The current conceptual site model (CSM) includes data gaps related to the extent of mercury contamination throughout the site, as well as the presence of other metal contaminants in soil. This study focuses on three areas in OU01: the Six Mile Canyon Area in Dayton, NV, the California Pan Mill Area in Virginia City, NV, and the Sacramento Mill Area just north of Virginia City, NV. Surface and near surface soils with COC concentration greater than the project action limits present a potential risk for direct contact and soil migration. Data gaps exist in the understanding the sources, extent, and migration pathways of contaminants at this area and the applicability of the Incremental Sampling (IS) and (X-ray Fluorescence (XRF) approach to comply with the LTSRP. The project will address these data gaps through incremental sampling and real time XRF. Data was compiled and evaluated for the IS Study where field sample collection techniques were evaluated as part of this study using XRF. Sample processing included seiving, to compare ISM with the current LTSRP method based on four five-point composite samples per residential parcel. The goal to is to validate the CSM and improve the screening of vast areas of mercury-contaminated soils while continuing to evaluate the performance of X-ray fluorescence (XRF) instrumentation for the simultaneous analysis of mercury (Hg), lead (Pb) and arsenic (As) in soil affected by the mining operations associated with the Comstock Lode. however sample processing will be. The most effective processing and analytical techniques will be selected for use in a follow-up study which will evaluate field sample collection. It is anticipated that the most effective and efficient sampling and analysis techniques will be incorporated into future investigations for the Carson River area. General Comments: The location coordinates represent the center point of the Decision Unit (DU) as calculated by GIS. For DUs that cross roads or driveways (SMCD2 and SMCSCR-South) the midpoint may plot in the middle of the road. The center point for SMCCBS was selected manually due to the unusual shape of the DU. The calculated GIS center point falls outside of the DU. DU columns provided on each tab for easy sorting and QC check. It is not a critical data point since the DU name is embedded in the Sample ID. For Source Units (SU) samples, the DU column is N/A if the SU was located outside of a DU, this column is filled out if the SU was located inside of a DU. Date represents sample collection date. Tab-Specific Comments: XRF field results did not use unique Lab ID sample #s so left that column blank. Did not establish specific XRF reporting limits for this project. Manually added a “U” for the XRF ND samples to match the lab formats. Region 9 lab results for the XRF comparison samples: Left all the ICP metals in the database. R9 lab DMA data only reported Pb, As, Se, and Hg per the team decision. SPLP Extraction #2 results for the samples selected for leaching analysis - removed the rows that identify the extraction procedure and contained no lab data. SPLP Extraction #3 results for the samples selected for leaching analysis - removed the rows that identify the extraction procedure and contained no lab data. Notes column indicates this is DI water extraction.

The current conceptual site model (CSM) includes data gaps related to the extent of mercury contamination throughout the site, as well as the presence of other metal contaminants in soil. This study focuses on three areas in OU01: the Six Mile Canyon Area in Dayton, NV, the California Pan Mill Area in Virginia City, NV, and the Sacramento Mill Area just north of Virginia City, NV. Surface and near surface soils with COC concentration greater than the project action limits present a potential risk for direct contact and soil migration. Data gaps exist in the understanding the sources, extent, and migration pathways of contaminants at this area and the applicability of the Incremental Sampling (IS) and (X-ray Fluorescence (XRF) approach to comply with the LTSRP. The project will address these data gaps through incremental sampling and real time XRF. Data was compiled and evaluated for the IS Study where field sample collection techniques were evaluated as part of this study using XRF. Sample processing included seiving, to compare ISM with the current LTSRP method based on four five-point composite samples per residential parcel. The goal to is to validate the CSM and improve the screening of vast areas of mercury-contaminated soils while continuing to evaluate the performance of X-ray fluorescence (XRF) instrumentation for the simultaneous analysis of mercury (Hg), lead (Pb) and arsenic (As) in soil affected by the mining operations associated with the Comstock Lode. however sample processing will be. The most effective processing and analytical techniques will be selected for use in a follow-up study which will evaluate field sample collection. It is anticipated that the most effective and efficient sampling and analysis techniques will be incorporated into future investigations for the Carson River area. General Comments: The location coordinates represent the center point of the Decision Unit (DU) as calculated by GIS. For DUs that cross roads or driveways (SMCD2 and SMCSCR-South) the midpoint may plot in the middle of the road. The center point for SMCCBS was selected manually due to the unusual shape of the DU. The calculated GIS center point falls outside of the DU. DU columns provided on each tab for easy sorting and QC check. It is not a critical data point since the DU name is embedded in the Sample ID. For Source Units (SU) samples, the DU column is N/A if the SU was located outside of a DU, this column is filled out if the SU was located inside of a DU. Date represents sample collection date. Tab-Specific Comments: XRF field results did not use unique Lab ID sample #s so left that column blank. Did not establish specific XRF reporting limits for this project. Manually added a “U” for the XRF ND samples to match the lab formats. Region 9 lab results for the XRF comparison samples: Left all the ICP metals in the database. R9 lab DMA data only reported Pb, As, Se, and Hg per the team decision. SPLP Extraction #2 results for the samples selected for leaching analysis - removed the rows that identify the extraction procedure and contained no lab data. SPLP Extraction #3 results for the samples selected for leaching analysis - removed the rows that identify the extraction procedure and contained no lab data. Notes column indicates this is DI water extraction.

This dataset contains final results for XRF and select laboratory results for the 2019 Carson River Mercury Site Incremental Sampling Field Study. Incremental samples were collected from three separate areas within the CRMS: Six Mile Canyon Area near Mark Twain, NV; California Pan Mill in Virginia City, NV; and Sacramento Mill in Virginia City, NV. The purpose of the data collection was to help characterize the extent of Hg, Pb, and As in surface (0 to 6-inch) and in some locations subsurface (0 to 24-inch) soils in the three study areas. A secondary purpose of the study was to demonstrate incremental sampling techniques and field XRF analysis to EPA Region 9 and NDEP Staff. The XRF results columns in the attribute table were generated by XRF data collected in accordance with the EPA-Approved Quality Assurance Project Plan and are considered definitive results suitable for project decisions. 30-point incremental samples were sieved to the 100-mesh fraction, placed “interference free” XRF read bags, and analyzed with EPA Headquarters’ Niton XRF. At least two XRF measurements were collected on each side of the bag resulting in at least four readings that were used to calculate the sample bag average that appears in the XRF Results columns for Hg, Pb, and As. If triplicate results were collected for a given sample, the mean is reported in the XRF Results columns for Hg, Pb, and As and the results for each of the three replicates are detailed in the XRF Notes column.

This dataset contains final results for XRF and select laboratory results for the 2019 Carson River Mercury Site Incremental Sampling Field Study. Incremental samples were collected from three separate areas within the CRMS: Six Mile Canyon Area near Mark Twain, NV; California Pan Mill in Virginia City, NV; and Sacramento Mill in Virginia City, NV. The purpose of the data collection was to help characterize the extent of Hg, Pb, and As in surface (0 to 6-inch) and in some locations subsurface (0 to 24-inch) soils in the three study areas. A secondary purpose of the study was to demonstrate incremental sampling techniques and field XRF analysis to EPA Region 9 and NDEP Staff. The XRF results columns in the attribute table were generated by XRF data collected in accordance with the EPA-Approved Quality Assurance Project Plan and are considered definitive results suitable for project decisions. 30-point incremental samples were sieved to the 100-mesh fraction, placed “interference free” XRF read bags, and analyzed with EPA Headquarters’ Niton XRF. At least two XRF measurements were collected on each side of the bag resulting in at least four readings that were used to calculate the sample bag average that appears in the XRF Results columns for Hg, Pb, and As. If triplicate results were collected for a given sample, the mean is reported in the XRF Results columns for Hg, Pb, and As and the results for each of the three replicates are detailed in the XRF Notes column.

The Region 9 CRMS risk assessor specifically identified the need to obtain data for Tribal lands near Fallon, Nevada. Based on a 1994 study performed on OU1 samples, an estimated 12% of total mercury measurements is mercuric chloride (HgCl2). The Quality Assurance Project Plan (QAPP) summarized the OU1 historical analytical approaches for “speciation” with currently available methods summarized. Based on team scoping meeting with EPA Region 10 and the Region 9 Toxicologist, use of the Brooks Applied Lab (BRL) sequential extraction was selected primarily for reasons of comparability of approaches to simplify data assessment. (EPA Method 3200 was presented for comparative purposes.) There are significant sources of uncertainty in “speciation” using any approach, as each is technically a procedurally defined fractionation that may include other mercury species not specifically identified. As an example of this uncertainty, under the OU1 study of the EPA Las Vegas Lab data, it was unclear which fraction would have captured mercury oxide or whether the residual chlorides caused minor amounts of sulfide to combine with the nitric acid fraction. While the Oak Ridge approach may have reported mercuric chloride in the elemental mercury fraction. The primary factors driving the need for this speciation data were uncertainty about the quality of the historical OU1 data; applicability of the OU1 data at the locations below Lahontan Reservoir, and concerns expressed by the Region 9 CRMS risk assessor to better obtain direct measurement data near the Fallon Paiute-Shoshone Tribe. The data generated by this sampling were reviewed for laboratory quality control but decisions with the data were made by the EPA Region 9 CRMS risk assessor.

EPA collected data in 2008 to evaluate the transport of mercury-contaminated water and sediment in the Carson River System in western Nevada. This report summarizes the analytical and field results from a pilot investigation performed to assess mercury contamination. Understanding the sources and transformations of mercury aided in planning future RI activities and pilot studies to assess mercury fate and transport in the Carson River and the Lahontan Reservoir. Soil samples from erosional banks along a 4-mile segment of the Carson River upstream of the Lahontan Reservoir were collected and analyzed in this pilot investigation to characterize mercury variability in exposed banks prone to erosion. This report presents the following information: Results of soil sampling and analysis, evaluation of data quality and compliance with the field sampling plan (FSP), discussion of the data, conclusions and recommendations for further study. 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.

EPA collected data in 2008 to evaluate the transport of mercury-contaminated water and sediment in the Carson River System in western Nevada. This report summarizes the analytical and field results from a pilot investigation performed to assess mercury contamination. Understanding the sources and transformations of mercury aided in planning future RI activities and pilot studies to assess mercury fate and transport in the Carson River and the Lahontan Reservoir. Soil samples from erosional banks along a 4-mile segment of the Carson River upstream of the Lahontan Reservoir were collected and analyzed in this pilot investigation to characterize mercury variability in exposed banks prone to erosion. This report presents the following information: Results of soil sampling and analysis, evaluation of data quality and compliance with the field sampling plan (FSP), discussion of the data, conclusions and recommendations for further study. 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.

The Region 9 CRMS risk assessor specifically identified the need to obtain data for Tribal lands near Fallon, Nevada. Based on a 1994 study performed on OU1 samples, an estimated 12% of total mercury measurements is mercuric chloride (HgCl2). The Quality Assurance Project Plan (QAPP) summarized the OU1 historical analytical approaches for “speciation” with currently available methods summarized. Based on team scoping meeting with EPA Region 10 and the Region 9 Toxicologist, use of the Brooks Applied Lab (BRL) sequential extraction was selected primarily for reasons of comparability of approaches to simplify data assessment. (EPA Method 3200 was presented for comparative purposes.) There are significant sources of uncertainty in “speciation” using any approach, as each is technically a procedurally defined fractionation that may include other mercury species not specifically identified. As an example of this uncertainty, under the OU1 study of the EPA Las Vegas Lab data, it was unclear which fraction would have captured mercury oxide or whether the residual chlorides caused minor amounts of sulfide to combine with the nitric acid fraction. While the Oak Ridge approach may have reported mercuric chloride in the elemental mercury fraction. The primary factors driving the need for this speciation data were uncertainty about the quality of the historical OU1 data; applicability of the OU1 data at the locations below Lahontan Reservoir, and concerns expressed by the Region 9 CRMS risk assessor to better obtain direct measurement data near the Fallon Paiute-Shoshone Tribe. The data generated by this sampling were reviewed for laboratory quality control but decisions with the data were made by the EPA Region 9 CRMS risk assessor.

EPA evaluated the total mercury representative of several surface and subsurface locations in OU1 for the purpose of the Human Health Risk Assessment investigation. EPA published this data in support of the Carson River Mercury NPL Site in Nevada. Data was compiled and evaluated for the OU1 Remedial Investigation Report (EPA, 1994), which describes the nature and extent of contamination from the Site. The reports contain the Human Health Risk Assessment and Ecological Risk Assessment Reports. Literature and other source Hg data are summarized in the RI report for upland source areas.

This feature class is converted from GPS coordinates obtained using a GPSmap 60CSx unit from Garmin in the field by AEI Consultants. The attribute information is filled with contaminant (Arsenic, Lead, Mercury) concentrations of soils derived from the Shallow Subsurface Investigation provided by AEI Consultants dated on January 11, 2013. Source documents; AEI Consultants, Peter J. McIntyre, C.E.M., October 16, 2012, Draft Phase II Subsurface Investigation Work Plan Carson River Estates, Dayton, Nevada, report to Jack Yates, NDEP, Unpublished, AEI Consultants, Bryan Campbell, Program Manager, October 31, 2012, Identification of Revisions to the Draft Phase II Subsurface Investigation Work Plan Carson River Estates, Dayton, Nevada date October 16, 2012, Electronic mail correspondence to Jeff Collins, NDEP, Unpublished, AEI Consultants, Peter J. McIntyre, C.E.M., January 11, 2013, Shallow Subsurface Investigation, Property Identification: Carson River Estates, Dayton, Nevada, report to Chris Carlson, Sr. Vice-President, City National Bank, Unpublished.