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Nueces Bay: A TMDL Project for Zinc

A project to protect the safety of oyster consumption by people by reducing zinc in oyster harvesting waters. The adopted total maxim daily load (TMDL) and approved implementation plan (I-Plan) together are the road map for improving water quality.

Counties: Nueces, San Patricio
Parameter: Zinc in oyster tissue
Basins: Bays and Estuaries, San Antonio–Nueces Coastal, Nueces River, Nueces–Rio Grande Coastal
Segment: 2482

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Background and Goals

Nueces Bay is a shallow, secondary bay that receives freshwater from the Nueces River and exchanges saline water with Corpus Christi Bay. Economic activities in and around the bay include petrochemical refining and production, agriculture, manufacturing, recreation, maritime commerce, and tourism. Ecologically, Nueces Bay provides a home for many plants and animals, and plays a role in water purification and storm protection.

Harvesting of oysters and other edible shellfish from the bay is currently restricted because concentrations of zinc in oyster tissue pose a risk to consumers. TCEQ’s TMDL Program is directing a project to reduce zinc concentrations to levels that make it safe to harvest and eat oysters from the bay.

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As of its last assessment in November 2020, the Texas Department of State Health Services (DSHS) still classifies Nueces Bay as restricted for oyster harvesting. Learn more about risk assessments and classifications of shellfish harvesting areas on DSHS's webpage Shellfish Harvesting Areas and MapsExit the TCEQ. Lear more about the possible risks of eating oysters from restricted areas at Risks of Eating ShellfishExit the TCEQ.

Public Participation

The TMDL Program worked with the existing forum of the Coastal Bend Bays and Estuaries Program (CBBEP)Exit the TCEQ to involve area stakeholders in this project.

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Adopted TMDL

The commission adopted this TMDL on November 1, 2006. It was approved by the EPA on December 15, 2006, at which time it became part of the state's Water Quality Management Plan.

Updates to TMDLs

From time to time, it is necessary to revise TMDLs to account for changing conditions in the watershed, such as new or amended permits, or urban growth, or to correct oversights in the original TMDL report. Revisions to the load allocations in TMDLs are made via the state’s Water Quality Management Plan (WQMP), which is updated quarterly.

The WQMP provides projected effluent limits for use in planning and permitting activities under the Texas Pollutant Discharge Elimination System (TPDES). The TCEQ reviews all applications for new and amended permits for conformance with applicable portions of the WQMP, including adopted TMDLs.

Revisions to the TMDL are documented in the approved WQMP updates listed below.

Learn more about WQMP updates and about opportunities to comment on revisions to them.

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Approved I-Plan

The commission approved the I-Plan on October 24, 2007.

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Technical Support Document

Annual Reports

Miscellaneous Reports

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Contact the TMDL Program

Please email, and reference the Nueces Bay project in the subject line. Or call us at 512-239-6682.

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