An evaluation of solidification/stabilization technology for Buffalo River sediment

Abstract

Abstract: The Buffalo River drains a 446-square-mile (1,155-sq-km) watershed in western New York State and discharges into Lake Erie at the city of Buffalo. The Buffalo River has been classified by the State of New York as a "fishing and fish survival" stream, but municipal and industrial discharges have degraded the water quality and resulted in a fish advisory for the river. Under the Assessment and Remediation of Contaminated Sediment Program, the US Environmental Protection Agency asked the US Army Corps of Engineers to evaluate solidification/stabilization (S/S) for potential treatment of the contaminated sediments in the Buffalo River. An evaluation of S/S technology was conducted on the bench-scale level on Buffalo River sediment to determine whether physical and chemical properties of the sediment would be improved. Based on analyses of the untreated sediment, five metals were selected for evaluation: chromium, copper, lead, nickel, and zinc. Initial screening tests (ISTs) were conducted on the sediment to narrow the range of binder-to-soil ratios (BSRs) to be prepared in the detailed evaluation. Three binder materials were evaluated: cement, kiln dust, and lime/fly ash. Based on the results of the IST, BSRs were selected for the detailed evaluation. Specimens were prepared by mixing sediment and binder materials in a Hobart K455S mixer and molding the mixture. The specimens were cured for 28 days at 23°C and 98-percent relative humidity. Physical tests including unconfined compressive strength (UCS), freeze/thaw durability, and wet/dry durability were run to determine if the physical handling properties of the sediment were improved. UCS values less than 50 psi (350 kPa) and loss of 30 percent of the solids from the wet/dry or freeze/thaw specimens constitute failure of the UCS, wet/dry, and freeze/thaw, respectively. Contaminant release tests were conducted to determine the effectiveness of the binder materials on immobilization of the contaminants. Based on the results of the UCS tests, specimens were selected for evaluation of contaminant release properties. The S/S specimens were subjected to the US Army Engineer Waterways Experiment Station serial leach test (SLT) and the toxicity characteristic leaching procedure (TCLP). The SLT results were compared to the drinking water standards, and the TCLP results were compared to the levels required for the maximum concentration of the contaminant in the TCLP extracts.