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Drill Mud Spill

Resources at Risk for Lower Atchafalaya River, Morgan City, Louisiana

I.
Spill Source Information

This report was prepared at 16:30 EST on 2/12/97.  Information in the report is based on
the assumption that a spill of 310 bbls of drilling mud occurred on the Atchafalaya River
at River mile 116.


II.
Geographic Region Covered

This report covers the area from Morgan City south to Atchafalaya Bay.  This area does not
necessarily correspond to actual or potential oil locations.  Consult other Hotline
reports for oil location information.


III.
Expected Behavior of the Spilled Material

The drilling mud is 45 percent diesel fuel.  The diesel will remain bonded to the mud.
The product will sink and remain on the bottom. The major threat is to bottom dwelling
organisms.  Impacts can come from smothering or ingestion of toxic compounds.


IV.
Shoreline Resources at Risk

There is little likelihood of the shorelines being oiled along the river banks.  The
greatest chance of shoreline oiling is in the bay.  The mud may collect on the tidal flats
at the mouth of the river.  This may impact animals associated with the mudflats,
including wading birds and waterfowl that feed on the flats.


V.
Biological Resources at Risk

Fish
The drilling mud is likely to remain mostly benthic, however with strong currents (4
knots) reported for the river, some of the drilling mud there become suspended in the
water column.  The impacts to the fish in the water column are likely to be low, because
of the low concentration of the petroleum hydrocarbons.  The greatest impacts are likely
to be to the benthic fish such as flounder and catfish.  These fish live and feed on the
river bottom and are likely to come into direct contact with the drilling mud.  The
concentrations may be high enough to cause mortality as well as sublethal effects.



Shellfish
Blue crab, brown shrimp, and white shrimp are known to be in the area.  These are bottom
dwelling organisms, and typically feed on organisms in the sediments.  These animals may
suffer sublethal impacts such as tainting and reduced reproductive success, as well as the
possibility of death.  In the open water area they are also brackish-water clams.  These
animals are at risk from smothering and since they filter feed they also bioaccumulate the
oil.  Even if exposed to relatively small amounts of oil they can accumulate enough to
taint the flesh and cause sublethal effects. At higher concentrations this may result in
mortality.



Birds
Of the birds present the ones primarily at risk are the shorebirds and wading birds that
feed on the flats.  These birds feed on organisms found on of the flats including crabs
and shrimp.  The birds may ingest oil-contaminated prey.  There is very little chance of
birds becoming oiled directly.



Mammals
Of the small terrestrial mammals in the area the river otter, mink, and raccoon are the
most likely to be impacted.  These animals may eat fish and shellfish that may have been
exposed to the oiled mud.  Mortality is not likely with the mammals.-


Reptiles
Alligators are found throughout the area.  Little is known about the impacts of oil on
these animals.  It is likely that they may consume oiled prey, but no lethal effects are
expected.  The alligators may also be exposed directly to the drilling mud in shallow
water areas.  It is possible that oil fraction may cause some irritation of the membranes
around the eyes and nostrils, but mortality is not expected.