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(004) TMDL and TIE approaches for legacy sediment contaminants: arsenic and petrochemical case studies.
Brooks, Bryan*,1, Turner, Philip1, Stanley, Jacob1, Waller, William1, La Point, Thomas1, Palachek, Randy2, Sullivan, Andrew3, 1 University of North Texas, Denton, TX, USA2 Parsons ES, Austin, TX, USA3 Texas Natural Resource Conservation Commission, Austin, TX, USA
ABSTRACT- Texas Natural Resource Conservation Commission (TNRCC) selected seven waterbodies on the 1999 CWA 303(d) list for intense monitoring to support development of total maximum daily loads (TMDL). We evaluated ambient toxicity and performed toxicity identification evaluations on these systems during a year and a half study period. Because of historical contamination, two waterbodies, Alligator Bayou in Jefferson Co. and Fin Feather Lake in Brazos Co., are currently being evaluated for EPA's Superfund program. These systems presented unique challenges for sediment toxicity identification (TIE) procedures and TMDL development because; 1) consensus procedures for whole sediment TIEs do not exist; 2) guidance for sediment TMDL development is lacking; 3) Fin Feather Lake is historically contaminated by arsenic; and 4) Alligator Bayou is contaminated by a complex mixture of petroleum hydrocarbons and metals. To evaluate contaminant toxicity in porewaters and whole sediments, we utilized ion exchange media to iteratively reduce or remove chemical classes from samples. These procedures help to identify which chemical(s) are causing observed toxicity and, hence, provide the foundation for TMDL development in these waterbodies. However, our experiences identify that a lack of a translator mechanism, or a method to establish a water-based TMDL or control strategy to address sediment impairments provide serious impediments to performing sediment TMDLs. Neither a method nor a translator mechanism protocol exists within TNRCC or EPA Clean Water Act programs.
Key words: TMDL, Sediment TIE, Texas 303(d) list, legacy contaminants
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