The Panama Canal expansion project served as an impetus for the Delaware River main channel deepening a $300 million 102-mile long project slated for completion in 2017 and started in 2010. The project will deepen the river from 40 to 45 feet.
Like its individual ports the Delaware River needs an upgraded capacity lest the Mid-Atlantic region lose out on commerce involving larger Panamax vessels.
The U.S. Army Corps of Engineers and the Philadelphia Regional Port Authority (PRPA) have entered into a Project Partnership Agreement (PPA) to dredge as needed within the existing 40-foot Delaware River federal navigation channel deepening it to 45 feet. The project stretches from Philadelphia Harbor and Beckett Street Terminal in Camden New Jersey to the Atlantic Ocean (roughly between Cape May New Jersey and Broadkill Beach Delaware.)
Additionally several Delaware River ports are investing in their own infrastructure improvements to support the channel expansion said Dennis Rochford president of the Maritime Exchange for the Delaware River and Bay based in Philadelphia. Major commodities transported on the Delaware River include petroleum products steel chemicals agricultural products road salt lumber and “project cargo” including windmill blades and heavy equipment.
The Corps has spearheaded the massive project which involves seven contracts already awarded (some of them completed) and most likely three more contracts still to come for additional dredging and rock blasting. So far $178 million has been spent according to Ed Voigt chief of public and legislative affairs for the Corps’ Philadelphia District.
THE SEVEN CONTRACTS
• Norfolk Dredging Co. Chesapeake Virginia was awarded the first two contracts. In 2010 the firm dredged 3.6 million cubic yards using two pipeline cutter suction dredges – the Charleston and Pullen – and placed the materials in New Jersey’s Killcohook Confined Disposal Facility on the east river bank. The dredging area stretched from the Delaware Memorial Bridge in New Castle Delaware to Port Penn/Reedy Island about 12 miles south.
• In late 2011 and early 2012 Norfolk Dredging used the cutter suction dredges Charleston and Essex to remove 923000 cubic yards of materials from a four-mile stretch running from north of Wilmington Delaware to the Delaware Memorial Bridge. The dredged material was placed in the Pedricktown South Confined Disposal Facility in Salem County New Jersey Company spokesman Steve Newton said and a spud barge was attached to the cutter suction dredges.
• From September 2012 to February 2013 Great Lakes Dredge & Dock Company executed the first of its three Delaware River contracts. The firm deepened the channel from the Walt Whitman bridge in Philadelphia to southwest of the Philadelphia International Airport using two cutter suction dredges the Illinois and the Florida. About 1.2 million yards of dredged materials were removed from the 11-mile stretch and placed in the National Park Confined Disposal Facility in Gloucester County New Jersey.
• At about the time that Great Lakes Dredge & Dock was wrapping up with its first contract Dutra Dredging Co. began dredging a 14-mile stretch of the river between from Port Penn/Reedy Island to Woodland Beach Delaware using the Stuyvesant a 351-foot hopper dredge. The 1.3 million cubic yards of dredged materials removed from February through November 2013 were placed on the Artificial Island Confined Disposal Facility in the Delaware Bay.
• From July through October 2014 Great Lakes Dredge & Dock dredged 400000 cubic yards of material from southwest of Philadelphia International Airport to Chester Pennsylvania. The dredged material was placed in the Fort Mifflin Confined Disposal Facility in Pennsylvania. The firm used the Dodge Island and Padre Island both hopper dredges.
• The same firm was awarded a contract in May 2014 to dredge 700000 cubic yards of material from the Ben Franklin Bridge to the Walt Whitman Bridge in Philadelphia (2.4 miles) – the northernmost portion of the project. Work began in September 2014 and was slated to wrap up in March. Dredge 54 a clamshell dredge was used for the project and the Fort Mifflin CDF was again the placement site.
• In June 2014 Weeks Marine was awarded a contract to dredge 1.9 million cubic yards over a 15-mile stretch at the south end of the project. The dredged materials will be deposited on Delaware’s Broadkill Beach near the end of the shipping channel. This will help nourish the beach and prevent storm erosion. The B.E. Lindholm and R.N. Weeks are performing the work; mobilization was expected by late March with dredging and beachfill placement commencing in May company spokesman Tim Weckwerth said. The contract required completion date is April 2016.
Voigt said the Corps has not faced unforeseen problems that would increase costs or push back the completion date; however securing adequate funding each fiscal year can be challenging. The projected completion date has been 2017 for several years now.
Although some environmental groups have raised concerns about dredging possibly stirring up contaminated sediments Voigt put that notion to rest.
“All of our monitoring sampling testing and analysis leading up to construction indicated no toxic levels exceeding any applicable federal or state water quality criteria” Voigt stated in an email. “Moreover reports following each contract have supported that expectation.”
HYDROGRAPHIC SURVEYING TECHNOLOGY
Voigt noted that dramatic improvements in hydrographic survey technology have led to more accurate dredging volume calculations. In 1997 when an Environmental Impact Statement was published the original estimate for the Delaware River project was 33 million cubic yards of dredged materials. In recent years that was revised downward to 16 million cubic yards eliminating concerns that federal confined disposal sites for dredged material would not have sufficient capacity.
Multibeam technology GPS enhanced computer and data storage capabilities and updated tidal datum all have led to greater efficiencies and cost savings on the project Voigt said.
“When the Delaware River deepening project was originally started during the early 1980s single beam acoustic technology was widely used to conduct hydrographic surveys” Voigt said. This technology involved surveying lines across the channel at spacing ranging from 100 to 1000 feet. Only about five percent of the bottom was actually measured; extrapolation led to the final profile upon which dredge volumes were based.
Since the late 1990s multibeam technology has been used. A single sonar head produces multiple beams with every pulse generating a swath that’s about twice as wide as the water depth (i.e. a single pass in 40-foot-deep water would result in an 80-foot-wide measurement.) This technology results in close to 100 percent measurement of the channel bottom according to Voigt.
In addition to multibeam technology and other advancements the tidal datum – a reference point from which the Delaware channel depth is measured – is updated on a 20- to 25-year cycle. The Delaware River deepening project originally used tidal datum (compiled by the National Oceanic and Atmospheric Administration) from the 1960 to 1978 period. This was replaced by the 1983 to 2001 tidal datum epoch which resulted in a higher “0 point” (the point of reference) and thus indicating less material to remove. The update is a result of a combination of sealevel rise better measurement techniques and additional recording stations Voigt said.