From October 1 to November 15 Barnegat Bay Dredging Co. Inc. dredged sediment from the New Jersey Intracoastal Waterway (NJIWW) near Mordecai Island in Beach Haven New Jersey. The U.S. Army Corps of Engineers Philadelphia District project placed the sediment into a breach on the island removing a shoal and navigation hazard from the waterway and rebuilding the island where it had eroded.
To develop marsh restoration and habitat creation projects along the NJIWW the Philadelphia District partnered with the Corps’ Engineer Research & Development Center. The district’s Regional Sediment Management program wanted to improve standard business practices by beneficially using material where it could said Project Manager for the Operations Division U.S. Army Corps of Engineers Philadelphia District Monica Chasten. She is responsible for federal navigation channels along the New Jersey and Delaware coast.
The Corps developed two pilot projects to dredge sediment and place it for beneficial use completed in partnership with the New Jersey Division of Fish & Wildlife The Nature Conservancy and the Green Trust Alliance which operated under a grant from the National Fish & Wildlife Foundation.
The dredge Fullerton took sand from the NJIWW and pumped via approximately 3000 feet of 14-inch pipeline to a breach on the island.
Barnegat Bay Dredging under contract with the Philadelphia District performed dredge work near Stone Harbor and Avalon New Jersey to create bird habitat and to raise low-lying areas and restore wetland by placing a thin-layer of dredged sediment. The Stone Harbor project was completed in September 2014. The Avalon project was completed in December 2014. The district said recent environmental monitoring has shown success on those projects. Barnegat Bay Dredging has worked with the district on a number of projects under two recent emergency supplemental contracts. The first one lasted 18 months and the second will run nine months.
This was a departure from typical dredging projects in the area and could be doubly important for the Philadelphia District given the lack of capacity in local confined disposal facility (CDF) sites. The projects also served as a model for the Mordecai Island project.
Barnegat Bay Dredging had to place the sand very precisely according to permit regulations. Turbidity curtains (seen on the right side of the photo) form a barrier for sand on the east side. The sand was not dewatered on the west side and left to form a more natural slope.
Chasten said dredged material there would typically go to the Parker’s Island CDF. “[The CDF] is quite small and also used by local marinas and the state for dredged material” she said. The sediment dredged from the NJIWW was 80 percent sand so it was optimal for beneficial use.
The work at Mordecai Island cleared the shoal in the channel 100 feet wide and six feet deep including a few sections of advanced maintenance Chasten said. The work was funded 100 percent with O&M funds and cost approximately $800000.
After years of erosion the once whole island was a small strip of land and a larger portion both at two different elevations. The sand placement brought the two pieces back together.
Erosion on Mordecai Island had left a small strip of land and a larger portion. The sand placement brought the two together and the Corps will return in the spring to plant native species.
On the east side of the placement area the project guidelines forced the contractor to contain the sand within a specific boundary. This involved tight placement and a small cap on the pipeline to dewater. Placement on the west side did not involve dewatering and Chasten said they were very happy with the natural slope where the placement was not constricted. “We had some back and forth with regulators and it left a beautiful beach slope that is breaking the waves way before they get to the island” Chasten said. She said that slope was a great lesson learned from the project.
Placement on the east side was much more restricted on where sand could go. With turbidity curtains marking the boundaries the placement took “incredible site control” on the part of the contractor Chasten said.
“You have to learn how to control the sand” said Joe Hill owner of Barnegat Bay Dredging. The state permit dictated tight boundaries and the contractor used turbidity curtains to control the placement which Hill said worked very well in a very dynamic process. Sand isn’t placed statically in one spot. The pipeline is constantly moving to control the placement. A berm is built up first in order to direct the flow of sand where it needs to go. Overall Hill said that project was simple to execute.
The dredge Fullerton a 14-inch hydraulic pipeline dredge took sediment from the NJIWW between markers 107 and 109 near Mordecai Island approximately 500 feet from the placement site at the island and pumped the sand in about 3000 feet of pipeline to the placement area on the island. Skid loaders also worked on-site to move material around.
The more challenging work for the Philadelphia District is at the other ongoing project at Avalon and involves spraying the meadows with sediment. This project mimics a process tested in the first two pilot projects. With a spray nozzle on the end of the pipeline it spread sediment three to six inches thick over an area. “It’s a new process for us and the Corps. We’ve done it before and it worked out very well” Hill said. “It could be a very good thing for the area.” Work began again in November 2015 and will continue through February 2016.
“We hope this will become important in thefuture” Hill said citing problems with placement sites in the area. “What we’ve done with Mordecai Island and in Avalon it’s one of the first projects like it in the area. The state is coming out with more projects like it.”
Barnegat Bay Dredging Co. Inc. has been in business since 1931 doing hydraulic dredging in the Northeast U.S. mainly for federal and state agencies