oil spill science and technology || spill occurrences: a world overview

Oil Spill Science and Technology. DOI: 10.1016/B978-1-85617-943-0.10002-4

Copyright � D.S. Etkin 2011.

Chapter 2

7

Spill Occurrences: A WorldOverview

Dagmar Schmidt-Etkin

Chapter Outline
2.1. Introduction 7
2.2. Executive Summary
8
2.3. Overview of Spill

Occurrences

8

2.1. INTRODUCTION

Asked to picture an oil spill, most people envision a large tank ship (tanker)grounded on a large rock or reef after having gone off-course in a storm ordue to navigational errors. Depending on one’s frame of reference andnationality, this might be the Exxon Valdez incident, the Hebei Spirit spill,or perhaps the Prestige spill. Oil-coated beaches, dead birds, angry fish-ermen, and massive cleanup efforts complete the picture. Although thesetypes of “catastrophic” spill incidents do indeed occur occasionally andreceive considerable media coverage, they are, fortunately, relatively rareevents.

Much more commonly, oil spills are much smaller in scope. On any givenday, hundreds, if not thousands, of spills are likely to occur worldwide in manydifferent types of environments, on land, at sea, and in inland freshwatersystems. The spills are coming from the various parts of the oil industrydfromoil exploration and production activities, from transport of that oil by tankships, pipelines, and railroad tankcars to the refineries, and from the refinerieswhere the oil is refined to create the many types of fuels that are then trans-ported by pipeline, rail, truck, or tank vessel to the consumers of that oil.Consumption-related spillage comes from manufacturing facilities, nontankvessels that carry oil only as fuel and for machinery, tanker trucks bringing oilsto service stations and heating oil tanks, and many miscellaneous sources. Thespills occur because of structural failures, operational errors, weather-related

8 PART | I Introduction and the Oil Spill Problem

events, earthquakes, human errors and negligence, and even vandalism orterrorism. The spills involve many different types of oil ranging from varioustypes of crude oil to a large array of refined products, from heavy persistentfuels to lighter, less persistent, but very toxic lighter fuels.

Because each spill occurs in a different location under different circum-stances of oil type and volume, proximity to sensitive resources, season,weather effects, and currents, each spill is a relatively unique event in terms ofimpacts, damages, and response challenges.

2.2. EXECUTIVE SUMMARY

Worldwide oil spillage rates have decreased dramatically since the 1960sand 1970s, from about 635,000 tons annually to about 300,000 tons peryear from all sources, not counting the anomalous intentional spillageassociated with the 1991 Gulf War, which amounted to over 82 million tonson land and at sea. The largest sources of oil spills in the last two decadeshave been related to oil transportation by tank ships (tankers) or throughpipelines.

Oil inputs from spills and other chronic discharge sources, such as urbanrunoff, refinery effluents, and vessel operational discharges, currently totalabout 1.2 million tons worldwide annually. While most spills are relativelysmall and cause localized impacts, occasionally very large spills occur thatcause significant environmental and socioeconomic damages. Despite signifi-cant progress in reducing spillage through a variety of technological andregulatory prevention measures along with better industry practices, the risk forsignificant oil spills remains.

A more detailed analysis of oil spillage in the United States, for whichthere are more accurate data than many other parts of the world, reveals thatduring the decade of 1998e2007, inland pipelines spilled an average ofnearly 11,000 tons annually, with the next largest source being refineries,which spilled 1,700 tons. Inland tanker truck spills amounted to 1,300 tonsannually. Tank ships only spilled an average of 500 tons annually during thisdecade. Nevertheless, the risk for large spills from tank ships, facilities, andoffshore oil exploration and production, all of which contain large volumesof oil, remains a concern for contingency planners and spill responders.

2.3. OVERVIEW OF SPILL OCCURRENCES

2.3.1. Natural Oil Seepage

Oil slicks on water and oiled shorelines are not new phenomena. A considerableamount of crude oil is discharged each year from “natural seeps”dnaturalsprings from which liquid and gaseous hydrocarbons (hydrogen-carboncompounds) leak out of the ground. Oil seeps are fed by natural underground

9Chapter | 2 Spill Occurrences: A World Overview

accumulations of oil and natural gas. Oil from submarine (and inland subter-ranean) oil reservoirs comes to the surface each year, as it has for millions ofyears due to geological processes.

Natural discharges of petroleum from submarine seeps have been recor-ded throughout history going back to the writings of Herodotus1 and MarcoPolo.2 Archaeological studies have shown that products of oil seeps wereused by Native American groups living in California, including the Yokuts,Chumash, Achomawi, and Maidu tribes, well before the arrival of Europeansettlers.3

In recent times, the locations of natural seeps have been used for explo-ration purposes to determine feasible locations for oil extraction. Regionalassessments of natural seepage have been conducted in some locations,particularly nearshore in California,4-7 the Indian Ocean,8-10 and the Gulf ofMexico.11 The most comprehensive worldwide assessment of natural seepageis still the study conducted by Wilson et al.12 Even the two more recentinternational assessments of oil inputs into the sea13 relied heavily on theestimates of natural oil seepage conducted by Wilson et al.,12 having foundno more recent comprehensive studies. While industry studies have beenconducted for the purpose of determining potential locations for oil explo-ration and production using various forms of increasingly sophisticatedtechnology, no results have been openly published in the scientific or tech-nical literature.

Natural seeps are of such great magnitude that, according to theprominent geologists Kvenvolden and Cooper,14 “natural oil seeps may bethe single most important source of oil that enters the ocean, exceedingeach of the various sources of crude oil that enters the ocean through itsexploitation by humankind.” Assessments of natural oil seepage involve fewactual measurements, though certain seep locations along the SouthernCalifornia coast of the Pacific Ocean have been studied to some extent.Natural seep studies have also included identification of hydrothermicallysourced hydrocarbons (especially polycyclic aromatic hydrocarbons) insediments. The most well-known studies have relied on estimation meth-odologies based on field data, observations, and various basic assumptions.Wilson et al. estimated that total worldwide natural seepage ranged from0.2 to 6.0� 106 tonsy annually, with the best estimate being 0.6� 106 tons,based largely on observations of seepage rates off California andwestern Canada.12 Estimates of the areas of ocean with natural seeps areshown in Table 2.1, and estimates of seepage rates by ocean are shown inTable 2.2.

yOil measurements are in metric tons (tons). Within the industry, oil is often measured in barrels

(equivalent of 42 U.S. gallons or 159 liters), roughly equal to one-seventh of a ton, depending on

specific gravity. Conversion between tons (weight) and barrels (volume) is per the formula: tons ¼0.173� barrels� specific gravity.

TABLE 2.1 Seepage-prone Areas of the World’s Oceans (based on

Wilson et al.12)

Ocean

Number of 1,000 Square Kilometers

High-potential

Seepage

Moderate-potential

Seepage

Low-potential

Seepage

Pacific 1,943 9,285 4,244

Atlantic 1,303 10,363 11,248

Indian 496 7,928 3,010

Arctic 0 5,636 2,456

Southern 0 486 458

Total 3,741 33,697 21,416


Wilson et al. based their estimates on five basic assumptions: More seepsexist in offshore basins than have been observed; factors that determine seepagerates in a particular area are related to general geological structural type andstage of sedimentary basin evolution; seepage is dependent on the area ofexposed rock rather than on rock volume; most marine seeps are clustered atcontinental margins; and seepage rates are lognormally distributed.12

TABLE 2.2 Summary of World Seepage Rates (based on Wilson et al.12)

Ocean

Estimated Oil Seepage (106 tons per year)

Case I, P16z Case II, P1.0

x Case III, P0.3**

Pacific 2.83 � 106 2.69 � 105 0.689 � 105

Atlantic 2.06 � 106 1.96 � 105 5.04 � 104

Indian 9.30 � 105 8.85 � 104 2.28 � 104

Arctic 2.14 � 105 2.30 � 103 5.20 � 103

Southern 1.88 � 104 1.74 � 103 4.51 � 102

Total 6.05 3 106 0.558 3 105 0.148 3 106

zProbability percentile 16 with a worldwide estimate of 6 � 106 tons annually, likely a high estimate.xProbability percentile 1.0 with a worldwide estimate of 0.6 � 106 tons annually.

**Probability percentile 0.3 with a worldwide estimate of 0.2 � 106 tons annually, likely a minimal

estimate.


Kvenvolden and Harbaugh15 concluded that the minimal worldwide esti-mate (0.2� 106 tons annually) from the Wilson et al.12 study is most likelycorrect and that an error margin of an order of magnitude above and below thisvalue should be applied (i.e., 0.02� 106 to 2.0� 106 tons annually). Theirtheory was based on a reduced value for the assumed and known oil resourcesthat would be available for seepage. There is some evidence that seepage ratesare decreasing in some locations, such as those near Coal Point, off SantaBarbara, California.16

In a 2003 National Research Council (NRC) study, a worldwide estimate ofnatural seepage into the marine environment of between 0.02� 106 to 2.0� 106

tons annually was made, with a “best estimate” of 600,000 tons.17 Theseestimates were made based on the Kvenvolden and Harbaugh15 reassessment ofthe estimates made by Wilson et al.,12 as well as an acceptance of the originalestimates of Wilson et al.,12 resulting from a “new appreciation” for themagnitude of natural seepage, particularly in the Gulf of Mexico. Relyinglargely on the Wilson et al.12 and Kvenvolden and Harbaugh15 studies, the 2007Joint Group of Experts on Scientific Aspects of Marine Protection (known asGESAMP) study on oil inputs into the marine environment included an esti-mate of the range of natural seepage as 0.2�2.0� 106 tons per year, with a bestestimate of 600,000 tons per year.13

Natural seeps often release oil sporadically in relatively small amounts, butoccasionally release larger amounts that can have the same environmentalimpacts as crude oil spills from tankers or other sources. But while naturalseeps have had impacts on the marine and terrestrial environment sinceprehistoric times, it was not until the occurrence of several larger anthropogenicoil spills in the late 1960s, which coincided with a greater public awarenessof general environmental issues, that concern over oil pollution came to theforefront.

2.3.2. Historical Concern Over Oil Pollution

When the tanker Torrey Canyon spilled 130,000 tons of crude oil off thewestern coast of the UK in March 1967, killing 15,000 seabirds and oilingnearly 300 kilometers of English and French coastline, there was a large publicoutcry. The environmental damage from this spill was multiplied by the use ofhighly toxic first-generation dispersant chemicals in the response.

The Torrey Canyon spill was not the first oil tanker spill by any means.A large number of oil tankers were torpedoed and sunk during World War II.According to Campbell et al., during the first six months of 1942 alone, a totalof 484,200 tons of oil were released from torpedoed tankers within 90 kilo-meters of the eastern U.S. coast.18 This came to about one tanker spill of about20,000 tons per week over six months. Cleanup efforts consisted of burningincidental to the torpedoing and minimal cosmetic actions on swimming bea-ches. While the occurrence of these incidents during wartime may explain the


relatively low concern about environmental damage from the spilled oil, therewas, arguably, a general lesser awareness of environmental protection in thesetimes as well.

The Torrey Canyon spill in 1967 was notable in that when it occurred, it isthe largest spill to date. The tanker’s capacity had recently been increased tohold 130,000 tons of oil cargo. Subsequently, there were at least five signifi-cantly larger worst-case discharge (complete cargo loss) tanker spills, as well asseveral other large spills associated with oil wells and pipelines. Following onthe 1967 Torrey Canyon incident, the 1969 Union Alpha Well 21 blowout offSanta Barbara, California, which released 14,300 tons of crude oil, is oftencredited with being the impetus for the environmental movement in the UnitedStates, as well as for the establishment of the federal Environmental ProtectionAgency (EPA).19

In the 1970s, other significant oil spills around the world brought greaterattention to the problem on an international scaledthe tanker Metula (Chile in1974), the tanker Urquiola (Spain in 1977), the tanker Amoco Cadiz (Francein 1978), the largest tanker spill of all time, Atlantic Empress (Trinidadand Tobago/Barbados in 1979), and the largest nonewar-related spill inhistorydthe Ixtoc I well blowout (Gulf of Mexico in 1979).20 The largest oilspills in history are listed in Table 2.3.

The 1989 tanker Exxon Valdez spill in Alaska is perhaps the most notoriousspill incident, though it is by no means the largest. The spillage of over 37,000tons of Alaskan crude oil into what was considered to be a “pristine” location,Prince William Sound, precipitated the most expensive and the lengthiest spillresponse and damage settlements in history. Its repercussions were felt world-wide, resulting in the passage of significant spill prevention and liability legis-lation in the United Statesdthe Oil Pollution Act of 1990 (OPA 90)das well asinternational conventions on spill prevention that included such measures as therequirement for double-hulls on tankers by 2015 and increased financial liability.The significant financial consequences for tanker owners and operators asa result of the Exxon Valdez spill and the spiller liability inherent in subsequentregulations brought the consequences for spills to an unprecedented level. Thefinancial risk associated with large spills may have had as much impact on spillprevention as any actual preventive measures, such as double-hulls on tankers.

2.3.3. Sources of Oil Spills and Patterns of Spillage

Spills occur around the worlddanywhere that oil is produced, transported,stored, or consumed. The vast majority of spills are relatively small. As shownin Figure 2.1, 72% of spills are 0.003 to 0.03 ton or less. The total of amount ofthese small spills comes to 0.4% of the total spillage. The largest spills (over 30tons) make up 0.1% of incidents but involve nearly 60% of the total amountspilled. Naturally, the relatively rare large spill incidents get the most publicattention owing to their greater impact and visibility, though spill size itself is

TABLE 2.3 Largest Oil Spills in History Worldwide Environmental Research

Consulting (ERC data)**

Date Source Name* Location Tons

10-Mar-1991 700 oil wellsy Kuwait 71,428,571

20-Jan-1991 Min al Ahmadi Terminalyz Kuwait 857,143

3-Aug-2000 oil wells Russia 700,000

3-Jun-1979 Ixtoc I well Mexico 476,190

1-Feb-1991 Bahra oil fieldsy Iraq 377,537

2-Mar-1990 oil well Uzbekistan 299,320

19-Jul-1979 T/V Atlantic Empressx Trinidad/Tobago 286,354

25-Oct-1994 Kharyaga-Usinsk Pipeline Russia 285,714

4-Feb-1983 No. 3 Well (Nowruz)y Iran 272,109

6-Aug-1983 T/V Castillo de Bellver South Africa 267,007

16-Mar-1978 T/V Amoco Cadiz France 233,565

10-Nov-1988 T/V Odyssey Canada 146,599

11-Apr-1991 T/V Haven Italy 144,000

1-Aug-1980 D-103 concession well Libya 142,857

6-Jan-2001 pipeline Nigeria 142,857

19-Jan-1991 T/V Al Qadasiyahyz Kuwait 139,690

19-Jan-1991 T/V Hileeny Kuwait 139,690

18-Mar-1967 T/V Torrey Canyon United Kingdom 129,857

19-Dec-1972 T/V Sea Star Oman 128,891

23-Feb-1980 T/V Irenes Serenade Greece 124,490

19-Jan-1991 T/V Al-Mulanabbiyz Kuwait 117,239

7-Dec-1971 T/V Texaco Denmark Belgium 107,143

19-Jan-1991 T/V Tariq Ibn Ziyadyz Kuwait 106,325

20-Aug-1981 storage tanks Kuwait 106,003

26-Jan-1991 Min al Bakar Terminalyz Kuwait 100,000

15-Nov-1979 T/V Independentza Turkey 98,255

11-Feb-1969 T/V Julius Schindler Portugal 96,429

(Continued )



Consulting (ERC data)**dcont’d


12-May-1976 T/V Urquiola Spain 95,714

25-May-1978 No. 126 Well/pipeline Iran 95,238

28-Mar-1995 pipeline Nigeria 90,000

5-Jan-1993 T/V Braer United Kingdom 85,034

1-Mar-1991 pipelineyz Kuwait 83,897

29-Jan-1975 T/V Jakob Maersk Portugal 82,503

6-Jul-1979 storage tank (Tank #6) Nigeria 81,429

19-Nov-2002 T/V Prestige Spain 77,000

3-Dec-1992 T/V Aegean Sea Spain 74,490

6-Dec-1985 T/V Nova Iran 72,626

15-Feb-1996 T/V Sea Empress United Kingdom 72,361

19-Dec-1989 T/V Khark 5 Morocco 70,068

27-Feb-1971 T/V Wafra South Africa 68,571

11-Dec-1978 fuel storage depot Zimbabwe 68,027

26-Apr-1992 T/V Katina P. South Africa 66,700

12-Jun-1978 Sendai Oil Refinery Japan 60,204

6-Dec-1960 T/V Sinclair Petrolore Brazil 60,000

7-Jan-1983 T/V Assimi Oman 53,741

9-Nov-1974 T/V Yuyo Maru No. 10 Japan 53,571

28-May-1991 T/V ABT Summer Angola 51,020

22-May-1965 T/V Heimvard Japan 50,000

31-Dec-1978 T/V Andros Patria Spain 49,660

30-Jan-1991 T/V Ain Zalahyz Kuwait 49,543

13-Jun-1968 T/V World Glory South Africa 48,214

13-Jan-1975 T/V British Ambassador Japan 48,214

9-Dec-1983 T/V Pericles GC Qatar 47,619

9-Aug-1974 T/V Metula Chile 47,143



Consulting (ERC data)**dcont’d


1-Jun-1970 T/V Ennerdale Seychelles 46,939

7-Dec-1978 T/V Tadotsu Indonesia 44,878

29-Feb-1968 T/V Mandoil United States 42,857

10-Jun-1973 T/V Napier Chile 38,571

13-Mar-1994 T/V Nassia Turkey 38,500

26-Aug-1979 T/V Patianna United Arab Emirates 38,000

11-Jun-1972 T/V Trader Greece 37,500

24-Mar-1989 T/V Exxon Valdez United States 37,415

29-Dec-1980 T/V Juan Antonio Lavalleja Algeria 37,279

21-Oct-1994 T/V Thanassis A. Hong Kong 37,075

22-Apr-1988 T/V Athenian Venture Canada 36,061

7-Feb-1977 T/V Borag Taiwan 35,357

Mar-1986 Pemex Abkatun 91 Mexico 35,286

6-Feb-1976 T/V St. Peter Colombia 35,100

*“T/V” ¼ “tank vessel” and refers to tank ships or tankers.

**Ended in January 2010.yWar-related intentional spillage.zSeveral intentional spills occurred nearly simultaneously during the 1991 Gulf War. They are often

aggregated into one large “spill.” In this list, the individual spill sources are separated.xT/V Atlantic Empress spilled 145,250 tons of oil off Trinidad and Tobago on 19 July 1979, then

another 141,000 tons while under tow off Barbados.


not a direct measure of damage. Location and oil type are extremely importantin determining the degree of environmental and socioeconomic damage.

Oil spills and discharges* can occur at any point in the “life cycle” ofpetroleumdduring oil exploration and production; transport by vessel, pipe-line, railroad, or tanker truck; refining; storage, consumption or usage as fuelor as raw material for manufacturing; or waste disposal. The regional andnational patterns of spillage depend on the oil-related activities in those

*A “spill” is a discrete event in which oil is accidentally or, occasionally, intentionally released. A

“discharge” is a legal permitted release of oil (usually in a highly diluted state in water) as part of

normal operations.

71.9%

22.8%

6.2%

1.6%0.3% 0.1% 0.0%0.4%

1.6%

4.3%

11.7%

22.2%

39.5%

20.3%

0%

10%

20%

30%

40%

50%

60%

70%

80%

0.003 0.03 0.3 3 3,000 30 300

% Total Spills

Spill Size (tonnes)

# spills

amount

FIGURE 2.1 Size classes of U.S. marine oil spills, 1990e1999 (ERC data).


locations, the amount of oil handled, and the degree to which oil preventionmeasures have been implemented and enforced.

Overall, oil spillage has decreased significantly in the United States andinternationally due to the implementation and enforcement of preventionmeasures as well as more responsible operations on the part of the shipping andoil industries.13,17,21,22

In the 1970s, an estimated 6.3 million tons of oil spilled into marine watersfrom all sources, excluding war-related incidents.22 By the 1980s, an estimated3.8 million tons of oil spilled worldwide, a 40% reduction since the decade1988e1997. Spillage reduced another 20% by the 1990s.

These reductions in spillage are all the more remarkable considering theincreases in production, shipping, and handling of oil during this time period(Table 2.4).

In a series of studies that estimated total oil inputs into the marine envi-ronment from spills, as well as from operational discharges* from shipping andother sources, especially urban runoff,y a definitive trend of input reduction isapparent (Table 2.5). It is important to note that some of the variations betweenthe studies are due to differences in methodology rather than to actual differ-ences in inputs.

*A legal permitted release of oil (usually in a highly diluted state in water) as part of normal

operations.y“Urban runoff” is the accumulation of drops of oil that leak from automobiles, trucks, and other

vehicles, as well as small chronic spillages that occur from other land-based sources. The oil

washes off into storm sewers, culverts, and other waterways into streams and rivers that enter

marine waters. Because the exact source of this spillage cannot be pinpointed, it is termed nonpoint

source pollution.

TABLE 2.4 Annual Worldwide Marine Oil Spillage (ERC Data)

Source Type

Estimated Average Annual Tons Spilledy

1970s 1980s 1990s

Tank Vessels 428,646 190,180 126,743

Nontank Vessels 2,735 23,811 10,248

Pipelines 59,087 36,744 85,664

Facilities 66,067 58,047 35,655

Offshore Exploration/Production

69,111 68,099 38,351

Unknown/Other 9,241 1,775 3,905

Total 634,887 378,656 300,546

yExcluding war-related spills.


The tracking of oil spills is generally conducted by those authoritiesinvolved in initiating emergency spill response operations, such as CoastGuard agencies or state and local governments. The accuracy of reporting,particularly of smaller spills, varies considerably from one jurisdiction toanother. There have been increases in the reporting of increasingly smallerspills, though not necessarily in the actual incidence of such spills, whichreflects broader public awareness of spills and greater concern about andresponsibility for these incidents by spillers. As larger spills become increas-ingly rarer, it is important that contingency planners and spill respondersmaintain preparedness for these large spills owing to the potential damagesassociated with them.22,23 A detailed recent overview of oil spills in the UnitedStates is presented here based on Environmental Research Consulting (ERC)data, along with analytical results from some past international studies on oilspills.24-28

2.3.4. Spillage from Oil Exploration and Production Activities

During the years 1998e2007, an estimated 182 tons of crude oil spilledannually from offshore exploration and production platforms into U.S. waters.An additional 373 tons spilled annually from pipelines associated with offshoreoil production, for a total of 555 tons per year. This represents a nearly 66%reduction in spillage since 1988e1997, and an 87% reduction in spillage sincethe 1970s (1969e1977). Oil spillage from offshore platforms in U.S. OuterContinental Shelf (OCS) and state waters is shown in Figure 2.2 for 1969e2007.

TABLE 2.5 Estimated Worldwide Oil Inputs Based on Various Studies

Source

Oil Input Estimates (Tons)

1973z 1979x 1981** 1981yy 1990zz 1997xx 2000***

Natural Seeps 600,000 600,000 300,000 200,000 258,500 600,000 600,000

Municipal/Industrial 2,700,000 2,250,000 1,480,000 1,230,000 1,175,000 114,900 156,900

Urban Runoff 2,500,000 2,100,000 1,430,000 1,080,000 e n/a 140,000

Coastal Refinery 200,000 e e 100,000 e 112,500 4,900

Other Coastal e 150,000 50,000 50,000 e 2,400 12,000

Transportation 2,130,000 1,100,000 1,440,000 1,420,000 564,000 389,000 413,100

Tanker Accidents 300,000 300,000 390,000 400,000 e 157,900 100,000

Other Shipping 750,000 200,000 340,000 320,000 e 586,500yyy 7,100

Operational 1,080,000 600,000 710,000 700,000 e 225,800 306,000

Atmosphericzzz 600,000 600,000 300,000 300,000 305,000 68,000 24,700

Offshore Expl/Prod 80,000 60,000 50,000 50,000 47,000 19,750 38,000

TOTAL 10,940,000 7,960,000 6,490,000 5,850,000 2,349,500 2,246,750xxx 1,802,700

z[24]x[25]**[26]yy[27]zz[28]xx[13]***[17]yyyIncludes 53,000 tons from small-craft activity.zzzAtmospheric deposition of petroleum hydrocarbons from volatile organic compounds (VOCs) that evaporate during the handling of oil and incomplete fuel combustion

that are then deposited into the sea.xxxDoes not include urban runoff.

18

PART

|I

Intro

ductio

nan

dtheOilSp

illProblem

0

2,000

4,000

6,000

8,000

10,000

12,000

14,000

16,000

18,000

1969 1974 1979 1984 1989 1994 1999 2004

Tonnes

FIGURE 2.2 Annual U.S. offshore oil platform spillage, 1969e2007 (ERC data).


Average platform spillage by decade is shown in Table 2.6. There has been a 30%reduction in annual spillage since 1988e1997 and a 95% reduction since the1970s.

Annual oil spillage from pipelines connected to offshore platforms is shownin Figure 2.3, and by decade in Table 2.7. There has been a 68% reduction inoffshore pipeline spillage since 1988e1997. Of the total spillage, 96% is in theGulf of Mexico. Offshore oil exploration and production spillage was combinedto include offshore platforms and pipelines, as well as offshore supply vesselsservicing the platforms, as shown in Table 2.8. There has been a 61% reductionin total spillage since 1988e1997 and an 87% reduction since the 1970s.

TABLE 2.6 Average Annual Spillage from U.S. Offshore Oil Platforms

(ERC data)

Years

Average Annual Spills

One Ton or More

Average Annual

Tons Spilled

1969e1977 45 3,694

1978e1987 29 192

1988e1997 14 259

1998e2007 20 182

1969e2007 27 1,015

0

500

1,000

1,500

2,000

2,500

3,000

3,500

4,000

4,500

5,000

1969 1974 1979 1984 1989 1994 1999 2004

Tonnes

FIGURE 2.3 Annual oil spillage from U.S. offshore pipelines, 1969e2007 (ERC data).

TABLE 2.7 Average Annual Spillage from U.S. Offshore Oil Pipelines

(ERC data)

Years

Average Annual Spills

One Ton or More

Average Annual

Tons Spilled

1969e1977 15 640

1978e1987 10 495

1988e1997 14 1,161

1998e2007 13 373

1969e2007 13 668


Oil spillage per production (i.e., barrels spilled per barrels produced) hasdecreased over time, as shown in Table 2.9. In other words, despite increases inproduction, spillage rates have decreased. For every ton of oil produced in theUnited States, less than 0.000005 tons have spilled from offshore explorationand production activities in the last decade. This is a 71% reduction since the1988e1997 decade and an 87% reduction since the 1969e1977 decade.

While the majority of oil production spills have been recorded in offshorewaters, there are reported spills of inland-based oil production wells to inlandareas, as shown in Table 2.10.

During the oil extraction process at offshore oil platforms, water in the oilreservoir is also pumped to the surface. Industry practice is to treat this

TABLE 2.9 U.S. Offshore Oil Exploration/Production Spillage per

Production (ERC data)

Years Average Annual Tons Spilled per Tons Produced

1969e1977 0.0000089

1978e1987 0.0000015

1988e1997 0.0000040

1998e2007 0.0000012

1969e2007 0.0000038

TABLE 2.10 Average Annual U.S. Inland Oil Exploration/Production Spillage

(ERC data)

Years Average Annual Tons Spilled

1980e1987 521

1988e1997 742

1998e2004 863

1980e2004 705

TABLE 2.8 Average Annual Spillage (tons) from U.S. Offshore Oil Activities

(ERC data)

Years Platforms Pipelines Offshore Vessels Total

1969e1977 3,694 640 14 4,348

1978e1987 192 495 39 726

1988e1997 259 1,161 7 1,427

1998e2007 182 373 1 556

1969e2007 1,015 668 15 1,698


“produced water” to separate free crude oil, and then to inject the water backinto the reservoir, or to discharge the water overboard from the platform.Increasingly, the reinjection process is becoming the preferred technique. Thehighly diluted oil content in produced water (with a maximum allowable oil

TABLE 2.11 Estimated Oil Inputs in Produced Water from U.S. Offshore Oil

Exploration/Production

U.S. Region

Produced Water

(tons/yr)

Oil/Grease Content

(ppm)

Oil/Grease

Discharge (tons/yr)

Low High “Best”* Low High “Best”

Gulf of MexicoOCS

67,571,429 15 29 20 1,300 2,500 1,700

Louisiana State 26,571,429 15 29 20 450 860 600

Texas State 614,286 e e 6.6 0 0 5

CaliforniaOffshore

5,157,143 15 29 18 85 170 85

Alaska State 6,528,571 15 29 15 110 210 110

Total US 106,442,858 e e 20 2,000 3,740 2,500

*Best estimate as determined by panel of experts in the 2003 NRC study.17


content of 29 ppm) from offshore oil exploration and production processes isgenerally dispersed very quickly in the open waters where offshore oil plat-forms are located. The impacts from these inputs in offshore waters have beenstudied extensively, and, as concluded by the 2003 NRC study, “there is littleevidence of significant effects from petroleum around offshore platforms indeep water.”17 The oil inputs from produced water are calculated as shown inTable 2.11don average, 2,500 tons per year, based on the methodology usedby the 2003 NRC study based on measurements and assumptions of maximumallowable oil content in produced water (“high”) or lower oil content asreported by offshore operators.17 It is important to note that these inputs arepermitted operational discharges that are distinct from accidental spillagepreviously reviewed.

Worldwide estimates on oil spillage and discharges from offshore oilexploration and production activities are shown in Table 2.12.

The greatest concern associated with oil pollution from offshore oil and gasexploration is the unlikely event of a catastrophic well “blowout”*. The largestwell blowout incidents worldwide are shown in Table 2.13. Fortunately, mostblowouts release relatively little oil.29

*Loss of well control or a blowout is defined as: the uncontrolled flow of formation or other fluids,

including flow to an exposed formation (an underground blowout) or at the surface (a surface

blowout), flow through a diverter, or uncontrolled flow resulting from a failure of surface

equipment or procedures.

TABLE 2.12 Worldwide Spillage and Discharge from Offshore Oil

Exploration and Production

Study

Estimate

Year

Annual Oil Input Estimate (tons)

Spillage Operational Atmospheric Total

NRC, 1975 [24] 1973 e e e 80,000

Kornberg, 1981[25]

1979 e e e 60,000

Baker, 1983 [26] 1981 e e e 50,000

NRC, 1985 [27] 1981 e e e 50,000

GESAMP, 1993 [28] 1990 e e e 47,000

GESAMP, 2007 [13] 1997 3,400 16,350 e 19,750

NRC, 2003 [17] 2000 860 19,000 1,300 21,160


2.3.5. Spills During Oil Transport

After extraction from offshore or terrestrial wells, oil is transported by a varietyof means to refineries and ultimately to industrial or individual consumersdbytank vessel (tank ships or tankers; tank barges), pipeline, railroad, and tankertruck, each potentially a source of spillage.

2.3.5.1. Spillage from Tank Vessels

Tank ships can carry the greatest amount of oildas much as 300,000 tonsdandthus can be the sources of the largest transport-related spills. Tank ships (tankers)carrying crude oil or refined petroleum as cargo spilled an average of 514 tons ofoil annually inU.S. waters over the last decade, a 90% reduction since the decade1988e1997. A breakdown of annual spillage from oil tankers is shown inFigure 2.4. Average annual spillage by decade is shown in Table 2.14.

Tank barges carrying oil as cargo spilled an average of 771 tons of oilannually over the last decade, a nearly 67% reduction from the spillage in thedecade 1988e1997. Annual spillage volumes are shown in Figure 2.5. Abreakdown of average annual spillage from oil tank barges is shown in Table2.15. Oil transport by tank vessels (tankers and barges) has decreased over thelast decades in the United States.

Oil spillage from tank vessels in the United States in relation to oil trans-ported by this mode decreased by 71% since the decade 1988e1997 and 81%since the 1980s (Table 2.16). Worldwide estimates of tanker and tank bargespillage made in international studies are shown in Table 2.17.

TABLE 2.13 Largest Offshore Exploration and Production Well Blowouts

Worldwide (ERC data)

Well Location Date Tons

Ixtoc I Bahia del Campeche,Mexico

June 1979 471,430

Pemex Abkatun 91 Bahia del Campeche,Mexico

October 1986 35,286

Phillips Ekofisk Bravo North Sea, Norway April 1977 28,912

Nigerian NationalFuniwa 5

Forcados, Nigeria January 1980 28,571

Aramco Hasbah 6 Gulf, off Saudi Arabia October 1980 15,000

Iran MarineInternational

Gulf, off Laban Island,Iran

December 1971 14,286

Union Alpha Well 21 Santa Barbara,California, USA

January 1969 14,286

Chevron MainPass 41-C

Gulf of Mexico, Venice,Louisiana, USA

March 1970 9,286

Pemex Yum II/Zapoteca Bahia del Campeche,Mexico

October 1987 8,378

Shell South TimabalierB-26

Gulf of Mexico, BayMarchand, Louisiana,USA

December 1970 7,585


2.3.5.2. Spills from Pipelines

In inland areas, underground and above-ground pipelines transport large quan-tities of crude oil and refined fuels, particularly diesel, gasoline, heavy fuel oil,and trans-mix.* Spillage from pipelines in coastal and inland areas is shown inTable 2.18 and Figure 2.6. During the last decade, coastal and inland pipelinesspilled an average of 11,000 tons of oil annually. This represents a 35%reduction in spillage since 1988e1997 and 70% since the 1970s. In theseanalyses, coastal and inland pipelines were considered to encompass all parts ofthe pipeline system, including gathering pipes, transmission pipes, breakouttanks, pump stations, and tank farms directly associated with and operated bypipeline companies. Offshore pipelines were considered separately under

*Usually a combination of No. 2 fuel oil (diesel) and No. 6 heavy fuel oil.

0

10,000

20,000

30,000

40,000

50,000

60,000

70,000

80,000

90,000

1962 1967 1972 1977 1982 1987 1992 1997 2002 2007

Tonnes

FIGURE 2.4 Spills into U.S. waters from tank ships, 1962e2007 (ERC data).

TABLE 2.14 Average Annual Oil Spillage from Tank Ships in U.S. Waters

(ERC data)

Years

Average Number

of Spills One Ton or More

Average Annual

Tons Spilled

1962e1967 e 7,162

1968e1977 301 27,513

1978e1987 153 8,607

1988e1997 55 6,028

1998e2007 19 514


offshore exploration and production. It should be noted that a significant portionof oil (about 85%) that spills from inland pipelines goes to containment areasaround breakout tanks or to solid ground rather than directly into surface waters.

With concerns about the aging pipeline infrastructure and vulnerability ofpipelines for spillage, there have been a number of regulatory changes forpipelinesdthe Oil Pollution Act of 1990 (OPA 90), the 2002 Pipeline SafetyAct (PSA), and the 2006 Pipeline Integrity, Protection, Enforcement, andSafety (PIPES) Act, which have improved pipeline safety and reduced spillage.Pipeline spillage amounts by oil type and per unit of oil transport are shown inTable 2.19. Spillage per unit transport has decreased 37% since the decade1988e1997, and 57% since the 1980s.

0

2,000

4,000

6,000

8,000

10,000

12,000

14,000

16,000

1968 1973 1978 1983 1988 1993 1998 2003

Tonnes

FIGURE 2.5 Spills into U.S. waters from tank barges, 1968e2007 (ERC data).

TABLE 2.15 Average Annual Oil Spillage from Tank Barges in U.S. Waters

(ERC data)

Years

Average Number

of Spills One Ton or More

Average Annual

Tons Spilled

1968e1977 368 4,547

1978e1987 290 7,570

1988e1997 123 3,269

1998e2007 54 776

1968e2007 186 4,040


2.3.5.3. Spills from Railroads

Railroads spilled 200 tons of oil annually as cargo in tankcars and as fuel. Thisis a 34% reduction since the decade 1988e1997. Average annual railroadspillage and spillage by ton-miles transported are shown in Table 2.20. (A ton-mile is a measure of the transport of oil one ton the distance of one mile.) Thespillage rate has decreased in the last three decades. Spills from railroads oftengo to ballast and do not always directly impact waterways.

2.3.5.4. Spillage from Tanker Trucks

Tanker trucks carrying oil (usually fuels) as cargo spilled an average of 1,300 tonsof oil annually in the last decade, a 76% increase since the decade 1988e1997.

TABLE 2.16 Oil Spillage by Tank Vessels in Relation to Oil Transported in

U.S. Waters (ERC data)

Time Period

Average Annual Spillage

(tons)Average Annual Spillage

per Billion Ton-Miles*

Oil TransportTankers Tank Barges Combined

1978e1987 8,607 7,570 16,177 27.40

1988e1997 6,028 3,269 9,297 18.22

1998e2007 514 776 1,290 5.28

*Ton-miles combine volume and distance of transport.

TABLE 2.17 Estimates of Worldwide Annual Tank Vessel Spillage

Study

Estimate of Average Annual Tank Vessel

(Tank Ship and Tank Barge) Spillage (tons)

1970s 1980s 1990s

NRC, 1975 300,000 e e

Kornberg, 1981 300,000 e e

Baker, 1983 e 390,000 e

NRC, 1985 e 400,000 e

GESAMP, 1993 e 564,000* e

GESAMP, 2007 e e 157,900

NRC, 2003 e e 100,000

Etkin, 2001 372,878 98,866 184,460y

ERC Data 431,381 213,991 136,991z

*Includes operational discharges from vessels.yIncludes 1991 Gulf War-related tanker spillage.zExcludes 1991 Gulf War-related tanker spillage.


Thismay be attributed to better reporting of these incidents to local authorities thatusually handle these incident responses. Spills from tanker trucks often go topavements and do not directly impact waterways. Average annual spillage is inTable 2.21. There are no reliable international data on this source type.

TABLE 2.18 Oil Spillage from U.S. Inland and Coastal Pipeline Systems

(ERC data)

Years

Average Annual Number

of Spills One Ton or More Average Annual Tons

1968e1977 276 37,049

1978e1987 172 25,885

1988e1997 140 16,900

1998e2007 195 10,965

1968e2007 196 22,828

0

10,000

20,000

30,000

40,000

50,000

60,000

70,000

1968 1974 1979 1984 1989 1994 1999 2004

Tonnes

FIGURE 2.6 Spills into U.S. waters from pipelines, 1968e2007 (ERC data).


2.3.6. Spillage from Oil Refining

Each year, on average, over 8.6 billion tons of imported and domestically-produced crude oil are refined into hundreds of petroleum-based products andfuels at the 162 refineries in the United States. Spillage from oil refineriesaveraged 1,700 barrels annually over the last decade, about a 19% reductionsince the decade 1988e1997 and a 27% reduction in spillage per barrel of oilthroughput at refineries. Average annual spillage is shown in Table 2.22.

The lower spillage for the 1980e1987 time period is likely a data artifactsince spill sources in reports were not always accurately identified (e.g.,

TABLE 2.19 Average Annual U.S. Oil Pipeline Spillage by Oil Type and

Transport (ERC data)

Years

Spillage (tons)

Tons Spilled per Billion

Ton-Miles* Transport

Crude Refined Total Crude Refined Total

1980e1987 11,314 6,157 17,471 35.24 25.06 30.71

1988e1997 16,384 9,292 25,676 48.99 40.42 45.50

1998e2007 10,855 6,558 17,413 32.38 25.95 29.71

1980e2007 7,716 3,249 10,965 27.11 11.89 19.88

*A ton-mile is one ton of oil being transported one mile.

TABLE 2.20 Average Annual Estimated U.S. Oil Spillage from Railroads

(ERC data)

Years

Tons Spilled

per Year


Ton-Miles Transport

1980e1987 332 26.7

1988e1997 309 18.6

1998e2007 204 10.3

1980e2007 278 16.2

TABLE 2.21 Average Annual Estimated U.S. Oil Spillage from Tanker Trucks

(ERC data)

Years Tons per Year


Ton-Miles Transport

1980e1987 698 25.5

1988e1997 745 26.2

1998e2007 1,312 41.2

1980e2007 934 31.6


TABLE 2.22 Average Annual Oil Spillage from U.S. Refineries (ERC data)

Years

Tons

Spilled

Annual

Refining

Capacity (tons)

Refinery

Utilization

Annual

Throughput

(tons)

Spillage per

Refinery

Throughput

1980e1987 502 9.17 � 109 78.95% 0.66 � 109 0.00000076

1988e1997 2,145 9.41 � 109 89.71% 0.72 � 109 0.00000296

1998e2007 1,734 10.33 � 109 91.62% 0.80 � 109 0.00000216

1980e2007 1,529 9.66 � 109 87.32% 0.73 � 109 0.00000208


a refinery may merely have been identified as a “facility”). There were alsochanges in reporting requirements in 1986 that authorized the Toxics ReleaseInventory (TRI) to track facility releases of a variety of chemicals and toxicsubstances. While crude oil and refined petroleum products themselves are notencompassed by the TRI-reporting requirements, some of their additives andchemical components are listed. Overall, this created a greater awareness of theneed to report discharges from refineries. During refining, wastewater con-taining minute concentrations of oil is legally discharged in effluents, aspermitted under the National Pollutant Discharge Elimination System(NPDES). The NPDES-permitted refinery effluents contain no more than fiveparts of oil per million parts of wastewater. The effluents are generally dis-charged in rivers and coastal areas where the already dilute oil concentrationsare quickly diluted even further.

The environmental impacts of refinery effluents have been studied fairlyextensively. Environmental impacts from the oil in the effluents are extremelylow and localized. Refineries are, however, generally located in industrial areasthat have other permitted discharges, making it difficult to separate the effects ofoil in effluents from those of background concentrations of other contaminantsfrom other point and nonpoint sources. A comprehensive review of theecological impacts of refinery effluents concluded that any minor impacts arelimited to the areas close to the outfalls, but that it is difficult to distinguish theseimpacts from other pollution sources.30 The total amount of aqueous effluentdischarged from oil refineries has decreased by 20% over the last 40 years due toincreases in the use of air cooling and recirculation of cooling water. In addition,the toxicity of effluent discharges has decreased significantly owing to theimplementation of various wastewater treatment systems.30,31 The estimatedmaximum discharge of oil in refinery effluents over the last decade is 7,700 tonsper year. This estimate is the equivalent of less than 0.00001 ton of oil for eachton of oil processed, and is based on the following assumptions: wastewaterproduction as a function of refinery capacity average for the last decade is 2.37

TABLE 2.23 Estimated Annual Oil Discharged in U.S. Oil Refinery Effluents

(ERC data)

Years

Throughput

(billion tons)

Wastewater

Tons per Ton

Throughput

Wastewater

(billion bbl)

Oil in Effluent

(tons)

1985e2007 0.66 2.15 1.17 5,837

1985e1987 0.72 1.69 1.49 7,465

1988e1997 0.80 2.05 1.91 9,538

1998e2007 0.73 2.38 1.55 7,740


barrels of wastewater (refinery effluent) produced per barrel of refining capacity;and effluents contain 5 ppm of oil (based on NPDES guidelines).

There are a number of estimates of the amount of wastewater produced perunit of refining capacity. The average of the two best-documented sources wastaken.31,32 Average annual refinery effluent discharges in the United States areshown in Table 2.23. The average annual oil in legally-permitted refineryeffluent discharges is based on an assumption of maximum effluent oilconcentration of 5 ppm. This value is the maximum allowed. Actual oilconcentrations in effluents are likely to be lower. Estimates of internationalcoastal refinery spillage and effluent oil content were made as shown in Table2.24. Estimates in the 2007 GESAMP study were made using the samemethodology as for U.S. refinery effluents, with the exception that the oilcontent in the effluent was assumed to vary between 5 ppm and 25 ppm,depending on national laws and practices.13

TABLE 2.24 Estimates of Worldwide Oil Refinery Spillage and Effluent

Discharges

Study Year(s)

Estimated Average Annual Inputs

to Marine Waters (tons)

Refinery

Spillage

Oil in Refinery

Effluent

Total Refinery

Inputs

NRC, 1975 1970s 200,000 e 200,000

Baker, 1983 1980s 100,000 e 100,000

GESAMP, 2007 1990s e 179,547 179,547


2.3.7. Spillage Related to Oil Consumption and Usage

Refined petroleum products are used in a wide variety of applications,including fuels for transportation, heating, manufacturing, and electricityproduction. Spillage of oil from sources that “consume” or use oil is generallyoutside of the realm of the petroleum industry itself, but is presented here forperspective on total oil inputs.

2.3.7.1. Spillage from Nontank Vessels

“Nontank vessels” (e.g., cargo ships) carrying oil as bunker fuel and foroperations spill an average of 230 tons of oil annually, a 43% reduction sincethe decade 1988e1997. Average annual spillage from these vessels is shown inTable 2.25. At the same time, the shipment of dry cargo (i.e., nonpetroleumshipments) by vessels has increased by 43% over the last 30 years in the UnitedStates (U.S. Army Corps of Engineers). The rate of spillage from these cargoships in relation to the tonnage of cargo moved in U.S. waters during that timeperiod is shown in Table 2.26. Spillage per cargo shipment has declined by 50%since the decade 1988e1997. Worldwide nontank vessel spillage was estimatedin several international studies (Table 2.27).

Spillage from smaller vessels (e.g., passenger, fishing, recreational, andunclassified vessels) averaged under 600 tons annually over the last decade inthe United States, a nearly 34% reduction since the decade 1988e1997.Average annual spillage from these vessels is shown in Table 2.28. There are noreliable worldwide estimates of spillage from smaller vessels.

Operational discharges of lubricant oils from the vessels within ports,during transit within ports, and while moored at docks contribute a significantamount of oil to U.S. watersdabout 2,800 tons annually.33 Leakages occurfrom stern tubes and other submerged machinery, as well as from on-deck

TABLE 2.25 Average Annual Oil Spillage from Nontank Vessels in U.S.

Waters (ERC data)

Years

Annual Number of Spills

(1 ton or more) Annual Tons Spilled

1973e1977 100 149

1978e1987 85 969

1988e1997 83 402

1998e2007 37 229

1973e2007 73 479

TABLE 2.27 Estimates of Worldwide Nontank Vessel Spillage

Study

Estimate of Average Annual Nontank Vessel Spillage (tons)

1970s 1980s 1990s

NRC, 1975 750,000* e e

Kornberg, 1981 200,000* e e

Baker, 1983 e 340,000* e

NRC, 1985 e 320,000* e

GESAMP, 2007 e 533,000*

NRC, 2003 e 7,100

Etkin, 2001 1,000 4,024 5,454

ERC Data 2,735 23,811 10,248

*Includes operational discharges from nontank vessels.

TABLE 2.26 Cargo Vessel Oil Spillage per Dry Cargo Shipments in U.S.

Waters (ERC data)

Years

Dry Cargo Shipment

(million short tons)

Annual Tons

Spilled

Tons Spilled per Million

Short Tons Shipped

1978e1987 1,057 969 0.90

1988e1997 1,256 402 0.32

1998e2007 1,382 229 0.16

1978e2007 1,232 534 0.46


machinery. Based on a study by Etkin, these inputs are estimated to be as shownin Table 2.29, as calculated for the past five years.33 Previous time periods wereadjusted based on the overall amount of shipping in U.S. waters.

Operational inputs of oil and gasoline from two-stroke engines in the UnitedStates were estimated by the 2003 NRC study17 to average 7,000 tons annuallyand by the 2007 GESAMP study13 to average 53,000 tons annually worldwide(Table 2.30). It should be noted that this estimate has been questioned bya number of researchers (personal communications) with regard to theassumption that all of the gasoline enters the water rather than combusts orevaporates. The use of two-stroke engines of the type mentioned in this studyhas significantly decreased in the last few years.

TABLE 2.28 EstimatedOil Spillage from Smaller Vessels in U.S.

Waters (ERC data)

Years Annual Tons Spilled

1973e1977 2,123

1978e1987 939

1988e1997 900

1998e2007 595

1973e2007 999

TABLE 2.29 Vessel Operational Lubricant Leakage in U.S. and Worldwide

Ports33

Years

Lubricant Discharges (average annual tons)

Stern Tube Other Operational Total

U.S. Worldwide U.S. Worldwide U.S. Worldwide

1980e1987 1,064 19,558 1,036 22,082 2,101 41,488

1988e1997 1,246 22,903 1,213 25,859 2,460 48,584

1998e2007 1,400 25,734 1,363 29,055 2,764 54,589

1980e2007 1,237 22,738 1,204 25,672 2,442 48,233


2.3.7.2. Spillage from Facilities

Coastal facilities (other than refineries) spill an estimated 600 tons of oil in theUnited States annually, a 72% reduction from the decade 1988e1997. Averageannual facility spillage in the United States and worldwide is presented inTable 2.31. It is important to note that spillage volumes from coastal facilitiesoften include oil that spills into secondary containment. A secondarycontainment system provides an essential line of defense in preventing oil fromspreading and reaching waterways in the event of the failure of an oil container(e.g., a storage tank) or the primary containment. The system providestemporary containment of the spilled oil until a response can be mounted.

In the last decade, gas stations and truck stops spilled an average of 100 tonsof oil annually, a nearly 48% decrease since the decade 1988e1997. This

TABLE 2.30 Estimates of Oil Inputs from Two-Stroke Recreational Vessels in

the United States and Worldwide

Region

Estimated Average

Annual Tons Input

U.S. Atlantic* 3,100

U.S. Gulf of Mexico* 1,540

U.S. Pacific and Alaska* 2,306

U.S. Total* 6,946

Worldwide* 53,000

*Estimates based on analyses in the 2003 NRC study.17

TABLE 2.31 Estimated Oil Spillage from Coastal Marine Facilities in U.S. and

Worldwide Waters

Years U.S. Annual Tons Spilledy Worldwide Annual Tons Spilled

1973e1977 8,889 150,000z

1978e1987 6,112 50,000x

1988e1997 2,151 e

1998e2007 604 2,400*e12,000**

1973e2007 3,803 e

*From 2007 GESAMP study13 based on methods in the 2003 NRC study.17 The 2007 GESAMP

study13 had a second estimate of 3.9 � 106 tons annually.yERC dataz[24]x[25, 26]**[23]


includes all spillages that occur at gas station facilities and truck stops, includingspills that occur during the transfer of fuels from tanker trucks. Average annualspillage from these sources is shown in Table 2.32. Spills at gas stations and truckstops often go to pavements and other substrates, reducing the direct impacts towaterways. There are no reliable estimates of worldwide spillage rates.

Inland facilities regulated under the United States’ Environmental ProtectionAgency’s Spill Prevention, Control, and Countermeasures (SPCC) programother than refineries and production wells, covered separately in these analyses,

TABLE 2.32 Estimated U.S. Oil Spillage from Gas Stations and Truck Stops

(ERC data)*

Year Annual Spillage (tons)

1980e1987 171

1988e1997 223

1998e2007 116

1980e2007 170

*Based on reported data reported to the relevant state and local authorities in the 50 U.S. states, as

well as data reported to federal authorities. These data do not include leaking underground storage

tanks that leak over long periods of time. These data are tracked separately and are not considered

emergency spill incidents. Since gas stations are regulated by the EPA, facilities spillage at these

facilities of at least 50 gallons (0.17 tons) that occur during these facilities are included. Smaller spills

(less than 50 gallons) are not included.

TABLE 2.33 Estimated U.S. Oil Spillage from Inland EPA-Regulated Facilities

(ERC data)

Years Annual Spillage (tons)

1980e1987 4,963

1988e1997 35,002

1998e2007 8,525

1980e2007 16,963


spill an average of 8,500 tons of oil annually, a 76% reduction since the decade1988e1997 (Table 2.33). Spills at inland facilities often go to pavements andother substrates, including secondary containments, reducing direct impacts towaterways. There are no reliable estimates of worldwide spillage rates.

Oil spillage from home-heating oil tanks, which are not regulated by theEPA unless the tanks are in sizes larger than 34 tons, amounts to 70 tons of oilannually, a slight decrease from the decade 1988e1997 (Table 2.34). Note thatthis does not include slow leakages from underground storage tanks. There areno reliable estimates of worldwide spillage rates from residential tanks.

Motor vehicles that carry oil as fuel rather than cargo spill about 285 tons ofoil annually in the United States, double that for the decade 1988e1997 (Table2.35). The spillage is associated with greater motor vehicle traffic, as well as

TABLE 2.34 Estimated Oil Spillage from U.S. Residential Heating Oil Tanks

(ERC data)

Years Annual Tons Spilled

1980e1987 26

1988e1997 74

1998e2007 71

1980e2007 59

TABLE 2.35 Estimated U.S. Oil Spillage from Motor Vehicles (excluding

tanker trucks) (ERC data)

Year Annual Tons Spilled

Average 1980e1987 39

Average 1988e1997 170

Average 1998e2007 295

Average 1980e2007 168


better reporting by local authorities that are often the emergency responders.Motor vehicle spills* often go to pavements and do not directly impactwaterways. Since the data only include spills of less than 1 ton, most passengervehicles are excluded. There are no reliable estimates of worldwide spillagefrom motor vehicles.

2.3.7.3. Spillage from Aircraft and Other Sources

Aircraft spill an estimated 50 tons of jet fuel annually to inland areas. These spillsgenerally occur at airports during fueling, or occasionally from an accident.Aircraft spill an additional 530 tons annually to U.S. marine waters, based ona 2003 NRC study.17 These spills occur from two sources: through the deliberatedischarge or jettisoning of jet fuel due to emergency conditions aboard an aircraft,or through the release of partially burned fuel in inefficient engines or operatingmodes.17,34 This type of spillage also occurs over inland areas, but there are no

*Note that tanker trucks carrying oil as cargo are considered separately.

TABLE 2.36 Estimated U.S. Oil Spillage (bbl) from Other Inland Sources

(ERC data)

Years Inland Aircraft (annual tons) Inland Unknown (annual tons)

1980e1987 2 138

1988e1997 23 314

1998e2007 49 74

1980e2007 26 190


current estimates of these inputs. Total aircraft input in the United States isestimated to be about 580 tons of oil annually. The 2003 NRC study estimatedworldwide marine inputs from jettisoned aircraft fuel to be about 7,500 tonsannually.17 Average annual spillage from aircraft and miscellaneous unknown(unidentified) inland sources in the United States is shown in Table 2.36.

2.3.7.4. Oil Inputs from Urban Runoff

About 50,000 tons of oil enters U.S. marine waters each year through urbanrunoff, based on a 2003 NRC study.17 Urban runoff is the accumulation ofdrops of oil that leak from automobiles, trucks, and other vehicles, as well assmall chronic spillages that occur from other land-based sources. Oil washesoff into storm sewers, culverts, and other waterways into streams and rivers thatenter marine waters. Because the exact spillage source cannot be pinpointed, itis termed “nonpoint source” pollution. The U.S. inputs are broken down byregion in Table 2.37. Studies that included worldwide estimates of oil in urbanrunoff are shown in Table 2.38.

TABLE 2.37 Estimates of U.S. Oil Inputs from Urban Runoff

Region Estimated Average Annual Tons of Oil Input*

Atlantic 31,500

Gulf of Mexico 12,600

Pacific 5,829

Alaska 80

Total 50,009

*Estimates based on analyses in the NRC 2003 study.17

TABLE 2.38 Estimates of Worldwide Marine Oil Inputs from Urban Runoff

Study

Estimate of Average Annual Oil Inputs from Urban Runoff

(tons)

1970s 1980s 1990s

NRC, 1975 2,500,000 e e

Kornberg, 1981 2,100,000 e e

Baker, 1983 e 1,430,000 e

NRC, 1985 e 1,080,000 e

NRC, 2003 e e 140,000


2.3.8. Oil Inputs from Potentially Polluting Sunken Shipwrecks

Potential future and documented current oil leakage and discharges fromsunken ships in marine waters is an issue of concern worldwide. A studyconducted in 1977 drew attention to the oil discharges from a large number ofoil tankers sunk during military operations in World War II along the U.S.western, eastern, and southern (Gulf of Mexico) coasts.18 While the tankers hadbeen sunk over 30 years earlier, oil was still periodically leaking from thevessels, which were acting as “seeps.” Many of the tankers were still relativelyintact, though their structural integrity was uncertain.

The issue of oil pollution from sunken World War II tankers and militaryvessels was further brought to public attention after several incidents of oilleaking from several vessels (notably the S.S. Jacob Luckenbach off the Pacificcoast of the United States, the USS Mississinewa in Micronesia, and theGerman warship Blucher off Oslo, Norway) in the late 1990s to 2004. Thesesunken vessels were identified as the sources of “mystery spills” anddischarges that impacted shorelines and other resources.35 The South PacificEnvironment Programme (SPREP) has conducted surveys of wrecks in theSouth Pacific region particularly impacted by World War II military vesselsinkings.36,37

In 2005, the American Petroleum Institute and the sponsors of the Inter-national Oil Spill Conference* commissioned a study, Potentially PollutingWrecks in Marine Waters, which involved developing a databasey of recorded

*International Maritime Organization, U.S. Coast Guard, U.S. Environmental Protection Agency,

International Petroleum Industry Environmental Conservation Association, Minerals Management

Service, and National Oceanic and Atmospheric Administration.yThe proprietary database was developed by ERC.

FIGURE 2.7 Approximate location of potentially polluting shipwrecks* (ERC data).


vessel sinkings for tankships of at least 150 gross registered tons (GRTs)carrying oil and nontank vessels of at least 400 GRTs that carried oil as fuel/bunkers (and for operations); an analysis of the distribution of and likelyamount of oil contained in these vessels; and an examination of the environ-mental, regulatory, political, technical, and financial issues associated withthese sources of petroleum.38 The data analysis revealed that there were at least8,569 recorded vessel sinkings worldwide, of which 1,583 were tankships and6,986 were nontank vessels. An estimated 2.5 to 20.4 million tons of oil isthought to be present in these shipwrecks. The shipwrecks are distributedthroughout the world, as shown in Figure 2.7. The data in the 2005 Michel et al.study were analyzed regionally, as summarized in Table 2.39.38

This oil will not necessarily discharge, but there is the potential that it will,with the actual probability of discharge depending on vessel integrity andcondition, age, depth at which the wrecks rest, temperature of the waters, andtype of oil. Heavier fuels at greater depths may be nearly solid, and many of thevessels may be largely intact. On the other hand, the greatest potential forspillage is with the older vessels, particularly those from World War II, whichwere often built according to lower standards than more modern vessels.

The potential for impacts depends largely on the location of the wrecks.Those in nearshore waters tend to present the greatest potential for impacting

*Dots indicate approximate locations based on Marsden square (10-degree latitude/longitude).

Because many of the vessels are “war-graves” and there are also safety concerns, authorities aim to

prevent plundering or diving exploration. The exact locations of many vessels are uncertain or are

classified or confidential.

TABLE 2.39 Worldwide Potential Pollution from Sunken Tankers and

Nontank Vessels (ERC data)

Region

Estimated Oil Content of Shipwrecks (tons)

Minimum Maximum

North Atlantic Ocean 951,000 7.5 million

South Atlantic Ocean 165,000 0.5 million

North Pacific Ocean 221,000 1.7 million

South Pacific Ocean 521,000 4.2 million

Indian Ocean 264,000 2.2 million


shorelines. The impacts of discharges from these vessels in the open ocean arelikely to be less severe than those closer to shore because of the naturaldispersion that would break the oil into smaller concentrations. Much of the oilinvolved is likely to be heavier and would most likely form tar balls rather thanlarger slicks unless released in a large mass. The experts who conducted the2005 Michel et al. study concluded that most of the vessels were likely torelease oil in small quantities over a longer period of time or had already startedto do so, acting almost as a “natural seep.” Nevertheless, there is the potentialfor a vessel to suddenly release a much larger quantity of oil if a radical changetakes place in the vessel’s structural integrity.38

The political, regulatory, and financial issues associated with these ship-wrecks are extremely complex due to jurisdictional concerns. Removing the oiland other hazardous materials, as well as munitions, from these vessels involvescomplex, dangerous, and expensive salvage operations. It is unclear who wouldfinance or regulate these operations, especially for the large number of WorldWar II vessels involved. Because of the complex issues presented by thesewrecks and the overwhelming number of potentially polluting wrecks, anapproach involving scientifically based risk assessments and cost-benefit anal-yses has been promoted by several organizations, government agencies, andresearchers to prioritize those wrecks that poset the highest environmental riskfor oil and hazardous material removal operations.38-44

2.3.9. Summary of Oil Spillage

Estimates of average annual U.S. oil spillage by decade from all sourcecategories are summarized in Table 2.40. Over the last decade, the largestsource category of spillage is inland pipelines, followed by EPA-regulatedfacilities. The oil spillage reported here does not reflect the amounts of oil

TABLE 2.40 Estimated Total Average Annual U.S. Oil Spillage (tons)

Source Type

1969e

1977

1978e

1987

1988e

1997

1998e

2007

% Total

1998e2007

Production 4,491 1,243 2,169 1,420 5.07%

Offshore Platform Spills 3,694 192 259 182 0.65%

Offshore Pipelines 640 495 1,161 373 1.33%

Offshore Supply Vessels 14 35 7 1 0.00%

Inland Production Wells 143 521 742 863 3.08%

Refining 429 502 2,145 1,734 6.19%

Refinery Spills 429 502 2,145 1,734 6.19%

Transport 69,809 43,092 27,250 13,770 49.16%

Inland Pipelines 37,049 25,885 16,900 10,965 39.15%

Tanker Trucks 429 698 745 1,312 4.68%

Railroads 286 332 309 204 0.73%

Tank Ships 27,499 8,607 6,028 514 1.83%

Tank Barges 4,547 7,570 3,269 776 2.77%

Storage andConsumption

16,932 13,887 39,789 11,088 39.58%

Nontank Vessels 714 969 402 229 0.82%

Other Vessels 2,123 939 900 595 2.12%

Gas Stations andTruck Stops

171 171 223 116 0.41%

Residential 21 26 74 71 0.25%

Inland EPA-RegFacilities*

4,286 4,963 35,002 8,525 30.43%

Aircrafty 529 531 552 578 2.06%

Coastal Facilities 8,889 6,112 2,151 604 2.16%

Inland Unknown 129 138 314 74 0.26%

Motor Vehicles 71 39 170 295 1.05%

Total 91,660 58,723 71,354 28,011 100.00%

*Excludes refineries, gas stations, and production wells.yIncludes aircraft in inland areas plus estimates of marine inputs (based on NRC, 2003).



that were contained or recovered. It also does not reflect the differencesbetween oil that is spilled directly into marine or freshwater systems and oilthat is spilled onto other surfaces, including containment areas around storagetanks in tank farms. The properties of the oil spilled (crude vs. refined, heavyvs. light) and the locations in which the oil spills (marine waters, inlandwaters, dry surfaces, wetlands, industrial zones) will largely determine theimpacts of these spills and should be considered in addition to the actualamounts of oil spilled.

Total U.S. oil inputs to marine and inland waters, including spills, runoff,and all operational discharges are shown in Table 2.41.

TABLE 2.41 Estimated Total Average Annual U.S. Oil Inputs (tons)

Source Type

1969e

1977

1978e

1987

1988e

1997

1998e

2007

% Total

1998e2007

Production 5,876 2,431 3,438 2,930 2.15%

Offshore Platform Spills 3,694 192 259 182 0.13%

Offshore Pipeline Spills 640 495 1,161 373 0.27%

Offshore Supply VesselSpills

14 39 7 1 0.00%

Inland Production WellSpills

521 742 863 705 0.52%

Produced Water 1,007 963 1,148 1,669 1.23%

Refining 35,963 52,758 68,910 55,915 41.09%

Refinery Spills 429 502 2,145 1,734 1.27%

Refinery Effluents 35,534 52,256 66,765 54,181 39.82%

Transport 69,882 43,084 27,163 13,864 10.19%

Inland Pipelines 37,049 25,885 16,900 10,965 8.06%

Tanker Trucks 429 698 745 1,312 0.96%

Railroads 332 309 204 278 0.20%

Tank Ships 27,513 8,607 6,028 514 0.38%

Tank Barges 4,547 7,570 3,269 776 0.57%

Tank Vessel OperationalDischarge

12 15 17 19 0.01%

Storage andConsumption

67,841 65,497 91,595 63,357 46.56%

(Continued )

TABLE 2.41 Estimated Total Average Annual U.S. Oil Inputs (tons)dcont’d

Source Type

1969e

1977

1978e

1987

1988e

1997

1998e

2007

% Total

1998e2007

Nontank Vessels 149 969 402 229 0.17%

Other Vessels 2,123 939 900 595 0.44%

Vessel OperationalDischarge

2,000 2,086 2,443 2,745 2.02%

Gas Stations and TruckStops

171 223 116 170 0.12%

Residential 21 26 74 71 0.05%

Inland EPA-RegulatedFacilities**

4,286 4,963 35,002 8,525 6.27%

Aircrafty 2 2 23 49 0.04%

Coastal Facilities(Nonrefining)

8,889 6,112 2,151 604 0.44%

Inland Unknown 129 138 314 74 0.05%

Motor Vehicles 71 39 170 295 0.22%

Urban Runoff 50,000 50,000 50,000 50,000 36.75%

Total 179,562 163,770 191,106 136,066 100.00%

**Excludes refineries, gas stations, and production wells.yIncludes aircraft in inland areas, plus estimates of marine inputs based on the 2003 NRC

study [17].


Although annual spill amounts vary from year to year, often due to one ortwo particularly large incidents, there has been a general downward trend inU.S. spills in the past decade, and an even greater downward trend since 1989,the year of the Exxon Valdez spill (Figure 2.8). Worldwide trends are shown inFigure 2.9. The large spill in 1979 from the Ixtoc I well blowout dominates thespillage. War-related intentional spillage, such as that in the 1991 Gulf War, hasnot been included.

Despite general downward trends in spills in the United States and world-wide, it is important that spill response preparedness be maintained due to thecontinuing risk of spills, including worst-case discharge scenarios. Most spillswill continue to be “routine” in that they are relatively small and easilyresponded to with local resources. At the same time, occasional large spills,along with increasing public expectations for effective spill response andincreased spiller liability, have necessitated complex contingency planning for

0

20,000

40,000

60,000

80,000

100,000

120,000

140,000

1968 1973 1978 1983 1988 1993 1998 2003

Tonnes

FIGURE 2.8 Annual oil spillage into U.S. waters with reduction trends (ERC data).

0

200,000

400,000

600,000

800,000

1,000,000

1,200,000

1,400,000

1,600,000

1,800,000

2,000,000

1970 1975 1980 1985 1990 1995 2000

Tonnes

FIGURE 2.9 Worldwide oil spillage with reduction trends (ERC data).


increasingly rare high-impact events.22 For example, the United States with itsexperience in the 1989 tanker Exxon Valdez, which involved the spillage of over37,000 tons of oil, has not experienced a worst-case discharge scenario, definedas the complete release of the contents of a fully loaded oil tanker or largestorage facility. Had the Exxon Valdez released its entire contents, about fivetimes as much oil would have spilled into Prince William Sound. Thecomplexity of the spill response and the impact of the spill is difficult toenvision, but must be planned for. The magnitude of the spill from the MC-252


well (otherwise referred to as Deepwater Horizon spill) that occurred duringApril through July 2010 has not yet been verified, though it has been beenconfirmed to be the largest spill in US history.

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