Carters Creek (Segment 1209C) and Burton Creek (Segment 1209L) are located in central Brazos County and are tributaries of the Navasota River. The contributing watersheds cover roughly 36,000 acres throughout the Southern Post Oak Savanna ecoregion. Land uses in these watersheds differ in that the Burton Creek watershed is totally urbanized while Carters Creek is roughly 50 percent urban and 50 percent rural. Urbanization has impacted water quality and quantity in each of these watersheds by altering their hydrologic cycle. Impervious cover (parking lots, roofs, etc.) associated with urbanization limits infiltration into the soil and leads to increases in stormwater runoff. Baseflow levels are also augmented through wastewater treatment plant effluent and in some cases smaller streams are almost totally comprised of these inputs during the drier months of the year.
Both of these creeks are currently listed as impaired water bodies on the 2010 Texas Water Quality Inventory and 303(d) List published by the Texas Commission on Environmental Quality (TCEQ). Burton Creek has been on the list since 2006, and Carters Creek has been represented there in every report since 1999. Water quality monitoring indicates that these water bodies are not meeting their designated contact recreation use standards due to elevated levels of E. coli bacteria. Elevated amounts of the monitored, non-pathogenic strain of E. coli in a water body may signify an increased risk for disease-causing pathogens to be present and effectively limit the safe use of a water body for contact recreation. Both E. coli and other pathogenic organisms that may be present in Carters and Burton Creeks and are likely derived from the fecal material of birds and mammals.
In response to these impairments, a total maximum daily load (TMDL), or in simpler terms, a pollutant budget was developed by the Texas Institute for Applied Environmental Research. This work broadly identified potential sources of E. coli in the watershed. Concurrently, the Texas Water Resources Institute (TWRI) worked with local watershed stakeholders to develop a TMDL Implementation Plan (I-Plan). The I-Plan described locally agreed upon solutions to mitigate pollutant loading to the Carters and Burton Creek watershed.