Below is the uncorrected machine-read text of this chapter, intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text of each book. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.
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
41 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.
42 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
43 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.
44 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.
45 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.
46 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.
47 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
48 · 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
49 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
50 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.
51 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.
52 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.
53 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.
54 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
55 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
56 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
57 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.
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: