Dredging_Initiative_Questions.docx

1. How are the CDFs operating now and what do you do with the material?

USACE follows the Inland Testing Manual or the Great Lakes Testing Manual (a regional version of the Inland Testing Manual) when evaluating sediment. Using a tiered approach, the chemical and biological quality of the material and any potential impacts associated with the placement/use of that material are evaluated. CDFs are used to confine the most contaminated materials, which are unsuitable for open water placement, beach nourishment or other beneficial uses. USACE operates a number of CDFs around the Great Lakes, which vary in size and operational details. USACE also has a few “SMFs” or “sediment management facilities” which hold clean materials that are dewatered and staged for re-use. The Erie Pier facility in Duluth, MN is used for sediment management of clean sands.

2. What form is the waste material in and does the waste material contain contaminants?

Sediment is a granular solid material, saturated with water when removed from the lake or river, Sediment in the Great Lakes varies widely in physical and chemical characteristics, ranging from coarse and clean sands (used for beach nourishment) to fine, silty and heavily contaminated sediments at industrial harbors (placed in CDFs for storage). Clean sediment is not ‘waste’ per se, but is a valuable, re-usable commodity. Regardless of the physical properties (coarse or fine) and the level of contamination, sediment can be dredged using either mechanical or hydraulic methods. Mechanical dredging involves using a crane with a clamshell bucket to scoop the material out and place it in a barge for transport; the material is off-loaded either by dumping or by using another crane. Hydraulic dredging involves pumping the material as a slurry, with the sediment/water mixture flowing through a pipeline either to a barge for transport, or more typically to the final placement site. The determination between the dredging methods is typically based on cost and equipment availability.

3. After the dredging process how do you transport the material to the CDFs and what process do you use on the material?

Sediment is transported to CDFs by barge or pipeline typically, directly moved from the dredging location to the CDF. It is possible to use trucks also, however these operations tend to be messy (wet sediment drips out of the trucks) and less efficient (trucks are smaller than barges and move less material per trip). Once the sediment is placed in the CDF, it is dewatered passively. Material is allowed to settle and the free water is decanted off. Once the free water has been removed, sediment is worked and compacted to further dry it and to maximize the capacity of the CDF. Typical earthmoving equipment is often used for sediment management and compaction activities.

4. Is there any vegetative wood biomass pulled from the river?

All dredging operations encounter some amount of debris, including wood, stones, and various manmade objects that fall or are dumped into the river or lake. There is typically not a large mass of wood or vegetative material in industrial harbors. Debris is typically placed in the CDF with the sediment, or for dredging operations that involve beach placement the debris would be disposed of as garbage.

5. Are there analytical reports on the material and what elements are contained within?

There is no general, annual testing done at CDFs or even at individual harbors. Rather, the testing done is dependent on the dredging frequency, the conditions in the sediment, the placement location, and any permit or other requirements particular to that location. Information on a specific harbor, river, or CDF could be obtained through a FOIA request to the district office; the district offices (Buffalo, Detroit, Chicago) keep records related to sediment management and sediment quality.