Groundwater Sites Evaluated to Assess The Vulnerability of Public Supply Wells To Increasing Arsenic Concentrations In Southeastern Carson Valley, Douglas County, Nevada

Dates

Publication Date: 2017-07-11
Start Date: 1956-12-19
End Date: 2016-09-08

Citation

Paul, A.P., Welborn, T.L., and Naranjo, R.C., 2017, Groundwater Sites Evaluated to Assess The Vulnerability of Public Supply Wells To Increasing Arsenic Concentrations In Southeastern Carson Valley, Douglas County, Nevada: U.S. Geological Survey data release, https://doi.org/10.5066/F75B00Z5.

Summary

Over the past 15 years Douglas County, NV has removed production wells in northern Carson Valley from use due to relatively high arsenic concentrations (Carl Ruschmeyer, January 2013, Douglas County Public Works Director, verbal communication). To maintain the supply of water to the public, the town of Minden has been providing water to Douglas County and Carson City. Due to the projected increases in municipal demand, water resource managers are concerned that increasing pumping rates from wells in Minden may change groundwater chemistry and degrade the resource by potentially drawing in arsenic enriched water. Naturally occurring arsenic is one of the most common contaminants in groundwater in the western United States. Arsenic [...]

Summary

Over the past 15 years Douglas County, NV has removed production wells in northern Carson Valley from use due to relatively high arsenic concentrations (Carl Ruschmeyer, January 2013, Douglas County Public Works Director, verbal communication). To maintain the supply of water to the public, the town of Minden has been providing water to Douglas County and Carson City. Due to the projected increases in municipal demand, water resource managers are concerned that increasing pumping rates from wells in Minden may change groundwater chemistry and degrade the resource by potentially drawing in arsenic enriched water.

Naturally occurring arsenic is one of the most common contaminants in groundwater in the western United States. Arsenic found in basin-fill aquifers is oftentimes associated with alluvial/lacustrine sedimentary deposits derived from the weathering of volcanic rocks and geothermal waters (Welch and others, 1988). The primary aquifers beneath Carson Valley are comprised of quaternary aged basin-fill deposits of weathered granitic and volcanic material (Welch, 1994). Factors contributing to increasing arsenic concentrations in groundwater include, but are not limited to, proximity to arsenic bearing rocks, relatively long groundwater flow paths, the application of phosphate containing fertilizers, and leaching from soils in irrigated areas (Busbee and others, 2009; Anning and others, 2012). The vulnerability of groundwater resources to contamination is influenced by the physical properties of the aquifer, pumping rates, locations of wells and screened intervals relative to the groundwater flow system, and geochemical environment (Focazio and others, 2002). Arsenic mobility and transport through the subsurface is largely controlled by the interaction of groundwater with aquifer sediments. Arsenite (As(III)), the reduced form of inorganic arsenic, usually exhibits greater mobility in groundwater than the oxidized form, arsenate (As(V)) largely due to the greater attraction of As(V) to aquifer sediments relative to that of As(III) at pH values exceeding 8.5 (Smedley and Kinniburgh, 2002). Arsenic speciation (form) is influenced by the relative redox condition of the aquifer environment. For example, in the vicinity of the Douglas County Airport, where arsenic speciation has been characterized, arsenic in groundwater collected at depths greater than 250 feet below land surface was found to be primarily As(III); however, in the upper 150 feet of the aquifer As(V) predominated (Paul and others, 2010).

This data set provides a spatial and temporal assessment of available chemical and physical data from local, county, state, and federal databases for the Carson Valley, near Minden, Nevada. Critical data gaps will be identified and, if necessary, additional sample collection and monitoring under conditions of routine groundwater pumping from both municipal and agricultural supply wells will be suggested. Data included as part of this data set, are data provided by the USGS and Carson Valley water purveyors with the support of the Carson Water Subconservancy District and Nevada Division of Environmental Protection to evaluate arsenic mobility and transport in Carson Valley. The data summarized and included in this release are water quality samples and water-level observations.

Anning, D.W., Paul, A.P., McKinney, T.S., Huntington, J.M., Bexfield, L.M., Thiros, S.A., 2012, Predicted nitrate and arsenic concentrations in basin-fill aquifers of the Southwestern United States: U.S. Geological Survey Scientific-Investigations Report 2012-5065, 78 p. and appendices;

Busbee, M.W., Kocar, B.D., Benner, S.G., 2009, Irrigation produces elevated arsenic in the underlying groundwater of a semi-arid basin in Southwestern Idaho: Applied Geochemistry, vol. 24, pp. 843-859;

Focazzio, M.J., Reilly, T.E., Rupert, M.G., Helsel, D.R., 2006, Assessing ground-water vulnerability to contamination: providing scientifically defensible information for decision makers: United States Geological Survey Circular 1224, 33 p.;

Paul, A.P., Maurer, D.K., Stollenwerk, K.G., Welch, A.H., 2010, In-situ arsenic remediation in Carson Valley, Douglas County, West-Central Nevada: U.S. Geological Survey Scientific-Investigations Report 2010-5161, 24 p.;

Smedley, P.L. and Kinniburgh, D.G., 2002, A review of the source, behavior and distribution of arsenic in natural waters: applied Geochemistry, v. 17, p. 517-568;

Welch, A.H., Lico, M.S.,Hughes, J.L., 1988, Arsenic in Ground Water of the Western United States, Ground Water, vol. 26, no. 3, pp. 333-347;

Welch, A.H., 1994, Ground-water quality and geochemistry in Carson and Eagle Valleys, Western Nevada and Eastern California: U.S. Geological Survey Open-File Report 93-33, 99 p.

Contacts

Point of Contact :: Angela P Paul
Originator :: Angela P Paul, Toby L Welborn, Ramon C Naranjo
Metadata Contact :: Angela P Paul
Publisher :: U.S. Geological Survey
Distributor :: U.S. Geological Survey - ScienceBase
USGS Mission Area :: Water Resources
SDC Data Owner :: Nevada Water Science Center

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Production Well Vulnerability to As in Carson Valley 2.xml Original FGDC Metadata	View	60.99 KB	application/fgdc+xml
tbl_ArsenicSites.txt		18.81 KB	text/plain
tbl_WaterLevelData.txt		826.31 KB	text/plain
tbl_WaterQualityData.txt		2.96 MB	text/plain
Presentation Arsenic in Carson Valley Data Summary.pdf		1.54 MB	application/pdf

Purpose

This data set was created as part of a U.S.Geological Survey study, done in cooperation with the Carson Water Subconservancy District, the Town of Minden, Douglas County, Gardnerville Water Company, Indian Hills General Improvement District, Gardnerville Ranchos General Imporvement District, South Tahoe Public Utility District, and the State of Nevada Division of Environmental Protection. The intended uses of this data set include, but are not limited to, natural resource modeling, mapping, and visualization applications.

Groundwater Sites Evaluated to Assess The Vulnerability of Public Supply Wells To Increasing Arsenic Concentrations In Southeastern Carson Valley, Douglas County, Nevada

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