Prepared in cooperation with the Wayne Conservation District Baseline Assessment of Groundwater Quality in Wayne County, Pennsylvania, 2014 Scientific Investigations Report 2016–5073 Version 1.1, March 2017 U.S. Department of the Interior U.S. Geological Survey Cover. Tanners Falls and exposure of Devonian-age sedimentary rocks of the Catskill Formation, Dyberry Township, Wayne County, Pennsylvania, May 2016. (Photograph by Sylvia Thompson, Wayne Conservation District.) Baseline Assessment of Groundwater Quality in Wayne County, Pennsylvania, 2014 By Lisa A. Senior, Charles A. Cravotta, III, and Ronald A. Sloto Prepared in cooperation with the Wayne Conservation District Scientific Investigations Report 2016–5073 Version 1.1, March 2017 U.S. Department of the Interior U.S. Geological Survey U.S. Department of the Interior SALLY JEWELL, Secretary U.S. Geological Survey Suzette M. Kimball, Director U.S. Geological Survey, Reston, Virginia First Release: 2016, online Revised: March 2017 (ver. 1.1), online For more information on the USGS—the Federal source for science about the Earth, its natural and living resources, natural hazards, and the environment, visit http://www.usgs.gov or call 1-888-ASK-USGS For an overview of USGS information products, including maps, imagery, and publications, visit http://store.usgs.gov To order this and other USGS information products, visit http://store.usgs.gov Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government. Although this report is in the public domain, permission must be secured from the individual copyright owners to reproduce any copyrighted materials contained within this report. Suggested citation: Senior, L.A., Cravotta, C.A., III, and Sloto, R.A., 2017, Baseline assessment of groundwater quality in Wayne County, Pennsylvania, 2014 (ver. 1.1, March 2017): U.S. Geological Survey Scientific Investigations Report 2016–5073, 136 p., http://dx.doi.org/10.3133/sir20165073. ISSN 2328-0328 (online) iii Acknowledgments The participation of individual well owners who made their wells accessible for the study is appreciated. The assistance and cooperation of Jamie Knecht of the Wayne Conservation District in obtaining grant funding from the Pennsylvania Department of Community and Economic Development Baseline Water Quality Program, identifying and obtaining permission from well owners, and conducting field work is gratefully acknowledged. U.S. Geological Survey (USGS) personnel from the New York Water Science Center and Pennsylvania Water Science Center who collected the groundwater samples include Tia-Marie Scott, Paul Heisig, Richard Reynolds, and Dana Heston. Linda Zarr of USGS assisted in data processing. v Contents Abstract ...........................................................................................................................................................1 Introduction.....................................................................................................................................................2 Purpose and Scope ..............................................................................................................................4 Description of Study Area ...................................................................................................................4 Physiography and Geologic Setting .........................................................................................4 Hydrogeologic Setting ................................................................................................................7 Previous Investigations........................................................................................................................7 Methods of Sample Collection and Analysis ............................................................................................9 Selection of Sampling Locations ......................................................................................................10 Collection of Samples ........................................................................................................................12 Analysis of Chemical, Physical, and Other Characteristics and Reporting Units ....................12 Quality Control and Quality Assurance ...........................................................................................13 Temporal Variability ............................................................................................................................14 Graphical and Statistical Analyses ..................................................................................................15 Geochemical Modeling .....................................................................................................................16 Baseline Groundwater Quality in Wayne County ..................................................................................16 Geochemical Controls on Selected Constituents in Groundwater .............................................17 Wayne County Groundwater Quality and Its Relation to Drinking-Water Standards .............17 General Characteristics ...........................................................................................................18 Field measurements of pH, Alkalinity, Specific Conductance, and Dissolved Oxygen .............................................................................................................18 Total Dissolved Solids, Total Solids, Hardness, and Corrosivity ..............................18 Major and Minor Ions ...............................................................................................................22 Nutrients ......................................................................................................................................23 Bacteria .......................................................................................................................................23 Trace Elements and Metals ......................................................................................................25 Arsenic................................................................................................................................25 Iron and Manganese ........................................................................................................25 Radionuclides ............................................................................................................................29 Gross alpha- and gross beta-particle radioactivity ....................................................29 Radon-222...........................................................................................................................33 Uranium ..............................................................................................................................33 Man-made Organic Compounds .............................................................................................33 Methane and Other Dissolved Hydrocarbon Gases ............................................................33 Methane Isotopic Composition and Origin of Methane Gas .....................................35 Geochemical Modeling and Analysis of Water Quality Data ...............................................................44 Types of Groundwater as Characterized by Major Ions...............................................................44 Ratios of Chloride, Bromide, and Sodium in Groundwater ..........................................................48 Correlations Among Major and Trace Constituents in Groundwater.........................................52 Evolution of Chemical Composition and Conceptual Hydrogeochemical Model .....................55 vi Geochemical Modeling .............................................................................................................55 Conceptual Hydrogeochemical Model ..................................................................................61 Spatial Distribution of Groundwater Quality and Relation to Hydrogeologic Setting .............63 Summary and Conclusions .........................................................................................................................65 References Cited..........................................................................................................................................66 Appendix 1. Summary of water-quality data for 34 groundwater samples collected in Wayne County, Pennsylvania, during 2011 and 2013..........................................................100 Appendix 2. Analytical methods and reporting levels for constituents analyzed, by laboratory .................................................................................................................................102 Appendix 3. Quality assurance and quality control data .................................................................105 Appendix 4. Spearman rank correlation coefficients and boxplots showing sample compositions by groups (pH and redox ranges, principal components) for groundwater samples collected from Wayne County, Pennsylvania, 2013–14 .................................................................................................................120 Figures 1. Map showing location of Wayne County, Pennsylvania, and gas wells drilled from 2005 through August 2015 ......................................................................................3 2. Map showing physiography, geology of the bedrock closest to land surface, and location of sampled wells in 2013 and 2014 in Wayne County, Pennsylvania .............5 3. Stratigraphic correlation chart for Devonian-age and younger geologic units, Wayne County, Pennsylvania ...........................................................................................6 4. Graph showing observed daily mean water levels during 2013–14 and long-term (1987–2014) daily median water levels in an observation well WN-64, Wayne County, Pennsylvania .......................................................................................7 5. Map and graphs showing A, land-surface elevation, streams, and location of wells sampled for baseline groundwater quality assessments in Wayne County, Pennsylvania during 2013 and 2014, B, transect A-A’ showing land-surface elevation, and C, transect B-B’ showing land-surface elevation .................8 6. Map showing spatial distribution of pH in water samples collected from 89 wells in 2014 and 32 wells in 2013 in Wayne County, Pennsylvania ..............................21 7. Graphs showing relation between field measured pH and A, laboratory alkalinity, B, field specific conductance, and C, dissolved oxygen concentrations in water samples collected from 89 wells in Wayne County, Pennsylvania, July–September 2014 .......................................................................................22 8. Graph showing relation between field measured specific conductance and concentrations of total dissolved solids in water samples collected from 89 wells in Wayne County, Pennsylvania, July–September 2014 .......................................22 9. Graphs showing relation between field measured pH and A, hardness, and B, corrosivity (as measured by calcite saturation index) in water samples collected from 89 wells in Wayne County, Pennsylvania, July–September 2014 ............23 vii 10. Map showing spatial distribution of dissolved sodium concentrations in water samples collected from 89 wells in 2014 and 32 wells in 2013 in Wayne County, Pennsylvania ...................................................................................................24 11. Graphs showing relation between field measured pH and dissolved concentrations of A, arsenic, B, molybdenum, antimony, and selenium, and C, copper and lead in water samples collected from 89 wells in Wayne County, Pennsylvania, July–September 2014 ...........................................................27 12. Map showing spatial distribution of dissolved arsenic concentrations in water samples collected from 89 wells in 2014 and 32 wells in 2013 in Wayne County, Pennsylvania ...............................................................................................28 13. Graphs showing concentrations of dissolved iron and manganese in relation to concentrations of A, dissolved oxygen, B, nitrate, and C, sulfate in water samples collected from 89 wells in Wayne County, Pennsylvania, July–September 2014 .................................................................................................................29 14. Graphs showing concentrations of total and particulate iron and manganese in relation to concentrations of A, dissolved oxygen and B, pH, in water samples collected from 89 wells in Wayne County, Pennsylvania, July–September 2014 .................................................................................................................30 15. Graphs showing relation between A, gross alpha-particle activity and gross beta-particle activity, B, gross alpha-particle activity and dissolved uranium concentrations, and C, gross beta-particle activity and dissolved uranium concentrations in water samples collected from 89 wells in Wayne County, Pennsylvania, July–September 2014 .......................................................................................32 16. Map showing spatial distribution of radon-222 activities (concentrations) in water samples collected from 89 wells in 2014 and 32 wells in 2013 in Wayne County, Pennsylvania ...................................................................................................34 17. Graph showing dissolved uranium concentrations in relation to field measured pH in water samples collected from 89 wells in Wayne County, Pennsylvania, July–September 2014 .......................................................................................35 18. Map showing spatial distribution of dissolved uranium concentrations in water samples collected from 89 wells in 2014 and 32 wells in 2013 in Wayne County, Pennsylvania ...............................................................................................36 19. Map showing spatial distribution of dissolved lithium and relatively elevated (>0.7 mg/L) methane concentrations in water samples collected from 89 wells in 2014 and 32 wells in 2013 in Wayne County, Pennsylvania .....................40 20. Graph showing isotopic composition of methane in water samples collected from eight wells in 2014, Wayne County, Pennsylvania .......................................................42 21. Graphs showing A, Isotopic composition of methane in water samples collected from eight wells in Wayne County, Pennsylvania, 2014, and in mud-logging gas samples collected from different geologic formations during drilling of Marcellus Shale gas wells in Pennsylvania, and B, C1/C2 (methane/ethane) ratios in relation to carbon-isotopic composition for methane in these same samples ........................................................................................43 22. Graphs showing relation of field measured pH to dissolved A, arsenic, bromide, fluoride, and methane concentrations, B, sodium, lithium, and boron concentrations, and C, barium and strontium concentrations in water samples collected from 89 wells in Wayne County, Pennsylvania, July–September 2014 .................................................................................................................45 viii 23. Trilinear (Piper) diagrams showing major ion composition for A, predominant water types or hydrochemical facies, B, water samples collected from 117 wells in Wayne County, Pennsylvania, 2013–14 plus median composition of brine from oil and gas wells in western Pennsylvania and flowback water from Marcellus Shale gas wells, C, 11 selected groundwater samples from Wayne County, 2013–14, and D, evolution pathways for mixing of dilute Ca-HCO groundwater with 3 road salt; with brine; with brine combined with cation exchange; or with brine plus calcite dissolution to saturation and then cation exchange ............................46 24. Pie charts showing typical ionic contributions to computed specific conductance (SC) for selected groundwater samples from Wayne County, 2014, for wells A, WN-345, B, WN-371, C, WN-361, and D, WN-295 ....................49 25. Graphs showing chloride concentrations in relation to A, chloride/bromide mass ratios for various ranges of bromide concentrations, B, chloride/bromide mass ratios for samples with and without elevated (>1.0 mg/L) methane concentrations, C, bromide concentrations, and D, sodium concentrations for 121 groundwater samples collected from 117 wells in Wayne County, Pennsylvania, 2013–14, plus median values for Salt Spring, flowback waters from Marcellus Shale gas wells, and oil- and gas-field brines from Western Pennsylvania ..................................................50 26. Graphs showing saturation indices for minerals and other solids in relation to pH for 121 groundwater samples from 117 wells in Wayne County, Pennsylvania, 2013–14 .................................................................................................57 27. Graphs showing equilibrium fractions of initial concentrations of A, anions or B, cations that may be dissolved or adsorbed on a finite amount of hydrous ferric oxide (HFO) at 25 degrees Celsius as a function of pH ..............................58 28. Graphs showing computed compositions of waters resulting from initial composition of low-ionic strength groundwater (from well WN-371) with dissolution of road deicing salt (NaCl Br ) and (or) calcite, but without 0.99996 0.00004 cation exchange. Low ionic strength groundwater (WN-371) with A, dissolution of deicing salt but without other reactions, B, mixing with median oil and gas well brine but without other other reactions, C, dissolution of deicing salt plus calcite (CaCO ) dissolution to equilibrium (saturation index = 0), 3 and D, mixing with median oil and gas well brine plus calcite dissolution to equilibrium ...............................................................................................................................59 29. Graphs showing computed composition of waters resulting from initial composition of low-ionic strength groundwater (from well WN-371) with reactions including dissolution of calcite and (or) cation exchange and (or) mixing with different amounts of brine. Low-ionic strength groundwater (WN-371) with dissolution of incremental amounts of calcite (CaCO ) until 3 reaching equilibrium A, without cation exchange, B, with cation exchange. Low-ionic strength groundwater (WN-371) mixes with median oil and gas well brine C, with cation exchange, and D, with calcite dissolution to equilibrium and cation exchange .............................................................................................60 30. Schematic diagram of generalized conceptual hydrogeochemical model for distribution of fresh and saline groundwater in fractured bedrock aquifer setting .............................................................................................................................62 31. Boxplots showing distribution of well bottom elevations, land surface elevations, and well depths for groundwater samples from 117 wells in Wayne County, Pennsylvania, 2013–14, grouped by pH class interval as “acidic” (5.4< pH <6.4, n=29), “neutral” (6.5< pH <7.4, n=32), “alkaline” (7.5< pH <7.9, n=25), and “very alkaline” (8.0< pH <9.4, n=9) ...............................................64