What to do with Dredged Materials? Topic of Environmental Council Meeting
The TMACOG Environmental Planning department brought together the various agencies and departments most concerned with dredging the Maumee River shipping channel for a close look at the subject at a meeting September 25.
The need for dredging is not in dispute. Joe Cappel, director of cargo development at the Toledo-Lucas County Port Authority, outlined the situation. The western basin of Lake Erie and the Maumee River are shallow. If left to nature, the large amounts of sediment flow down the Maumee River would clog the mouth of the river. The question is what to do with the sediment that is dug out and moved. With recent attention to harmful algal blooms, scientists want to know what role dredged materials have in contributing to phosphorus in the lake. It’s clear that phosphorus is implicated in the growth of harmful algal blooms.
Much of the dredged material is currently shipped a few miles out and dropped into Lake Erie, a practice called open lake placement. Some sediment is confined in artificial islands. For many years environmentalists and others have recommended that the U.S. Army Corps of Engineers (USACE), which is responsible for dredging, pursue beneficial uses for the dredged materials rather than open lake disposal. See the TMACOG resolution here.
|Facts About Dredging:
|• Each year, more than 700 vessels call at the Port of Toledo
• Each year, 12 million tons of cargo move through the port
• The federal navigation channel is more than 25 miles long
• Dredging maintains a depth of 27 feet, a couple feet deeper than the average depth of the western Lake Erie basin.
• An average of 800,000 cubic yards of material is dredged out of the channel every year.
• This is by far the largest amount of dredging required by ports in the Great Lakes system.
At the September meeting, Mike Pniewski of the Corps announced the results of a report studying the potential for placement of Toledo Harbor dredged material in the western Lake Erie basin to influence harmful algal blooms. The complete USACE report is here. Pniewski presented a summary of the findings:
• Most dredged materials stay in a mass; less than 5% of dredged materials are dispersed to the water column
• Dredged sediment and associated phosphorus at the placement area re-suspend and deposit at the same rate as other lake bottom areas
• No difference in algal biomass was found at the placement area when disposal areas and other areas were compared
John Hull, chair of Hull & Associates, responded to the USACE report and described some potential uses of dredged sediment. While not disputing the findings of the USACE report, he noted that additional data would be needed to confirm the results. He pointed out that the study was limited in the number of samples, and that it did not look at the effect of storms or other lake conditions as recommended by the Ohio EPA, and that the areas studied might not be representative of the Lake Erie conditions. He asked the question, why, if we are digging out the sediment anyway, and we know that it has phosphorus in it, we do not remove it from the system and do something else with it? Some viable options for using dredged materials include raising the elevation of agricultural fields which would improve drainage and productivity; improve lake side parks; and restore wetland areas. The effectiveness and cost of all options needs to be studied. Hull concluded that we are on the right track with active involvement of governments, local business leaders, and academic research. He added that the role of government is to provide funding and support for programs designed by the concerned parties.