NORWALK, Conn. — Contaminated soil will be carted away as part of the construction of The SoNo Collection, while other contaminated soil will remain on the site, “isolated” under the building, a Connecticut Licensed Environmental Professional (LEP) told the Norwalk Zoning Commission last week.
The difference is in the level of contamination, said Mitchell Wiest, a professional geologist. Under state regulations, soil that tests at a certain level can remain if it is isolated from water and human contact, Wiest said at the May 4 Zoning Commission public hearing on the proposed mall.
General Growth Properties (GGP) is sparing no expense in testing the soil at the “95/7” site, where West Avenue meets Interstate 95, he said. There were 80 test borings resulting in 250 soil samples from the site, which has gone through several remediation efforts over the past 10 to 20 years, Wiest said.
Parts of the site are subject to the Connecticut Transfer Act, but GGP voluntarily went through a state review of the entire property, Wiest said. A comprehensive report was delivered to the Connecticut Department of Energy and Environmental Protection (DEEP) at the end of the summer, and remediation began, according to Wiest.
“The site still has some impact, primarily oil related, through the past uses and operations of the site, also minor impacts of metals and pesticides,” Wiest said. “… We are going to excavate the impacted soils and transport most of them offsite to appropriate landfills and disposal facilities. Some soils will remain on site and those will be rendered environmentally isolated and inaccessible, in accordance with Connecticut regulations. Those soils will be placed underneath our new structures.”
Commissioner Nate Sumpter asked what type of petroleum compounds would remain on the property.
Semi-volatiles and hydro carbons, Wiest said.
Soil samples that tested at a higher concentration must be removed, but soil samples at a lower concentration can be buried under a “permanent building” because, “Basically, you can’t touch it and the water can’t get into it,” Wiest said.
Again, the soil was intensively tested, he said.
“We essentially gridded the entire site, one sample for so many square feet, and at different elevations,” Wiest said. “You can think of it as a Rubik’s Cube, of different colors. Some soil is green, and that’s good. Some soils may be yellow and that’s OK, but some soil is red and that gets to be removed to a landfill or some disposal facility somewhere else.”
Sumpter asked how the test results would be verified during construction.
“My team will be onsite fulltime during construction directing that process,” Wiest said. “… If we find something that we didn’t expect then we dig a little more.”
Attorney William Hennessy, in responding to public comments later, said that “most” soil would be removed.
Lori Kydes had asked that an independent, uninterested party check the soil samples as part of the construction process.
Wiest said that he is an independent party, as an LEP. As part of his license he has to “hold human health safety paramount,” and, “Just because a client wants it that’s not good enough. I have to hold human health first,” he said.
Commissioner Linda Kruk questioned Wiest, asking for a percentage of soil that is contaminated.
“I don’t have the actual number,” Wiest said. But in the four or five remediation efforts that were completed but not fully documented, some soils were removed and replaced with fill, he said. It’s obvious that soil on the perimeter of the site wasn’t touched, he said, describing the varieties of contamination as a “spectrum.”
Other environmental concerns
Stormwater runoff and sewage were also topics at the public hearing.
Tim Onderko of Langan Engineering said he had worked with Tighe and Bond and Norwalk’s Water Pollution Control Authority (WPCA) to monitor the area’s sewer flows for a month. The mall is expected to produce 150,000 to 180,000 gallons of sewage a day, and Norwalk’s wastewater treatment plant currently processes 12.8 million gallons a day, he said.
The Water Pollution Control Authority doesn’t “need to do any assessment until they meet 16 million a day. It’s still a pretty significant delta between what we generate and any issues at the treatment plant,” he said.
GGP will reduce storm water runoff to the area’s storm drains, he said, concluding, “The components that we have in place – with the quality treatment, the flow rate reduction and the rate reduction – we think all provide benefit to the coastal resources compared to the current condition or the former condition.”