City of Austin - Northwest Area Lift Station Improvement Program Streamlining Regional Wastewater Collection Systems and Improving Flow Conveyance with Strategic Long-Term Planning

Summary: The City of Austin hired K Friese & Associates (KFA) to optimize the Northwest Area regional collection system by redistributing flows among four lift stations. This effort involved expanding two lift stations, rerouting and reversing force mains, and decommissioning one lift station. Abstract: Austin Water operates 143 lift stations and 2,927 miles of wastewater pipelines. In 2018, the City of Austin selected KFA to modernize the Northwest Area's lift station network through the 'Rock Harbour Area Improvements' project. This included flow conveyance upgrades between the Boulder Lane (BL), Rock Harbour (RH), Four Points #1 (FP #1), and Four Points #2 (FP #2) lift stations. The project addressed increasing flows at BL and RH stations, planned service area growth, and outdated infrastructure. It also reduced inefficiencies by decommissioning FP #2 and reconfiguring the force mains. Initially, FP #1 and FP #2 were oversized due to early planning assumptions of high-density development. However, environmental constraints like the establishment of the Balcones Canyonlands Preserve led to limited growth. Meanwhile, flows to RH and BL increased, necessitating system improvements. Previously, BL flows were pumped to RH, which received additional gravity flows from its service area before discharging to FP #2 via FP #1. This overly complex flow pattern contributed to inefficiencies. The improvements streamlined this system by expanding BL and RH lift stations, bypassing FP #2, and rerouting and reversing flows. These upgrades were implemented in phases, each designed with future projects in mind. The RH station was first expanded with pumps capable of handling interim flows and later adapted for increased capacity using a larger-diameter force main. Subsequent projects included rerouting the RH force main (RH FM), reversing an existing force main to accommodate FP #1 flows, and decommissioning FP #2. BL station upgrades were completed independently, ensuring compatibility with increased flows downstream. Key Improvements: 1. Expansion of RH lift station. 2. Construction of a new 18' RH FM to bypass FP #2. 3. Connection of FP #1 to the reversed 12' RH FM. 4. Decommissioning FP #2. 5. Expansion of BL lift station. Project Execution: The design and construction of the projects required detailed sequencing to minimize operational disruptions and construction complexities. The RH FM reroute involved three interdependent designs: the new 18' FM to bypass FP #2, reversal of the existing 12' RH FM, and rerouted connections to FP #1. The RH lift station was expanded to accommodate these changes, with its design incorporating flexibility for future system curves. To decommission FP #2, FP #1 flows were redirected via the reversed 12' RH FM to the expanded RH lift station. Pre-design efforts ensured seamless integration of phased improvements while maintaining system functionality. Coordination between these interconnected projects was essential to avoid service disruptions and optimize efficiency. Challenges and Solutions: Several challenges emerged during the planning and execution phases, offering critical lessons: 1. Strategic Foresight: Early planning ensured the initial projects could accommodate subsequent improvements. This minimized costs and disruptions while simplifying future construction. 2. Phased Execution: Careful sequencing of the RH FM reroute project (comprising three of the five improvements) ensured prerequisite components were in place before proceeding with later phases. 3. Staffing Continuity: Staffing transitions posed risks to institutional knowledge. KFA retained the same project manager and lead engineer throughout the program, ensuring consistency. A diverse client team from Austin Water (AW), Development Services Department (DSD), and others supported continuity despite turnover. 4. Site Constraints: Limited workspace at the RH and BL stations required innovative approaches, such as phased construction, unique storage solutions, and close coordination with facility operators. 5. Infrastructure Retrofitting: Existing infrastructure was repurposed to reduce costs and timelines but introduced uncertainties due to unknown underground conditions. Record drawings and coordination with city operators helped mitigate risks. 6. Material Delays: Extended lead times for equipment like generators disrupted schedules. Lessons from the RH station informed bid evaluations for BL, including pre-purchasing and timeline adjustments. Early engagement with suppliers proved essential. Lessons Learned: The iterative nature of the project allowed the team to address issues proactively in later phases. Design refinements incorporated feedback from earlier projects, addressing material changes, site access, and installation challenges. The project also highlighted the importance of anticipating supply chain disruptions and planning buffer periods to accommodate delays. Conclusion: The integrated improvements program streamlined flow conveyance in Austin's Northwest Area, addressing current inefficiencies and planning for future growth. The project involved lift station expansions, force main rerouting, flow reversal, and decommissioning outdated infrastructure. Key achievements included strategic planning, phased execution, and adaptive design. These efforts reduced costs, improved system reliability, and provided valuable insights for managing complex wastewater improvement programs. The approach exemplifies innovative, sustainable infrastructure solutions that balance operational needs, environmental constraints, and long-term development.