Monthly Update, May/June 2010

National Grid to Begin Installation Work for Groundwater Treatment System Between Mirschel Park and Kensington Court

Project Intended to Remediate Groundwater Related to the Hempstead MGP Site

Temporary Inconvenience Possible for Certain Walkways, Driveways and Roads

National Grid is starting the installation of the underground oxygen delivery system located from Mirschel Park to Kensington Court. The oxygenation system will treat the groundwater plume associated with the Hempstead former Manufactured Gas Plant (MGP) Site by accelerating the rate of natural bioremediation within the groundwater plume. The wells and oxygen lines will be installed in Mirschel Park, on private property at 158 Hilton Avenue, along the right-of-way on the east side of Hilton Avenue, and on the south side of Kensington Court. Part of the oxygenation system installation work includes crossing the system piping under Hilton Avenue in the area of Kensington Court. This part of the work is planned for the July 2010 timeframe, and it will temporarily restrict traffic flow along Hilton Avenue during the daytime for about 2 to 3 days while the crossing work is completed. Please see the attached figure showing the location of the treatment systems.

The work in Mirschel Park is scheduled to start the week of May 24. The installation of the oxygenation system will include installing small diameter wells in pre-determined locations, and oxygen injection lines will be placed into the trenches and connected to the wells. The oxygen lines will be connected to an oxygen generator that will be located at 158 Hilton Avenue.

Excavating equipment will be used for digging piping trenches in Mirschel Park and in the road right-of-ways. Based on the completed environmental investigations in the area, the shallow soils to be excavated are not contaminated from the former MGP Site. Each day, after wells and lines are installed, the trenches will be secured. The trenching and installation of the wells for each system should take approximately 3-4 months, depending on the weather. After all of the work is done, the areas will be fully restored.

The work will be conducted with oversight from the New York State Department of Environmental Conservation, the New York State Department of Health, and the Nassau County Department of Health.

Should you have any questions or concerns about the work, please use National Grid’s Hempstead Intersection Street Project Hotline at 516 545 6161. Additional information about the investigation and remediation of the Hempstead Intersection Street former MGP Site is also available on the project website at

Thank you for your cooperation as we continue to make progress addressing the environmental issues associated with the Hempstead former Manufactured Gas Plant Site.

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