Eagles, Prairie Dogs, and Jumping Mice: Oh My! Installing a Large Diameter Pipeline within Sensitive Environmental Areas

Large diameter transmission pipelines are critical infrastructure that, within more arid areas of the country, must traverse long distances to bring water to the communities that need it. As the state of Colorado continues to grow and develop, the open and rural spaces between population centers tend to have more critical wildlife habitat and environmental protections. While these rural areas can be prime pipeline corridors, consideration, and planning is necessary to successfully construct a pipeline when endangered species and environmentally sensitive areas cannot be avoided. Northern Colorado Water Conservancy District (Northern Water) is building the Southern Water Supply Project II (SWSPII)—a large-diameter raw water regional pipeline project over 20 mi in length through Larimer and Boulder Counties in Colorado. The 36-in diameter steel pipeline will provide raw water to four (4) different public entities. Routed through multiple endangered species habitats, protected prairie dog colony land, and other protected raptor species nesting zones, this project has unique design, permitting, and construction challenges. During the design phase of the project, an inventory of all wildlife impacts and associated schedule constraints was developed. Multiple raptor surveys, Preble’s Meadow Jumping Mouse habitat surveys, wetland delineations, and prairie dog counts were completed. Different raptor, wetland, and prairie dog protocols for the four (4) different jurisdictions in the pipeline’s path were evaluated and documented. In addition to wildlife schedule constraints, a variety of farming and irrigated land impacts and schedule limitations were prevalent on the project. A detailed list of all these constraints were provided to the contractor during the bid phase of the project. As construction on the project began in Summer 2018, it was clear the project could not proceed in a linear fashion from one end to the other. Timing the work with the variety of constraints and timelines, as well as bird nesting changes, proved very challenging. This paper will describe the challenges, construction approach, and lessons learned to both plan and construct large diameter pipelines in environmentally sensitive areas with detailed schedule constraints. Some elements to be discussed include the following: allowing time for all construction activities, testing, and contingencies; best practices for minimizing impacts in wetlands; expediting construction when needed; and getting Contractor buy-in on schedule.