The City of Austin is seeking to reduce the risk of riverine flooding and storms to the health and safety of the 628,512 residents in the project service area.
This project would protect two of Austin’s critical infrastructure facilities from future flood damage through roadway improvements and streambank stabilization activities. Fallwell Lane is the primary access route to the existing South Austin Regional (SAR) Wastewater Treatment Plant (WWTP) as well as the Austin Energy Sand Hill Energy Center (SHEC) electric generating and distributing facilities. Together, they represent over $700 million dollars of infrastructure investment. Based on their experience in previous flood events, the facilities risk losing access, flood damage, and bank erosion that could cause catastrophic service interruptions. These interruptions — including loss of electric power — would likely result in uncontrolled raw sewage discharge from the WWTP, sewer collection system backups, loss of climate control in residents’ homes, and sewage flooding into residents’ homes.
2015 Flood Event over Fallwell Lane
It has been estimated that a single catastrophic flood event at the facilities could cause losses of over $1.6 billion at the site. An extended outage could severely hamper Austin’s recovery after a flood and risk neutralizing the many resilience measures that Austin has implemented through a variety of community plans. Under flood conditions, both plants would be inoperable and unable to generate electricity or treat wastewater. SAR represents half the wastewater treatment plant capacity of the City of Austin, and SHEC represents 23% of the base load power capacity.
The City of Austin has previously contracted with a wide variety of professional service firms including engineering, environmental, geotechnical, and mapping providers to investigate solutions for the project area. The City evaluated holistic alternative infrastructure improvements for Fallwell Lane and adjacent facilities. The result of that study was a Preliminary Engineering Report (PER) that forms the basis of much of this narrative and resulted in $8.8 million of CDBG-MIT grant funding. The components included in the scope of work consist of:
- Reconstructing Fallwell Lane at-grade, with a portion of the roadway off-set from the Colorado River bank to reduce flood risk;
- Realignment of water utilities within the right of way of the off-set roadway;
- Implementation of “soft” streambank restoration techniques where topography and adjacent infrastructure allows;
- Implementation of hard streambank stabilization to protect the Austin Energy Onion Creek Substation and Fallwell Lane; and
- Improvements to the Austin Energy SHEC drainage outfalls to minimize future erosion.
With a probable cost of $22.6 million, the selected project elements and roadway alignment will provide the maximum benefit to the stakeholders based on stakeholder defined parameters, while minimizing environmental impacts. The remaining funding will come from predominantly local sources.
Fallwell Lane Failure