2011  ·  Wastewater

Land-­Applied Wastewater Effluent Impacts on the Edwards Aquifer

D. Lauren Ross, Ph. D., P. E. Glenrose Engineering, Inc, Greater Edwards Aquifer Authority, Save Our Springs Alliance

This report examines existing evidence that wastewater effluent discharged in the Barton Springs and San Antonio Edwards Aquifer contributing zones under Texas Land Application Permits (TLAPs), issued by the Texas Commission on Environmental Quality, have failed to protect springs, creeks, rivers, and groundwater. Significant findings of the study include:

    • The total TLAP-permitted daily flow in the Barton Springs Edwards Aquifer contributing zone is 5.75 million gallons per day, compared with only 3.18 million gallons per day in the San Antonio Edwards contributing zone. On a per acre basis, the permitted effluent in the Barton Springs Edwards Aquifer contributing zone is 24 times the amount in the San Antonio Edwards Aquifer contributing zone.
    • Across the Barton Springs and San Antonio Edwards Aquifer recharge zones from Austin to Brackettville, there are currently no TLAPs. A recently proposed TLAP system over the Barton Springs Edwards Aquifer recharge zone presents a significant new threat to aquifer water quality.
    • TLAPs are wildly inconsistent in terms of requirements for wastewater treatment, offline
      effluent storage volume, irrigation area size, or downgradient monitoring. The result of these inconsistencies is widely different levels of protection for downgradient springs, streams, rivers, and wells.
    • Sparsely available monitoring data from streams and/or springs downstream from TLAPs
      indicate significant degradation of the high quality water that would naturally occur at those locations.
    • Regulations governing TLAPs should be overhauled to provide a consistent and high level of water quality protection across the Edwards Aquifer.

In the context of the thin soils, numerous springs, and delicately sensitive Texas Hill Country streams, rivers, and aquifers, any wastewater effluent system represents the threat of permanent and significant degradation. Only by soundly based and strictly enforced regulations can we balance provision of wastewater infrastructure to suburban residences with protection of the natural streams and springs that draw people to these areas.