National Grid – Patchogue Former MGP Site Remediation

Patchogue, NY

National Grid

Contract Value:

Project Dates:
2019 to 2020

  • Site Drainage and Sewer Contracting
  • Steel Sheet Piling
  • Stone, Sand, Clean Fill
  • Thermal Disorbtion and Recycling of Petroleum Contaminated Soils
  • Transportation and Disposal of Contaminated Soils
  • Hot Mix Asphalt
  • In-situ Soil Mixing
  • Remediation


This project was located on a former manufacturing gas plant site which had historic contamination that required remediation under a NYSDEC consent order. The site was remediated by in-situ soil stabilization involving soil mixing down to 22 feet below grade. The project scope included the installation of temporary sheet piles for slope protection along the Patchogue River, the removal of existent storm drainage structures and historic railroad tracks, the relocation of utilities, and the excavation and disposal of contaminated soil. The site restoration included the installation of a stone site cover, stormwater swale systems, and the asphalt paving of parking lots.


The project site was adjacent to the Patchogue River. This presented several challenges. The first was avoiding the spread of contamination through potential run-off into the river while the slurry was being mixed into the contaminated soil. The second, was the proximity of the work area to the edge of the water body which would require slope stabilization to maintain the integrity of the riverbank. Other challenges included safely managing truck traffic in and out of a commercial and residential area, the discovery of an existent gas leak that required repair, and scheduling delays due to the water table being higher than expected.


To address the challenges, Posillico installed and maintained a silt fence and haybales as erosion control measures to contain contamination; and installed temporary steel sheet piles as slope protection measures to allow equipment to safely move along the edge of the site. Prior to executing our scope of work, we performed private mark outs and test pitted utilities and anomalies, uncovering an existent gas leak. Posillico had this leak repaired by National Grid to avoid issues during construction. The higher-than-expected water table was resolved by backfilling the area with stone. This resolved the additional health and safety issues.