Green Bay Recycles Dredged Material
The Corps of Engineers Detroit District has begun using the first of a new generation of confined disposal facilities at the Port of Green Bay Wisconsin.
The Bay Port Dredged Material Disposal Facility is designed to de-water maintenance material from the Green Bay navigation channel and recreate usable topsoil. It is the result of five years of effort by the Brown County Harbor Commission.
Roen Salvage has the $1.5 million dredging contract for maintenance of the Green Bay shipping channels, and is placing the material into two cells of the new facility.
The Corps annually dredges 150,000 to 200,000 cubic yards of sediment from the 18-mile-long Green Bay shipping channel, which collects runoff from the Fox River drainage basin. In 1994, the State of Wisconsin had notified the port that the existing confined disposal facility (CDF) would have to be engineered to match current solid waste landfill regulations. The Port had filled two 400-acre confined disposal facilities over the past 30 years, and Brown County began looking for a better way to handle the material. Since the sediments are primarily topsoil, the commissioners decided to find a way to get this soil back to the land. An inexpensive method had to be developed to remove the approximately 70 percent water content from the material, which is excavated using clamshell dredges. Once dewatered and compacted, the dredged soil occupies 1/3 the volume of the original amount dredged.
The county hired Robert E. Lee & Associates, a local environmental engineering firm, to develop a suitable method for accomplishing this. Michael Dovichi, a professional geologist with 25 years experience in solid waste management, is the project manager.
Landfill approval in Wisconsin is a three-stage process that takes a minimum of 10 years to negotiate. Robert E. Lee & Associates modified one step and eliminated a second step, receiving licensing of the facility in only two years. The Wisconsin Department of Natural Resources was one of the first partners in the Port’s efforts to approve the new landfill.
The 100-acre facility has a 2.5 million cubic yard capacity, and is designed to never be filled. As the material is dried, it will be removed for re-use. There are five de-watering cells that vary in size from 10 to 23 acres. Dump trucks haul the sediment to the facility from barges at a nearby dock and deposit the material into the cells, which are sloped to the northeast corner, where a de-watering structure is in place. Material from the 1998 dredging project has filled Cell 5, and part of Cell 6 (see drawing on page 7.)
The drainage structure consists of a layer of granular material in which six-inch-diameter perforated PVC piping is installed. The granular drainage blanket removes water draining through the sediment at the low end of each cell. Drainage from the cells will be carried through grassed waterways to a series of ponds for additional settling, and eventually discharged to the bay of Green Bay.
Dredging in Green Bay takes place in late summer and fall. Weather conditions vary, but ice usually begins to form on standing water around November 15. The material will be left until next summer, and the freeze-thaw activity in the winter will help separate water from the sediment. The underdrain system will continue to operate during the winter.
Unless there is a need to drain pockets of water on the surface, nothing will be done to the sediment for a year after it is placed in the cell. An adjacent cell will be used the second year, and a third one the following year. By the fourth year, the material in the first cell will have dewatered to 20 to 30 percent moisture without any mechanical treatment or physical processing. At this point, the sediment resembles silty topsoil.
Before the fourth year of dredging begins, standard earthmoving equipment will be used to excavate the soil and transport it to a storage cell. There it will be placed in a pile, compacted and seeded, unless there is a use for it in the same year. Meanwhile, the original cell will be re-graded to design grades to be made available for the four-year cycle to begin again.
Roen Salvage of Sturgeon Bay, Wisconsin is dredging 234,000 cubic yards using their Derrick #3 with a Manitowoc 4000 crane and an eight cubic yard Cable Arm bucket, which they purchased specifically for this job. Dredging began on September 1. They are loading onto three 160 x 40 foot deck barges moved by the tug Stephen Asher, and using a four cubic yard Cable Arm to unload into the dump trucks. The longest trip to the dock is a mile and a half, from the end of the 7000-foot-long channel.
Because of a considerable overrun in material, this project will be completed in the spring. The job was shut down for the winter at the end of November.
Tom Levy is project manager for Roen Salvage. Reliance Construction of DePere, Wisconsin is the trucking subcontractor.
This is the first project to be funded through Section 217 of the 1996 Water Resources Development Act (PL 104-30.) This section allows the Corps to use private or public landfills for disposal of sediment, paying a tipping fee to the owner, in this case, Brown County, Wisconsin.
The final funding agreement for this project, which had a total cost of $3 million, is still pending. The site was planned and built using funds from Brown County, the State of Wisconsin, and the U.S. Environmental Protection Agency. The level of payback on the federal portion will be determined after a final review by Corps of Engineers headquarters. The Detroit District has included this project in the modification of their Dredged Material Management Plan (DMMP,) which was submitted to the Corps Lakes and Rivers Division on June 6, and was scheduled to reach Washington in the middle of November. The DMMP is a decision document that demonstrates that this project is right for this area, and is included with the request for funding under Section 217 of WRDA 1996.
The modification of the DMMP includes reducing the 11-mile outer channel from a two-way width to a one-way width. This means that the historic maintenance dredging numbers are reduced and cannot be used to project future volumes. With the new volume projections, the Bay Port facility would have a 20 to 30-year capacity if none of the material is ever recycled, and an indefinite life if re-use of the material proceeds as hoped by Brown County, said Joe Mantey at the Detroit District. Though the material meets federal standards for levels of PCB’s, it does not meet current State of Wisconsin standards for certain uses, and so the plan to use the material as topsoil has not been approved. Landscapers in the area have said they could use most of the material, if it is approved, said Dovichi.
The Brown County commissioners intend for this project to be a valid prototype for the Section 217 program, and have taken pains to be sure that all legitimate costs have been included in the report submitted to the Corps of Engineers, Dovichi stated.