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Assessment and Remediation of Contaminated Sediments (ARCS) Program

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Objective and Scope
Organization of the Report

Sediment Sample Collection and Analysis
Preparation of Test Specimens
Physical and Contaminant Release Testing

Physical Strength Testing
Wet/Dry and Freeze/Thaw Testing
Contaminant Release Testing for Metals
Contaminant Release Testing for Organics
Alternatives for Application of S/S to Buffalo
  River Sediment
Comparisons of Buffalo River Results to
  Other Sites



An Evaluation of Solidification/Stabilization Technology for Buffalo River Sediment

Source: Fleming, E. C., D. E. Averett, M. G. Channell, B. D. Perry. 1991. Abstract and Table of Contents to "An Evaluation of Solidification/Stabilization Technology for Buffalo River Sediment," Miscellaneous Paper EL-91-11. Vicksburg, Miss.: US Army Engineer Waterways Experiment Station.


Elizabeth C. Fleming, Daniel E. Averett, Michael G. Channell, Bret D. Perry

Environmental Laboratory

Waterways Experiment Station, Corps of Engineers
3909 Halls Ferry Road, Vicksburg, Mississippi 39180-6199

May 1991

Final Report

Approved For Public Release; Distribution Unlimited

Prepared for US Environmental Protection Agency
Great Lakes National Program Office
Assessment and Remediation of Contaminated Sediment Program
Chicago, Illinois 60604

Monitored by US Army Engineer Division, North Central
Chicago, Illinois 60605-1592



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.




1. The Buffalo River drains a 446-square mile* watershed in western New York State and discharges into Lake Erie at Buffalo, NY. The Buffalo River Area of Concern is illustrated in Figure 1. Although the State of New York has classified the Buffalo River as a "fishing" stream, municipal and industrial discharges into the river have degraded water quality. As a result, taking of fish for consumption from the river has been restricted by the State of New York. Although abatement efforts have reduced the discharges of contaminants to the river, residual contaminants in bottom sediments are believed to contribute to continued water quality impairment of the river (New York State Department of Environmental Conservation (NYDEC) 1989).


2. Effects of contaminated sediment on water quality can be reduced by a number of control or treatment technologies. Alternatives for reducing or eliminating contaminant transport from the sediment into the water column include isolating the contaminated sediment from the water by capping with a layer of clean sediment or chemically solidifying the sediment in place. Other remediation options involve removing the contaminated material from the waterway and treating or disposing of the dredged material so that contaminants are removed, destroyed, immobilized, or efficiently contained within a disposal site. However, treatment options that efficiently extract or destroy contaminants are expensive, and unrestricted disposal in a confined disposal facility provides the potential for leaching of contaminants and pollution of groundwater or surface water.

3. Solidification/stabilization (S/S) is a promising treatment technology for containing and immobilizing dredged material contaminants within a disposal site. S/S technology has been applied in Japan to bottom sediments containing toxic substances (Otsuki and Shima 1982, Kita and Kubo 1983) and in the United States to industrial wastes (Cullinane, Jones, and Malone 1986; US Environmental Protection Agency (USEPA) 1989). Laboratory investigations of S/S of dredged material have been performed for Indiana Harbor, Indiana (Environmental Laboratory 1987); Everett Bay, Washington (Palermo et al. 1989); and New Bedford Harbor, Massachusetts (Myers and Zappi 1989). While S/S is not a solution to every disposal problem, the technology offers improved physical characteristics that reduce the accessibility of water to contaminated solids and reduced leachability for many contaminants.

4. Myers and Zappi (1989) have described S/S for dredged material. Solidification is the process of eliminating the free water in a semisolid by hydration with a setting agent(s) or binder(s). Stabilization can be both physical and chemical. Solidification usually provides physical stabilization but not necessarily chemical stabilization.

5. Physical stabilization refers to improved engineering properties such as bearing capacity, trafficability, and permeability. Alteration of the physical character of the material to form a solid material reduces the accessibility of water to the contaminants within a cemented matrix and entraps or microencapsulates the contaminated solids within a dimensionally stable matrix. Since most of the contaminants in dredged material are tightly bound to the particulate fraction, physical stabilization is an important contaminant immobilization mechanism (Myers and Zappi 1989).

6. Chemical stabilization is the alteration of the chemical form of the contaminants to make them resistant to aqueous leaching. S/S processes are formulated to minimize the solubility of metals by controlling pH and alkalinity. Anions, which are more difficult to bind in insoluble compounds, may be immobilized by entrapment or microencapsulation. Chemical stabilization of organic compounds may be possible, but the mechanisms involved are poorly understood (Myers and Zappi 1989).

7. Binders include cements, pozzolans, or thermoplastics (Cullinane, Jones, and Malone 1986). In certain instances, proprietary additives may also be added to the process. Results of reactions of binders to the contaminated sediment are not always predictable due to varying contaminant types and concentrations within the test material. Therefore, laboratory leach tests must be conducted on a sediment-specific basis. Discussions of S/S processes are provided in Malone and Jones (1979); Malone, Jones, and Larson (1980); and USEPA (1986a).

8. Binders selected for potential application to Buffalo River sediment are:

  1. Portland cement.
  2. Lime/fly ash.
  3. Kiln dust.

These binders were selected because of their nonproprietary nature and ready availability. They have been used in a number of S/S studies at the US Army Engineer Waterways Experiment Station (WES), including assessment of best demonstrated available technology for a number of listed hazardous wastes. Portland cement addition results in the formation of a concrete-like monolith. Lime/fly ash pozzolanic processes combine the properties of lime and fly ash to produce low-strength cementation. Kiln dust processes involve the addition of kiln dust to eliminate free liquids and usually form a low-strength solid.

9. Because the above binder systems are not always effective for organics, addition of activated carbon to the portland cement process was investigated as a fourth S/S process. The purpose of the activated carbon is to adsorb contaminants. The activated carbon particles along with the adsorbed contaminants may then become physically bound within the solid matrix produced by the cement.

Objective and Scope

10. The objectives of this study were to:

  1. Evaluate the effects of S/S treatment on contaminant mobility for Buffalo River sediment.
  2. Evaluate improvements in the physical handling properties of Buffalo River sediment by S/S.
  3. Determine if activated carbon addition to a portland cement process will enhance contaminant immobilization.

11. The scope of the study involved laboratory preparation of S/S samples using Buffalo River sediment and the following binders/additives: portland cement, lime (slaked)/fly ash, kiln dust, and portland cement with powdered activated carbon. A range of weight binder-to-weight wet sediment ratios (BSRs) were screened, and an optimum ratio was selected for detailed evaluation for each binder process. Effectiveness was measured by comparing leaching results, unconfined compressive strength (UCS), and durability under wet/dry and freeze/thaw cycles.

Organization of the Report

12. This report is divided into four parts:

  1. Part I provides the background information around which this study evolved.
  2. Part II describes the materials and methods used to evaluate S/S of the Buffalo River sediment and S/S with carbon-treated sediment.
  3. Part III discusses the results of the physical and chemical tests run on the S/S sediment and S/S carbon-treated sediment.
  4. Part IV presents conclusions and recommendations regarding S/S of Buffalo River sediment.


American Society for Testing and Materials. 1988a. "Standard Test Method for Compressive Strength of Hydraulic Cement Mortars; Cement, Lime, Gypsum," ASTM Designation C 109-88; Vol 04.01, Annual Book of ASTM Standards. Philadelphia, PA.

__________ 1988b. "Standard Test Method for Wetting and Drying Test of Solid Wastes; Water and Environmental Technology," ASTM Designation D 4843-88; Vol 11.04, Annual Book of ASTM Standards. Philadelphia, PA.

Bricka, R. Mark, Holmes, Teresa, and Cullinane, M. John. 1988. "An Evaluation of Stabilization/Solidification of Fluidized Bed Incinerator Ash (K048 and K051)," Technical Report EL-88-24, US Army Engineer Waterways Experiment Station, Vicksburg, MS.

Cullinane, M. J., Jr., Jones, L. W., and Malone, P. G. 1986. "Handbook for Stabilization/Solidification of Hazardous Waste," US Environmental Protection Agency, EPA/540/2-86/001, Cincinnati, OH.

Environmental Laboratory. 1987. "Disposal Alternatives for PCB-Contaminated Sediments from Indiana Harbor, Indiana; Vol II," Miscellaneous Paper EL-87-9, US Army Engineer Waterways Experiment Station, Vicksburg, MS.

Headquarters, Department of the Army. 1971. "Materials Testing," Technical Manual No. 5-530, Section XV, Washington, DC.

Kita, D., and Kubo, H. 1983. "Several Solidified Sediment Examples," Proceedings of the Ninth Annual US/Japan Experts Meeting Management of Bottom Sediments Containing Toxic Substances. US Army Engineer Water Resources Support Center, Fort Belvoir, VA.

Malone, P. G., and Jones, L. W. 1979. "Survey of Solidification/ Stabilization and Technology for Hazardous Industrial Wastes," EPA/600/2-79/ 056, US Environmental Protection Agency, Cincinnati, OH.

Malone, P. G., Jones, L. W., and Larson, R. J. 1980. "Guide to the Disposal of Chemically Stabilized and Solidified Waste," SW-872, Office of Water and Waste Management, US Environmental Protection Agency, Washington, DC.

Myers, Tommy E., and Zappi, Mark E. 1989. "New Bedford Harbor Superfund Project, Acushnet River Estuary Engineering Feasibility Study; Report 9, Laboratory-Scale Application of Solidification/Stabilization Technology," Technical Report EL-88-15, US Army Engineer Waterways Experiment Station, Vicksburg, MS.

New York State Department of Environmental Conservation (NYDEC). 1989. "Buffalo River Remedial Action Plan Summary," Buffalo, NY.

Otsuki, T., and Shima, M. 1982. "Soil Improvement by Deep Cement Continuous Mixing Method and Its Effect on the Environment," Proceedings of the Eighth Annual US/Japan Experts Meeting. Management of Bottom Sediments Containing Toxic Substances. US Army Engineer Water Resources Support Center, Fort Belvoir, VA.

Palermo, M. R., et al. 1989. "Evaluation of Dredged Material Disposal Alternatives for US Navy Homeport at Everett, Washington," Technical Report EL-89-l, US Army Engineer Waterways Experiment Station, Vicksburg, MS.

USEPA. 1986a. "Handbook for Stabilization/Solidification of Hazardous Wastes," Hazardous Waste Engineering Research Laboratory, Cincinnati, OH.

USEPA. 1986b. "Prohibition on Placement of Bulk Liquid Hazardous Waste in Landfills; Statutory Interpretive Guidance," EPA 530 SW-86-016, OSWER Policy Directive 9487.00-24, Office of Solid Waste and Emergency Response, Washington, DC.

USEPA. 1986c. "Quality Criteria for Water," EPA/440/5-86/001, US Environmental Protection Agency, Office of Water Regulations and Standards, Washington, DC.

USEPA. 1989. Stabilization/Solidification of CERCLA and RCRA Wastes, EPA/625/6-89/022, Risk Reduction Engineering Laboratory, Cincinnati, OH.


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