IncidentNews Home  >>  Incident  >>  Entry

Report - Trajectory

Date: March 15, 2001
  To: NOAA SSC Sharon Christopherson 
FROM: NOAA/Hazardous Materials Response Division
      Modeling and Simulation Studies
      Seattle, WA 98115
      
SUBJECT: Gasoline spill at March Point

FOR ADDITIONAL INFORMATION, PLEASE CONTACT Glen Watabayashi,
MODELING AND SIMULATION STUDIES, NOAA, SEATTLE, WA 98115.
PHONE (206) 526-6317.
_______________________________________________________
Per your request we have looked at trajectory implications of the gasoline that has been
released from a barge.  These notes are based on the following information:


At about 0700 PST, Thursday, March 15, a barge lost approximately 1,000 gallons of
gasoline from a crack.  The source has been secured and is no leaking anymore product.
Onscene winds are reported to be 20 knots from the south.


_______________________________________________________
1)Weather Forecast
Winds are expected to be from the SSE this morning 10 -20 knots becoming SW at 10 - 20
knots by mid afternoon.


2) Trajectory Analysis
The spill occurred at the start of a strong ebb and under strong south wind conditions.
Under these conditions we expect the gasoline to quickly evaporate and disperse.  By hour
2 or 3 most if not all of the product will be gone.

If any gasoline persists past hour 3, it will most likely beach along the southeast end of
Guemes Island.


3) Oil Weathering
The ADIOS II model predicts that over 90% of the gasoline will be either evaporated or
dispersed into the water column by hour 2 after the spill.


Gasoline is considered a light refined product with a specific gravity that can range from
0.76 to 0.70 at 15°C ( 54 to 70 API ).  The product typically has a very high evaporation
rate and does not tend to create persistent slicks.  For most releases smaller than 100
barrels in open water conditions and with wind speeds greater than 5 knots,  90% of the
gasoline would be expected to evaporate within the first 1 to 2 hours of the initial
release. When spilled, the gasoline spreads quickly into thin films by forming patches of
rainbow and silver sheens.  If the sheens reach the shoreline in a few hours,  a slight
staining, or greasy film is common. Normally, this type of release does not become an
involved cleanup problem.


It should be noted that gasoline does have a relatively high concentration of light
aromatic compounds and tends to be more soluble and more toxic then heavier oils.  In high
energy environments, the gasoline will likely disperse as small droplets in the water
column.  Gasoline spills can result in an initial toxic shock to biota and persist as a
biological threat particularly in low energy marine environments as often found in shallow
bays and inlets.