USA: Dredging Starts at Great Lakes Area
The Indiana Harbor and Canal has not been dredged since 1972, but thanks to a truly collaborative effort, the Corps has started to safely remove and contain sediment to not only restore deep draft commercial navigation but improve water quality in southern Lake Michigan.
Over a period of eight to 10 years, the Indiana Harbor and Canal Confined Disposal Facility Project will produce an estimated 1.8 million cubic yards of dredged materials. First buckets of sediment removed from canal Oct. 23. Production dredging began Nov. 16.
With one seamless swivel of a crane, a bucket of sediment was released into a barge the afternoon of Oct. 23 for the first time in over 40 years in the Indiana Harbor and Canal, one of the busiest ports by tonnage and the number one area of contamination in the Great Lakes.
“This East Chicago waterway hasn’t been dredged since 1972, but thanks to a truly collaborative effort involving federal, state and local government, private industry and members of the local community, we have started to safely remove and contain sediment to not only restore deep draft commercial navigation but improve water quality in southern Lake Michigan,” said Chicago District Engineer Col. Frederic A. Drummond Jr.
Over a period of eight to 10 years, the Indiana Harbor and Canal Confined Disposal Facility (CDF) Project will produce an estimated 1.8 million cubic yards of dredged materials through mechanical operation of an environmental or closed clamshell bucket to securely place accumulated sediment backlog in barges where it is transported to the CDF and hydraulically off-loaded through pipes using re-circulated water from the CDF.
“By removing sediments from the canal, the migration of sediment into Lake Michigan, our largest body of fresh water, will be prevented,” said Rep. Pete Visclosky (IN-1).
It is estimated that each year, more than 100,000 cyd of contaminated sediment washes to the Lake, including approximately 67,000 pounds of chromium, 100,000 pounds of lead and 420 pounds of PCBs.
“You can see the effort and care the Corps has put into this complex project,” said East Chicago Mayor Anthony Copeland.
As the location for the CDF is an abandoned petroleum refinery site, it includes some unique features not typical of Great Lakes-area CDFs, such as a groundwater cut-off wall and a groundwater gradient collection system instead of the more typical passive liner, a sealed sheet-pile wall to complete the site isolation from the environment, oil booms in the canal to address historical discharges and an on-site wastewater treatment plant.
USACE and partners worked in close concert with the community from the project’s start and took concerns to heart to include: annually reviewing new and emerging technologies, including those proposed by the community, in the area of removal, transport, disposal and treatment of contaminated sediment; holding quarterly community information sessions; and completing an evaluation report of property value impacts expected from the project.
“We are ensuring this project will have minimal negative effects on the local community and environment, through activities such as air monitoring and treatment of all groundwater and dredged material that leaves the site,” said Chicago District Project Manager Mike Nguyen.
The sediment contains a number of compounds of various types. USACE is monitoring the air for the total number of volatile compounds and has also chosen naphthalene as the main compound for real-time air monitoring.
“Naphthalene was chosen because it is present in the sediment in fairly high concentrations, so it is more likely to be released. Also, it is not a compound known to be released from the adjacent petroleum industries, as we want to identify the potential air quality impact of the CDF as a unique source,” said Chicago District Environmental Engineer Jennifer Miller.
If any of the monitoring starts to show elevated concentrations of volatile compounds, the dredging operation will be changed or stopped until the concentrations are sufficiently low.
“We expect to release less than 1 ton per year, which is well below the facility’s permitted 25 tons of volatile emissions per year,” said Miller.
USACE has monitored background levels of PCBs and other airborne pollutants for more than 10 years. Twenty-four-hour samples of chemical parameters that fall into several chemical groups and particulate matter are collected from air sampling stations every six days, as part of long-term ambient air monitoring.
“We conducted extensive experimental measurements and modeling, and the model developed for Indiana Harbor is now used worldwide for estimating volatile releases from dredging projects,” said Miller.
After backlog dredging is complete, maintenance dredging will take place, as necessary, over a period of approximately 20 years, to remove re-accumulated sediments and maintain navigable depths in the waterway.
Source: dvidshub, December 7, 2012