دانلود رایگان ترجمه مقاله قنات Tohickon (نشریه وایلی ۲۰۰۸)

قنات Tohickon

The Tohickon Aqueduct

I first became aware of the Tohickon Aqueduct project when contacted by William J. Collins, a landscape architect and timber framer from Point Pleasant, in Bucks County, Pennsylvania. We agreed to meet and discuss the proposed project at the annual meeting of the Timber Framers Guild of North America in Guelph, Ontario, in 1992. Bill Collins, a resident of Point Pleasant and a principal in the firm Simon Jaffe Collins Incorporated Landscape Architecture of Berwyn and Doylestown, Pennsylvania, had worked several years as project manager, landscape architect, and designer for the local sponsor, the Point Pleasant Community Association. The design concept he presented to me in Guelph was an aqueduct framed with Town lattice trusses, in keeping with the original 1834 construction.

The Delaware Canal was constructed in the early 1830s with the primary goal of transporting anthracite coal from northeastern Pennsylvania to cities on the eastern seaboard. The Tohickon Aqueduct is a vital link in the 60-mile-long Delaware Canal carrying the canal over Tohickon Creek in Point Pleasant, Pennsylvania. The canal climbs 164 feet between Bristol and Easton through a series of 23 locks, over nine aqueducts. The Tohickon Aqueduct, originally built as a timber-framed Town lattice truss structure was replaced in the 1890s with an iron riveted structure containing a wood- framed trunkway. This aqueduct collapsed in 1931. After World War II, the canal was transformed into a Pennsylvania state park and the aqueduct reconstructed with steel girders supporting a cast-inplace concrete trunkway. By 1990, the badly deteriorated concrete and steel structure needed to be replaced. As if to place an exclamation mark on the statement that the aqueduct needed to be replaced, a September 16, 1999, storm in Point Pleasant, caused a portion of the sidewall of the aqueduct to collapse.

Bill Collins was one of several community leaders who were very interested in replacing the aqueduct as a timber structure. The concept plans were presented at a meeting of community and elected officials and officials of the Pennsylvania Department of Conservation and Natural Resources, Bureau of Facilities Design and Construction. A unique agreement was reached, allowing the community to collaborate with the State Parks Department by providing engineering plans for the timber superstructure outside the normal procurement process.

Apparently, it was an easy agreement to broker, as the state would not have to pay for the engineering. Fortunately, there was an organization interested in having the Tohickon Aqueduct constructed of wood. The Wood in Transportation Program of the U.S. Department of Agriculture Forest Service came to the rescue, providing five small grants to successive phases of the project. The state would be responsible for administration of the project and design of the substructure and the interface of the trunkway with the canal. Initial funding for design of the superstructure was provided by U.S. Forest Service grants through the Wood in Transportation Program. Initial funding was minimal, so design proceeded slowly between 1992 and 1999. This was especially frustrating for the members of the Point Pleasant Community Association when I presented them with construction photographs of the New Covered Bridge in Old Salem, North Carolina, a similar project well underway, which had started at the same time. By contrast, the aqueduct project had gone nowhere.