GZA provided engineering, permitting and construction support services to the Town of Marshfield for the Bass Creek Restoration Project. The project consisted of the removal of invasive vegetation (Phragmites australis) and dredging of approximately 1,500 CY of sediments to help alleviate flooding, remove invasive species, and improve tidal flushing, water quality and wildlife and fisheries habitat.
The project was located within a Coastal Wetlands Restriction and Priority Habitat for several state-listed species, including the Eastern Box Turtle, Common Moorhen, Least Bittern, Sharp-shinned Hawk and Upland Sandpiper. Habitat Assessments and MESA consultation were conducted to assure that the project would not adversely affect species present. Restoration plans were developed for temporary impacts at the staging and access areas. GZA also coordinated with the Massachusetts Audubon Society, an abutting landowner, to minimize potential impacts to their property and address their concerns on potential project impacts on wildlife habitat.
Beginning in 2014, a 10-foot wide by 1-foot deep channel was mechanically dredged along 3,600 feet of the creek with equipment access/staging available at two locations along this length. Dredging and invasive species removal was performed using an amphibious excavator. Sediments consisted of sand with some organics and were approved for beneficial reuse. All nuisance vegetation and dredge sediments were removed from the site.
The project was completed in 2014 and GZA is currently providing long-term monitoring to document the effects of improved tidal flushing on the system. This monitoring includes seasonal and yearly documentation of salinity and vegetation transition along the channel at five established transect locations Our observations to date indicate that Phragmites stands have receded and salinity values have increased from 0.1 ppt prior to restoration to 20.5 ppt post restoration.