US Army Corps of Engineers
Philadelphia District & Marine Design Center

The dual benefits of dredging

USACE Philadelphia District
Published Jan. 19, 2017
In 2015, the U.S. Army Corps of Engineers' Philadelphia District conducted dredging operations in the Delaware River to deepen the channel and then beneficially used the material to build a dune and berm in Broadkill Beach, DE and reduce the risk of coastal storms for the community.

In 2015, the U.S. Army Corps of Engineers' Philadelphia District conducted dredging operations in the Delaware River to deepen the channel and then beneficially used the material to build a dune and berm in Broadkill Beach, DE and reduce the risk of coastal storms for the community.

Why dredge? In the maritime community, the answer has long been obvious. The benefits of dredging have to do with what is taken out.

But there is another side to dredging, where the benefits have to do with what is added in. This describes most of the beach nourishment projects now in place along the New Jersey and Delaware coastlines.

Better still is when both types of benefits are combined into one project -- such as the Delaware River Main Channel Deepening.

The biggest and best known example was the project's seventh construction contract, in which one U.S. Army Corps of Engineers project was used directly to construct another. All the sand removed in deepening the southernmost 15 miles of the channel was pumped ashore to Broadkill Beach, Del., where it was used to construct a new dune and beachfill to reduce the risk of storm damages for that Delaware Bay community.

In addition, part of the main channel served as the borrow area when the Corps built a similar dune-and-beachfill project at Oakwood Beach (Salem County), N.J.; deepening material previously deposited at two of the Corps' riverside disposal areas was re-used for road construction projects in Delaware and road construction and site work in southern New Jersey; and even now, during the second phase of the eight contract (rock blasting), the New Jersey Department of Environmental Protection is having all the dredged rock hauled down to just offshore of Wildwood, N.J., to help build a new submerged artificial reef.

And that's just what relates to the channel deepening effort. For decades, the Delaware River 40-foot channel and other Corps navigation projects have served as prime sources of sand-and-gravel earthfill, as made available at Corps-owned disposal areas to any and all takers. Beneficial use of dredged material helped create the Camden Waterfront District, the RiverWinds Golf & Tennis Club, Palmyra Cove Nature Park, the commuter runway at the Philadelphia International Airport, commercial redevelopment (now underway) of the former Fort DuPont in Delaware, and numerous other road construction and site development projects. Along the New Jersey coast, sand dredged from the Intracoastal Waterway and coastal inlets has been used extensively to restore marsh and build islands. 

Finally, looking beyond the Delaware Valley, a pilot project about 10 years ago up in Hazelton, Pa., showed how some of the finer silts and clays -- dredged material typically not of much use for construction work -- could be transported by truck and rail to abandoned mine sites and used to help combat acid drainage.

And who knows what other potential beneficial uses lie ahead? The Corps has feasibility studies underway to identify such opportunities on both sides of the Delaware River and Bay.

For the Delaware River Ports, dredging has always been first and foremost about navigation, and that's not about to change. What is changing is that more and more, dredging's benefits are extending to other areas as well.