City of Pflugerville Carmel/Sorento Lift Station & Force Main
Meeting an Accelerated Schedule to Serve Development in Pflugerville’s Wilbarger Creek Basin
Due to imminent development in the Wilbarger Creek basin, the City of Pflugerville needed to provide wastewater service to the basin. Since the City operates one major wastewater treatment plant in a different drainage basin, the wastewater flow in the Wilbarger basin either needed to be pumped to the existing treatment plant, or a new wastewater treatment plant would have to be constructed in the Wilbarger basin.
During its recent Wastewater Master Plan update, the City opted to construct a new lift station, known as the Carmel/Sorento Lift Station and Force Main (CSLS), which would allow the City to delay construction of the future wastewater treatment plant for 20 years. The CSLS was designed to receive wastewater flows from two gravity-controlled interceptors (Sorento Interceptor Phase 1 and Carmel Interceptor Phase 1) as shown in the Wastewater Master Plan. These two interceptors have been completed and are in service. The lift station pumps deliver wastewater flows through a new force main to an existing 24-inch force main located in Weiss Lane.
The City of Pflugerville retained KFA to design and construct the CSLS to provide wastewater collection facilities for two proposed subdivisions in the City of Pflugerville’s extraterritorial jurisdiction (ETJ). KFA provided preliminary engineering, final design, and bid and construction phase services. Major tasks included: lift station site selection, force main alignment analysis, wet well and pump sizing and phasing, force main sizing, permitting for the project, construction plans and specifications, and construction administration.
- Preliminary Engineering: This project included a significant effort towards site selection. As the site location was not previously identified, KFA reviewed landowner records, topographic maps, floodplain maps, and other materials to identify possible candidate sites. Considerations such as access to roads, availability of electrical and water utilities, force main length, and permitting requirements were tabulated and reviewed with the City to determine the most beneficial site location. Preliminary engineering also included using the City’s Future Land Use Map and information from developers to project flows for the lift station to size and phase the facilities. Several routes were evaluated for access to the lift station and routing of the force main. Selected to facilitate land acquisition and constructability, the final route is more than 9,000 feet long. Through hydraulic modeling, KFA determined that no improvements to the existing Weiss Lane Lift Station were required for the existing Weiss Lane Force Main to be used for both lift stations.
- Final Design: The CSLS consists of a wet well, submersible pumps, monorail crane, electrical building, emergency generator, and associated appurtenances. The CSLS is designed for an ultimate firm capacity of 6,000 gallons per minute. KFA designed the CSLS in accordance with City of Pflugerville Design Standards and included alternative force main piping materials in the bid documents to ensure the City received the best project pricing.
- Bid & Construction Phase Services: The bid documents included alternative force main piping materials (HDPE and ductile iron) to ensure the City received the best project pricing. The Contractor selected HDPE pipe in order to accelerate construction of this cross-country pipeline. The force main and access drive were packaged as one project and bid separately from the lift station. KFA provided the bid evaluation and recommendation, submittal and RFI reviews, periodic site visits, ran the progress meetings throughout construction, and coordinated project close-out for both construction projects. Paving of the access road was added to an adjacent project during construction.
The project was completed in 2016 to meet the accelerated schedule. Without the deduction of access road paving and Owner-initiated additions such as trees, the lift station was completed with 0.7% change orders and the force main and access road with 0.4% change orders. The CSLS now conveys wastewater flows in the Wilbarger Basin to the Central Wastewater Treatment Plant for treatment.