Crews using thermal system to remediate former post office site contaminationThe Telegraph, Alton, Ill. — Linda N. Weller The Telegraph, Alton, Ill.
Feb. 14--ALTON -- Obscured by black cloth sheeting on chain-link fencing, crews are in their second week of dropping long, thin cylinders into the former post office grounds to heat, then extract contaminants.
"We are installing an in-situ thermal (desorption/ISTD) remediation system, it removes contamination from the subsurface, via extraction of liquids and vapors," said Dave Palmer, Ameren Illinois project manager for manufactured gas plant remediation. "We heat the soil to a temperature above the boiling point of the chemicals underground, and as the heat increases, they become more mobile or turn to steam and heat."
The extraction system pulls the contaminated ground water and vapors from the subsurface into a treatment container, he said. The vaporized contaminants from the vapor extraction wells will go into containers for proper disposal.
"We capture everything and contain it," Palmer said. "Any water will run through granulated carbon and we will put it in drums. A thermal oxidizer will combust any residual (contaminant) vapors as they come out."
Ameren Illinois never has used the process to remove contaminants from a remediation site, with the entire process likely to last 2 to 2.5 years.
"This is our first time in the entire territory to use this," said Brian Bretsch, Ameren communications executive regarding the ISTD process. "In 43,700 square miles, it is our first cleanup using this. Alton is the first."
Ameren all along worked with the Illinois Environmental Protection Agency in formulating the remediation plan, and needed special approval to use the "pilot system," Palmer said. The IEPA will issue a "No Further Remediation" document when the site is cleaned to its requirements.
Ameren Illinois (d/b/a Ameren CIPS) has owned the property, 727 Belle St., since 2003 and was leasing it to the U.S. Postal Service. The utility declined to renew the post office's lease that expired in 2016 in order to clean coal and tar residue in the soil and groundwater left by former manufactured gas plants that had occupied the property. The utility plans to sell the land, once clean.
Tuesday morning, a man finished wrapping the chain-link fence surface with the cloth sheeting, ending along Piasa Street. To the west, a portion of the Belle Street sidewalk was closed to accommodate an addition of a fresh, wet cement ingress-egress to the southern end of the site. "No Trespassing" signs are posted at various points on the fence.
What is going in behind the black cloth "veil" is a crew from manufacturer Terra Therm of Gardner, Massachusetts, and others, drilling and dropping in the first of about 90 wells and thermal remediation heater cylinders 4- to 6 inches in diameter. The cylinders contain thermal conductive heating elements.
The cylinders first went in on the northwest corner of the site, with the crews now continuing to add the thermal system from the north property line southward to about where the north side of the former post office building was located.
The cylinders go deep to bedrock, down 14 to 36 feet. For the units already in place, their top ends appear to have popped up from the ground.
"They will all manifold into the treatment system components," Palmer said.
Palmer said this first phase of the cleanup is scheduled for eight months, if the process goes as planned. "We might expand the system before the eight months are up, we could extend it to 1 to 1.5 years. We are hoping it overlaps. The second phase would be more of the same," depending on how much more cleanup is necessary.
Ameren selected this remediation method, which Shell Oil Co. developed in the 1980s, for efficiency, instead of simply digging up, removing and replacing the dirt on the property.
"We looked at a lot of alternatives, our goal is to not disrupt the local community and surrounding small businesses," Palmer said. "This eliminates the dump truck traffic in Alton." Ameren also would have been forced to purchase adjoining land if it would have opted to dig up the site.
He said city officials were concerned that an excavation could damage the combined, sanitary-storm Piasa Sewer, an arched limestone culvert 20 to 23 feet under the central portion of the site dating to the 1840s. "Our goal is to make sure it stays functioning," Palmer said.
With the project having an unknown length of time, and other factors, Palmer said he could not estimate what the cleanup will cost.
The former, 19,604-square-foot post office building on the site was built in 1966-67 and closed May 27, 2016. Demolition began Dec. 23, 2016 and continued for a couple weeks.
The work that began last week follows months of on-and-off drilling for samples of groundwater at the 1.47-acre site, beginning in 2016 -- first in the out yard, then on the footprint of the building once it was gone. Another round of drilling that URS Corp. performed went deeper than preliminary probing, at one point hitting an old gas holder.
Testing lasted for months at a laboratory while owner Ameren Illinois and engineers formulated the remediation plan, working with the IEPA. Palmer said tests revealed presence of coal and tar residues, mostly liquids, but no "surprise" substances requiring remediation.
"We have a good delineation of the impact on the property," Palmer said of the contaminants.
According to the IEPA website, there were several previous environmental testings at the site, in 1986, 1990, two in 2005, 2006, 2008 and 2011.
The residues were released, and seeped deep into the ground from cylindrical gasholders storing manufactured gas from a series of companies that occupied the site. In the 1800s, Chicago and Mississippi Railroad Co., had owned the property, and sold it to Alton Gas & Electric, which built the first gas plant there in 1855. Alton Gas Co., then, purchased the plant in 1926, selling it to Union Electric Co., in 1937. Bretsch said previously that the company ceased manufacturing the gas in 1941.
The plant manufactured gas from coal and oil for heating, cooking and lighting, including for street lights. The process to manufacture gas involved heating coal in the absence of air, as opposed to burning. The gas was stored on site in large, cylindrical tanks called gasholders, before the company distributed it to customers. Coal tars, coke and ash were residues resulting from the process, with the company selling the first two substances for other uses.
"Between 1941 and 1949, the gas plant buildings, relief holder and equipment were demolished and converted for use as the Union Electric Service Center," Bretsch said previously. "Sometime between 1949 and 1965, the distribution holder was demolished. The Union Electric Co. sold the property in 1965" to an Ameren predecessor company. Then, Bretsch said that company signed a 50-year lease with the Postal Service on June 13, 1966.
Reach Linda N. Weller at 618-208-6450 or on Twitter @Linda_Weller
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