EVALUATION OF CEMENT DUST STABILIZATION
OF POLYCHLORINATED BIPHENYL-CONTAMINATED SLUDGES
Marshall K. Sonksen, Senior Mechanical Engineer
Alcoa Davenport Works
Davenport, Iowa 52808
John A. Lease, Senior Environmental Engineer
Alcoa, Arkansas Operations
Bauxite, Arkansas 72011
Alcoa is the world's largest producer of aluminum products. Founded in Pittsburgh, Pennsylvania, in 1888, it now has mining and fabrication facilities situated around the world.
Alcoa's principal activities include mining bauxite, alumina and chemical production, and
smelting and fabricating of aluminum into semifinished and finished products. Alcoa has also
diversified into a variety of businesses related to its basic facilities and technology.
Alcoa's principal fabricating process is the rolling of aluminum into plate, sheet and foil.
The company's Davenport Works is a major rolling mill. This facility is more than one mile
in length and is situated on a 445-ac site along the Mississippi River in Davenport, Iowa. The
plant has approximately 120 ac under roof and ships over 1 million lb/day of aluminum.
Davenport's aluminum ends up in such familiar products as Saturn rockets and space capsules, the space shuttle, virtually all domestically produced commercial airliners, along with
many over-the-road cars and semi-trailers.
BACKGROUND
In 1956 a surface impoundment was constructed at Davenport Works for the storage of
waste oil from the manufacturing operations, and, in particular, for the oily sludge produced
by an alum/lime oily waste treatment plant. The impoundment was located in a natural
depression south of the plant where little excavation was required. It was situated in natural
silty clay soil and no artificial liner was installed. The impoundment is bounded on the south
and west by manmade clay dikes and cores installed to bedrock for flood protection.
Since installation of the surface impoundment, oil has been removed from the surface for
fuel use. Separated water from the bottom of the impoundment was discharged into the
Mississippi River. This practice of water removal was discontinued in 1966 when all water
was returned to the waste treatment facility for treatment prior to discharge.
In 1966 efforts were started to reduce dependence on the surface impoundment for
sludge disposal. Two 106-gal tanks were installed for scrap oil storage to permit more rapid
removal of oil from the impoundment. A 24-million Btu/hr waste oil incinerator was installed in 1969 for disposal of oily sludge as produced. This was used for disposal until 1976
when sludge disposal via outside contractor was started. In 1976 a new $1.5 million ultrafiltration oily waste treatment plant was installed which reduced sludge production by 80%.
The Problem
In 1979 it was discovered that some material in the surface impoundment contained poly-
chlorinated biphenyls (PCB). Onsite oil reclamation and water removal were stopped until a
program to properly identify the contamination could be developed. Since shoreline grab
samples indicated the presence of PCB in some areas of the impoundment, a consultant was
hired to survey the entire impoundment to determine the magnitude of the contamination.
The survey was conducted by sampling from three elevations at each intersection of a 50-
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