Pondcrete

Pondcrete
Pondcrete is a mixture of cement and sludge .
Its role is to immobilize hazardous waste and, in
some cases, lower-level radioactive waste, in
the form of solid material. The material was
used by the United States Department of Energy
and its contractor, Rockwell International , in an
attempt to handle the radioactive waste from
contaminated ponds in the Rocky Flats Plant for
burial in Nevada desert. Portland cement is
mixed with sludge to solidify into “pondcrete”
blocks and placed into large, plastic lined boxes
[1] . The sludge is taken from solar evaporation
ponds which are used to remove moisture from
waste materials, therefore reducing their
weight. To do this, liquid waste is poured into
artificial, shallow ponds. The waste is heated by
solar radiation and any moisture is evaporated,
leaving behind the waste. These ponds
contained low level radioactive process waste as
well as sanitary sewage sludge and wastes [2] ,
which categorize them and the Pondcrete as a
mixed waste.
Because the blocks were classified as mixed
waste, Rockwell International was unable to
store the blocks in the Nevada Test site. The site
did not have a permit to store mixed waste, so
the blocks were temporarily stored at Rocky
Flats. Due to problems in production, many of
the blocks did not harden correctly and
eventually began to seep from the boxes and
cause large scale environmental damage to the
area [3] . The blocks, containing radioactive
waste with a half-life of 24,000 years had failed
in a year. Despite warnings by engineer Jim
Stone that the blocks would most likely fail
earlier than expected, the blocks were still
produced. Later it would be Jim Stone which
would file a lawsuit against the company,
claiming that they had concealed
environmental, safety and health problems from
the United States Department of Energy[4] . The
contaminations lead to an investigation of the
Plant by the Federal Bureau of Investigation and
the Environmental Protection Agency which
eventually resulted in its shutdown.