OIL CONTAINMENT BOOM

A. GENERAL

B. BOOM CHARACTERISTICS AND NOMENCLATURE

Although boom can be classified several different ways, most types of boom share many of the characteristics shown in the drawing above. The drawing shows an "end on" look at a section of boom. The boom consists of a fabric "fence" made of a flexible material. A tension member (such as a piece of cable) of greater strength than the fabric prevents the fabric from tearing under stress. Some sort of ballast such as chain or weights is attached to the bottom of the fabric to keep the boom vertical in the water. Flotation material keeps the boom afloat. There are several different designs and methods of flotation. Floats may be rigid or flexible. Inflatable air chambers may be used to provide flotation. Freeboard is the vertical height of a boom above the water line. The freeboard prevents oil from washing over the top of the boom. If there is too much freeboard, however the boom may be pushed over in high winds. The part of the fabric below the floats is called the skirt. The skirt prevents oil from being swept underneath the boom. End connectors are used to connect sections of boom together. Since there are many different types of boom there are many types of end connectors. You can view several styles of end connectors.

In addition, boom may have some or all of the following features:

• Anchor points

• Bridles

• Handholds

• Lifting points

• Stiffeners

• Tow bars

The most important characteristic of a boom is its oil containment or deflection capability, determined by its behavior in relation to water movement. It should be flexible to conform to wave motion yet sufficiently rigid to retain as much oil as possible. No boom is capable of containing oil against water velocities much in excess of 1 knot acting at right angles to it. The escape velocity for most booms is around .7 knots, irrespective of skirt depth.

The illustration below compares the performance of booms with a rigid skirt with booms with a flexible skirt in waves. Flexible boom has better wave following characteristics.

C. TYPES OF OIL BOOM

Boom might be classified by its area of use, or by purpose, or by its type of construction.

• Classifying Boom By Area of Use

  • Open Water Boom: is of more sturdy construction and has greater freeboard and draft.

  • Protected Water Boom: is used in calmer protected waters and has less freeboard and draft.

  • Intertidal Boom: is boom used in areas in which the water bottom is periodically flooded and then uncovered by tidal action.
    

    
    

• Classifying Boom By Purpose

  • Intertidal Boom: Intertidal boom is designed to make a seal at the water/shoreline interface. Usually one end of this boom is anchored on the dry shore. The boom stretches from the shore out across the surface of the water and floats on the water. As the tide goes out and the water level drops this boom sits on the exposed bottom. When the tide comes in the boom once again floats. Thus oil on the water cannot get around the shoreline end of this boom as the water surges in and out. Water is the common type of ballast used in this boom.

    
    

  • Collection, Containment, Diversion Boom: Examples are curtain boom and fence boom. In general, curtain boom is used in rougher offshore areas and fence boom is used in areas closer to the shore or inland. These oil booms serve the standard purposes of containing, collecting, or deflecting spilled oil.

  • Specialty Boom

    • Fire Boom: Used, as the name implies to contain oil while it is set on fire and burned. Thus fire boom must have features that permit it to endure under extreme temperatures for a period long enough to serve it's purpose. This boom is constructed of fire resistant materials such as ceramic textiles and stainless steel mesh. This boom is used during "In-Situ Burning".

      
      

    • Oil Trawl: A curtain boom with air inflatable flotation bladders which contains netting and is designed to reduce turbulence in the pocket formed by the boom so that oil can be more easily skimmed. The netting also serves the purpose of collecting tar balls and other larger globules of oil.

    • Skimming Boom: This is oil boom which incorporates a method of skimming oil. An example is the Vikoma 3-Weir Boom shown below. The boom is deployed off a reel and weirs in the catenary of the boom take in the oil which is then pumped to a recovery vessel. Thus the collection of the oil and the skimming of the oil take place simultaneously with the same piece of oil recovery equipment.

      

    • Weir Boom
      

    • Sorbent Boom and Barriers: These are specialized containment devices that absorb oil in porous materials such as straw or synthetic materials. They are used when the oil slick is relatively thin because their efficiency rapidly decreases once the porous surface is saturated with oil. The drawbacks to sorbent boom are: it requires considerable additional support to avoid breakage under the force of wind/current; it often requires some method of additional flotation to prevent sinking when saturated with oil and water; a great deal of caution must be used to prevent the contaminated side of the boom from turning over and recontaminating the water.

  Classifying Boom by Construction

  There are two basic types of booms in service today: Fence and Curtain booms.

  • Fence Boom: These booms have a rigid or semi-solid material as a vertical screen against oil floating on the water. Fence booms are usually easy to deploy, resistant to damage, and bulky for storage. They can be further classified according to the type of flotation used:

    

  • Fence Boom
    

    • Centerline flotation

    • Outboard flotation on one side

      

      Fence Boom with outboard floats on one side.
      

    • Outboard flotation on two sides
      

      

      Fence Boom with outboard floats on both sides
      

  • Curtain Boom: These booms have flexible skirts which are free to move independently of the floats. They have centerline flotation provided by air, inert gas, solid foam bars, flexible foam roll, or granulated foam contained in a plastic cylinder.

    

  • Curtain Boom with flexible flotation foam.

    
    

    

     

     

    

  • Inflatable Curtain Boom
    

    The most important difference between fence and curtain booms is how they respond to wind, waves, and currents. Fence boom has the skirt and freeboard mechanically coupled together causing them to move as a single unit. If current and wind roll a fence boom away from the vertical, they also lose freeboard and draft. And if fence boom is too rigid to conform to the surface of a passing wave, there is also a loss of freeboard and draft. Flexible curtain boom has a skirt that is free to move independently of the flotation and freeboard.

  D. BOOMING TECHNIQUES

  There are five basic booming techniques:

  • Exclusion booming

  • Diversion booming

  • Containment/Collection booming

  • Sorbent booming

  • Sorbent barriers

  Exclusion Booming: Boom is deployed across or around a sensitive area to prevent a pollutant from contaminating the area.
  

  Diversion Booming: Boom is deployed at an angle to the approaching pollutant. Thus the pollutant is either diverted away from a sensitive area or diverted to a central collection point for recovery. This technique is used primarily in inshore, river, or harbor areas. Diversion booming must take into account the velocity of the flow of water and boom must be angled appropriately so that the force of the water flow against the boom does not cause oil to flow under the boom or damage the boom.

  
  

  The boom is typically laid out in a Chevron pattern or a Cascading pattern. In the Chevron pattern the boom is angled so that all floating oil and debris is deflected to either side of the stream. In the Cascading pattern varying lengths of boom are progressively staggered along the waterway so that the oil is directed to one side. Numerous anchors and firm shoreline anchoring must be employed with boom used for diversion in watercourses with strong current because tremendous forces are exerted on the boom.

  
  

  Containment/Collection Booming: Boom is deployed in a U or a J shape in front of the approaching pollutant. The ends of the booms are anchored or secured to vessels. Often skimmers are deployed in the pocket created by these formations and oil recovery takes place simultaneously. This technique is primarily used in the open water with offshore boom.

   

  U Formation	J Formation

  
  

  Sorbent Booming: Boom composed of sorbent material is typically deployed along a shoreline to protect sensitive areas or to keep heavier, emulsified oils from spreading. Used primarily on quiet waters that are not heavily contaminated.

  Sorbent Barriers: Usually constructed of wire or mesh, stakes and loose sorbent materials a sorbent barrier is often deployed across a waterway or outfall. It allows water to flow through it but retains and absorbs oil on the water surface. Useful in small, low-velocity streams, tidal inlets or channels.

   

  ---

  Back To Oil Spill Response