Transmission Pipeline Route Analysis to Support Growing Water Demand

In early 2016, Freese and Nichols Inc. (FNI) was contracted by the North Texas Municipal Water District (NTMWD) to develop a pipeline alignment for an 84-inch treated water pipeline to support the future growth projections expected in the northern reaches of their treated water system. The NTMWD currently serves more than 1.6 million people. The project is named the Leonard to McKinney Treated Water Pipeline, and this paper will present the preliminary design aspects of corridor and alignment selection analysis. The Leonard to McKinney Treated Water Pipeline (TWPL) is approximately 25 miles in length and proposed as an 84-inch pipeline with the potential for a future parallel 60-inch pipeline. The line begins at the proposed Leonard Water Treatment Plant (LWTP) near the city of Leonard, Texas, and travels southwesterly to the proposed McKinney Pump Station No. 4 delivery point in McKinney, Texas. The pipeline is expected to convey 90 MGD initially with an ultimate system capacity of 360 MGD. This pipeline is critical to meet the rapid growth the northern Dallas metroplex is experiencing. The paper will present an overview of the route analysis that was provided, beginning with a corridor analysis where a total of six, quarter-mile wide corridors were developed before narrowing those down to one preferred corridor, and finally working toward one final preferred pipeline alignment. The goal of the paper and presentation will be to focus on the reasoning and methods utilized for the careful selection of the optimal pipeline route. Special consideration was provided for various aspects to minimize known potential environmental and archeological impacts, potential impact to landowners, constructability concerns, topographic characteristics that would negatively impact hydraulic profile, and maximizing proposed permanent easement limits for future maintenance/construction needs. The preliminary routes were broken up by length into geographical classifications that represent specific construction challenges and associated costs. An evaluation matrix was developed utilizing geographical, cost, environmental, maintenance, and installation characteristics to classify sections of the routes as a means of comparing the alternatives. Using these reasoning tools, the analysis able to provide the NTMWD with an optimal pipeline route to carry into final design.