Title: Bridging the Gap: Galveston Causeway 8,500 LF Aerial Water Line
Abstract: The city of Galveston is located on an island and receives potable water from the mainland through two pipelines supported on the railroad causeway. Years ago, issues with the existing lines prompted the city to look for alternatives for an additional water pipeline to add reliability and redundancy to their water supply system. This third water supply line will allow the city to rehabilitate the existing lines, one of which is over 100 years old, without compromising the city’s water supply. When the new Galveston Causeway Bridge was built in 2003, the city partnered with the Texas Department of Transportation (TxDOT) to provide the bridge with structural capacity to support the water line even though it would be built later. This allowed the city to save tens of millions of dollars on a very deep tunnel beneath the Intracoastal Waterway. Now that the city has decided to move forward with the design and construction of the water line, a few updates had to be made to the design concept. Due to a change in the American Association of State and Highway Transportation Officials (AASHTO) bridge design codes, only a portion of the hanger bolts left in the bridge could be utilized. Several innovative design alternatives were developed to support the pipe from the bridge in other ways and ultimately an alternative to span the pipe from bridge bent to bridge bent was selected. To accomplish this, each bridge bent on the approach sections will be extended to support the pipe and the pipe thickness will be increased to provide the strength necessary to make the 134-foot span between the bents. While the change in the AASHTO codes necessitated the design concept change on the approach sections of the bridge, it did not have the same impact to the center span of the bridge over the Intracoastal Waterway. In this section, a finite element analysis (FEA) model was prepared to determine the capacity of the bridge to support the pipe from the existing hanger bolts. The model determined that the bridge has capacity and a concept like the original concept could be implemented. There are many stakeholders for this project, including the United States Army Corps of Engineers (USACE), Gulf Coast Water Authority (GCWA), United States Coast Guard (USCG), and TxDOT. Each of these parties were coordinated with to achieve the goal of increasing the redundancy and reliability of the city of Galveston’s water supply. The project is nearing completion of final design pending final approval from TxDOT. This paper will focus on the design and planning considerations one would need to consider when designing an aerial pipeline, particularly an aerial pipeline supported by an existing structure. With good planning and proper design, aerial pipelines can save cities significant amounts of money.
Publication Year: 2019
Publication Date: 2019-07-18
Language: en
Type: article
Indexed In: ['crossref']
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