TABLE E-18 Summary of Average Total Load from Accidental Spills during Years 1990-1999, for Vessels in U.S. Waters by Type of Vessel and by Type of Oil (tonnes)

 

Tankers

Tank Barges

Other Vessels

Totals

% of Total

Crude oil

16,525

1,184

162

17,872

36%

Gasoline

187

1,459

50

1,697

3%

Light distillate

545

5,466

6,247

12,259

25%

Heavy distillate

2,340

12,556

2,651

17,546

36%

TOTALS

19,597

20,665

9,110

49,373

 

(Percent of total)

40

42

18

 

 

incompleteness of the data and the fact that the smaller spills, under 10,000 gallons (34 tonnes), comprised about 13 percent of the U.S. totals, the international spill quantities were increased by 25 percent to obtain the minimum estimate, by an additional 10 percent to obtain the best estimate, and further increased by 25 percent to obtain the maximum estimate. Results are summarized in Table E-21.

Accidental Spills from Vessels Worldwide

The North American and international spill estimates are combined to provide worldwide estimates (Tables 2-2 through 2-6). The best estimate for total spillage worldwide is 110,000 tonnes (30 million gallons) per year. The 1985 report (National Research Council, 1985) and the 1990 study (IMO, 1990) both used data from the International Tanker Owners Pollution Federation Ltd. (ITOPF) to estimate the quantity of oil entering the marine environment from tanker accidents. In the 1990 study, the spillage was averaged for the 10-year period from 1981 to 1989, establishing an annual average of 114,000 tonnes per year. In the 1990 report no adjustments were made for the deficiencies in the database, so care should taken when comparing these figures.

Inputs To The Sea From The Aircraft Industry

There are inputs to the sea from deliberate and continual releases of fuel from aircraft. There are two sources: deliberate discharge due to emergency conditions aboard the aircraft, and normal operation releases including the release of partially burned fuel in inefficient engines or inefficient operating modes and emptying of fuel injection bypass canisters. Modern aircraft have take-off weights exceeding their landing weights, sometimes by as much as 150 tonnes. For example, a 747 can carry as much as 220,000 L of fuel weighing about 175,000 kg or 175 tonnes. If a fully laden 747 jettisoned its fuel because it was required to return to an airport, it could dump as much as 150 tonnes of the fuel to enable it to land safely. Fuel dumping is infrequent but not rare. One airport reported on 16 fuel dumps in one year out of 7,000 flights conducted [Canadian Environmental Assess

TABLE E-19 Summary of Average Annual Loads from Accidental Spills (for Vessels in North American Waters)

 

Tank Vessels (gallons)

Other Vessels (gallons)

All Vessels (gallons)

Tank Vessels (tonnes)

Other Vessels (tonnes)

All Vessels (tonnes)

Spill Volume—U.S. Waters (per year)

1,089,173

252,013

1,341,186

4,026

911

4,937

Est. Spill Volume—Canada (per year)

100,000

38,000

138,000

384

137

521

Est. Spill Volume—Mexico (per year)

170,000

15,000

185,000

631

55

686

 

1,359,173

305,013

1,664,186

5,042

1,102

6,144

 

Tank Vessels

Other Vessels

 

 

(gallons)

(tonnes)

(gallons)

(tonnes)

 

North American Waters

Minimum (based on 1990’s data)

1,400,000

5,000

300,000

1,100

 

 

Best Estimate (1990’s data + 5 percent)

1,400,000

5,300

300,000

1,200

 

 

Maximum (Best estimate + 20 percent)

1,700,000

6,400

400,000

1,400

 

 

NOTE: All totals rounded to two significant figures.



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