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Oil Spill Risks From Tank Vessel Lightering (1998)

Chapter: 2 Lightering Primer

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Suggested Citation:"2 Lightering Primer." National Research Council. 1998. Oil Spill Risks From Tank Vessel Lightering. Washington, DC: The National Academies Press. doi: 10.17226/6312.
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2
Lightering Primer

The solid safety record for lightering in the United States, which was documented in the previous chapter, does not suggest obvious avenues for risk reduction. Improving safety at the margins requires laying a foundation through a careful review of current lightering activity patterns, government regulations, industry standards, and operational procedures and equipment. This chapter summarizes the status and technical state of the art for lightering in the United States. The first section is an overview of U.S. lightering activity, including oil import patterns, types of vessels, and the nature of activities on each coast. The second section outlines the USCG regulatory regime for lightering and industry progress in setting standards. The third section describes the current lightering process in the United States.

Overview of U.S. Lightering Activity

Lightering takes place in the Gulf of Mexico and along the east and west coasts (see Figure 1-1). Approximately 60 percent of all U.S. oil imports are delivered through the Gulf of Mexico, and about 30 percent of the total comes through the LOOP and lightering areas (NRC, 1997). Most of this crude oil is imported from the Arabian Gulf, West Africa, the North Sea, and the Caribbean Basin (see Table 2-1). In addition, some refined petroleum products are imported from the Caribbean, Canada, and Europe and lightered (along with refined products from the U.S. Gulf of Mexico) on the East Coast. The committee could not locate any data on this trade, but the volume of products lightered is very small compared to the volume of imported crude oil lightered.

The numbers tell only part of the story. The characteristics of lightering activity, as well as public perceptions of it, vary by coast and by state. In Texas,

Suggested Citation:"2 Lightering Primer." National Research Council. 1998. Oil Spill Risks From Tank Vessel Lightering. Washington, DC: The National Academies Press. doi: 10.17226/6312.
×

TABLE 2-1 Sources of U.S. Crude Oil Imports Delivered by Offshore Lightering, 1994

Region

Barrels (millions)

Percentage

Arabian Gulf

351.5

59

Africa

112.8

19

Europe

64.3

11

Americas

61.2

10

Pacific

6.2

1

Total

596.0

100

 

Source: Maritime Administration Office of Statistical Analysis

for example, state officials recognize lightering as an integral part of the economy and invite industry to provide data and help develop lightering rules and regulations. Companies operating in the Gulf of Mexico have joined together through ITOL to develop lightering standards. On the East Coast, inshore lightering has been a common practice in Delaware Bay for many years, but offshore activities have developed only recently and tend to be more varied.

Lightering patterns in the United States are currently fairly stable (Figure 2-1). Oil imports to the United States have been rising steadily since the early 1980s and now total about 7.5 million barrels per day. The U.S. Department of Energy has projected an increase in U.S. oil consumption of 3.5 million barrels per day between 1994 and 2015 (Energy Information Administration, 1996). With more than half of U.S. demand now being met by foreign sources and most imported oil being delivered by water, the nation faces the prospect of a substantial increase in the waterborne oil trade (NRC, 1997). Lightering will undoubtedly continue to be a popular method of delivering imported oil, but predictions of future activity levels are based on considerable speculation.

Most lightering of imported oil takes place in either the Gulf of Mexico or Delaware Bay. Future imports to the Gulf of Mexico will most likely be lightered if they are carried by large tankers from distant sources, such as the Arabian Gulf or Africa. Because the proportion of long-haul versus short-haul imports is unlikely to change dramatically in the near future, the committee expects that lightering activity will remain fairly steady in the Gulf of Mexico in the near term. On the East Coast, lightering of refined products has increased in the recent past but still makes up a very small percentage of the total volume of lightered cargo. (This trade depends on the fluctuating margins between the cost of imports and the domestic supply.) East Coast oil refineries are now operating at nearly full capacity, and future increases are likely to be limited to improvements in efficiency because laws to protect air, water, and coastal zones will make the construction of new refineries cost prohibitive. Accordingly, the committee anticipates only small increases in lightering of crude oil on the East Coast in the near term. Trends on the West Coast are expected to have little impact on overall

Suggested Citation:"2 Lightering Primer." National Research Council. 1998. Oil Spill Risks From Tank Vessel Lightering. Washington, DC: The National Academies Press. doi: 10.17226/6312.
×

Figure 2-1

Crude oil deliveries to U.S. ports by lightering, 1986 to 1996. Notes: Offshore lightering of imported crude oil for the years 1986 to 1994 are from MARAD Office of Statistical Analysis. More than 95 percent of these offshore imports are lightered in the Gulf of Mexico. Because of data analysis problems in MARAD for the years 1995 and 1996, the numbers for those years are based on rough estimates by ITOL of offshore lightering activity in the Gulf of Mexico. Delaware Bay figures are from Maritrans Corporation's estimates for 1993 to 1996 (previous years are not available). San Francisco Bay figures (Alaskan crude oil) were derived from local USCG  estimates for 1993 to 1996 (previous years were not available).

lightering activity levels, given the very small volume of oil lightered there (see Table 1-2).1,2

The present study assumes that U.S. lightering activity will remain about the same as it is now. Nevertheless, preparing for the possibility that lightering activity will increase and that the industry will expand is only prudent.

1  

A substantial proportion of Alaskan oil is lightered in San Francisco Bay, but domestic production is likely to fall in the future. Oil imports may rise to compensate, but new lightering activity involving imported oil would take place offshore.

2  

The committee reviewed several projections of import patterns and concluded that none was conclusive enough about their effect on lightering to establish a consistent trend. Although imported oil is usually predicted to increase, whether that oil is lightered depends greatly on where it comes from (short hauls from South America would probably not be lightered, and oil from Mexico would be pipelined; oil from the Arabian Gulf or Africa would probably be lightered). In addition, the limits of U.S. refinery capacity will restrict the amounts of imported crude oil and possibly cause a shift to imported products, which would arrive by smaller vessels and would not be lightered.

Suggested Citation:"2 Lightering Primer." National Research Council. 1998. Oil Spill Risks From Tank Vessel Lightering. Washington, DC: The National Academies Press. doi: 10.17226/6312.
×

Vessels Involved in Lightering

Ships to be Lightered

Most of the crude oil imported into the Gulf of Mexico originates on continents thousands of miles away and is usually transported in very large crude carriers (VLCCs) of 165,000 to 360,000 deadweight tons (DWT)3 or ultralarge crude carriers (ULCCs) with capacities of up to 550,000 DWT. These tankers can be as large as 1,500 feet long and 225 feet wide, with a cargo capacity of 4 million barrels (168 million gallons). Ships of this size have deep drafts, extending as much as 90 feet below the water surface. Therefore, VLCCs and ULCCs cannot enter most U.S. ports, which typically have harbors and channels ranging from 30 to 40 feet deep. (The only U.S. port that these vessels can use is the offshore LOOP terminal. Another factor preventing their entry into U.S. ports is the sheer physical size and maneuvering characteristics of these large ships, which require ample time, broad channel widths, and turning basins.

The STBLs that supply the East Coast refineries are typically Suezmax vessels of 120,000 to 165,000 DWT (approximately 1 million barrels) or, in some cases, Aframax vessels of 80,000 to 105,000 DWT (approximately 650,000 barrels). When these vessels are fully loaded, their drafts exceed the maximum channel depths in the Delaware River (40 feet) or New York Harbor (40 feet or less, depending on the location in the port). Most of the crude oil arriving at these refining centers originates in West Africa. The remainder comes from the North Sea, the Mediterranean, or the Middle East.

Product carriers calling on East Coast ports are typically 50,000 DWT or less. Their voyages originate in the Gulf of Mexico, the Caribbean, Canada, or Europe. These vessels are lightered because of either port-specific draft restrictions or the economic advantages of lightering as opposed to having the vessel call at more than one port.

Service Vessels

Service vessels can be of several types. Vessels dedicated to the lightering trade spend the majority of their time shuttling between STBLs and terminals. Nothing restricts these vessels from participating, when lightering business is slow, in the more typical dock-to-dock transshipment of petroleum. Some dedicated vessels are owned by, or on long-term charter to, oil companies that attempt to provide a minimum level of secured lightering tonnage. Other dedicated vessels are available on a first-come, first-served basis (the "spot market") to meet

3  

Deadweight ton is a measure of a vessel's carrying capacity (the weight of cargo, fuel, fresh water, and stores).

Suggested Citation:"2 Lightering Primer." National Research Council. 1998. Oil Spill Risks From Tank Vessel Lightering. Washington, DC: The National Academies Press. doi: 10.17226/6312.
×

the needs of oil companies with excess chartered tonnage or oil companies or oil traders who prefer to deal on a trip-by-trip charter basis. Dedicated service vessels typically are permanently outfitted for lightering and have all the necessary equipment on board (e.g., fenders, mooring lines, deck equipment, and hoses), as well as the necessary personnel. Service vessels used in the Gulf of Mexico and on the West Coast are small enough to enter port areas, usually from 80,000 to 150,000 DWT (with a cargo capacity of 375,000 to 1.1 million barrels).

The majority of dedicated tug-barge units used in lightering operate along the East Coast. The capacity of dedicated tug-barge units ranges from 50,000 barrels to 400,000 barrels. Typically, units with capacities of more than 130,000 barrels are built as integrated tug-barge units, in which the tug and barge are attached with semi-rigid mechanical devices or a combination of a deep notch and soft-line or wire-tensioning system. Smaller units are designed so that the tug is connected to the barge by a series of soft lines or wires on the stern or alongside. These connections are very sensitive to sea conditions. If the seas get too rough, the tug must tow the barge. Typically smaller barges are used to lighter refined products, whereas larger vessels are used to lighter crude oil.

Vessels that are not permanently equipped with lightering equipment are sometimes known as all-purpose vessels. All-purpose vessels may be on long-term contract to provide lightering services, or they may be chartered for one or more voyages. They can be the same sizes and types as the vessels described above; but they must be supplied with the necessary equipment prior to a lightering operation. Fenders and hoses are usually brought to an offshore lightering location by a workboat, or the equipment is placed on board while the vessel is at a dock just prior to the voyage. When these vessels are not involved in lightering, they spend the majority of their time transporting petroleum from dock to dock.

The crews and officers aboard dedicated vessels are usually highly knowledgeable about lightering in general and their vessel's capabilities in particular. The officers and crews aboard all-purpose service vessels, which are used only for an occasional lift from an STBL, may not have in-depth knowledge of lightering operations. These vessels can still conduct lightering operations safely, as long as everyone involved is aware of the circumstances and procedures and plans accordingly. Lightering companies usually supplement the crews by placing an experienced lightering master aboard the service vessel and, frequently, an assistant lightering master aboard the STBL.

Workboats / Support Vessels

Many companies conducting offshore lightering operations enlist the assistance of a workboat, especially when using nondedicated service vessels. Workboats are typically 145 to 175 feet long and are used to transport lightering equipment. If service vessels are not built specifically for lightering, workboats

Suggested Citation:"2 Lightering Primer." National Research Council. 1998. Oil Spill Risks From Tank Vessel Lightering. Washington, DC: The National Academies Press. doi: 10.17226/6312.
×

bring out the necessary fenders and hoses. Some workboats used in lightering are also equipped with firefighting and oil pollution response equipment. Workboats that remain on station near a lightering operation can provide first response in the event of a spill while additional equipment is being mobilized and brought to the scene. Workboats can also be used as command platforms. Although workboats are not required by regulation or law, many shipping companies consider them safety nets for offshore lightering operations. The need for workboats is highly dependent on local conditions, specific characteristics of all vessels, and equipment and operational details. The committee considers that the Coast Guard captain of the port (COTP) oversight authority will assure prudent use of appropriate vessels.

Lightering in the Gulf of Mexico

Lightering activity in the U.S. Gulf of Mexico takes place in either designated lightering zones or traditional lightering areas (see Figure 2-2). STBLs can be at anchor, under way, or drifting, depending on weather and sea conditions. Service vessels used in the Gulf of Mexico are generally smaller tankers, in the 80,000 to 100,000 DWT range. Typically, STBLs lighter their entire cargoes because most of them are too large to enter port areas even after much of the cargo has been removed and their vessel drafts have been substantially reduced. Some of the smaller STBLs carrying crude oil from West Africa can enter port after one lift by a service vessel. Three lightering service companies4 conduct most of the operations in the Gulf of Mexico.

Nine areas have traditionally been used for lightering. Table 2-2 indicates the center point of each area. These traditional lightering areas, which can be many miles wide and long, are located away from the busy fairways or traffic separation schemes leading into port areas and away from large concentrations of offshore exploration and production platforms. Mariners who often navigate these waters have come to expect lightering operations in the traditional areas and can be expected to take appropriate precautions when approaching or transiting known lightering areas.

The USCG was authorized by OPA 90 to create designated lightering zones, where single-hull vessels are permitted to operate for a period of time. Until January 1, 2015, a tank vessel need not comply with the double-hull requirement if it is either ''(A) a vessel unloading in bulk at a deepwater port licensed under the Deepwater Port Act of 1974; or, (B) a delivering vessel that is offloading in lightering activities within a designated lightering zone established under title 46 USC section 3715(b)(5) and more than 60 miles from the baseline from which the territorial sea of the United States is measured.'' By using the designated

4  

The three companies are Skaugen PetroTrans, Inc., OMI Petrolink Corporation, and American Eagle Tankers, Inc.

Suggested Citation:"2 Lightering Primer." National Research Council. 1998. Oil Spill Risks From Tank Vessel Lightering. Washington, DC: The National Academies Press. doi: 10.17226/6312.
×

Figure 2-2

Designated lightering zones and prohibited areas in the Gulf of Mexico.

Suggested Citation:"2 Lightering Primer." National Research Council. 1998. Oil Spill Risks From Tank Vessel Lightering. Washington, DC: The National Academies Press. doi: 10.17226/6312.
×

TABLE 2-2 Traditional Lightering Areas in the U.S. Gulf of Mexico

Area

Latitude

Longitude

Sabine, Texas

28°–30°N

93°–40°W

Galveston, Texas

28°–27°N

94°–30°W

Galveston (#2), Texas

28°–40°N

94°–08°W

Freeport, Texas

28°–45°N

95°–03°W

Corpus Christi, Texas

27°–28°N

96°–49°W

Corpus Christi (#2), Texas

27°–48°N

95°–31°W

Houma, Louisiana

28°–27°N

90°–42°W

Pascagoula, Mississippi

29°–27°N

88°–13°W

Southwest Pass, Louisiana

28°–00°N

89°–30°W

lightering zones, single-hull tank vessels contracted for after June 30, 1990, and older single-hull tank vessels phased out under OPA 90, will be able to lighter until 2015.5 At the time these rules were made, approximately 20 new vessels meeting this definition were identified by the USCG that might trade to the U.S. Gulf of Mexico and engage in lightering to offload cargo. Because the International Convention for the Prevention of Pollution from Ships (MARPOL Convention) prohibits, as of July 1993, contracting for the construction of single-hull tankers used in international commerce, no more single-hull tankers will be built. The intent of allowing single-hull tankers to continue to lighter in designated areas was to ensure adequate oil supplies in the United States while double-hull tank vessels were being built and placed in service.

The four lightering zones shown in Figure 2-2 were formally designated by federal regulation (46 USC 1503[b][5]) on August 29, 1995. These are the only lightering zones currently designated by national regulation, although other regulated areas can be (and are) designated at the USCG district level.6

Lightering on the East Coast

Most lightering along the East Coast takes place in protected and semi-protected coastal areas, primarily Big Stone Anchorage in Delaware Bay and, to

5  

Single-hull tank vessels contracted for after June 30, 1990, are prohibited from conducting lightering operations anywhere (other than the designated zones) in the U.S. Gulf of Mexico, unless they are more than 200 miles offshore, outside the U.S. Exclusive Economic Zone (EEZ). The prohibition on operations inside the EEZ raises concerns that lightering operations might simply move farther offshore into international waters where the U.S. has no jurisdiction.

6  

The Coast Guard COTP can use his general authority to designate anchorages or regulated navigational areas with respect to lightering within U.S. waters. For example, this has been done in Long Island Sound, Delaware Bay, and San Francisco Bay. When a vessel provides the required advance notice of lightering to the COTP, he can require that the vessel use a specified area before giving permission.

Suggested Citation:"2 Lightering Primer." National Research Council. 1998. Oil Spill Risks From Tank Vessel Lightering. Washington, DC: The National Academies Press. doi: 10.17226/6312.
×

some extent, in Long Island Sound, New York Harbor, and Boston Harbor. Lightering activity is concentrated inshore (see Table 1–2),7 which influences the types of vessels used. Under federal law, petroleum imports that are lightered within U.S. territorial waters must be transferred to U.S.-flag service vessels (OTA, 1989), which are subject to different standards and regulations than vessels engaged in offshore lightering (see section on government and industry controls below).

In these inshore areas, the STBL is always at anchor, and barges or integrated tug-barge units are usually used to transport cargo to the discharge berth. Vessels lightering in semiprotected areas can be subjected to weather anomalies, such as high seas, swells, currents, and winds. The weather is less of an issue in protected bays, harbors, and sounds. The STBLs used in crude oil lightering are generally smaller than those used in the Gulf of Mexico, typically carrying about 1 million barrels of oil. In some instances, after a few lifts by service vessels, the draft of the STBL is sufficiently reduced for it to move to the dock and directly offload the remaining cargo.

Refined products (i.e., gasoline, jet fuel, and diesel fuel) are lightered in Long Island Sound and various East Coast harbors. The STBLs are typically 30,000 to 50,000 DWT tankers originating at refineries in the Caribbean, the Gulf of Mexico, Canada, or Europe. In these cases, lightering is performed either because the vessel's draft is too deep to enter the destination port directly or because the product is destined for two or more terminals, and it is more economical to lighter the parcels than to make multiple port calls.

Offshore lightering is conducted off Montauk Point, New York; Cape Henlopen, Delaware; Cape Henry, Virginia; and Great Issacs, Bahamas. Lightering is conducted off Great Issacs when an STBL carries cargo that needs to be delivered at both East Coast and Gulf Coast refineries or when the weather off Cape Henry is not conducive to lightering operations. Offshore lightering on the East Coast is subject to different weather and wave conditions than those found along the other U.S. coasts. Along the East Coast, storms and rough seas are more prevalent in the winter, spring, and fall seasons than in the Gulf of Mexico, but the large swells that occur offshore in the Pacific (off the West Coast) are not as prevalent along the Atlantic coast.

In most East Coast locations where lightering takes place, the local USCG COTP has substantial control over lightering operations. A COTP has the authority to establish certain rules and regulations within the territorial sea under the Ports and Waterways Safety Act (33 USC section 1221 et seq.). Notification is required prior to a lightering operation (33 CFR 156.215). A COTP can also designate a lightering anchorage (46 USC section 3715), as COTPs have done in Stapleton in New York Harbor, and President Roads in Rhode Island. Another

7  

Maritrans handles most of the lightering on the East Coast; Skaugen is beginning to provide offshore lightering services here as well.

Suggested Citation:"2 Lightering Primer." National Research Council. 1998. Oil Spill Risks From Tank Vessel Lightering. Washington, DC: The National Academies Press. doi: 10.17226/6312.
×

approach is to establish a regulated navigation area (33 CFR 165) within the territorial sea, such as Big Stone Anchorage in Delaware Bay. Recently, the COTP in Long Island Sound proposed that the USCG district commander establish five regulated navigation areas in waters that are currently used for lightering. The areas were recommended initially by a stakeholder group composed of industry representatives and other waterway users. The areas were reviewed by the USCG based on environmental protection and traffic safety criteria. The regulated navigation areas would be designated through a rule-making process to formalize the applicable federal regulations (personal communication from Capt. Peter Mitchell, December 15, 1997). An overview of government and industry controls on lightering is provided later in this chapter.

Lightering on the West Coast

Substantial lightering takes place in only two locations on the West Coast: in San Francisco Bay and about 140 miles off San Diego. Small amounts of petroleum are also lightered in Puget Sound and in Los Angeles/Long Beach harbor, but not on a regular basis. In the past, some lightering was done offshore near Los Angeles (inside the Channel Islands), but this practice has been discontinued.

In San Francisco Bay, most of the lightering involves shipments of crude oil from Valdez, Alaska, to the refineries in the San Francisco Bay area.8 The protected area offers some shelter from weather conditions. Typically, tankers of about 150,000 DWT anchor in a designated area (Anchorage #9) just south of the Bay Bridge and discharge cargo into barges and other vessels, which then navigate a shallow channel to the north (with draft restrictions of about 35 feet) to deliver the cargo to refineries. Lightering is one of the most cost-effective ways of bringing Alaskan oil to these refineries. Only one major refinery in the region is located along channels deep enough9 to allow large Alaskan trade tankers to dock.

The lightering activity off San Diego began in 1996. Chevron Shipping Company, the only company now operating in this region, uses lightering to bring crude oil from the Middle East and the Far East to refineries in the Los Angeles and San Francisco areas.10 The typical STBL is a VLCC of about 300,000 DWT that lighters into service vessels of about 150,000 DWT, which then deliver crude oil to Chevron refineries. These operations take place in unprotected waters where weather conditions can be more severe than in most other U.S. locations where

8  

One company, SeaRiver Maritime, conducts more than 80 percent of the lightering in San Francisco Bay; the rest is performed by approximately six smaller companies.

9  

These channels are still only 39 feet deep, and most vessels have to either wait for high tide or offload some cargo before going in.

10  

The state of California has commented on the Chevron operations (see Appendix F) even though they take place beyond state jurisdiction. The Coast Guard monitors this offshore lightering, as it does in the Gulf of Mexico.

Suggested Citation:"2 Lightering Primer." National Research Council. 1998. Oil Spill Risks From Tank Vessel Lightering. Washington, DC: The National Academies Press. doi: 10.17226/6312.
×

lightering now takes place. Accordingly, Chevron is developing special (more rugged) equipment and procedures to accommodate severe weather. The company uses dedicated service vessels and has tested and trained crews specifically for these operations.

California officials and local environmental groups monitor West Coast lightering operations, and, impressed by the good safety record to date and by industry's cooperation in information sharing, they did not express serious concerns about the risk of spills from lightering. In the future, lightering activity levels are expected to remain stable unless and until there are major changes in the Alaskan oil supply. Some have predicted a decline in Alaskan crude oil production in the next several years; if this occurs, then more foreign crude oil will be imported to supply West Coast refineries. An increase in imports could lead to more lightering because foreign oil would most likely be delivered in VLCCs and would have to be lightered to smaller service vessels offshore. Other changes in crude supply patterns, such as an increase in deliveries from South America, could have similar effects.

Government and Industry Controls

The only federal agency that oversees lightering operations beyond the territorial seas is the USCG, whose role varies depending on the geographical location of the lightering operation. The USCG exerts maximum control over lightering within the territorial sea, where all service vessels must be U.S.-flag vessels, constructed in a U.S. shipyard, and crewed by U.S. citizens. Lightering outside the territorial sea can be performed by foreign-flag vessels built overseas that employ foreign crews.

In either case, the USCG exerts varying control over lightering through six general mechanisms: vessel design requirements (established by the United States Code, OPA 90, and international agreement)11 ; operational procedures (established by the United States Code, OPA 9012 and international agreement)13; personnel qualifications; oil spill contingency planning and equipment requirements; vessel inspection; and monitoring. The USCG role in these areas is outlined

11  

This agreement is the MARPOL Convention, which is the 1978 Protocol of the International Convention for the Prevention of Pollution from Ships (1973). The MARPOL Convention is one of many conventions adopted by the International Maritime Organization (IMO), the United Nations agency responsible for maritime safety and protection of the marine environment. All of the world's major shipping nations are members of IMO.

12  

For example, one regulation promulgated under OPA 90 requires vessel masters of single-hull tankers to calculate the underkeel clearance based on the vessel's draft and other conditions prior to entering port, but there is no established minimum clearance (33 CFR Part 157.455).

13  

This agreement is the International Convention on Standards of Training, Certification, and Watchkeeping for Seafarers (known as STCW), which is discussed further in Chapter 4.

Suggested Citation:"2 Lightering Primer." National Research Council. 1998. Oil Spill Risks From Tank Vessel Lightering. Washington, DC: The National Academies Press. doi: 10.17226/6312.
×

briefly below. The relevant vessel design issues, equipment requirements, and personnel qualifications are addressed in more detail in chapters 3 and 4.

There are two sets of basic USCG regulations: one for navigable waters and contiguous zones (i.e., inshore areas) and one for offshore areas. The specialized USCG lightering zone regulations (33 CFR Part 156 Subpart C) apply only to the four designated offshore lightering zones in the Gulf of Mexico (the regulations are provided as Appendix G). Elsewhere, lightering is performed at the discretion of the local COTP within the parameters of the applicable basic lightering regulations and other applicable laws. Table 2–3 outlines the various regimes for USCG control of lightering operations.

All STBLs conducting operations within the U.S. EEZ, a 200-mile-wide band around the coastline, must notify the nearest COTP more than 24 hours prior to the vessel's arrival. This applies to operations in both designated lightering zones and traditional lightering areas. The vessel notifies the USCG of both intent to lighter and the proposed location, and the COTP grants permission subject to certain guidelines and standards. Various areas (e.g., Big Stone Anchorage in the Delaware River and Graves End Bay and Stapleton Anchorage in New York Harbor) have been designated as lightering anchorages in which standard operating procedures must be followed. The regulations may be suspended when lightering is carried out during emergency salvage operations.

For vessels lightering in a U.S. coastal region within 200 miles, a number of international and national regulations apply. For example, both the STBL and service vessel must have a U.S. certificate of financial responsibility (COFR) and the minimum level of liability insurance established by OPA 90. The vessel owner, not the cargo owner, is liable for any spills. Both vessels must also have on board USCG-approved spill-response plans that identify procedures, equipment, and personnel available to respond to an oil spill (see Box 2-1). All U.S.-

TABLE 2-3 Regimes for U.S. Coast Guard Control of Lightering Operations

Geographical Area

Designator

Location

Type of Control

Designated lightering zones

U.S. Coast Guard

Gulf of Mexico

Special federal regulations

Traditional lightering areas

Local shipping industry

Various offshore areas on all coasts

Federal regulations for offshore activity

Lightering anchorages

Captain of the port (U.S. Coast Guard District)

Delaware Bay, New York Harbor, San Francisco Bay, et at.

Federal regulations for inshore transfers

Regulated navigation areas

Captain of the port (U.S. Coast Guard District)

Long Island Sound, Delaware Bay

Established by captain of the port

Outside U.S. Exclusive Economic Zone (EEZ)

U.S. Congress designates the EEZ

More than 200 miles off all U.S. coasts

No U.S. Coast Guard control

Suggested Citation:"2 Lightering Primer." National Research Council. 1998. Oil Spill Risks From Tank Vessel Lightering. Washington, DC: The National Academies Press. doi: 10.17226/6312.
×

BOX 2-1 Requirements for Spill Response Plans

The OPA 90 Required the development of regulations for response capabilities for oil spills. The USCG established regulations (33 CFR Part 155 Subpart D-Response Plans) accordingly. As of 1995, all vessels engaging in lightering operations within the EEZ, when the cargo lightered is destined for a port or place subject to the jurisdiction of the United States, must have a USCG-approved response plan. The plans must identify the personnel and equipment, secured by contract or other approved means, that would be used in the event of an oil spill,as well as certain shipboard requirements of personnel training, equipment, and drills.

The regulations also specify response times and amounts of equipment and oil-recovery capacities, depending on the location, size, and type of oil spilled. For Example, the lowest planning standard (for the "average most probable" spill) is defined as "a discharge of 50 barrels of oil from the vessel during a transfer operation." All vessels transferring oil within 12 miles of land must have the capability to deploy a "containment boom in a quantity equal to twice the length of the largest vessel involved in the transfer and capable of being deployed at the site of the oil transfer operation within one hour of detection of a spill; and oil recovery devices and recovered-oil storage capacity capable of being at the transfer area within two hours of the detection of a spill during the transfer operation.''

A waiver granted by USCG commandant established an alternative planning standard for vessels engaged in lightering operations more than 12 miles from shore. This planning requirement allows one hour for mobilization of equipment and a planned transit speed of 5 knots of the site of the transfer operation.

flag vessels must have a certificate of inspection. Foreign tank vessels must have a valid tank vessel examination letter (TVEL) issued by the Coast Guard. All vessels must comply with all USCG regulations covering the operation of tank vessels.

Vessels engaged in lightering in the territorial sea are required to abide by all regulations pertaining to the transfer of oil. These regulations address several parameters, such as who is in charge, discharge cleanup, the connection of transfer hoses, and equipment tests and inspections. Prior to a transfer, both vessels must complete a Declaration of Inspection (DOI) (46 CFR 35.35–30) and are subject to all of the applicable provisions (in 46 CFR Subchapter D—Tank Vessels and 33 CFR Subchapter O—Pollution). The DOI requires that the individuals in charge of a petroleum transfer attest to their compliance with a predetermined set of regulations. A DOI is also required for offshore lightering (33 CFR Part 156.210).

Suggested Citation:"2 Lightering Primer." National Research Council. 1998. Oil Spill Risks From Tank Vessel Lightering. Washington, DC: The National Academies Press. doi: 10.17226/6312.
×

Most vessels involved in offshore lightering are foreign-flag vessels (OTA, 1989) because they are less expensive and more readily available than U.S.-flag vessels and, under the law, can be used for lightering offshore. Between the territorial sea and the 200-mile limit of the EEZ, the USCG's primary tool for ensuring safety is the requirement that foreign-flag vessels engaged in lightering have a current TVEL certifying that the USCG has inspected the vessel to international standards and certain U.S. tanker requirements within the last 12 months. If the TVEL is not current, then the USCG must conduct an inspection before lightering begins.

The designated lightering zones in the Gulf of Mexico provide the USCG with some additional enforcement tools in those areas. For example, the regulations describe the weather conditions in which lightering can be performed and specify the maximum operating conditions, work hours, and operational parameters for vessels engaged in lightering in the designated areas. Although these regulations do not apply to traditional lightering areas, most vessels operating in those areas voluntarily follow the regulations for designated zones. Furthermore, most ITOL guidelines for operational parameters are stricter than the regulations.

As a further safety check in the Gulf of Mexico, the USCG engages in periodic surveillance of lightering areas. Approximately three to four times a week, air crews stationed in Corpus Christi, Texas, fly over lightering areas. Sometimes they have a specific mission, but usually they just observe whatever vessels happen to be in the lightering areas. Anecdotal reports suggest that USCG personnel sometimes observe lightering operations on other coasts.

The shipping industry has implemented lightering safety measures in several stages. In the early 1970s, large fenders and special mooring arrangements were evaluated and adopted (NRC, 1991). The procedures for maneuvering vessels, mooring, and handling cargo were developed by the OCIMF (Oil Companies International Marine Forum), an oil industry association, and codified in Ship to Ship Transfer Guide, first published in 1978 and now in its third edition (ICS and OCIMF, 1997). These guidelines are for offshore lightering between tankers only. There are no specific lightering guidelines or standards specifically for inshore lightering, which often involves barges, although the American Waterways Operators promotes general safety standards and practices for inland vessels (see Chapter 4). Many inshore operators follow the international guidelines. The committee considers the international guidelines to be sufficiently stringent for general application, and the guidelines also encourage specific enhancements under special conditions that warrant them.

In the late 1980s, the COTP in Houston became concerned about lightering activities in the Gulf of Mexico, which led to the establishment of ITOL in 1990. ITOL is a mechanism for the consensus-based development of industry standards, and among its accomplishments, is the publication of a supplement to the international guidelines on lightering operations (ITOL, 1990). In addition, some major oil companies and independent oil transport companies have established

Suggested Citation:"2 Lightering Primer." National Research Council. 1998. Oil Spill Risks From Tank Vessel Lightering. Washington, DC: The National Academies Press. doi: 10.17226/6312.
×

their own lightering procedures, which are generally more stringent than the international guidelines.

The Lightering Process

The crude oil lightering process is initially set in motion by a refinery's capabilities to refine certain types of crude oils, which are distinguished by their source and characteristics. The refinery's capabilities determine where the oil will be shipped. For example, a refinery designed to run a light, sweet crude oil14 would probably get it from the Arabian Gulf rather than from Mexico. The supply planners attempt to make 30-to-60-day projections of the product lines to be run, based on the demand, season, and refinery capability. The projections dictate not only the source of the oil but also the amount needed. Product availability and economics also affect the final determination of the source and cost of the oil, as well as the transport costs and the spot deals possible on the open market. Existing contracts and agreements for delivering a certain number of barrels per month may also affect the source of the oil.

Once the refinery plans are established, the traders working under established agreements or on the open market purchase the necessary "raw material barrels." The traders begin with the projected dates on which the oil will be needed at the refinery and calculate back to an estimated transportation date. Then, based on the traders' purchases, the vessels needed to transport the oil are secured by the traders. These vessels are either managed by the oil company or are chartered for a specific voyage or for a predetermined length of time (independent of the number of trips). The types of companies that provide lightering services are described in Box 2-2.

Refined products are typically imported by oil companies or traders either when the domestic supply can not meet the demand or when the margin is better on the imported product even after shipment costs are added. Lightering of petroleum products almost always takes place inshore, typically using a tug-barge unit as the service vessel. The STBL can be either a tanker or a large tank barge.

The lightering process can be divided into the approach, transfer, and post-transfer (or departure) phases. The approach phase includes the rendezvous in the lightering area or zone, the maneuvering of the STBL (if not already at anchor) and service vessel alongside each other, the mooring of the two vessels, and (if necessary or desirable) the anchoring of the STBL. The transfer phase includes the completion of required paperwork, the connection of hoses, the pumping and transfer of cargo, and the inspection and certification of cargo. The post-transfer phase includes operations associated with the unmooring and departure of the service vessel. In certain areas (e.g., the designated lightering zones), the approach distances, wave heights, weather conditions, and other factors are

14  

A light, sweet crude oil is a low-density, low-viscosity oil with a low sulfur content.

Suggested Citation:"2 Lightering Primer." National Research Council. 1998. Oil Spill Risks From Tank Vessel Lightering. Washington, DC: The National Academies Press. doi: 10.17226/6312.
×

BOX 2-2 Companies That Provide Lightering Services

Service companies can provide any or all lightering equipment and personnel. When hired to support lightering operations, service companies usually provide the full range of services because this is the most economical arrangement for the customer.

Some of the larger oil companies retain one or more service vessels on permanent charter to service STBLs on a regular basis, supplemented by additional chartered service vessels as necessary. The oil companies usually scrutinize every aspect of a lightering operation very carefully and, if incidents occur, they act quickly to ensure that they do not happen again. They may stop doing business with a poor performer.

One major oil company owns and uses two dedicated tankers to service STBLs carrying oil to its refinery. The company uses it own staff mooring and lightering masters when necessary.

spelled out, but in general there are no specific federal regulations governing the approach, mooring, unmooring, and coming off procedures (other than specified approach distances and transition positions). The best practices for offshore lightering have been established by the OCIMF (ICS and OCIMF, 1997). An annotated timeline for the overall oil transportation and lightering process is provided in Chapter 4 (Box 4-1 and Figure 4-1).

Approach Phase

Offshore Operations

The approach phase begins when the service vessel proceeds to the general area where the STBL is waiting. Communications are established and maintained throughout the operation among the vessel masters, the mooring (or lightering) master, and the assistant mooring master, if present. (The personnel involved in lightering operations are described in Box 2-3.) By tradition and custom, everyone involved in the approach phase must agree that the conditions, vessels, equipment, and personnel are prepared and adequate for a safe operation; otherwise, the process comes to a halt until the problems are resolved. Several OCIMF safety checklists (copies are provided in Appendix H) are then completed before any close-quarters maneuvering is done to ensure that both vessels comply with international guidelines and company policies. Prior to inshore lightering, a DOI must be filled out and transmitted to the COTP. The committee considers that the safety checklists under the 1997 guidelines and the current lightering zone regulations noted in Box 1-3 have adequately addressed the problems of ''limited communications."

Suggested Citation:"2 Lightering Primer." National Research Council. 1998. Oil Spill Risks From Tank Vessel Lightering. Washington, DC: The National Academies Press. doi: 10.17226/6312.
×

BOX 2–3 Personnel Involved in Lightering Operations

Vessel masters: The masters of the STBL and service vessel retain ultimate authority over their vessels during the entire operation, even when a mooring and lightering master are on board to assist with the operation. Depending on a vessel's typical route, the master may or may not be familiar with lightering procedures. A service vessel owned by a company that provides lightering services may have a master who is very familiar with lightering. Masters of STBLs that are regularly chartered for lightering operations usually are somewhat familiar with the operation

Mooring master of lightering master: A mooring master (or lightering master) is an experienced, senior officer placed on board the service vessel to coordinate and assist in directing the entire lightering operation, from the first communications during the approach phase to the coming off process. The mooring master is especially valuable for monitoring weather conditions, assisting with navigation, and ensuring a safe operation.

Assistant mooring master: Sometimes an assistant mooring master is placed a board the STBL to ensure that the mooring master's directions are followed and to assist the crew. This individual could be a mooring master in training.

Cargo mate, chief mate, or chief officer: One or more persons are on board both the STBL and service vessel to ensure the safe loading and discharge of cargo within the specified parameters of stress, trim and stability.

Workboat master: A workboat is responsible for transferring fenders and hoses and usually remains in the lightering area during the entire operation. A workboat often heads off small boat traffic that might interfere with the operation and may also provide support for responding to oil spills, if necessary.

Officers and crews of STBL, service vessel, and workboat: The crews perform various duties, such as handling the lines that moor the two vessels together, standing watch on deck to ensure that cargo is transferred smoothly, providing navigation watches, and ensuring that the engines are ready for maneuvering.

During lightering operations, the service vessel is usually moored to the starboard side of the STBL. Before the vessels begin to maneuver to come alongside, a string of four fenders is rigged on either the starboard side of the STBL or on the service vessel (the industry-recommended approach). The rubber fenders, ranging in size from 3 by 6 feet to 15 by 30 feet, are filled with either air or foam. Primary fenders, typically of the larger size, float on the water surface to cushion the impact as the two vessels are brought together. These fenders must remain

Suggested Citation:"2 Lightering Primer." National Research Council. 1998. Oil Spill Risks From Tank Vessel Lightering. Washington, DC: The National Academies Press. doi: 10.17226/6312.
×

afloat throughout the entire operation to prevent their riding up the sides of the vessels and rolling onto the deck. Smaller secondary fenders (also called baby fenders) are used, as necessary, on either the STBL or service vessel to prevent unexpected bow or stern contact during mooring or unmooring. The fenders are brought out to the STBL by either the service vessel or a workboat.

When the vessels are approximately 25 to 30 feet apart, the crews begin passing mooring lines between them to make them fast to one another. As the two vessels come closer together, the mooring master must pay special attention to the hydrodynamic effects that tend to move the bow of the service vessel away from the STBL; therefore, the first lines out are the forward spring lines. The head lines follow shortly thereafter. Once these critical lines are out, a full complement of after-spring lines and stem lines is put out.

When the lines are almost fast, the mooring master begins to reduce the speed of both vessels simultaneously. If the lightering operation is to take place at anchor, then the service vessel's speed is gradually reduced to zero, essentially making it a towed vessel. The STBL proceeds slowly to the chosen anchorage, and the anchor is dropped. If the two vessels are to drift with the winds and currents, then the speed of both is reduced to zero. The third option is to lighter while the STBL steams at a very slow speed and the service vessel is towed alongside. The selection of one of these three alternatives depends on several variables, such as water depth, weather conditions, sea states, the area available for steaming, and the draft of the STBL. In all cases, the mooring master, or lightering master, and masters and crews of both vessels must maintain diligent navigational watches as long as the vessels are together to ensure the safety of the crews and vessels. Support vessels, such as workboats, may remain in the area to assist in the lightering operation or warn other vessels in the vicinity.

Inshore Operations Using a Tug-Barge Unit as the Service Vessel

The approach phase of an inshore lightering operation, in which a tug-barge unit is typically used as the service vessel, differs in certain respects from the initial phase of an offshore operation. First, the STBL is always at anchor when lightering takes place. Second, the interplay of a number of factors that affect how the STBL acts on its anchor must be considered prior to the approach. The approach phase begins only after the service vessel personnel have considered the wind direction; speed, direction, and time of a change in a tidal or seasonal current; vessel traffic conditions; and anchorage congestion. Third, barges are typically equipped with permanent lightering fenders, which are lowered out of fender slides and into the water prior to coming alongside the STBL. The side of the barge that berths alongside the STBL depends on how the barge is outfitted and which side provides the best shelter from the wind. Most barges are also permanently equipped with the necessary hoses and mooring lines, eliminating the need for a workboat. Fourth, mooring masters are not typically employed by the tug-

Suggested Citation:"2 Lightering Primer." National Research Council. 1998. Oil Spill Risks From Tank Vessel Lightering. Washington, DC: The National Academies Press. doi: 10.17226/6312.
×

barge service vessels. Rather, the tug master is responsible for directing the vessel and is assigned to the unit on the basis of proven expertise in handling vessels. Many companies that operate service vessels employ a lightering coordinator, who is stationed on the STBL. This individual's role is similar to the role of an assistant mooring master.

Transfer Phase

Offshore Operations

In preparing for the transfer of oil, pretransfer checklists and a DOI must be completed to ensure that the crews and officers of both vessels understand the amount of cargo to be transferred, transfer rates, and the expected duration of the cargo transfer. The checklists and DOI also help ensure that customary safety precautions have been taken aboard both vessels, that communications have been established between the cargo officers of both vessels, and that contingency plans have been made in case cargo is spilled.

While the checklists and DOI are being reviewed by the cargo officers, the crews hook up the transfer cargo hoses to each vessel's cargo manifold. These hoses, usually supplied by the service vessel or workboat, are constructed to withstand the pressures and transfer rates of cargo discharge. If the service vessel is equipped specifically for lightering, then the hoses are stored on board on a special mechanical arm that can span the distance between the two vessels. If the hoses are supplied by a workboat, then it comes alongside the STBL, which uses its cargo crane to lift the hoses aboard before mooring. Generally two hose strings, sets of three interconnected hoses amounting to 90 feet of hose, are used to transfer the cargo. Once the hoses have been connected and the checklists completed, cargo transfer begins.

Cargo transfer and crew communication during lightering are much the same as they are at a berth (OCIMF, 1995). The STBL starts its cargo pumps slowly as the integrity of the systems aboard both vessels is checked and rechecked. The rate of transfer is increased slowly to the maximum discharge rate. Transfer continues at this rate until the cargo tanks on the service vessel are almost full. The rate of transfer is then slowly reduced until the designated fill point is reached. The transfer is stopped when the last cargo tank on the service vessel has been topped off.

After the cargo transfer is completed, the cargo hoses are drained and disconnected from one vessel's manifold (generally the STBL). While still connected to the service vessel's manifold, the hoses are suspended vertically by a crane, so that remaining cargo runs into that vessel's tanks. (Hoses may be drained into either vessel, depending on whether a flow boom or ordinary hose rig is used, but it is preferable to drain any remaining cargo into the receiving vessel to maximize the amount offloaded.) The hoses are then capped and either draped over the side

Suggested Citation:"2 Lightering Primer." National Research Council. 1998. Oil Spill Risks From Tank Vessel Lightering. Washington, DC: The National Academies Press. doi: 10.17226/6312.
×

of the STBL or, if all lifts have been completed, laid on the deck in preparation for unmooring.

Inshore Operations Using a Tug-Barge Unit as the Service Vessel

An additional step is taken during the transfer phase of an inshore lightering operation. Prior to the transfer of any cargo from a vessel engaged in an international voyage to a U.S.-flag vessel engaged in a domestic voyage inside U.S. Customs waters (12 miles from shore), the STBL must undergo a customs inspection and clearance procedure. If the transfer occurs more than 12 miles offshore, and the STBL has not cleared customs, then the service vessel has completed a foreign voyage and must undergo inspection and a customs clearance process when it reenters U.S. Customs waters. As with offshore lightering a DOI must be completed prior to any petroleum transfer within the territorial sea.

Post-Transfer Phase

Offshore Operations

Cargo inspection, or gauging, is either performed while the hoses are being drained and disconnected or is delayed until the service vessel reaches its destination. Often the process is carried out at both points. At least one gauging is necessary to determine the amount of cargo transferred, ensure that each party receives the amount of cargo contracted for, and confirm that no excess cargo has been inadvertently left aboard the STBL. The cargo inspectors work on behalf of the chartering and purchasing organizations.

Some experienced mariners question the need for cargo inspections at sea, which can take more than two hours and can pose a safety risk in adverse or deteriorating weather conditions, when the mooring master is anxious to separate the vessels. Moreover, if at-sea cargo gauging takes place while the service vessel is moving in the seaway because of wind and sea conditions, the calculations of cargo levels will only be approximate. A more accurate figure can be obtained when the service vessel reaches port. One way to deal with these concerns would be to limit at-sea cargo gauging to the STBL and to begin the process only after the departure of the service vessel. Cargo levels on the service vessel can be measured at the destination port and transmitted to the STBL for record-keeping purposes. (This approach is already the norm for inshore lightering when tug-barge units are used as service vessels.) If there were concerns about possible irregularities, then a surveyor could ride the service vessel and use other methods to make initial estimates of the volume of cargo transferred.

Once the necessary cargo gauging has been performed, the mooring master or lightering master and the masters of the two vessels discuss the unmooring process, and, when all agree, the maneuver proceeds. The same level of care

Suggested Citation:"2 Lightering Primer." National Research Council. 1998. Oil Spill Risks From Tank Vessel Lightering. Washington, DC: The National Academies Press. doi: 10.17226/6312.
×

must be taken during unmooring and coming off as is taken when the vessels are brought together and moored. One final checklist is completed, and any necessary adjustments are made to facilitate coming off.

The mooring lines are let go in a predetermined order, and the vessels are separated very slowly. If the STBL is at anchor, then she may remain at anchor while the service vessel maneuvers. As the distance between the vessels grows, the speed and angle of departure of the service vessel can be increased. Finally, the service vessel proceeds to the discharge port and berth.

If the STBL expects another service vessel, then the crew proceeds with any cargo consolidations, crude oil washing, ballasting, or other activities required before the next lift. If no more lifts are expected, then the cargo hoses are disconnected and capped and, along with the fenders, are either collected by the service vessel or lowered to a workboat that comes alongside. The STBL then proceeds either to the next load port or to a destination port to discharge the remaining cargo.

Cargo Delivery to Shore Facilities

Following the lightering operation, the service vessel proceeds to a crude oil terminal ashore. There are 163 refineries located in the United States, many of them with either direct access or pipeline access to the sea, allowing the facility to operate with imported crude oil.

The states bordering the Gulf of Mexico account for 44 percent of all U.S. refining capacity. Galveston Bay and the Mississippi River have 11 percent of refining capacity each. Four major pipelines that supply inland refineries are located in the western Gulf of Mexico (Capline at St. James, Louisiana; Arco Pipeline at Texas City, Texas; Seaway Pipeline at Freeport, Texas; and Mobil Pipeline at Port Arthur, Texas). Other areas in which lightering takes place include Delaware Bay, with 6 percent of U.S. refining capacity, San Francisco with 5 percent, and Los Angeles with 5 percent (Oil and Gas Journal Data Book, 1998).

The port operations for a tanker mirror the lightering process in that they have an approach phase, a transfer phase, and a post-transfer phase. The vessel has to consider many factors, including port restrictions, such as draft, length, and beam. USCG regulations require the ship's master to compute underkeel clearance before entering port.

The approach phase includes maneuvering into the port area to pick up a pilot. This may well be the most dangerous time for a ship in the entire passage. Traffic, water depths, and excessive background lights are among the problems vessel masters can encounter. After picking up a pilot, the ship transits to a berth. The transit can take from 90 minutes at Freeport, Texas, to 28 hours at Baton Rouge, Louisiana.

At the terminal, the ship ties up with the assistance of tugboats. The mooring arrangement depends on the configuration of the dock. Most crude terminals use chicksans (metal arms) instead of flexible hoses for discharging the oil. Once a ship

Suggested Citation:"2 Lightering Primer." National Research Council. 1998. Oil Spill Risks From Tank Vessel Lightering. Washington, DC: The National Academies Press. doi: 10.17226/6312.
×

clears customs, it is gauged again, and discharge commences. Typically, ships discharge their entire cargo in less than 24 hours. During the discharge, crude oil tanks are washed to minimize retained cargo. After discharge, the cargo tanks are checked again, and pilots and tugs move the vessel back to sea.

Inshore Operations Using a Tug-Barge Unit as the Service Vessel

The post-transfer phase for inshore lightering differs in two fundamental respects from the process for offshore lightering. First, cargo gauging of the service vessel is typically done after the barge reaches the discharge dock. Second, the tug master, as always, is responsible for maneuvering the service vessel.

Summary

The practice of lightering is well developed, and a safety net of industry guidelines and government controls has been established. This operational framework appears to function effectively overall, as evidenced by the rarity of spills attributed to lightering in U.S. waters.

The committee identified one gap in the framework that may offer opportunities for reducing safety risks further. The concerns expressed by some mariners about unnecessary delays caused by cargo gauging at sea appear to have merit. Moreover, the successful experience of inshore operators who have delayed cargo gauging on barges until they reached port suggests that this approach may be an effective, and perhaps safer, alternative to at-sea gauging.

References

Energy Information Administration. 1996. Annual Energy Outlook 1996. Washington, D.C.: U.S. Department of Energy.


ITOL (Industry Taskforce on Offshore Lightering). 1990. Industry Lightering Operations Supplement to OCIMF Ship to Ship Transfer Guidelines for U.S. Gulf Coast—Galveston Zone. Houston: ITOL.

ICS (International Chamber of Shipping) and OCIMF (Oil Companies International Marine Forum). 1997. Ship to Ship Transfer Guide (Petroleum). London: Witherby & Co., Ltd.


NRC (National Research Council). 1991. Tanker Spills: Prevention by Design. Washington, D.C.: National Academy Press.

NRC. 1997. Double-Hull Tanker Legislation: An Assessment of the Oil Pollution Act of 1990 . Washington, D.C.: National Academy Press.


OTA (Office of Technology Assessment). 1989. Competition in Coastal Seas: An Evaluation of Foreign Maritime Activities in the 200-Mile EEZ: Background Paper. OTA-BP-O-55. Washington, D.C.: U.S. Government Printing Office.

Oil and Gas Journal Data Book. 1998. Houston, Texas: Penn Welling Publishing.

Oil Companies International Marine Forum (OCIMF). 1995. Prevention of Oil Spillages through Cargo Pumproom Sea Valves. London: Witherby & Co., Ltd.

Suggested Citation:"2 Lightering Primer." National Research Council. 1998. Oil Spill Risks From Tank Vessel Lightering. Washington, DC: The National Academies Press. doi: 10.17226/6312.
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Suggested Citation:"2 Lightering Primer." National Research Council. 1998. Oil Spill Risks From Tank Vessel Lightering. Washington, DC: The National Academies Press. doi: 10.17226/6312.
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The safety record of lightering (the transfer of petroleum cargo at sea from a large tanker to smaller ones) has been excellent in U.S. waters in recent years, as evidenced by the very low rate of spillage of oil both in absolute terms and compared with all other tanker-related accidental spills. The lightering safety record is likely to be maintained or even improved in the future as overall quality improvements in the shipping industry are implemented. Risks can be reduced even further through measures that enhance sound lightering standards and practices, support cooperative industry efforts to maintain safety, and increase the availability of essential information to shipping companies and mariners. Only continued vigilance and attention to safety initiatives can avert serious accidents involving tankers carrying large volumes of oil.

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