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648,

surface layer of the atmosphere over land, dispersion of the plume is greater,
ut can yield higher particulate levels at the ground due to vertical transport.
This is seen at downwind distances greater than 10 km. However, for both
runs, concentrations of smoke particulate were well below 100 g/m, from the
source out to 20 km downwind over land.

DISCUSSION

‘Tampa B° is the seventh largest port in the United States, handling an average
of 4 billion gallons of petroleum and related products annually. With over

20 piloted vessel trips per day, oil-spill responders should have access to as
many tools as possible. In situ burning at sea has been demonstrated to be an
effective oil-spill response method.

In situ burning is a relatively simple technique. For an excellent review of
burning as a response technique, see Shigenaka and Barnca, 1993.(11)
However, to be effective, at-sea burning of oil will probably have a short
window of opportunity in which the oil composition and thickness, wind, and
sea conditions must all be within certain parameters. It is crucial that spill
responders have the authority and political backing to make quick decisions to
take advantage of this time window. This would involve having rapid access
to standardized fireproof boom, vessels, and appropriate training in operations
and safety. Also, weather conditions would be monitored, and the public
should be advised on smoke plume trajectory and content.

‘The extent to which inhalation of fine particulates presents a human health
hazard during an in situ burn depends on the concentration and duration of
exposure. These very small particulates do not settle readily and will be
carried by prevailing winds {* long distances, over which their concentrations
will rapidly decline. However, public perception may be that smoke plumes
pose an unacceptable risk to human health. When compared to the damage
that beached oil has been shown to cause, as in the Tampa Bay spill, the
alternatives are put in perspective.

ACKNOWLEDGEMENTS

Appreciation is extended to David Evans at NIST, George Henderson at
Florida Department of Environmental Protection, Jeff Lankford at HAZMAT,
and Eileen Lear at MMS for their help with this paper.

REFERENCES
1) World Information Systems, "Major Fire and Spill Following Collision off

"Tampa," il Pollution Bulletin, Vol. V, No. 18, pp. 1-4, (August 13,
1993).

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639

By August 13, the oil had begun to mors widely distribute itself (Fig. 3),
becoming patchy with slicks spread over very large areas and picking up water
i Content estimated at about 50 percent. At this Point, burning may have

} become more difficult due to emulsification, After August 13, the winds

i changed to out of the west and the oil began to move ashore. Figure 4 shows
the path of a Minerals Management Service (MMS) “oil-following" surface

i On August 14, tarballs began coming ashore. In the next few days, most of
! the offshore oil had beached, was carried into and through tidal inlets, or was
| in the nearshore areas (Fig. 5). ‘This secondary oil (following the tar balls

: ashore) had been in the streamers described above and, therefore, might have
! been reduced in volume if offshore burning had been available as a response

i tool.

Before the wind shifted to onshore, spill response was mainly a skimming

i Operation. After oil came ashore, response concentrated on beach cleanup.

: Overall, the response went well in terms of cleaning up a large quantity of oil
and rapidly mobilizing people and equipment. The total amount of oil
recovered was estimated at over 147,000 gallons in offshore skimming
Operations and more than 130,000 gallons of oil/water mixture in inshore
operations. (4)

IMPACTS TO COASTLINE

Tampa Bay is Florida’s largest open-water estuary. Popular for sport, tourism
i and recreation, the bay Supports one of the world’s most productive natural
systems. Nursery grounds are present for young fish, shrimp and crabs.
These include grouper, pompano, Gulf Whiting, redfish, shrimp, crabs,
Sysrers, clams, scallops, snook, tarpon, flounder and mullet.(5) "As many as

coastline.

i
1

i Asa result of the spill, fish and wildlife resources and their habitats in the

| St. Petersburg Beach area, Boca Ciega Bay and lower Tampa Bay were

j adversely affected. No. 6 fuel oil is a viscous, heavy molecular weight oil of
j moderate toxicity and is extremely persistent when spilled into protected,

: Poorly-flushed ecosystems, The estimated areas of affected habitat included

i about 6 acres of mangroves, which contain one active brown pelican and one

; Wading bird rookery. Also affected were approximately 14.5 miles of sand

H beaches, 2.5 acres of submerged seagrass beds, and 1.3 acres of salt marsh.(5)

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644

concern, especially in vicinities of aged populations with attendant respiratory
problems, Research programs have been designed to study how burning large
spills would affect air quality by quantifying the products of combustion and
developing methods to predict the downwind airborne smoke particulate
concentrations. (8)

NEWFOUNDLAND OFFSHORE BURN EXPERIMENT (NOBE)

A consortium of over 25 agencies from Canada and the United States
conducted two experimental burns offshore Newfoundland on August 12, 1993
(coincidentally 2 days after the Tampa Bay spill). Each experiment involved
the release of about 50 tons of Alberta sweet crude oil into a fireproof
boom.(9) Each burn lasted over an hour and was monitored for emissions and
physical parameters. Over 200 sensors and samplers were employed, and the
data return exceeded expectations. Overall, the experiments indicated that
burning oil at sea is a feasible and practical oil-spill countermeasure.

Data analyzed to date show that emissions from the bums were low. Beyond
about 150 m from the fire, all compounds and parameters measured were
below health concern levels, and very little material of any type was detected
beyond 500 m. Particulates in the air were measured by several means and
fond to be minimal beyond 150 m downwind at sea level. No respirable
particles (less than 10 micrometers in size) were detected at ground level.
Volatile organic compounds (VOCs) in the smoke plume were, nevertheless,
Jower than those emitted from the non-burning spill.(9)

‘The two bums left a total of about 0.5 m? of oily residue, which is less than

1 percent of the volume of oil released. ‘Thus, burn removal approached
99-percent efficiency. The residue resembled a highly weathered oil and was
generally lighter than water. No toxic compounds were found in the water
samples taken directly beneath the burning oil, nor from later toxicity tests
using those samples. ‘The performance of the fireproof boom indicated a need
for further research on at-sea burns.

SMOKE PLUME MODELING

Since 1985, the National Institute of Standards and Technology (NIST),
supported by MMS, has studied in situ burning of crude oil to provide
information in support of oil-spill response. Along with development of smoke
plume measurement techniques, NIST has developed a Large Eddy Simulation
(LES) model for calculating smoke plume trajectories and estimating the
“footprint” of soot particle deposition downwind of a burn.(10) The model
was designed to differ from other (typically smokestack) models by
encompassing larger sizes and types of combustion sources.

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641

Ocean 255 Incident

Overflight Map 15 AUG 93, 1600-1705
Prepared by NOAA Platform: NOAA Bell 212

Observers: Galt, Lankford, Benggio
USE ONLY AS A GENERAL REFERENCE (NOAA)

Z| i
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&
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q Shoreline impact}
an :
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Z| MSO Tampa Area
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a z
3
§
Z|
BI
&
sow OW SW SW
Overflight 08/15 1600

Figure 4. Movement of satellite-tracked drifter deployed near large
slicks, from August 13-15. 1993

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640

Ocean 255 Incident

Overflight Map Date/Time: 13 AUG 93, 0700-0820
prepared by NOAA, Platform: NOAA Bell 212

Observers: Galt, Lankford, Hall
USE ONLY AS A GENERAL REFERENCE (NOAA); Ross (U. of Miami)

Ten
Binueeeal
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: er
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&
Wind 8 kts|
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|
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Approximate ‘Additional detail inside
Senay edge “Tampa Bay avalsbe on
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4|— : a _— Response Plan
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Anna Ye
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Overflight 08/13 0700 oH

Figure 3. Spill overflight map for August 13, 1993

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643

All of the affected habitats function as nursery areas for recreationally and
Commercially important finfish and shellfish species.

During the spill and cleanup, numerous species of migratory, shore, and
wading birds were affected and their habitats disturbed. Bird rescue efforts
ace, “ed for the recovery of 357 oiled birds, with 80 mortalities.(5) A total
Of fi sea turtles were known to have been exposed to oil. ‘These included
four loggerhead hatchlings, a threatened species, which were beginning to
cinerge from nests on the beaches around Egmont and Mullet Keys at the time
t of the spill. Ninety-six of the 115 known loggethead nests were on beaches
that could have been potentially affected by the spill. Twenty-nine of these
nests hatched turtles during the spill response and had to be protected,

} Ongoing studies are documenting the effects of the spill on surf-zone fishes,
Seagrass finfish and invertebrates, and larval fish.(5) Mortality to crab and
oyster larvae and larval/juvenile fish in the tidal passes and channels ig also a
Sra Several areas of sunken oil were observed in the subtidal areas just
off Treasure Island beaches, and also in seagrasses, mud flats, the
{nira-Coastal Waterway and are likely in deeper areas of Boca Ciega Bay. In
October 1993, Treasure Island beaches were te-exposed to oil from this
benthic source, requiring additional cleanup of those areas. (5)

: POTENTIAL OF OFFSHORE BURNING
The use of in situ burning as a spill response measure has several advantages
over other methods. Large amounts of oil on the water can be converted
rapidly to small amounts of residue with a small percentage of smoke
Particulate yield. By removing the oil before it spreads, burning can reduce
shoreline contamination with its attendant damage to sensitive environmental
resources.

Burning also requires far less equipment and labor than other techniques. For
Srample, the response to the Tampa Bay spill included removing over

33,000 cubic yards of oiled sand and solid waste, representing over

2,000 dump truck loads.(6) Other equipment used included 12 vacuum trucks,
87 heavy equipment vehicles, 62,000 feet of boom, 14 barges, 10 skimmers,

stress. (6)

Buring oil spills produces a visible smoke plume containing particulates and
ether products which may persist far downwind from the burn. A human
health risk may result from inhalation of the fine particulate material that is
Produced as a byproduct of combustion. Public health is therefore a prime

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Reprinted from: Proceedings of 17th Arctic and Marine Oil Spill
' Program (AMOP) Technical Seminar, Vol. I, June 8-10, 1994,
Vancourver, British Columbia.

| 1993 SPILL OFF TAMPA BAY, A CANDIDATE FOR BURNING?
by

Robert P. LaBelle', Jerry A. Galt?,
Edward J. Tennyson', Kevin B. McGrattan?
1. U.S. Minerals Management Service, Herndon, VA.
2. National Oceanic and Atmospheric Administration, Seattle, WA.
3. National Institute of Standards & Technology, Gaithersburg, MD.

ABSTRACT
On August 10, 1993, the Tank Barge Ocean 255 and the Tank Barge Bouchard
B-155 collided with the freighter Balsa 37 near the entrance of Tampa Bay,
Florida. Jet fuel from the Ocean 255 caught fire and bumed for approximately
18 hours. Barge B-155, carrying 5 million gallons of No. 6 fuel oil, ruptured
a port tank and spilled an estimated 328,000 gallons. Much of the discharged
oil was initially carried offshore by winds and tidal currents and moved
northward, parallel to the adjacent barrier island beaches.

By August 14 and 15, a storm system bringing winds from the west pushed oil
onshore onto several beaches and into and through tidal inlets. Subsequent
oiling of sand beaches, shallow embayments, and fringing wetlands occurred
during the second week of the spill event. Estimates are that about 14.5 miles
of sand beaches were oiled, along with approximately 6 acres of mangrove
wetlands, 2.5 acres of seagrass beds, and 1.5 acres of saltmarshes. Areas of
submerged oil were also present in bays and bay passes.

This paper outlines the general behavior and movements of the spilled oil and
the sea and weather conditions prevalent before the oil moved ashore. ‘The
possibility of removing portions of the spill by ignition and combustion is
discussed, and results of smoke plume model runs are presented. Given the
highly successful in-situ test burning of spills off Newfoundland in August
1993, this response measure deserves serious evaluation in future emergencies.
Presently, spill responders must consider both actual and publicly perceived
hazards associated with the at-sea burning of oil.

INTRODUCTION
The premise of this paper is that in situ burning of offshore oil spills is now
feasible and may be preferable, in some cases, as an oil-spill response tool.
Given advances in technology and research, coupled with recent successful
large- scale experimental burns, this tool should now be made more available
to spill responders. As a hypothetical example, the 1993 oil spill off Tampa
Bay was examined. Weather and sea conditions were quite favorable for

tu burning of large portions of the slicks for a period of 2 days after the
ill. This response method would have reduced the volume of oil that

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TAMPA BAY SPILL SCENARIO 1

646

Wino SPCC 4.0 m/e
aH STANO.OCY. 3.

WOAT LOADING 335. ww
MASS LOADING 1.20 4g/+

TENPCRATURE PROFLE |... __ROSSWINO CONCENTRATON AT_5. KLOUETERS
E1000 E1000
E800 E800
2 400 3 400 3004
4 4
Sa RE a a
‘arturin ) etnies row exon fo

VERTICAL CENTERLINE CONCENTRATION

ras
| | as
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SOs 5 9500 p5q_-—~
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DOWNWIND DISTANCE (Kem)

GROUND LEVEL CONCENTRATION

10
DOWNWIND DISTANCE (4m)

GROUND CENTERLINE CONCENTRATION

100
Gove |
8 iy 3 10 1s 20
own OSTANEE em)
Figure 6. Summary of the Large Eddy Simulation (LES) model run for a

simulated spill of fuel oil no. 6 off Tampa Bay, scenario 1
(all concentrations expressed in units of pg/m?)

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645

The LES model has shown that smoke production from crude oil fires varies
with the area of the burn and the type of crude oil. It appears that 10 to

15 percent of the mass of crude oil burned in large areas is converted to
particulates that are carried in the smoke plume. A comprehensive evaluation
of many burn scenarios for the state of Alaska (10) showed that for a
465-m? burn (800-900 megawatts), the 150 yg/m? one-hour-average smoke
particulate concentrations were not found at distances greater than 5 km
downwind of the bum at ground level and did not extend beyond a width of
1 km. (The level of the national primary and secondary 24-hour ambient air
quality standards for particulate matter is 150 ug/m?, 24-hour-average
concentration; ref: 40 CFR, S. 50.6(a).)

The LES model was run for two scenarios of hypothetical oil spill bums of
portions of the spill of fuel oil No. 6 off Tampa Bay. Both runs modeled
bums in the confines of a fireproof boom at the rate of 40 m’/hr. The fraction
of fuel that was converted into particulate matter, or smoke yield, was assumed
to be about 13 percent, based on previous work and the NOBE burns.

The model runs were based on actual slick locations (Fig. 2) and weather
conditions observed on August 11 and 12, 1993, offshore Tampa Bay. The
first run assumed a U.S. standard daytime temperature lapse rate of
-6.5°C/km, an onshore wind speed of 4 m/s, and lateral and vertical wind
fluctuations over water of 3‘and 1°, respectively; and over land of 10°and 6°.
Wind fluctuation values were hour-averaged standard deviations which
correspond to clear, sunny conditions. The smoke plumes were generated over
water, but were assumed to blow over land 10 km away.

The second model run corresponded to stable meteorological conditions with a
lapse rate of 0° C/km (isothermal profile), an onshore wind speed of 7 m/s,
and wind fluctuations identical to the first run. These conditions were similar
to those prevalent during the NOBE burns.

Figures 6 and 7 give summaries of each calculation. (Note difference in scale
when making comparisons.) The figures show the temperature profile assumed
and the crosswind extent of hour- averaged plume particulate concentrations of
50, 150, and 300 yg/m’ at a plume cross section 5 km downwind of the bun
site, The two runs showed 50 g/m? contour widths of about 1.5 and 1.0 km,
respectively, which is on the order of the width of visible smoke plumes at
sea. Also shown are downwind extents of those concentration levels in the
plume. Note that Figure 6 shows a “hole” along the centerline of the plume,
which appears as a gap in the conce‘ration contours. This is due to the
generation of two counter-rotating vortices which entrain most of the
Particulate matter sent aloft. This phenomena was also observed during the
NOBE bums.

The figures also display concentrations at ground level (first 10 to 20 m of the
atmosphere) downwind from the bum, Because of increased mixing in the

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Ocean 255 In

Johns Pass

prepared by NOAA Platform: NOAA Bell 212
Observers: Galt, Lankford, Michel

(NOAA); Harbert (USCG OSC)

USE ONLY AS A GENERAL REFERENCE,

Johns Ovflt.081593.0704

Figure 5. Spill overflight map for August 15, 1993

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649

2) National Oceanic and Atmospheric Administration, Information
Managem : 155 Oil Spill Tam: ri
August 10, 1993, for the Hazardous Materials Response and
Assessment Division, Seattle, WA, Sept. 10, 1993.

3) Simecek-Beatty, Debra A., is il i
Drifters, A Compatien Proc, 2nd reals Conf. on Remote Sensing
for Marine and Coastal Environments, New Orleans, LA, Vol I, pp.
423-434, Jan. 31-Feb. 2, 1994,

4) Cutter Information Corp., "Crews Wrap Up Cleanup Activities in Tampa

Bay,” Oil Spill Intelligence Report, Vol. XVI, No. 36, pp. 2-3,
(Sept. 16, 1993).

5) U.S. Department of the Interior, National Oceanic and Atmospheric
peministation, and Florida Dept. of Environmental Protection,

tis iT
Bay Flora Oi! Spill, 1993.

World Information Systems, "Cleanup Force Peaks at 1,800 After Tampa
Bay Collision,” Qil Pollution Bulletin, Vol. V, No. 11, pp. 6-7,
(Sept. 10, 1993).

6)

7

Cutter Information Corp., "Responders Continue to Clean Up Oil from

‘Tampa Spill,” Oil Spill Intelligence Report, Vol. XVI, No. 32, p. 3,
(Aug. 26, 1993).

8)

Evans, D., W. Walton, H. Baum, et al. In-Situ Burning of Qil Spills:

Mesoscale Experiments, Proc. 15th AMOP Tech. Seminar, June 1992,
Edmonton, Canada, pp. 593-657, 1992.

Newfoundland Burn Experiment Committee, Newfoundland Offshore Burn
Experiment, NOBE Facts Newsletter, Vol. 6, March 1994.

9)

10) McGrattan, K., A. Putorti, W. Twilley, D. Evans, Smoke Plume
Trajectory from In Situ Burning of Crude Oil in Alaska, NISTIR 5273,
National Institute of Standards, Gaithersburg, MD., 1993.

11) Shigenaka, G. and N. Bamea, Questions about In-Situ Burning as an
W: i ill Ri nse Technique, HAZMAT Report 93-3,
Seattle, WA., 42 pp., June 1993,

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637

Ocean 255 Incident

Overflight Map 2 IQAUGS3 1635,
pared by NOAA
popes Observers: LCDR Bengglo
apc does no eplt prose
verover st acetat emaenc SacI atte
a

aan ———
Henry iridescent dul slo
tnd cal patches of emulsibed ol
(Colors giden ren be,
purple, ome grey. Appears
Simos ly

‘Thick black and tridescent patches]
of emulsified oll basleally follows
channel ~7run west of Egmont Key
about 3 miles wide

(sting an

aw ew
OVFLT 08/10 1835

Figure 1. Spill overflight map for August 10, 1993

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636

eventually came ashore, thus reducing impacts. In this case, smoke plume
modeling indicates minimal risk to coastal populations from particulate
deposition if such burns had taken place. However, public perception of risks
inherent in burning oil must be acknowledged and addressed.

SPILL EVENT AND BEHAVIOR
On August 10, 1993, the outbound freighter Balsa 37 collided with two
inbound barge-tug combinations in Tampa’s main shipping channel, about

2.5 miles west of the Sunshine Skyway Bridge.(1) The barge Ocean 255,
carrying jet A fuel, suffered an explosion and fire that was finally extinguished
early the next day, The Balsa 37 was intentionally grounded southeast of
Egmont Key. The remaining barge, the Bouchard B-155, spilled an estimated
328,000 gallons of No. 6 fuel oil from its ruptured No. 1 port tank. A rapid
transfer of the fuel oil from the ruptured tank helped to minimize the amount
spilled.

Although some oil washed ashore on Egmont and Mullet Key, winds and
currents carried most of the spill out into the Gulf of Mexico (Fig. 1) in long
streamers along surface convergence lines.(2) An August 11 spill overflight
showed the oil in a 17-mile slick initially heading west and slightly north
(Fig 2). The winds, as shown in Table 1, were generally light and in the
offshore direction over August I1 and 12th. Thus, conditions were excellent
to boom and bum oil all along the distribution about 7 or 8 miles offshore.

Table 1. Wind Data for Tampa Spill
(NOAA/Hazardous Material Response Branch)
Observation Point Time Direction | Speed
Date ceEDT | _(From)_|_ (Knots)
St. Petersburg Airport | 8/11/93 0500 140 7
8/12/93 0500 CALM | CALM
8/13/93 0500 CALM | CALM
8/14/93 0500 179 5
8/15/93 1300 w 9
‘Tampa Bay, Tampa 8/14/93 0500 CALM | CALM
8/15/93 1300 Wsw 9
Sunshine Skyway 8/12/93 0500 ENE 15
(Bridge) 8/12/93 1500 wsw 5
8/13/93 1500 w 5
8/14/93 1212 SSE 9
8/15/93 1315 w 12
West of Egmont Key 8/11/93 2000 NW 9

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647

TAMPA BAY SPILL SCENARIO 2 WeAT LOADING 338. sow

wos tome cae
TewperaToRe prorite CROSSWIND CONCENTRATION AT _ 8. KLOMETERS
too seo
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‘OOWNWIND DISTANCE (Km)

Figure 7. Summary of the Large Eddy Simulation (LES) model run for a
simulated spill of fuel oil no. 6 off Tampa Bay, scenario 2
(all concentrations expressed in units of g/m?)

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