Underground Stormwater Detention, Piscataway NJ

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Project Overview

Underground stormwater detention was at the heart of this warehouse site development on South Washington Avenue in Piscataway, NJ. The 24.55-acre site supports two 180,000 SF warehouses, both designed for steady truck traffic.

On a site like this, space matters. Every acre used for a surface detention basin is an acre that can’t hold trailers or loading areas. The solution was to move stormwater storage below ground. That decision shaped much of Pillari’s work on the project.

Building the Detention Systems

Pillari’s underground utilities and drainage crews installed three large StormTrap detention systems. Together, they provide 239,310 CF of underground storage.

Each system is built from precast concrete modules, 469 pieces in all. Crews set every piece on a prepared stone base, keeping the modules level and aligned so the system performs as designed. It’s careful, precise work, and it’s what allows the paved area above to carry heavy trucks every day.

The detention systems connect to precast outlet control structures, which manage how quickly water leaves the site. Contech StormFilter water quality units then treat the runoff before it’s released. Together, these components meet the project’s stormwater management requirements.

Utilities for Each Building

Beyond drainage, Pillari brought essential services to both warehouses. Crews installed two E-One pump stations and 1,300 LF of SDR-11 force main to carry wastewater away from the buildings. They also ran more than 4,000 LF of C900 water main to supply each warehouse.

The Result

The finished site gives the owner the room it needs for truck parking and circulation, with the stormwater system working out of sight below. This project shows how well-planned underground utility work can make a site development more efficient from the ground up.