Lift Station 7 handled approximately one-third of the City of Sarasota’s wastewater flow (9.5 mgd), but with a history of mechanical failures and overflows it was at the end of its useful life. The City entered into a Consent Order with FDEP to improve the level of service and reliability at the facility, and retained engineering and construction firms to design a replacement – Lift Station 87. Construction on the original project began in 2011; however, due to design and construction issues, the original project failed and the contract with the initial engineer was terminated.
The City then retained McKim & Creed to manage its $32-million program, evaluate the original design, propose design revisions, and develop a proactive public outreach program to regain the trust of the elected officials and the residents. The primary focus of Phase 1 was evaluation and design, and of Phase 2 was redesign and construction.
The results of our Phase 1 evaluation determined that the vertical alignment of the gravity main, as designed, could not be constructed. The invert elevation of the 36-inch main was lowered 8 feet to avoid interference with the existing bridge abutment and to minimize potential impacts to the environment during drilling. Phase 1 also included a review of the previous lift station design and recommendations to increase reliability, improve worker safety and minimize operational issues.
The first bid package included a new 36-inch gravity main to be installed under the Hudson Bayou, an environmentally sensitive waterway, using microtunneling construction techniques. The project also included construction of a new 24-inch water main under Hudson Bayou using HDD technology.
Phase 1 condition assessment and design services were completed in only five months to meet an aggressive consent order schedule. Traditional geotechnical borings and innovative geophysical investigations were performed to better define subsurface conditions underneath the Hudson Bayou and to determine as-built conditions of the historic Hudson Bayou Bridge, which was built in 1916. The lift station design was revised to “harden” the facility for Hurricane Category 3 storm surges.
Included in the plan was the installation of a 600kW, 480V, 3-phase standby generator for LS-87 designed to provide backup power to the entire lift station. The generator was installed on a second-floor mezzanine, to keep it protected in the event of storm surge. Securely bolted to the ground floor, the fuel tank will provide three days of run time at 100 percent of the generator’s capacity.
Phase 2 consisted of redesigning both the gravity collection system and other systems at the lift station. It also included permitting activities, construction phase activities and continuing public outreach. For construction, the City’s initial intent was to negotiate a change order with the original contractor and progress under a Construction Manager at-Risk model. However, when negotiations failed to present a reasonable change order, the original contractor was terminated, and McKim & Creed developed three bid packages based on the 30 percent designs, resulting in $2.5 million in savings for the City.
This project won a 2020 Award of Merit, Water / Environment Category, from Engineering News-Record Southeast.