More than 2,000 gallons of toxic and flammable liquid was expelled from the residue treater, ruptured
piping, and other equipment, most of which burned in the ensuing fire. Although the residue treater
feed contained significant quantities of methomyl and MSAO, those chemicals were rapidly
decomposing in the residue treater. Post-incident, trace amounts of methomyl were found in swipe
samples from equipment in the vicinity of the explosion; however, the specific quantities of undecomposed
or unburned methomyl or other toxic chemicals that might have escaped into the
atmosphere were indeterminate.
The MIC day tank and cross-unit transfer piping were not damaged in the incident. However, the
liquid in the residue treater contained significant quantities of methomyl and MSAO products of
decomposition and possibly some quantity of methyl isocyanate.48
48 The flasher bottoms likely contained small amounts of MIC, and MIC could have been one of the products of
the methomyl decomposition reaction.
MIC might have also been
released from ruptured process piping and vent piping. MIC is flammable and highly reactive with
water; at least some of any released MIC likely burned in the fire or reacted with the water used to
88
fight the fires. There were no reports of river water contamination or other offsite ground
contamination.