Oil Tracking, Containment, and Recovery During the Exxon Valdezresponse

OIL TRACKING, CONTAINMENT, AND RECOVERY DURING THE EXXON VALDEZ RESPONSE

Jere A. Noerager Downloaded from http://meridian.allenpress.com/iosc/article-pdf/1991/1/193/1742936/2169-3358-1991-1-193.pdf by guest on 02 October 2021 Exxon Production Research Company P.O. Box 2189 Houston, Texas 77252

Ron H. Goodman Esso Resources Canada, Ltd. 3535 Research Road N.W. Calgary, Alberta T2L 2K8, Canada

ABSTRACT: The initial response to the Exxon Valdez oil spill, in Equipment mobilization Prince William Sound, Alaska, March 24,1989, was to locate, contain, and recover free oil on the open water before it reached the shoreline. Immediately following the grounding, Exxon undertook a massive Mobilizing the necessary equipment and materials was a major chal- mobilization of equipment for the containment and recovery of the lenge. Oil was tracked primarily by airborne observers supplemented by spilled oil. Strenuous efforts were also made, successfully, to prevent remote-sensing devices; the immediate generation of maps showing the the release of almost one million barrels of crude oil remaining in the oil's location was a critical component in the initial response. Free oil was grounded tanker. Additionally, preparations were made to disperse or contained mainly by the placement of booms of various designs and burn the crude that had been released. Although we discuss below only manufactures in crucial locations. Ultimately, more than 100 miles of the containment and recovery procedures, more than half of the equip- containment boom were used for this purpose. After containment, oil ment mobilized by Exxon in the first days after the spill was for was removed by skimmers and other devices from the water's surface. lightering and dispersing or burning activities. Additional equipment was needed to transfer the recovered oil from the The first sources contacted for oil spill response equipment were the skimmers to temporary storage, where it was held pending final dis- Alyeska Pipeline Service Company (Alyeska) and four oil spill cooper- posal. This paper presents the details of the tracking, containment, and atives: Alaska Clean Seas, Clean Bay, Cook Inlet Response Organiza- recovery operations, with comments on how well various types of equip- tion (CIRO), and Oil Spill Response Ltd. (OSRL). Their resources ment performed. were soon augmented by those of other cooperatives, state and local governments, and commercial manufacturers. Several countries outside the United States provided resources as well: Canada, Denmark, England, Finland, Sweden, Norway, and the Soviet Union. All equipment from foreign countries, however, required customs clearance. Some of the self-propelled skimmers (such as the French Egmopol skimmers) were considered foreign-hulled vessels under the Jones Act and required special waivers to be used in After the Exxon Valdez went aground in Prince William Sound on the cleanup. Some foreign skimmers with onboard storage were not March 24, 1989, Exxon's immediate response was to contain and approved by the U.S. Coast Guard (USCG), since they had not been recover the free oil from the open water. The response quickly became through the marine inspection process. Furthermore, mechanical sys- the largest such operation ever conducted. The major aspects of the oil tems from Europe were not always compatible with U.S. hydraulic tracking, containment, and recovery operations are discussed below, fittings and had to be modified. organized under the following headings: Nearly all of the early response equipment was delivered by air. • Equipment mobilization (sources of equipment and delivery logis- Nonstop jet flights to Anchorage were possible from the West Coast, tics for the initial response) but most flights from Houston required a stop for refueling and either a • Oil tracking (aerial surveillance, oil detection instrumentation, crew rest period or a replacement crew. and spill trajectory forecasting) The Valdez airport has a 6500-foot runway, which cannot handle • Oil containment (equipment used and operations undertaken to aircraft larger than a DC-6 or C-130. As a result, most large air cargo contain oil for recovery and to protect environmentally sensitive shipments arriving in Anchorage were transferred to smaller planes for areas) delivery to Valdez. • Oil recovery (equipment and operations involved in recovering oil Extensive marine and air support were needed for boom and skim- on the surface of the water and transferring it to temporary storage mer operations. The spill location required that recovery vessels and until disposal) personnel remain at sea rather than returning to port to offload recovered oil and replenish supplies. Exxon made extensive use of the many small fishing vessels in Valdez and other ports in the area. However, mobilization of large vessels for storing recovered oil or deploying large booms took days or even weeks, since few were locally available. Some 1. Mention of trade names or commercial products does not constitute came from within Alaska, but many vessels, such as large barges, came endorsement or recommendation for use. from out of state. 193 194 1991 OIL SPILL CONFERENCE

Oil tracking Tracking and mapping operations. Exxon, the USCG, the National Oceanic and Atmospheric Administration (NOAA), and the Alaska Spilled oil was tracked from its origin at Bligh Reef through Prince Department of Environmental Conservation (ADEC) conducted reg- William Sound and into the Gulf of Alaska. The primary function of ular aerial oil spill tracking operations. Data from these flights were this surveillance was to provide a basis for planning the overall deploy- shared, and NOAA summarized the information on computer-drawn ment of resources in order to minimize the effects of the spill. maps (see Figure 1).

EXXON Twin Otter overflight Goodman/Sikstrom 145·

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59·40.7* N 149· 08.3V/ 59· 49.5'N 1 48· 19.2W

Figure 1. A spill observation map produced by NOAA on April 1, 1989 CLEANUP OPERATIONS 195

Exxon's aerial tracking of the spill began on March 25 and continued NOAA's On-Scene Spill Model (OSSM). It used forecasts of ocean with two or three flights a day for the first month. Usually, there was a currents and wind speeds to predict spill movement. However, uncer- flight at dawn that located heavy concentrations of oil; these observa- tainty in the forecasts of winds used as input data limited the accuracy tions were presented at the morning operations planning meeting. of the OSSM predictions; the results were therefore not used as a basis Then a midday flight might be conducted to verify reports of oil at for daily deployment of oil recovery equipment. On the other hand, if various locations. A final flight was made before dusk to determine the the expected range of currents and wind speeds were entered, OSSM direction that the spill had taken during the day. Exxon's regular aerial could be used to estimate the likelihood and the time that the spill tracking of the spill in Prince William Sound ended in mid-April, by would reach a specified location. The system was especially useful in which time most of the free oil had moved out of the Sound. Regular reassuring residents of nearby communities and in justifying the alloca- aerial tracking in the Gulf of Alaska continued until mid-May. Aerial tion of oil containment and recovery resources to other locations. observations conducted in direct support of booming and skimming operations continued throughout the summer. Tracking instrumentation. Exxon and the USCG used several types Oil containment

of sensor systems to augment visual observations. Both routinely Downloaded from http://meridian.allenpress.com/iosc/article-pdf/1991/1/193/1742936/2169-3358-1991-1-193.pdf by guest on 02 October 2021 employed an ultraviolet/infrared sensor combination for reliable iden- tification of thick oil accumulations during aerial tracking flights. Oil containment booms were crucial in the response to the Exxon The ultraviolet (UV) sensor can detect oil on water because oil has a Valdez oil spill. They served two purposes, first to contain the free oil higher UV reflectivity than water does, so that areas with floating oil for recovery on open water, and second to protect coastal communities appear brighter on the UV image screen than areas without oil. The and sensitive areas such as fish hatcheries and anadromous fish streams sensor is insensitive to oil layer thickness, responding to sheens that from the oil. Figure 2 shows the amount of boom (containment plus may be only a few millionths of an inch thick as well. Because it sorbent) used during the response. At the peak of the containment measures reflected light, the UV sensor must be used during daylight efforts, almost 100 miles of boom were deployed, with another 25 miles hours. held in inventory. The proportion of containment and sorbent booms The infrared (IR) sensor detects differences in sea-surface tempera- was roughly 60 to 40. tures. Differences in heat absorption and radiation, heat conductivity, Containment booms may be divided into six types. Table 1 lists the and volatility cause the temperature of an oil slick and that of the types, makes, and sizes used in the spill response: nearly every type surrounding water to differ. Experimental data show that only oil available in the marketplace is represented.4 Almost all the booms thicker than several thousandths of an inch is capable of sustaining a used in the cleanup are included, but there were a few instances in detectable difference in temperature from that of water. Generally, the which purchasing records did not identify the specific type or size. Also IR sensor is not used by itself, since there are many other possible shown on Table 1 is the amount of boom identified during cleaning as causes for sea-surface temperature variations, such as sunlight and being damaged beyond repair. shadow, winds, currents, organic matter, and melting ice. The UV and Boom deployment. In a spill this size, the use of workers inex- IR sensors used together, however, provide a means of positively perienced in oil spill response methods (local fishermen) to deploy, identifying the larger, thicker portions of an oil slick. anchor, and tend the booms was unavoidable. Technical advisors from Exxon used the UV/IR system developed by Esso Resources Can- spill cleanup service companies and from the boom suppliers provided ada Ltd, Exxon's Canadian affiliate.3 Video images from the instru- training in proper procedures for the different kinds of equipment. ments are fed into a video monitor and recorder. The USCG AirEye Particularly in the initial response, however, variability in the pro- system uses a UV/IR line scanner rather than an imaging system. The cedures led to the booms being handled in ways for which they were not sensors sweep from side to side and depend on the motion of the designed (such as incorrect anchoring, towing, and lifting). Rugged- aircraft for image generation in the second dimension. Output from the ness and durability therefore proved essential for successful boom sensors is shown on a display in the aircraft and is recorded on film. deployment, given the available work force. Side-looking airborne radar (SLAR) is the primary sensor in the Some of the booms were self-inflating; some had to be inflated by AirEye system. The radar waves radiate downward from the aircraft mechanical means (such as generators and air compressors). Self- and can detect an oil slick within a 20- to 40-mile-wide swath. This large inflating booms with valves arranged on the top of the buoyancy swath is the principal advantage of SLAR; with the high cruising speed chambers also presented a special handling problem. If the valves were of the jet aircraft in which it is installed, a large area can be quickly not kept above water during deployment, the buoyancy chambers surveyed. Other advantages are its ability to operate at night and under could, and in some cases did, fill with water, resulting in the loss of the all weather conditions. equipment. The radar image generated by SLAR depends on the roughness of Most containment booms came in 50- to 100-ft sections that must be the sea's surface. Areas with floating oil appear smoother than areas connected one to another. Deployment problems arose from the need without oil, because its presence damps the small, wind-generated to use different kinds of boom in a single operation. Incompatible capillary waves. Consequently, SLAR cannot detect oil on either calm connectors presented the most obvious problem among the various or very rough seas, in which the damping effect of the oil on the surface makes, but ingenuity and baling wire eventually triumphed. roughness becomes inconsequential. SLAR also has difficulty in bays Even booms with "universal" ASTM connectors1 were difficult to and along rugged coasts where geographic features alter the wind's handle and hook up, especially at sea with the boom in tension. The velocity and hence the roughness of the nearby sea. The best results pins required bare-handed operation and were difficult to check for were obtained in the open waters of the Gulf of Alaska. security after installation. When submerged in cold water, the differen- Satellite imagery was tested as a way to track the oil spill. The tial rate of expansion between the aluminum and stainless steel parts of Landsat Thematic Mapper detects oil as a slight difference in the the ball-locked ends often made the connectors difficult to open. reflectivity of the sea surface at near-infrared wavelengths. Image Based on experience during the spill, several design modifications to processing facilities at Exxon Production Research Company were improve boom deployment suggested themselves: used to enhance the image from the satellite. • Booms with shorter flotation chambers are easier to fold, store, Several factors made satellite data not highly useful in oil spill and ship. tracking. The Landsat satellite passed over Prince William Sound only • For anchor points below the waterline, attaching a floating line or once every seven or eight days, and even then the images were some- moving them higher would improve access. times obscured by clouds. Two days were needed to acquire and • A boom 18 inches or larger is awkward to handle in the water. process the data; the results were not timely enough for guiding the Handles on top would be useful. spill response. Consequently, the more readily available aerial recon- • An attachment point is needed for boom lights to warn vessels. naissance information was used for operational support. Containment of free oil on open water. To trap and accumulate free Trajectory forecasting. During the first month after the spill, com- oil floating on the surface of the open water before it reached the puter-based spill motion programs were used to model the spread of shoreline or an environmentally sensitive area, a containment boom the oil and the effects of winds and currents on its movement. A fairly was towed in a U-shaped configuration between two fishing boats. basic spill model was run by Alyeska; it correctly predicted the direc- When the boom was full, the ends were drawn together into a teardrop tion that the spill would take and its shoreline contact with Naked or doughnut shape (Figure 3) to hold the oil until it was recovered by a Island. More sophisticated trajectory forecasting was conducted with skimmer. Towing caused little damage to the booms, but some prob- 196 1991 OIL SPILL CONFERENCE

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Figure 2. Amount of containment plus sorbent boom deployed and in inventory during spill response

lems arose because of improper towing bridles and inexperienced Sawmill Bay during April. As we gained confidence in the ability of the towing crews. outer boom layers to provide sufficient protection, the number of Most booms were recovered in the same way that they were de- layers was reduced. In mid-September the booms were recovered in ployed. However, booms initially deployed from reels were not always good condition from the fish hatcheries, and no oil was ever reported retrieved on reels because the logistics of having the proper reels inside the boomed area. available offshore during recovery. Instead, some booms were re- For most hatcheries, anchoring booms to withstand the environment trieved by cranes pulling on the chain weights or other non-load- was a trial-and-error process. Boom-tending operations such as reset- carrying members. This procedure often damaged the boom fabric or ting anchors, replacing damaged segments, or opening and closing the carabiners attaching the chains to the booms. It was estimated that gates required major expenditures of effort. In the case of Sawmill more than 50 percent of the damage to the larger booms occurred Bay, as many of 15 to 20 boats were used daily for boom-tending and during recovery. for towing sorbent booms to recover sheen. Booms sustained several types of damage during open-water opera- Boom cleaning, maintenance, and disposal. In the first few weeks tions: following the spill, there was neither the need nor the time to clean the • Some sank because of improper deployment, infrequent tending, booms used for recovering free oil on open water. Later, cleaning was leakage in buoyancy compartments, or inadequate redundancy in required, because oily booms tended to leave sheens when being towed the buoyancy system. from one location to another. • Anchorage points or the fabric near anchorage points were torn Initially, all containment booms were cleaned by hand. They were because of loads imposed by waves and current. lifted onto vessels, brushed with a cleaning agent, and wiped down by • Buoyancy compartments or the skirt fabric were punctured by hand with absorbent pads. On a good day, a crew of 6 to 12 workers debris. could clean about 1,000 feet by hand. • Ballast chains along the bottoms of the skirts were ripped off Mechanical boom washing facilities were constructed on a barge during recovery (lifting by the ballast chain). during June, and a second wash barge was added in July. The cleaning • Connectors were damaged by rough handling. equipment consisted of two Expandi washing units and and hand-held Protection of hatcheries and sensitive areas. Containment booms steam washers. Ten persons could clean one to two miles of boom per were used to protect fish hatcheries, streams used by anadromous fish, day with this equipment. and coastal communities threatened by the oil spill. Contractors and Only minor boom repairs were done offshore. A boom requiring local fishermen were assigned the primary responsibility for deploying major overhaul was returned to Valdez, where it was containerized and and maintaining these booms. shipped to Anchorage for repair and winter storage. Booms identified Five key fish hatcheries in Prince William Sound and two hatcheries as being beyond repair were transported to Valdez and processed in the Gulf of Alaska were successfully boomed. The most extensive through the Dayville Road waste-management site. deployment occurred at the hatchery in Sawmill Bay, where on April A total of 140,000 ft (26 miles) of containment boom was judged to 15, 30,500 ft of sorbent boom and 28,600 ft of containment boom were be damaged beyond repair, as shown in the fifth column of Table 1. No deployed in multiple layers. Figure 4 shows a portion of the booms in records are available of the service conditions (number of redeploy- CLEANUP OPERATIONS 197

Table 1. Containment boom used in the cleanup

Amount damaged Amount beyond Percent Size purchased repair beyond Manufacturer Model name or number (inches) (feet) (feet) repair Type A—High-buoyancy internal foam flotation 3M Fire Boom 24 2,500 0 0 ABASCO Beta 1A and IB PVC, Gamma 1A PVC 18,24 23,000 8,580 37 ACME Products O.K. Corral 18,19,20,24,36,40 32,000 7,620 24 American Boom and Barrier Mark I, II, III, IV series 18,19,24,36 32,000 24,450 76 American Marine, Inc. Simplex, Optimax 18,19,24,26,31,36 27,600 20,095 73 Downloaded from http://meridian.allenpress.com/iosc/article-pdf/1991/1/193/1742936/2169-3358-1991-1-193.pdf by guest on 02 October 2021 Containment Systems Corp. Fence, Contractor, Compactible, Harbor 18,24,36 50,000 14,597 29 Hurum Marine Flexy 3 20 10,000 6,081 61 JPS/Oiltrol R, T 16,36 300 200 67 Jet Line Services Spilldam Model 180, 240, 360 18,24,36 23,000 900 4 Kepner Plastics Fabricators Sea Curtain 18,20,30,36 62,500 17,775 28 Navenco Log Boom 20 5,000 0 0 NOFI 24 18,650 0 0 Norpol Marine NOFIXF11, KL80 79,59 1,500 0 0 Numor International M25, M50 12,24 23,000 0 0 Parker Systems MK II Model O-RD 18 5,000 4,590 92 Peratrovich, Nottingham, and Gunderboom 72 55,000 1,150 2 Drage Skimmex Disposable, Standard 12,36 800 40 5 Texas Boom Co. Shorebarrier 20 1,700 740 44 Uniroyal Sealdboom 18,24,36 3,700 2,415 J)5 Subtotal (Type A) 377,250 109,233 29 Type B- Medium-buoyancy, externally attached flotation Slickbar MK Series 10 300 Subtotal (Type B) 300 Type C—External tension member Jackson Trawls Ltd Jackson Trawlnet, 2 Meter Boom 40,78 300 200 67 Trelleborg AB Troilboom Model 750, 1100, 1500 30,43,60 27,210 0 0 Subtotal (Type C) 27,510 200 1 Type D—Self-inflatable Enviro-Pro Ocean Dike, River Dike 18,26 5,400 100 2 Expandi Systems AB Models 3000, 4300, 7000 30,43,70 47,000 d5,281 11 Versatech Products, Ine Zoom Boom 24 5,000 3,265 65 Subtotal (Type D) 57,400 8,646 15 Type E—Pressure-inflatable A/S Roulunds Fabriker Ro Boom 67 20,000 0 0 Goodyear Sea Sentry 38 26,000 60 0 Hoyle Shore Guardian 21 1,800 0 0 Vikoma International Ltd Sectional 750, 950, 1500 Seapack 24,36,60 4,200 0 0 Subtotal (Type E) 52,000 60 0 Type F—Semipermanent installation Aqua-Guard Liteflex, Harborflex 20,30,36,40 3,200 0 0 Chempro Environmental Services Petro Barrier 18,24,36 1,000 1,000 100 Subtotal (Type F) 4,200 1,000 24 Unidentified during cleaning/inspection 23,160 Total 518,660 139,884 27 NOTES: Majority of boom purchased is listed, but table is not comprehensive. No records of service conditions are available; boom damage cannot be attributed to boom design or manufacturing defects. Some boom was lost (sank) or otherwise disposed of and is not listed on this table. There was a large amount of boom damaged, but repairable.

ments, experience level of operating personnel, and environmental Skimmers were the primary oil-recovery device used in the spill conditions) to which these booms were subjected. Thus, in some cases response. Figure 5 shows the number of major units deployed through- the damage columns may not reflect a boom's true ruggedness or out Prince William Sound and the Gulf of Alaska; the smaller ones durability. used intermittently throughout the spill response are not represented on the figure. Most of the oil recovery equipment was deployed in the Sound, since that area was the most heavily affected by the spill. The Gulf of Alaska operations had fewer recovery units, and these tended Oil recovery to be the larger vessels since weather conditions were more severe than in Prince William Sound. Oil recovery operations involved three types of equipment: Specific skimming equipment used in the recovery operation is listed • Skimmers or other devices to recover the product from the water in Table 2 according to skimmer type. Most but not all the skimmers surface were actually put in service. Some were determined to be unsuitable. • Transfer equipment to offload the skimmers Vacuum equipment and positive-displacement pumps were used to • Temporary storage to hold the recovered product until disposal transfer recovered oil, water, and debris from skimmers to temporary 198 1991 OIL SPILL CONFERENCE Downloaded from http://meridian.allenpress.com/iosc/article-pdf/1991/1/193/1742936/2169-3358-1991-1-193.pdf by guest on 02 October 2021

Figure 3. Collected oil held by containment be in a "teardrop" for recovery by a skimmer (photo courtesy of Clean Bay)

storage and then to a vessel for disposal. Table 3 lists the transfer support and towing vessels typically sat so low in the water that it was equipment acquired for use in these cleanup activities. Most of this difficult to detect a slick from them on the water's surface. Although all equipment was leased, and the figures given in the table show the Exxon flights assisted in spotting free oil, many daily flights by fixed- maximum number of units available at any one time. Many vacuum wing aircraft from Valdez and helicopters based on vessels were dedi- systems performed the dual role of transfer equipment and suction cated principally to recovery operations. skimmers. For the purpose of description, vacuum systems are Skimmer offloading. Skimmer offloading was a time-consuming grouped with the transfer devices. step in the free oil recovery process; we therefore attempted to mini- Free oil recovery on open water. Free oil recovery operations were mize skimmer transit time, since this represented downtime. Two or initiated in Prince William Sound on the day of the spill and soon three large barges were used to store recovered oil. Three large landing extended into the Gulf of Alaska; most of these operations were craft and a supply boat with truck-mounted air conveyors also circu- completed by June. The types of skimmers used and where they were lated through the operating area to offload skimmers. In some cases deployed to recover free oil are shown in Table 4, although the mix skimmers traveled to the transfer vessels or storage barges to offload, a changed with time. Only skimmers assigned to vessels are listed; those trip that sometimes took as long as four hours. Other skimmers had to used only intermittently are not included. wait in line to offload, losing additional time. To the extent possible, Large landing craft, 130 to 180 feet in length, were the types used therefore, offloading equipment and storage were kept in the vicinity most frequently for skimmer deployment. In addition to a skimmer, of the high-capacity skimmers. support equipment on the craft included a small crane for skimmer During the early days of free oil recovery, storage capacity was in handling; onboard storage for recovered oil; pumps to transfer recov- short supply, so water was decanted from the skimmers or tanks into a ered oil, water, and debris; and power packs to drive the skimmers and boomed area prior to off-loading. The remaining oil and debris were pumps. very difficult to pump, and off-loading required as long as six or eight Aerial surveillance was needed to track the spread of oil on the water hours. and to direct the deployment of booms and skimmers. The boom Attempts to decant water from the bottom of storage tanks were not always successful, because of alternating layers of oil and water from top to bottom. Large oil/water separators were generally not available, yÈ&É^— but several small, portable separator tanks were obtained from coops. They were deployed on skimmer support vessels and were particularly effective in decanting water into the area ahead of the boom skimmers. The high viscosity and debris content (especially kelp) of the recovered product made offloading difficult, as has been noted. The centrif- ugal pumps on some skimmers were effective only with fresh oil; they were not designed to handle mousse or debris. Progressing cavity pumps performed better, although offloading a skimmer full of weathered oil took many hours. In viscous oil, these pumps tended to evacuate a pocket around the pump inlet, which caused pumping to cease. Rather than shoveling the product into the inlet, off-loading with vacuum equipment proved more efficient. Auger pumps worked well on viscous oil, and those with cutters in their inlets could also handle debris. As a result, many auger pumps were removed from skimmers and lowered into tanks to transfer recovered oil. Augers were not as efficient with light oil, however. Difficulties with standard skimmer offloading pumps led to the extensive use of high-capacity vacuum equipment. An air conveyor Figure 4. Boom in western end of Sawmill Bay, with Armin Koernig could usually off-load a skimmer or tank in less than 30 minutes (Figure Fish Hatchery in the background, April 1989 6). Often the oil was so viscous it could not be pumped out of the CLEANUP OPERATIONS 199

Q GULF OF ALASKA

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MARCH SEPTEMBER

Figure 5. Number of major skimmers deployed during spill response trucks; in such cases, the rear of the air conveyor was opened, and the effective on light oil than on viscous oil or debris. Some of the larger product was dumped into 100-bbl troughs. Grain pumps were partic- units were effective for a much longer time because they had auger ularly effective for offloading operations, typically handling about 200 pumps with cutters to chop up debris. Eventually, however, oil and to 300 bbl per hour of viscous crude and debris. debris would not flow over the weir, and heavy oil also accumulated on Navy Dracone storage bladders were towed behind the Navy Marco the rotors. V skimmers. Three bladders were filled early in the response, but Weir/boom skimmers. A boom skimmer from the U.S. Coast Guard offloading was not completed until June because of difficulties in was put into service six days after the spill occurred, and it worked well handling the viscous crude. The unloading operations were compli- for one week. Thereafter, the oil was too viscous to go through the cated by the presence of gas from decomposed kelp and the crude weirs, and the skimmer was used simply as a towed boom. Other boom itself. Because of its concern over gas buildup, the Coast Guard did not skimmers remained operational for longer periods of time by increas- allow further use of the Dracone bladders. ing their towing speeds to 2 or 3 knots, which forced viscous oil and Skimmer performance in free oil recovery. Skimmer efficiency de- debris into the skimming weirs, thereby assisting the pumps. Fire hoses pends on the type and condition of the oil being recovered. While most were also used on occasion to break up thick blankets of floating oil or skimmers were able to recover oil that was fresh, many lost their mousse before they entered the weir. effectiveness after a few weeks as the oil spread, weathered, emul- Suction skimmers. Barge-mounted vacuum trucks and air conveyers sified, and became mixed with debris. We have summarized below the were used as suction skimmers. Suction heads were used briefly, but experiences reported by personnel with the various types of skimmers their openings were generally too small to handle viscous mousse or used in the recovery efforts. Skimmers with similar principles of opera- debris. Large vacuum units were effective when used with open-ended, tion are grouped together, regardless of manufacturer. six- or eight-inch-diameter suction hose; four-inch hose was too small. Weir skimmers. The simple weir skimmers worked well very early in Paddle belt skimmers. An Egmolap skimmer arrived on April 10 and the spill when the oil was fresh and oil layers were thick. However, was very effective in heavy mousse and debris, recovering as much as swells and choppy conditions generated by multiple wave reflections 18,000 gallons per hour. In light sea conditions with zero swell, almost inside the containment booms resulted in large quantities of water no water was recovered with the oil. In heavier weather, however, the being recovered as well. As the oil became thicker and more debris- blades dipped below the oil/water interface and collected both sub- ridden, the simple weir skimmers were the first to clog and become stances. The paddle belt skimmer from the Canadian Coast Guard was ineffective. easily clogged by viscous oil. Hopper weir skimmers also performed well early in the response, Oleophilic disc skimmers. Large disc skimmers were effective very recovering as much as 5,000 gallons per hour. Although effective early in the spill. Typical recovery rates for the first week of operation longer than other weir skimmers, these skimmers were finally stopped were about 7,000 to 10,000 gallons per hour. However, during cold when very viscous oil mixed with debris would not flow into the early morning or late evening hours, the oil was so viscous that it could hopper. In some cases, the skimmer was kept operational by moving oil not be scraped from the discs. The skimmer's design requires that the manually into the hopper. oil flow between the discs, and the discs had to be rotated very slowly to The weir/vortex skimmers, like other weir skimmers, were more cut through viscous oil. As the oil became emulsified and laden with 200 1991 OIL SPILL CONFERENCE

Table 2. Skimming equipment acquired for use in the cleanup Table 3. Transfer equipment acquired for use in the cleanup

Number Model name or Manufacturer Model name or number acquired Manufacturer number Number acquired Weir skimmers Vacuum trucks Acme Products Tunnel Skimmer 2 Various Vacuum Truck 3 Kepner SeaVac (or Sea Skimmer) 3 Air conveyors Marine Pollution Contr. Buda I and II 2 Keith Hubert (ICI) King Vac 2 Oil Recovery Sweden WP2 1 Super Products Supersucker 6 Parker Systems Oil Hawg 1 Central Engineering Vac-Alls 2 Weir skimmers—hopper Portable vacuum systems A/S De Smithske (Desmi) Destrol 250 12 Pharos Marine GT 185 18 Hyde Products Hyde-Vac, 10-inch 2 Downloaded from http://meridian.allenpress.com/iosc/article-pdf/1991/1/193/1742936/2169-3358-1991-1-193.pdf by guest on 02 October 2021 Pharos Marine GT260 1 Slickbar Trans-Vac 4 Weir skimmers—vortex Vikoma International Powervac 2 Junoverken AB Walosep Wl 2 Auger pumps Junoverken AB Walosep W2 1 A/S De Smithske (Desmi) Destrol DS 150 2 Junoverken AB Walosep W4 2 A/S De Smithske (Desmi) Destrol 250 Pumps removed Weir/boom skimmers from skimmers Offshore Devices Inc. Vessel of Opportunity Skim- 3 Pharos Marine GT 185 Pumps removed mer from skimmers Offshore Devices Inc. High Seas Skimming Barrier 2 Grain pumps Suction skimmers C&R Sales Monster Vac 1 Slickbar Manta Ray 21 C&R Sales Super Vac 4 Paddle belt skimmers Fish pumps Canadian Coast Guard Paddle Wheel 1 Various Fish Transvac 2 S.E.P. Egmo Egmolap II 1 Submersible pumps S.E.P. Egmo Egmopol Barge 10 Marflex Marflex 1 IOleophili c disc skimmers Thune Eureka CCN 153 BP Sunbury Researchi Heavy Oil Skimmer (proto- 3 3 type) TOTAL 34 Frank Mohn A/S (Framo) ACW-400 3 NOTES: Table based on asset accounting records. Most equipment Lockheed Clean Sweep 1 was leased. Quantities are maximum number available at any one Vikoma Komara 12 K Mk D, 12 K 24 time. Not all equipment was used continuously. Mkll Vikoma Seaskimmer 100 1 Vikoma Seaskimmer 50 4 Sorbent belt skimmers Marco Class V 22 some mops was trimmed from nine to six inches, which worked better Marco Class VII 2 for viscous oil. Marco Class XI 2 Dredges. The Valdez spill marked the first time that a hopper dredge Petro Systems Petro Retriever 1 was used for oil recovery in the United States. A hopper dredge is R.B.H. Cybernetics Slicklicker 1 designed to maintain harbors and waterways by removing seabed Rope mop skimmers sediment, which is normally sucked into a draghead, through a drag- ABASCO A14D, A14G 30 arm, and into hopper bins. The dredged material is discharged through Containment Systems 41G 37 doors in the bottom of the hull. Oil Mop, Inc. Mark II-4, Mark II-9, Mark 52 At first, an attempt was made to recover oil from the water's surface 1-4 with the draghead facing down, but without success. However, when TOTAL 266 the draghead was turned upside down, so that the suction head pointed upward (see Figure 7), it operated as a large weir skimmer, recovering NOTES: Quantities are based on asset accounting records. Not all debris and heavily emulsified oil without clogging. As expected, this skimmers were used. method captured a large amount of water with the oil. But because the vessels have a large on-board storage capacity and the ability to decant, the high water volumes presented less of a problem for them than for other skimming systems. debris, the disc skimmers' performance deteriorated, and their use was discontinued. Sorbent belt skimmers. Marco sorbent lifting-belt skimmers supplied Table 4. Skimmers deployed on April 22, 1989 by the Navy were a mainstay in the spill response. In concentrated oil, their recovery rate was 2,400 to 3,600 gallon per hour, which filled their storage capacity in 30 to 45 minutes. Once the spilled oil became Number in Prince Number in Gulf of viscous and emulsified, the sorbent part of the belt was removed and Skimmer type William Sound Alaska Total only the conveyor belt was used to transport the oil up the ramp. The — — — pump aboard the skimmer had difficulty off-loading viscous oil from Weir the sump, so that vacuum equipment was typically used to unload the Weir—hopper 8 8 collected oil. Weir—vortex 1 1 2 Weir/boom 1 1 Rope mops. A few large (nine-inch) rope mop skimmers were used — 7 5 12 to recover free oil. In heavy oil concentrations, it was important to Suction 3 3 minimize the lift required to bring the mop from the water and through Paddle belt — 2 2 the wringer. Keeping the mop horizontal prevented the oil from run- Oleophilic disc 16 7 23 ning down the mop and back into the water. Viscous oil also tended to Sorbent belt 1 gum up the mop and slow down the wringers, so diesel oil was injected Rope mop 1 14 52 into the mop and onto the rollers to cut the viscosity. The diameter of Total 38 CLEANUP OPERATIONS 201

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Figure 6. Supersucker offloading Navy Marco skimmer (photo courtesy of U.S. Navy)

The U.S. Army Corps of engineers provided two dredges for oil south-running currents in the Cook Inlet/Kodiak region. They were recovery in the Gulf of Alaska, the Yaquina and the Essayons. The still present in June, long after the spill had passed through the area. Soviet dredge Vaydaghubsky also operated in the Gulf of Alaska. The By the end of June, there was little free oil in the Gulf of Alaska, and dredges were used primarily in the teardrop mode, that is, by corralling the collection of tarballs and mousse patties became a major activity. the oil in a containment boom and bringing it alongside the dredge. Seiners were used as "mother ships" for skiffs that recovered tarballs The draghead was placed under the boom beneath the oil, and the oil and oily debris with dip nests. The tarballs were near neutral buoyancy was sucked down into the draghead and up to the storage areas on the so it was often necessary to dig among the debris and dip down several ship. Because of their deep draft, the dredges could not work close to feet below the surface to collect the oil. The first "dip net fleet" the shore. operated out of Homer, and at its peak, the Homer fleet consisted of 8 Tarball collection. When sufficiently weathered, oil can form into ships and 30 skiffs. In late July, a similar operation was started out of soft, tan-colored "tarballs". They are typically 1 to 10 inches in diame- Kodiak. About 65 barrels of tarball materials was collected by these ter and have a density approaching that of water. Tarballs, mousse operations. patties, and oily debris accumulated in the rips between the north- and Oil recovery during shoreline treatment operations. As shoreline treatment task forces were deployed, the emphasis of oil recovery operations began to shift from recovering free oil on water to recovering the oil that was freed during shoreline washing operations. Skim- mers played a significant role in this process. Sorbent booms, snare booms, and pom-poms were also widely and effectively used. Skimmers were used to remove oil collected within primary containment booms during shoreline treatment operations. Oil washed from the shoreline was herded toward the skimmers by water sprayed from hoses. Some skimmers with moderate pickup rates, such as disc skimmers or rope mops, ran continuously while oil was being wash from the shoreline. The higher capacity devices operated intermittently. The paddle belt and rope mop skimmers proved to be the mainstays of shoreline oil recovery. Weir skimmers were little used because of their high water cut. Most of the suction devices were used in offloading other skimmers, and many of the sorbent belt skimmers for sheen recovery. Table 5 shows the mix of skimmers deployed on July 20, 1989. The paddle belt skimmers and most rope mop skimmers were deployed on shallow-draft, self-propelled barges that moved from site to site. The paddle belt (Egmopol) barges had built-in storage and offloading capability. The belt assemblies on these skimmers were raised during transit. Upon arriving at the work site, a unit lowered its belt over the primary boom and began skimming (see Figure 8). The vessels used for the rope mops were outfitted with offloading Figure 7. Inverted draghead being lowered from dredge Yaquina pumps and storage containers. The most useful vessels had arms that (photo courtesy of U.S. Army Corps of Engineers) could deploy the mop and pulleys over the primary containment boom 202 1991 OIL SPILL CONFERENCE

Table 5. Skimmers deployed on July 20, 1989 through openings in the barge was continuous, and the 100-bbl storage capacity minimized offloading logistics. Sorbent belt skimmers. The Navy Marco skimmers had a draft of 3 to Number in Prince Number in Gulf of 4 feet, which was too deep to allow operation close to shore and Skimmer type William Sound Alaska Total prevented the vessels' use on all but the most steeply sloping shorelines. They often cruised just offshore to recover oil sheen escaping Weir (all 3 from the shorelines, but even with a sheen belt, recovery of sheen was types) difficult. Suction 7 2 9 Rope mops. Paddle belt 7 7 Rope mop skimmers were used extensively to recover Oleophilic disc 1 1 oil washed from the shoreline. They easily accommodated small quan- Sorbent belt 8 2 10 tities of oil, but proved quite slow for large amounts. Recovery effi- Rope mop 8 8 ciency depended on the ambient temperature; they worked better at Total 34 4 38 temperatures about 60° F. Compared with most other skimmers, rope

mops are more difficult to set up, and they require frequent adjustment Downloaded from http://meridian.allenpress.com/iosc/article-pdf/1991/1/193/1742936/2169-3358-1991-1-193.pdf by guest on 02 October 2021 by the operator to maintain recovery efficiency. Sorbente. Sorbents were widely used to recover small amounts of oil to recover oil (Figure 9). Other rope mops were deployed without and sheen that could not be recovered efficiently by mechanical means. arms; instead, anchors were used to hold the tail pulleys and barge. As The use of sorbents was labor-intensive and generated considerable the tide rose and fell, the anchors were pulled and reset to keep the solid waste, yet sorbents were sometimes more effective than mechani- proper distance from the shoreline and adequate tension in the rope cal recovery. mop. As a result, anchored units were not as easy to operate as other Sorbent booms differ from typical containment booms in that they skimmers. do not have a separate flotation element or skirt. Pom-poms, another Four landing craft carrying truck-mounted air conveyors rotated variety of sorbent, are clusters of oleophilic polypropylene fibers gath- through the task force areas to collect recovered product. Two similar ered together at one end. As the name implies, they look very much vessels were used in the Gulf of Alaska. like the pom-poms used by cheerleaders. A snare boom is made by Skimmer performance in shoreline treatment operations. A large stringing together pom-poms on a rope. cross-section of the personnel involved in the spill response evaluated Pom-poms were extremely effective in picking up small amounts of skimmer performance in shoreline service, as outlined below. weathered oil. Individual pom-poms, snare booms, and sorbent pads Paddle belt skimmers. The most effective skimmer in task force were used extensively to recover oil from inside the primary booms operations was the self-propelled Egmopol barge. Its paddle belt skim- during shoreline cleanup. When fully saturated, pom-poms recovered mer had such a high recovery rate that each unit could circulate among up to 20 times their weight in oil. five to eight work sites. Although the water cut was high, decanting To recover sheen on open water, the sorbent boom was towed behind

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Figure 9. Rope mop skimmer on a Carolina skiff reaching over containment boom to recover oil during shoreline cleanup a fishing boat in a "U," or catenary, formation. The work was time- were not readily available for major repairs; it sometimes took weeks consuming, as it was necessary to pass over the same area several times to receive parts from the lower 48 states or abroad. to absorb the product. Towing in a circular or zigzag fashion was more Recovery equipment on loan from the several oil spill coops and/or successful than towing in a straight line. During extended towing, a government agencies was returned as soon as it was no longer needed sorbent boom absorbed four to eight times its weight in water, which or had been replaced by equipment purchased by Exxon or its contrac- decreased its ability to absorb oil. Sorbent booms made of rolled pads tors. Equipment owned by Exxon was cleaned, then sent to storage were preferred to booms made of loosely packed particles because they facilities in Anchorage as it was demobilized. absorbed less water and were stronger, and if they did break there were not multitudinous small particles to clean up. During shoreline cleanup, sorbent booms were towed by skiffs be- Acknowledgments tween the primary and secondary boom layers to collect sheen. Sor- bent booms and snare booms were deployed along cleaned beaches to protect them from free-floating oil. They also recovered the sheen The work described in this paper was performed by hundreds of released when oil in the sediments was flushed to the surface by tidal dedicated men and women who worked long hours in a difficult environment. More detail on their efforts, and other areas of technology rise and fall. 2 Equipment cleaning, maintenance, repair, and disposition. used in the spill response, is presented elsewhere. The authors would like to thank Exxon Company U.S.A. for permission to publish this Maintenance and repair were critical in keeping oil recovery equip- paper. ment operational. Most of the equipment was purchased new or arrived in good condition. Although mechanical breakdowns did occur, most of the equipment required only normal maintenance or minor repairs. References Recovery equipment became coated with oil and needed periodic cleaning and maintenance before it was redeployed or stored. Smaller 1. American Society for Testing and Materials, 1986. Standard specifi- skimmers and vacuum equipment were often cleaned with high-pres- cation of oil spill response boom connection, D962-86. in 1986 sure sprayers while suspended over waste oil tanks. Larger, self-pro- Annual Book of ASTM Standards, sect. 11, "Water and Environ- pelled skimmers went through the normal boat washing facilities. mental Technology," vol. 11.04. Philadelphia Because of the need for near-constant operation, much of the oil 2. Exxon Production Research Company, 1990. Valdez Oil Spill Tech- recovery equipment was maintained "on-the-fly." In mid-April, the nology—1989 Operations Arctic Tucktu was outfitted to perform preventive maintenance and 3. Goodman, R. H., 1989. Application of the technology in North repairs on skimming equipment. Additional maintenance vessels were America, in The Remote Sensing of Oil Slicks, A. E. Lodge, ed.. equipped when shoreline recovery operations began. These vessels John Wiley, London, pp39-65 shortened the supply lines and provided mechanics with specialized 4. Schultz, Robert, ed., 1987. World Catalog of Oil Spill Response knowledge of oil recovery equipment. For some skimmers, spare parts Products. Port City Press, Baltimore Downloaded from http://meridian.allenpress.com/iosc/article-pdf/1991/1/193/1742936/2169-3358-1991-1-193.pdf by guest on 02 October 2021