; format updates October 19, 2016.

COMMISSION AGENDA  8c                                              Page 4 of 5 
Meeting Date: November 10, 2020 
(3) Increases risks to Concourse C New Power Center projects cost and schedule (similar to
Alternative 1). 
This is not the recommended alternative. 
Alternative 3 Perform work as a change order to Concourse C New Power Center at an estimated
cost of up to $600,000. 
Pros: 
(1) Overall cost, schedule  and operational risks  to the Port is reduced  compared to
Alternatives 1 and 2. 
(2) Eliminates the 6-9-month procurement time for major works contract. 
(3) Maintains the agreed upon gate closure schedule with Operations and Airlines. 
(4) Eliminates the staff and designer cost to prepare bid documents to procure this work
separate as a major construction or small works contracts. 
(5) Scope can be completed without long shutdown of the existing 400Hz electrical power
system. 
Cons: 
(1) This  work  would  not  be  competitively  bid,  resulting  in  potentially  higher  direct
construction cost. 
This is the recommended alternative. 
ATTACHMENTS TO THIS REQUEST 
None 
PREVIOUS COMMISSION ACTIONS OR BRIEFINGS 
PLB Program: 
March 2, 2020  The Commission approved advertising and executing two additional
major works contracts. 
September 3, 2019  The Commission approved $3,000,000 budget increase for the
design and construction of PLBs at Gates C15, C9, D11, C11, C18, S6, D4 and the fixed
walkways at C9, D11, C18, and D4. 
February 27, 2018 -The Commission approved $7,700,000 for the design, construction,
and purchase of PLBs at Gates C15, C9, D11, C11, C18, S6, D4, and the fixed walkways at
C9, D11, C18, and D4. 
February 28, 2017 -The Commission approved $2,300,000 for the design, construction,
and purchase of PLBs at Gates S11 and B10 and the fixed walkway at S11. 

Template revised September 22, 2016; format updates October 19, 2016.

COMMISSION AGENDA  8c                                              Page 5 of 5 
Meeting Date: November 10, 2020 
Concourse C Power Center: 
April 16, 2020  The Commission authorized $8,525,000 to advertise and award of a major
works contractor for the construction of the Concourse C New Power Center. 
September 22, 2015  The Commission authorized $1,900,000 to execute a design
contract, prepare design and construction bid documents, and authorized the use of Port
crews for preliminary work in support of this project. 















Template revised September 22, 2016; format updates October 19, 2016.