Spills of Emulsified Fuels: Risks and Response (2002)

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4 Efficacy of Response: Summary and Evaluation of Available Information In this chapter the available information on response technologies is evalu- ated with respect to the likely efficacy of response in the six settings described in Chapter 2, namely, marine—open water; marine—nearshore; estuarine (brackish water); nontidal river; fresh water—quiescent; and on land near water. Most of the literature on response options for spills of emulsified fuels describes equip- ment and systems that are similar to those traditionally used to respond to spills but modified to have improved effectiveness for spills of emulsified fuels. How- ever, because there have been no significant spills of emulsified fuels, the modi- fied equipment and the strategies for their use have been untested in real cleanup situations. Therefore, no actual spill data for determining actual or measurable effectiveness are available. These response options and their modifications are evaluated to the degree possible in the following sections. It should be noted that the effectiveness of oil response in containment and recovery of spilled oil has been historically low. In the response community, recovery of 20 percent of the spill volume is considered to be a good effort. Where dispersants or in situ burning are used effectively there is little or no additional response or recovery. MARINE OPEN-WATER RESPONSE In recent years, alternative technologies have been accepted as response tools to be considered as part of the oil spill response arsenal in the United States. Alternative response technologies usually include, but are not limited to, the use of dispersants, in situ burning, and bioremediation. Since some emulsified fuels, 66 

EFFICACY OF RESPONSE 67 such as Orimulsion-400, already have a dispersant added in the form of their emulsifying surfactant, at the instance of spillage they disperse into the upper part of the water column. Therefore, the aerial dispersant application operations that are normally considered the first response in many areas of the United States for most spilled oils in the open water, have already taken place with emulsified fuel products. Since 1989, BITOR and its subsidiaries, in conjunction with their primarily utility company clients and U.S. and international government agencies, have studied the response to and possible cleanup techniques for spills of Orimulsion- 100 and Orimulsion-400. These studies provide a large volume of information regarding available cleanup techniques and the individual merits and failures of response for these emulsified fuel products. Table 4.1 summarizes the effective- ness of response options for spills of emulsified fuels in marine open-ocean environments. It is clear that in an open-water marine environment, the preferred response methodology would be to monitor the naturally dispersed bitumen plume using the Surveillance and Monitoring for Alternative Response Technology (SMART) protocols in place for monitoring chemically dispersed spills of other types of oil. This sampling and analysis approach could also be augmented with discrete water column sampling for separate dissolved and dispersed bitumen droplet phases (Payne et al., 1999), to provide calibration for the UV fluorescence approach of the SMART Protocols and validation of computer model predictions of dissolved- and dispersed-bitumen droplet PAH concentrations. The availability of existing sophisticated computer three-dimensional model- ing programs will support and enhance required surveillance operations (French et al., 1997). If any of the spill re-floated and was found, cleanup would be initiated using existing cleanup technology developed and available for Orimulsion, as well as technologies available for other Group V oils that are presently being transported in the United States (National Research Council, 1999). Many of the tests for equipment specifically designed for response to spills of Orimulsion products have been carried out on the open-ocean to determine the ability of responders to recover dispersed bitumen in that environment (Hvidbak and Masciangioli, 2000). As is the case with most open-ocean oil spill response equipment, some equipment developed specifically for response to Orimulsion spills and evaluated during the documented tests, such as the Tar Hawg, the forced adhesion and floatation (FAF) system, the PNP Re-floater, and the deep- skirted containment booms, can reasonably be deployed and perform to some degree of efficiency in calm, open-ocean conditions, especially during an inten- tional spill demonstration scenario (Bitor America Corporation, 1997). For per- sons not familiar with equipment that has been developed specifically for Orimulsion, the Tar Hawg is a belt skimmer that has teeth built into the belt to enhance bitumen adhesion. The FAF and PNP Re-floater systems are two differ- ent methods of pumping both water and Orimulsion from the dispersed plume and forcing air into the pumped material, causing the bitumen to float. As the 

68 SPILLS OF EMULSIFIED FUELS TABLE 4.1 Effectiveness of Response Techniques for Spills of Emulsified Fuels in Marine Open-Water Environments Response Technique Effectiveness for Emulsified Fuels Special Issues Monitoring and Similar to success of tracking SMART protocols should be used tracking intentionally dispersed oils and augmented with large-volume water sampling systems to analyze dissolved and dispersed bitumen PAH concentrations Mechanical re- Even under optimum conditions, Very specialized equipment; not floating and amount of oil that could be found, proven under spill conditions; forced adhesion contained, and re-floated would be little hands-on experience by and flotation of minimal responders. Logistics may be dispersed overwhelming to deploy emulsified oil Long-skirted Limited to upper 3 m of water To be effective, must be deployed containment column, difficult to be towed by before the dispersed plume spreads boom boats, must be allowed to drift with in the water column current Skimming Low overall because of limited Floating bitumen “clumps” are amount of bitumen that will re-float very sticky and viscous, requiring in this environment specialized skimmers and pumping systems Trawl nets Effective for containing and Smaller mesh nets may be more recovering weathered bitumen in effective but will increase drag for tests. Offloading in significant towing vessels. More testing incidents may be an issue for this required recovery technique Pumping Moving recovered bitumen from Successful tests have been skimmers to storage and offloading conducted on small amounts of storage devices will require heavy spilled Orimulsion. However, the oil pumping systems and perhaps effectiveness and efficiency of heating systems tested devices may differ greatly for large uncontained spills On-water Disposable bladders or bags and Tank barges and tanks on storage tanks barges may be used skimming vessels, should have heating coils installed to facilitate offloading Disposal of Same as for other crude oil and oil Shoreside recycling and recovered products incineration are probably best weathered options available bitumen xx 

EFFICACY OF RESPONSE 69 name suggests, the deep-skirted containment boom is a normal offshore-type oil spill containment boom with a 9- to 12-foot skirt. However, although responding to locate and recover any floating weathered bitumen is practical and reasonable, the notion that requiring an operation to be mounted with the goal of tracking, re- floating, and then recovering a dispersed oil of any type in the open ocean would be unrealistic and unreasonable. The disposal of recovered weathered bitumen poses the same problems as the disposal of other recovered crude oil and oil products that are spilled (Bitor America Corporation, 1999). MARINE NEARSHORE RESPONSE In the nearshore marine environment, the surveillance and monitoring re- sponse action (Table 4.2) suggested for the open ocean will be more important because of the increased potential for the bitumen to re-float in sticky clumps. Any re-floated bitumen will provide a threat to wildlife due to the greater number of birds and marine mammals present in the nearshore environment. Furthermore, the potential for re-floated bitumen to come ashore as an oil slick or in the form of sticky tar patties and tar mats is much greater. Because shoreline cleanup is more costly and shoreline impacts increase the potential for natural resource and third-party damages, there should be an increased effort to respond to recover re-floated bitumen as quickly as possible. The containment and recovery of re-floated “clumps” will follow the same strategy and, to a large degree, will use the same equipment available in the open- water marine environment. Response times should be faster for spills in nearshore waters, potentially increasing the effectiveness of on-water containment and re- covery operations. If available, the viscous oil recovery equipment developed for Orimulsion may enhance the recovery rate for resurfaced Group V oil (Garcia Tavel et al., 1997). However, in order to make a difference, equipment such as the Tar Hawg, Oriboom, and other devices must be stockpiled in sufficient quan- tity at locations where the greatest potential for emulsified fuel spills exists (Middleton et al., 1995). Furthermore, local responders need to become familiar with the effective operation of this equipment. While existing equipment re- sources serving other oil transporters and storage facilities will satisfy the con- tainment and recovery of resurfaced Group V oil requirements under the Oil Pollution Act of 1990 (OPA-90), especially if enhanced with the specially de- signed equipment for Orimulsion, the concern will be for the special on-water storage requirements necessary for these types of oils. It would seem that the viscosity of this product will mandate that all tank barges and tanks on skimming vessels be heated if off-loading of filled tanks is considered during a continuing on-water response operation. Since there is greater potential for dispersed bitumen to re-float in the coastal zone, dispersants must be considered for this environmental scenario. Limited 

70 SPILLS OF EMULSIFIED FUELS TABLE 4.2 Effectiveness of Response Techniques for Spills of Emulsified Fuels in Marine Nearshore Environments Response Technique Effectiveness for Emulsified Fuels Special Issues Monitoring and Same as for open-water marine SMART protocols should be used tracking and augmented with large-volume water sampling systems to analyze dissolved and dispersed bitumen PAH concentrations Dispersant Product disperses when spilled; Application of dispersant in an application dispersant effectiveness on re- attempt to redisperse re-floated floated bitumen will be very low bitumen may be ineffective. More study and field testing are required Mechanical re- Because of faster response time for Increased tidal currents and wave floating of deployment of deep-skirted boom, energy in nearshore areas may dispersed this option may be more feasible reduce effectiveness emulsified oil than in open-ocean. However, low effectiveness levels would be expected Long-skirted Because of faster response time, Recommended booming strategy containment this may be more effective in for containing dispersed bitumen boom containing bitumen prior to is a free-floating O-type extensive lateral dispersion configuration Skimming Faster response time for deep-skirted Same as for open-water marine boom and skimmer deployment, increased potential for natural re- floating, increased on-station time for spotter aircraft On-water Same as for open-water marine storage Shoreline Same basic strategy as for heavy Ability to carry out exclusion, protection oils. Expanded use of geotech deflection, and diversion of materials, deep-skirted boom, and dispersed bitumen may require other products such as visqueen to further study cover shorelines prior to impact Shoreline Same basic strategy as for other Preferred use of salt water in cleanup heavy oils. Solvents or chemicals pressure washing to remove may enhance cleanup of some bitumen from substrates will shoreline types increase wear and tear on equipment 

EFFICACY OF RESPONSE 71 TABLE 4.2 Continued Response Technique Effectiveness for Emulsified Fuels Special Issues Wildlife Same strategy as for other oils Studies required to determine the efficiency and toxicity of preferred cleaning agent Dredging Limited to submerged areas where Many operational issues in regard sunken oil would accumulate to water depth, storage, disposal of recovered oily water and sediments, sea conditions, and currents Diver-directed Limited to submerged areas where Visibility, water depth, storage and pumping and sunken oil would accumulate disposal of recovered oily water vacuum systems and sediments, sea conditions, and currents Disposal Same as for open-ocean xx studies have indicated that applying dispersant to re-floated bitumen will cause some redispersal (Oil Spill Response Limited, 1989). However, more work would have to be completed to determine if the dispersant application would be efficient and effective. Shoreline protection and cleanup must also be considered in the coastal environment. For the most part, shoreline protection and cleanup of emulsified fuels will be conducted in the same manner as for other oil products (Owens and Sergy, 1999). There may also be a need to protect sensitive areas from shoreline impact if possible. Presumably this can be achieved by using long-skirted booms to exclude the oil from the zone to be protected, diverting it to a less sensitive shoreline for recovery or deflecting it back to open water (Morgan and Fernie, 1995; Owens and Sergy, 1999). Once weathered bitumen is stranded on the shoreline, chemical agents en- hance its removal (Guénette et al., 1998). However, further testing, particularly with agents accepted by the U.S. EPA for use in the United States, should be conducted to determine their efficiency in removing stranded bitumen coatings from various shoreline types and to study the fate and effects of the released bitumen. As with other types of heavy oil, mechanized beach cleaners and other types of mechanical or manual recovery equipment are efficient in cleaning up stranded weathered bitumen from certain shorelines (Clement et al., 1997). Dredging or other types of underwater recovery must also be considered as a response option, 

72 SPILLS OF EMULSIFIED FUELS because oil-sediment tar mats may be deposited in offshore depressions. Again, these operations will be similar to those used for spills of other types of heavy oil (National Research Council, 1999). Because of the increased potential for contact with wildlife cleaning, of seabirds particularly, will become an issue. Even though a suitable agent has been proposed for cleaning wildlife (Gauvry and Miller, 1995), the effect of weathered Orimulsion on wildlife and the ability to clean contaminated wildlife for return to their habitat remain to be seen. The report by Gauvry and Miller (1995) called for more study to determine the ability of the preferred cleaning agent to remove Orimulsion from birds and other species and to determine the toxicity of the cleaning agent itself to various types of wildlife. ESTUARINE (BRACKISH WATER) RESPONSE Only a small fraction of the spilled emulsified fuel is expected to re-float in an estuarine environment. The response strategies for estuaries will follow very closely those strategies discussed for the open-ocean, because the majority of the bitumen droplets will remain in suspension or sink (Table 4.3). However, because many estuaries in the United States are also major port areas, the response time to spills should be much faster than for spills in the open- ocean or in coastal zones. Therefore, some of the response techniques discussed for the open-ocean and nearshore environments are appropriate for estuaries as well, and they may be more efficient because of the increased speed of response and access to shoreside support resources. Estuaries do have zones of low flow where suspended particles may settle out, increasing the potential need for dredging or underwater vacuum recovery opera- tions. However, the issue would be whether there is enough accumulation of “oil” to warrant bulk oil removal. Dredging and diver-assisted pumping or other types of underwater recovery operations can be very effective; however, they are also very expensive and require handling of large volumes of potentially contaminated water and sediment. Furthermore, dredging is not a commonly used spill response tech- nique, and the required equipment may not be readily available. NONTIDAL RIVER RESPONSE Because of the fresh water and current conditions in a river, an emulsified fuel spill is expected to remain in suspension and to become more dispersed as it spreads further downstream. Therefore, tracking of the plume will require water column monitoring, either with grab water samples (limited spatial coverage, very slow) or field detectors such as fluorometers. Even where trajectory models are available, they must be validated with field data on the location of the main body of the plume. Without preplanning that 

EFFICACY OF RESPONSE 73 TABLE 4.3 Effectiveness of Response Techniques for Spills of Emulsified Fuels in Estuaries (Brackish Water) Response Technique Effectiveness for Emulsified Fuels Special Issues Monitoring and With so little surface oil, it will be Gradients in water salinity over tracking difficult to track the dispersed oil space and time, will have plume using overflights. Water significant influence on ability to sampling or remote sensing methods model the dispersed oil plume will be required, which have significant limitations Dispersant Not applicable because so little application bitumen is expected to float or re- float Mechanical Even though response times should If suspended plume can be refloating and improve, containing dispersed diverted to a quiet backwater, this FAF of bitumen in tidal currents while may be an option dispersed attempting to re-float it will be emulsified oil difficult Long-skirted Because of tidal currents, even Set and drift of vessels supporting containment tear-dropped boom drifting with the re-floating and skimming boom current may not be able to contain operations will cause increased dispersed droplets for recovery. entrainment of bitumen from May consider diverting dispersed containment boom bitumen plume to quiet water for settling-dredging or re-floating operations Skimming Because of improved response times and less area, skimming operations should be as effective for floating emulsified fuels as would be expected for other oils On-water storage Same as open-ocean or nearshore Shoreline Due to freshwater influence and less protection potential for “clumping” there may be less shoreline impact Shoreline Due to freshwater influence and less cleanup potential for “clumping” there may be less shoreline impact Dredging Same as nearshore Diver-directed Same as nearshore pumping and vacuum systems Disposal Same as open-ocean xx 

74 SPILLS OF EMULSIFIED FUELS includes purchase, training, and maintenance of the necessary equipment, the monitoring of emulsified oil in rivers will be very difficult. There are at least 75 hazardous substances currently being transported in bulk on tankers and tank barges throughout the United States that present these same problems when spilled (U.S. Code of Federal Regulations). As discovered during a 1996 survey of resources available for response to releases of bulk hazardous substances trans- ported by water, there may be a shortage of readily available equipment and personnel trained to monitor and sample products that either disperse, dissolve, or sink (Chemical Transportation Advisory Committee, 1996-1997). However, if and when the OPA-90 regulations for hazardous substances are finalized, they may include provisions that require transporters to have the ability to readily provide monitoring and sampling resources and expertise, and this situation will improve. There will be very little opportunity for suspended droplets to re-float in this environment; therefore, there will be little or no opportunity to recover bitumen from the water surface using skimmers (see Table 4.4). The droplets will remain in suspension until the surfactant degrades, so they will be widely distributed before they attach to other suspended matter and sink. Therefore, it is doubtful that there will be sufficient accumulations in depression and behind natural and man-made structures to substantiate a dredging or diver-directed pumping or vacuum system recovery. The most feasible response in this environment will be to deploy exclusion or deflection long-skirted booms or silt fences at water in- takes and other sensitive sites downstream. Alternatively, downstream locations where the bitumen droplets might settle out (e.g. low-flow areas, backwater sloughs) and dredging-pumping-vacuum operations might be effective could be identified. If sufficient quantities of dispersed bitumen can be diverted to these quiet areas, then the PNP Re-floater or FAF principle could be considered as a response option. Based on limited experi- ments, the PNP Re-floater device is about 30 to 60 percent effective in re-floating dispersed bitumen in freshwater environments (Hvidbak and Masciangioli, 2000). Although recovery is lower than for salt water, laboratory testing indicates a good recovery of dispersed re-floated bitumen in fresh water. However, aeration is essential since recovery only occurs at the surface. If the sorbent or polymer material is delivered as part of the aeration process, efficiency may be increased even further (M3 Inc., 1996). FRESHWATER QUIESCENT RESPONSE A discharge of emulsified fuel in a freshwater, quiescent setting, such as a port facility, will offer the best opportunity for containing and recovering the spilled bitumen or oil. A facility that receives routine cargo of emulsified fuel can plan for spill events and provide the necessary equipment needed for contain- ing and recovering it. 

EFFICACY OF RESPONSE 75 TABLE 4.4 Effectiveness of Response Techniques for Spills of Emulsified Fuels in Nontidal Rivers Response Technique Effectiveness for Emulsified Fuels Special Issues Monitoring and Visual techniques will not be Real-time river flow data are tracking effective in most rivers. Most available to predict spread of the effective would be fluorometers dispersed plume. Would require deployed on boats or at one location preplanning for use of water (e.g., water intake) column monitors. May be shortage of readily available sampling equipment and qualified technicians Dispersant Since emulsified fuels will remain None application in suspension in fresh water, dispersant will not be considered Mechanical re- In most cases, not a viable or Effectiveness of PNP Re-floater floating of efficient option. However, if and FAF has to be validated for dispersed dispersed bitumen can be diverted fresh water emulsified oil to a quiet water area, it may be tried Long-skirted May consider diversion or exclusion Specially designed booms with booming booming to protect water intakes or semi-permeable skirts might be sensitive areas. Can probably be more effective than regular booms effective only in slow-current environments Skimming Use only in conjunction with PNP None and FAF operations Sorbents and May be effective, if used with Containment will be an issue using polymers aeration these techniques On-water storage Required for skimming conducted None in conjunction with PNP and FAF operations Shoreline Not applicable because no shoreline None protection stranding should occur Shoreline Not applicable because no shoreline None cleanup stranding should occur Dredging Low effectiveness because of low River currents should keep potential for accumulation of particles in suspension and recoverable amounts of bottom oil enhance spreading Diver-directed Low effectiveness because of low Low visibility in rivers may pumping and potential for accumulation of make diver operations less vacuum systems recoverable amounts of bottom oil effective Disposal Same as open ocean None xx 

76 SPILLS OF EMULSIFIED FUELS Furthermore, although the equipment designed for Group IV and V oils may not be as efficient as specially designed equipment, it will be more available and perhaps more rapidly deployed in this environment. Because many transfer facilities are situated in at least semi-protected areas, it is likely that the berth will be pre-boomed (or can immediately be boomed) with a deep-skirted boom or silt curtain following a spill. In this case, the majority of the bitumen droplets will remain in suspension until they sink to the bottom of the berth or are re-floated. Although the PNP Re-Floater may achieve only 30 percent success in fresh water, a fully contained spill would provide more time to work the dispersed bitumen, and a greater percentage may be obtained (see Table 4.5). A fully contained spill at a shoreside facility would also allow greater oppor- tunity for the use of FAF system technology. It would allow the dispersed plume to be pumped to shoreside tanks where FAF would allow separation, floatation, and recovery. This scenario also provides the best opportunity for carrying out dredging or diver-assisted pumping operations to recover the bitumen droplets that settle on the bottom. Once on the bottom the bitumen will likely remain until recovery can take place. The shallow water depths in a port area will also be conducive to dredging operations. ON LAND NEAR WATER RESPONSE When spilled on land, fresh Orimulsion will behave like a viscous liquid, with the potential for penetration into porous substrates. Response and cleanup methods would be similar to those for conventional heavy oils. As it weathers and becomes sticky, the degree of penetration will decrease, and cleanup will likely involve complete removal of the surface oil and oiled sediments. Even though the risk of groundwater contamination is low, groundwater cleanup methods would be needed for the water-soluble fraction contained in the water component. In this type of spill, the emulsified fuel will remain in suspension when in water. Containment booming using regular containment boom and filter-fence- type material should be possible (see Table 4.6), because of the reduced current and very shallow-water conditions expected in a wetland habitat. Dikes and berms could also be constructed to isolate the spill area from other waterways and reduce migration. Depending on the amount of product spilled, the size of the area impacted, and the sensitivity of the wetland, the area could be isolated and pumped dry for manual or heavy equipment recovery of oil or bitumen from the substrate. The spill site could then be treated by burning or land farming. To ensure that only clean water was discharged downstream the effluent from any pumping operation to a dry out area could be routed through a filter box arrange- ment, or FAF or a PNP Refloater pumping system could be used to pump out the marsh water. In areas where the land is alternately wet and dry, emulsified fuels, 

EFFICACY OF RESPONSE 77 TABLE 4.5 Effectiveness of Response Techniques for Spills of Emulsified Fuels in Freshwater Quiescent Environments Response Technique Effectiveness for Emulsified Fuels Special Issues Monitoring and Can be relatively effective because None tracking the point of exit can be the focus of water column monitoring Dispersant Not applicable because none of the None application oil will float Mechanical re- Tests indicate that only 30 percent None floating of effectiveness can be achieved in dispersed fresh water. However, logistics emulsified oil available in this scenario may make it a viable option FAF system Shoreside facilities and ability to Oil water treatment facility and/or contain dispersed bitumen plume decanting authority would be make this a viable option for this necessary scenario Long-skirted Predeployed deep-skirted boom Facility response planning allows containment should be considered for transfer for advanced containment strategy boom facilities. For emulsified fuel that and equipment staging escapes the encapsulated area, river environment techniques would apply Sorbents and Same as rivers Containment should be improved polymers in this environment Storage Should not be limiting because of Facility response planning allows many shoreside options for advanced containment strategy and equipment staging Shoreline Limited to areas where re-floating None protection operations take place Shoreline Limited to areas where re-floating None cleanup operations take place Dredging Oil or bitumen that sinks should be None contained in the immediate vicinity of berth and readily recovered Diver-directed Oil or bitumen that sinks should be Bottom topography can be highly pumping and contained in the immediate vicinity variable, so divers may have to vacuum systems of berth and readily recovered direct recovery to zones of higher accumulation xx 

78 SPILLS OF EMULSIFIED FUELS TABLE 4.6 Effectiveness of Response Techniques for Spills of Emulsified Fuels on Land Near Water Response Technique Effectiveness for Emulsified Fuels Special Issues Monitoring and Can be highly effective since plume None tracking is highly visible Dispersant Not applicable because none of the None application oil will float Mechanical Dependent on water depth. May be None refloating of considered part of any pumping dispersed operation intended to increase flow emulsified oil from marsh or to dry area for recovery of product that sinks Containment Regular boom, filter fence, and Access will be an important boom deep-skirted boom should be consideration considered depending on water depths Berms or dikes Install berm or dike to contain spill Environmental concern regarding within marsh area already impacted impact of stopping flow of water through marsh Skimming Not effective because none of the None bitumen is expected to float Sorbents and Could be moderately effective None polymers where plume can be concentrated to flow through a restricted area Storage May be difficult in areas of limited None access Shoreline Minimal shoreline protection None protection strategy required Excavation or Method dependent on water depth Disposal of large volumes of dredging and soil conditions. Removal of material contaminated sediments using heavy equipment or manual labor Shoreline Shoreline cleanup will be required Access will define type of cleanup cleanup on any surface where the product technique to large extent flowed across soil or vegetation and dried. Normal oil shoreline cleanup techniques will apply 

EFFICACY OF RESPONSE 79 TABLE 4.6 Continued Response Technique Effectiveness for Emulsified Fuels Special Issues Dredging Same as for estuarine environment. Access will be critical for defining Amount spilled, area impacted, type of dredging equipment that type of marsh environment, and may be used water depth will be critical Diver-directed Same as dredging above None pumping and vacuum system Excavation Pump impacted marsh or wetland Environmental effect of pumping area dry, and excavate oil or bitumen marsh dry that has sunk and accumulated In situ burning Pump impacted marsh or wetland Burning agent will have to be used area dry, and burn oil or bitumen to support in situ burn of bitumen. that has sunk and accumulated Environmental effect of pumping marsh dry Land farming Pump impacted marsh or wetland Environmental effect of pumping or area dry, and land-farm or fertilize marsh dry bioremediation to enhance biodegradation xx and bitumen in particular, are less likely to leach into the substrate than other heavy oils (Wood, 1996). SUMMARY Because emulsified fuels are essentially predispersed, the most likely re- sponse actions will be monitoring of the dispersed plume and recovery of any re- floated bitumen. Recovery efforts are likely to be even lower than for traditional spills because so little of the oil is expected to re-float. Therefore, as for all types of spills, the most effective strategy, is prevention. Many of the proposed strategies for responding to spills of emulsified fuels are likely to have low initial effectiveness for the following reasons: • They have not been tested under realistic conditions. • The equipment may not be readily available at all necessary locations. • Responders are not familiar with the equipment and strategies available for emulsified fuel spills 

80 SPILLS OF EMULSIFIED FUELS • There have not been spills where the proposed strategies could be tested and made more effective under field conditions. • For example, mechanical re-floating of dispersed bitumen has been dem- onstrated in small intentional spill scenarios and is suggested as a practical re- sponse to a spill of emulsified fuel. However, only actual experience will determine if it is practical to re-float any type of dispersed oil and, if required, to determine whether the methodologies being suggested are logistical and practical for likely spill scenarios. Another proposed strategy is diversion or deflection of a dispersed plume using deep- skirted booms; field tests should be conducted to validate this strategy and deter- mine the physical and environmental limitations. Tests with trawl-type nets for containing and recovering floating weathered bitumen indicate that smaller-mesh nets might make the systems more effective. Further tests are needed to deter- mine if towing smaller-mesh nets is practical. Realistic field tests1 and refine- ment of the more innovative methods for containment and recovery of emul- sified fuels are required before these methods can be part of realistic response plans. 1Environmental restrictions on the release of possibly toxic substances may contstrain certain types of field tests.