Association of State Drinking-Water Administrators, Understanding Chemical and Microbial Contaminants in Drinking Water: Raw, Treated, and Tap Water Groundwater Sources – Bruce Lindsey Water Quality from Source Through Treatment - Ed Furlong, Susan Glassmeyer, and John Sullivan Water Quality from Distribution to the Consumer - Paul Bradley Association of State Drinking-Water Administrators, September 5th, 2018

Groundwater sources: Untreated Water From Principal Aquifers Bruce Lindsey, USGS

Objective: What is the quality of groundwater used as a source of public supply in the United States?

We can answer that question Spatially weighted sampling of principal aquifers Identify contaminants of concern Are contaminants widespread or regional?

National Assessment: 18 Principal Aquifers 85 percent of public supply use (by pumping volume) 1,300 public-supply wells sampled Maupin, M.A., and Barber, N.L., 2005, Estimated Withdrawals from Principal Aquifers in the United States, 2000, US Geological Survey Circular 1279

Aquifer Assessment: Each aquifer evaluated individually by spatially weighted sampling Assess proportion of the aquifer with high concentrations Given a grid of 60 cells, a contaminant is unlikely to be missed if it is present in more than 4 % of the aquifer. Belitz, K., B. Jurgens, M. K. Landon, M. S. Fram, and T. Johnson (2010), Estimation of aquifer scale proportion using equal area grids: Assessment of regional scale groundwater quality, Water Resour. Res., 46, W11550, doi:10.1029/2010WR009321.

GROUNDWATER: A THREE DIMENSIONAL RESOURCE Monitoring wells 20 to 50 feet deep Solid Casing Domestic wells 100 to 200 feet deep Screened or Open interval Production wells 150 to 750 feet deep Irrigation wells Public supply wells

Summary of Principal Aquifer Survey Results Compare Concentrations to Water-Quality Benchmarks* *USEPA MCLs, SMCLs, Health Advisories, USGS HBSLs HIGH (concentration > benchmark) MODERATE (concentration 50-100% benchmark for inorganic compounds or 10-100% of benchmark for organic compounds) LOW (concentration <50% benchmark for inorganic compounds or <10% of benchmark for organic compounds) 8

INORGANICS All 18 principal aquifers, assessed by aquifer area 34 trace elements and major and minor ions, of which 19 have human-health benchmarks 8 radioactive constituents, of which 4 have benchmarks 5 nutrients, of which 2 have benchmarks HIGH MODERATE LOW Percentages are area weighted Data are provisional and subject to revision

ORGANICS 90 VOCs, of which 38 have human-health benchmarks 227 pesticide compounds (pesticides and their breakdown products), of which 119 have benchmarks For organics, low concentrations are less than 10% of the benchmark HIGH MODERATE LOW Percentages are area weighted Data are provisional and subject to revision

Summary of Constituents Exceeding Benchmarks in all 18 Aquifers Exceedance Frequency Number of aquifers with exceedances  Radium 226 + Radium 228 5% 8 Arsenic 12  Gross-alpha radioactivity, 72 hour count 4% 12 Manganese Strontium 3% 9 Radon-222 2% 5 Fluoride 1% 6 Gross-beta radioactivity, 72 hour count Percentages are area weighted Data are provisional and subject to revision

Summary of Constituents Exceeding Benchmarks in all 18 Aquifers Exceedance Frequency Number of aquifers with exceedances  Uranium 0.9% 3 Nitrate plus nitrite, as nitrogen 0.5% 5 Molybdenum 0.2% 2 Lead Thallium Beryllium 0.1% 1 Percentages are area weighted Data are provisional and subject to revision

HIGH MODERATE LOW Radium Radium (Combined 226+228) WELL LOCATION AND CONCENTRATION HIGH HIGH MODERATE MODERATE LOW LOW Percentages are area weighted Data are provisional and subject to revision

HIGH MODERATE LOW Arsenic Arsenic Percentages are area weighted WELL LOCATION AND CONCENTRATION HIGH HIGH MODERATE MODERATE LOW LOW Percentages are area weighted Data are provisional and subject to revision

HIGH MODERATE LOW GROSS ALPHA ACTIVITY Gross Alpha Activity WELL LOCATION AND CONCENTRATION HIGH HIGH MODERATE MODERATE LOW LOW Percentages are area weighted Data are provisional and subject to revision

HIGH MODERATE LOW Manganese Manganese Percentages are area weighted WELL LOCATION AND CONCENTRATION HIGH HIGH MODERATE MODERATE LOW LOW Percentages are area weighted Data are provisional and subject to revision

HIGH MODERATE LOW Radon Radon Percentages are area weighted WELL LOCATION AND CONCENTRATION HIGH HIGH MODERATE MODERATE LOW LOW Percentages are area weighted Data are provisional and subject to revision

HIGH MODERATE LOW Nitrate Nitrate Percentages are area weighted WELL LOCATION AND CONCENTRATION HIGH HIGH MODERATE MODERATE LOW LOW Percentages are area weighted Data are provisional and subject to revision

HIGH MODERATE LOW AT LEAST ONE CONTAMINANT OF CONCERN Percentages are area weighted Data are provisional and subject to revision

Detection Frequency Provisional data subject to revision

Unique aspects of NAWQA sampling Groundwater age Extrapolating to aquifer scale Emerging contaminants Full radionuclide suite, Pb 210 and Po 210 Unregulated Contaminant Monitoring Rule (UCMR) contaminants: Perfluorinated compounds and cyanotoxins Pharmaceuticals and hormones Pesticide breakdown products

Percentages are area weighted Data are provisional and subject to revision

Rosecrans, Nolan, and Gronberg, 2017, Prediction and visualization of redox conditions in the groundwater of Central Valley, California, Journal of Hydrology, https://doi.org/10.1016/j.jhydrol.2017.01.014 23

Conclusion: blindsey@usgs.gov What is the quality of groundwater used as a source of public supply in the United States? Concentrations were less than human-health-benchmarks in 84 percent of the groundwater from public supply wells. Radionuclides and trace elements are the contaminants that most frequently exceeded human-health benchmarks. blindsey@usgs.gov