2019 Phase 3 Sediment Sampling
- Details
- Published: Thursday, 21 March 2019 22:18
More in-river sampling is being scheduled for 2019 between the Marcus area and the Canadian Border as a continuation of preliminary work started in 2018 for the third phase of the Sediment Study (Phase 3). EPA first conducted sediment studies in 2005. The purpose of Phase 3 work is to inform the Baseline Ecological Risk Assessment (BERA) that Teck American, Inc. (TAI) continues conducting with oversight from EPA.
The BERA evaluates risk (i.e., the potential for adverse effects) to wildlife on land and in water, including river benthic (i.e., aquatic sediment-dwelling) invertebrate life such as mayflies, mussels, and crayfish. This is a key part of the assessment of metals and other contaminants of concern under the RI/FS.
The Phase 3 Sediment Study includes sediment and porewater sampling in three areas of interest (AOIs) in the northern section of the UCR Site: Deadman’s Eddy, China Bend and a location upstream of Marcus Flats near Evans. The three AOIs were selected based on evaluation of data from sediment sampling conducted in 2005 and 2013. The Phase 3 study features five main components.
Sediment Facies Mapping: The mapping study will collect high-resolution data to identify and map sediment grain size fractions and texture of the UCR sediment bed in the northern section of the UCR Site. Further characterization of sediment bed attributes is needed to inform and support other subsequent Phase 3 efforts. At varying degrees of measurement resolution detail the following data will be collected in support of the mapping effort:
o Bathymetry and backscatter using a multibeam echosounder (MBES)
o Vertical velocity profile measurements via acoustic Doppler current profiler (ADCP)
o Underwater imagery using a drop-frame camera equipped with scaling lasers
For this study component, approximately 35 miles of river from Marcus to just north of Deadman’s Eddy were surveyed in 2018. The remaining 5 river miles to the US-Canada border will be surveyed this summer. The survey is of higher clarity and resolution in the AOIs. The survey data were used to develop “facies maps” to classify areas such as gravel, cobble and sand that would help identify the best sites for sediment sampling in the three AOIs. Less detailed facies maps will also be developed in 2019 for the river surveyed outside of the AOIs.
Sediment Sampling: Samples of river sediment will be collected to measure concentrations of metals and other chemicals of interest that could pose risk to benthic invertebrates and other aquatic organisms in the AOIs.
Porewater Sampling: Porewater refers to the water between the grains of sediment in the river. It’s of interest because metals and other chemicals of interest leach from the sediments into porewater and thus can become available to benthic organisms living in and ingesting this water. This sampling will assist in better understanding risk to benthic invertebrates due to metals in porewater, and in better understanding the relationship between concentrations of metals in sediments and metals in water.
Bioassays: Contaminated sediment toxicity to aquatic benthic invertebrates can be evaluated with laboratory tests known as bioassays. Extensive bioassay testing has previously been performed. This additional bioassay testing will be performed in conjunction with other measurements on sediments collected within the three AOIs. This may help further evaluate risk to organisms coming in contact with site sediment and porewater. If biological effects are observed in sediment bioassays from the sediments sampled, an additional laboratory sediment assessment techniques known as toxicity identification evaluations (TIEs) will be employed on the sediment samples. TIEs will be conducted to potentially help better describe the substances or conditions cause toxic responses in site sediments.
Benthic Invertebrate Community Survey: Benthic invertebrates are organisms such as mayflies, crayfish, and mussels, that live in or on the bottom sediments. Benthic invertebrates can be adversely affected by sediment contamination, and the types of organisms present in a sediment sample also can provide information about whether contaminants in the sample are having an effect on the benthic community. The survey will provide information on the species composition and diversity of benthic communities in the AOIs to be sampled.
A Quality Assurance Project Plan (QAPP) is currently in development and, if approved, will result in field work beginning in the fall of 2019.