Project Objectives

treatment train is assembled and pilot-scale testing is conducted in the field.

Costs to contract intermediate and pilot testing are typically high given that

mobilization/demobilization and equipment costs are relatively insensitive to the

volume being processed, and most vendors cannot accept contaminated

sediments for pilot testing in-house. Availability of a mobile hydrocyclone unit

could result in significant cost savings for feasibility evaluations and small-scale

projects, and ultimately facilitate full-scale implementation of this technology.

The long-term goal is assemble a mobile physical separation plant suitable for

separation of sediments and dredged material to serve the Great Lakes CDFs.

Questions remaining to be addressed before full-scale implementation is

feasible include the following:

a. The degree of bulking of residual materials, with and without flocculants,

and the short- and long-term effects on CDF capacity recovery.

b. Alternatives for dewatering residual materials to minimize bulking

effects, and their cost, effectiveness, and effect on suitability of residual

materials for beneficial uses.

c. The relative benefit and feasibility of making finer separations (silt/clay)

to recover additional material from CDFs.

d. Evaluation procedures for determining the potential contaminant levels

in fine residuals and the effect on the regulatory classification of these

materials.

e. Development of cost/benefit algorithms incorporating all of these

considerations for economic feasibility evaluations.

Project Objectives

Identification and purchase of a portable hydrocyclone unit suitable for

conducting separation feasibility evaluations and a small-scale field

demonstration was the principal objective of this project. While the predominant

focus is coarse material recovery for beneficial use as beach nourishment and

construction fill (typically requiring the material to contain less than 10-

15 percent fines), some beneficial uses will accommodate higher percentages of

fine material. The silt/clay separation is expected to be an important long-range

objective in maximizing material recovery from CDFs for material in which the

silt fraction is substantially less contaminated than the clay fraction. Separation

capability at the sand/silt interface (approximately 75 microns) with the

additional capability of a silt/clay separation (at 2-3 microns) were therefore the

principal operating specifications. Additional criteria were (a) level of expertise

required for operation, (b) auxiliary equipment required to support operation, and

other information gaps, as previously described.

Chapter 1 Introduction