Water Quality > Water Quality Monitoring > TMDL

TOTAL MAXIMUM DAILY LOAD (TMDL)

The TMDL is the amount of a pollutant a stream can assimilate and still meet State water quality standards. The Federal Clean Water Act requires that TMDLs be developed on all waterbodies that are impaired (listed on the EPA 303(d) list). Once TMDLs are established for a stream, steps can be taken (rigorous wastewater permit limits, abatement of storm water runoff, utilization of best management practices, etc.) to reduce pollutant levels, that will allow the stream to meet the Texas State Water Quality Standards.

The goal of a TMDL is to restore the full use of a water body that has limited quality in relation to one or more of its uses. The TMDL defines an environmental target and, based on that target, the state develops an implementation plan to mitigate anthropogenic (human-caused) sources of pollution within the watershed and restore full use of the water body. See TCEQ TMDL Website for further Information.

Current TMDL Projects

Leon Creek, Segment 1906 TMDL for Dissolved Oxygen and Bacteria Impairments:

The draft 2008 TCEQ 303(d) List (March 19, 2008) identifies several assessment units in the Lower Leon Creek as being impaired based on the state’s contact recreation (bacteria) and high aquatic life (dissolved oxygen) use criterion. In response to these conditions, the TCEQ Total Maximum Daily Load Program in partnership with the San Antonio River Authority (SARA) have initiated a project to verify depressed dissolved oxygen and develop information necessary to support a bacterial (E. coli) Total Maximum Daily Load (TMDL) in the Lower Leon Creek, Segment 1906.

The specific objectives of the Leon Creek Segment 1906 TMDL for Dissolved Oxygen and Bacteria Impairments, TCEQ contract number 582-8-80193 are to: (1) Collect targeted 24 hour dissolved oxygen data in order to verify the water quality impairment and overall organic loading; (2) Collect targeted bacterial data in order to establish source of impairment and over loading; (3) Conduct modeling and assessment activities required to allocate loading; (4) Provide technical assistance to the TCEQ in the evaluation of actions necessary to achieve the recommended loading allocations, and; (5) Document, compile, and summarize technical analyses in reports to the TCEQ. There are two phases to this project; Phase I addresses dissolved oxygen deficiencies in Leon Creek, Phase II addresses excessive bacteria concentrations. Both phases will be conducted simultaneously.