APPLICATION TO USACE DREDGING PROJECTS

ERDC TN-DOER-T7

October 2004

dependent upon chemical addition to flocculate the material. Under unfavorable conditions (in

which the slurry requires high dosages of flocculants) chemical costs can outweigh equipment

costs.

The fact sheets in Appendix A give a range of costs for the processes described, reflecting the

impact of less-than-optimum operating conditions. When comparing cost estimates from

different vendors, care should be taken to do so on an equivalent-cost basis. If one estimate

includes wastewater treatment and another does not, for example, it may be impossible to extract

these cost differentials and establish a uniform basis for comparison. Requests for proposals

should attempt to address this issue by specifying all cost items that are to be included or

itemized.

APPLICATION TO USACE DREDGING PROJECTS: With decreasing storage capacity

available, managers in many areas of the country are considering efforts to recover and put to

beneficial use previously dredged materials. Often transport and placement specifications

require that the material be dewatered. While this can be effectively accomplished with passive

dewatering methods, area requirements are large and time to achieve sufficient dewatering for

the materials to be workable may be lengthy. Additionally, construction costs for new CDFs are

high. Dewatering technology has matured in recent years, making material processing more

cost-competitive than in the past. Where existing upland storage is available and adequate,

mechanical dewatering will typically not be the least-cost alternative. Where storage is limited

or must be constructed, or where offsite disposal options are being considered, mechanical

dewatering may offer a reasonable alternative for some projects.

ACKNOWLEDGEMENTS: The contributions of the co-authors of this document, and the

companies with which they are affiliated, are gratefully acknowledged: John Waugh, Phoenix

Process Equipment Company, Louisville, KY; Robert L. Schwartz, Solomon Technologies and

Operations Services Corporation (while contributing to this article, now employed by Hazen

Research, Golden, CO); Glen Green and Vic Buhr, J. F. Brennan Company, LaCrosse, WI ; Bob

Braddock, Solomon Technologies and Operations Services Corporation, Lakewood, CO; Heinz-

Dieter Detzner, Department of Port and River Engineering, State Ministry for Economic and

Labour Affairs, Hamburg, Germany.

POINTS OF CONTACT: For additional information contact Ms. Trudy Estes (601-634-2125,

), or the manager of the Dredging Operations and

Environmental Research Program, Dr. Robert M. Engler (601-634-6324, Robert.M.

). This technical note should be cited as follows:

Estes, T. J., Waugh, J., Schwartz, R. L., Green, G., Buhr, V., Braddock, B., and

Detzner, H.-D. (2004). "Mechanical dewatering of navigation sediments:

Equipment, bench-scale testing, and fact sheets," DOER Technical Notes

Collection (ERDC TN DOER-T7), U.S. Army Engineer Research and

Development Center, Vicksburg, MS.