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Commercial Chemicals & Nuclear Programs
Contaminated Site Remediation Section |
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TAB #29: Expedited Site Characterization: Tools And TechnologiesDESCRIPTION:The process of Expedited Site Characterization (ESC) described in TAB # 27, is made possible by the tool and technology selection criteria/philosophy, of the ESC methodology, reviewed in TAB # 28. The development and acceptance of the array of new tools and technologies allow the rapid collection and analysis of data. Selected tools and technologies that are currently being accepted and used for ESC are presented. These fall into five broad categories: Non-Intrusive Tools, Subsurface Access Technologies, Analytical Chemistry Technologies and Data Management and Visualization Technologies.INTRODUCTIONThe tools that are currently being accepted and used for ESC fall into five broad categories:
Aerial images are either photographs, or output from a variety of remote sensing techniques. They are often the primary source of information for the initial stage of an ESC. Non-intrusive tools rely on Geophysics, and are discussed in the following Section. They constitute a "second line" of tools for the collection of information towards the development of the conceptual model. Subsurface Access Technologies are the tools that imply or relate to the intrusion of the subsurface. Only recent technologies aimed at accelerating investigations will be presented. The field of analytical chemistry has also experienced a recent surge in new developments aimed at expediting the generation of results, and these are emphasized in this document. Finally, since the process of ESC requires the rapid processing of information and communication of results, and interpretations among team members and the other stakeholders, new developments in data management and visualization are mentioned. NON-INTRUSIVE TOOLS General information on their use: The use of non-intrusive tools, cost-effectively, increases sampling density at a site. They allow the detection and mapping of anomalies, the mapping of the presence and continuity of strata, and the mapping of the limits of buried waste, landfills or trenches. These techniques rely on the contrast between the measured property of the target region and the background conditions. They include the following: 1. Surface Geophysical Surveying Methods
2. Borehole Geophysical Surveying Methods
SUBSURFACE ACCESS TECHNOLOGIES Requirements The technologies discussed here, serve the purpose of penetrating the subsurface for the collection of samples (gas, water, and soil), and for the installation of data collection instruments. The inclusion and use of existing wells increases the number of locations previously accessed. Using direct push for subsurface access, provides "continuous" monitoring of the subsurface, as opposed to its "discrete" counterpart. The techniques involved in the drilling of new wells are readily available, and generally well understood by field personnel and regulatory authorities. In addition to conventional drilling technologies, there are emerging technologies, such as rotasonic drilling, which may match some of the advantages of direct push technologies. Most of the recent Research and Development for the intrusive technologies, has been towards the direct push techniques. Direct Push technologies have been developed and used for many years by the Civil Engineering industry for the exploration of geological strata. Environmental industries have added chemical detection capabilities to the direct push techniques. Direct Push Technologies Advantages:
Limitations:
Two classes of direct push technologies exist for subsurface probing: 1. Percussion Probing.
2. Cone Penetration.
See Table 1 for a partial comparison of the two techniques. Percussion Probing is generally more productive and more maneuverable than cone penetration testing. The systems are both well suited to the abstraction of depth-discrete groundwater and soil gas samples. Percussion Probing is well suited for the collection of continuous (limited) or depth-discrete soil samples. CPT is particularly effective for soil stratigraphic logging and chemical screening. The stratigraphic logging sensors are well developed and proven, whereas many of the chemical sensors are still being developed and validated in the field. Fluorescence sensor systems, both laser induced and mercury bulb contact activation, are the most developed. These sensors have the ability to detect aromatic compounds in the subsurface. CHEMICAL ANALYTICAL METHODS Fixed-based versus field methods The decision between using an off-site, fixed-base laboratory versus an on-site mobile laboratory will depend on:
When only a small number of samples will be collected, samples can be transported rapidly by air freight to a fixed laboratory service that offers a 24 hour turn-around time. This avoids the expense of bringing a laboratory to the field, while achieving the rapid analytical output, that is necessary for a successful dynamic field investigation. The laboratory analytical techniques, (contained in the following sections), and field technologies (Table 2), are some of the approaches used in the context of an ESC. Organic Contaminants Standard Laboratory Analysis:
Newly emerging methods - hand-held or transportable:
Inorganic Contaminants Metals:
Radionuclides:
Other Inorganics (sulfates, nitrates, chlorides, etc.):
DATA VISUALIZATION Requirements
Applications In many cases, maps, photographs, and other geo-referenced images (in reports and presentations) are the only visible evidence to regulators and the public that progress is being made in the environmental clean-up. In addition, visualizing site data in three dimensions can be critical in the development and testing of a site model. Thus, thematic mapping during all phases of remediation and restoration is a fundamental activity. Geographic Information Systems (GIS) and data visualization technologies can, and should be employed early in the remedial process to create a database for recording, modeling, and mapping spatial data related to site characterization and remediation activities. The rapid pace that is set for regulatory compliance, and the legal requirements for historical records and long-term site monitoring have made GIS vital for information management, analysis, and presentation. For example, within the Department of National Defence , most facilities have developed a GIS for thematic mapping and site analyses. These systems, developed with such commercially available software as Arc/Info®, MapInfo® and Intergraph®, are excellent sources of data for site remediation activities in and around the facilities. GLOSSARY Rotasonic: This is a drilling technique where a casing penetrates the subsurface (soil and rock) through the simultaneous application of rotation and a high frequency (50-150Hz) axial vibration. It is a variation of Resonant-Sonic drilling, the name indicating that the frequency of vibration is set to achieve harmonic resonance within the casing thereby greatly facilitating the propagation of the vibration from the vibratory head to the tip of the casing. Tomography: A method for determining the distribution of physical properties within a given volume of subsurface, by inverting the results of a large number of measurements made in three dimensions (e.g., seismic, radar, resistivity, and EMS) between different source and receiver locations. SOURCES OF INFORMATION ON ESC INVESTIGATIVE TOOLS A catalogue of technologies developed through the US Department of the Environment's Characterization, Monitoring, and Sensor Technology Program can be found on the Internet at: Also, the US Environmental Protection Agency (EPA) has databases for site characterization technologies at the following Internet locations:
SELECTED REFERENCES ASTM (1995). Provisional Standard Guide for Accelerated Site Characterization for Confirmed or Suspected Petroleum Releases. PS3-95, Annual Book of ASTM Standards, Philadelphia. Burton, J.C., J.L. Walker, P.K. Agarwal and W.T. Meyer (1995). Expedited Site Characterization: An Integrated Approach for cost- and time-effective remedial investigations. Argonne National Laboratory. Owen, Gareth (1997). Contaminated and Hazardous Waste Site Management. Contaminated and Hazardous Waste Site Management Course, GOwen Environmental Limited, Toronto, Ontario. Purdy, Caroline (1997). Expedited Site Characterization - Tools and Technologies. Contaminated and Hazardous Waste Site Management Course, GOwen Environmental Limited, Toronto, Ontario. Tétreault, Michel (1996). Contaminated Site Investigation Process and Practices. Contaminated and Hazardous Waste Site Management Course, GOwen Environmental Limited, Toronto, Ontario. USEPA (1993). Subsurface Characterization and Monitoring Techniques: A Desk Reference Guide. Vol. 1 and Vol. 2, EPA/625/R-93/003 a & b. USEPA (1997). Expedited Site Assessment Tools for Underground Storage Tank Sites: A Guide for Regulators. EPA 510-B-97-001. For further information please contact:
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