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5
Options for Handling
Large Vessels
Several alternatives have been proposed to accommodate large vessels.
This chapter describes five, and compares them by the committee's
criteria (economics, navigational safety, environmental effects,
national security/defense implications,and contribution to future
flexibility). These alternatives are in different stages of
development--a few have long been in use, others represent more recent
applications of existing technology, and some are speculative.
The five principal options considered by the committee are:
Construction dredging, that is, underwater excavation of
materials to create a wider/deeper channel for larger vessels,
can be undertaken at existing ports. It should be understood
for the comparative purposes of this chapter that the other
options described are not necessarily exclusive of dredging.
Offshore terminals, designed to accommodate deep-draft vessels,
are usually dedicated to a specific commodity. State-of-the-
art examples of several types are now in service in many parts
of the world.
The design and construction of new deenwater Forts or offshore
industrial islands represent major regional or national
commitments. New multicommodity harbors (such as Europoort) and
new deep ports for one or two commodities have been built in
other countries, and proposals have been advanced in the U.S.
for such developments.
The use of wide-beam ships, with substantial cargo-carrying
capacity and drafts compatible with the depth limitations
typical of ports in the United States, have been proposed and
designed, but not built. Among the problems to be resolved are
structural design, maneuverability, and power requirements.
Lightering of incremental cargo may be used either to lighten
. . .
.
incoming ships to drafts compatible with channel depths or to
top-off outbound ships. Transfer terminals, enabling rapid and
economical transfer from barges to ships, have recently been
constructed at New Orleans, and self-unloading barges have been
built for top-off services on the East Coast.
40
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Alternative means of cargo transfer accompany several of these
options--dry transfer of crushed or pelletized cargoes by conveyer
belts, tramways, or monorail; pipeline transfer of bulk liquids or
slurried solids--and may, depending on the over-all design and
application, serve as alternatives to dredging. There appear to be no
effective alternatives to inner harbor areas for the transfer of
containers, owing to the large amount of space required (35 acres or
more per containership berth). A trend emerging with operation of the
new large containerships is to designate a major port for calls by
these vessels and to use feeder ships to collect and distribute
containers to and from other ports. While this might have some
implications for dredging, the trend is too recent to evaluate. The
cargo-transfer alternatives described in this chapter have all been
developed for bulk and break-bulk cargoes.
The alternatives described and compared in succeeding sections need
to be evaluated in the specific contexts of their proposed applications
for capital costs; compatibility with existing infrastructure, and with
existing land and sea transport; operational costs; environmental
considerations; political considerations; and safety. No general
characterization can be made of the dominating considerations or unique
circumstances that would guide the choices to be made in a particular
location.
CONSTRUCTION DREDGING
As dredging is the principal subject of this report, various aspects
are described in detail in other chapters, and only a brief description
is given in this section. In dredging, materials below the water
surface are excavated and transported to a designated site for
placement. Navigational channels, maneuvering areas, anchorages, and
berths have been created and maintained by dredging for many hundreds
of years. "Construction dredging" refers to excavation of virgin
materials either to create or to improve (by deepening, widening, or
lengthening) these navigational facilities.
In the context of dredging to accommodate large vessels, it bears
mention that while the placement of dredged material is often
incidental to the objectives of dredging, it is sometimes the primary
objective--creating landfill, for example, to expand terminal
facilities. In the proposals of some ports for construction dredging,
enlarging the navigational facilities and creating landfill for new or
expanded terminals are equally important in accommodating large vessels.
OFFSHORE TERMINALS
Offshore terminals have long been recognized as a potentially optimum
solution for bulk cargoes. They are usually designed for one
commodity, restricted to use by large vessels, and equipped with
modern, efficient handling and transfer facilities.
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An advantage of these terminals is that they are located offshore,
at a distance from concentrations of people and facilities, and are
usually in open waters. Thus, a disaster such as fire or explosion
would be remote from areas of extreme vulnerability, and accidental oil
spills and airborne contaminants would be more likely to be dispersed.
These advantages depend to some extent on remoteness, which may add to
the cost of an offshore terminal, and in the case of dispersal' on
winds and waves that may not be favorable. Generally, however,
offshore terminals can greatly reduce the risks of certain cargoes to
concentrated human populations and to restricted environments, such as
estuarine marshes. Because the characteristics of the commodity are
known, specialized safety and pollution-prevention equipment can be
installed.
In a discussion of the advantages and disadvantages of offshore
terminals, Soros (1983) emphasizes the protection of coastal resources
as the primary advantage, and among the problems, lists the following
for marine operations:
The tug-ship operation in the open sea
The docking approach, especially with adverse winds, waves, and
currents
Attachment of mooring lines to buoys, dolphins, and pier
structures, and detachment, especially from mooring buoys
Decision about when to leave berth owing to worsening weather
The principal constraint acting against construction of offshore
terminals is their high capital costs. The Japanese contribution to an
international study (Permanent International Association of Navigation
Congresses, 1977) stated opposition to uncoordinated planning of
offshore oil terminals, and support of joint operation "to ensure the
efficient operation of berths, facility of construction, and safety to
maritime traffic." Many offshore terminals (for example, the Drift
River Terminal, Cook Inlet, Alaska) are operated by consortia, and
others are operated as public utilities.
Offshore terminals have occupancy rates ranging from 65 percent to
90 percent, depending on exposure and design. Occupancy is important
in determining the economic promise of such a facility, since unusable
time incurs extra costs for the terminal and the vessel.
The principal types of offshore terminals are described briefly in
succeeding sections.
Fixed Offshore Structures
Fixed offshore structures, against which vessels berth for cargo
transfer, are supported by piles or caissons. Delivery to (from) shore
is usually by pipeline or conveyor. Three examples, among many
worldwide, are:
.
The offshore oil terminal at Tomokomai, Hokkaido, Japan, located
5 miles offshore in the Pacific Ocean, where prevailing winds
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blow seaward, accommodates very large crude carriers up to
350,000 DWT. A pneumatically controlled oil boom is raised from
the seafloor as the ship docks. Vacuum suctions prevent oil
spillage when the transfer lines are disconnected.
The coal export terminals two miles offshore Hay Point, MacKay,
Queensland, Australia. Coal is transferred on covered conveyor
belts. Stockpiles on shore are sprinkled to reduce dust.
The offshore iron ore export terminal at Port Latta, Tasmania,
Australia, where pelletized iron ore is conveyed two miles out
to a terminal in the open sea for loading into large ore
carriers.
A fixed terminal was proposed for liquefied natural gas (LNG) in
waters offshore southern California to minimize the risks to coastal
populations of an explosion or ignited cloud of gas. The proposal
called for regassif~cation of the LNG and transportation ashore by
submarine pipeline.
Spread-Type Offshore Moorings
An example of a spread-type offshore mooring is located offshore E1
Segundo, California. Incoming tankers moor to a system of buoys. The
hose to the submarine pipeline is lifted from the seafloor and
connected for discharge. This system requires tug assistance in both
mooring and cutting loose. The time for connecting and disconnecting
is correspondingly longer, and the use of the berth is restricted to
calm and moderate seas, with winds from westerly directions.
Single-Point Moorings
The ship moors to a single-point buoy or articulated arm, and the hose
is brought aboard for connection. The ship swings or "weathervanes"
about the buoy. This system is widely used throughout the world for
oil shipment and (to a lesser extent) for oil imports. Examples of the
latter are at St. John, New Brunswick, where the 30-ft tides would make
any fixed terminal very expensive. The single-point mooring has also
been used for iron-ore slurry transfer off New Zealand, described by
Wasp (1983~:
Placed in operation in 1971, the Waipipi Iron Sands project consists
of a relatively short land pipeline and a ship-loading system. A
1.8 mile undersea line carries the slurry to an offshore mooring
buoy, where special Marconaflo tankers load the slurry and then
de-water it on board. After the transport water is removed from the
cargo and piped ashore, the tanker sails to its destination with the
iron ore.
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Floating Terminals
Floating storage and transfer facilities include the Arco Seki Ardjuna
terminal for liquefied petroleum gas (LPG) in the Java Sea, and
numerous floating offshore oil storage vessels in Indonesia, West
Africa, the Persian Gulf, and elsewhere. Vessels are usually moored to
an articulated arm or single-point mooring, so as to weathervane. For
transfer operations, vessels come alongside or astern. Similar
floating terminals have been proposed for LNG service.
Offshore Storage Caisson Terminals
This category includes the Dubai steel tanks placed underwater for oil
storage, and the many large concrete caisson structures in the North
Sea, which store oil for transfer through an associated articulated
mooring buoy. Direct offloading concepts have been developed but not
so far used because of concerns about tanker override.
Offshore Terminal Complexes
The outstanding example of an offshore terminal is the Louisiana
Offshore Oil Port (LOOP). A complex of single-point moorings is
connected by submarine pipelines to a control and pumping terminal
structure for transfer by submarine pipeline to onshore and inland
refineries. A similar project has been proposed for Freeport, Texas,
to handle 500,000 barrels of oil per day. These "superport" projects
have been hard hit by the decline in demand for imported oil (in the
United States) and by the withdrawal of federal financial support.
This has dimmed the prospect for additional building and expansion.
Worldwide, most offshore terminals are located in countries other than
the United States, yet the majority were designed by engineers and in
many cases, constructed by contractors from the United States. This is
in large part because such terminals are designed for one commodity,
and sometimes for dedicated vessels, and are financed on the basis of
export or import of that single commodity.
NEW PORTS; INDUSTRIAL I S LAND S
Construction of entirely new ports with deep-water capabilities is one
means of accommodating large modern vessels. Historically, new ports
or industrial islands have been planned as part of economic development
projects--the import of raw materials, for example, being coordinated
with onshore processing or manufacturing. New ports have been
developed in Japan in the last several years for petroleum,
petrochemicals, and alumina-bauxite. Examples of such developments are
the East Harbor at Tomokomai, Hokkaido, Japan, and Sines Harbor in
Portugal.
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A much larger industrial-island development was studied for the
Netherlands, with the conclusion that the high capital costs could not
be justified. Industrial islands to handle oil imports have been
proposed for the New York Bight Apex and Port Angeles, Washington.
Neither has attracted investor interest with the recent decline in
imported oil. Los Angeles, California, has conducted preliminary
studies of an offshore "Energy Island" that has the principal aim of
moving the transfer of hazardous and potentially polluting cargoes away
from the densely populated Inner Harbor area. The Port of Los Angeles
has long recognized a "hazardous footprint" in the proximity of
terminals and tanks to fish canneries and public harborfront
developments.
In the United States, development of a new port in the lower
Delaware Bay was the subject of a recent conference (Firstport, 1984,
proceedings in preparation). The obstacles that would have to be
overcome by such an ambitious plan far exceed those of dredging
existing ports in the United States (and indeed, dredging and land
reclamation would be significant in creating this new port).
WIDER-BEAM CARRIERS WITH RESTRICTED DRAFT
Increasing any dimension of a vessel can significantly augment
cargo-carrying capacity. One alternative to deeper ports, therefore,
is large vessels of shallower draft and wider beam. Hydronautics, Inc.
(1982), Roseman (1979), Roseman et al. (1974) and Roseman and Barr
(1984) describe the development and analysis of designs for dry bulk
carriers of 60,000 DWT to 200,000 DWT, having restricted drafts of 35
to 55 ft.
Relatively wide-beam vessels have been built and operated, but most
of those 100,000 DWT or more are not restricted-draft designs, and
exceed the water depths of almost all U.S. ports, fully loaded.* An
exception is the Amoco Trinidad-class tanker, 150,000 DWT and 50 ft
draft, which can call on West Coast tanker ports (Valdez, Los Angeles,
Long Beach) fully loaded, and on Gulf Coast ports somewhat
light-loaded. (Ono et al., 1985~. The existing vessels and the
restricted-draft design series follow the dimensional ratios required
by classification societies and considered reasonable limits by naval
architects.
Departures from these limits have been suggested: Mitsubishi (1974)
proposed an ultra-shallow-draft vessel, a 105,000 DWT bulk carrier that
would have a 64 m (210 ft) beam and 10 m (33 ft) draft. There are some
concerns with radical designs; for example, as the structural design of
the hull will no longer follow the semi-empirical rules of ship
*British Steel, 173,000 DWT, 58 ft draft; Shinho Maru, 208,952 DWT, 60
ft draft; BHP ore carrier, 222,000 DWT, 60 ft draft.
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classification societies, design criteria for torsion due to
quartering waves would be required.*
Wide-beam vessels are sensitive to underkeel clearance, and can be
more difficult to maneuver in restricted waters (Landsburg et al.,
1983; Roseman et al., 1974~; however, this problem is overcome on
existing (single-screw) vessels by much larger rudders. The
Mitsubishi ultra-shallow-draft design is dual-propeller, dual-rudder,
reminiscent of an articulated tug-barge combination.
Very wide-beam vessels (140,000 DWT or more) of greatly restricted
draft could require additional channel widths, and may exceed the
reach of existing loading equipment for dry bulk commodities in U.S.
ports.
The advantage of wide-beam, restricted-draft vessels is that given
a specific draft limitation, they are more economical than smaller
vessels with conventional proportions. However, the advantage of
larger, restricted-draft configurations tends to diminish as they
approach extreme proportions. Given a specific deadweight
requirement, the greatest transport economy (subject to voyage
constraints and practical design limitations) is obtained with
conventional deep-draft vessels. For cargo-carrying capacities above
100,000 DWT, foreign shipowners have so far been unwilling to accept
the draft limitations of U.S. water depths as a design criterion.
L I GHTE R I NO/TOP P I NG- OFF
Lightering--unloading part of a vessel's cargo to allow it to proceed
at lesser draft--has been practiced for hundreds, perhaps even
thousands, of years. Until recently, lightening operations have
involved low rates of cargo transfer. New self-loading and -unloading
barges and bulk transfer facilities have transformed this ancient
practice, particularly for the reverse operation of loading vessels in
deeper water with the extra cargo that could not otherwise be loaded.
Midstream transfer facilities to handle barge-to-ship transfer at high
cargo rates are now in operation in New Orleans for most bulk
commodities. A topping-off service to load coal into large bulk
carriers unable to load fully in the ports of Hampton Roads, Virginia,
has been developed for the lower Delaware Bay, in an anchorage area
used to lighter oil from larger to smaller tankers (Dowd, 1983~. The
advantages of lightering/topping-off services such as these are:
Potential for use by several ports and many shippers
Low capital investment
Rapid and progressive implementation
Costs borne directly by users
Flexibility to use topping-off vessels in other functions
-
*Hull forms similar to that of the ultra-shallow-draft design have
been built for heavy-lift roll-on/roll-off vessels, but not for
tankers or bulk carriers.
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The disadvantages, depending on particular circumstances, are:
Higher risk of fire and spills, owing to higher exposures
More vessel time required to load cargoes
If carried out in the open ocean, dependence on weather
CARGO TRANSFER TECHNOLOG IE S
An especially attractive means of cargo transfer is emerging--the use
of slurries to transport coal and iron ore--and it may enhance the use
of offshore terminals. Other materials, such as copper ore, can also
be Flurried, but the volumes do not usually justify the use of an
offshore terminal.
The most commonly used slurry medium is water, but oil, methanol,
or liquid carbon dioxide might be used. As noted, iron sands in New
Zealand are slurried and loaded in dedicated vessels. Slurry
transportation of coal has been demonstrated (Wasp, 1983), and can
readily be applied to the loading of vessels (Bertram, 1982~.
Roseman (1979) states that slurry carriers for pelletized ores and
other dry bulk commodities in converted or new special bulk carriers
can be considered state-of-the-art technology, owing to the following
advantages:
Reduced cargo handling time between ship and terminal
Elimination of airborne pollution from mechanical handling of
coal
Ability to operate from offshore terminals employing
single-point moorings, permitting the use of large deep-draft
vessels, with corresponding economies of scale
System compatibility with proposed coal slurry pipelines
Among the several proposals, coal slurry would most likely be
pumped in 50 percent concentration (by weight) from shore storage to
special slurry tankers via submarine pipelines, and dewatered to about
75 percent coal, 25 percent water. Closed-circuit pipelines could be
used to eliminate discharge to the sea.
Harris (1983) discusses slurry loading of vessels as an alternative
for long-term improvements to coal-exporting facilities in
Australia. Among his principal recommendations is: "Loading of coal
by pumping slurry or capsules to offshore berths at single buoy
moorings." This is an adaptation of the offshore terminals developed
for crude oil and petroleum products. The advantages of such a system
would be:
The pipeline would cost less than a jetty equipped with a
conveyor
The loading point can be farther offshore and accept larger
ships
The loading equipment would be less expensive
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· The time to build the facility would be reduced
· As with other offshore facilities, adverse effects might
possibly be lessened for sensitive environments
While slurry transfer of iron ore, copper ore, and coal has been
well established for long-distance transfer over land, its use in
loading ships is relatively new. However, it has been thoroughly
engineered, and shows promise as a practical and economical mode for
the future.
Tramways and Monorails
The use of tramways and monorails for transfer of dry cargo from shore
to ship, or ship to shore, has been studied periodically by the U.S.
Army and Navy, primarily as a means of unloading military cargoes onto
undeveloped coasts. The commercial application of these techniques
for loading bulk carriers has been studied and rejected; for example,
to load iron ore in Goa, India. These systems have inherent
limitations; slow loading rates, problems with excavation from the
holds, and potentially high maintenance costs.
Because of their limited capacity, tramways are limited in use to
high-density, high-value cargoes such as copper ore. It is uncertain
whether sufficient commercial or military interest exists to carry
forward the engineering development of tramways or monorails.
COMPARISON BY THE COMMITTEE' S CRITERIA
In this section, the previously described alternatives are compared by
the committee's criteria--economics, navigational safety,
environmental effects, national security and defense, and contribution
to future flexibility. This comparison is necessarily general: a
detailed comparison could only be made on the basis of well-developed
plans for each alternative.
Economics
Of the alternatives considered in this chapter, the construction costs
of a new deepwater port would appear to be the greatest and those of
topping-off services the least. Estimates have not been developed for
the only recent new-port proposal in the United States (in the lower
Delaware Bay). A five-year, $10 million study of the Delaware Bay
proposal has been suggested (Gaither, 1983~. Owing to the number of
existing ports and their competition with one another for cargoes, it
has been remarked (Firstport, 1984) that several ports in a region
would have to participate as investors in the development of a new
port, and continue to support it with feeder and transshipping
services. A group of ports in a region might not be able or willing
to make such a large investment: it is possible that some combination
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of federal, state, and local investment guarantees would be necessary,
as well as formation of a public-private, or very large private
consortium to finance and manage such a project. Prospects for such
developments in the United States appear questionable.
As indicated in Chapter 4, the construction costs for dredging the
five ports with proposals for dredging to 50 ft or 55 ft depths range
between $278 million and $440 million. The range of estimated
construction costs for dredging each of the five ports proposing to
accommodate the latest-generation containerships is between $3 million
and $80 million. For containerships, there appear to be no effective
alternatives (other than new deepwater ports) to dredging existing
ports.
For liquid- or dry-bulk commodities, the economic advantage of
deepening existing ports and harbors in comparison to the non-port
alternatives is that loading and unloading is assured if the ship can
be brought to port. Offshore alternatives are all weather-sensitive
to greater or lesser degree, and this can affect ship schedules.
Delays may not be as large an economic factor as other factors,
however. Since the alternatives tend to address specific needs, their
economics tend to be specific to location, commodity, timing, intended
throughput, and actual volumes handled.
The offshore terminals already installed in waters of the United
States are all oil terminals, and these are not in every case
competitive with transshipment from larger into smaller tankers for
unloading in existing ports. This may be due to timing or to a
combination of factors that different market conditions would reverse.
Proposals for coal slurry pipelines to carry coal from mines to
deepwater terminals have estimated costs of $140 million to $750
million (Bertram, 1982~. Coal slurry transportation and loading
systems would depend for their economic competitiveness in part on
achieving lower inland transportation costs. The costs associated
with the terminal end of such systems are almost certain to be higher
than those of already existing terminals, and could only be
competitive in loading large bulk carriers. To pay for themselves,
offshore coal terminals would need to handle substantial volumes.
A wide-beam vessel of 120,000 DWT capacity and 38 ft draft has been
estimated to cost $120 million to build in the United States (1980
dollars). Estimates have not yet been developed for larger wide-beam
vessels with very shallow drafts (Bertram, 1982~. Large vessels of
extreme proportions may have hidden system costs, and may not be
competitive with already existing large bulk carriers. Except in
special cases, given the worldwide surplus of very large carriers of
oil, coal, and ore, and hence, the low cost of using already existing
large carriers, constructing a fleet of vessels to such specifications
appears unlikely except for "captive" runs. One of the principal
reasons for design studies of these vessels in the United States was
to give the U.S.-flag merchant marine large bulk-carrying capacity.
This motivation has been clouded by the uncertain economic return that
could be expected from such vessels in competition with the existing
heavily over tonnaged world bulk-carrier fleet, the probable need to
reserve a percentage of U.S. coal exports for the vessels, and the
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government's announced intention to eliminate subsidies for the
construction and operation of U.S.-flag vessels.
Of all the alternatives considered, topping-off has the shortest
lead times and lowest capital investment. Investments have already
been made in three technologies (floating terminals, self-unloading
ships, and self-unloading barges), and this existing capability
enables short-term response to the need to load large-volume bulk
carriers. To gain the needed return on the investment depends on the
willingness of shippers and shipowners to pay the additional cost, and
spend the additional time for topping-off operations. Thus, the
charge per ton (averaged over total tons carried) cannot exceed the
transportation cost-savings per ton of using larger vessels, and for
the past three years, this has represented a relatively small
difference.
The economically most attractive alternatives for accommodating
large vessels appear to be construction dredging of existing ports and
lightering/topping-off.
Dredging of existing multicommodity ports is attractive for the
following reasons:
.
· Economies of scale associated with large vessels are provided
for all commodities and cargoes which could benefit
Existing multicommodity, multipurpose ports offer economic
protection against the volatile fluctuations of trade in single
commodities
· Existing ports represent already sizable investments in
terminals and other port facilities and services (described in
Chapter 4), as well as established infrastructures of inland
transportation. Among the existing services of ports are
worldwide sales organizations (allowing them to pursue
vigorously whatever cargoes are available)
There are, of course, economic risks associated with dredging: the
capacity created in anticipation of demand may exceed actual demand or
fail to serve it, and the emergence of new technologies could make
improvements obsolete.
Navigational Safety
As with economic issues, the navigational advantages and disadvantages
of various alternatives for accommodating large vessels cannot be
assessed in detail without well-developed plans. Any engineered
system represents a set of compromises between several goals; for
example, between project cost and safety, and forces and features of a
particular environment. Following is a summary of experience with the
trade-offs which must be made with each of the alternatives.
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New Construction Dredging
Dredging existing ports offers the opportunity to enhance the safety
margins cf vessel operations in approach channels and within the
sheltered waters of a port. New construction dredging also offers the
opportunity to accommodate even larger vessels and more traffic in
these navigational facilities with smaller margins of safety. Thus,
the contribution to navigational safety of new construction dredging
in existing ports depends on adequate design, maintenance, and
operational practices.
Offshore Terminals
Offshore terminals are located in deep water, as opposed to the
protected waters of coastal ports and harbors, but their relatively
greater exposure has not resulted in higher rates of casualties than
similar port and harbor operations. Docking and undocking may be
simpler than the equivalent operation at port terminals, and offshore
terminals may reduce port vessel traffic.
A particular problem for offshore terminals (if tug assistance is
required) is the availability and capability of oceangoing tugs:
those that are used to assist harbor maneuvers are not designed for
open ocean conditions, and the tugs designed for oceangoing functions
are not designed for the maneuverability of docking and undocking
operations.
New Deepwater Ports
The contributions of a new deepwater port to navigational safety could
be substantial, but this would depend on the relative importance of
this criterion as a design goal. The opportunity to enhance
navigational safety by providing ideal channel layouts and approaches
may be considerable. Any comparison would have to take into account
the specific circumstances and characteristics of existing ports in
the region that might be improved versus those of the new port.
Wide-Beam Vessels
The preliminary tests of extremely wide-beam, shallow-draft vessels
for inherent controllability by computer simulation (Eda, 1983,
Aranow, 1983) indicate that they are unresponsive. The problems
exhibited in simulated maneuvers can probably be solved by very large
rudders, rudders of different design, and other adjustments, but these
could also affect the vessels' economics in greater power
requirements. Large wide-beam vessels with drafts of 50 ft to 60 ft
have been built and operated successfully. Depending on their
dimensions and trade, such vessels could require additional dredging
in many U.S. ports.
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A large wide-beam vessel of shallower draft could require channel
widening for navigational safety. An additional navigational concern
for wide-beam vessels is narrow bridge openings. These already
present a navigational hazard in many U.S. channels (Marine Board,
1983).
Topping-Off
Topping-off or lightering operations carried out in semi-protected or
unprotected waters (where sufficient water depth is available) imply
some dependence on weather. For midstream loading, winds acting on
the unloaded or lightly loaded vessel are perhaps the factor of most
concern in operations. Generally, the navigational safety of
lightering, topping-off, and midstream transfer are about the same as
for offshore terminals, with the obvious difference of involving two
vessels, and for oil transshipments, have been carried out for many
years without major casualties.
Environmental Issues
While the potential environmental effects of some alternatives for
handling large vessels are associated with construction or the
disposal of dredged material, others are principally associated with
the vessels and their cargoes. The committee has not assessed or
compared these latter risks in detail.
The potential environmental effects of any alternative are highly
site-specific, and adverse effects may be averted or mitigated by
conscientious planning, siting, engineering, and operations. Some
general observations about the potential environmental effects of the
alternatives are offered here.
New Construction Dredging
The environmental implications of new construction dredging are
discussed in Chapter 9. These vary with the specific characteristics
of the project, the characteristics of the physical and biological
environments of the project and disposal sites, and other factors,
and can only be known in site-specific studies. Some of the general
points made in Chapter 9 deserve mention for comparative purposes:
(1) potentially adverse environmental effects can be caused by
dredging and the disposal of dredged material; (2) adequate planning,
design, action, and follow-up activities give reasonable assurance of
minimizing and managing the environmental consequences of dredging and
disposal of dredged material (that is, an adequate base of scientific
and technical knowledge exists to guide decisions and action); (3)
dredging may have some environmental advantages--removal of
contaminated materials (if properly managed), beach replenishment, and
wetlands rehabilitation.
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Offshore Terminals
As indicated in preceding sections, there are environmental advantages
to locating certain terminals offshore, and those of the United States
are sufficiently far from shore to ensure maximum protection of
coastal resources and concentrations of population from catastrophic
or operational pollution and accidents. For coal terminals offshore
(none now exists in the U.S.), questions of environmental implications
might be raised about the fluid medium in the slurry, and its ultimate
fate and effects.
New Deepwater Ports
It is likely that the greatest change to the local environment from
the creation of a new port would occur with shoreside developments,
particularly as the sites proposed for new-port development have
little existing landside infrastructure. Dredging would also be
required (both construction and maintenance) in these locations, even
though existing water depths are greater than the natural depths of
existing ports, to create berths and other facilities, and to make
depths uniform. How much dredging would be required (and the
environmental effects) depends on the design and layout of the port,
and on its site-specific characteristics.
A detailed risk and consequences assessment would be necessary to
determine the level and severity of hazards posed to the environment
and surrounding populations of vessel casualties.
Wide-Beam Vessels
Environmental implications of wider-beam ships would appear to be
comparable to those of full-form tankers, with one major exception,
and that exception is that channels may have to be widened rather than
deepened, particularly if two-way traffic is desired. As with any
dredging project, the potential exists for adverse environmental
effects.
Topping-Off
Concerns have been expressed about the environmental effects of
topping off large bulk carriers with coal in the lower Delaware Bay
(Biggs et al., 1984~. These concerns center on the fates and effects
of coal lost to the air and water in the transfer operation.
Environmental concerns have not been raised for topping off in the
Gulf of Mexico, or for midstream transfer in the Mississippi River,
where the operations are viewed as comparable to coal loading at a
port terminal (Chatagnier, 1983~. There are no ports in the lower
Delaware Bay: the anchorage proposed for coal topping-off has been
used for oil transshipment and is regulated by the U.S. Coast Guard.
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The Coast Guard conducted an environmental assessment in reviewing the
permit application (the permit was granted), but authority over the
environmental quality of Delaware's coastal waters was claimed by the
state Department of Natural Resources and Environmental Control and
Delaware law has been interpreted to prohibit the proposed topping off
activities.
National Security and Defense
Much of the nation's contingency planning for national security and
defense involves oceanborne transportation. The Joint Chiefs of Staff
estimate that for any major overseas deployment, 95 percent of all dry
cargo and 90 percent of all petroleum will move by sealift. The armed
forces appear to have given little attention to the security- and
defense-related aspects of port dredging in the United States and the
proposed alternatives (General Accounting Office, 1983~. Review of
these aspects is therefore somewhat speculative.
As noted in Chapter 4, some combatant vessels have greater depth
requirements than are now provided by the navigational channels they
use or propose to use. While operational flexibility (such as waiting
for high water, light-loading and one-way traffic) may be adequate to
ensure transit in many of these situations, it may not be adequate in
all situations. The same considerations may apply to the noncombatant
vessels used. If the capacity to accommodate vessels with greater
depth requirements is needed by some combination of combatant vessels
and those to be used for mobilization or the transport of strategic
materials, then new construction dredging of existing ports offers the
maximum contribution to national security and defense (the existence
of ports that are able to respond to all three needs broadens the
nation's capability to support these activities).
The possible contributions of offshore terminals is somewhat
equivocal: they may present a valuable option or an additional
vulnerability. They may also have no potential contribution, positive
or negative, depending on the commodities handled. New deepwater
ports, on the other hand, could offer the opportunity to include
defense facilities or features that might be difficult to achieve at
existing ports, but this is a contingent opportunity that has not been
addressed.
There seem to be few implications for national security or defense
from the introduction of large wide-beam vessels. Alternatively, the
flexibility of topping-off and lightering services could prove
important in moving strategic materials or petroleum.
Future Flexibility
As implied in preceding sections, new construction dredging of
existing multicommodity ports gives the nation the greatest future
flexibility among the options. Assuming that offshore terminals are
for single commodities, they offer little additional flexibility for
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the United States, and it might be argued that they increase the
nation's inflexibility. On the other hand, they are a proved
technology that can be provided to the pipeline infrastructure without
demands for space on the ports' waterfront, and this enhances
flexibility.
A new deepwater port could clearly add to the nation's future
flexibility, if it were planned as a multipurpose port handling a mix
of cargoes. Alternatively, if the deepwater port were primarily a
single-commodity port, it would offer less future flexibility than the
deepening of an existing multipurpose port. If the investment
required that the new port have a regional monopoly on port services,
however, future flexibility would clearly be reduced.
The contribution of wide-beam ships to future flexibility appears
minimal, since they do not seem to be competitive with deep-draft
vessels.
The lightering/topping-off option on the other hand, offers the
nation a short-term, low-cost response to handling large-volume bulk
carriers. It appears attractive where volumes of dry-bulk commodities
are sufficient to repay the investment. It is not likely to be
offered for certain commodities in particular circumstances, nor can
it substitute for additional channel depths to accommodate
containerships. This option contributes to present as well as future
capacity to accommodate large-volume vessels, but cannot be expected
to meet all the needs projected.
CONCLUSIONS
Of the five options for increasing the nation's capacity to handle
large vessels, measured against the criteria of economics,
navigational safety, environmental implications, national
security/defense needs, and future flexibility, two of the options
stand out as being the most attractive. That is, assuming the
conclusion drawn in Chapter 4 is correct that a prudent society can
ill afford to move into the future without the capacity to handle
large ships, then lightering/topping off and dredging existing ports
are clearly the most attractive two options.
This necessarily general judgment does not exclude any of the other
options, which may be attractive for some particular application now
or for very different circumstances in the future.
Lightering/topping-off is a developed and available technology that
is sufficiently flexible to meet short-term contingencies and serve
developing needs. Its short lead times allow the market to measure
its attractiveness.
Alternatively, new construction dredging of existing ports cannot
respond to short-term market changes. The lead times for new
construction dredging are long, and the short-term future uncertain.
The reason for developing at least a limited program of new
construction dredging in this country at existing ports is that
dredging offers the most secure response to an uncertain future. That
more secure future results from the fact that construction dredging
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puts the United States in a position to take advantage of the changes
in maritime transportation that have already occurred, those that can
be projected in the near term, and those that may occur.
Two optional categories of dredging to handle larger vessels can be
distinguished. One is dredging to accommodate vessels requiring 40 to
45 ft of water depth. The most frequently cited need is that of the
latest-generation containership, but there are many vessels in the
world fleet in this medium-size category, and the container ports that
handle a range of commodities could benefit from being able to
accommodate more and larger vessels of all types. The evidence
presented by several of the major ports in the United States and that
reviewed by the committee suggest that these are needs that exist
now. Given the heavy existing investment in cargo-handling facilities
in these ports, the well-established inland transportation systems
serving them, and the expectation that the quantity of cargoes carried
in medium-size vessels will increase, there is compelling reason to
assure that construction in this medium-depth range can be carried out
by the ports that can justify it.
The second category includes dredging to accommodate larger bulk
vessels requiring depths of 50 ft or 55 ft (or more). The committee
concludes that the prudent choice, given an unpredictable future, is
to ensure the nation has future flexibility. This conclusion does not
entail dredging all the proposed deep-water bulk-commodity projects
that have been put forward, nor does it suggest the number or order of
ports to be dredged to depths of 50 or 55 ft or more. The future
flexibility criterion does suggest that the nation should have a
minimum of deep-draft capability on each of the coasts.
Criteria Applicable to Selection
of Ports for Deep Construction Dredging
If, in the face of uncertainty, prudence suggests that additional
dredging of existing ports to achieve deep facilities is necessary,
what criteria might be used in establishing priorities for
construction dredging? Four criteria seem compelling. First, major
emphasis should be given to the ports with multicommodity
capabilities. Ideally then, selected ports should be capable of
handling all types of high-value cargo vessels ranging from
containerships through roll-on/roll-off ships, to break-bulk vessels.
Similarly they should include ports with facilities capable of
handling coal, hard minerals' grain, and oil.
Second, consideration should be given to the adequacy of the inland
transportation systems serving the ports. Two factors should be
considered here. First, the most attractive ports would be those that
serve a range of economic activities--manufacturing, agriculture,
mining--and the greatest numbers, in terms of population or markets.
Consideration should be given to the availability of alternative
inland transportation systems. The ideal would be a port which is
served by highways, multiple rail lines, and inland waterways. Where
there are alternative inland transportation options, competition
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offers the best prospect of keeping inland transport prices low. One
concern frequently expressed is that a deep-water port served by a
single inland transportation system might see that system increase
transportation costs to the point of cancelling the economic
advantages of using large ships.
The third criterion that should be considered is the comparative
cost of construction dredging and the additional maintenance dredging
costs that will have to be met annually (or at whatever the
maintenance dredging interval).
An important consideration in all port dredging decisions is the
potential effect on the environment. Thus, the fourth criterion for
selection among candidate ports for deep-draft dredging is minimizing
the potentially adverse environmental consequences.
REFERENCES
Aranow, P. I. (1983), "Maneuvering Response Supplemental Experiments
(Collier and Containerships)," CAORF Technical Report 42-8218-01,
National Maritime Research Center, Kings Point, N.Y.
Betram, K. M. (1982), "Alternatives to Deep-Draft Port Dredging for
U.S. Coal Export Development: A Preliminary Assessment," Report
No. ANL/EES-TM-183, Argonne National Laboratory, Argonne, Illinois.
Biggs et al. (1984), "Coal Transfer: Can an Environmentally Safe Coal
Transfer Operation Be Undertaken in The Lower Delaware Bayer
Report No. DEL-SG-01-84, University of Delaware Sea Grant Program,
Lewes, Delaware.
Chatagnier, G. (1983), "Midstream Mooring Facilities," Ports '83, K.
Wong, ed. (New York: American Society of Civil Engineers), pp.
402-414.
Dowd, J. P. (1983), Presentation to National Coal Association
Conference, New Orleans, September 19, 1983.
Eda, H. (1983), "Shiphandling Simulation Study During Preliminary
Ship Design," Proceedings, Fifth Annual CAORF Symposium, Kings
Point, N.Y., May 12-13, 1983.
Gaither, W. S. (1981), "A National Deepwater Port in Delaware," Marine
Policy Reports, _: 1-4 (University of Delaware, College of Marine
Studies).
General Accounting Office (1983), Observations Concerning Plans and
Programs To Assure the Continuity of Vital Wartime Movements
Through United States Ports (Washington, D.C.: Government Printing
Office).
Harris, A. J. (1983), "Marine Works for Bulk Loading," The Warren
Center, University of Sydney, Sydney, Australia.
Hydronautics, Inc. (1982), Advanced Technology U.S. Flag Bulk
Carriers, Report prepared for U.S. Maritime Administration (Laurel,
-
Md.: Hydronautics, Inc.~.
Landsburg, A. C. et al. (1983), "Design and Verification for Adequate
Ship Maneuverability, n Paper presented at Annual Meeting, Society
of Naval Architects and Marine Engineers, New York, November 9-12,
1983.
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58
Marine Board, National Research Council (1983), Ship Collisions with
Bridges: The Nature of the Accidents, Their Prevention and
l
Mitigation (Washington, D.C.:
National Academy Press).
Mitsubishi Heavy Industries, Ltd. (1974), "Ultra Shallow Draft Vessel."
Ono, M. et at. (1985), "The Design of Tankers for Restricted Draft
Service," Paper presented to STAR Symposium, Society of Naval
Architects and Marine Engineers, Norfolk, Va., May 21-24, 1985.
Permanent International Assembly of Navigation Congresses (1977),
"Report of the Japanese National Section," Proceedings of the 25th
International Navigation Congress, Leningrad, U.S.S.R.
Roseman, D. (1979), "Relative Costs of Alternative Modes of Ocean
Transport of Coal," Presentation to the Third International
Symposium, Transport and Handling of Minerals, Vancouver, Canada,
October 21-24, 197g.
Roseman, D. P. and R. A. Barr (1984), "Restricted Draft Geometry--
An Alternative to Dredging," Oceans '83 (Washington, D.C.: Marine
Technology Society and Institute of Electrical and Electronics
Engineers, Inc.~.
Roseman, D. P. et al. (1974), "Characteristics of Bulk Product
Carriers for Restricted Draft Service," Presentation to Annual
Meeting, Society of Naval Architects and Marine Engineers, New
York, November 14-16, 1974.
Soros Associates (1983), "Report on Offshore Materials Handling
Terminals," New York.
Sugin, L. (1972), "Alternatives in Port Terminal Layout--Dredging vs.
Offshore Terminal," Society of Mining Engineers of AIME, Preprint
72-B-68.
Wasp, E. J.
48-55.
(1983), "Slurry Pipelines," Scientific American, 249:
Representative terms from entire chapter:
existing ports
