Austin Water Utility Wastewater Treatment Plants Flood Preparedness, Management, and Response

Austin Water Utility (AWU) operates two large wastewater treatment plants (WWTP), namely Walnut Creek Wastewater Treatment Plant (Walnut Creek) and South Austin Regional Wastewater Treatment Plant (SAR). Both WWTPs are permitted to treat annual average flows of 75 million gallons per day (MGD) each, and discharge their treated effluent into the Colorado River. AWU also operates several small WWTPs, including the 0.345 MGD Onion Creek Water Reclamation Plant (WRP). This plant sits near Onion Creek which feeds into the Colorado River upstream of SAR. The plant’s effluent is used to irrigate a golf course adjacent to the plant site.The Austin region is subject to frequent flash floods. All three plants had experienced prior flooding with significant impact to the facilities infrastructure and wastewater treatment operations. Consequently, in the last decade, AWU implemented flood preparedness measures at Walnut Creek and SAR, including operational modifications, structural improvements and plant expansion. The principal aim was to be better prepared to respond to flash flood events. The Onion Creek WWTP was deemed at risk but no significant improvements were made.In October 2013, the Austin area received heavy rainfall on two occasions and both events created flash floods in many parts of the city. Walnut Creek was able to manage the flood to maintain facility operation and to protect the Colorado River waters. On the other hand, although SAR similarly had prepared for such event, it was unable to manage the flood because it completely lost its power supply. As further assessment indicated, a single electrical substation, the Onion Creek Substation, owned and operated by Austin Energy (AE) was providing power to the plant. The substation was flooded and lost power. For three days, SAR was discharging essentially untreated water until AE and AWU restored power to the plant. Onion Creek was completely flooded and was considered a total loss. This paper discusses the flood preparedness, impacts of the flood and the lessons learned at each of the three plants.