Water chemistry data for samples collected at groundwater and surface-water sites in the San Ardo Oil Field study area, March 2019–May 2021, Monterey County, California

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.

加利福尼亚州水资源控制委员会（California State Water Resources Control Board）启动了油气区域监测计划（Oil and Gas Regional Monitoring Program，RMP），以评估油气开发对指定用于各类有益用途的地下水所产生的影响。美国地质调查局（U.S. Geological Survey，USGS）是该RMP的技术牵头方，通过加州油气与地下水项目（California Oil, Gas, and Groundwater，COGG）开展工作，与州水资源委员会协作，并与其他州级及地方机构结成合作伙伴关系。美国地质调查局在加利福尼亚州蒙特雷县的圣阿多油田研究区——即圣阿多油田行政边界范围及周边5公里缓冲带——采集并分析了地下水（GW）与地表水（SW）样本。2019年3月至2021年5月期间，共采集18组地下水样本、2组溪流样本及2组泉水样本。其中地下水样本取自1口公共供水井、5口监测井、2口灌溉井、1口畜牧用水井、5口油田供水井及4口民用井。样本采集严格遵循既定的水文数据采集规程与流程，检测分析内容涵盖：(1) 水质指标；(2) 常量与微量离子；(3) 营养盐；(4) 痕量元素；(5) 挥发性有机化合物（VOCs）；(6) 天然放射性物质（镭同位素）；(7) 地球化学与定年示踪剂；(8) 溶解性有机碳（DOC）；(9) 溶解性标准气体与烃类气体（甲烷至己烷）；(10) 溶解性稀有气体与大气气体。本次数据发布共包含185项组分、水质指标或物性参数。研究采用质量控制（QC）样本对实验室检测结果的可靠性进行评估。