Project Description
Parsons is conducting four Toxicity Maximum Daily Loads (TMDLs) for Patrick Bayou in Houston, Texas. Patrick Bayou, a tributary of the Houston Ship Channel (Segment 1006A), was placed on the states' Clean Water Act §303(d) list for water quality impairments associated with sediment toxicity, ambient water toxicity, temperature, and dissolved copper.
Expressing their interest in advancing water quality improvements and using sound science as a foundation for TMDLs and permitting decisions, a coalition of five industrial and one municipal dischargers chose to initiate the TMDL process for Patrick Bayou on their own. Since the Texas Natural Resource Conservation Commission (TNRCC) did not initiate or fund these TMDLs for Patrick Bayou, it was labeled as a third-party TMDL project. The coalition hired Parsons to provide the project management and technical support necessary to meet the objectives and requirements outlined in the TNRCC's TMDL guidance. From the outset of the project, the coalition made a significant commitment of time and resources. Coordinating with the TNRCC and engaging concerned groups and citizens, they established a formal watershed stakeholder group. Parsons, assisted by a professional facilitator that was also hired by the coalition, held six meetings with the stakeholder group and met monthly with the TNRCC project manager and district office representative. This commitment to communication and the extensive local and state involvement was critical to the success and rapid progress of the project.
The project team designed a comprehensive assessment approach for all four pollutants of concern. This included the preparation of a Quality Assurance Project Plan for all parameters, which was approved by TNRCC. The first phase of this project focused on compiling and summarizing the existing data (10 years) that had been collected on the Bayou since the early 1990s. This data was entered into an electronic database compatible with the GIS objectives of the project.
Based on the assessment of existing data and discussions with TNRCC, a detailed sampling design was prepared for 19 stations. It consisted of an intensive three-week sampling of water, sediment, and benthic organisms in August/September 2000; a one-week sampling period each in October 2000, and January 2001 for water quality parameters; and a concentrated sampling effort in April 2001 for water and sediments. During these four quarterly events temperature sampling was also conducted to collect data on thermal loading and hydraulic and hydrodynamic conditions associated with tidal exchange.
Copper and Ambient Water Toxicity TMDLs
Guided by previous clean metals sampling and toxicity data from a copper water effects ratio study that Parsons completed in 2000, a quarterly monitoring program was adopted for these parameters. The quarterly sampling program executed by Parsons acquired sufficient water quality data to verify that copper and ambient water toxicity concentrations do not exceed the revised state water quality criteria and therefore these pollutants could be removed from the 303(d) list. A comprehensive report was prepared summarizing this data collection and assessment effort which was used by the TNRCC as the basis for removing these two pollutants from the state 303(d) list. This targeted effort will save the State and the facilities discharging into Patrick Bayou significant time and financial resources in the long run.
Sediment Toxicity
Whole sediment toxicity testing using Leptochirus and Neanthes was conducted in August 2000 and April 2001 to determine potential sites where toxicity may occur. Sediments were also sampled for priority pollutant analysis, including dioxins. The sediment triad approach was used to statistically evaluate chemical and physical data, benthic organism data and overall sediment toxicity values to draw conclusions regarding the condition of the sediment. Multivariate statistical techniques were used define or explore relationships and inter-dependencies among measured variables. Statistical correlations and professional judgment were used to develop conclusions. If a site indicated whole sediment toxicity, then the plan required that samples be evaluated for porewater toxicity to see if water-based toxicity identification evaluation (TIE) protocols could be applied to determine specific toxicants.
At each of the 19 sample stations benthic organisms were collected and counted during the three seasonal events. In addition, whole sediment TIE protocols were developed and utilized to determine potential toxicants using state-of-the-art methods. This sediment toxicity TMDL is still underway; however, many unresolved issues and regulatory policy questions have been identified and presented to the state and EPA region for consideration.
Temperature
In addition to quarterly temperature sampling, intensive surveys were completed in August 2000 and January/February 2001, which verified the exceedances of the state water quality temperature criterion. Tidal and hydrologic measurements using Rhodamine dye tracers were also conducted to characterize the hydrodynamics of the bayou and selected outfalls for various seasons and model calibration. All relevant data (temperature, flow, tidal) was acquired, modeling using DYNHYD 5 and WASP 5 was initiated to evaluate thermal loading scenarios. Parsons extensive experience preparing TMDLs and presenting the technical underpinnings of the TMDL will then be applied to finalize the temperature TMDL for submission to TNRCC. Technical memos were prepared to obtain acceptance of the model selection, approach, and modeling scenario inputs, by the state, federal, and public stakeholders.
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