The Denver Radium Superfund Site consists of over 44 properties, constituting 11 operable units, along the South Platte River within the City of Denver, Colorado, that were contaminated with radioactive residues resulting from the processing of radium in the years 1913 to 1923. The site was added to the superfund national priorities list (npl) in 1983. The Robinson Brick Company (ROBCO) property and the adjacent Denver and Rio Grande Western Railroad right-of-way form operable units IV and V of the Denver Radium Superfund Site. The radiological cleanup of these units was completed in March 1991, approximately 9 years after the initial site assessment, at an estimated cost of $22.3 million. Had a historical review been conducted in conjunction with the initial site assessments, the presence of heavy metals would have been known and more appropriate site characterization methods could have been applied, thus reducing the cleanup costs in terms of both time and money.