PORT OF SEATTLE 
MEMORANDUM 
COMMISSION AGENDA  STAFF BRIEFING 
Item No.         7c 
Date of Meeting    November 30, 2009 
DATE:    November 24, 2009 
TO:      Tay Yoshitani, Chief Executive Officer 
FROM:    Stephanie Jones Stebbins, Senior Manager, Seaport Environmental Programs 
Michael Burke, Senior Manager, Container Leasing and Operations 
SUBJECT:  Terminal 5 Maintenance Dredging Update 
BACKGROUND
In September 2008, the Port Commission approved funding to begin permitting and design for
Terminal 5 Maintenance Dredging. Since then, we have developed a plan for a comprehensive
approach to the project that will address the specific characteristics of shoaling within the three
berths at the facility. To date we have had discussions with the Corps of Engineers (COE) and
Dredged Material Management Office (DMMO) about our approach, and are planning to submit
the Joint Aquatic Resources Permit Application (JARPA) later this month. Once submitted, the
COE will coordinate the involvement of other resource agencies and notify the public for
comments.
The way we are approaching this maintenance dredging effort reflects lessons learned from
recent projects at Terminal 30, Terminal 91, and Terminal 18. It also reflects changes necessary
to be consistent with technical guidance that has recently been developed by the COE. Our
approach is different from past dredging projects in three principal ways. 
First, we will  be requesting approval to include an additional one-foot (1') of "advance
maintenance dredging" below the project depth for each berth. Advance maintenance dredging
is permitted in critical and fast-shoaling areas as a means to extend the interval between dredging
events and ensure the reliability and least overall cost of operating and maintaining the project
authorized dimensions. Because the shoaling experienced at T-5 berths results in part from
episodic under pier sloughing, it is difficult to predict and resolve through a routine of regular
planned maintenance. As such, doing the maintenance in advance allows for a safer and more
proactive approach, anticipating the high spots that occur rather than reacting to them. For our
project, advance maintenance dredging would increase the required dredging depth from -45'
MLLW to -46 MLLW for Berth 1, and from -50' MLLW to -51' MLLW for Berths 2 and 3.
Second, we are characterizing the geometry of the dredge prism in a manner that more accurately
portrays the amount of overdepth excavation that is anticipated. Overdepth excavation occurs
due to the inherent margin of error that results from equipment tolerances, survey inaccuracies,
wave and wind conditions, water depth and human factors. Our recent experience with dredging

COMMISSION AGENDA 
T. Yoshitani, Chief Executive Officer 
November 24, 2009 
Page 2 of 3 

projects indicates that we can expect 50-75% of sediments to be removed from two feet (2')
below the required dredging depth, and another 5-10% removed below that if rocks or large
debris are dislodged in deeper sediments. Figure 1 illustrates both the advance maintenance
dredging concept and anticipated overdepth excavation as it relates to the project. 
The third component of the Terminal 5 maintenance-dredging project that is different from
previous Port dredging applications is phasing of the work over a ten (10) year period. A benefit
of this approach is that we can differentiate dredging that is needed immediately, or in the very
near-term, from dredging that is less critical and that can be deferred to future years, all within a
single planning effort. Phasing also allows us to segregate those dredging events that will utilize
open-water disposal options from those that will be required to use an upland disposal site. 
Figure 1 Typical dredge zones and dredge prism geometry 








To accommodate a phased project plan, we will be requesting a programmatic project
authorization from the COE pursuant to 33 CFR 325.6 that would be in effect for ten (10) years.
A programmatic approach will promote comprehensive management of maintenance dredging at
T5, allowing us to anticipate and control costs as well as environmental impacts. It also serves to
minimize redundancies associated with contracting, permitting and the public involvement
process. Table 1 identifies the proposed phasing schedule, including anticipated dredge volumes,
depths and disposal methods.

COMMISSION AGENDA 
T. Yoshitani, Chief Executive Officer 
November 24, 2009 
Page 3 of 3 

Table 1. Anticipated phasing schedule, volumes, depths and disposal method 
Incidental   Dredge
Project     Advance    Overdepth                              Anticipated
Excursions   Volume   Estimated
Berth      Phase      Depth    Maintenance   (50-75%                               Disposal
(5-10%    (cubic   Schedule 
(ft MLLW)     Depth     removal)                             Method 
removal)     yards) 
Berth 1        II          -45          -46          -48         -50        3,800     2011-2012      Upland 
Open water
Berth 2        I         -50          -51          -53         -55       3,000     2010-2011 
& Upland 
Berth 3        II         -50          -51          -53         -55       7,700     2011-2012     Upland 
Future "asneeded"
III         -45/-50        -46/-51        -48/-53        -50/-55      <40,000     2012-2020       TBD 
maintenance
(all berths) 
The COE public notice process that is usually undertaken for individual dredging events would
now be combined into a single comprehensive notice that the public would receive following our
application later this month.
It is important to note that the programmatic approach will not reduce regulatory oversight and
environmental protection. Conditions of the programmatic approvals would necessarily require
that the Port coordinate each dredging event with the respective regulatory agencies and tribes.
Each planned phase of dredging, including future "as-needed" phases, would not move forward
without their concurrence or approval. 
Finally, it should be noted that sediments within the dredge prism in Berth 2 have already been
assessed and a significant portion satisfy the regulatory criteria for open water disposal. It
should be recognized that the open water disposal option allows for a significant cost savings
compared to upland disposal options. The Commission should also be aware that regulations
may be changing in the near future, and the open water disposal option for Berth 2 may likewise
change. The option may be preserved, however, if permit applications are submitted prior to the
new regulations becoming effective. Either way, the Commission would retain the ability to
decide whether the dredge spoils should be disposed of at an open water site or upland site.
The project team is excited to undertake next steps for this project, which include submittal of
the JARPA, stakeholder coordination, Phase I and II dredge design, and the procurement
process.