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, whichwill retire two aging wastewater plants and consolidate treatment at the Northwest Regional Water ReclamationFacility (NWRWRF). The program will improve wastewater service in northwest Hillsborough County, improvereliability, and save money for all County customers. An initial step of this program involved retiring the DaleMabry Wastewater Treatment Plant (WWTP) and constructing a new pump station and six miles of 24 and 36-inchforce main to convey wastewater to the NWRWRF for treatment and a new 20 and 24-inch reclaimed water main toreturn 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 toan alignment that traversed a major 6-lane road with numerous intersections/business entrances and environmentalchallenges, the team had to carefully weigh trenchless versus open-cut installation along the route during their initialresponse to the design-build solicitation. The final approach incorporated 16 horizontal directional drills, many inclose proximity to each other within the road median to minimize traffic disruptions, provide separation fromexisting utilities including a 1,000-psi gas main, and to avoid impacts to bridge pilings, surface waters, and forestedwetlands.