Field operation

harp screen to enhance processing of clayey material and reduce plugging due to

wet material.

Field operation

The generator and water pump performed well, and similar equipment should

be readily available at most locations. The flexible hoses were not designed to

operate at the optimum delivery pressure, however. Several failures of the

coupling/hose attachment occurred, but once this problem was addressed, the

hoses performed reasonably well with the pump discharge throttled back

somewhat. Based on this experience, however, it is thought that suitable hoses

should be purchased for future operations. The eductor pump, although

somewhat crudely assembled for the purposes of demonstration, performed fairly

effectively. Although the site was heavily vegetated, the vegetation did not

prevent excavation of the sediment in situ. Some variability was noted in the

feed percent solids. Although this does not appear to have adversely affected the

separation achieved, the result is an inefficient utilization of available water

supply; and under different circumstances, separation efficiency could be

affected. The pump did plug with large woody debris on two or three occasions.

This could be prevented with a coarse protective screen at the pump intake.

Additionally, no water jets faced in the downward direction. Excavation was

impeded when a large rock was encountered underneath the pump. The sump

and cyclone performed as expected. There was one failure of a band coupling,

and this is potentially a weak point in the system. This connection could be

made more secure with permanent piping, rather than the flexible hoses used to

deliver the slurry pump discharge to the hydrocyclone inlet.

The Powerscreen performed relatively well considering that the material

being fed was much wetter than the equipment is designed to handle. Problems

were encountered, however, in feeding the screen. Clay clods rolled off the

grizzly, reporting with the oversize. Attempts to push this material through the

grizzly were only partially successful and time-consuming. The shaking screen

passed the moist, fine materials without any evident problem, but blinding did

occur on the coarse upper screen, where 0.1- to 0.15-m (4- to 6-in.) chunks of

asphalt collected and had to be manually scraped off. Although the results

indicate that the Powerscreen may be useful to prepare a small amount of

material for process testing, feeding a full-scale hydrocyclone operation in this

manner is probably infeasible.

Visitors

The demonstration was scheduled for 10 August 2000. Notice of the

demonstration was posted on the Detroit District Web site, and notification sent

directly to regulators and environmental organizations in the region.

Approximately 30 people attended the demonstration. Results of the

demonstration were also presented to the Great Lakes Commission in October

2000.

Chapter 2 Project Description