Provenance

Every source on file

Each number on this site comes from one of the public datasets below. Pages name the source next to every figure, and this list shows how each was licensed and when it was last pulled.

• EGLE North Kent Study Area residential well PFAS results

  State of Michigan public data; no restrictions on use, reproduction or distribution (item license). Credit EGLE RRD, County of Kent, AECOM.. Retrieved September 22, 2026.

  Residential well PFAS results from the Michigan EGLE North Kent Study Area investigation, one row per sampled well with the highest reading per compound, April 2017 to present.

  EGLE sampled every residential well in a defined study area around known tannery waste disposal sites in northern Kent County, so these shares describe wells near a known source rather than every well in the township.

  ArcGIS layer Residential_Well_Sample. Values are per-well maxima in ng/L and can include the untreated influent of a whole-house filter; Non-Detect counts as zero; Not Analyzed is skipped. No sample dates in the layer; the period is the program's stated span. Shares are against the EPA limit (4 ng/L PFOA and PFOS, 10 ng/L PFHxS and PFNA).

• Ohio EPA Washington County residential well PFAS sampling

  Ohio EPA public GIS service; no restrictions stated, attribution given. Retrieved September 22, 2026.

  Residential well PFAS results from Ohio EPA's Washington County drinking water investigation (sampling by AECOM), published on the Ohio EPA GIS server.

  Ohio EPA sampled residential wells around the Chemours Washington Works site in Washington County, and wells with a detection are resampled quarterly. PFAS shares describe wells near a known source, not every well in the county.

  Layer 5, Washington County All Test Points. Raw well water only: treated-water locations (-PT, -Bed1, -Bed2, -AT suffixes), duplicates and rejected results are dropped. Four analytes kept of forty. ug/L converted to ng/L. Location ids are address-derived and stored only as a hash.

• Alaska DNR well log tracking system (WELTS)

  State of Alaska public data, no warranty; attribution given. Retrieved September 18, 2026.

  Well logs filed with the Alaska Department of Natural Resources (WELTS).

  Layer OpenData/NaturalResource_WELTS/MapServer/0 (40,722). WellUse Domestic is domestic (28,751 logs have no use recorded); WellDepth, StaticWaterDepth, DepthToBedrock in feet, PumpGPM; DateComplete is epoch milliseconds. Owner and parcel fields are not requested.

• South Dakota DANR well completion reports

  South Dakota DANR public data; attribution given. Retrieved September 18, 2026.

  Well completion reports filed with the South Dakota Department of Agriculture and Natural Resources.

  Layer NR68_WellLogs_Public/MapServer/0 (78,442). WELL_TYPE DOM is domestic; DEPTH in feet; staticValue when present; WELL_COMPL is epoch milliseconds. Owner and driller name fields are not requested.

• Delaware DNREC non-public well permits

  Delaware FirstMap public data; attribution given. Retrieved September 18, 2026.

  Non-public well permits and completion reports from the Delaware Department of Natural Resources and Environmental Control.

  FirstMap layer DE_DNREC_Monitoring_Network/MapServer/0 (174,806). WellType beginning Domestic is domestic; TotalDepthActual when above zero else TotalDepthProp; StaticWaterLevel and PumpTestRate when above zero; ActualConstructionDate is epoch milliseconds. Owner and tax parcel fields are not requested.

• Arkansas DEQ permitted sites

  State public data; attribution given. Retrieved September 18, 2026.

  Regulated storage tank, hazardous waste and solid waste permit sites from the Arkansas Division of Environmental Quality, through the Arkansas GIS Office.

• Nevada NDWR well driller reports

  Nevada DCNR open data; attribution given. Retrieved September 18, 2026.

  Well driller reports filed with the Nevada Division of Water Resources.

  ArcGIS layer NDWR/Well_Driller_Reports/FeatureServer/0 (145,794). ProposedUse Domestic is domestic; DepthDrilled, DepthBedrock, DepthCased, StaticWaterLevel in feet, yield in gpm; WellFinishDate is epoch milliseconds. Owner and parcel fields are not requested.

• Arizona ADWR well registry (Wells55)

  ADWR open data; attribution given. Retrieved September 18, 2026.

  Registered wells from the Arizona Department of Water Resources Wells55 registry.

  ArcGIS layer Well_Registry_2024/FeatureServer/0 (241,042). WELL_TYPE_GROUP EXEMPT (small wells under 35 gallons per minute, nearly all household) is domestic; WELL_DEPTH, WATER_LEVEL, CASING_DEPTH in feet, TESTEDRATE in gpm, INSTALLED is the completion date. Owner and cadastral fields are not requested.

• North Dakota solid waste facilities

  State public data; attribution given. Retrieved September 18, 2026.

  Permitted solid waste facilities from the North Dakota Department of Environmental Quality.

• RIDEM regulated facilities

  State public data; attribution given. Retrieved September 18, 2026.

  Leaking underground storage tanks, site remediation projects, closed landfills and active solid waste facilities from the Rhode Island Department of Environmental Management.

• Oregon DEQ active tank sites

  State public data; attribution given. Retrieved September 18, 2026.

  Active underground storage tank sites from the Oregon Department of Environmental Quality.

• Iowa DNR regulated sites

  State public data; attribution given. Retrieved September 18, 2026.

  Contaminated sites, solid waste facilities and leaking underground storage tank sites from the Iowa Department of Natural Resources.

• Kentucky waste landfill facilities

  State public data; attribution given. Retrieved September 18, 2026.

  Permitted landfill facilities from the Kentucky Energy and Environment Cabinet.

• CDPHE operating landfills

  State public data; attribution given. Retrieved September 18, 2026.

  Operating commercial landfills from the Colorado Department of Public Health and Environment.

• TDEC underground storage tank facilities

  State public data; attribution given. Retrieved September 18, 2026.

  Underground storage tank facilities from the Tennessee Department of Environment and Conservation.

• MDE Land Restoration Program sites

  State public data; attribution given. Retrieved September 18, 2026.

  Brownfield, voluntary cleanup and Superfund sites from the Maryland Department of the Environment Land Restoration Program.

• Alaska DEC contaminated sites

  State public data; attribution given. Retrieved September 18, 2026.

  Contaminated sites, including leaking tank sites, from the Alaska Department of Environmental Conservation.

• NMED storage tank facilities and landfills

  State public data; attribution given. Retrieved September 18, 2026.

  Underground storage tank facilities and permitted landfills from the New Mexico Environment Department.

• Montana DEQ regulated sites

  State public data; attribution given. Retrieved September 18, 2026.

  Petroleum tank releases, underground storage tank facilities and licensed solid waste facilities from the Montana Department of Environmental Quality.

• Oklahoma DEQ land sites

  State public data; attribution given. Retrieved September 18, 2026.

  Superfund sites, voluntary cleanup sites and solid waste facilities from the Oklahoma Department of Environmental Quality.

• Utah DEQ regulated sites

  State public data; attribution given. Retrieved September 18, 2026.

  Underground storage tank facilities, CERCLA site assessments and National Priorities List sites from the Utah Department of Environmental Quality.

• South Dakota DANR tank facilities and spills

  State public data; attribution given. Retrieved September 18, 2026.

  Regulated tank facilities and spill reports from the South Dakota Department of Agriculture and Natural Resources.

• DNREC leaking tank facilities

  State public data; attribution given. Retrieved September 18, 2026.

  Leaking underground storage tank facilities from the Delaware Department of Natural Resources and Environmental Control.

• NDEP corrective action release events

  State public data; attribution given. Retrieved September 18, 2026.

  Leaking tank and other release events under corrective action at the Nevada Division of Environmental Protection.

• ADEQ regulated sites

  State public data; attribution given. Retrieved September 18, 2026.

  Leaking underground storage tank sites and municipal landfills from the Arizona Department of Environmental Quality.

• Ohio DNR water well logs

  ODNR public data; general information, not for resale; attribution given. Retrieved September 17, 2026.

  Water well logs filed with the Ohio Department of Natural Resources Division of Water Resources since 1948.

  MapServer layer waterwells/0 (549,390 wells, nightly). WELL_USE DOMESTIC is domestic (417,876); TOTAL_DEPTH, BEDROCK_DEPTH, CASE_LENGTH, STATIC_WATER_LEVEL_FT in feet, TEST_RATE_GPM; AQUIFER_TYPE names the water-bearing unit and bedrock is inferred from a recorded bedrock depth above the well depth. COMPLETION_DATE is epoch milliseconds. Owner and street fields are not requested.

• Washington Ecology well construction reports

  Washington Ecology public data; attribution given. Retrieved September 17, 2026.

  Well construction reports filed with the Washington State Department of Ecology, water wells only, located at the quarter-quarter section.

  ArcGIS layer WR/FeatureServer/9 filtered to WellProjectType Water (about 165,000 of 1.19 million reports; the rest are borings, decommissioning and dewatering). Points sit at the quarter-quarter section centroid, good to about half a mile. CompletedDepth and StaticWaterLvl in feet, FlowRateGPM; WorkCompletionDate is epoch milliseconds. Use is not recorded; most cased water wells in the state are household, so domestic is marked for Water (Cased) reports. Owner and address fields are not requested.

• Virginia Energy DGMR water well records

  Virginia Energy public data; attribution given. Retrieved September 17, 2026.

  Water well records compiled by the Virginia Department of Energy, Geology and Mineral Resources program, mostly from driller logs filed before 1990.

  MapServer layer VA_Water_Wells/0 (19,937 wells; sparse for a state with over a million). TD, SWL and Yld in feet and gallons per minute; Comp_DT is epoch milliseconds; the Bedrock field is free text and not used. All rows are water wells; use is not recorded, so domestic is unknown and left null. Owner and driller fields are not requested.

• Washington Ecology facility interactions

  Washington Ecology public data; attribution given. Retrieved September 17, 2026.

  Toxics cleanup sites, spills and solid waste facilities from the Washington State Department of Ecology Facility/Site register.

• Virginia DEQ regulated sites

  Virginia DEQ public data; attribution given. Retrieved September 17, 2026.

  Petroleum releases and solid waste permits from the Virginia Department of Environmental Quality Environmental Data Mapper.

• Ohio EPA regulated sites

  Ohio EPA open data; attribution given. Retrieved September 17, 2026.

  Remediation sites, leaking underground storage tank releases (BUSTR) and landfills from the Ohio Environmental Protection Agency and the Division of State Fire Marshal.

• FDEP regulated sites

  Florida DEP open data; attribution given. Retrieved September 17, 2026.

  Petroleum contamination discharges and cleanup sites from the Florida Department of Environmental Protection.

• Michigan Wellogic well records

  EGLE public data; no reuse restriction stated, attribution given. Retrieved September 16, 2026.

  Water well records from Wellogic, the Michigan Department of Environment, Great Lakes, and Energy statewide well database.

  ArcGIS layer EGLE/DwOpenData/MapServer/3 filtered to WELL_TYPE HOSHLD (1,081,079 of 1,173,632 records). WELL_DEPTH, CASE_DEPTH, SWL and ROCK_TOP in feet; TEST_RATE is the pump test rate in gallons per minute, kept only when 500 or less; AQ_TYPE ROCK or DRIFT decides bedrock. Owner and address fields are not requested.

• Michigan EGLE regulated sites

  EGLE public data; no reuse restriction stated, attribution given. Retrieved September 16, 2026.

  Part 201 environmental contamination sites, underground storage tank facilities and Part 115 landfills from the Michigan Department of Environment, Great Lakes, and Energy.

• Connecticut well completion reports

  Public Domain (data.ct.gov). Retrieved September 16, 2026.

  Well completion reports filed online with the Connecticut Department of Consumer Protection since January 2021.

  Socrata CSV wphv-ux6v (about 8,200 reports). type_of_report Water Supply Well is domestic; depth_of_well, top_of_rock, casing_length, water_depth_from_surface in feet; yield_test_result in gallons per minute; date_of_boringabandonment is the completion date. Reports filed on paper before 2021 are not online. Owner and address fields are not requested.

• CT DEEP contaminated sites and landfills

  Public Domain (data.ct.gov); CT DEEP attribution. Retrieved September 16, 2026.

  Contaminated or potentially contaminated sites and solid waste landfills from the Connecticut Department of Energy and Environmental Protection.

• IDEM regulated sites

  Indiana public data, provided as is; attribution given. Retrieved September 16, 2026.

  Leaking underground storage tank sites and state cleanup sites from the Indiana Department of Environmental Management.

• NYSDEC water well completion reports

  New York open data; NYSDEC attribution. Retrieved September 16, 2026.

  Water well completion reports filed with the New York State Department of Environmental Conservation Water Well Contractor Program since 2000.

  ArcGIS layer Water_Wells/FeatureServer/28 (144,499 located wells; WELLTYPE, DEPTH, PUMPCAP). The Socrata copy has bedrock and casing depths but most rows lack coordinates, so the located layer is used. No completion date. Owner field is not requested.

• NYSDEC remediation sites

  New York open data; NYSDEC attribution. Retrieved September 16, 2026.

  State Superfund, brownfield, voluntary cleanup, RCRA and spill remediation sites from the New York State Department of Environmental Conservation Environmental Remediation Sites database.

• Pennsylvania Groundwater Information System (PaGWIS) wells

  Pennsylvania Geological Survey open data; attribution given. Retrieved September 16, 2026.

  Water well records from the Pennsylvania Groundwater Information System, Pennsylvania Geological Survey (DCNR).

  ArcGIS layer PAGWISWaterWells/FeatureServer/0 (662,556 points). Water_Use contains DOMESTIC for household wells (sometimes repeated, e.g. DOMESTIC,DOMESTIC); Bedrock_Reached Yes or No; Well_Depth, Bedrock_Depth_FT and Well_Yield_GPM. No completion date field. Address fields are not requested.

• MassDEP well completion reports

  MassDEP open data; provided as is, permission granted to copy and use. Retrieved September 16, 2026.

  Well completion reports filed with the Massachusetts Department of Environmental Protection, as published in the Well Location Viewer (April 2023 vintage).

  ArcGIS layer Well_Location_Viewer_Data_4_26_23/FeatureServer/0 (127,011 points, 1,000 per page). Fields are strings: Date_Drilled M/D/YYYY, Total_Depth_of_Well, Depth_to_Bedrock, Depth_to_Static_Water_Level, Yield. Well_Type Domestic is domestic. A well is bedrock when its depth passes the recorded bedrock depth. Address and driller fields are not requested.

• MassDEP regulated sites

  MassGIS public record; attribution given. Retrieved September 16, 2026.

  Chapter 21E release sites, solid waste landfills and underground storage tank facilities from the Massachusetts Department of Environmental Protection, through MassGIS.

• Penn State Agricultural Analytical Services Lab drinking water summaries

  Penn State College of Agricultural Sciences; no license text published, attribution given. Retrieved September 16, 2026.

  County summaries of private water samples tested by the Penn State Agricultural Analytical Services Laboratory since 2007, published by the College of Agricultural Sciences.

  These are samples homeowners paid to send to the Penn State lab, often because of a suspected problem, so shares above the limit run higher than a random survey would find.

  Counts are samples, not distinct wells. Shares are against the standard the lab prints: the EPA maximum contaminant level, or the secondary standard for iron, manganese and chloride. Lead is the first-draw result. Medians printed as 0.00 are stored as null because the lab rounds to two decimals.

• MassDEP Private Well PFAS Sampling Program

  MassDEP open data; provided as is, permission granted to copy and use. Retrieved September 16, 2026.

  Private well PFAS results from the Massachusetts Department of Environmental Protection free sampling program, 2020 to 2023, one anonymized row per well.

  MassDEP offered free PFAS tests to towns without public water and to wells near suspected sources such as landfills, fire stations and airports, so these shares describe the wells that took part rather than every well in town.

  Shares are against the EPA limit for each compound (4 ng/L for PFOA and PFOS, 10 ng/L for PFHxS and PFNA). Massachusetts applies its own PFAS6 standard of 20 ng/L to the sum of six compounds; that sum is not a contaminant page here. Zero means not detected.

• Missouri DNR certified well records

  Missouri DNR public data; no warranty, attribution given. Retrieved September 15, 2026.

  Well certification records from the Missouri Department of Natural Resources Wellhead Information Management System (WIMS), published through MSDIS.

  ArcGIS layer MO_Wells/FeatureServer/0 (MSDIS export of WIMS, 2022). WELL_TYPE Domestic is domestic; TOTAL_DPTH, SWL, WELL_YIELD and CASING_LEN are feet and gallons per minute; DATE_COMPL is epoch milliseconds. Depth to bedrock is not a field. Owner and address fields are not requested.

• Missouri DNR regulated sites

  Missouri DNR public data; no warranty, attribution given. Retrieved September 15, 2026.

  Permitted solid waste facilities, and leaking tank, underground tank and hazardous waste sites from the historical CARES potential contaminant site inventory, Missouri Department of Natural Resources.

• Missouri DHSS private well sampling summaries

  Missouri public data; no license text published, attribution given. Retrieved September 15, 2026.

  County summaries of private well samples analyzed by the Missouri State Public Health Laboratory, 2010 to 2023, published by the Missouri Department of Health and Senior Services.

  Missouri does not require private well testing, so these are samples homeowners chose to send to the state lab, often after a problem; shares above the limit run higher than a random survey would find.

  Counts are samples, not distinct wells. Shares are against the EPA maximum contaminant level, or the EPA secondary standard for chloride and iron. Counties with fewer than 20 samples are flagged unreliable by DHSS and are kept here with their counts so the threshold rule can judge them. Barium, sulfate and zinc layers exist but have no contaminant page yet.

• USGS national arsenic model (Ayotte 2017)

  Public domain (US federal government data). Retrieved September 15, 2026.

  County estimates of domestic well users with arsenic above 10 ug/L from the USGS national logistic regression model (Ayotte, Medalie and Qi, 2017), with private well population from the USGS 2015 county water-use compilation (Dieter and others, 2018).

  A geology, geochemistry and hydrology model fitted to 20,450 domestic well samples, not measurements in the county. The share is the modeled population above 10 ug/L over the county's self-supplied domestic population. Better at ruling arsenic out than at saying how high it is; treat a high share as a reason to test.

• Minnesota Well Index

  Minnesota Geospatial Commons; no use constraints. Retrieved September 15, 2026.

  Well construction records from the Minnesota Well Index (Minnesota Department of Health), non-public-supply wells.

  ArcGIS layer water_well_information_non_pws/1, paged 1000 per request. Use code DO is domestic; depth_comp is completed depth; depth2bdrk is depth to bedrock; swl is only a flag here, so static level is not stored. Owner and address fields are not requested.

• California GeoTracker and EnviroStor sites

  California open data (data.ca.gov, DTSC). Retrieved September 15, 2026.

  Leaking underground storage tank and cleanup sites from the State Water Board GeoTracker export on data.ca.gov, and DTSC EnviroStor cleanup sites.

• MPCA regulated sites

  MPCA open data; any use, keep metadata attached. Retrieved September 15, 2026.

  Tank, leak, remediation, Superfund and landfill sites from the Minnesota Pollution Control Agency What's In My Neighborhood database.

• California GAMA Domestic Well Project

  California open data; State Water Resources Control Board. Retrieved September 15, 2026.

  Private well samples from the State Water Board GAMA Domestic Well Project county studies (El Dorado, Tehama, Tulare, San Diego, Yuba, Monterey and others), 2002 to 2011, from the GAMA results file on data.ca.gov.

  Domestic wells only, GAMA_DOM dataset; the USGS rows in the same file are excluded to avoid double counting the Water Quality Portal. Coverage is the counties the project studied, not the whole state. '<' and ND rows keep the reporting limit.

• MDA Township Testing Program nitrate

  Minnesota Geospatial Commons; redistribute with metadata. Retrieved September 15, 2026.

  Nitrate results from the Minnesota Department of Agriculture Township Testing Program, 2013 to 2019, which offered a free test to every well in 344 townships with vulnerable groundwater.

  Townships were selected for vulnerable geology and row-crop land use, so their shares run above the state as a whole; county and state figures are not derived from them. Share is the final (follow-up) result above 10 mg/L as N.

• MDH new private well arsenic tests

  Minnesota Department of Health public data; attribution required. Retrieved September 15, 2026.

  Arsenic results for every new private well drilled and tested August 2008 to December 2021, reported to the Minnesota Department of Health by well contractors and published by county.

  Mandatory test on new wells only, so older wells are not represented; 64,793 wells statewide. Shares are against 10 ug/L, which MDH applies as its advice level. Median and 95th percentile published per county.

• Texas Water Development Board Groundwater Database

  TWDB public data; disclaimer only, attribution given. Retrieved September 9, 2026.

  Water quality samples from the Texas Water Development Board Groundwater Database, collected by TWDB, groundwater conservation districts and cooperators.

  TWDB samples an ambient monitoring network of wells on a rotation, so these describe aquifers, not a survey of homeowners' tests.

  Domestic wells only (WellMain.WellUse = Domestic). Parameter codes for dissolved and total fractions both load; the rollup prefers whichever is reported. Values with a < flag are non-detects. The nightly zip is cached in data/raw/texas.

• Idaho statewide ground water quality monitoring (IDWR EDMS)

  Idaho public data; no terms stated, attribution given. Retrieved September 9, 2026.

  Ground water quality results from the Idaho Department of Water Resources statewide monitoring program and partner agencies (ISDA, IDEQ, INL), EDMS bulk download.

  Domestic wells only (WaterUse = Domestic). Non-detects are stored with the reporting limit. Units are normalized from the mixed mg/l, ug/l and ng/mL labels in the file.

• Nebraska Groundwater Quality Clearinghouse

  Nebraska public data; disclaimer only, attribution given. Retrieved September 9, 2026.

  Groundwater quality results compiled by the Nebraska Department of Environment and Energy, University of Nebraska and Nebraska Department of Agriculture in the Groundwater Quality Clearinghouse, contributed by Natural Resources Districts and state agencies.

  Domestic wells only (Well Type D). Non-detects (ND) are stored with the reporting limit. Nitrate is mg/L as N. Public water supply well locations are confidential and absent.

• KDHE regulated sites

  Kansas public data; attribution required. Retrieved September 9, 2026.

  Identified contaminated sites, leaking underground storage tank facilities and solid waste facilities from the Kansas Department of Health and Environment.

• TCEQ regulated sites

  TCEQ open data; attribution required. Retrieved September 9, 2026.

  Leaking petroleum storage tank sites, state Superfund sites and municipal solid waste landfills from the Texas Commission on Environmental Quality.

• Louisiana LDEQ ambient ground water results (LDH Private Well Initiative)

  Louisiana public data; no terms stated, attribution given. Retrieved September 9, 2026.

  Ground water sample results from the LDEQ Ambient Ground Water Monitoring Program, published by the Louisiana Department of Health Private Well Initiative.

  These are LDEQ monitoring wells sampled by aquifer on a rotation, so the shares describe the aquifer, not a survey of homeowners' wells.

  LDEQ ASSET network wells sampled on a three-year aquifer rotation, not owner-submitted private well tests. USGS rows in the same layer are excluded to avoid double counting the Water Quality Portal.

• Kansas Geological Survey groundwater quality samples

  Kansas Geological Survey public data; attribution required. Retrieved September 9, 2026.

  Groundwater quality samples from the Kansas Geological Survey and Groundwater Management District 2, joined to WWC5 well records.

  These are KGS and groundwater management district sampling wells, not a survey of homeowners' wells.

  Domestic wells only (WWC5 use description starting with Domestic). Results are in the units the explorer publishes (mg/l for most metals, ug/l for a few); nitrate is mg/l as N.

• Wisconsin Well Water Quality Viewer samples

  Public data from UWSP Center for Watershed Science and Education and Wisconsin DHS; attribution required. Retrieved September 9, 2026.

  Private well samples compiled by the UWSP Center for Watershed Science and Education from the DNR Groundwater Retrieval Network, DATCP surveys, the UWSP Water and Environmental Analysis Lab and county health programs, published in the Wisconsin Well Water Quality Viewer with Wisconsin DHS.

  Samples are located to the town, village or city they fall in; one result per well and parameter (the latest) so repeat samples do not double count; wells without a state well number are keyed by location. Shares are against Wisconsin NR 140 enforcement standards (arsenic 10 ug/L, nitrate 10 mg/L as N, manganese 300 ug/L, lead 15 ug/L, copper 1.3 mg/L) and the iron and chloride secondary levels. Many samples were submitted by homeowners with a reason to test, so shares can run above a random survey.

• NJDEP Private Well Testing Act summaries

  NJDEP Data Distribution Agreement; as-is, attribution required. Retrieved September 9, 2026.

  Share of private wells exceeding each standard in tests required at sale or lease under the New Jersey Private Well Testing Act, September 2002 to December 2024, published by NJDEP.

  Tests are untreated water at the time of sale or lease, so every well is counted once per transaction. Municipalities with fewer than ten wells are suppressed. Standards are New Jersey's: arsenic 5 ug/L, PFOA 14 ng/L, PFOS 13 ng/L, PFNA 13 ng/L, manganese and iron secondary standards. Uranium and PFAS were added to the required panel in 2021 and 2020, so their well counts are smaller.

• NC DEQ regulated sites

  NC DEQ open data; attribution required. Retrieved September 9, 2026.

  Underground storage tank incidents from the North Carolina Department of Environmental Quality UST Section.

• Wisconsin DNR regulated sites

  Wisconsin DNR public data; attribution required. Retrieved September 9, 2026.

  Open and closed remediation activities (BRRTS, including leaking underground storage tanks and spills) and landfill and waste sites from the Wisconsin Department of Natural Resources.

• NJDEP regulated sites

  NJDEP Data Distribution Agreement; as-is, attribution required. Retrieved September 9, 2026.

  Known Contaminated Sites, regulated underground storage tank facilities and solid waste landfills from the New Jersey Department of Environmental Protection (NJ-GeoWeb).

• NCWELL private well summaries

  CC0 1.0 (UNC Dataverse). Retrieved September 9, 2026.

  County summaries of private well tests run by the NC State Laboratory of Public Health, 1998 to 2019, compiled by the UNC Superfund Research Program (NCWELL database).

  Counts are tests, not distinct wells; since 2008 every new well is tested once, so most tests are unique wells. Shares are against the NC 2L groundwater standard where one exists (manganese 50 ug/L, lead 15, iron 300) and otherwise the EPA limit. Medians are not used because more than half of results sit at the reporting limit for most analytes.

• Maine DEP PFAS investigation

  Maine public data; attribution required. Retrieved September 3, 2026.

  PFAS results for private wells sampled by the Maine Department of Environmental Protection.

  Maine DEP samples private wells near fields where sludge or septage was spread and near other known PFAS sources, and resamples detections. PFAS shares describe wells that were tested for a reason, not every well in the area.

  ArcGIS layer MaineDEP_PFAS_Investigation/0, domestic wells only. Address fields dropped.

• USGS Water Quality Portal

  Public domain (US federal government data). Retrieved September 3, 2026.

  Data from the Water Quality Portal, a service of USGS, EPA and USDA; groundwater samples collected by USGS and cooperators.

  WQX 3.0 /wqx3/Result (basicPhysChem profile) and /wqx3/Station endpoints. Stations joined for well depth and aquifer.

• Maine Tracking Network private well summaries

  Maine CDC public health data; access constraints none, attribution required. Retrieved September 3, 2026.

  Town summaries of private well tests run by the Maine Health and Environmental Testing Laboratory, published by Maine CDC through the Maine Tracking Network.

  Shares are against Maine's guideline for each analyte (arsenic 10 ug/L, uranium 30 ug/L, fluoride 2 mg/L, manganese 0.3 mg/L, nitrate 10 mg/L, nitrite 1 mg/L). Towns with too few tests are suppressed (NR). Only the share above the guideline and wells tested are published; no medians.

• Vermont Tracking private well summaries

  Vermont Department of Health public data; attribution required. Retrieved September 3, 2026.

  Town summaries of private well tests reported to the Vermont Department of Health, published through Vermont Environmental Public Health Tracking.

  Shares are against the limit Vermont applies to each analyte: arsenic 10 ug/L, uranium 20 ug/L (stricter than EPA), fluoride 4 mg/L, nitrate 10 mg/L, gross alpha 15 pCi/L, radon 4,000 pCi/L advisory. Only towns with 20 or more results are published; statistics below the reporting limit show as *.

• Vermont ANR regulated sites

  CC BY-SA 4.0 (Vermont Open Geodata Portal). Retrieved September 3, 2026.

  Hazardous waste sites, landfills and underground storage tanks from the Vermont Agency of Natural Resources.

• Vermont ANR well completion reports

  CC BY-SA 4.0 (Vermont Open Geodata Portal). Retrieved September 3, 2026.

  Well completion reports filed with the Vermont Agency of Natural Resources since 1966.

  ArcGIS MapServer OPENDATA_ANR_WATER_SP_NOCACHE_v2/162. Owner, purchaser and E911 address fields dropped at ingest.

• Maine DEP regulated sites

  Maine public data; attribution required. Retrieved September 3, 2026.

  Remediation sites, leaking underground storage tanks and closed municipal landfills from the Maine Department of Environmental Protection.

• Maine Geological Survey well database

  Maine public data; attribution required. Retrieved September 3, 2026.

  Well construction records reported to the Maine Geological Survey by licensed well drillers.

  ArcGIS FeatureServer MGS_Wells_Database/0, paged 2000 per request. Address and tax lot fields dropped at ingest.

• NH DHHS WISDOM private well summaries

  NH Department of Health and Human Services public health data; attribution required. Retrieved September 3, 2026.

  Town summaries of private well tests run by the New Hampshire Public Health Laboratories, published by NH DHHS through the WISDOM environmental public health tracking portal.

  Exceedance shares use New Hampshire guidance levels, which are stricter than EPA for arsenic (5 ug/L), manganese (0.3 mg/L), radon (2,000 pCi/L) and sodium (20 mg/L). Statistics for small counts are suppressed (*).

• NHDES OneStop regulated sites

  NHDES public data; screening use, attribution required. Retrieved September 3, 2026.

  Remediation sites, underground storage tanks, solid waste facilities and potential contamination sources from the New Hampshire Department of Environmental Services OneStop database.

• NHDES PFAS sampling

  NHDES public data; screening use, attribution required, aggregates only. Retrieved September 3, 2026.

  PFAS results for private wells from the New Hampshire Department of Environmental Services Environmental Monitoring Database.

  NHDES samples private wells near known or suspected PFAS sources (industrial sites, airports, landfills, fire training areas), and wells with a detection are resampled over time. PFAS shares describe wells that were tested for a reason, not every well in the area.

  PFAS_Sampling FeatureServer layer 1 (stations) joined to table 6 (results) on STANO. Residential/private wells only. Addresses dropped.

• NHDES Water Well Inventory

  NHDES public data; screening use, attribution required, aggregates only. Retrieved September 3, 2026.

  Well construction records reported to the New Hampshire Department of Environmental Services Water Well Board.

  ArcGIS REST layer, paged 1000 records at a time. Owner and address fields dropped at ingest.

• Connecticut DPH and USGS arsenic and uranium survey

  USGS data release, public domain.

  Arsenic and uranium in 674 private bedrock wells sampled by the Connecticut Department of Public Health with the U.S. Geological Survey, 2013 to 2015.

  One sample per well per analyte, ug/L, with town and county but no coordinates; sites are placed on the town. Non-detects print as <3 (arsenic) and <1 (uranium).

• Oklahoma OWRB reported well logs

  OWRB public data; attribution given.

  Well completion reports filed with the Oklahoma Water Resources Board, located by public land survey.

  Layer Groundwater/Groundwater_Wells/MapServer/1 (136,887). use_class Domestic is domestic; total_dpth and first_wtr in feet; approx_yld in gpm; const_date is epoch milliseconds. Owner fields are not requested.