A mile-long waterway tells tales of reshaping and renaming. The Boundary Channel. It is a channel off the Potomac River in Washington D.C. This channel marks the original Virginia shoreline. Boundary Channel separates Columbia Island from Virginia.
The story of Boundary Channel is intertwined with the history of Columbia Island. Columbia Island is partly natural and partly man-made. Around 1818, Analostan Island, now Theodore Roosevelt Island, was rocky. It sat close to the D.C. shoreline. Deforestation and agriculture upstream caused river erosion. The Potomac River’s northern bank eroded. The gap between Analostan Island and the shore widened. Silt deposits built up around Analostan Island. By 1838, Analostan nearly doubled in length southward. By 1884, the new southern part of Analostan Island was established. It supported a wetland. The river eroded the center of Analostan Island. This erosion severed Columbia Island from its parent body.
Between 1911 and 1922, the U.S. Army Corps of Engineers repeatedly dredged the Potomac River. The goal was to deepen the channel and alleviate flooding. Dredging widened the distance between Theodore Roosevelt Island and Columbia Island. This was to prevent flooding of the Virginia Channel. Dredged material was piled on Columbia Island. This helped to build it higher, lengthen, and broaden it. Columbia Island received its name around 1918. An unnamed engineer working for the District of Columbia chose the name.
An anonymous Corps of Engineers officer named the waterway between Columbia Island and Virginia the Boundary Channel. The Boundary Channel was further defined in the late 1920s. In 1925, Congress authorized the Arlington Memorial Bridge across the Potomac River. Preliminary designs showed the bridge ending on Columbia Island. This required additional expansion of the island. The Corps of Engineers planned to continue dredging the Potomac River and enlarge Columbia Island. Secretary of War John W. Weeks ordered the expenditure of $114500 on April 1 1925. The aim was to dredge the river between the Highway Bridge and the Lincoln Memorial. The dredged material was dumped on Columbia Island. By June 30 1927, dredging of the Potomac River and reshaping of Columbia Island was largely finished.
In 1936, Boundary Channel measured 100 to 200 feet in width. Its depth was 4 to 6 feet. No lagoon existed then. The Boundary Channel changed again after ground was broken for The Pentagon on September 11 1941. The Pentagon was built south of the Boundary Channel. The ground to the northwest, north, northeast, and east of the building site was low. The Corps of Engineers considered building a levee to protect it from floods. General Brehon B. Somervell decided to raise the ground. It was raised at least 8 feet to 18 feet above the average water level. Boundary Channel was dredged and widened to provide fill material.
Due to silting, the Boundary Channel is about 100 feet wide as of 2013. The width varies. It is also quite shallow.
Pentagon Lagoon is a shallow pool. It is part of the Boundary Channel. The lagoon was originally constructed as part of the channel. It was originally quite small and unnamed. During the Pentagon’s construction in 1941, the U.S. Army needed fill material. They also needed a way for barges to deliver materials to the construction site. The Corps of Engineers removed a portion of Columbia Island. They dredged the bottom of the lagoon for fill material. The Army built a dike inland on the Virginia shoreline. The earth behind the dike was excavated to 14 feet below the Potomac River’s average high tide. Cement plants and marshalling areas were built on the new shoreline. The dike was then breached. Barges delivered construction materials quickly. More than 1000000 cubic yards of earth were excavated. Boundary Channel’s lagoon enlarged by 30 acres. The Washington Post named the Pentagon Lagoon. This occurred after a murder there in September 1944.
Many bridges cross Boundary Channel. These include the George Washington Memorial Parkway and Arlington Boulevard. Boundary Channel has a rich history. It has been reshaped and redefined over time. It reflects the changing landscape of Washington D.C. and its surroundings.