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Lower Leon Creek: Bacteria

This completed project assessed the extent of bacteria impairments in Lower Leon Creek.

photo of Lower Leon Creek
Lower Leon Creek

County: Bexar
Parameter: Bacteria
River Basin: San Antonio
Segment: 1906

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Background and Goals

In Lower Leon Creek, TCEQ measured concentrations of bacteria in the past at levels that might pose a health risk for swimmers. Bacteria from human and animal waste can indicate the presence of disease-causing microorganisms. People who swim or wade in the creek might be at risk. The state’s standards use the term contact recreation to refer to swimming or other recreational activities during which it is likely a person may ingest natural waters.

In 2008, TCEQ’s TMDL Program initiated an assessment project to determine the extent and severity of water quality impairment in Lower Leon Creek.

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Watershed Description

Lower Leon Creek, Segment 1906, drains an area of 228 square miles and has a total length of 57 miles. It originates as a spring-fed stream in the Edwards Plateau region of south-central Texas. The creek runs from its headwaters in northern Bexar County to its confluence with the Medina River. The creek generally flows south and enters the main portion of the Kelly Air Force Base (AFB) from the northwest, near the intersection of Billy Mitchell Road and Westover Road.

Leon Creek drains a highly urbanized residential area and the Kelly and Lackland AFBs. Water quality in the creek is affected by industrial and municipal wastewater discharges and stormwater. The project watershed included the cities of San Antonio, Cross Mountain, Helotes, and Leon Valley.


TCEQ and the San Antonio River Authority (SARA) completed a two-year intensive effort to collect additional data in 2010. Review and analysis of the new data showed that the creek is supporting its contact recreation use. The bacteria impairment was subsequently removed from TCEQ’s list of impaired waters.

TCEQ and SARA will continue to monitor water quality in Leon Creek under the TCEQ’s Surface Water Quality Monitoring and Clean Rivers programs.

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Public Participation

Public participation is an important component of all TMDL projects. The TCEQ coordinated local involvement in this project through the San Antonio River Authority    with the help of the Bexar Regional Watershed Management Water Quality Focus Group, a public participation forum.

Learn more about water quality standards and management by reading the TCEQ’s publication Preserving and Improving Water Quality.

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Contact the TMDL Program

Please e-mail and mention the Lower Leon Creek bacteria project in the subject line. Or call us at 512-239-6682.

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Communities Working Together