Mild temps allow workers to finish containment pit so dredging can begin next week
BY CHUCK VANDENBERG
FORT MADISON - You can see the work - but you really can't see the work.
Ten-foot berms block the view of passersby along Fort Madison's riverfront. The occasional earth mover crawls over the berms, but the real work is taking place on the other side of the hills.
Fort Madison Public Works Director Mark Bousselot said the city has been building a containment area for dredging material that will be pumped out of the marina as early as next week.
The $11 million marina renovation project is quickly getting to the point where winter temperatures and a separation of river water from silt will be under way sooner than expected.
While the separation takes place in the containment pits, crews will finish working on the jetty wall that is being extended into the river, eventually being the foundation for a walking path that ends looking into the river.
"What we're doing here basically east of the Memorial is building a containment for the dredge material coming out of the marina," Bousselot said.
"The water and sediment are going to come in through a hydraulic pump off the dredger and then through some piping. The water will drain out back into the river."
The sediment won't be enough to fill the pits inside the berms, so as the sediment settles out and it becomes workable, crews will take these berms back down to the level of the sediment and regrade the park.
The remaining sediment will become the base for the new Riverview Park on the east side. The residual berms will then be used to raise the road on the north side next to the railroad tracks up to the same level as the new base of the park.
Dirt from the construction of the new highways was also brought over to the park, while some clay was brought in for the future building pad of the new hospitality center at the marina.
Dan Hicks, project manager for DeLong Construction, said the dredge pit will be completed by Monday afternoon and dredging can begin.
Four large lines of white rock were run along the base of the pit and will serve as a "french drain" under the sediment to help move water out of the pits after the sediment, or "silt" is settled into the base.
A crew supervisor on site said with the four french drains in place and the other drain pipes, it will take about a year for the silt to dry out.
Hicks said he wants to work with the city to cut the extra "surcharge", or dirt, used for the pad for the hospitality center down to a height of about five feet, which would be out of the 500-year flood plain. Then use that extra surcharge to raise the parking lot to the same height as the hospitality center, and possibly raise the rest of the park road that runs from the boat ramp east to the new jetty wall, if materials are sufficient.
"Currently under contract I have to raise this road up to a certain elevation to the parking lot," Hicks said.
"The thought is that in spring, or even this winter, we'll negotiate that into the contract and we'll just leave our equipment here."
He said the dredge pit will be complete by Friday night. Then they bring rock in as the new base for the jetty. Part of the new jetty wall has been constructed and a silt screen runs the rest of the way around the marina held up by yellow floats. Hicks said they will bring in enough rock to go another 600 feet out into the river toward the park.
Bousselot said the Army Corp of Engineers require that silt disturbed during the dredging not make its way back out into the river.
Hicks said material already on site will go on top of that initial rock for the jetty. Then the bigger rock or "rip-rap" will be brought in to work along the outside of the jetty wall until the dredging begins along the inside.
He said crews will continue to work as long as the weather holds up.
"We'll continue to work right up until Christmas and we may even work from Christmas to New Years if the dredge is running and I have a place to put rip rap, I'm gonna keep working - until I get froze out," Hicks said.
"If we get the dredge guy going, that's about four weeks so by the middle of January, provided we don't get froze out, all the dredge work should be done and we'll continue to place rip-rap until we get froze out. Then as soon as the ice goes out we'll complete the rest of the rip-rap.
Bousselot said the removal of sediment on the river side of the jetty, which is part of FEMA reimbursements, has been taken care of. The other aspect is dredging the marina six feet deeper. Hicks said the bottom of the marina is at about 518 feet above sea level now, and dredging should take it down to 512 feet giving another six feet of depth in the marina.
Then crews will continue to finish the jetty wall, which will include a walking path that triggered some funding from the Great River Health System - Fort Madison Community Hospital Community Foundation to assist the project.
The dredging will consist of a pumping operation where the water and silt will be pumped through 12" hard plastic piping that was part of the work of Superior Seawalls, Docks and Dredging out of Illinois City. The piping will be six 250-foot sections that will carry sediment and river water to the dredge pits where it will settle out for a year.
The city has committed $1.5 million to the project, and Fort Madison - Southeast Iowa Regional Riverboat Commission has committed to an equal investment. FEMA's reimbursements cover an additional $1.5 million, and the GRHS-FMCH foundation also committed $1.5 million to the project.
Fort Madison Mayor Matt Mohrfeld was able to secure funding through a federal grant program and $100,000 from Freeport McMoRan. He's also applied for state block grants and funding through the county's America Rescue Plan Act's $6.5 million pool.
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