Prediction of the Dispersal of Oil Transport in the Caspian Sea Resulting from a Continuous Release

A 3-D hybrid flow/transport model has been developed to predict the dispersal of oil pollution in coastal waters. The transport module of the model takes predetermined current and turbulent diffusivities and uses Lagrangian tracking to predict the motion of individual particles (droplets), the sum of which constitute a hypothetical oil spill. Currents and turbulent diffusivities used in the model have been generated by a numerical ocean circulation model (Princeton ocean model) implemented for the Caspian Sea. The basic processes affecting the fate of the oil spill are taken into account and parameterized in the transport model.The hybrid model is implemented for a simulated continuous release in the coastal waters of the Caspian Sea. The potential of the model for the prediction of the advective and turbulent transport and dispersal of oil spills is demonstrated.     

South Arne Field Development: An Environmental Impact Assessment of Oil Spills

The South Arne field being developed by Amerada Hess A/S is located in 60 m water depth approximately 200 km from the Danish mainland, in block 5604/29 of the Danish sector of the North Sea.As part of the development of the field, a comprehensive environmental impact assessment has been carried out, including the assessment of the impact from oil spills. The Danish authorities required that a ‘worst case’ oil spill be chosen as the basis for the assessment on birds and aquatic organisms including plankton, fish eggs and larvae and benthos.A well blow-out at the surface was chosen as the worst case for the impact on birds, and a seabed blow-out for aquatic organisms.The oil spill modelling was carried out with the DEEPBLOW, SLIKMAP and OSCAR models from SINTEF. The modelling identified environmentally sensitive areas which could potentially be influenced by an oil spill. These included the Dogger Bank, western Skagerrak, south-western Norwegian Trench, the eastern German Bight and the Wadden Sea.Historical meteorological and hydrodynamic scenarios were chosen from a long period of records to ensure that the plume passed through the environmentally sensitive resource areas.For birds, a scan of the literature and available databases was made to determine the numbers and species of birds in the areas swept by the surface slick, the number of fatalities was estimated and finally the recovery time for each species population was estimated.The impact on aquatic organisms was estimated using the predicted environmental concentration/predicted no effect concentration (PEC/PNEC) method of the CHARM model. This method is normally applied to continuous discharges, but here has been used to estimate the impact of a transient pollution cloud resulting from an oil spill.     

Australia's National Plan to Combat Pollution of the Sea by Oil and Other Noxious and Hazardous Substances – Overview and Current Issues

Australia's National Plan to Combat Pollution of the Sea by Oil and Other Noxious and Hazardous Substances (the National Plan) has operated since 1973. The objectives of the National Plan are based on Australia's obligations as a signatory to the International Convention on Oil Pollution Preparedness, Response and Co-operation 1990 and a responsibility to protect natural and artificial (man made) environments from the adverse effects of oil pollution and minimise those effects where protection is not possible.The Australian Maritime Safety Authority (AMSA) is the managing agency of the National Plan, working together with the States and Northern Territory governments, other Commonwealth agencies, ports, and the shipping, oil and exploration industries, to maximise Australia's marine pollution response capability.The 1990s have been a period of significant change for oil spill response arrangements in Australia. The National Plan was extended in 1998 to cover chemical spills and is currently in the process of implementing the oil spill response incident control system (OSRICS). A fixed wing aerial dispersant spraying capability was implemented in 1996 and a research and development program has been put in place. The development of a computer-based National Oil Spill Response Atlas was a major project completed during 1999.     

Overview of the Compensation and Liability Regimes Under the International Oil Pollution Compensation Fund (IOPC)

This paper focuses on the cost recovery issues arising through the operation of the International Oil Pollution Compensation Fund (IOPC) and administrative matters which arose following the Braer and Sea Empress oil tanker pollution incidents in the UK. Each of these oil spills brought very different problems.Any major oil spill will have prolonged economic and social consequences for the communities affected. Membership of the International Oil Pollution Compensation Fund (IOPC Fund) will do much to soften the impact as regards economic damage. However, the operation of the Fund brings difficulties which may not have been considered by the administration prior to the spill. Some of the difficulties are foreseeable.It covers details of the international compensation and liability regimes, it considers a number of administrative consequences and highlights seven lessons that have been learned in the UK in the light of recent experience. These lessons are:

• •Claims may not be paid quickly or in full.
• •Claimants will need advice and government involvement.
• •Action by the government may be needed to complement the IOPC Fund.
• •Governments have to balance their obligations as a member state with the needs of claimants.
• •It is better for claimants to keep matters out of court for as long as possible.
• •Administrative consequences will continue for a long time after the oil has been cleared from the shoreline.
• •Each major oil spill brings different cost recovery problems and will also bring demands ‘to learn the lessons’.

In much the same way as contingency plans are regularly tested, each state party to the regime would be wise, from time to time, to think through the likely scenarios so as to better prepare themselves in the light of experiences elsewhere. The United Kingdom has had rather more experience in recent years than it would have wished!     

Real time oil spill forecasting during an experimental oil spill in the arctic ice

The oil spill trajectory and weathering model OILMAP was used to forecast spill trajectories for an experimental oil spill in the Barents Sea marginal ice zone. The model includes capabilities to enter graphically and display environmental data governing oil behavior: ice fields, tidal and background current fields, and wind time series, as well as geographical map information. Forecasts can also be updated from observations such as airplane overflights. The model performed well when wind was ‘off-ice’ and speeds were relatively low (3–7 m s⁻¹), with ice cover between 60 and 90%. Errors in forecasting the trajectory could be directly attributed to errors in the wind forecasts. Appropriate drift parameters for oil and ice were about 25% of the wind speed, with an Ekman veering angle of 35° to the right. Ice sheets were typically 1 m thick. When the wind became ‘on-ice’, wind speeds increased to about 10 m s⁻¹ and trajectory simulations began to diverge from the observations, with observed drift parameters being 1.5% of the wind speed, with a 60° veering angle. Although simple assumptions for the large scale movement of oil in dense ice fields appear appropriate, the importance of good wind forecasts as a basis for reliable trajectory prognoses cannot be overstated.     

Computer Modeling of Oil Spill Trajectories With a High Accuracy Method

This paper proposes a high accuracy numerical method to model oil spill trajectories using a particle-tracking algorithm. The Euler method, used to calculate oil trajectories, can give adequate solutions in most open ocean applications. However, this method may not predict accurate particle trajectories in certain highly non-uniform velocity fields near coastal zones or in river problems. Simple numerical experiments show that the Euler method may also introduce artificial numerical dispersion that could lead to overestimation of spill areas. This article proposes a fourth-order Runge–Kutta method with fourth-order velocity interpolation to calculate oil trajectories that minimize these problems. The algorithm is implemented in the OilTrack model to predict oil trajectories following the “Nissos Amorgos” oil spill accident that occurred in the Gulf of Venezuela in 1997. Despite lack of adequate field information, model results compare well with observations in the impacted area.     

Introduction/Overview to In Situ Burning of Oil Spills

In situ burning is an oil spill response technique or tool that involves the controlled ignition and burning of the oil at or near the spill site on the surface of the water or in a marsh (see Lindau et al., this volume). Although controversial, burning has been shown on several recent occasions to be an appropriate oil spill countermeasure. When used early in a spill before the oil weathers and releases its volatile components, burning can remove oil from the waters surface very efficiently and at very high rates. Removal efficiencies for thick slicks can easily exceed 95% (Advanced In Situ Burn Course, Spiltec, Woodinville, WA, 1997). In situ burning offers a logistically simple, rapid, inexpensive and if controlled a relatively safe means for reducing the environmental impacts of an oil spill. Because burning rapidly changes large quantities of oil into its primary combustion products (water and carbon dioxide), the need for collection, storage, transport and disposal of recovered material is greatly reduced. The use of towed fire containment boom to capture, thicken and isolate a portion of a spill, followed by ignition, is far less complex than the operations involved in mechanical recovery, transfer, storage, treatment and disposal (The Science, Technology, and Effects of Controlled Burning of Oil Spills at Sea, Marine Spill Response Corporation, Washington, DC, 1994).However, there is a limited window-of-opportunity (or time period of effectiveness) to conduct successful burn operations. The type of oil spilled, prevailing meteorological and oceanographic (environmental) conditions and the time it takes for the oil to emulsify define the window (see Buist, this volume and Nordvik et al., this volume). Once spilled, oil begins to form a stable emulsion: when the water content exceeds 25% most slicks are unignitable. In situ burning is being viewed with renewed interest as a response tool in high latitude waters where other techniques may not be possible or advisable due to the physical environment (extreme low temperatures, ice-infested waters), or the remoteness of the impacted area. Additionally, the magnitude of the spill may quickly overwhelm the deployed equipment necessitating the consideration of other techniques in the overall response strategy (The Science, Technology, and Effects of Controlled Burning of Oil Spills at Sea, Marine Spill Response Corporation, Washington, DC, 1994; Proceedings of the In Situ Burning of Oil Spills Workshop. NIST. SP934. MMS. 1998, p. 31; Basics of Oil Spill Cleanup, Lewis Publishers, Washington, DC, 2001, p. 233). This paper brings together the current knowledge on in situ burning and is an effort to gain regulatory acceptance for this promising oil spill response tool.     

Effectiveness of “Nochar” Solidifier Polymer in Removing Oil from Open Water in Coastal Wetlands

The use of solidifier in oil spill cleanup has been minimal due to lack of practical application method and in situ field testing and evaluation under various coastal and environmental conditions. Solidifiers are dry granular, hydrophobic polymers that react with oil and form a cohesive mass that floats on water. Unlike sorbents, the oil is retained in the solid mass allowing for easy removal. A field test was conducted in coastal Louisiana in which replicated open water enclosures were oiled with South Louisiana Crude. Granular solidifier was spread over oil and the solidified oil was then removed from the plots. Over 70% of the applied oil was recovered. Results demonstrated that solidifier may, under certain conditions, be an option for removing oil from wetlands.     

The Social and Political Meaning of the Exxon Valdez Oil Spill

In this paper we argue that the Exxon Valdez oil spill gained so much attention because of its setting in Alaska. Alaska symbolizes for many Americans the wilderness or frontier that has long been part of American thought. At the same time, American national development has largely depended on the discovery and use of the nation’s abundant natural resources. The setting of the Valdez spill in the seemingly pristine waters of Prince William Sound brought the tension between our national identification with wilderness and our national need for further natural resource exploitation into sharp focus. In the aftermath of the spill, a legislative deadlock was passed and the Oil Pollution Act of 1990 was passed. The Valdez accident had longer-term consequences as well, most prominent of which is related to the ongoing debate over whether to open up the coastal plain in the Arctic National Wildlife Refuge to further development.     

Oil outflow estimates for tankers and barges

Results of an analysis to estimate potential oil outflow from tankers in the event of groundings and collisions is presented. Three baseline tanker types are considered: pre-MARPOL (COW), MARPOL '73 (SBT only), MARPOL '73/'78 (PL/SBT) before and after these tankers have been retrofitted with various combinations of pollution prevention measures. Specifically the analysis examines four tanker sizes, 46 600, 71 000, 152 000 and 268 000 dwt, and various pollution measures — protectively located spaces (PL/spaces) in various ballast arrangements and with clean ballast tanks (CBTs), hydrostatically balanced loading (HBL), probabilistically located HBL, combinations of HBL and PL/spaces, double bottom or double side retrofits, and replacement of the tanker with a double hull vessel. Additionally, oil outflow estimates are presented for a US coastal and an ocean going barge of over 5000 gt with and without PL/spaces, PL/SBT, and HBL. The accidental oil outflow estimates are developed in accordance with probabilistic and deterministic models of IMOs MARPOL Annex I Regulations 13F and 13G. The accidental oil outflow estimates presented in the paper may provide oil spill response and related organizations with information to assist in planning for oil spill response activities.     

The Myth of the “Pristine Environment”: Past Human Impacts in Prince William Sound and the Northern Gulf of Alaska

The coastal region affected by the Exxon Valdez oil spill, although a beautiful and sensitive maritime wilderness with bountiful fish and wildlife, was not a pristine environment in 1989. Prior to the spill, Prince William Sound and the northern Gulf of Alaska region had experienced extensive human impacts from the commercial fur trade, commercial sea-mammal hunting, commercial fishing, logging, mining and introduced exotic species including foxes, Sitka black-tailed deer and hatchery-reared pink salmon. The spill occurred in a scenic area that was (and is) paradoxically both the source of subsistence food for local residents and the scene of extensive natural resource exploitation.Contrary to media sound bites and news headlines, the Exxon Valdez oil spill did not destroy a pristine wilderness. The Russian and American fur traders, commercial whalers and commercial fishermen, miners, loggers, fox farmers and military construction crews had transformed the region long before March 24, 1989. The Exxon Valdez spill was an important chapter in the history of human impacts to the area’s maritime ecosystem, but it was not, as many continue to claim, the mother of all environmental impacts in the region.     

A Numerical Simulation of an Oil Spill in Tokyo Bay

An oil spill accident happened in Tokyo Bay on 2 July 1997. About 1500 m³ of crude oil was released on the sea surface from the Japanese tanker Diamond Grace. An oil spill model is applied to simulate the fate of spilled oil. The Lagrangian discrete-parcel method is used in the model. The model considers current advection, horizontal diffusion, mechanical spreading, evaporation, dissolution and entrainment in simulating the oil slick transformation. It can calculate the time evolution of the partition of spilled oil on the water surface, in the water column and the sedimentation on the bottom. A continuous source at constant rate is set up as a tanker off the coast of Yokohama. The grid size is 1 km in the calculation domain. The residual flow simulated by a 3-D hydraulic model and observed wind data are used for advection. The simulated distribution of oil spreading agrees well with observations from satellite remote-sensing.     

Hindcast of a Japan Sea oil spill

An oil spill model was applied to the Nakhodka tanker spill accident that occurred in the Japan Sea in January 1997. The amount of oil spilled was estimated to be around 5000 kl, released over 1 day. Under a 2-m wave height condition, and a 3.5% of drift factor, the model simulated the oil slick to hit the shoreline after 6 days. This was in good agreement with the observed conditions. After drifting to the shoreline, the oil slick moved northeastward with the current. In the model, the simulation where the shoreline absorbs 100% of stranded oil failed to reproduce the actual oil slick trajectory. The simulation in which oil resuspended after stranding indicated a similar trend to the actual case. Therefore, it is likely that a considerable amount of oil that hit the shoreline may have returned to the sea and moved with the current. The effects of current pattern and wind drift angle on the oil slick trajectory were also examined. It is suggested that the wind parameters were of prime importance in reproducing a realistic distribution.     

An exposure index for oiled shorelines

Wave action is the most effective natural cleaning agent of oiled shorelines. Therefore, the degree of exposure of a shoreline to wave action dictates how quickly that shoreline will be cleaned by natural processes. In the absence of recorded wave data, a simplified exposure index, tested on the shorelines of Prince William Sound, Alaska oiled during the Exxon Valdez oil spill, can be used to predict potential cleansing by wave action. Wind gauge data correlated with three effective fetch distances measured perpendicular to and at 45° to the shoreline are used to calculate the exposure index. In Prince William Sound, both biological and geomorphological criteria for exposure to waves agreed with the readings calculated for the index. Surface oil on the exposed shorelines was removed quickly during the first storm season. Sheltered coasts were cleaned more slowly. This technique should also work well for other partially enclosed water bodies.     

Summary of Development and Field Testing of the Transrec Oil Recovery System

This paper summarizes the development, field testing and performance evaluation of the Transrec oil recovery system including the Framo NOFO Transrec 350 skimmer and multi-functional oil spill prevention and response equipment and presents performance data, not published before, from full-scale experimental oil spills in the North Sea from 1981 to 1990. The rare data provides useful information for evaluation of mechanical clean-up capabilities and efficiency, in particular, for responders who are using this equipment in many countries around the world.The development of the Transrec oil recovery system represents one of the most comprehensive efforts funded to date by the oil industry in Norway to improve marine and open ocean oil spill response capabilities. The need for improvements was based upon early practical user experience with different oil recovery systems, and test results from experimental oil spills in the North Sea.The result of the development efforts increased: (1) skimmer efficiency from approximately 15–75% (it reached 100% under favorable environmental conditions); (2) oil emulsion recovery rate from approximately 20–300 m³/h; (3) recovery system efficiency from approximately 15–85% in 1.5 m significant wave height; (4) oil emulsion thickness from approximately 15–35 cm; (5) weather-window for mechanical recovery operations from 1.5 to 3.0 m significant wave height; (6) capability for transfer of recovered oil residue to shuttle tankers in up to 4 m significant wave height and 45 knot winds; (7) capability for operations at night.The new Transrec oil recovery system with the special J-configuration virtually eliminated skimming operation downtime, and damage to booms and equipment failures that had been caused by oil spill response vessel (OSRV) problems with maintaining skimming position in the previous three-vessel oil recovery system with the boom towed in U-configuration. The time required to outfit OSRVs dropped from approximately 30–<1 h, reducing time from notification to operation on site by more than 24 h.Improvement in oil recovery resulted in the acceptance of a new oil spill preparedness and response plan. The new plan reduced the need for oil recovery systems from 21 to 14, towing vessels in preparedness from 42 to 18, and personnel on stand-by from 135 to 70, which subsequently reduced the total contingency and operational costs by almost 50%. These cost reductions resulted from lower contingency fees for personnel, fewer towing vessels on stand-by, less expensive open ocean training and exercises, less equipment and reduced storage space to lease, and simplified equipment maintenance.     

Quantitative analysis of alternate oil spill response strategies using OSCAR

A three-dimensional numerical model of the physical and chemical behavior and fate of spilled oil has been coupled to a model of oil spill response actions. This coupled system of models for Oil Spill Contingency and Response (OSCAR), provides a tool for quantitative, objective assessment of alternative oil spill response strategies. Criteria for response effectiveness can be either physical (‘How much oil comes ashore?’ or ‘How much oil have we recovered?’) or biological (‘How many biologically sensitive areas were affected?’ or ‘What exposures will fish eggs and larvae experience in the water column?’). The oil spill combat module in the simulator represents individual sets of equipment, with capabilities and deployment strategies being specified explicitly by the user. The coupling to the oil spill model allows the mass balance of the spill to be affected appropriately in space and time by the cleanup operation as the simulation proceeds. An example application is described to demonstrate system capabilities, which include evaluation of the potential for both surface and subsurface environmental effects. This quantitative, objective approach to analysis of alternative response strategies provides a useful tool for designing more optimal, functional, rational, and cost-effective oil spill contingency solutions for offshore platforms, and coastal terminals and refineries.     

Langmuir Circulation and the Dispersion of Oil Spills in Shallow Seas

Aspects of Langmuir circulation (Lc) which relate to the dispersion of floating material are reviewed. These include convergence, dispersion by advection (particularly of a plume of floating oil when wind and current are in different directions) and the spread and dispersion by cell instability or breakdown first described by Csanady. There are, however, processes which compete with Lc to diffuse floating material. In shallow tidally mixed seas, where the environmental impact of an oil spill may be greatest, cross-wind dispersion caused by Lc will dominate over that produced by bottom turbulence if the ratio of the wind speed, W, to current, U, is sufficiently large. Observations and rough estimates suggest a transition near W/U=15. A simple model is devised to estimate cross-wind dispersion in shallow unstratified waters when turbulence generated at a flat seabed dominates that produced by Lc, but when the effects of Lc are still evident in aligning filaments of oil, as may commonly be the case in moderate winds in coastal or continental shelf waters.     

Maersk Navigator oil spill in the great channel (Andaman Sea) in January 1993 and its environmental impact

Observations on oil slicks, tar residues and dissolved petroleum hydrocarbons (DPH) shortly after the oil spill resulting from the tanker accident in January 1993 showed negligible impact on the Indian EEZ of the Great Channel (Andaman Sea). DPH were between 0.31 and 1.85 μg l⁻¹ in the area examined. Tar residues were absent throughout the study area. Prevailing NE wind with resultant SW surface current appears to have pushed the oil patches out towards the open Indian Ocean.A follow-up survey of the same area was carried out in September-October 1993 and observations similar to those made during the earlier survey were recorded. The zooplankton biomass had increased considerably during the interval between the two surveys, but this was probably due to seasonal changes and natural variability.The spill did not cause any perceptible impact on the environment.     

Sensitivity of Water Quality Model Results for the Dutch Coastal Zone to the Distribution Coefficient of Cadmium

Results of a water quality model of the Dutch coastal zone appeared to be highly sensitive for the distribution coefficient particulate/dissolved (K_d) of cadmium.Field data of the Dutch coastal zone were used to calculate the annual and seasonal trend in the distribution coefficient of cadmium over the years 1983–88. A strong seasonal and spatial gradient in the distribution coefficient was found with relatively high values in summer and lower values in winter (K_d=3.0–7.0 log l/kg). Near the coast (2 km) the K_d was lower than more offshore (70 km from the coast). In addition, values for the distribution coefficient for cadmium were extracted from the literature (K_d=2.9–4.7 log l/kg).The range of K_d values obtained from the field data was used to perform model simulations for cadmium, in order to determine the sensitivity of the model to the distribution coefficient. The modelled yearly averaged concentrations of dissolved cadmium at one location 10 km from the coast, ranged from 0.005–0.035 μg/l, depending on the magnitude of the K_d used in the simulation. These concentrations are low compared to measured values (0.053 μg/l) due to an underestimation of the cadmium input to the North Sea, or possibly the occurrence of bottom-water exchange processes which the model does not include.     

Removal of Oil from the Sea Surface through Particulate Interactions: Review and Prospectus

The fate of oil spilled in coastal zones depends in large part on the interactions with environmental factors existing within a short time of the spill event. In addition to weathering which produces changes in the chemistry of the hydrocarbon stock, physical interactions between oil and suspended particulate matter (SPM), both organic and inorganic, play a role in determining the dispersal and sedimentation rates of the spill. This in turn affects the degradation rate of the oil. This paper provides a comprehensive literature review of the role of oil–particle interactions in removal of petroleum hydrocarbons from the sea surface and provides estimates of the degree to which SPM may augment the deposition of oil. Both field and laboratory observations have shown widely varying rates of oil removal due to particulate interactions. The discussion covers the interaction between oil weathering, injection, sinking, adsorption, microbial processes, flocculation and ingestion by zooplankton, which all contribute to packaging oil and SPM into settling aggregates.