Description: The primary purpose of the sediment collection was to obtain vertical profile information from several areas in which no data existed and/or to compare with existing data to demonstrate the mercury and metals deposition resulting from the Comstock-era release (i.e., beginning in the 1860s). The specific areas targeted in the field work were from the Lahontan Reservoir, Sheckler Lake, and downstream areas potentially impacted by the historic river flows prior to construction of Lahontan Reservoir. In 2015, the Carson River and Lahontan Reservoir were at historic low levels as a result of a four-year drought. This presented the agency access to collect sediment core samples from areas that were normally below the waterline. EPA’s principal study question was whether mercury is indeed sediment bound and that Lahontan Reservoir, since it construction in 1915, serves as a mercury sink. The secondary purpose of the sediment sampling effort was to collect a range of mercury concentrations for assessing field screening equipment using Thermal Decomposition, Amalgamation, and Atomic Absorption Spectrophotometry (See EPA SW7473) and comparing the results to laboratory analytical data. The EPA is publishing this data in support of the Carson River Mercury NPL Site in Nevada. Data was compiled and evaluated for the OU2 Remedial Investigation Report (EPA, 2017), which describes the nature and extent of contamination from the Site. The report contains the Human Health Risk Assessment and Ecological Risk Assessment. Literature and other source Hg data are summarized in the RI for surface waters, sediments, and biological tissues.
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