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Cleanup of National Grid Site Nears Second Phase

Posted on 04 December 2008

On the lot where the big blue gas ball once stood it looks like winter has come early to Sag Harbor. On a dark gray November day trucks rumbled and the brown earth was crested by white; the scene was like an urban building project crusted with snow.

The white, however, was a layer of foam meant to keep down the odor of chemicals and coal tar, which was being dredged up on the property. It is all part of the first phase of remediating the property, removing tons of soil that have been contaminated by years of dumping toxic coal waste and cleaning the groundwater beneath that is laced with carcinogenic chemicals. A walk past the site offers only a hint of the bitter and caustic stuff that lies beneath the surface, a testament to the success the cleanup crew has had so far in keeping down — but not eliminating — the impact on the neighbors.

The remediation project, which began in earnest in mid-September, is reaching the start of its second phase, digging out tons of soil and treating millions of gallons of contaminated water a day. In the past several weeks National Grid and its subcontractors have been building an underground wall, 17-feet deep, around the perimeter of the .8-acre site to be remediated. They have been using an auger to drill holes, at times ten-feet in diameter and filling the holes with a slurry of water and Portland cement. The holes, backed up to one another, form a wall that is about 12-feet thick and will form a sort of dam to keep the earth from falling into pits they will be digging throughout the site.

Last Tuesday, November 25, village officials, including Mayor Greg Ferraris and trustee Ed Deyermond, as well as Harbor Committee members Bruce Tait and Jeff Peters, toured the site and received a presentation on where the project goes from here.

As slurry flowed in a river outside, the officials stood around a table inside the former annex for Fisher’s Home Furnishings, a space National Grid has taken over as a sort of command center. A set of windows look out over the construction site, and just feet away from the building’s wall an auger pressed through the dirt pulling up dark black dirt along the southern boundary of the remediation.

Once the boundary has been secured, National Grid will bring in a 100’-by-140’ tent that will be moved around the site over the next seven months. It is beneath this tent that most of the clearing work will be done. Essentially, two things will occur: contaminated soil will be trucked out and disposed of, and water will be pumped, cleaned and released into the bay beyond the breakwater.

The design calls for the tent to be set so that two sides are always sitting on the underground walls. Steel walls will then be driven to hold up the dirt on the other two sides while the soil is dug out. Dozens of test borings have already been completed to test for contaminants beneath the soil, and the site carved up into a matrix, indicating the more contaminated sections, and helping workers decide where certain sections of soil will be disposed of. At least six sites have been selected to receive the waste, in New Jersey, Pennsylvania, Delaware and upstate New York.

Before the digging begins, however, wells will be drilled around the perimeter of the tent that will then be used to remove groundwater from the section to a level below the point where the soil will be excavated. On most of the site, soil will be excavated to a depth of nine feet, with some deeper cuts going as far as 11 feet. The water is then pumped through filters and out to the bay where it will be released through a diffuser, a length of pipe about 200-feet long with hundreds of holes to allow the fresh water to have a minimized impact on the saltwater environment of the bay.

The process is then repeated as the tent is re-positioned six times to cover the entire site, with the greatest intensity of contamination at the rough center of the property. It was there, explains project manager Ted Leissing, that a plant in the early part of the 20th century manufactured gas by burning coal that once lit the village. The coal tar and fluid that resulted was dumped into the ground on the site. The chemicals associated with the contamination, several of which are carcinogenic, include benzene, ethyl benzene, xylene and tuolene.

When the tent arrives in the next couple weeks, workers will not be required to wear masks or respirators inside, despite the fact that it is an enclosed space. That is because a negative air pressure system is designed for the space, which will ensure fresh air is brought in from the outside and the contaminated air is pumped outside and through a carbon filter before being released into the air. The release is monitored to meet DEC standards. The perimeter of the site is monitored as well with a half-dozen air-quality monitors that report to computers at the site as well as at National Grid’s main office and workers’ cell phones. Last week, as contractors moved soil around on the property, the monitors were indicating that contaminants were exiting the site at a rate of .1 parts per million. By their agreement with the DEC, they are allowed to work at a level of 5 parts per million, but they have set a threshold of 3.7 parts per million when an alarm would sound and they would shut work down. They will get warnings at 1 ppm.

To date there have been about a half-dozen times when limits have been exceeded, but, said Leissing, they were not related to site work, and had been triggered by such things as truck exhaust too close to a monitoring station.

The project is being overseen by the state Department of Environmental Conservation, which has established standards for water and air as it leaves the property. A DEC representative is on site each day observing the work.

The groundwater pulled from beneath the soil will be pumped through carbon and sand filters. For passersby, these are among the most visible parts of the cleanup, as the tanks tower over the fence that has been put up around the site.

Before the system becomes fully operational, water will be looped through the filters and tested before it is released into the water. National Grid must meet a set of standards of water quality with its filtration system, and the DEC will test before the pumping into the bay begins. Once the system starts, however, water testing will occur once a week, with samples being sent to a lab by National Grid, and the results then reviewed by the DEC.

There has been at least one misstep so far with the project. While augering holes for the underground wall, workers drilled through two outflow sewer pipes that led to the sewer line beneath Long Island Avenue.

About 150 – 200 feet of sewer line filled with the slurry and hardened, blocking the sewer line like an artery clogged with plaque. Subcontractors have been working for the past few weeks drilling through the cement with a tool called an Intruder, and will ultimately install a vinyl liner to make the sewer line operational. In the meantime, National Grid has been providing a tank truck to collect the waste from the occupied buildings at the affected section of the sewer line, and bring the waste to the village’s wastewater treatment plant on Bay Street each morning.

Work on the project is expected to be completed by Memorial Day.

 

 

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