Trenchless Technology

OCT 2018

Trenchless Technology is the premier communications vehicle for the trenchless industry. Through our multiple platforms, readers receive insights into the trenchless industry, as well as keep connected to the latest news, products and projects.

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W W W.T R E N C H L E S S T EC H N O LO GY.C O M 27 all excavation had to be witnessed by an archeologist to inspect for items of historic interest. The west side of Rock Creek Park is bordered by Oregon Avenue, within the Chevy Chase and Barnaby Woods neighborhoods of Washington D.C., where the second half of the tunnel would be built. An active residential community had signi•icant concerns about how the project would restrict travel around their homes and the impacts of a construction project like this in their front yards. These conditions led to limited access from which to build a tunnel with the only available staging area at the intersection between the two halves of the job. The three tunnels designed along Oregon Avenue were combined into a single 1,860-ft long tunnel drive using 60-in. diameter steel casing behind a microtunnel boring machine (MTBM), the longest at the time in the United States through rock. Given the length and soil conditions, special considerations had to be made for every utility used in the tunnel - ing operations. Also, the southbound lane of Oregon Avenue had to remain open for traf•ic and emergency servic- es, therefore shafts had to be narrow enough to •it in the northbound lane and a narrow strip between the edge of pavement and the Rock Creek bound- ary. Three elliptical liner plate shafts were used to achieve the depths re- quired, up to 50 ft, and avoid existing utilities that may have been damaged by pile installations. While most of the Bingham Drive section was to be installed by open cut, access had to be maintained from the same, congested project staging area. The tight curvature of the of the street itself had originally required three short, straight tunnels to navigate it. An S-curve tunnel eliminated these two intermediate shafts that would have severely hampered access to the project site The two 625-ft radius curves in op- posite directions maintained the tun- nel alignment along the Bingham Drive footprint within the National Park Service right of way. It also tested both the 48-in. RCP used as a casing and the MTBM. Project Owner: District of Columbia Water and Sewer Authority (DC Water) Engineer: Johnson, Mirmiran & Thompson Contractor: Bradshaw Construction Corp. Manufacturers/Suppliers: Herrenknecht, Permalok, Vianini, Jennmar, VMT and Jackcontrol Value of Trenchless Project (US$) $16,824,115

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