This data-release component documents chemical analyses of soil samples collected by the U.S. Geological Survey (USGS) in Lakeport (Lake County, California) on July 12, 2022. Environmental samples were collected at selected sites in Lakeport to assess the effects of lead-based paint on soil chemistry. This sampling was made as part of a broader study to attribute sources of lead in soils in cooperation with the California Department of Toxic Substances Control (DTSC) for their Lead-Acid Battery Recycling Facility Investigation and Cleanup (LABRIC) program. A total of five soil samples plus one replicate across four properties were collected proximal to selected structures suspected to have legacy coatings of lead-based paint. This component of the data release contains two tab-delimited text files and associated metadata describing results. The Lakeport_soils.txt file contains results of soil chemical analyses for individual soil samples sieved to three size fractions (less than 2 millimeters [mm], 0.063 mm to 0.25 mm, and less than 0.063 mm). Concentrations of elements included in this data release analyzed by inductively coupled plasma mass spectrometry or optical-emission spectrometry after multi-acid digestion include: aluminum, calcium, iron, potassium, magnesium, sodium, sulfur, titanium, silver, arsenic, barium, beryllium, bismuth, cadmium, cerium, cobalt, cesium, copper, gallium, indium, lithium, manganese, molybdenum, niobium, nickel, phosphorus, lead, rubidium, antimony, scandium, selenium, tin, strontium, tantalum, tellurium, thorium, thallium, uranium, vanadium, tungsten, and zinc. The Lakeport_soils_replicates.txt file contains comparison results for the aforementioned three size fractions for one of the soils that was sampled in duplicate.

This data release documents chemical analyses of environmental samples collected by the U.S. Geological Survey (USGS) in Lakeport (Lake County, California) during July 11-12, 2022. Environmental samples were collected at selected sites to assess the effects of lead-based paint on soil chemistry. This sampling was made as part of a broader study to attribute sources of lead in soils in cooperation with the California Department of Toxic Substances Control (DTSC) for their Lead-Acid Battery Recycling Facility Investigation and Cleanup (LABRIC) program. Results of soil sampling and chemical analyses are included in the data-release component entitled "Soils chemistry from selected sites in Lakeport, Lake County, California" linked below. Results of paint-chip screening data and associated quality control are included in the data-release component entitled "Field portable X-ray fluorescence and associated quality-control data for paint chips sampled from selected sites in Lakeport, Lake County, California" linked below. This study would not have been possible without volunteers who provided field support and allowed access to sample sites. First release: July, 2023 Revision 1.1: August, 2023

This data release documents chemical analyses of environmental samples collected by the U.S. Geological Survey (USGS) in Lakeport (Lake County, California) during July 11-12, 2022. Environmental samples were collected at selected sites to assess the effects of lead-based paint on soil chemistry. This sampling was made as part of a broader study to attribute sources of lead in soils in cooperation with the California Department of Toxic Substances Control (DTSC) for their Lead-Acid Battery Recycling Facility Investigation and Cleanup (LABRIC) program. Results of soil sampling and chemical analyses are included in the data-release component entitled "Soils chemistry from selected sites in Lakeport, Lake County, California" linked below. Results of paint-chip screening data and associated quality control are included in the data-release component entitled "Field portable X-ray fluorescence and associated quality-control data for paint chips sampled from selected sites in Lakeport, Lake County, California" linked below. This study would not have been possible without volunteers who provided field support and allowed access to sample sites. First release: July, 2023 Revision 1.1: August, 2023

This data release documents chemical analyses of environmental samples collected by the U.S. Geological Survey (USGS) in Lakeport (Lake County, California) during July 11-12, 2022. Environmental samples were collected at selected sites to assess the effects of lead-based paint on soil chemistry. This sampling was made as part of a broader study to attribute sources of lead in soils in cooperation with the California Department of Toxic Substances Control (DTSC) for their Lead-Acid Battery Recycling Facility Investigation and Cleanup (LABRIC) program. Results of soil sampling and chemical analyses are included in the data-release component entitled "Soils chemistry from selected sites in Lakeport, Lake County, California" linked below. Results of paint-chip screening data and associated quality control are included in the data-release component entitled "Field portable X-ray fluorescence and associated quality-control data for paint chips sampled from selected sites in Lakeport, Lake County, California" linked below. This study would not have been possible without volunteers who provided field support and allowed access to sample sites. First release: July, 2023 Revision 1.1: August, 2023

This dataset includes geochemical, isotopic, and particle-size data for soil and sediment samples collected at approximately 500 sites in the Clear Lake drainage basin, Lake County, California, between November 2021 and December 2023. Data are also reported for ten soil samples collected during October 2018 soon after the Ranch Fire in the upper Scotts Creek watershed. Samples of lakebed sediment (top four centimeters (cm)) were collected at 26 locations in Clear Lake in September 2023 using an Eckman dredge. Samples collected in tributary watersheds included soils, roadside ditches, streambed sediment, and stream-side sediment (including streambanks, floodplain deposits, colluvium, or alluvium). Some of the streambed sites were sampled on multiple occasions, including a monthly time series during July to December 2023. For 589 samples, the size fraction sieved to less than 0.063 millimeter (mm) was analyzed for the following parameters: 61 elements determined by inductively coupled plasma methods, low-level mercury by cold-vapor atomic absorption spectroscopy, total sulfur and carbon by combustion methods, carbonate carbon, stable isotopes of carbon and nitrogen, total organic carbon, total organic nitrogen, and particle-size distribution. A suite of 101 samples (preserved frozen in the field) was analyzed for nutrient species (forms of phosphorus and nitrogen) as well as particle-size distribution. Version History Summary: First Published: March 2025 Version 2.0: August 2025

The Sulphur Bank Mercury Mine in Lake County, California, was the site of historical mercury mining from 1880s through 1973.Since 1990, the mine area has been a Superfund site managed by the U.S. Environmental Protection Agency (USEPA). As part of a Remedial Investigation, the USEPA and the U.S. Geological Survey (USGS) are collaborating on a groundwater investigation in a part of the Sulphur Bank mine site known as the Waste Rock Dam (WRD) area, which lies between Herman Impoundment (a flooded mine pit) and Clear Lake. 33 groundwater wells were sampled in the WRD area and adjacent areas of the mine site by USEPA and their consultants in six sampling events during 2022-23. Because of low water levels due to drought conditions in 2022, some wells could not be sampled. Surface water was sampled from Herman Impoundment and Clear Lake during all six sampling events, and surface water from the Northwest Pit was sampled during one event. This data release includes field and laboratory data for 295 environmental samples and 42 QA samples collected during these sampling events. Field parameters include water temperature, specific conductance, dissolved oxygen, turbidity, pH, and oxidation-reduction potential. Laboratory analyses include major cations, trace metals, mercury, anions (sulfate, chloride, bromide, and fluoride), alkalinity, forms of nitrogen (nitrate plus nitrite, and ammonium), and stable isotopes of hydrogen and oxygen in water, and of sulfur and oxygen in aqueous sulfate.

Multiple sources of mine drainage including discharge from the abandoned Dinero mine tunnel and two gulches flow into a wetland, known herein as the Dinero wetland along the Lake Fork Creek corridor. The Dinero wetland is approximately 20 acres in extent. The Dinero wetland is being considered as a location for passive treatment of the mine drainage flowing through it. As such, study objectives are to understand: (1) variations in pH, specific conductance, and temperature in surface water in the wetland; (2) metal loading into and out of the wetland; (3) the configuration of surface drainage features; (4) the configuration of subsurface conductive features; and (4) depth to bedrock in the wetland. These data will be used to help understand whether the wetland is currently and naturally treating the mine drainage flowing through it and will help pinpoint locations needing additional investigations to help inform potential passive treatment scenarios. Water quality field parameters (temperature, pH, specific conductance, and dissolved oxygen) were measured in the Dinero wetland complex downstream from Sugarloaf gulch, Little Sugarloaf gulch, and Dinero tunnel discharge and locations near and directly at the Nelson tunnel discharge in June 2024. Data were collected from multiple points at existing surface-water drainage channels and at upwelling groundwater/spring locations. A geographic information system was used to prepare maps of the four different parameters to help understand variation in these parameters across the Dinero wetland complex. Waters originating at Nelson Tunnel, Sugarloaf Gulch, and Little Sugarloaf Gulch had depressed pH, elevated specific conductance, and mixed dissolved oxygen and temperature signatures. Waters originating from Dinero tunnel had near neutral pH, moderate temperatures, and elevated specific conductance and dissolved oxygen values. Samples in the northern portion of the wetland had lower specific conductance and dissolved oxygen and greater pH than samples in other portions of the wetland. Temperatures of these sites were generally moderate compared to those in other portions of the wetland. Spring samples had values generally within the range of values for each parameter.

The data herein were collected in support of a larger study in Gwinnett County, Georgia, on the potential impacts of on-site waste water treatment (septic systems) on Lake Lanier water quality. Until recently, a missing component in this assessment was the inclusion of historical sediment and associated nutrient accumulation data from the lake to place results in a broader context. To this end, the USGS collected sediment cores from ten locations that varied in water depth as well as proximity to residential areas with septic systems. Samples were collected using either a gravity corer or box corer depending on site conditions. Cores were sub-sampled and processed for laboratory analyses. Laboratory analyses were conducted to evaluate nutrient concentrations (carbon, nitrogen, and phosphorus) in sediments, stable isotope ratios of carbon and nitrogen in the sediment organic matter, cesium-137 for select samples, and trace and heavy metals. The latter constituents (cesium-137 and trace and heavy metals) were used primarily to help constrain mass accumulations rates (MAR) and assign ages to each sub-sample so that temporal changes in nutrient concentrations could be evaluated in concert with timing of shoreline development. Version 2.0 adds three new data files: 1) information linking specific replicate sediment cores to specific laboratory analyses, 2) activities of five radioisotopes (cesium-137, lead-210, radium-226, thorium-234, and potassium-40), and 3) the concentration of biogenic silica of sediment samples from all 10 coring sites. This revision also corrects a shift in the latitude and longitude of the coring sites.

The data herein were collected in support of a larger study in Gwinnett County, Georgia, on the potential impacts of on-site waste water treatment (septic systems) on Lake Lanier water quality. Until recently, a missing component in this assessment was the inclusion of historical sediment and associated nutrient accumulation data from the lake to place results in a broader context. To this end, the USGS collected sediment cores from ten locations that varied in water depth as well as proximity to residential areas with septic systems. Samples were collected using either a gravity corer or box corer depending on site conditions. Cores were sub-sampled and processed for laboratory analyses. Laboratory analyses were conducted to evaluate nutrient concentrations (carbon, nitrogen, and phosphorus) in sediments, stable isotope ratios of carbon and nitrogen in the sediment organic matter, cesium-137 for select samples, and trace and heavy metals. The latter constituents (cesium-137 and trace and heavy metals) were used primarily to help constrain mass accumulations rates (MAR) and assign ages to each sub-sample so that temporal changes in nutrient concentrations could be evaluated in concert with timing of shoreline development. Version 2.0 adds three new data files: 1) information linking specific replicate sediment cores to specific laboratory analyses, 2) activities of five radioisotopes (cesium-137, lead-210, radium-226, thorium-234, and potassium-40), and 3) the concentration of biogenic silica of sediment samples from all 10 coring sites. This revision also corrects a shift in the latitude and longitude of the coring sites.

The California State Water Resources Control Board (State Water Board) initiated the Oil and Gas Regional Monitoring Program (RMP) to assess effects of oil and gas development on groundwater designated for any beneficial use. The U.S. Geological Survey (USGS) is the technical lead in conducting the RMP through the California Oil, Gas, and Groundwater (COGG) Program, working in cooperation with the State Water Board, and in partnership with other State and local agencies. The USGS collected and analyzed groundwater (GW) and surface water (SW) for the San Ardo Oil Field study area, the area within the San Ardo Oil Field administrative boundary and the surrounding five-kilometer buffer zone, in Monterey County, California. Eighteen groundwater, two stream, and two spring samples were collected from March 2019 through May 2021. Groundwater samples were collected from one public-supply well, five monitoring wells, two irrigation wells, one livestock well, five oil-field water supply wells, and four domestic wells. Samples were collected using established water data-collection protocols and procedures and analyzed for (1) water-quality indicators, (2) major and minor ions, (3) nutrients, (4) trace elements, (5) volatile organic compounds (VOCs), (6) naturally-occurring radioactive material (radium isotopes), (7) geochemical and age-dating tracers, (8) dissolved organic carbon (DOC), (9) dissolved standard and hydrocarbon gases (methane through hexane), and (10) dissolved noble gases and atmospheric gases. In total, 185 constituents, water-quality indicators, or properties are included in this data release. Quality-control (QC) samples were used to assess the quality of laboratory results.