Oil Spill Response Methods

Transcription

1 Oil Spill Response Methods Summary: This lecture gives students an overview of the equipment, procedures, and strategies used in oil spill response. This lesson builds on The Fate of Spilled Oil (although it may also stand alone). It should be followed by the Oil Spill Cleanup Lab. Grade Level: 6-12 Duration: 50 minutes Objectives: - Students will learn about strategies and types of equipment used in open water, nearshore, and onshore oil spill response. - Students will be able to describe the functions, uses, and common problems associated with skimmers, booms, and dispersants. Materials: - Oil spill response equipment powerpoint presentation - Computer and projector for slideshow - Whiteboard, markers Background: Part 1 contains an overview of the general cleanup methods and a discussion of the types of equipment used in each. For younger students (grades 6-8), part 1 will provide sufficient information on oil spill cleanup, and is sufficient background for the next lesson, the Oil Spill Cleanup Lab. Part 2 outlines oil spill response strategies for open water, nearshore, and onshore. Part 2 will be helpful background for the ICS Scenario. The accompanying powerpoint presentation by Dr. Pegau of the Prince William Sound Oil Spill Recovery Institute contains photos of the different types of skimmers and booms described in the lecture notes. The lecture notes for Part 1 below include slide numbers to correspond to the powerpoint. Lecture Notes: Part 1: There are basically four ways to clean-up oil spills. These are: mechanical containment and recovery, chemical methods such as dispersants, burning, and shoreline clean-up. In the open water and near shore, mechanical skimming of oil is considered the response method least harmful to the environment. It requires large quantities of equipment and personnel. It is a multistage process that can be time consuming

2 and has several potential bottlenecks in which the system can break down. First you need to contain the oil with booms; then you need to recover it using skimmers, store it temporarily, treat it (remove the water) and then dispose of it. In each stage you handle the oil; equipment and personnel are needed. The operation will be hampered if, in any stage, the system breaks down. Boom [SLIDE 2] - Functions: o Containment (for skimming or burning) [SLIDE 3]; bottom, a containment boom with skimmer] o Diversion (to deflect oil from an area of shoreline or hatchery) o Exclusion (to complete enclose an area of shoreline) - Parts of a boom [SLIDE 4] o Flotation may be rigid foam or inflatable air. o The skirt is the main part of the boom, and varies in size and material depending on what type of conditions the boom is designed for. It is attached to a weighted anchor which keeps the boom upright in the water. - Boom failures [SLIDE 5] o Booms can only be towed at slow speeds and in relatively calm seas. (The speed and wave height that a boom can tolerate depends on the specific boom type and tactic. Generally speeds up to 5 or 6 mph and seas up to 3 to 6 feet.) o If they are towed at higher speeds, they may not remain anchored upright in the water, and oil can be entrained under the boom. In rough seas, the boom may not stay upright or oil may spill over the top. - Types: o Light-duty boom: foam filled harbor boom used in calm and protected waters. [SLIDE 6] Light-duty boom that is used in calm water can also be made of floating sorbent material, the same material used in oil spill cleanup pads. [SLIDE 7] o Heavy-duty boom: must be inflated before use, used for towing or areas with strong currents. Used in open water areas with large swells, strong winds or tides [SLIDE 8]: This boom is towed by two boats. Oil is funneled into the chamber at the back of the V, concentrating it into a small area where a skimmer is used to skim it off. o Intertidal boom: inflated with water and air to conform to and seal the beach as the tide goes in and out. Used in calm and protected waters adjacent to beaches, estuaries and other sensitive shoreline areas. Provides continuous protection throughout the tide cycle. [SLIDE 9] o Fire boom: used to tow oil for burning [SLIDE 10] Skimmers [SLIDE 11] - Types:

3 o Suction devices: draws in oil and water like a vacuum cleaner; easily clogged with debris; high H 2 O volume o Oleophilic surface units: uses the principle of adhesion; oil adheres to a surface, and then is scraped off into a collecting tank. Most skimmers work best on fresh, non-emulsified oil. Disk [SLIDES 12 and 13] Rope: low viscosity oils [SLIDE 14 top] Belt [SLIDE 14 right] Brush [SLIDE 14 bottom left, SLIDE 15] (best for emulsified oil) o Weir skimmers: uses a weir positioned at the oil/water interface to collect the oil while collecting as little water as possible. The oil is pumped through a hose to a storage tank. Best for light/medium oil in calm waters [SLIDE 16] o Hydrodynamic devices: effective on light, thin sheen Burning [SLIDE 17] - In-situ burning works best on fresher oil and specialized equipment and trained personnel are necessary. Controversy exists about this method's effectiveness and hazards. - Burning can only be used in open-water areas (more than 3 miles away from populated areas) where fumes will not be carried to coastal communities where it can pose a health risk or cause fires to spread on shore. - Booms are used to tow and contain a mass of oil to be burned, and the oil is ignited by hand or by helicopter. Dispersant [SLIDE 18] - In open water, chemical dispersants can be used to break oil into small droplets in the upper part of the water column. In a manner similar to dish soap, chemical dispersants allow oil to disperse into the water column, so it becomes diluted and can more quickly be degraded by natural processes such as biodegradation. Some studies show that dispersants speed up natural dispersion, biodegradation and evaporation. Other studies show dispersants to be highly toxic and less effective in cold waters. To be effective, dispersants must be applied soon after a spill, since weathered oils are hard to disperse. Mixing energy from wind and waves is also needed. - Approval is required from the government before dispersants can be applied on a spill. - Most effective when applied as soon as possible (minimize surface transport) o Dispersants can be applied by plane or boat (airborne application is most rapid) - Dispersant sometimes increases and sometimes decreases the rate of biodegradation o May increase/ decrease biodegradation rates of different components at once, or rate of biodegradation by different microbes o May inhibit microbes ability to attach to and intake hydrocarbons

4 - [Dispersant chemistry: Normally water and oil do not mix because H2O is a polar molecule while petroleum consists of nonpolar hydrocarbon chains. Chemical dispersants consist of surfactant molecules with combined polar and nonpolar properties (a hydrophilic head and a lipophilic tail), so that a large mass of oil can be separated into small particles and dispersed throughout the water column.] Solidifiers [SLIDE 19] - Solidifiers cause a chemical reaction when they come in contact with oil, forming a floating rubber-like solid that is easy to remove from the water s surface. - Mixing is needed to increase contact between oil solidifying agents; can be used in rough water for natural mixing energy. - Impractical for large oil spills because large amounts of solidifier are needed for maximum effectiveness (up to 3 times the volume of the spilled oil). Shoreline clean-up [SLIDE 20] involves the physical removal of oil from beaches. This is the most labor and equipment intensive response method and techniques must be chosen carefully. Removal of oiled sediments can sometimes create environmental problems such as beach erosion. Running heavy equipment on shorelines can sometimes do more damage than the oil. A variety of shoreline clean-up methods are available. The one used depends on the beach type, its location, the type of oil and the equipment and manpower available. Citizen clean-up programs after the Exxon Valdez oil spill involved many different techniques such as oiled seaweed pickup on the beaches. Seaweed is a natural oil collector so the more picked up meant less oil that spread to other bays and estuaries. Pom-poms made of oil-absorbent material were also used to pick up oil. Bioremediation, the use of fertilizer to increase the populations of oil eating bacteria, was another technique that was tried. Also, a rock washing program was developed where rocks were cleaned by tying them up in specially designed bags so the ocean s tidal action could wash them. Oil absorbent pads were used to wipe off rocks individually and for general clean-up, i.e. boots of oil spill workers. Another response, not always recognized, is no response. After the Exxon Valdez spill, NOAA studied sites that were not cleaned up and documented considerable survival and recovery of marine life. Part 2: Response Strategies Oil spill response strategies differ depending on the environment that is being cleaned up. They can be categorized as open-water, nearshore, or onshore. Open-Water - Containment o Booms are used immediately to minimize the spread of oil and concentrate the oil as close as possible to the source of the spill. - Mechanical recovery of floating oil

5 - Non-mechanical response o Dispersants Dispersants may complement or replace mechanical recovery May be the only way to avoid shoreline impact. Usually applied by aircraft, sometimes by boat Most effective if used soon after a spill, before weathering o In-situ burning An area of oil is collected in a fire boom, ignited by helicopter Can eliminate up to 90-99% Impact on air quality is comparable to evaporation of light ends - shoreline protection: deploy booms to minimize shoreline impact Nearshore - Free oil recovery: intercept oil escaping the open water recovery operations and threatening shorelines or sensitive areas (same as open-water task forces) - Shoreline protection: protect priority sensitive areas - Hatchery protection: Deployment and support vessels to protect hatcheries in the projected path of the spill o Protective boom and related equipment is pre-staged year-round at all hatcheries in PWS. - Wildlife protection: protect and/or rescue wildlife that is in the projected path of the spill Onshore - Passive collection: sorbent booms placed over the shoreline to absorb oil - Manual removal o Oiled seaweed pickup o Rock washing (beach rocks are placed in - cold water deluge: a hose system that uses high-volume, low-pressure saturation to wash oil out of rocks and into the water, where it can be absorbed by booms or skimmed - bioremediation Cold region influences on oil spill response equipment and operations - Equipment and infrastructure o lack of roads, docks, and airstrips in remote areas o difficulty starting and maintaining engines in cold weather o blocking/ plugging of equipment from ice and snow - Logistics & communications o increased dependence upon good communications and navigation equipment o long periods of darkness in winter hinders oil detectability and reduces time for response o response rate limited by reduced visibility from snow or fog o extreme water depth variations

6 o difficulty of working in ice infested waters o drifting of snow onshore and on solid ice - Oil detectability o limited by ice, snow, or reduced visibility - Oil recovery o freezing of water with, or in, recovered oil o natural oil holding capacities of ice and snow Resources: Alaska Oil Spill Curriculum, grades 7-12 (3 rd edition). Prince William Sound Science Center and Prince William Sound Regional Citizens Advisory Council Available online at EPA Emergency Management. Oil Spill Response Techniques. NOAA National Ocean Service Office of Response and Restoration. SERVS Fishing Vessel Training Captain s Manual. Alyeska Pipeline Service Company