August 2012 » Departments

Concrete aqueduct provides a century of service
A rare structural evaluation performed on a concrete stormwater outfall in Salt Lake City recently found that a pipeline constructed in 1910 was still functioning well and was not in need of replacement. The long-term viability of the City Creek Aqueduct was only at issue because of planned construction of a light rail transit line running closely parallel to or above the pipeline. The 84-inch-diameter, cast-in-place concrete pipeline was initially constructed by Davis and Heuser in 1910, which submitted the low bid of $48,252 – roughly $14.50 per foot – for 3,300 feet of 7-inch-thick reinforced concrete.

Since precast concrete pipe was not available then, the pipeline was cast using an outer frame of round wood staves, with an inner frame of four removable quarter-sections. Historical photographs and newspaper articles showed that excavation and construction was performed with hand laborers and little mechanical help. Yet, the contractor was able to work at a record pace, constructing as much as 140 feet of pipeline in a day.

A condition assessment and structural analysis of the 100-year-old pipeline found that portions of the pipeline looked brand new, while other sections had experienced spalling or reinforcing corrosion. Scour from the constant flow of water also was seen in some sections.

Historical photograph shows workers preparing forms for the 84-inch-diameter, cast-in-place concrete pipeline.
Photo: Used by permission, Utah State Historical Society, all rights reserved.

Find this web-exclusive article with the August 2012 issue of CE News at www.cenews.com

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