Contaminant Assessment of Patrick Bayou

In July 1994, the Texas Natural Resource Conservation Commission (TNRCC) and United States Environmental Protection Agency (EPA) Region 6 conducted an ambient toxicity and water and sediment quality survey of Patrick Bayou, a small tributary of Segment 1006 of the Houston Ship Channel (HSC). Patrick Bayou is bounded by and receives effluent from several industrial dischargers and one municipal wastewater treatment plant. This area was investigated because a recent HSC study found ambient water and sediment toxicity and elevated levels of several priority pollutants in Patrick Bayou. The primary objective of this study was to collect water and sediment samples in Patrick Bayou to provide information on the magnitude and spatial distribution of contamination and toxicity in this small bayou. Ten stations were chosen for priority pollutant analyses and a TNRCC routine monitoring station was also sampled during the survey. Several stations were selected for water and/or sediment toxicity testing. Out of five stations tested, water from four was toxic to Mysidopsis bahia and one of those was also toxic to Menidia beryllina. Significant mortality to Cyprinodon variegatus was observed in two of five sediment elutriate tests. State water quality standards were exceeded in Patrick Bayou for dissolved copper (8 sites), dissolved lead (3 sites), total mercury (1 sites), carbon tetrachloride (1 site), and water temperature (4 sites), although a few of these exceedances were inside mixing zones. Three Patrick Bayou stations has unionized ammonia values that exceeded the EPA chronic criteria for saltwater. More than 40 percent of the sediment samples in Patrick Bayou exceeded TNRCC sediment screening levels (85th percentiles) for Cr, Cu, Pb, Hg, Ni, Se, Zn, hexachlorobenzene, total polychlorinated biphenyls (PCBs), and bis(2-ethylhexyl) phthlate. Very high levels of mercury (8.3 ppm), hexachlorobenzene (83,900 ppb), hexachlorobutadiene (138,000 ppb), PCBs (4,150 ppb), polynuclear aromatic hydrocarbons (total PAHs 233,700 ppb), and lead (269 ppb) were found in Patrick Bayou sediments. State screening levels were not available for the remaining 24 organic compounds found in the sediments. Lead, mercury, PCBs, acenapthene, acenaphthylene, anthracene, fluorene, naphthalene, 2-methylnaphthalene, phenanthrene, benzo(a)anthracene, benzo(a)pyrene, chrysene, fluoranthene, pyrene, and total PAHs all exceeded the effects range median levels developed by the National Oceanic and Atmospheric Administration. Overall, Patrick Bayou showed a significant accumulation of many priority pollutants in sediments, exceedances of several water quality standards, and ambient toxicity in both water and sediment. The specific distribution of the contaminants in the sediments gave some information on their potential sources. The major dischargers along Patrick Bayou have proposed to sample their effluents for the compounds found in the bayou to further pinpoint the sources.