New landfill cell nearly done
A new landfill cell nearing completion at the regional waste agency south of Fort Dodge will provide needed space as the current cells reach capacity. It will also enable a new method of encouraging decomposition in the waste.
Construction on the major project at the North Central Iowa Regional Solid Waste Agency should be finished in about two weeks, according to Doug Luzbetak, of HLW Engineering group, who has been the engineer of record for the project. The cell could be ready to take in garbage in as little as three weeks, pending an inspection and approval by the Iowa Department of Natural Resources.
The cell is a lined depression about 40 feet deep at its maximum depth, but waste will eventually fill the cell much deeper than that, Luzbetak said. The cell covers about 3.6 acres. and should last for about 10 years.
The cell is one of several projects going on at the agency, said Interim Agency Director Cindy Turkle.
When it was bid in September 2013, the project cost was $1.2 million, Turkle said, but that also included construction of a new system for collecting and removing the water that trickles down through the solid waste.
This liquid, called leachate, must be collected and treated, and not allowed to seep into the ground under Iowa DNR regulations. A new lift station and force main was installed in November 2013 to collect the liquid from the landfill’s two active cells, Turkle said.
Failure to handle leachate properly was one of several alleged environmental violations found last year under previous landfill staff that have led to potential legal action from the Iowa attorney general’s office which may result in a fine.
The new cell is tucked between those two currently operating cells, said NCIRSWA Board Chairman Mark Campbell said. Both are becoming full, leading to a need for more space.
The southeast cell is used during dry weather, Turkle said, while the cell to the north, built in 2002, is used when it’s wet, due to the land around the cells.
“This is the state of the art,” said Turkle of the new construction. “This is what they call a Subtitle D composite lined landfill cell.”
Several layers go into the bottom of the cell to create a tight, leakproof basin.
“We excavated down until we found real good firm virgin dirt. Then they put in a fabric with a geotextile in it,” Turkle said. “Then there is 2 foot of compacted clay as an impervious natural layer.”
On top of the impervious clay, which is tested in multiple places, is a layer of high-density polyethylene liner. Seams in the HDPE are sealed by a special machine which creates two seals instead of one, with an air pocket in between. This makes it easy to test the seal for leaks by pressurizing the air pocket.
A layer of sand will go on top of the plastic, and moisture that trickles down through the garbage will flow down to the center and be collected by a pipe.
“We’re basically building a bathtub, with a drain in the end,” Turkle said.
This style has been in use since the 1990s, Luzbetak said, but was not required by law until 2007.
Cells were previously built with only clay or ground tires as liners, under previous DNR regulations.
With the new composite lined cell the landfill will be able to recirculate the leachate by spraying it on top of the garbage. State law prevents this on the old cells.
“When we get enough waste on here, we’ll be able to recirculate,” she said. “What it does for a landfill like this is it will help compact it tight, so we can get better compaction. When garbage is dry, it doesn’t compact as well as if it’s a little moist.
“The other thing it will do is, a lot of the garbage that comes in is organic materials. Potato peels, coffee grounds, even paper and stuff like that. When you put some water with it, the good organisms will break it down and stabilize it.”
Leachate will still have to be pumped out, but recirculation can decrease the amount, because some of it evaporates during the spraying, Luzbetak said.
This is just one of a number of changes going on at the landfill, Turkle said.
“We have made so many good changes here, people should be proud,” she said. “The staff has been wonderful bringing this up to regulations.”
“I’m out here every day looking at the progress,” Campbell said. “It’s so good to see what people thought was just a dump is now really becoming a landfill where we separate garbage, construction products are recycled if possible, and we have the recycling center.
“With single-stream recycling, that’s going to decrease the amount that goes in here, and we really want to see that expanded to the smaller communities if possible.”
Fort Dodge began single-stream recycling in February, enabling residents to use curbside recycling without sorting the items first.
A modern landfill is a complicated operation, not just a hole in which to throw trash, Campbell said.
The garbage must be covered every day by a layer of dirt or an alternate approved cover, Turkle said. This keeps away birds and other vermin.
Proper handling also means the landfill is cleaner than some might expect.
“There’s no smell,” Campbell said, standing in the new cell. “We’re right in the middle of the landfill. Do you smell anything? We’re right between the two areas that are in use.”