The operation and maintenance of mercury manometers have resulted in the release of elemental mercury at many natural gas industry metering sites. While the aerial extent of impacts at these sites is generally limited, cleanup costs, nonetheless, can be high due to the cost of treating and disposing of contaminated soil. Landfilling, at costs generally less than $70/CY, is a disposal option for soil containing low mercury concentrations, but the EPA's Land Disposal Restrictions prohibits landfilling of soil containing more than 260 mg/kg of mercury. Costs for thermal soil treatment (retorting), one of the few treatment options for soil exceeding that concentration, can be over $800/drum. Reliable on-site determination of mercury concentrations can minimize soil remediation costs. The direct mercury analyzer (DMA) can easily be adapted to on-site use following the new EPA Method 7473. The DMA functions on the basis of thermal decomposition, amalgamation, and atomic absorption spectrometry, with detection limits well below the 0.7 mg/kg Minnesota cleanup standard. The DMA was used during cleanup activities at numerous mercury-contaminated sites in Minnesota. The method provided real-time data to direct the extent of soil excavation and eliminated downtime while waiting for fixed-base laboratory results. Initial investigation activities and remobilizations were minimized using the DMA. Excessive and costly excavation of soil was limited with real-time data provided on-site. The on-site data was also used to segregate the more contaminated excavated soils. This segregation resulted in treatment and disposal cost savings. The remediation approach, a comparison of on-site and fixed-base laboratory data, and the cost-effectiveness of on-site use of the DMA are presented.
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