Designing a Stormwater Management System for a 55-Acre Corporate Campus

When New Jersey Manufacturers Insurance Group
(NJM) developed their new Regional Operations Facility, a 55-acre corporate campus in Hammonton, New Jersey, they approached the construction with one major goal at the forefront: stormwater management.

Fundamental to that goal was designing a green infrastructure stormwater management system capable of containing on site nearly all the stormwater runoff generated by storm events up to and including a 100-year frequency, 24-hour duration storm.

The group hired Princeton Hydro, recognized as a leader in innovative, cost-effective, and environmentally sound stormwater management, to develop a concept plan that could be built within the context of proper stormwater management and meet the stringent requirements of the NJ Pinelands Comprehensive Management Plan.

To accomplish the ambitious stormwater management goals, the project team designed and implemented an integrated stormwater management system that combined traditional and green infrastructure components, and consisted of bioinfiltration basins, parking lot islands, a wetland basin, and a bioretention island. These features were designed to promote the interception, evapotranspiration, and infiltration of stormwater runoff at its source.

Emphasis was given to green infrastructure BMPs specifically capable of treating and infiltrating large volumes of runoff. Thus, all of the infiltration areas were designed using a soil amendment process where the underlying soils were excavated and amended with organic material to improve the underlying recharge capabilities of the soils. To complement the BMPs, the team designed and installed 120,000 gallon below-grade rainwater capture and reuse system. The system captures roof runoff to be used for on-site irrigation, which not only reduces stormwater volume but also decreases the facility’s water usage.

The project is one of the first projects in New Jersey built to infiltrate nearly 100% of the on-site runoff and uses site-design-based stormwater capacity to determine allowable impervious cover.

Before construction began, the team implemented a comprehensive study, which began with a detailed analysis of the site’s soils, with particular attention given to physical properties of the soil and the depth to seasonal high water (groundwater). During construction, Princeton Hydro provided monitoring services for all earthwork activities. Our team was on site full-time during critical activities to ensure that the project was built in accordance with the intent of the original design and ensure the maintenance of the project schedule. The team also provided environmental and geotechnical design and engineering services throughout the corporate campus construction, including the analysis of subsurface structures shop drawings and providing consultation support to the general contractor.

For the project, we partnered with Burgis Associates, Inc. who created site designs, provided landscape architectural and professional planning services, and helped to obtain agency approvals. The landscape program sought to establish native plant communities that filter runoff, provide an aesthetically pleasing visual, reduce invasive species, create habitat for pollinators and other critical species, and require limited maintenance to stay healthy and flourishing.

Post construction, the Princeton Hydro team led the preparation of the scope of services, budget, and proposal for the Stormwater Basin Maintenance, which included mowing and clearing the vegetation in nine infiltration basins. The basins were inspected monthly for functionality and for the presence of invasive plants. And, we are happy to report that the basins are all working properly and invasive plants have been eradicated.

At Princeton Hydro, we are experts in stormwater management; we recognize the numerous benefits of green infrastructure; and we’ve been incorporating green infrastructure into our engineering designs since before the term was regularly used in the stormwater lexicon. Click below to read about a Stormwater Treatment Train we designed and implemented in Thompson Park, a 675-acre recreation area in Middlesex County, New Jersey.

• Flood Mitigation
• Green Infrastructure
• Natural Resource Management
• Stormwater Management