Case: Mobil Gypsum, TX
Date of incident: April 6, 1992.
On April 6, 1992, a 600-foot long section of retaining wall of a gypsum slurry
pile failed at the Mobil Mining and Minerals facility in Pasadena, Texas,
causing 45 million gallons of a 3 percent phosphoric acid and hydrated gypsum
mixture to spill through a small bayou and into the Houston Ship Channel. Most
of the material was released on that one day but leaking continued for several
days. This mixture flooded control ditches, open fields, and bayous.
Gypsum and phosphoric acid water are classified as toxic and hazardous materials
according to the Comprehensive Environmental Response, Compensation, and
Liability Act (CERCLA). Although the ship channel is heavily industrialized,
the nearby small bayous and wetlands are extensively used by juvenile fish and
crustaceans. The spill caused significant injuries to freshwater, marine, and
estuarine wildlife, fishes, invertebrates, plants and sediments. There was a
significant loss of habitat for terrestrial and aquatic animals in the upland
fields and drainage canals. There was also direct mortality to terrestrial
animals, primarily ground-nesting birds, rodents, and reptiles. The injury to
the surface waters was widespread. The spilled material had a Ph of 1.5. This
adversely affected the water quality within approximately 7 miles of the
Houston Ship Channel for at least one week.
Mobil undertook response actions to contain, neutralize and remove contaminated
water and soil and agreed to a compensatory restoration project. Texas and
Federal trustees entered into a consent decree with Mobil specifying the
required project and payment of costs incurred by the Trustees engaged in the