New Environmental Restoration Technique Tested in Ohio december 1999
Working from a barge in the Ottawa River in Toledo, Ohio, the operator of a Putzmeister Telebelt® TB 105 uses remote radio controls to move the belt from side to side to assure even placement of sediment-sealing AquaBlok™ in the water.
Operating from the shore of the Ottawa River in Toledo, Ohio, a Putzmeister Telebelt® TB 105 uses the full extent of its 105-foot (32 m) horizontal reach to place a special compound in the water that seals the contaminated sediment on the bottom of the river to prevent further spread.
An excavator keeps the hopper of the Putzmeister Telebelt® TB 105 filled with AquaBlok™ as it operates from a barge in the Ottawa River in Toledo, Ohio. The Telebelt placed 360 tons of the material in the river at a targeted thickness of 2 inches (5 cm). AquaBlok™ seals contaminants in the sediment in the river bottom. Putzmeister Telebelt® places 470 tons of material in Ottawa River
The Lake Erie Basin has been home to heavy industry for more than 100 years, and the Ottawa River in Toledo, Ohio, has suffered from the effects of industrial waste deposited in the waterway.
While companies have minimized pollution discharges to the river, contaminants still remain in the riverbed sediment, posing a hazard to fish and humans. For more than a decade, fishing, swimming and other recreational activities have been prohibited in certain portions of the river.
After studying the situation, the city of Toledo, in conjunction with Hull & Associates, Inc. and the University of Toledo, in September 1999 tested a relatively new method of encapsulating contaminated sediments by covering and sealing the river bottom with AquaBlok™. This is an inert, bio-friendly compound made up of clay, stone and biodegradable polymers.
Once placed in the water, AquaBlok settles to the bottom of the riverbed, absorbs water, physically expands and bonds together to create a barrier and an erosion-resistant cover over the contaminated sediments.
Hull & Associates, project engineers and the city’s lead consultant on the project, brought Geo. Gradel Company into the project during the planning stages about two years ago because one of the company’s divisions specializes in marine contracting.
Fred Sander, Gradel’s vice president, said it was during the planning sessions that the application method was decided upon. “We tested the material to see how much it swelled in water,” he said, “and we were amazed. This was our first time using AquaBlok, and I’m sure it won’t be the last.”
Geo. Gradel Company supplied the barges, a tugboat and the equipment needed to move the material to a Putzmeister Telebelt®, a truck-mounted telescoping conveyor used to place almost 360 tons (326,586 kg) of AquaBlok in the river.
Another partner in the project, Hite Concrete Pumping Services, operated the Telebelt TB 105 to place approximately 2 inches (5 cm) of AquaBlok — which would expand to a 5- to 6-inch (13 cm to 15 cm) layer.
About 25 truckloads of AquaBlok were delivered to the site and placed in a large, shovel-based rockbox for subsequent delivery to the Telebelt hopper. The Telebelt was operated both from shore as well as from a barge in the river. Because several sediment cap designs are being tested, an additional 113 tons (102,512 kg) of stone were also applied with the Telebelt (over the top of the AquaBlok) in a similar fashion.
Placed About 80 Tons a Day The test site is a 2.5-acre (1 hectare) area of the river about 6 miles (10 km) from the river’s mouth on Lake Erie which was known to have some of the highest concentration of PCBs and heavy metals in the Lake Erie Basin.
“It took several days to do the job,” said Dick Hite, president of the concrete pumping services company. “We could have done it faster, but it was necessary for the engineers to measure and monitor the amount and combination of material before it went into the water to obtain the exact coverage they needed. We averaged about 80 tons a day.
“Before we started, we did a test pour on land,” he said. “We had to play with the controls a bit to regulate the flow to get the thickness coverage required,” Hite said. “When the engineers were satisfied, we went to work.”
“We found that with a Telebelt and an experienced operator the uniformity of the application was quite impressive,” said John Hull, president of Hull & Associates, Inc.
Second Time AquaBlok Use This is the second time AquaBlok was used. The first was in 1994 at a Superfund toxic site in Alaska. At that time, the Army Corps of Engineers spread the material from a helicopter.
As the city’s consultants, Hull & Associates, Inc. provided a demonstration of material delivery from a helicopter as well as from the TB 105. Hite said, “I don’t want to say the TB 105 competed with a helicopter for the job, but for the kind of work they needed done, the Telebelt offered the best solution at this site.”
Hull agreed, “The delivery method really depends on the situation. In this case, the Telebelt provided the kind of precise placement required.”
Couldn’t Run at Top Speed Hite said he couldn’t run the TB 105 at its maximum belt speed of 360 cubic yards (275 m3) per hour because of the need for a uniform application. “We had to regulate the belt speed to the boom movement using the radio remote-control box.” Operators did, however, use almost every inch of the machine’s 105-foot (32 m) reach. Hite added, “They would give us the coordinates and square-off an area with buoys or wooden markers. When everything was ready, we would go in and place the material.”
“We used the barges because one side of the river contained sodded reclaimed landfill and the other was an environmentally reclaimed area,” said Sander. “We couldn’t tear up the ground surface with heavy equipment.”
While Hite had no problem working from the barge, he worried about the precision required in the placement of the AquaBlok. “My one concern was the shape of the material. It was between 1 and 2 inches (2.5 and 5 cm) in diameter and round. I thought it might roll down the belt,” said Hite. “Fortunately, it held fast, and we maintained the accuracy needed.”
Saw Ad in Magazine How did an engineering consulting firm hear about a Putzmeister Telebelt? Hull’s staff saw an advertisement in a trade publication. When they wrote for more information, their name was given to Hite — who sells Putzmeister equipment in the Toledo area.
Hite thought they wanted to buy one, so he demonstrated a unit. A year later, they called and explained the project. “They were involved in a lot of planning and had to get approvals from a number of agencies, such as the Army Corps of Engineers, before operations could begin,” Hite said.
The job was completed the end of September. And while the material placement was successful, Hull & Associates, Inc. and the Department of Civil Engineering from the University of Toledo will continue to monitor the application to determine how it is affected by varying river currents, scour patterns and sediment thickness.
The project was funded in part by a $191,000 grant from the Ohio Lake Erie Protection Fund, and a portion of Hull’s services was donated to the city.
Consulting Engineers: Hull & Associates, Inc., Toledo, Ohio Marine Contractor: Geo. Gradel Company, Toledo, Ohio Pumping Company: Hite Concrete Pumping Services, Neapolis, Ohio