River Gone Wild: Protecting a Large-Diameter Transmission Main from the River, Dallas, Texas

A 72-in. water transmission main was installed in the early 1960s to provide water to the southeastern portion of the City of Dallas Water Utilities (DWU) service area. This prestressed concrete cylinder pipe (PCCP) was at risk of being exposed by the Trinity River due to river bank erosion, compromising its integrity. Several options were evaluated to protect the pipeline and also to minimize the impact to the surrounding area. The options varied from pipe relocation to bank stabilization. An electromagnetic (EM) inspection was performed and only six joint locations were found to be distressed indicating the line was in good condition, making the pipe replacement option less desirable. Using the results of an investigation of soils in the area, cost analysis, EM results, and long-term client interests, bank stabilization in the form of rock anchors and gabions was ultimately recommended. This cost-effective approach was estimated to save, more than $13 million in construction costs as compared with replacement of the pipeline. This paper discusses the alternatives evaluation, design phase, required permitting with the U.S. Army Corps of Engineers, and the risks associated with the construction phase on the banks of a major waterway.