Lots of rain and stormwater runoff in a short time can challenge any combined sewer system.

Just ask the operators of the Adams Street Wastewater Treatment Plant in Hoboken, New Jersey, where flooding in parts of the city is common. None was more challenging than the flood caused by the 14-foot storm surge produced by Hurricane Sandy in 2012, when nearly half the city was flooded.

“We were devastated, and the plant was offline for 24 hours,” says Phil Reeve, project manager for CH2M Hill at the 20.8 mgd (design) plant owned by North Hudson Sewerage Authority. “But through a lot of hard work and cooperation we were back to full treatment in five days.”

Part of the plan

Not long afterwards, Reeve and his staff coordinated the design and installation of two rain gardens, the first of them in Hoboken, as part of a site improvement project. As it happened, that effort gave the authority a head start on a regional planning effort called The Hoboken Green Infrastructure Strategic Plan, which evolved over the next two years.

Finalized in late 2013, the plan is part of a 13-county initiative in North Jersey called the Regional Plan for Sustainable Development. Funded by the U.S. Department of Housing and Urban Development, the plan outlines a variety of ways to reduce stormwater runoff, such as by constructing wetlands, building basins or ponds, creating vegetated swales, installing green roofs, minimizing areas of impervious surfaces, and installing rain gardens.

The two rain gardens at the Adams Street Plant are in front of the main administration building. Each captures flow from the parking lot and diverts it away from the combined sewer system.

The smaller garden is 44 by 18 feet; the larger one measures 90 by 10 feet. Both are designed to handle 3 inches of ponding. They drain through 12 inches of permeable soil on top of 6 inches of gravel. The certified sandy soil mixture is amended with up to 7 percent organics and contains less than 5 percent clay and silt.

Help with maintenance

The gardens support native grasses, sedges, rushes, ferns, shrubs and deep-rooted plants — some 800 in all. For aesthetics, an 18-inch-wide border of stone adorns each garden.

The plant staff performs only a small amount of maintenance; most of that work falls to students from Hoboken’s Stevens Institute of Technology. The students volunteer their time and do the work as part of a study by their professor, who monitors the capacity and water quality to determine the rain gardens’ efficiency.

Reeve says the rain gardens are the result of the second attempt to build them. In 2011, an anticipated grant from an irrigation equipment manufacturer to fund the project fell through, but the authority was so committed to the project that its leaders decided to pay for the gardens. Work was then interrupted by Hurricane Sandy.

“Our rain gardens have been very successful,” says Reeve. “The city has plans to build other infrastructure like rain gardens throughout the community, and we’d like to think it’s because ours have been so successful.”

Learning tools

Education is a big part of the rain gardens’ success. Besides the study by an expert in green infrastructure from the Stevens Institute, students from Columbia University and officials from the New Jersey Department of Environmental Protection have toured the plant. Tours conducted for students and the public also include the story of the rain gardens.

“Our goal in constructing the rain garden was to focus our local communities on green solutions in urban settings,” says Dr. Richard J. Wolff, the authority’s executive director.

“There is a great deal that can be done with green infrastructure in densely populated areas serviced by CSO collection systems. We wanted to set an example for developers and municipalities alike, and this rain garden has been a great step forward in that regard.”