Nassau County Pump Station Flood Mitigation
Greeley and Hansen, A TYLin Company, upgraded and provided flood hardened four of Nassau County’s sanitary pump stations as part of their $800M flood mitigation program.
The Nassau County flood mitigation program was funded by FEMA to flood harden the sanitary pump stations and the Bay Park Sewage Treatment Plant. The upgrade of the sanitary pump stations included detail design services and design services during construction to inspect each of the four pump stations, assess any damages, design replacement of equipment, review the facility for code compliance and upgrade it for safety, and flood harden the facility to the 500-year design flood elevation to prevent shutdown of the facility during future major storms like Super Storm Sandy.
The four pump stations were damaged during Super Storm Sandy and were upgraded to avoid future storm damage. These pump stations convey wastewater to Bay Park Sewage Treatment Plant. These stations are generally located within residential neighborhoods. All the equipment in these pump stations were last upgraded in 1990’s and are over 20 years old. Under this project aging pumping equipment, at risk, or damaged equipment was replaced with submersible rated equipment. Critical electrical equipment will be raised above the 500-year flood level. In addition, the pump stations were flood hardened to withstand the forces from a 500-year flood elevation and prevent water from entering the station. Our approach to flood harden the facility included protecting the pump stations from water entering the station, keeping the dry well physically separated from the wet well and all penetrations sealed to prevent water rising from within the station submerging the critical equipment required to maintain the operation of the station during storm events, raising the critical electrical equipment where possible above the 500-year still water level, providing sump pumps to keep up with potential small leaks into the dry well and providing equipment suitable to operate in submerged conditions.
Some of the challenges faced under this project to flood harden the existing pump stations included maintaining the pump station in operation during the upgrade. To flood harden the walls to the 500-year flood elevation, the walls required to be stiffened to withstand the new anticipated loads. However, the existing walls have various electrical equipment mounted on them that could not be disturbed for the station to remain in service at all times. Therefore, we developed an alternate
approach to stiffen the walls by building a concrete wall with a new brick facade on the exterior while maintaining the existing structure intact. Louvers were raised above the 500-year flood elevation and new watertight doors were designed to prevent water from entering the station.
Project Highlights:
- Climate resilient design
- Facility flood proofing
- Maintenance of service throughout construction of the improvements