Challenge: To conduct groundwater, soil, and surface water sampling and associated reporting needed to meet environmental permit requirements for operating this zero-discharge biosolids processing plant and help maintain the surrounding area as a mecca for bird watchers, anglers, river paddlers, and nature lovers in Central Texas.
Solution: Situated in a bend of the Lower Colorado River, the Hornsby facility was established in the 1950s to process biosolids produced by wastewater treatment in the City of Austin. Digested and dewatered biosolids have historically been land applied or composted onsite. Land application ceased in 2016. The thickening and dewatering sidestream liquids and stormwater are processed through an onsite wastewater treatment system, including a series of ponds, before either evaporating, being used to irrigate onsite hay fields, or being pumped back to the South Austin Regional Wastewater Treatment Plant (SAR) for additional treatment. The nutrient-rich ponds attract a wide diversity of resident and migrating birds—historically, more than 350 avian species have been documented on the plant property. When groundwater monitoring identified elevated ammonia concentrations in 2011, the Texas Commission on Environmental Quality (TCEQ) changed the monitoring frequency from bi-annual to quarterly. INTERA began providing groundwater monitoring, annual soil sampling, and annual reporting in 2023. The permit was renewed for another 5-year term in 2025, which included additional provisions to characterize redox conditions in the groundwater, to assess potential sources of ongoing elevated contaminants in groundwater (ammonia as nitrogen (NH3-N), nitrate as nitrogen (NO3‑N), arsenic, iron, and manganese), and to investigate potential impacts to surface water in the Lower Colorado River.
Results: INTERA has successfully implemented the groundwater, soil, and surface water monitoring program to ensure permit compliance. Our assessment of more than a decade of environmental data indicates that Austin Water’s ongoing efforts to reduce the volume of treated effluent going to the ponds, improve the quality of treated water, and create opportunities for alternate uses like irrigation, is lowering the concentrations and mobility of site contaminants. The property and surrounding area continue to serve as a sanctuary for migrating shorebirds, like the American White Pelican, warblers, and hawks, resident black-bellied whistling ducks and barred owls, coyotes, spiny softshell turtles, bumblebees, rattlesnakes, white-tailed deer, bobcats, and a host of other wildlife.
