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HILLSVILLE — Workers scurry over 13.6 acres of mounded earth on this bright Tuesday at the Twin County landfill, bent on various tasks to seal off the waste and prevent 23 years of accumulated garbage from leaking and causing pollution hazards.
In a maneuver not unlike covering the turf in a baseball stadium during a rain delay, five of 14 workers grab the end and sides of a roll of 22-foot-wide white plastic sheeting and pull briskly to cover a swath of this approximately 50-foot-high hill of garbage and dirt.
Workers depend on the arm of an excavator to hold up the roll of this first layer of three geotechnical fabrics to go down.
This is necessary because the roll of liner weighs 3,500 pounds.
The mound spreads over an area larger than athletic fields, so perhaps a better parallel for the more than $1.5 million landfill closure project is installing wall-to-wall carpet.
Crews excavated a line of dirt that buried the edge of the closing of the first half of the landfill in 2001.
Around the man-made hill stand 15 metal pipes that act as methane vents to let escape the gases that arise from the decomposition of many tons of trash.
A rotten eggs smell is strongest near the vents before the breezes dissipate it.
Sunlight shines off the white material of the first barrier layer, reflecting into eyes and making a glare for a time, before the second black layer of linear low-density polyethylene goes down on top of it.
The trade name for the white material refers to it as the Bento liner, which features a filler of malleable material that would move to reseal in case any of it were punctured.
Using this fabric replaces having to truck in load after load of clay instead, saving time, work and money, landfill manager Allen Lawson said.
Other rolls of a third material — reminiscent of felt on the outside, with a kind of mesh on the inside — will serve as the outermost layer of the landfill cap seal.
This liner will catch rain that falls onto the two feet of dirt that will top the geotechnical fabrics.
Water will run off down the slope and into a trench built to catch and direct it to a holding pond nearby. This rainwater is clean and does not need treatment.
“The liner seals to keep water out,” Lawson explained. “Essentially, when we get done with this project the trash will be closed in a big plastic bag.”
Any liquids that gather inside the closed landfill cell will get collected and pumped out to Hillsville’s wastewater treatment plant to be processed.
At the join where fabric pieces overlap, a self-propelled machine creeps along to seam the edges together.
Travis Brown, a field inspector for the engineering firm of Draper Aden, pointed out that the machine leaves a double seam behind in its tracks — one that needs to be both water- and air-tight.
Requirements for landfills state that a worker has to take a sample of the seam once every 500 feet.
They cut out a swath big enough to divide into threes — one piece for onsite testing, one for shipping to an independent lab for testing and one to go into a vault as an “archive” of the sample, Brown explained.
The seaming process creates little pockets in these overlaps. One of the tests involves pumping the pockets full of air to 28 pounds of pressure per square inch.
Testers monitor the pressure and if it drops to under 26 pounds of pressure, the sealing has failed.
Other tests involve attempts to pull apart and to cause the fabric to shear, Brown said. The goal is for the “welds” to hold even under conditions that would cause the materials to give way.
When the new covering reaches the edge of the old cell, the geotechnical fabrics over the two will be sealed together.
Grasses with shallow roots will be sown on top of the dirt over the liner — nothing that will grow down long enough and get into the landfill barrier, Lawson said. That means no trees or shrubs will be allowed to grow there, because their roots do go too deep.
Before completion of the landfill cap around January, workers will have to fill in around 65,000 cubic yards of dirt for the project.
The dirt needs to be free of rocks, so there are no sharp edges to puncture the seal.
Materials alone for this effort cost $800,000, the landfill manager said.
These are elements that make landfill closures complex tasks, said Lawson and Brown.
The capped landfill will have to undergo 30 years of monitoring gas and water at the site by law.
Today, the landfill dumps garbage in one of five new cells, which have an undetermined lifespan, Lawson said. He sees those buried piles probably rising another 40 or so feet before they’re closed and capped.
In the meantime, the landfill’s day-to-day operations continue with one employees assigned to different mitigation efforts, like picking up stray trash and mowing and weed eating to maintain a good appearance.
The staff also uses shredded tires from New River Tire Recycling for daily cover to replace having to spread dirt all the time.
It’s also a way to dispose of tires safely, Lawson said. The landfill takes advantage of a state grant to pay the expenses for that.
It helps with the appearance of the landfill that an equipment operator smooths over the trash dumped daily with a layer of earth.
Two Department of Environmental Quality inspectors recently noticed the state of the landfill and praised the authority.
“They said it was one of the cleanest and neatest kept landfills in the state,” Lawson recalled.
Bidder questions selection process
Officials with the regional landfill authority that serves the City of Galax and Carroll and Grayson counties bid this project earlier in 2013, and selected Sowers Construction to do the work.
The project probably would have proceeded without any notice from the general public, except that one of the construction companies that bid on the work objected to the landfill authority’s selection of another contractor.
“We would like to express our disappointment with the board’s decision to award this project to another contractor whose bid surpassed our low bid by over $200,000,” said a June 25 letter from Jimmy R. Lynch and Sons Inc., written by Daniel Lynch to the landfill officials and shared with The Gazette. “Simply put, the taxpayers of Carroll County, in these tough economic times, are being submitted to unnecessary spending due to insufficient post-bid investigation.”
The letter specified that in terms of landfill closure experience, Jimmy R. Lynch & Sons, would have used subcontractors Hallaton for the gas vent installations and American Environmental Group for installing liners.
Combined with the 40 years of grading, earthwork and utility work, Daniel Lynch believed that their company would have been able to handle the closure and for less money.
“We feel that all aspects of the work involved in this project would be completed by contractors who have an acceptable level of work in their respective fields,” the letter said.
But Draper Aden, the designing firm for the closure project, did not recommend Lynch’s company because it hadn’t been involved in landfill closures before.
In awarding the work on June 21, regional landfill officials noted in a letter that bid documents sought contractors that “have experience with the construction of landfill closures and [are] familiar with the particular requirements of this project.”
The landfill required a “contractor’s qualification statement” along with the bids to evaluate the contractor’s experience.”
“In reviewing the qualification statement submitted by Lynch & Sons, no experience with landfill closures was provided,” the landfill’s June 21 letter said. “The one project listed on the qualification statement generally relating to landfill work was of relatively small scope and was conducted in 1999.
“Importantly, this project did not constitute a landfill closure.”