Lawrence Brook Wetland Mitigation Site

Princeton Hydro worked collaboratively with GreenVest to design the 25-acre Lawrence Brook wetland mitigation site. The site is situated at the confluence of the Lawrence Brook and the Raritan River and is an important urban/estuarine mixing zone providing habitat for wading birds, waterfowl, fish, and invertebrates. Its tidally influenced wetlands were extensively ditched for mosquito control and completely dominated by the invasive Common Reed (Phragmites australis).

This mitigation project provided compensatory mitigation for the former National Lead site redevelopment project. The primary objective was to eliminate Common Reed and replace the site with a more desirable and species-rich plant community. The project also included a wetland creation component. Princeton Hydro prepared the engineering plans in a collaborative effort with GreenVest. The design included clearing and grubbing of invasive species, excavation of accreted sediments within the wetland restoration areas to achieve optimal marsh elevations, placement of excavated material within proposed upload forested areas, re-vegetation of restoration areas with native plant species, and installation of wildlife exclusion systems and fencing to prevent herbivory. Although the plan emphasized the restoration of estuarine wetland, the project also included forested/scrub-shrub freshwater wetlands, maritime upland forest, and riparian buffers.

Princeton Hydro was also retained to manage the invasive species control program for the project site, which targeted the elimination of Common Reed, and allowed a number of desirable tidal wetland species to colonize the site. Subsequent to completion of several treatments, the dead stalks and thatch were removed from the marsh plain to facilitate the establishment of planted material as well as allow for plant species present in the marsh’s seed bank to emerge. The wetland responded extremely well to this restoration project and the site is dominated by a species-rich intertidal plant community that includes several rare species.