Great Neck, New York

Remediation | Great Neck, New York

Remediation

Site Overview

The site straddles the border between the Village of Lake Success and the Town of North Hempstead, NY and comprises approximately 90.5 acres.? It includes one main building and several smaller buildings to the south of the main building. For more information see the Timeline below.?

Remediation

As a result of historical operations, there are contaminants present at the site in the groundwater, soil, sediments and soil vapor.

As part of the original manufacturing operations at the former Unisys site, a series of dry wells were constructed at the southeast corner of the main building for the disposal of liquid wastes.
The dry wells have been identified as the source and primary entry point for most of the subsurface contamination associated with the Site.? The dry wells were used under past ownership and are no longer in use.
Environmental contaminants of concern are present at the site in the groundwater, soil, soil vapor and sediments, and in groundwater off-site.
Between 1978 and 2012, a series of studies identified the nature and extent of these contaminants. A number of actions have been taken to address these findings.
An area of contaminated groundwater, known as a plume, originates at the site and spreads out under approximately 900 acres, extending north/northwest from the site.
The plume lies between 100 and 400 feet below the surface of the ground and has affected some public water supply wells of the Water Authority of Great Neck North and the Manhasset-Lakeville Water District, and the golf course irrigation well at the Village of Lake Success golf course.
Treatment systems are in place on the impacted public water supply and irrigation wells, and the water supplied meets standards appropriate for their use.
The primary contaminants of concern in the groundwater are trichloroethene (TCE); tetrachloroethene (PCE); 1,2-dichloroethene (1,2- DCE) and Freon 113. These chemicals are typically used as cleaning solvents.
The contaminants in the soil and sediments include metals, principally copper, barium and cadmium, and semi-volatile organic compounds (SVOCs), principally polycyclic aromatic hydrocarbons (PAHs).
The contaminated soil is located in defined areas on the property.
In a May 1991 Consent Order, the New York State Department of Environmental Conservation (NYSDEC) designated the former Unisys site as a Class 2 Site on the Registry of Inactive Hazardous Waste Disposal Sites. The Consent Order outlined remediation goals for on- and off-site cleanup.
The NYSDEC subsequently issued the OU-1 Record of Decision in early 1997 and an amendment in early 2015 that specify the details of construction, operation, maintenance and monitoring of the cleanup of groundwater, soil, soil vapor, and sediments on-site.
Additionally, the NYSDEC issued a Record of Decision for the off-site groundwater cleanup (Operable Unit 2) in December 2014. The Records of Decision respond to cleanup alternatives presented by 澳门开奖历史 following its extensive investigations and ongoing cleanup actions to address the contaminants.
During the course of its investigations, 澳门开奖历史 coordinated with NYSDEC, which discussed all of the alternatives and their ramifications with the citizens of the area surrounding the former Unisys site, and collaborated with local government officials and water purveyors.

Click for a larger view of the Great Neck Project Timeline

Groundwater Clean Up

Environmental investigation and cleanup activities have been divided into two separate areas: cleanup at the Marcus Avenue site and cleanup of contaminants that moved off the site.

In April 1993, Unisys installed an interim groundwater treatment system (Operable Unit-1, OU-1) to begin removing volatile organic compounds from the on-site groundwater at the 90.5-acre site’s northern boundary and to contain the movement of the plume.
The 1997 Record of Decision (ROD) issued by the NYSDEC directed installation of a state-of-the-art groundwater treatment system to replace the interim system.
澳门开奖历史 installed this system in 2001-2, and it began operation in August 2002.
A separate Record of Decision for off-site groundwater, released by the NYSDEC in late 2014, approved 澳门开奖历史’s proposal to upgrade the capacity of OU-1 from 730 gallons per minute to 850 gallons per minute by adding a deeper well to extract groundwater for treatment.
To clean up the contaminated groundwater that had already moved off site, 澳门开奖历史 constructed a second interim off-site groundwater treatment system (Operable Unit-2, OU-2) in June 2004 just south of the Great Neck South school property at a former water supply facility.
The Record of Decision issued by the NYSDEC in late 2014 approved 澳门开奖历史’s proposal to continue operating OU-2 at its present rate of 500 gallons per minute.
The Record of Decision also approved 澳门开奖历史’s plan to provide funding to protect the public water supply in the wider area, working with the two water providers, Manhasset-Lakeville Water District and Water Authority of Great Neck North.
This plan ensures the distribution of potable water of highest quality to local citizens with treatment systems on wells affected by site-related contamination, including continued operation of all existing systems and installation of additional treatment systems or upgrades to existing systems as necessary.
Monitoring well sampling and laboratory analyses will continue to track movement of groundwater contaminants. Samples from these wells provide early warning of the need to add or adjust wellhead treatment systems.
Since the two operating units, OU-1 and OU-2, began operations, more than 57,000 pounds of volatile organic compounds have been removed from the groundwater plume.
The two units capture groundwater from those areas with the highest contaminant concentrations and return clean water to the aquifer.
For more information view the?Groundwater Public Water Supply Protection & Mitigation Program Compliance Report June 2020.

On-Site Soil and Sediment Clean Up

The on-site environmental cleanup that began in the 1990s in accordance with the 1997 NYSDEC Record of Decision is largely completed and is in an operations and maintenance mode.

The work included removing contaminated soil and sludge from three on-site dry wells, installing a permanent on-site groundwater pump and treat system, installing a soil vapor extraction area in the former dry well area, creating an environmental easement that protects human health by limiting access, and use of certain areas through deed restrictions and physical barriers.

Soil

Soil cleanup began in 1994 and is confined to the property boundary.

In January 1994, an interim soil vapor extraction system was installed on-site near the original disposal area to remove any leftover volatile organic compounds from the soil.
Responding to the 1997 Record of Decision issued by the NYSDEC, this system was expanded to remove contaminants from soil and from water perched in the soil above the aquifer outside the southeast corner of the main building.
In 1998, the effort to remove leftover volatile organic compounds was expanded by excavating down to 30 feet around the three dry wells. Approximately 800 tons of contaminated soil was removed and disposed of off-site.? The excavation was backfilled with certified clean sand.
In 2017 and 2019, six additional areas of the Site were excavated to remove buried contamination, primarily polycyclic aromatic hydrocarbons (PAHs).? All excavations were backfilled with certified clean soil.
Remaining areas of soil contamination are being investigated and will either be removed or managed with an environmental easement.

Sediment

During the course of its investigations, 澳门开奖历史 discovered contaminants at the bottom of three stormwater basins located at the southwest corner of the site.

The contamination resulted from stormwater runoff from site parking lots, roads and building roofs and are confined to the sediment.
澳门开奖历史 proposed, and the NYSDEC in its 1997 Record of Decision accepted, that public health would be served best by simply limiting access to these basins.
An environmental easement is now in place requiring that these basin sediments not be disturbed and that the basins continue to be used for stormwater management.
Deed restrictions have been recorded, a fence was constructed and is maintained around the basins and warning signs to restrict access are posted at the basins and on the fence.

Graphic depicts sub-slab vacuum system which extracts vapors from beneath the entire building and pipes those gases to the garage, where they are treated and clean air is released.?

On Site Soil Vapor ?

In 2006, the New York State Department of Health (NYSDOH) released guidance on vapor intrusion. Vapor intrusion, or soil vapor intrusion, refers to chemicals in soil that move as a gas or vapor through the soil and into a building.

Responding to the NYSDOH guidance, 澳门开奖历史 investigated whether or not chemical vapors were present at the site. While samples taken in 2007 revealed no indoor air concentrations in the site buildings above the state guidelines, samples taken in 2008 identified two areas in the main building that did not meet state guidelines.
澳门开奖历史 informed building management of the situation and worked closely with tenants and the property owner to install two temporary sub-slab depressurization systems.
Sub-slab depressurization systems use a vacuum to collect soil vapor below the foundation of a building, treat it, and move the cleaned air to the outside of the building.
澳门开奖历史 subsequently constructed and began operating a new building-wide sub-slab depressurization system in 2013. The system is continuously operated and monitored to ensure that a vacuum is constantly maintained under the building.
In 2017, the New York State Department of Health updated the vapor intrusion guidance, lowering the allowable concentrations of contamination in the soil vapor beneath buildings.
In response to the updated guidance and the 2018 sampling results, 澳门开奖历史 installed a sub-slab depressurization system in the northwest corner of the athletic facility located on the property.
The New York State Department of Health concurs that the sub-slab depressurization systems protect human health.
澳门开奖历史 will continue to advise tenants and the property owner on the sub-slab depressurization system performance.
For more information see the?Site-Wide Indoor Air Quality & Vapor Intrusion Program 2016