Stony Hill Substation Access Road

Brookfield, ct

AI is providing roadway and drainage system design for the expansion of the Stony Hill Substation in Brookfield, CT. The substation is being expanded to install a synchronous condenser, and the current substation access road does not provide a feasible path to the expansion area, given the existing substation’s building and equipment placements. The existing access entrance and new access to the south of the station must be reconstructed and constructed, respectively, to accommodate a WB 67 Low-Boy trailer with a 5-in vertical ground clearance.

The 20-ft.-wide road is designed with a constant cross slope (no crown) to allow the trailer to maneuver through the site while maintaining ground clearance. The stormwater design is analyzed using HydroCAD modeling software, where the system components include culverts, riprap-armored conveyance swales, pocket ponds with forebays and permanent pools for water quality treatment, and a level spreader to safely discharge treated/detained runoff to an adjacent wetland. The culverts under the road are designed to safely pass the 100-year storm to provide protection and resiliency from large storm events.

The roadway alignment, profile, and grading are being designed in AutoCAD Civil 3D, which creates substantial design efficiencies, allowing for dynamic changes to the overall design model.

The 5-in vertical clearance for the Low-Boy trailer is being carefully considered during the design, given the heavy load that will be transported along the road. A turning and vertical clearance analysis was conducted using the AutoDesk Vehicle Tracking Module to Civil 3D. The vehicle tracking software allows for showing the vehicle’s horizontal and vertical pathways over the plan and profile designs to demonstrate to Eversource and their regulatory authorities that the roadway design will accommodate the delivery of the synchronous condenser.

AI services also include coordination with the substation electrical design team, Eversource, the Connecticut Siting Council, and other interested parties.


  • Duration: 2016 - Present
  • Project Scope:
    • Roadway design
    • Drainage conveyance, treatment & detention design
    • Storm resiliency
    • Grading
    • Storm water modeling