Aquatic Risk Assessment for Pesticides. One of the most important ecological issues with pesticides is the potential for runoff and spray drift following applications. The runoff and spray drift have the potential to contaminate water bodies causing exposure to ecological species. Sciences has evaluated the potential aquatic risk of several pesticides for private clients to develop refined estimates of potential risks and recommend new data collection objectives for further refining assessments. Scientists at the firm have expertise using the most common tools for assessing pesticide runoff and spray drift, the Pesticide Root Zone Model (PRZM) and the Exposure Analysis and Modeling System (EXAMS) (link to models). PRZM is used to estimate runoff into a water body and EXAMS is used to estimate the partitioning of the pesticide in the water column.

Contaminated Sediment Investigation and Ecological Risk Assessment of Metal Bank Property. Ecologists and toxicologists at Tetra Tech supported the Department of Justice and EPA Region 3 in assessing aquatic environmental impacts and ecological risks resulting from historic PCB and oil leaching into the Delaware River near Philadelphia, PA. Tetra Tech searched, compiled, analyzed, and evaluated relevant chemical, biological, and toxicological data for the site and reviewed earlier risk assessments conducted by EPA and NOAA. Used GIS to map previous data collections in and around the site and developed a study plan to fill data gaps pertaining to sediment toxicity, bioaccumulation of PCBs and certain PAHs, and biological potential of the mudflat and river adjacent to the site. Tetra Tech designed and implemented sediment sampling at several sites for chemical, toxicological, and biological analyses and developed a novel in-situ chamber design for examining worm (Lumbriculis) bioaccumulation in 30 day studies. Additional data collections for the site included benthic macroinvertebrate sampling of the tidal freshwater mudflat and reference sites on the river. Tetra Tech conducted sediment toxicity tests using Hyalella and Chironomus and analyzed all toxicity and bioaccumulation data. Biota Sediment Accumulation Factors (BSAFs) were derived for Lumbriculis exposed in-situ at various locations and these data, along with sediment and water column data were used in ecological risk assessments to develop risk factors for invertebrates, fish, and wildlife, such as herons, kingfishers, and raccoons, for several contaminants including PCBs (by congener and by homologue grouping), dioxins and furans, and PAHs. Available feeding information and other life history traits were used to derive potential body burdens of certain contaminants in several different fish species common to the site, such as catfish, large mouth bass, and sunfish. Toxicity information was correlated with sediment concentrations of PAHs and PCBs using several normalizations to reflect relative bioavailability including percent organic carbon. Results of all analyses were used to evaluate remedy options for removing and/or containing upland sources of contaminants, reduce current risks of sediment contaminants in place, and prevent future re-contamination of the river and mudflat. A full report of the analyses and conclusions was prepared and submitted to DOJ and EPA, resulting in a settlement with the responsible parties in terms of the remedial actions necessary and future monitoring requirements.

Ecological Effects of Sediment-Associated Contaminants in Inner Burlington Harbor, Lake Champlain, Vermont. Tetra Tech designed and conducted a 2 year study to determine ambient sediment toxicity conditions in the harbor and to determine causes of toxicity if present. Spatial krieging analysis was used to infer areas of high pollutant concentration and associated levels of uncertainty based on previous sampling and analyses. This information was then used in discussions with VTDEC, Lake Champlain Basin representatives, and USEPA to target subsequent monitoring and identify areas of concern. The project integrated sediment and water chemistry, toxicity, and biological assessment (benthic macroinvertebrate) analyses (sediment quality triad) in addition to organism biomarker information, to assess the current status of sediment and water quality in the harbor. A Quality Assurance Project Plan was prepared by Tetra Tech for this project and approved by EPA Region 1 and the Vermont Department of Environmental Conservation to ensure that accurate, representative data were collected in this project. Sampling and testing was performed in both the summer and spring because of concerns in contaminant loadings and bioavailability during these seasons. Toxicity tests included acute (10 day) and chronic (28 day) Hyalella azteca sediment tests, pore water tests from supposedly contaminated sites using Ceriodaphnia dubia, 28 day Lumbriculus bioaccumulation tests, Pimephales promelas chronic (7 day growth) tests, and novel protein expression analyses on sediments taken from various places in the harbor. These tests, in addition to chemical and biological assessment results for the same sites were used to evaluate areas of concern in the harbor and to obtain preliminary apparent effects threshold concentrations for PAHs and several metals, the major pollutants of concern. Supporting chemical data collected in this project (acid volatile sulfide, organic carbon, and organic nitrogen concentrations) were used to interpret potential toxic effects of metal and PAH concentrations. Multivariate analyses were used to partition chemical and physical factors that most affected biological repsonses such as Hyalella survival, fathead minnow growth, and Chironomid species diversity. A weight of evidence approach (sediment quality triad) was used to assign probable risk of contaminants to aquatic life in the harbor and Lake Champlain as a whole.

Site-Specific Ecological Risk Assessment. For FMC and JR Simplot in Pocatella, Idaho, Sciences performed a detailed site-specific risk assessment which included an ecological risk assessment for the American Falls Reservoir, terrestrial exposures, and exposures to fish in the Port Neuf River. For the American Falls Reservoir, there was a concern that impacts had occurred downstream from the site from the discharge of the Port Neuf River to the American Falls Reservoir. The initial proposal was to perform a sampling program that included sediment, benthic communities, fish, and other food chain organisms. In response, Sciences' experts proposed a decision-tree approach that involved an initial sediment sampling program with an agreed upon result that should statistically significant contributions to sediments from the Port Neuf River be identified, the benthic community sampling program would go forward; if no contribution was found, the sampling program would stop. Likewise for sampling the benthic community and so on up the food chain. No statistically significant result was found in sediments from the Port Neuf River so an extremely expensive sampling program was avoided on sound scientific grounds. Likewise, Sciences' experts established a statistically representative sampling program for fish in the Port Neuf River, sampling stations were established upstream and downstream from the site with analysis to determine likely contribution from the site. Further questions concerning soil contributions from air emissions from the facilities involved extensive potential contamination; bioavailability became a major issue. Concerns about both human health and impacts on ecological systems resulted in Sciences establishing a statistically representative sampling program with terrestrial organisms and plants co-located with soil samples. The finding was that the high levels of alkalinity in the soil inhibited plant uptake of the metals of concern. Excavation of off-site soils was found to be unnecessary. Thus impacts on aquatic organisms and plants were effectively addressed and detailed in the final risk assessment.