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Chromium
Routine groundwater monitoring conducted in 2005 led to the identification of chromium contamination in regional groundwater at monitoring well R‑28 located in Mortandad Canyon. Chromium concentrations at that well are approximately 400 μg/L (ppb), exceeding the New Mexico Environment Department (NMED) and Environmental Protection Agency standards of 50 μg/L and 100 μg/L, respectively. The Laboratory has prepared and is implementing an "Interim Measures Work Plan" pursuant to a requirement from the NMED. Work Plan ObjectivesObjectives of the Interim Measures Work Plan include:
Potential Sources of Chromium ContaminationMultiple potential sources of chromium contamination have been identified, including electroplating, photoprocessing, and use as a corrosion inhibitor in cooling-tower systems. The highest chromium usage is believed to be associated with use in the cooling-tower system in TA-03 at the head of Sandia Canyon where potentially large volumes (potentially up to 37 lb/day) of chromate (the highly soluble/mobile form of chromium) were released along with large volumes of water. Extent of Contamination in Regional GroundwaterIn January and February 2006, 17 groundwater monitoring wells and three production wells surrounding R-28 were sampled for chromium speciation to refine our understanding of the forms of naturally occurring chromium and chromium contamination and to bound the extent of chromium contamination in the groundwater. Results showed that of the chromium present in the samples, 100% was in the hexavalent form. A background of approximately 3–5 µg/L hexavalent chromium is present beneath the Pajarito Plateau. No elevated chromium levels were detected in water-supply wells. Work Plan ScopeA series of investigation activities will be implemented in 2006. These activities will help determine the spatial extent, and fate and transport, of chromium contamination and support eventual remedy selection.
ScheduleThe initial phase of fieldwork began in May 2006. With the exception of ongoing groundwater monitoring, the majority of the fieldwork is expected to be complete by late summer–early fall of 2006. An investigation report and a work plan for the next phase will follow. Community Involvement, Information and AssistanceLANL is committed to gathering community input, involvement, and assistance in our groundwater monitoring program. Presentations and other communications venues on groundwater monitoring are available to interested persons.
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