Contractors remove the existing concrete roadway across the St. Georges Bridge in New Castle County, Del.
(U.S. Army Corps of Engineers photo)
Everyone likes short cuts. It saves time. It saves fuel and it saves aggravation. Business leaders in the late 1700s envisioned such a short cut slicing through a narrow strip of land to build a waterway linking the Chesapeake Bay with the Delaware River. In 1829, the Chesapeake and Delaware Canal opened for business.
With the opening of the canal, ships leaving Baltimore harbor could save more than 300 mi. from traveling the full length of the Chesapeake Bay and out into the Atlantic. This saving has been especially influential for ships traveling from Baltimore to Philadelphia, New York, Boston and Europe.
In 1919, the U. S. Army Corps of Engineers took over the operation of the C & D Canal. Regular dredging has continued until today as the canal is maintained at a depth of 35 ft. and a width of 450 ft. The canal is one of the busiest in the nation.
Of course, to make all of this feasible, bridges need to be in place that are tall enough to allow passage for the giant vessels while traffic can continue overhead.
The Corps is starting a deck replacement and steel repair of the Saint George's Bridge. The bridge rehabilitation will cost $45.8 million and will be handled by contractor J. D. Eckman. The bridge work is expected to take approximately 18 months. The bridge normally carries traffic from Delaware Route 13 over the canal.
Four other bridges arch over the canal and will carry traffic while the bridge is being rehabilitated. All five of the bridges over the canal are owned and operated by the Corps.
Timothy J. Kelly, deputy chief, operations division of the Corps' Philadelphia District, commented on the annual dredging in the canal which typically costs between $10-$12 million. "We usually remove about 400,000 cubic yards of sediment from the approach channels each year," he said.
Without the dredging activities, the approach channel would fill up slowly and impede the large ship traffic.
"Nearly 30 percent of the cargo coming into the Port of Baltimore travels through the canal," said Kelly. "Most of this cargo is cars, tractors and vehicles that can roll on and roll off. The cargo is transported on specialized ships that are used for vehicles. Fuel and bulk materials are brought through the canal using tugs and barges.
Kelly added that the Army Corps regularly surveys the federal channel of the Canal and Delaware River and shares that information with pilots and mariners to help them safely navigate.
The most recent dredging was done by Corman Kokosing Construction Co., of Annapolis Junction, Md. The company used a mechanical bucket to remove sediment from the channel and placed it in a barge. The barge is then pushed by a tugboat back toward the shoreline and sediment is offloaded at a Corps-owned dredged material disposal site.
Bridge Work
With annual dredging activities wrapped up, the Corps has turned its attention on the Saint George's Bridge, a steel-tied arch bridge that is 135 ft. above the waters of the canal. The bridge was built in 1942.
Work has begun in earnest with the first objectives being to remove the existing concrete roadway. Work will ultimately replace the entire deck, railings, drainage features and include some steel repair.
Project planners are taking special precautions to make sure the construction activities do not result in material falling into the canal more than 100 ft. below. The containment also will catch dust from sand blasting and other work. With work on any bridge, fall protection safety guidelines are in place.
Delaware Department of Transportation (DELDOT) requires bridge decks to have nylon fibers in the mix to increase durability of the concrete. It also will have a shrinkage compensating admixture, which will prevent normal temperature and shrinkage cracks that develop. These additional elements should prolong the life of the structure.
Bridge drainage features also are being updated.
"The deck joints have troughs to divert water away from the structural steel," said Kelly. "We will then consolidate the discharge and into water collection systems near the bridge. Ultimately, the repairs will make the bridge safer for the public and reduce future maintenance." CEG
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