During site investigation all relevant information needed for a complete assessment has to be gathered and reviewed. Of particular interest should be the site’s physical characteristics; the physical and chemical characteristics of the potential contaminants of interest; and the likely transport pathways. Before fieldwork begins available information about the area of interest should be obtained and reviewed. The information gathered is used to establish a conceptual site model. A number of recent technological developments have encouraged the development of expedited site characterization approaches.
1. Site characterization approaches
In the early stages of the project planning process the data needs of the different user groups have to be identified (e.g. risk perspective, compliance perspective, remedy perspective, responsibility perspective).
The general objectives for any site assessment are to understand the:
- geology/hydrogeology of the site
- nature and extent of contamination (including physical and chemical characteristics of contaminants of interest)
- migration pathways and points of exposure (e.g. storm water runoff, sediment deposition, leaching into groundwater, groundwater recharge into surface water)
Approaches and methods:
- Conduct geophysical surveys (e.g. resistivity soundings)
- Install depth-specific piezometers and well clusters
- Sample and analyze for contaminants
- Define geology by extensive coring/split-spoon samples
- Evaluate hydrogeology (e.g. pumping tests)
- Perform tests on solids (grain size, clay content)
- Conduct tracer tests
- Evaluate sorption-desorption behavior using selected cores
- Identify bacteria and assess potential for biotransformation
2. Expedited site characterization approaches
To accelerate and improve cleanup processes the US EPA promotes the so called “Triad” approach, which involves systematic project planning, dynamic work plan strategies and the use of real-time measurement technologies.
During. During systematic planning, factors and variables that may impact the design and execution of project activities should be identified so that cost-effective strategies to manage those factors can be developed. The conceptual site model (see further description) is primary planning tool during project planning. The conceptual site model should consider all potential exposures and receptors.
The dynamic work plan is a flexible adaptive work strategy, which relies on real-time data to reach decision points and to identify the need for alternative action.
Commonly used field-based sampling and analytical technologies are:
- Direct-Push Sampling: Direct push units use hydraulic pressure to advance sampling devices and geotechnical and analytical sensors into the subsurface. The weight of the truck in combination with a hydraulic ram or hammer is used to “push” the tool string into the ground. The two major classes of direct-push platforms are cone penetrometer (CPT) and rotary hammer systems.
- Gas Chromatography: Gas chromatography (GC) analysis is a widely used technique for field-based analysis. Analysis of organic compounds is possible for a variety of matrices such as water, soil, soil gas, and ambient air.
- Geophysics: Three primary geophysical methods can be distinguished: in situ, surface and borehole.
- Immunoassay: Various immunoassay kits and methods are tailored to specific classes of environmental contaminants.
3. Weblinks and Guidelines
EU-Project CARACAS: “Concerted Action on Risk Assessment for Contaminated Sites in the European Union”
European Environment Agency (2000): Groundwater quality and quantity in Europe
Environmental assessment report No 3
European Environment Agency - Data Service: Corine Land Cover 2000
European Environment Agency - Data Service: Waterbase
US Army Corps of Enginees (1998): Technical Project Planning (TPP) Process. Engineer Manual. EM 200-1-2
USEPA (2003): Using the Triad Approach to Streamline Brownfield Site Assessment and Cleanup. http://brownfieldstsc.org
USEPA (2000): Innovations in Site Characterization. Case Study. Site Cleanup of the Wenatchee Tree Fruit Test Plot Site Using a Dynamic Work Plan. EPA-542-R-00-009
USEPA Hazardous Waste Cleanup Information:
American Society for Testing and Materials: Standard E1527-00 “Standard Practice for Environmental Site Assessments: Phase 1 Environmental Site Assessment Process
Boulding, J.R., Ginn, J.S. (2004): Practical handbook of soil, vadose zone and ground water contamination: assessment, prevention and remediation, CRC Press.
Abbaspour, K., Matta, V., Huggenberger, P., Johnson, C.A. (2000): A contaminated site investigation: comparison of information gained from geophysical measurements and hydrogeological modeling. Journal of Contaminant Hydrology 40, 365-380.