Bayou Verdine, Calcasieu Estuary, LA

Client: Conoco and Condea Vista

Location: near Lake Charles, LA

Summary: Cardno ENTRIX conducted both screening-level and baseline assessments of risks to humans and wildlife in Bayou Verdine. We prepared a baseline human health and detailed quantitative ecological risk assessment for portions of Bayou Verdine, which is a tributary to the Calcasieu Estuary near Lake Charles, LA. The purpose of this risk evaluation was to quantify potential risks to humans and ecological receptor populations exposed to site constituents in the sediment and surface water in the bayou. These assessments were based on a comprehensive determination of the nature and extent of contamination (metals, PAHs, PCDDs, PCDFs, semi-volatile and volatile organic compounds, and pesticides) in sediment, surface water, wetland soil, and biological tissues.

For both assessments, detailed conceptual site models were developed. Human evaluation focused on exposures for hypothetical recreational users and industrial worker?s contact with bayou surface water and sediment. In conjunction with the ecological evaluation, human food chain issues were quantitatively addressed for recreational and subsistence consumption of fish and shellfish residing in the bayou. A sediment quality triad was employed to further assess the environmental quality of the system. A sediment pore water toxicity identification evaluation was also conducted, which demonstrated that toxicity to sediment benthic invertebrates was due largely to bioavailability of non-polar organic compounds (e.g., PAHs). Based on estimated risks and sediment toxicity, a remedial action plan was developed to mitigate risk in the bayou, based on equilibrium partitioning of PAHs.

Highlights: Results of the risk assessments were well received by EPA Region 6, NOAA, and the public stakeholders. Cardno ENTRIX facilitated a cooperative relationship between the clients and the Natural Resource Trustees that has resulted in a smooth transition from risk assessment to settling NRD issues in portions of the Calcasieu Estuary. As a result of the evaluation, the Trustees have designated the human health issues along that portion of the bayou as not a concern for natural resource damage assessment (NRDA). Information from the ecological risk assessment was used to conduct an NRDA evaluation that identified the magnitude of injury to the bayou and provided the basis for scaling and designing a compensatory restoration project. USEPA Region 6 is using human recreational scenario assumptions presented for Bayou Verdine to address other areas of the Calcasieu.