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Dredging

Dredging is being undertaken throughout the Indiana Harbor and Canal to establish the navigation depths and widths authorized by H. Doc. 1113, 60th Cong., 2d Sess., taken from the River and Harbor Acts of 1910. Dredging is also being completed in the adjacent berthing areas outside of the authorized channel limits at non-Federal expense to provide depths commensurate with those in the Federal channel.

 Dredging areas (red) and CDF (yellow)
Dredging areas (red) and CDF (yellow)

The Indiana Harbor and Canal had not previously been dredged since 1972 due to a lack of suitable storage area for the contaminated sediments. The accumulated sediment backlog in the IHC will be dredged over an 8 to 10 year period and will produce an estimated 1.6 million cubic yards of dredged materials. These sediments currently cause pollution of Lake Michigan and affect the efficiency of deep draft commercial navigation. After backlog dredging is complete, maintenance dredging will take place, as necessary, over a period of approximately 20 years, to remove reaccumulated sediments and maintain navigable depths in the harbor and canal.

Dredging is being performed using a closed bucket mechanical dredge. The dredged material is loaded onto barges or scows and then moved to the disposal area. Next, dredged material is mixed with water (slurried) that is obtained from the CDF, to make a mud-mixture. This slurry is then pumped into the CDF and allowed to settle. As the sediment settles to the bottom, clean water remains at the surface, which can then be recycled for additional sediment placement.

Monitoring data is available at http://indianaharbor.evs.anl.gov/Home.aspx.

 

Mechanical dredging with clamshell bucket.    Dredging diagram
 Mechanical dredging with clamshell bucket.