Item 14 - Williamson Creek Wastewater Interceptor Project Presentation — original pdf

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Williamson Creek Wastewater Interceptor Project Kane Wei, P.E. Austin Water Supervising Engineer Water & Wastewater Commission January 14, 2026 Agenda Agenda  Project Overview  Routing Requirements  Neighborhood Partnership  Parks and Recreation Partnership  Watershed Protection Partnership  Summary 2 Project Overview 18,800+ linear feet of 72-inch diameter gravity wastewater interceptor installed using a two-pass tunneling method Project drivers:  increase capacity  replace aging infrastructure  reduce the potential for future sanitary sewer overflows to protect the environment 3 Existing Interceptor Requires Replacement  Built in the early 1960’s – size, age, location, and condition of the existing pipelines make it susceptible to infiltration during rain events, which may result in overflows  No existing odor control along interceptor 4 Major Project Components  Excavation of 18,800 LF of tunnel, ranging from 20 to 90 ft below grade, entirely outside of the Erosion Hazard Zone.  Installation of 18,600 LF of 72-inch and 200 LF of 84-inch corrosion resistant fiberglass pipe with grouted annulus.  6 Operations and Maintenance (O&M) Shafts.  11 connection shafts for connections with the new tunnel  All shafts are made of corrosion resistant fiberglass or polymer concrete materials 5 Project Benefits  Installation of 22 local pipeline reconnections via open cut (5,400 LF of 8” to 48”) and jack and bore (2,500 LF of 12” to 54”) construction methods  Removal and abandonment of existing wastewater pipelines and manholes in the creek.  New biological odor control facility and associated rain gardens designed for potential future trailhead parking lot.  Cured-in-Place (CIPP) pipeline rehabilitation of 2,700 LF of existing 36” diameter concrete pipe.  Extensive environmental site restoration (native seeding, tree plantings, etc). 6 Why was this route selected?  18 different alignments evaluated via scoring matrix  22 environmental constraints considered 7 7 8 Neighborhood Partnership: Community Benefits  In 2017 and 2024 - Community Open Houses in Districts 2 and 3  Increasing parkland and future trails  Coordinated with nearby public projects (storm improvements, trails, etc).  Additional public meetings in 2026+ 9 Parks and Recreation Partnership: Expanding Greenbelt and Trails Access  1 acre of acquired sidewalk, trail, and recreation easements  3 acres of acquired properties necessary for temporary workspace areas, to be transferred after construction is completed  Transfer of up to 59.6 acres for future trailhead access near Jimmy Clay Golf Course  Total: over 63 acres of additional parkland, approved through Parks Board 10 Parks and Recreation Partnership: Odor Control and Trailhead Access  Odor control facility to reduce odors  Rain gardens were oversized to accommodate future potential trail head parking and access  Concrete paved access instead of gravel 11 Watershed Protection Partnership: Creek Restoration  Proper abandonment and removal of pipe and manholes in the creek  Each location individually evaluated with Watershed Protection for the least environmental impact and most creek stabilization 12 Watershed Protection Partnership: Flood Reduction  Removal of abandoned structure and “hill” to lower the bed of the creek to match its surrounds  Increases conveyance ability and reduces flood risk of Williamson Creek  Approved through both Planning Commission and Environmental Commission 13 Watershed Protection Partnership: Environmental Mats for Temporary Access  Laid down with minimal disturbance to the underlying soil, then picked up with less mitigation required. Used where feasible.  Incorporated via feedback from community 14 Where are we now?  2016 to 2019 – Preliminary Engineering Phase  2019 to 2023 – Detailed Design Phase  2023 to 2025 – Permitting and Easement Acquisition  September 18, 2024 – Environmental Commission  November 25, 2024 – Parks and Recreation Board  May 13, 2025 – Planning Commission  2025 – Advertisement  January 14, 2026 – Water and Wastewater Commission  January 22, 2026 – Council Meeting  2026 to 2031 – Construction Phase 15 Project Website  www.austintexas.gov/wci  Project details, maps, exhibits  Past presentations  Sign up for email updates 16 Building Austin’s water future, together. Water & Wastewater Commission January 14, 2026