The Dale Mabry Diversion Pipelines project was the first of four successive, design-build projects included in Hillsborough County’s $250-million wastewater consolidation program. It was critical for the Dale Mabry project to be completed on time prior to the construction of the new 10-MGD Dale Mabry Diversion PS to the newly expanded NWRWRF in an effort to protect the program’s overall schedule.
McKim & Creed served as the engineer of record for the design and construction oversight of over 67,200 LF of 24-inch to 36-inch wastewater force mains and a 20-inch reclaimed water main. The project’s aggressive schedule included 24 months for design, permitting, construction, and commissioning of over 12 miles of large-diameter force mains and reclaimed water mains.
The project included the installation of large-diameter utility mains in a congested, multilane roadway corridor. Environmental challenges included multiple crossings of wetlands and surface waters. A risk register was developed to identify and address these and other challenges during planning, permitting and design to protect the project’s schedule during construction. Project risks included permitting, design, construction, and community impact issues.
The final approach included 16 horizontal directional drills (HDDs) totaling approximately 17,400 LF of 20-36″ diameter pipeline, 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 avoid impacts to surface waters and forested wetlands. Permitting, design, and construction required coordination with diverse stakeholders, including regulatory agencies, community groups, and franchise utilities.
The $25.9-million design-build project was completed on-time, within budget, and with minimal community disruption. This was achieved through proactive and creative risk management, community outreach, and construction management practices.