Upper Texas Gulf Coast: A TMDL Project for Bacteria in Oyster Waters
Counties: Brazoria, Chambers, Galveston, Harris
Parameter: Bacteria in Oyster Waters
Basins: Neches-Trinity Coastal, Trinity River, San Jacinto River, and San Jacinto–Brazos Coastal, Bays and Estuaries
Segments: 2421, 2422, 2423, 2424, 2432, 2433, 2434, 2435, 2439
- Project Overview
- Background and Goals
- Get Involved
- Proposed Implementation Plan
- Total Maximum Daily Loads
- Reports and Other Documents
- For More Information
Background and Goals
Bacteria concentrations are sometimes elevated in several bays in the Houston–Galveston area. Restricted areas are closed to the harvesting of shellfish for direct marketing. Microorganisms from human and animal waste may contaminate oysters and other shellfish, making them unsafe to eat, especially since some shellfish are eaten raw.
The use of coastal waters for harvesting shellfish—called the “oyster waters use” in the state’s standards for surface water quality—is the most commonly impaired use among Texas bay and gulf waters. The affected segments are Upper Galveston Bay (Segment 2421), Trinity Bay (Segment 2422), East Bay (Segment 2423), West Bay (Segment 2424), Chocolate Bay (Segment 2432), Bastrop Bay/Oyster Lake (Segment 2433), Christmas Bay (Segment 2434), Drum Bay (Segment 2435), and Lower Galveston Bay (Segment 2439).
Assessment of the oyster waters use is conducted by the Seafood Safety Division of the Texas Department of State Health Services. The DSHS is responsible for monitoring and classifying shellfish harvest areas into four categories for harvesting—approved, conditionally approved, restricted, or prohibited. These classifications are published as maps on the DSHS website .
The goal of this TMDL project is to improve water quality so that the oyster beds are routinely safe for harvesting. Analysis indicates that isolated zones of high bacteria concentrations occur in isolated areas near shorelines, rather than occurring chronically throughout the bays. Because the exceedances are confined to discrete areas, bay-wide reductions can be achieved by targeting each isolated zone.
The TCEQ is working with existing forums in the watershed to inform the public about the project and work together with stakeholders on an I-Plan to improve conditions in the watershed.
The Galveston Bay Foundation is coordinating stakeholder participation in developing the I-Plan. Work groups were formed at a public meeting on February 24, 2010. These work groups are developing sections of the I-Plan.
The Foundation hosted three meetings in July 2010 to share progress on I-Plan development and the draft management measures developed by each work group.
For additional information about the work group meetings or to get involved, visit the Galveston Bay Foundation website.
Proposed Implementation Plan
Public comment on the proposed implementation plan closed on May 18, 2015.
Total Maximum Daily Loads
On August 20, 2008, the commission adopted the six original TMDLs below. On February 4, 2009, the EPA approved these TMDLs, at which time they became part of the state’s Water Quality Management Plan.
- Six Total Maximum Daily Loads for Bacteria in Waters of the Upper Gulf Coast, Segments 2421, 2422, 2423, 2424, 2432, and 2439
(Includes an amendment in Appendix that gives the median fecal coliform capacity of the restricted oyster-water assessment units; this also serves as Addendum 1 to the original document.)
- Response to Public Comment on the TMDLs
TMDLs for three additional segments—2433, 2434, and 2435—were added by addenda in 2012 (see below).
Revisions to TMDLs
From time to time, it is necessary to revise TMDLs to account for changing conditions in the watershed. 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 are made to TMDLs in one of two ways:
- Updates are made to account for changing conditions in the watershed, such as new or revised wasteload allocations, permits that have been canceled or have expired, or changed facility names.
- Addenda are created to add load allocations for assessment units that are impaired by the same pollutant or condition, within the same watershed as in the original TMDL report.
Both updates and addenda are provided in the same units of measure used in the original TMDL.
Additional TMDLs for the Upper Texas Coast have been added by addenda:.
- TMDL Addendum One: added as Appendix C in the original TMDL report September 2009
- TMDL Addendum Two: Two TMDLs for Bacteria in Drum Bay
January 2012 WQMP Update, Approved by EPA April 2012
- TMDL Addendum Three: Two TMDLs for Bacteria in Bastrop Bay/Oyster Lake and Christmas Bay
April 2012 WQMP Update, Approved by EPA August 2012
The reductions of bacteria loads were completed using a concentration-based approach, which compares water quality to both the median and the 90th percentile criteria for acceptable concentrations.
Updates to the TMDL are documented in the approved WQMP updates listed below.
- January 2013, Appendix IV, page 14
- April 2012, Appendix II, page 11 (Bastrop Bay/Oyster Lake and Christmas Bay Addendum)
- January 2012, Appendix V, page 18 (Drum Bay Addendum)
- Octob/assets/public/sitewide/pdf.gif" /> Appendix III, page 14
- October 2009, Appendix III, page 15
- July 2009, Appendix V, page 12
- April 2009, Appendix V, page 21
Summaries of Public Meetings during TMDL Development
- February 2010 Meeting
-February 28, Clear Lake
- June 2008 Meetings
- June 9, Clear Lake; June 11, Hankamer
- Presentation: Overview of the Project
- February 2008 Meetings
- February 27, Hankamer; February 28, Clear Lake; February 29, Galveston
- Presentation: TMDL Process
- Presentation: DSHS Overview of Oyster Waters and Classification Zones
- Presentation: Project Overview - Upper Coast Oyster Water TMDL for Bacteria
- Handout: Reductions Necessary to Meet 90th Percentile Criteria
- Handout: Announcement for April 2008 Storm Water Workshop
Reports and Other Documents
1905 Map of Galveston Bay:
This 1905 map of Galveston Bay (JPG, 9.9 MB) was originally produced by the Corps of Engineers. An old paper copy, the only known copy of this map, was scanned to produce digital images.
The file posted here was made by combining two overlapping partial images, merging to a single image, adjusting color to reduce yellowed effect of original, trimmed, and reduced to 4000 x 4000 pixel density to make a smaller but readable image.
Larger format (6848 x 9584 pixels) files are available in TIF and JPG format, but require additional work to merge pieces or color correct the image. Contact us (see below) if you want the original files.
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