Radiological Engineering and Health Physics Services
Radiological Surveys Assisted by GPS
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To date, well over one million acres have been surveyed using numerous GPS assisted methods. ERG utilizes several types of GPS systems to obtain the necessary accuracy required for surveying. Accuracies as low as < 10 inches may be achieved using a series of filtering techniques developed by ERG.
ERG has been conducting GPS-based radiological surveys since 1994. Early work was in support of Conventional Uranium Mill Site cleanups. Vehicle mounted systems were used to collect the data over large areas (some sites had windblown tailings covering 1000+ acres). Correlations between soil sample Ra-226 concentrations and gross gamma count rates were used to delineate the excavation boundaries. ERG has performed these types of surveys in support of both government and non-government clients, and sites regulated by a variety of federal and state agencies, including the DoD, DOE, NRC and USACE. These surveys for characterization, remediation support, and final status surveys have, and continue to be, a significant portion of our business.
ERG has adapted these surveys to fully support MARSSIM requirements. In particular, for surface soil contamination removals, remedial action support surveys (RASS) are performed to delineate areas requiring excavation. ESRI ArcGIS generated maps, coupled with on-site analysis of soil samples to develop gamma/soil concentration correlations, provide maps showing areas requiring further remediation. Scanning minimum detectable concentrations (MDC) are determined by sampling areas exhibiting slightly elevated gamma levels on the maps. In addition, elevated areas are analyzed using ArcGIS to determine whether they meet the elevated measurement comparison DCGL (DCGLEMC). A final status survey (FSS) is then performed with the variance of the gross gamma data used to estimate the variance of the constituent of concern in the soil. gps