Supplemental Monitoring of Selected Water Bodies with Contact Recreation Impairments

Nutrient and indicator bacteria data were collected at seven sites in five Austin creeks that are on the draft 2010 Clean Water Act section 303(d) list of impaired water bodies proposed by the TCEQ. The supplemental data was collected to verify the TCEQ assessment that the creeks are not supporting designated uses of primary contact recreation in the Texas Surface Water Quality Standards due to elevated bacteria levels (30 TAC 307.7(b)(1)(A)(i)). These streams may also be “of concern” under Clean Water Act section 305(b) due to nutrient enrichment. Flow monitoring indicated that Eanes Creek below the Barton Springs Edwards Aquifer recharge zone is ephemeral; therefore, the bacteria impairment for this site is not appropriate according to TCEQ assessment methodology. Bacteria levels are low enough at the Westlake-Davenport Tributary site to fully support primary contact recreation uses. Primary contact recreation is not supported at the Waller Creek, Taylor Slough South or Spicewood Tributary to Shoal Creek sites. Elevated nutrients at Waller Creek appear to be from and indeterminate source of sewage contamination and those at Westlake-Davenport are most likely from nearby residential fertilizer application.