Deep Draft Navigation > Part I: Introduction > Chapter 5: Port and Vessel Operations> 5.5
Navigation Constraints
Deep Draft Navigation
Part I: Introduction
5.5 Navigation Constraints
There are several types of constraints that impact port and vessel
operations. These constraints need to be considered in describing and
modeling any without- or with-project conditions. Some constraints
may also be opportunities for improvement under the with-project
alternatives and some are external factors out of the team’s hands to
manage.
Beam Constraints
Beam is the width of the ship at its maximum width. Beam constraints
related to channel width exist when two vessels cannot safely pass in
the channel as an ordinary operation (excluding weather-related
events, such as fog and high winds).
Most pilots will require channel width to be four times the vessel
width, allowing for two times the vessel width for beam clearance
between passing vessels to allow for ample clearance between each
vessel and the channel lane. EM 1110-2-1613 details the Corps
engineering guidance on this and other aspects. However, every port is
different and this constraint should be discussed and researched in the
pilot’s handbooksand through port and pilot discussions.
Beam constraints are particularly important when larger beam vessels
are projected as part of the with-project vessel fleet forecast. To the
extent that beam operational conflicts exist that are not addressed with
the plan formulation, the affected vessels will experience delays as a
result of one-way channel movements.
Beam conflicts and resulting delays can be simulated by a queuing
model that looks at the probability that vessels will arrive at or near the
same time and thus be delayed. The HarborSym Model from IWR can
help model this feature. Some port and vessel scheduling can avoid
these passes, so it is important to discuss these scenarios with the port
and pilots.
It is important that the economist verify that the beam conflicts are
operational across a size category of vessels and not subject to pilot
discretion, weather, tide circumstances, etc. A distinction should be
made between beam clearance preferences and actual practices.
Vessel Length Restrictions
Vessel length restrictions may be absolute prohibitions or may be
relative to remedial measures, which typically include additional tug
assistance and/or requirement of working bow thrusters. Each
additional tug adds an increase in the transportation cost of the vessel
movement.
Bow thruster restrictions are a common practice. They require that
vessels of a certain size (LOA) have working bow thruster(s) for
enhanced maneuverability in the channel or additional tug assistance
(or other restrictions):
Most conventional large bulk vessels do not have bow thrusters
including tankers.
Smaller bulk vessels may be equipped, particularly if they are
deployed in trades with frequent port calls (e.g. chemical carriers
and shuttle tankers)
Most container vessels have bow thrusters for enhanced
maneuverability while docking and undocking.
In some instances improved tug performance may eliminate the
requirements for bow thrusters for channel maneuverability with
curvature.
The economist should understand the relationships between tug
assistance (number, type and horsepower) and bow thrusters when
there are channel maneuverability issues for particular sizes of vessels
applicable to the benefiting fleet. Adding tugs can also be considered a
non-structural alternative, but this also adds additional costs.
Panama Canal
One natural constraint for ships transiting west to east is the Panama
Canal. The Panama Canal is actually a network of artificial channels
and locks that connect various lakes. The width of the existing lock
chambers (Gatun, Miraflores, and Pedro Miguel) are 110 feet wide by
1,050 feet long. However, the largest vessel that can transit the canal is
a Panamax vessel. EM 1110-2-1613 dictates that the maximum sailing
dimensions are 105.75 feet (32.2 meters) beam width, 950 feet (289.6
meters) long, and 39.5 feet (12.5 meters) depth in fresh water (less in
the dry season) and about 38.5 feet in saltwater. Consequently, vessels
sailing from the East Coast U.S. (ECUS) and Gulf Coast U.S. (GCUS)
will typically not sail deeper than 38.5 feet unless they lighter or
otherwise discharge cargo prior to transiting the Canal. 17 There are
also additional restriction in various places in the canal and air draft
restriction from the Bridge of the Americas.
More recently, construction has begun to increase the depth and
channel width a bypass the existing locks. The expansion also includes
two new locks that have three chambers each. One will be on the
Atlantic side and one on the Pacific side. The locks are schedule to be
completed in 2014. The new lock dimensions will be 180 feet wide,
1,400 feet long, and 60-feet deep. This means that a post-Panamax
vessel capable of sailing through the canal will be up to 160 feet beam,
1,200 feet long, and 50-feet deep. This would reduce restrictions and
increase the amount of goods carried. The expanded canal would have
the capability to allow a 12,000 TEUs containership to pass, which
more twice that of the existing canal that allows 5,000 TEUs.
The multimedia link on the Panama Canal Authority is
recommended to get a better view of the canal and its expansion
through live cameras and more. A paper titled "Implications of
Panama Canal Expansion to U.S. Ports and Coastal Navigation
Economic Analysis (PDF, 161 KB) by IWR further examines some of
the issues related to the Panama Canal and future manual updates will
provide more information.
Panama Canal Tolls:
The following website describes how
tolls were historically set and how they
are set today:
http://www.pancanal.com/eng/maritime/tolls.html.
Suez Canal
The Suez Canal, owned by the Suez Canal Authority, is located in
Egypt and serves as a major worldwide transit point that connects
Europe and Asia without having to circumnavigate Africa. The canal is
about 118-miles long and has a single lane with several passing zones
and no locks. The maximum sailing draft as of 2009 was 62-feet
according to the Suez Canal Authority. Some vessels may be
constrained by the Suez Canal Bridge which is 223-feet high. The
channel accommodates what is known as the Suezmax, which is
almost exclusively tankers and has a width of up to 151-feet and
150,000 tons. The existing width can accommodate a vessel of up to
230-feet, but there are few tankers that meet this criterion and can fit
within the depth. However, planned improvements that are scheduled
to be completed in 2010 will increase the depth to 66-feet. The
improvements would allow supertankers to pass though. More
information on the canal is available at http://www.suezcanal.gov.eg/
. A cross-sectional area shows the various vessels sizes that can
transit the canal.
Figure 5-1: Cross Section of Suez Canal18
Other Constraints
Any other impediments to unconstrained movements of vessels should
be identified because they might constrain growth of the fleet from the
perspective of numbers and sizes of vessels expected to call. They can
include:
1. Airspace Restrictions: many ports are located near airports.
Some vessels or cranes may be so tall that they are in regulated
airspace.
2. Traffic Management: Traffic management is used in a few
major European ports and international canals, like Suez and
Panama. It is similar to air traffic control operations and just as
sophisticated.
3. Encounter Restrictions: Some ports issue encounter
restrictions on movements of hazardous cargoes such as
liquefied natural gas (LNG) vessels or military vessels. These
restrictions require other vessels of particular sizes not to pass
(encounter) these vessels. Sometimes, the restriction is to stop all
Section 2-7 of EM 1110-2-1613 lists
several considerations for constraints
and risks
(encounter) these vessels. Sometimes, the restriction is to stop all
movements in a port. Although LNG vessel calls may be low at
the time of the study, the economist should anticipate how these
restrictions will affect the benefiting fleet, particularly if there is
a growth in LNG and the benefiting fleet leading to more
encounters and delays. The military’s role in the port should be
analyzed and described if it impacts the port operations.
4. Bridge Restrictions: The economist should make allowance for
any bridge delays or restrictions for opening/closing and
accommodation of passing vessels that may be present.
5. Weather-Related Constraints: Weather-related constraints can
be acknowledged unless there is evidence that sustained
disruptions to normal operations occur (such as seasonal fog).
6. Port and Landside Capacity Constraints: The economist
should understand the capacity of cargo handling and storage
systems and any landside constraints that may affect the ability
of the marine terminal to receive or discharge cargo in sufficient
volume to meet ship berth times. Berth capacity constraints will
be an absolute impediment to vessels in the absence of such
things as new cargo handling and storage capacity. Such
constraints can result in capping vessel and cargo forecasts as a
function of maximum port throughput.
7. Cruise Ship Priority: Some ports give priority to cruise ships in
order to keep their passengers happy. The economist should be
aware of this arrangement and consider this in their analysis.
8. Safety Zones: Certain vessels such as oil tankers, LNG and
cruise ships may have more restrictive rules surrounding their
movements. For example, other traffic in the port may have to
come to a complete stop while an LNG vessel is moving. Other
vessels may have an increased buffer zone for nearby vessels.
This movement and restriction can be modeled using
HarborSym.
9. Capacity: Once a good is transported to the port, sometime it is
directly shipped onto its final destination and other times it is
stored on-site or nearby. Containers in particular are often stored
before they are shipped; this is evident by the stacks of boxes in
the port. It is possible that some ports now or in the future may
have troubles moving these boxes out quick enough and not have
enough storage capacity. Cranes can be so fast that they can
unload boxes almost too quickly. The same potential capacity
issue could be said for other cargo and petroleum. The
economist should investigate this as a possibility.
10. External Factors: Other factors may be outside the team or
port’s controls. These factors can be easily be used in the
existing conditions if they are ongoing; however, predicting the
future on some of these factors is impossible. Some examples
include: NAFTA or GAFTA regulations, union strikes, whale
strikes resulting in changes in vessel operational rules,
hurricanes, war, acts of God and so on.