Eastern Michaud Flats (Idaho)
Formation Environmental personnel have been involved in the Eastern Michaud Flats (EMF) Superfund Site project since 1994, initially assisting with the RI/FS phase and later serving as the technical lead for remedial design to address groundwater conditions.
Remedial Design/Remedial Action
Formation personnel began leading groundwater remedial design activities for the eastern portion of the site in 2004. Detailed, subsurface, hydrogeologic and geochemical data were collected to evaluate an existing groundwater extraction and monitoring system. GIS analysis and groundwater modeling indicated that expansion of the existing system would improve groundwater capture and attain performance standards for the groundwater remedy. The redesigned groundwater extraction and monitoring system was installed in four phases from 2004 to 2010. Formation continues to provide technical support for treatment system performance, quarterly groundwater and surface water monitoring, remedy performance assessments, and discussions with Federal and State regulatory agencies on groundwater issues.
Hydrogeology and Groundwater
The subsurface investigation technologies and data analyses used by Formation to support remedial design for the groundwater remedy included:
- Sonic drilling obtain depth-discrete geologic samples for geochemical and geotechnical analysis and provide lithologic and stratigraphic data for detailed mapping
- Hydropunch, discrete-interval groundwater sampling, during sonic drilling, to profile groundwater quality and provide the basis for field decisions regarding well construction
- Multi-level and nested designs for monitoring and extraction wells
- Surface geophysical surveys for mapping stratigraphy and groundwater chemistry
- Development of a three-dimensional hydrostratigraphic model which provided the framework for analytical and numerical modeling of groundwater flow and contaminant transport.
Formation Environmental redesigned a groundwater extraction system as part of a comprehensive remedy to reduce the concentration of contaminants in groundwater discharging to a nearby river.
A 3-D hydrostratigraphic model, constructed in a GIS, formed the basis for a predictive model of groundwater flow and mass flux. Our modeling team used MODFLOW and MODPATH to support the optimization of location and pumping rates for groundwater extraction wells installed in a multi-aquifer system.
Formation Environmental facilitated a collaborative process with the client, regulatory agencies, and other stakeholders to build consensus on model-design issues, including the conceptual site model, identification of data gaps, design objectives, and required analyses. The extraction system design was approved and implemented. Groundwater and surface water monitoring verify the design objectives are being achieved.