The site is in south-central Des Moines on the east side of a bend in the Raccoon River and was listed on the NPL in September 1983. In all, the site encompasses more than 200 acres of which the Dico, Inc. (Dico) property occupies approximately 43 acres. The property includes several buildings that were used for a variety of industrial uses and operations including steel wheel manufacturing, chemical herbicide distribution, and pesticide formulation/distribution processes. Hazardous substances known to have been released during Dico’s operations at the site include: trichloroethene (TCE), 1,2-dichloroethene (DCE), and vinyl chloride (all found in groundwater); residual pesticides, polychlorinated biphenyls (PCBs), and metals (all found in shallow soils); and pesticides, asbestos and PCBs within buildings and building construction materials. Buildings to be addressed in this removal action include the buildings known as Buildings 1, 2, and 3.
Dico produced various pesticides/herbicides including 2,4-trichlorophenoxyacetic acid (2,4-D) and 2,4,5-trichlororphenoxyacetic acid (2,4,5-T), chlordane, dieldrin and aldrin. The results of previous sampling detected in several of the building materials samples residual levels of pesticides/herbicides.
Dioxins are known to be contaminants generated during the production of 2,4,5-T. Sampling and analyses for dioxin equivalents at the site were not above health threat screening criteria but were included in the cumulative risk assessment for the site. Polychlorinated biphenyls, PCBs, were also detected in several of the June 2016 building material samples. The highest PCB detection, 58 parts per million (ppm), was found in Building 3 in a sample of the epoxy paint and building construction material (expansion joint compounds). Previous samples from another area in the buildings showed even higher concentrations of PCBs within the buildings’ construction materials used for roofing/insulation. Of the construction materials (bricks/concrete) sampled from various locations in the buildings, analytical results showed residual levels of the various organo-pesticides handled by the previous business operations. Previous site investigation sampling and analytical results has shown that the building construction materials have previously been in direct contact with releases of hazardous substances during mixing, packaging and storage operations. These substances are adhering or have been absorbed into the immediate interior surface of the buildings. Concentrations of these residual contaminants were evaluated as a direct contact threat in the risk assessment for the site.
For several years, the City of Des Moines has been planning and executing redevelopment projects within the River Point West area east of the Dico property. The city has rezoned the area, including the Dico property, from Industrial to Central Business Mixed Use District C-3 B. The new zoning established a change in the exposure basis for re-evaluating appropriate cleanup strategies for the Dico property. The change in land use will result in hazardous substances within the buildings presenting potential and/or actual exposures to human health and the environment. Dismantling and off-site disposal of the buildings will address those threats.