108 Interceptor Carlls River Watershed

West Babylon, NY

Suffolk County Department of Public Works

Contract Value:
$4.7 Million

Project Dates:
November 2021 - October 2022

  • Relocation of water main pipe, force main pipe, and electrical cables
  • Sampling and testing of soils
  • Asphalt Paving
  • Traffic Management
  • Micro-Tunneling
  • Vibration Monitoring
  • Ground freeze support of excavation


The sewer extension portion of this project consisted of a 48” Reinforced Concrete Pipe (RCP) installed approximately 25’ below grade. This pipe connects an existing manhole on the south side of the Southern State Parkway (SSP) to a newly constructed manhole on the north side, situated just east of the intersection of Lakeway Drive and Governor Avenue. The primary aim of this connection is to enable the homes in the area north of SSP to access the existing sewer system located south of the parkway. To carry out the installation of the 48″ RCP, we employed micro-tunneling techniques using a Micro Tunnel Boring Machine (MTBM). In order to facilitate this, we had to excavate two pits (a launch pit and a receiving pit), which were approximately 24’ diameter by 25’ depth. Since we were working in a heavy residential area, we opted for ground freezing as our method for Support of Excavation (SOE). This SOE approach allowed us to work in the residential areas with minimal effects to the homeowners and residents. To accommodate this work, we also undertook the permanent relocation of existing utilities, which included water mains, force mains for sewer, and electrical infrastructure. Additionally, the project comprised of installing three new manholes as well as the comprehensive restoration efforts such as landscaping, fencing, and paving.


Complexity (1): Working in a residential neighborhood having to excavate large pits while also maintaining safe access for the residents and keeping the work area safe. Complexity (2): Micro tunneling underneath the SSP brought up concerns of potential roadway settlement, which had to be continuously monitored.


Solution (1): Posillico sequenced the work accordingly so that only half the road was used at a time during utility relocations and excavation. The other half of the road was always open to maintain traffic. Also, we performed ground freeze SOE in lieu steel sheeting to minimize vibrations to residential homes.

Solution (2): We hired JR Cruz who is an expert in micro tunneling. Also, we hired Wang Technology to do continuous monitoring on the SSP while we were working.