Monthly Update, May 2009
Restoration and landscaping of the excavated areas has been completed, and the trees and grass are growing in well.

On-going activities at the Hempstead Intersection Street former MGP Site include bimonthly monitoring and recovery of MGP tar from Site related wells.  Approximately 256 gallons of MGP tar have been collected since April, 2007.  Additional MGP tar recovery wells are planned for the site.  Groundwater samples are collected and analyzed quarterly to monitor the concentration and extent of the plume which have been stable over time.    

An interim remedial measure was completed in December 2008 that included the excavation, treatment, and disposal of shallow contaminated soils and liquids.  Approximately 4,400 cubic yards of contaminated soil and construction demolition debris was excavated and approximately 9,400 gallons of contaminated water and liquid MGP tar were removed.  The contaminated soils, construction demolition debris, and contaminated liquids were taken off-site for treatment and disposal.  A review copy of the interim remedial measure completion report was submitted to the New York State Department of Environmental Conservation (NYSDEC), New York State Department of Health (NYSDOH), and Nassau County Department of Health (NCDH) in May 2009. 

Engineering design of the off-site groundwater treatment systems is on-going.  The groundwater treatment systems design and contractor bidding is planned for 2009.  The start of construction is pending the acquisition of access agreements for properties not owned by National Grid.  Design of the In-Situ Solidification (ISS) remediation is on-going, which includes performing bench-scale treatability and leaching tests for the solidification mixture and numerical modeling to predict aquifer changes that will occur as a result of the ISS remediation.

A pre-design investigation for the ISS remediation and off-site groundwater treatment was completed in February, 2009.  The investigation included drilling soil borings to verify the extent of MGP contaminated soil that will be remediated by ISS, collecting groundwater samples to verify the boundaries of the dissolved-phase contaminant plume, and performing various hydrogeologic, geochemical, and geotechnical tests and environmental forensic analyses.  A review copy of the investigation report was issued to the NYSDEC, NYSDOH, and NCDH on May 12, 2009.  Additional delineation borings will be drilled at the site to further refine the extent of contaminated soil in certain areas.