West 17th Street MGP Remediation

Manhattan, NY

HLP Properties, LLC

Contract Value:
$12.8 Million

Project Dates:
2013 - 2014

  • Steel Sheet Piling- installed 440 LF of a steel sheeting containment wall.
  • Dewatering and water treatment
  • In-Situ Soil Mixing- Mixed 14,100 CY
  • Asphalt Paving and site restoration
  • Soil characterization testing, approvals, and T&D of 6,200 tons of Contaminated Soils
  • New Sidewalks- Placed 4900 of sidewalk SF
  • Clean fill procurement testing and placement.


The project site was an operating commuter pay parking lot. The High Line Park split the site into two locations. In the first phase, we had to remove all the existing structures, contaminated soil, and asphalt to the east of the Highline, 3′ below existing grade. During the second phase, we had to excavate the entire site to a depth of 7′ below grade. Then a 440′ long DNAPL containment wall was constructed along the West Side Highway and 17th & 18th Street. The containment wall was fully interlocked, coated and the interlocks completely sealed. The wall’s depth varied from a maximum of 40′ to a minimum of 25′ below grade. The center of this phase required the performing of In-Situ Stabilization (ISS) to a depth of 25′ below grade. After ISS was completed, the site had to be fully restored as a parking lot with new sidewalks and pavement.


In- situ stabilization (ISS) is a complex and delicate process that requires high precision and expertise. Moreover, the excavation and dewatering had to be carried out carefully to avoid any damage to NYC Park called the Highline and ensure the safety of its visitors. An additional concern of the NYSDEC representative was dust and odor suppression.


Meetings were held with all stakeholders that stressed the demand that construction not interfere with active use of the open park.  CAMP units were stationed on the Highline to record fugitive dust and odors. Posillico staged the site to minimize the impacts to the public and the project was completed without any incident.  All CAMP readings were below the allowable limits for the projects.