Location of sample points and analytical results for mercury concentrations from a soil survey.

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.

Sediment cores were collected in the Cache Creek Settling Basin (CCSB), Yolo County, California, during October 2011 at 10 locations (borehole sites) and during August 2012 at 5 other locations. Total core depths ranged from approximately 4.6 to 13.7 meters (15 to 45 feet), with penetration to about 9.1 meters (30 feet) at most locations. Detailed subsampling (3-centimeter intervals) was done at total of seven locations: six along an east-west transect in the southern part of the Cache Creek Settling Basin and at one in the northern part of the basin for analyses of total mercury; organic content; and cesium-137, which was used for dating. This data release reports results of the analyses of each subsample of these sediment cores, including associated quality-assurance and quality-control data.

Sediment cores were collected in the Cache Creek Settling Basin (CCSB), Yolo County, California, during October 2011 at 10 locations (borehole sites) and during August 2012 at 5 other locations. Total core depths ranged from approximately 4.6 to 13.7 meters (15 to 45 feet), with penetration to about 9.1 meters (30 feet) at most locations. Detailed subsampling (3-centimeter intervals) was done at total of seven locations: six along an east-west transect in the southern part of the Cache Creek Settling Basin and at one in the northern part of the basin for analyses of total mercury; organic content; and cesium-137, which was used for dating. This data release reports results of the analyses of each subsample of these sediment cores, including associated quality-assurance and quality-control data.

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.

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. For more information on soil sampling field procedures, refer to the following 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. Note: Generally, five composite sample points are respectively collected at the front and backyard in one parcel. However errors occurred in two parcels: APN=2952402 and APN=2952202. In the parcel 2952402, there are nine sample points. The other sample point (Sample ID=524-02-05) is found at the parcel 2952202 and overlied with one sample points (Sample ID=522-02-04) of the parcel 2952202. According to checking the Shallow Subsurface Investigation provided by AEI Consultants dated on January 11, 2013, the originial GPS coordinates of both sample points (Sample ID=524-02-05 and Sample ID=522-02-04) are the same.

This is a summary of mercury (Hg) data from the Lahontan Reservoir area of the Carson River Basin. USBR provided an information overview and reference source on mercury (Hg) in soils for water resources managers and researchers working in the Carson River Basin. These data and the data tables provide results of the Lahontan Reservoir area, focused on the camp sites and the beaches, in order to measure concentrations of Hg to evaluate potential human health exposure pathways. The original sources of Hg contamination in the Carson River Basin are from historic gold and silver mining and associated milling of the Comstock Lode near Virginia City, Nevada. Runoff and erosion from an estimated 236 'stamp mills', driven by flumes, resulted in a cummulative release of an estimated 7,500 Tons of elemental mercury into the Carson River Basin. The elemental mercury, imported from mines in California and used to almalgamate the ore at the stamp mills, contaminated sediments throughout the Basin from the source area situated approximately between Carson City and Dayton, to the terminal wetlands in the Carson Sink. This area is the primary source of Hg pollution in the Basin, considering the naturally occurring mercury concentrations are close to the crustal average. During runoff and flood events, the River laterally cuts through the contaminated sediments in the overbanks and transports Hg with suspended sediments, and with concentrations rising with higher flow. When Lahontan Reservoir was built in 1915, it became a settling basin for suspended Hg from the Carson River, and while it retains up to 90 percent of influent sediments, the reservoir continues to pass significant concentrations of suspended and dissolved inorganic Hg and methylmercury (Me-Hg) downstream to the Carson Sink. 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. Literature and other source Hg data are summarized in the RI, for surface waters, sediments, and biological tissues. The report contains the Human Health Risk Assessment and Ecological Risk Assessment.

This is a summary of mercury (Hg) data from the Lahontan Reservoir area of the Carson River Basin. USBR provided an information overview and reference source on mercury (Hg) in soils for water resources managers and researchers working in the Carson River Basin. These data and the data tables provide results of the Lahontan Reservoir area, focused on the camp sites and the beaches, in order to measure concentrations of Hg to evaluate potential human health exposure pathways. The original sources of Hg contamination in the Carson River Basin are from historic gold and silver mining and associated milling of the Comstock Lode near Virginia City, Nevada. Runoff and erosion from an estimated 236 'stamp mills', driven by flumes, resulted in a cummulative release of an estimated 7,500 Tons of elemental mercury into the Carson River Basin. The elemental mercury, imported from mines in California and used to almalgamate the ore at the stamp mills, contaminated sediments throughout the Basin from the source area situated approximately between Carson City and Dayton, to the terminal wetlands in the Carson Sink. This area is the primary source of Hg pollution in the Basin, considering the naturally occurring mercury concentrations are close to the crustal average. During runoff and flood events, the River laterally cuts through the contaminated sediments in the overbanks and transports Hg with suspended sediments, and with concentrations rising with higher flow. When Lahontan Reservoir was built in 1915, it became a settling basin for suspended Hg from the Carson River, and while it retains up to 90 percent of influent sediments, the reservoir continues to pass significant concentrations of suspended and dissolved inorganic Hg and methylmercury (Me-Hg) downstream to the Carson Sink. 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. Literature and other source Hg data are summarized in the RI, for surface waters, sediments, and biological tissues. The report contains the Human Health Risk Assessment and Ecological Risk Assessment.

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. For more information on soil sampling field procedures, refer to the following 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. Note: Generally, five composite sample points are respectively collected at the front and backyard in one parcel. However errors occurred in two parcels: APN=2952402 and APN=2952202. In the parcel 2952402, there are nine sample points. The other sample point (Sample ID=524-02-05) is found at the parcel 2952202 and overlied with one sample points (Sample ID=522-02-04) of the parcel 2952202. According to checking the Shallow Subsurface Investigation provided by AEI Consultants dated on January 11, 2013, the originial GPS coordinates of both sample points (Sample ID=524-02-05 and Sample ID=522-02-04) are the same.

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. For more information on soil sampling field procedures, refer to the following 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. Note: Generally, five composite sample points are respectively collected at the front and backyard in one parcel. However errors occurred in two parcels: APN=2952402 and APN=2952202. In the parcel 2952402, there are nine sample points. The other sample point (Sample ID=524-02-05) is found at the parcel 2952202 and overlied with one sample points (Sample ID=522-02-04) of the parcel 2952202. According to checking the Shallow Subsurface Investigation provided by AEI Consultants dated on January 11, 2013, the originial GPS coordinates of both sample points (Sample ID=524-02-05 and Sample ID=522-02-04) are the same.