Volunteers prepare floating wetlands islands for installation. Native wetlands plants are secured into a “mattress” made of recycled plastics, which is then placed into a lake or pond. The plants’ roots grow through the recycled bed and help to improve water quality by removing sediment and excess nutrients. PHOTO COURTESY OF FREEHOLD SOIL CONSERVATION DISTRICT Floating wetlands islands and the bioconversion of water detention basins are part of a project underway that aims to mitigate impacts caused by urbanization to the Manalapan Brook watershed.
Spanning Middlesex and Monmouth counties, the project, which is funded by a $500,000 grant from the N.J. Department of Environmental Protection, involves improvements intended to combat erosion, reintroduce native plant life and improve the quality of the water flowing in the Manalapan Brook.
“The goal of the project is to use nature to restore the watershed and help improve the water quality, reduce stormwater runoff and flooding issues,” said Michele Bakacs, environmental and resource management agent for the Rutgers Cooperative Extension of Middlesex County.
The Manalapan Brook starts in the Manalapan of Monmouth County and travels north into Middlesex County through Monroe, finally meeting the Matchaponix Brook on the Spotswood-Old Bridge boundary to form the South River at DuHerNaL Lake.
Towns located within the watershed of the brooks include Manalapan, Monroe, Spotswood and Old Bridge.
A group of organizations lead by the grantee — Freehold Soil Conservation District — is taking part in the project, including Rutgers Cooperative Extension, Princeton Hydro, Monroe, Manalapan, and Middlesex and Monmouth counties.
According to Bakacs, a number of improvements will be incorporated to achieve the project’s goals. Chief among them are last year’s installation of floating wetlands islands, which are man-made islands that encourage the growth of wetlands flora and provide a habitat for wildlife.
“Those islands have become more and more popular for helping to improve the water quality of ponds and lakes. The idea is that they are easy to install and easy to maintain,” Bakacs said, adding that the floating islands were installed in spring 2014 during the first phase of the project.
Native wetland flora is planted into a bed of recycled plastics, which floats on top of the water. Once the plants flourish, they excel at breaking down pollutants in the water and excess nutrients that would encourage algae overgrowth.
According to Bakacs, research also shows that the floating islands help to remove sediment that has built up in the waterway. Sediment can have adverse affects on habitats relied upon by local animal life. Inez Zimmerman, district manager of the Freehold Soil Conservation District, said each aspect of the project was selected from a much larger list of potential improvements.
Upon receiving the grant, Zimmerman said several were prioritized for implementation.
The next step will be to naturalize detention basins, where water is held and slowly released into waterways after a storm. Much of the water is often contaminated, and detention basins do little to help infiltrate that water naturally.
Improving the soil, removing concrete channels and planting flood-tolerant plants can help to mitigate those issues, Zimmerman said.
“Three detention basin overhauls are going to take out the existing grass vegetations and substitute in more low-maintenance plantings,” Zimmerman said. “Also, [we will install] different fixtures in the detention basins that will allow for greater water quality.”
Three basins are targeted in the project, including one in Monroe and two in Manalapan.
John Riggs, chair of Monroe’s Environmental Commission, said the township is a central part of the project, including improvements at Manalapan Lake in Thompson Park, the detention basin conversion and the installation of rain gardens. In addition, a project to limit runoff from the Thompson Park zoo will also be included in the project.
According to Riggs, the initial rain garden plantings and the installation of floating wetland islands at Thompson Park are already completed.
In the future, an additional rain garden will be installed at Thompson Park, the New Street basin conversion will take place, and several bank stabilization projects will take place along the Manalapan Brook.
“This has been a problem for years, and this is a pilot-type thing,” Riggs said. “I just think it’s a great example of state agencies, county agencies and municipalities working together to solve a problem.”
Riggs added that with each improvement, there will be educational signage for the public, and the town has developed a brochure to inform school-age children about the purpose of the improvements.
According to Zimmerman, the crux of the project is harnessing natural processes to enhance the quality of the water and viability of the watershed.
“You want to take advantage of these plantings that offer some water-quality treatment. We’re also trying to delay the flow path of the water [in basins] to allow the opportunity for some infiltration,” Zimmerman said.
Other issues the project seeks to address are erosion and stormwater runoff. It also aims to help educate the public about exactly why these projects are beneficial.
Water-quality testing is required before and after as a condition of the grant award, but Zimmerman said she expects the impact to be significant.
“Where the engineers have done this previously, they saw a great improvement in water quality,” she said.
She expects additional work to begin on the detention basins and Thompson Park shortly.