Hillsborough County Dale Mabry Diversion Force Main and Reclaimed Water Transmission Main Design-Build Project Horizontal Directional Drill vs Open Cut Strategy

摘要

The Dale Mabry Diversion project is part of the Northwest Hillsborough Wastewater Consolidation Program, which will retire two aging wastewater plants and consolidate treatment at the Northwest Regional Water Reclamation Facility (NWRWRF). The program will improve wastewater service in northwest Hillsborough County, improve reliability, and save money for all County customers. An initial step of this program involved retiring the Dale Mabry Wastewater Treatment Plant (WWTP) and constructing a new pump station and six miles of 24 and 36-inch force main to convey wastewater to the NWRWRF for treatment and a new 20 and 24-inch reclaimed water main to return reclaimed water to the Dale Mabry service area. Westra Construction and their design partner, McKim & Creed, were contracted to design, permit, and construct the project utilizing a Design-build approach in 2015. Due to an alignment that traversed a major 6-lane road with numerous intersections/business entrances and environmental challenges, the team had to carefully weigh trenchless versus open-cut installation along the route during their initial response to the design-build solicitation. The final approach incorporated 16 horizontal directional drills, many in close proximity to each other within the road median to minimize traffic disruptions, provide separation from existing utilities including a 1,000-psi gas main, and to avoid impacts to bridge pilings, surface waters, and forested wetlands.