Draft final

BOX 4a PRE-APPROVAL MAY APPLY; REFER TO THE PRE-APPROVAL PROCESS.
The request for dispersant use may not require RRT IX Expedited Approval. Review the Pre-Approval guidelines and begin the pre-approval process if appropriate (see ENCLOSURE 4910a: Section I) .

Chart 4.1

BOX 5 CAN DISPERSANT BE REASONABLY EXPECTED TO HAVE A NET ENVIRONMENTAL BENEFIT?

Use the regional sensitive species and habitat information from the Net Environmental Benefit Analyses for each major coastal area in which dispersant use may have an impact.

Consider:

• 
  The type and value of habitat potentially affected.
  
• 
  The sensitivity of affected resources to oil, and to different oil response strategies.
  
• 
  Natural recovery rates of affected species and habitats.
  
• 
  Likely oil persistence and degradation rates with and without dispersant use.
  
• 
  Potential oil toxicity on surface water species compared to water column and/or seafloor species.
  

Decision: Will the dispersant use have a net environmental benefit?

• 
  Yes Go to Box 6.
  

• 
  No Go to Box 1c.
  

Make a note of the decision in the Dispersant Decision Summary box on the Dispersant Use Flowchart.

Discussion Note 5.1 ASSESSING NET ENVIRONMENTAL BENEFIT

The central question to be answered in assessing Net Environmental Benefit is:

Will dispersant use significantly reduce the impact of the spilled oil?

• 
  Rapid decisions on use are essential as dispersant must be applied quickly to be effective.
  
• 
  Decision-makers must consider the various environmental, social, economic, political and cultural
  

factors unique to each spill.

• 
  Tradeoffs will be necessary, as no response is likely to satisfy all parties and protect all resources.
  

The ecological impacts of oil are generally longer-lasting and more persistent than most other impacts.

• 
  Ecological effects will be due primarily to the spilled oil. Dispersant applied at recommended rates is unlikely to cause significant adverse effects, even in multiple applications.
  
• 
  Oil dispersed into water depths greater than 30 feet (~10 meters) will quickly dilute to levels where acute toxic effects are unlikely.
  
• 
  The California policy is that dispersants will not be used over water shallower than 60 feet deep.
  
• 
  Few acute toxic effects have been reported for crude oil dispersed into less than 30’ (10m) water depth if the water is well-flushed.
  

• 
  Small spills seldom require dispersants use.
  
• 
  Dispersant use is not recommended for spills of light fuels such as gasoline, jet fuel, kerosene, diesel
  

and light fuel oils.

• 
  Dispersants are not recommended for use on oil sheens.
  
• 
  Dispersant use is generally not appropriate in areas with limited water circulation and flushing, near aquaculture facilities, shellfish beds and fish-spawning grounds, and around seawater intakes.
  

• 
  

  Discussion Note 5.1 ASSESSING NET ENVIRONMENTAL BENEFIT

  
  
  The most important question to answer is: Will dispersant use significantly reduce the impact of the spilled oil?
  
  
  • 
    Rapid decisions on use are essential as dispersant must be applied quickly to be effective.
    
  • 
    Decision-makers must consider the various environmental, social, economic, political and cultural factors unique to
    
  
  each spill.
  
  • 
    Tradeoffs will be necessary, as no response is likely to satisfy all parties and protect all resources. The ecological
    
  
  impacts of oil are generally longer-lasting and more persistent than most other impacts.
  
  • 
    Ecological effects will be due primarily to the spilled oil. Dispersant applied at recommended rates is unlikely to
    
  
  cause significant adverse effects, even in multiple applications.
  
  • 
    Oil dispersed into greater than 10m or water will quickly dilute to levels where acute toxic effects are unlikely.
    
  • 
    Few acute toxic effects have been reported for crude oil dispersed into less than 10m of well-flushed water.
    
  • 
    Small spills of light fuels seldom require dispersant use.
    

  Discussion Note 5.1 ASSESSING NET ENVIRONMENTAL BENEFIT

  
  
  The most important question to answer is: Will dispersant use significantly reduce the impact of the spilled oil?
  
  
  • 
    Rapid decisions on use are essential as dispersant must be applied quickly to be effective.
    
  • 
    Decision-makers must consider the various environmental, social, economic, political and cultural factors unique to
    
  
  each spill.
  
  • 
    Tradeoffs will be necessary, as no response is likely to satisfy all parties and protect all resources. The ecological
    
  
  impacts of oil are generally longer-lasting and more persistent than most other impacts.
  
  • 
    Ecological effects will be due primarily to the spilled oil. Dispersant applied at recommended rates is unlikely to
    
  
  cause significant adverse effects, even in multiple applications.
  
  • 
    Oil dispersed into greater than 10m or water will quickly dilute to levels where acute toxic effects are unlikely.
    
  • 
    Few acute toxic effects have been reported for crude oil dispersed into less than 10m of well-flushed water.
    
  • 
    Small spills of light fuels seldom require dispersant use.