Replacement of a Critical Water Supply Pipeline in a Dense Urban Landscape

Since its formation in 1951, the North Texas Municipal Water District (NTMWD) has been charged with developing a reliable water supply source for its 13 member cities and 60 other customers, serving more than 1.6 million people in portions of North Texas. NTMWD, like many large municipalities and water suppliers, increasingly relies on aging infrastructure to meet customer demands. Urban growth, development, and congestion are some of the major challenges in maintaining and replacing existing infrastructure in highly populated regions. In 2009, the NTMWD initiated a project to replace a critical existing 4-mile, 42-inch pipeline with a new 48-inch pipeline that supplies treated water to the NTMWD member cities of Richardson and Plano, Texas. The 35 year old existing water line had an increasing number of maintenance issues including pipe buckling, leaks, and other repairs in numerous locations. Since the 1970's, urban growth and build out had occurred in the area and created difficult challenges for replacing the existing pipeline. This paper will focus on the major design and coordination issues, construction management, and lessons learned during design and construction of the multi-million dollar project. Unique project design issues included multi-level coordination of road and utility infrastructure throughout the congested corridor, evaluation of roadway and traffic impacts to high capacity thoroughfares, repair and protection of landscaping and urban spaces per local ordinances, evaluation of alternate routes, and deep and extensive tunnel crossings of highways, major thoroughfares, and major creeks. Hydraulic and surge models were developed during design to confirm capacity and long term reliability for the new pipeline. Challenging construction issues included traffic control, sequencing and logistics for materials delivery and staging areas, and coordination with numerous landowners and businesses. Construction contract documents were specifically written to provide for an accelerated 10-month construction schedule in order to meet pipeline in-service requirements for Summer 2011. The construction phase required management of multiple installation crews in order to meet schedules and public expectations.