Ambient Groundwater Quality of the Lower San Pedro Basin: A 2000 Baseline Study ADEQ Open File Report 02-01 July 2002 Ambient Groundwater Quality of the Lower San Pedro Basin: A 1999-2000 Baseline Study By Douglas C. Towne Maps by Larry W. Stephenson Arizona Department of Environmental Quality (ADEQ) Open File Report 2002-01 ADEQ Water Quality Division Hydrologic Support & Assessment Section Groundwater Monitoring Unit 3033 North Central Avenue Phoenix, Arizona 85012 Thanks: Report Preparation: Field Assistance: Report Printing: Photo Credits: Lorraine Akey, Danese Cameron, Warren Elting, Maureen Freark, Stephen Franchuk, Douglas McCarty, Larry Stevenson, and Wang Yu Elizabeth J. Boettcher, Maureen Freark, Kip Gambee (ASARCO), Angela Lucci, Royce Flora, and the many well owners in the basin who were kind enough to give permission to collect groundwater data on their property. Mario Ballesteros and Crew Douglas Towne Report Cover: At first glance, a well casing and turbine pump appear to be growing as part of a healthy riparian ecosystem, competing for sunlight with a grove of juvenile cottonwood trees. As indicated by the presence of Jason Ekstein of the Nature Conservancy (TNC) next to the casing, the turbine pump sits approximately 20 feet above land surface. The farmland surrounding this irrigation well was eroded away during 1993 flooding on the San Pedro River, a problem that has been ongoing since the 1890s39. This “well in the sky” is located at the TNC’s San Pedro River Reserve near the community of Dudleyville. Other Publications of the ADEQ Ambient Groundwater Monitoring Program Ambient Groundwater Quality of the Lower San Pedro Basin: A 2000 Baseline Study. ADEQ Factsheet 02-09, August 2002, 4 p. Ambient Groundwater Quality of the Willcox Basin: A 1999 Baseline Study. ADEQ Open File Report 01-09, November 2001, 55 p. Ambient Groundwater Quality of the Willcox Basin: A 1999 Baseline Study. ADEQ Factsheet 01-13, October 2001, 4 p. Ambient Groundwater Quality of the Sacramento Valley Basin: A 1999 Baseline Study. ADEQ Factsheet 01-10, June 2001, 4 p. Ambient Groundwater Quality of the Sacramento Valley Basin: A 1999 Baseline Study. ADEQ Open File Report 01-04, June 2001, 77 p. Ambient Groundwater Quality of the Yuma Basin: A 1995 Baseline Study. ADEQ Factsheet 01-03, April 2001, 4 p. Ambient Groundwater Quality of the Virgin River Basin: A 1997 Baseline Study. ADEQ Factsheet 01-02, March 2001, 4 p. Ambient Groundwater Quality of the Prescott Active Management Area: A 1997-98 Baseline Study. ADEQ Factsheet 00-13, December 2000, 4 p. Ground-Water Quality in the Upper Santa Cruz Basin, Arizona, 1998. Joint Publication: USGS Water Resources Investigations Report 00-4117 - ADEQ Open File Report 00-06, September 2000, 55 p. Ambient Groundwater Quality of the Douglas Basin: An ADEQ 1995-1996 Baseline Study. ADEQ Factsheet 00-08, September 2000, 4 p. Ambient Groundwater Quality of the Prescott Active Management Area: A 1997-98 Baseline Study. ADEQ Open File Report 00-01, May, 2000, 77 p. Ground-Water Quality in the Sierra Vista Sub-basin, Arizona, 1996-97. Joint Publication: USGS Water-Resources Investigations Report 99-4056 - ADEQ Open File Report 99-12, July 1999, 50 p. Ambient Groundwater Quality of the Douglas Basin: A 1995-96 Baseline Study. ADEQ Open File Report 99-11, June 1999, 155 p. Ambient Groundwater Quality of the Virgin River Basin: A 1997 Baseline Study. ADEQ Open File Report 99-4, March 1999, 98 p. Ambient Groundwater Quality of the Yuma Basin: A 1995 Baseline Study. ADEQ Open File Report 98-7, September, 1998, 121 p. Collection and Analysis of Ground-Water Samples in the Sierra Vista Basin, Arizona, 1996. Joint Publication: USGS Factsheet FS-107-97 - ADEQ Factsheet 97-8, August 1997, 4 p. The Impacts of Septic Systems on Water Quality of Shallow Perched Aquifers: A Case Study of Fort Valley, Arizona. ADEQ Open File Report 97-7, February 1997, 70 p. Contents II CONTENTS Abstract . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 Purpose and Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 Physical Setting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 Cultural Setting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 ..................................................................................... 9 Geohydrologic Setting Geology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 Aquifers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 Groundwater Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 Groundwater Sampling Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 Water Quality Standards/Guidelines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 Water Quality Standard/Guideline Exceedances . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 Suitability for Irrigation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 Analytical Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 Groundwater Composition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 Groundwater Quality Patterns . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 Time Trend Analyses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 Suitability of Groundwater for Domestic Use . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 Groundwater Quality Patterns . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 Study Design and Data Evaluation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36 Recommendations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37 APPENDICES Basic Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40 Data on Sample Sites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40 Groundwater Quality Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44 Groundwater Quality Data by Aquifer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59 Volatile Organic Compound (VOC) Analyte List . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61 MRLs of Groundwater Protection List (GWPL) Pesticides . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62 Surface Water Quality Data Related to the LSP Study . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63 Driller’s Logs of Selected Wells . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64 Methods of Investigation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65 Sampling Strategy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65 Sample Collection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66 Laboratory Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66 Sample Numbers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69 Data Evaluation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69 Quality Assurance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69 Data Validation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70 Statistical Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73 Contents III FIGURES Figure 1. San Pedro River riparian area. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 Figure 2. LSP vista. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Figure 3. LSP Satellite image. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Figure 4. Confluence of San Pedro River and Gila River. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 Figure 5. LSP geology, land ownership, and groundwater levels of sampled wells. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 Figure 6. Ranching gateway near Winchester Mountains. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Figure 7. Farmland along the San Pedro River. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 Figure 8. San Manuel mining complex. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 Figure 9. Irrigation well supplying a cotton field. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 Figure 10. Flowing artesian well. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 Figure 11. Abandoned windmill. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 Figure 12. High-production well in ASARCO wellfield. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 Figure 13. Site exceedances and generalized aquifer locations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 Figure 14. Spring in the Santa Catalina Mountains. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 Figure 15. Arsenic and manganese concentrations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 Figure 16. Fluoride and hardness concentrations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 Figure 17. Groundwater chemistry types and pH levels. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 Figure 18. Sulfate and TDS concentrations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 Figure 19. Salinity and sodium hazards for irrigation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 Figure 20. Groundwater chemistry of sites. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 Figure 21. Sulfate-TDS correlation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 Figure 22. Hardness-pH correlation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 Figure 23. Fluoride concentration by aquifer. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 Figure 24. Bicarbonate concentration by aquifer. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 Figure 25. Sodium concentration in floodplain aquifer by watershed. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 Figure 26. Chloride concentration in floodplain aquifer by watershed. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 Figure 27. TDS concentration by watershed. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 Figure 28. Temperature levels relative to groundwater depth. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 Figure 29. Well in Gila River floodplain. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31 Figure 30. “Mountain Water” vending machine. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32 Figure 31. Coolidge Dam and San Carlos Reservoir. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33 Figure 32. Spring headgate at Cook’s Lake. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65 TABLES Table 1. Table 2. Table 3. Table 4. Table 5. Table 6. Table 7. LSP sites exceeding health-based water quality standards (Primary MCLs) . . . . . . . . . . . . . . . . . . . . . . . . . . LSP sites exceeding aesthetics-based water quality guidelines (Secondary MCLs) . . . . . . . . . . . . . . . . . . . . Summary statistics for LSP groundwater quality data. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Time-trend comparison of LSP sample sites. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ADHS/Del Mar laboratory methods used in the LSP study . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Summary results of LSP duplicate samples from ADHS/ARRA laboratories . . . . . . . . . . . . . . . . . . . . . . . . . . Summary results of LSP split samples from ADHS/Del Mar laboratories . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 18 21 28 67 71 72 Contents IV ABBREVIATIONS amsl af af/yr ADEQ ADHS ADWR ARRA As ASARCO BHP bls BLM o C CI0.95 Cl EPA F Fe gpm GWPL HCl LLD LSP Mn MCL ml msl Fg/l Fm FS/cm mg/l MRL MTBE ns ntu pCi/l QA QAPP QC SAR SDW SC su SO4 TDS TKN USGS VOC above mean sea level acre-feet acre-feet per year Arizona Department of Environmental Quality Arizona Department of Health Services Arizona Department of Water Resources Arizona Radiation Regulatory Agency arsenic American Smelting and Refining Company Broken Hill Properties below land surface U.S. Department of the Interior Bureau of Land Management degrees Celsius 95 percent Confidence Interval chloride U.S. Environmental Protection Agency fluoride iron gallons per minute Groundwater Protection List pesticide hydrochloric acid Lower Limit of Detection Lower San Pedro groundwater basin manganese Maximum Contaminant Level milliliter mean sea level micrograms per liter micron microsiemens per centimeter at 25E Celsius milligrams per liter Minimum Reporting Level Methyl tertiary-Butyl Ether not significant nephelometric turbidity unit picocuries per liter Quality Assurance Quality Assurance Project Plan Quality Control Sodium Adsorption Ratio Safe Drinking Water Specific Conductivity standard pH units Sulfate Total Dissolved Solids Total Kjeldahl Nitrogen U.S. Geological Survey Volatile Organic Compound Contents V “I don’t know where this water comes from. Just doesn’t make any sense to me, but it certainly is there. Right there,” he indicated stabbing his finger down on the map. The creeks of (the) Galiuro (Mountains) befuddle him. So much water in a place where there should be so little. Although the Galiuros (Mountains) reach as high as 7,663 feet, they do not account in size for the amount of water produced in the springs and creeks below. These desert creeks, all around a 4,000-foot elevation, are too numerous. Even larger mountain ranges that feed the surrounding deserts cannot produce this volume of water. For the number of cattle historically grazing this area, about 25 windmills would be expected. There are only six. Much of the water is actually a remnant of the ice age. Stored and doled out in the increments of small streams, this Pleistocene water slowly drains from aquifers buried in the mountains, joining banks of much more recent runoff water. Radiocarbon dating on the groundwater here places it back 10,000 years, while the oldest water goes back to over 15,000 years. Hydrologists call it fossil water. Craig Childs in The Secret Knowledge of Water60 Visit the ADEQ Ambient Groundwater Monitoring Program at: http://www.adeq.state.az.us/environ/water/assess/ambient.html#studies http://www.adeq.state.az.us/environ/water/assess/target.html#studies Contents VI Ambient Groundwater Quality of the Lower San Pedro Basin: A 2000 Baseline Study By Douglas C. Towne Abstract - The Lower San Pedro Groundwater Basin (LSP) baseline groundwater quality study was conducted by the Arizona Department of Environmental Quality (ADEQ) in 2000. Located in southeastern Arizona, this semiarid basin is drained by the San Pedro and Gila Rivers. The LSP is a rural landscape with scattered towns and two extensive copper mining and processing operations. Groundwater from three aquifers (floodplain, unconfined basin-fill, and confined basin-fill or artesian) and fractured mountain hardrock is the principle source of water supply. For this study, 63 groundwater sites were sampled for inorganic constituents. In addition, fewer sites were also sampled for Volatile Organic Compounds (25), radiochemistry (19), radon (19), and pesticide (2) analyses. Eighteen (18) percent of sample sites had concentrations of at least one constituent that exceeded a health-based, Federal or State water-quality standard. These enforceable standards define the maximum concentrations of constituents allowed in water supplied to the public 54. Constituents that exceeded these standards included antimony (2 sites), arsenic (1 site under current standards, 12 sites under standards effective in 2006), fluoride (8 sites), nitrate (1 site), and gross alpha (2 sites). In addition, 49 percent of sample sites had concentrations of at least one constituent that exceeded an aesthetics-based, Federal water-quality guideline. These are unenforceable guidelines that define the maximum concentration of a constituent that can be present in drinking water without an unpleasant taste, color, odor, or other aesthetic effect occurring54. Constituents that exceeded these guidelines included chloride (2 sites), fluoride (16 sites), iron (4 sites), manganese (9 sites), pH (4 sites), sulfate (11 sites), and total dissolved solids (24 sites). At one site, Volatile Organic Compounds that are common by-products of chlorination were detected. No pesticides or pesticide degradation by-products were detected. Artesian conditions can exist when confined basin-fill aquifers, which are generally found along the central portion of the basin’s axis, are intercepted35. Artesian water in the LSP is suitable for domestic and irrigation purposes at its southern boundary near Redington. Farther north, however the water quality deteriorates. Gypsum deposit dissolution and the associated cation exchange in the Mammoth-Dudleyville corridor creates groundwater with elevated sulfate and sodium concentrations. The artesian aquifer also has a chemically closed hydrologic system that favors alkaline pH values and depleted calcium concentrations, which also contribute to the elevated concentrations that can exceed water quality standards. The elevated sodium and other salt concentrations also make these confined basin-fill aquifer waters unsuitable for irrigation north of Redington. The floodplain aquifer is the most productive in the basin and supplies water for most irrigation and municipal uses. This aquifer forms a long corridor following the major waterways and receives most of its recharge from surface water flows 10. As such, this aquifer is considered to be a chemically open hydrologic system. However, leakage from the lower confined basin-fill aquifer upwards into the floodplain aquifer is thought to be largely responsible for the variable salinity and fluoride concentrations that are particularly elevated near Mammoth41. The elevated salinity, sodium, chloride, and potassium concentrations found in the most downgradient portions of the floodplain aquifer appear to be related to the high concentrations of these constituents in the Gila River. Elevated sulfate concentrations found along the floodplain aquifer between Mammoth and Winkelman may be from leakage from the confined basin-fill aquifer and the elevated concentrations carried north by the San Pedro River. The source of sulfates for both aquifers appears to be a combination of nearby gypsum deposits and mine tailing dumps, though the contribution of each would require an intensive targeted study to determine. Groundwater collected from the unconfined basin-fill aquifer and from hardrock areas was the most dilute and had the fewest water quality standard exceedances. Unfortunately, these areas also have a somewhat limited groundwater production potential. Differences in water quality between these aquifers and the floodplain aquifer appear to be related to a more dilute recharge source (mountain precipitation and runoff) as well as minimal leakage from the confined basin-fill aquifer. Potential water quality problems appear largely confined to fault zones producing water from great depths and granitic rock areas which may have elevated radiochemistry concentrations28. Abstract 1 INTRODUCTION The Lower San Pedro groundwater basin (LSP) is located in southeastern Arizona and characterized as a predominantly rural landscape with small scattered settlements. The San Pedro River, perennial in stretches, flows north through the center axis of the basin to the confluence with the Gila River. The Gila River, which enters the basin from San Carlos Reservoir in the east, is the main drainage north of Winkelman. Mining is the most important economic activity as several large copper mining and milling operations are located in the basin. Limited areas of irrigated farmland are scattered along stretches of floodplain. Upland areas have been utilized by ranches for livestock grazing. Recent population increases are largely the result of dispersed residential development by commuters and retirees drawn to the basin for its solitude and picturesque scenery, especially along the rare desert riparian habitat formed by perennial reaches of the San Pedro River (Figure 1). Groundwater is the primary source for domestic, municipal, irrigation, livestock, and mining uses in the LSP. As the population increases in the future, development will raise challenges of supplying groundwater that will meet U.S. Environmental Protection Agency (USEPA) Safe Drinking Water (SDW) Act water quality standards while under increased pressure from regional development. To assess these hydrological issues, the Arizona Department of Environmental Quality (ADEQ) Groundwater Monitoring Unit conducted a study to characterize the current (2000) groundwater quality conditions in the LSP. Sampling by ADEQ was completed as part of the Ambient Groundwater Monitoring Program, which is based on the legislative mandate in the Arizona Revised Statutes §49-2255 that authorizes: “...ongoing monitoring of waters of the state, including...aquifers to detect the presence of new and existing pollutants, determine compliance with applicable water quality standards, determine the effectiveness of best management practices, evaluate the effects of pollutants on public health or the environment, and determine water quality trends.” This ADEQ program examines regional groundwater quality in Arizona basins such as the LSP. Sample sites are chosen using a stratified random selection process. The analytical results of these samples are compared to water quality standards as well as statistically examined for significant patterns and relationships. Purpose and Scope ADEQ sampled 63 sites for this groundwater quality assessment. Specific sample types and numbers collected and analyzed include inorganics (physical parameters, major ions, nutrient constituents, and trace elements) (63 sites), Volatile Organic Compounds (VOCs) (25 sites), radon gas (19 sites), radiochemistry (19 sites), and Groundwater Protection List (GWPL) pesticides (2 sites). Figure 1. The San Pedro River and its cottonwood-willow-mesquite riparian area are shown here near the community of Dudleyville. This riparian ecosystem is used by a diversity of birds, mammals, and reptiles unequaled in the United States. The resource value of this watercourse is such that the Nature Conservancy has listed the San Pedro River as one of the Last Great Places in the western hemisphere40. Introduction 2 Aspects of Study Groundwater quality concerns examined in this report include: < Current (2000) regional groundwater quality conditions; < Variation in groundwater quality using indices such as aquifers, geology, geographic location, and groundwater depth; and < Co-variation among concentrations of groundwater quality constituents. Reasons for Study - The LSP was selected for study for the following reasons: Figure 2. The varied landscape of the Lower San Pedro basin is captured in this panoramic view. Desert vegetation, a fallow agricultural field in the floodplain, the changing colors of the riparian forest, and the distant Gailuro Mountains are shown in this autumn pictorial. The steep gradient of the San Pedro River and its tributaries has resulted in a deeply dissected basin resulting in more exposed bedrock than in most alluvial areas in Arizona28. < Support of the hydrological analysis requirements of the ADEQ San Pedro watershed program in addition to county and local governments. < To increase groundwater quality data available for the LSP due to the area’s dependence on groundwater and the aquifer’s vulnerability to contamination 34. < Greater access to investigate groundwater quality because of recent population growth and an associated increase in the number of wells. Benefits of Study - This groundwater quality study was undertaken with the purpose of developing a reproducible scientific report utilizing statistical analysis to support conclusions concerning groundwater quality. It is anticipated this report will provide the following benefits: #1 - Many residents in the LSP obtain domestic supplies from private wells that are seldom tested for a wide variety of possible pollutants. While Arizona statutes require well drilling contractors to disinfect for possible bacteria contamination new wells which are to be used for human consumption, few wells are further tested for other groundwater quality concerns. Thus, contamination affecting groundwater pumped from private wells may go undetected for years and have the potential to contribute to adverse health effects for users of this resource. Testing all private wells for a wide variety of groundwater quality concerns would be prohibitively expensive. An affordable alternative is a statistically-based ambient study to characterize groundwater quality on a regional scale that identifies areas of impaired conditions. #2 - A process to evaluate potential groundwater quality impacts arising from a variety of sources including natural mineralization, mining, agriculture, livestock, septic tanks, and poor well construction. #3 - A process for evaluating the effectiveness of groundwater protection efforts such as aquifer protection permits and best management practices by tracking groundwater quality changes. #4 - A process for identifying future locations of public supply wells and wellhead protection areas. Introduction 3 Physical Setting The LSP is located in southeastern Arizona and lies entirely within the Basin and Range physiographic province. The basin consists of the northwesttrending San Pedro River alluvial fill and the surrounding elongated fault-block mountain ranges (Figure 3). Portions of Cochise, Graham, Pima, and Pinal Counties are within the basin. The LSP is about 65 miles long and varies from 10 to 25 miles wide, encompassing approximately 1,600 square miles 10. The LSP consists of the drainage basin of the San Pedro River between The Narrows north of the town of Benson to the confluence with the Gila River near the town of Winkelman, exclusive of the drainage of Aravaipa Creek east of the mouth of Aravaipa Canyon. It also includes the drainage of the Gila River at the boundary with Dripping Springs Wash Basin to where the Gila River exits the LSP near the town of Kelvin and enters the Donnelly Wash basin. The western border of the LSP is the drainage divide between the San Pedro and Santa Cruz Rivers along the Rincon, Santa Catalina, Black, and Tortilla Mountains. The east border is the drainage divide formed by the Johnny Lyon Hills, Galiuro, (Figure 3) and Dripping Springs Mountains. These ranges average from 6,000 feet above mean sea level (amsl) to over 9,000 feet amsl in elevation. Elevations along the valley floor range from 3,400 feet amsl at The Narrows along the San Pedro River at the basin’s southern end, to 1,700 feet amsl along the Gila River near Kelvin. The basin’s vegetation changes dramatically with elevation. From the cottonwood-willow-mesquite bosques found along portions of the San Pedro River, the vegetation transitions to a lower desert montage of mesquite, desert shrubs, grasses, and cacti. Oak/pine woodlands occur in mountain areas. Surface Water - The LSP is drained by two major waterways, the Gila River and the San Pedro River. The free-flowing San Pedro River enters from the south at the Narrows, an extensive hardrock formation located about 15 miles north of Benson. From the Narrows, the San Pedro flows north for 65 miles along the basin’s central axis until debouching into the Gila River near Winkelman (Figure 4). Figure 4. The co-mingling of waters from the San Pedro River and the Gila River during spring flow in 1995 is clearly seen here at the confluence near Winkelman. The San Pedro River, the largest freeflowing river in the Southwest, carries a thick, chocolate-colored silt load as the result of recent precipitation. In contrast, the Gila River, impounded approximately 25 miles upstream by Coolidge Dam, has had its silt-load drop out into San Carlos Reservoir and, thus is relatively clear. The San Pedro River’s main tributary within this reach is Aravaipa Creek which enters the basin from the east about 12 miles south of Winkelman. Aravaipa Creek is perennial only in its upper reaches and is ephemeral at its confluence with the San Pedro River10. The flow Introduction 4 Introduction 5 in the San Pedro River is perennial in places where the streambed intercepts hard rock or is fed by springs. Elsewhere, flow occurs only in direct response to precipitation47. Streams having perennial stretches in the LSP include the Gila River, a 3 mile portion of the San Pedro River located 9 miles south of Redington, and parts of the tributaries of Hot Springs Canyon, Redfield Canyon, and Harden Cienega Creek10. Figure 6. Ranches in this land of Western skies often advertise their presence using creative wrought iron gateways. Cattle grazing is the most extensive land use in this rugged, largely undeveloped basin. The Warbonnet Ranch sign is shown with the Winchester Mountains in the background, adding a threedimensional effect to the ranching scene. The regulated Gila River, impounded upstream in the San Carlos Reservoir by Coolidge Dam, enters the northeast portion of the LSP a few miles east of Winkelman. The river flows north and west for approximately 15 miles before exiting the basin near Kelvin. The Gila River’s main tributary in the northernmost section of the basin is Muddy Creek, which flows south from the Dripping Springs Mountains. Streams having perennial stretches in this watershed include Mineral Creek and Devils Canyon10. The LSP can be divided into four subwatersheds which are from south to north (Figure 3): Redington, Mammoth, Winkelman, and Kearny9. The Redington subwatershed extends from the Narrows northward to the U.S. Geological Survey (USGS) gaging station at Redington. The Mammoth subwatershed extends from Redington to the Mammoth gaging station located in Township 9 South, Range 16 East. The Winkelman subwatershed extends from the Mammoth gaging station northward to a gaging station near its confluence with the Gila River. The northern Kearny subwatershed contains all the lands north of the Winkelman gaging station. Climate - The LSP’s semiarid climate is characterized by hot summers and cool, moderate winters; climate becomes warmer and drier with decreasing elevation. Annual precipitation is extremely variable, averaging 10.5 inches at Redington, 19.5 inches at Oracle, and approximately 28 inches in the Santa Catalina Mountains28 47. Precipitation typically occurs during two periods: as intense rains of short duration produced by thunderstorms from July to September and as gentle, long-duration rains and some snow produced by frontal-type storms during the winter months47. May is the driest month while July and August are the wettest months. Thunderstorm runoff tends to be short-lived and localized. Cultural Setting Land ownership in the LSP (Figure 5) consists of State Trust (64 percent), Bureau of Land Management (12 percent), private (11 percent), Forest Service (10 percent), San Carlos Indian Nation (2 percent), and the Saguaro National Monument (1 percent) (8). Much of the land along the San Pedro River and Gila River floodplains is privately owned. Introduction 6 Introduction 7 Communities and their 2000 census data population figures (if large enough) within the basin, from south to north, are Cascabel, Redington, San Manuel (5,698), Oracle (2,065), Mammoth (2,065), Feldman, Dudleyville, Winkelman (440), Hayden (910), Kearny (2,545), and Kelvin 3. Cascabel, Redington, Feldman, and Dudleyville are small agriculturally-oriented communities. Oracle, after a brief mining period, became a ranching and health-seekers tourism center39. The other communities are strongly linked to the mining industry. Mining is the principal economic activity within the LSP with major copper operations located in the San Manual/Mammoth area (Broken Hill Properties or BHP) and in the Hayden/Kearny/Winkelman area (American Smelting and Refining Company or ASARCO). These communities are attempting to diversify their economic base because of the cyclical nature of the mining industry. Agriculture has traditionally contributed to the basin’s economy through cattle ranches (Figure 6) and farms located along river floodplains. In 1990, approximately 6,500 acres (Figure 7) were irrigated in the basin 10. Tourist, retirement, and retail are growing sectors of the local economy. The lack of good transportation through the LSP, especially the absence of a railroad south of Winkelman and the rough dirt roads found south of San Manuel have been suggested as reasons for the underdeveloped economy of the LSP39. Historical Development - Prior to European settlement of the LSP, the area was inhabited by nomadic groups of Apache Indians39. Conflict between these groups led to the establishment of Camp Grant in 1860. Ranches and farms were established along the San Pedro River, until they were largely abandoned when the military closed Camp Grant in 187139. Prospectors began exploring the area in the late 1870's. This led to the establishment of several mining districts: the Old Hat in the Santa Catalina Mountains, the Bunker Hill in the Galiuro Mountains, the Saddle Mountain in The Tablelands, and the San Pedro in the Tortilla Mountains39. To supply food and feed to the mining operations, settlers once again began farming. During the 1890s, floods carried away many acres of farmland. These floods may have been due to heavy rains following long periods of drought and by the overgrazing of cattle 39. By 1930, only a few farms remained as the continued operation of diversion dams on the San Pedro River and their accompanying irrigation ditches proved too difficult. Mesquite brush subsequently invaded the many abandoned farm fields. Figure 7. A field of barley in the floodplain of the San Pedro River near Dudleyville. Most crops grown in the LSP, including small grains, alfalfa, and pasture, are used for animal feed. Many farms in this area are owned by mining companies and crops are grown primarily to preserve water rights related to appropriable sub-flow. Cottonwoods along the San Pedro River, Malapais Hill, and the Dripping Springs Mountains can be seen in the background. The San Manual/Mammoth area was originally mined for gold, silver, and minor amounts of copper until molybdenum extraction began in 193639. In the 1950s, large scale copper mining began at San Manuel. Both underground and open pit mines, a concentrator, smelter, refinery, and rod manufacturing plant were located in this town. In 1996, the operation was acquired by BHP from Magma Copper Company (Figure 8). This operation, which included the largest underground metal mine in North America, ceased production in June 199923. Introduction 8 The Ray/Kearny/Winkelman area is also a major copper producer. A copper smelter was built at the town of Hayden in 1912 to process ores from the nearby Ray Mine. Another smelter was built at the Ray Mine and processed the mine concentrates from 1958 until 1983 when once again the ore was shipped to the Hayden smelter1. Currently the mining operation consists of an open-pit mine and a solvent extraction and electrowinning plant at the Ray Mine and a smelter in Hayden. Kearny, a company town founded in 1958, and Winkelman are primarily residential communities for mining employees. Figure 8. The San Manuel copper mining complex, including the smelter smokestack and tailings piles are shown in this photo. Groundwater from the underground mining operations had been pumped at a rate of 4,000 gpm and applied to the tailings piles for dust control. This practice ended in January 2002 when a four inch cover of rock material capped the more than 3,000 acres of tailings dumps23. GEOHYDROLOGY Geology Figure 9. Powered by a turbine pump, a well draws groundwater from the floodplain aquifer for delivery to a field planted with cotton seed. Furrow irrigation systems are used to distribute water to scattered fields of cotton grown between the towns of Mammoth and Kearny. Recently, some fields are being replanted to riparian vegetation in an attempt to replace willow flycatcher habitat lost during the recent expansion of Roosevelt Dam and Lake. The pictured field is located near the confluence of the San Pedro River and Aravaipa Creek. The San Pedro River occupies a north-south trending structural trough bounded on the east and west by mountain ranges. These surrounding mountains (Figure 5) are composed of granitic, volcanic, sedimentary, and metamorphic rocks 35. This trough has filled with sediments deposited from the adjacent mountain ranges 35. The relatively steep gradient of the Geohydrology 9 San Pedro River, up to 30 feet per mile, has deeply dissected the LSP more so than other desert basins28. Tributary stream gradients are also correspondingly higher, and consequently the basin has more exposed bedrock than other basins. Of particular interest to groundwater quality are the sandstone beds that grade into gypsiferous silt containing economicallyviable gypsum beds in the central part of the valley in the Mammoth-Winkelman area47. Aquifers Groundwater in the LSP is found in four principal water-bearing units: the floodplain aquifer, the unconfined and confined basin-fill aquifers, and in the consolidated hardrock mountain areas (Figure 13). The floodplain and both basin-fill aquifers have the ability to transmit and supply large amounts of groundwater; the hardrock yields limited groundwater from areas sufficiently faulted and fractured10. The streambed alluvium forming the floodplain aquifer is more permeable than the alluvial basin-fill sediments that fill the valley; however, the narrow floodplain aquifer has a very limited extent along the LSP’s central valley. The floodplain aquifer is found in close proximity to the San Pedro River, the Gila River, and their major tributaries (Figure 9). The aquifer is 40 to 150 feet thick and consists of gravel, sand, silt, and clay35. The floodplain width averages about half a mile, though large tributaries such as Aravaipa and Hot Springs Creeks have flood plains as much as a mile wide at their mouths28. This very permeable aquifer has well yields averaging from 250 to 2,700 gallons per minute (gpm) 10. Groundwater in this aquifer is unconfined, and water levels are usually less than 60 feet below land surface (bls)35. The floodplain aquifer is recharged primarily by surface water flows of the San Pedro and Gila Rivers; this results in seasonal water level fluctuations in response to surface water flows in the riverbed41. Groundwater levels typically rise slightly in the spring and early summer and decline in the fall and winter41. The unconfined basin-fill aquifer is composed of younger basin-fill, older basin-fill, and basal conglomerate, which makes for highly variable hydrologic characteristics depending upon the amount of compaction and the presence of finegrained layers in the basin-fill10. The younger and Figure 10. An artesian well creates a riparian area amidst a mesquite bosque near the San Pedro River just south of the town of Mammoth. Tapping the confined basin-fill aquifer, this 1485 foot deep well drilled in 1934 spills water out of the casing at a hot 38.6 degrees Celsius. Groundwater chemistry–very soft with elevated levels of pH and fluoride-is suggestive of a chemically-closed system. older basin-fill units generally provide the bulk of water pumped from the regional aquifer, with reported well yields of 70 to 1,900 gpm41. In contrast, well yields from tightly cemented basal conglomerate are only several hundred gpm and found only in areas that are weakly cemented or fractured by faults 41. The confined basin-fill aquifer is encountered in most wells drilled deeper than 500 feet (Figure 10). These deep wells located in or near the river’s floodplain encounter fine-grained layers that restrict vertical groundwater movement, creating artesian conditions28. Two main zones of artesian activity are associated with sand and gravel layers from 600 to 800 feet and from 1,200 to 1,300 feet in depth41. Discharge from artesian conditions span the San Pedro River’s floodplain from about 5 miles north to 10 miles south of Mammoth10. The discovery of the Geohydrology 10 confined aquifer may be traced to the oil rush of 1904 after it was observed that water coming from wells around Mammoth contained colored spots that looked very much like drops of oil on water39. Oil speculators quickly purchased all the land around the town. The oil rush ended quickly when well drillers encountered artesian water39. Groundwater is extracted from the consolidated hardrock of the mountains surrounding the basin where the bedrock is sufficiently fractured or faulted10. Fault Figure 11. Successful field work sometimes requires hydrologists to think–and resemble–the zones create small, localized wells they sample. ADEQ’s Elizabeth Boettcher (above) accurately parrots this derelict aquifers that are tapped by windmill’s form while examining its missing blades. This cultural icon of the West is fast becoming a museum piece because of expensive and time-consuming maintenance costs. windmills (Figure 11) and Windmills are increasingly non-operable and the water tanks formerly supplied using wind power other low-capacity wells for are now filled by ranchers using submersible pumps powered by portable generators or solar stock and domestic use. energy. Abandoned windmills are left to slowly deteriorate but serve as excellent observation Springs issue water from posts for vertigo-free souls. bedrock, typically with low flows, although Leroy Groundwater Recharge - Recharge occurs in the LSP Spring, located 6 miles upstream from Winkelman through four routes 10: along the San Pedro River has an average flow of • Mountain-front recharge; 1,032 gpm47. • Sreambed infiltration; • Underflow from Aravaipa Canyon basin; and Groundwater Characteristics • Underflow from the Upper San Pedro basin. Groundwater movement in the basin is from the Mountain-front recharge occurs through surface higher mountain elevations toward the valley; runoff flowing off mountain bedrock and infiltrating however little if any moves northwest along the 39 riverbed . Groundwater moves readily between the the permeable sediments on surrounding alluvial fans. This is the main source of replenishment to the floodplain aquifer and unconfined basin-fill basin-fill aquifers 10. Streambed infiltration is the main aquifer10. The unconfined basin-fill aquifer, and recharge source for the floodplain aquifer as well as especially the floodplain aquifer, may also receive providing some recharge to the basin-fill aquifers. water leaking upwards from the artesian confined Streambed infiltration occurs when surface water aquifer in the Mammoth area41. The LSP contains an flows in the Gila and San Pedro Rivers and their estimated 25.6 million acre-feet in storage10. tributaries infiltrate through coarse riverbeds10. Groundwater levels are generally stable in the basin In the LSP, total recharge is estimated at 25,000 acreexcept in the area around San Manuel and Mammoth feet per year (af/yr). Mountain front recharge and where large groundwater pumpage rates are causing streambed infiltration contribute 24,000 af/yr, while water-level declines 9. Depth to water in unconfined underflow from Aravaipa Canyon basin is 800 af/yr areas of the basin-fill in 1978 ranged from 50 to 253 and 120 af/yr from the Upper San Pedro basin 9. feet bls 35. Geohydrology 11 Groundwater Discharge Groundwater discharge from the LSP occurs through five processes: pumpage from wells; evapotranspiration from phreatophytes and crops; evaporation from surface water in riverbeds; by discharge from springs and seeps; and through underflow to the Donnelly Wash Basin 9. Pumpage from wells is considered the largest source of discharge and, in the late 1980s, was estimated to total approximately 36,000 af 9. Of this total well discharge, 59 percent was for mining use (Figure 12), 37 percent for irrigation use, 4 percent for public supply and/or domestic use10. Figure 12. Groundwater quality assessments are much easier and complete when local sources of hydrologic knowledge are utilized. ASARCO’s Kip Gambee (pictured in hard hat with Maureen Freark of ADEQ) is one such fount. These hydrologists are posing next to one of the high-capacity mining wells located in the ASARCO wellfield near the confluence of the Gila and San Pedro Rivers. Mining is the single largest water use in the Lower San Pedro basin. GROUNDWATER SAMPLING RESULTS To characterize the regional groundwater quality of the LSP, ADEQ personnel sampled 63 groundwater sites (Figure 13) consisting of 46 wells (Figure 5) and 17 springs (Figure 14). The 46 wells consisted of 4 artestian, 23 domestic with submersible pumps, 9 irrigation with turbine pumps, 2 mining with turbine pumps, 4 public water-supply with submersible pumps, and 4 stock windmills. Information on locations and characteristics of groundwater sample sites is provided in Appendix A. At the 63 sites, the following types of samples were collected: < < < < < 63 inorganic samples; 25 VOC samples; 19 radon samples; 19 radiochemistry samples; and 2 pesticide samples. Water Quality Standards/Guidelines As an environmental regulatory agency, the most important determination ADEQ makes concerning the collected samples is how the analytical results compare to various water quality standards. Three sets of drinking water standards which reflect the best current scientific and technical judgment available on the suitability of water for drinking purposes were used to evaluate the suitability of these groundwater sites for domestic purposes: • Federal Safe Drinking Water (SDW) Primary Maximum Contaminant Levels (MCLs). These enforceable health-based standards establish the maximum concentration of a constituent allowed in water supplied by public systems 54. • State of Arizona Aquifer Water-Quality Standards apply to aquifers that are classified for drinking water protected use5. Currently all aquifers within Arizona are for drinking water use. These enforceable State standards are almost identical to the federal Primary MCLs. • Federal SDW Secondary MCLs . These nonenforceable aesthetics-based guidelines define the maximum concentration of a constituent that can be present without imparting unpleasant taste, color, odor, or other aesthetic effect on the water54. Groundwater Sampling Results 12 Groundwater Sampling Results 13 Water Quality Standard/Guideline Exceedances Health-based Primary MCL water quality standards and State aquifer water quality standards were exceeded at 11 of 63 sites (18 percent) (Figure 13)(Table 1). Constituents above Primary MCLs include antimony (2 sites), arsenic (1 site under the current standards; 12 sites under the 2006 standards) (Figure 15), fluoride (8 sites) (Figure 16), nitrate as nitrogen (1 site), gross alpha (2 sites), and uranium (1 site). and adequate drainage are necessary. Excessive levels of sodium are known to cause physical deterioration of the soil56. Irrigation water may be classified using specific conductivity (SC) and the Sodium Adsorption Ratio (SAR) in conjunction with one another. The majority of sites in the LSP have a low sodium hazard and a low-to-high salinity hazard when used for irrigation (Figure 19). Generally, only confined aquifer sites had sodium hazards while floodplain aquifer sites had salinity hazards. Analytical Results In addition, if 2006 arsenic standards are considered, 18 of 63 sites (29 percent) would have exceeded at least one Primary MCL. Potential health effects of these Primary MCL exceedances are also provided in Table 1. Aesthetics-based Secondary MCL water quality guidelines were exceeded at 31of 63 sites (49 percent) (Table 2)(Figure 13). Constituents above Secondary MCLs include: chloride (2 sites), fluoride (16 sites) (Figure 16), iron (4 sites), manganese (9 sites) (Figure 15), pH (4 sites) (Figure 17), sulfate (11 sites) (Figure 18), and TDS (24 sites) (Figure 18). Analytical inorganic and radiochemistry results of the 63 sample sites are summarized (Table 3) using the following indices: minimum reporting levels (MRLs), number of sample sites over the MRL, upper and lower 95 percent confidence intervals (CI95%), and the median and mean. Confidence intervals are a statistical tool which indicates that 95 percent of a constituent’s population lies within the stated confidence interval. Specific constituent information for each groundwater site is found in Appendix B. Radon is a naturally occurring, intermediate breakdown product from the radioactive decay of uranium-238 to lead-20620. There are widely conflicting opinions on the risk assessment of radon in drinking water, with drinking water standards varying from 300 piC/l to 4,000 piC/l20. Sixteen of the 19 sites exceeded the 300 piC/l proposed standard; none exceeded the 4,000 proposed standard. Suitability for Irrigation The suitability of groundwater at each sample site was assessed as to its suitability for irrigation use based on salinity and sodium hazards. With increasing salinity levels, leaching, salt tolerant plants, Figure 14. In remote mountainous areas, groundwater samples are often collected from springs as typically few wells exist in these rugged areas. Ranchers use these springs to water their livestock, often developing them so that the water flows out of a pipe into a series of troughs. The flow rate of springs can vary from figuratively drops per minute to higher flows which can sustain their own riparian area. Davis Spring, located on the eastern slope of the Santa Catalina Mountains, is an example of the latter with its valley location clearly marked by an abundance of verdant, water-loving, deciduous tress. Groundwater Sampling Results 14 Table 1. LSP Sites Exceeding Health-Based Water Quality Standards (Primary MCLs) Constituent Primary MCL Sites Exceeding Primary MCLs Concentration Range of Exceedances Health Effects Nutrients Nitrite (NO2-N) 1.0 0 -- Methemoglobinemia Nitrate (NO3-N) 10.0 1 30 Methemoglobinemia Trace Elements Antimony (Sb) 0.006 2 0.0073 - 0.75 Cancer Arsenic (As) 0.05 0.01* 1 12* 0.11 0.011 - 0.11 Dermal and nervous system toxicity Barium (Ba) 2.0 0 -- Circulatory system damage Beryllium (Be) 0.004 0 -- Bone and lung damage Cadmium (Cd) 0.005 0 -- Kidney damage Chromium (Cr) 0.1 0 -- Liver and kidney damage Fluoride (F) 4.0 8 4.0 - 13 Skeletal damage 0.002 0 -- Central nervous system disorders; kidney damage Nickel (Ni) 0.1 0 -- Heart and liver damage Selenium (Se) 0.05 0 -- Gastrointestinal damage Thallium (Tl) 0.002 0 -- Gastrointestinal damage; liver, kidney, and nerve damage Mercury (Hg) Radiochemistry Constituents Gross Alpha 15 piC/l 2 19 - 68 piC/l Cancer Ra-226 + Ra-228 5 piC/l 0 -- Bone cancer 30 Fg/l 1 61.5 Fg/l Uranium All units in mg/l except gross alpha, radium-226+228, and uranium. * new arsenic primary MCL scheduled to be implemented in 2006 Source: 54 57 Groundwater Sampling Results 15 Groundwater Sampling Results 16 Groundwater Sampling Results 17 Table 2. LSP Sites Exceeding Aesthetics-Based Water Quality Standards (Secondary MCLs) Constituents Secondary MCL Sites Exceeding Secondary MCLs Concentration Range of Exceedances Aesthetic Effects Physical Parameters pH - field 6.5 to 8.5 4 8.53 - 9.24 su Corrosive water General Mineral Characteristics TDS 500 24 500 - 2850 mg/l Unpleasant taste Major Ions Chloride (Cl) 250 2 705 - 810 mg/l Salty taste Sulfate (SO 4 ) 250 11 260 - 1100 mg/l Rotten-egg odor, unpleasant taste, and laxative effect Trace Elements Fluoride (F) 2.0 16 2.0 - 13 mg/l Mottling of teeth enamel Iron (Fe) 0.3 4 0.34 - 2.1 mg/l Rusty color, reddish stains, and metallic tastes Manganese (Mn) 0.05 9 0.056 - 0.76 mg/l Black oxide stains and bitter, metallic taste Silver (Ag) 0.1 0 -- Skin discoloration and greying of white part of eye Zinc (Zn) 5.0 0 -- Metallic taste All units mg/l except pH is in standard units (su). Source: 31 54 57 Groundwater Sampling Results 18 Groundwater Sampling Results 19 Groundwater Sampling Results 20 Table 3. Summary Statistics for LSP Groundwater Quality Data Constituent Minimum Reporting Limit (MRL) Number of Samples Over MRL Lower 95% Confidence Interval Median Mean Upper 95% Confidence Interval Physical Parameters Temperature ( o C) N/A 60 20.1 20.9 21.3 22.5 pH-field (su) N/A 63 7.50 7.45 7.63 7.76 pH-lab (su) 0.01 63 7.59 7.60 7.69 7.79 Turbidity (ntu) 0.01 63 - 0.33 0.41 3.18 6.69 220 209 227 General Mineral Characteristics Total Alkalinity 2.0 63 192 Phenol. Alkalinity 2.0 5 SC-field (FS/cm) N/A 63 637 656 810 982 SC-lab (FS/cm) N/A 63 684 700 872 1061 Hardness 10.0 63 219 250 266 312 TDS 10.0 63 428 440 549 671 > 80% of data below MRL Major Ions Calcium 5.0 63 61 72 75 89 Magnesium 1.0 62 14.9 18.0 18.6 22.2 Sodium 5.0 62 58 51 91 123 Potassium 0.5 61 2.8 3.0 3.5 4.2 Bicarbonate 2.0 63 231 270 253 275 Carbonate 2.0 5 Chloride 1.0 62 21 21 55 90 Sulfate 10.0 58 101 72 155 209 0.5 1.5 2.6 > 80% of data below MRL Nutrients Nitrate (as N) 0.02 54 0.5 Nitrite (as N) 0.02 3 > 80% of data below MRL Ammonia 0.02 11 > 80% of data below MRL TKN 0.05 33 0.06 0.06 0.27 0.48 Total Phosphorus 0.02 38 0.036 0.035 0.054 0.072 All units mg/l except where noted with physical parameters Source: 43 Groundwater Sampling Results 21 Table 3. Summary Statistics for LSP Groundwater Quality Data--Continued Constituent Minimum Reporting Limit (MRL) Number of Samples Over MRL Lower 95% Confidence Interval Median Mean Upper 95% Confidence Interval Trace Elements Antimony 0.005 2 > 80% of data below MRL Arsenic 0.01 13 > 80% of data below MRL Barium 0.1 6 > 80% of data below MRL 0.0005 0 > 80% of data below MRL 0.1 28 Cadmium 0.001 1 > 80% of data below MRL Chromium 0.01 1 > 80% of data below MRL Copper 0.01 2 > 80% of data below MRL Fluoride 0.20 61 Iron 0.1 8 > 80% of data below MRL Lead 0.005 1 > 80% of data below MRL Manganese 0.05 9 > 80% of data below MRL 0.0005 0 > 80% of data below MRL 0.1 0 > 80% of data below MRL Selenium 0.005 11 > 80% of data below MRL Silver 0.001 0 > 80% of data below MRL Thallium 0.005 0 > 80% of data below MRL Zinc 0.05 13 > 80% of data below MRL Beryllium Boron Mercury Nickel 0.09 1.09 0.05 0.93 0.15 1.62 0.22 2.15 Radiochemical Constituents Radon* Varies 19 (out of 19) 366 385 507 647 Gross Alpha* Varies 18 (out of 19) 1.5 4.6 8.8 16.1 Gross Beta* Varies 16 (out of 19) 2.1 2.6 4.0 5.9 Ra-226* Varies 0 (out of 9) > 80% of data below MRL Uranium** Varies 2 (out of 2) > 80% of data below MRL All units mg/l except * = piC/l and ** = Fg/l Source: 43 Groundwater Sampling Results 22 pesticides or their products of degradation on the list were detected at any of the sites. Appendix D contains a list of the pesticides on the GWPL. Sodium Adsorption Ratio (SAR) 30 GROUNDWATER COMPOSITION 20 Groundwater in the LSP was characterized by qualitative classifications, chemistry, and crosscorrelation of constituent concentrations. 10 0 0 1000 2000 3000 4000 Specific Conductivity (uS/cm) 5000 Figure 19. This graph illustrates that salinity is generally more of a hazard than sodium to successful plant growth. The salinity hazard is considered “medium” at SC levels > 250 uS/cm and “high” at > 750 uS/cm. In contrast, the sodium hazard is considered “low” when the SAR is less than 8. This typically only occurs with confined basin-fill aquifer sites56. The VOC and pesticide analytical results are provided in Appendix B and summarized as follows: VOC Results - Analytical results of the VOC samples collected at 25 sites revealed detections at only two sites. Chloroform, an organic disinfection byproduct of drinking water systems using free chlorine, was detected (4.4 Fg/l) in the sample collected from a public water supply well near Kearny. Detections of methylethyl ketone and another unidentified compound occurred in a sample collected from a well located in the floodplain south of Mammoth. These compounds are not target compounds listed by either EPA method 601 or 602 but were identified by the ADHS laboratory. These detections were probably caused by glue used for PVC piping. The well owner added a sample port at the wellhead the day before sampling by ADEQ. None of the other 34 VOC compounds on the EPA 601/602 VOC list, including the gasoline oxygenate, Methyl tertiary-Butyl Ether (MTBE), were detected at any sites. Analytes on the EPA 601/602 VOC list is found in Appendix C. Pesticide Results - Analytical results of the two samples collected for Groundwater Protection List (GWPL) analysis indicated that none of the 76 General Summary - Groundwater in the LSP is generally fresh, slightly-alkaline, and varies widely in hardness concentrations. TDS concentrations (Figure 18) were considered fresh (below 1,000 mg/l) at 59 sites while 4 sites were slightly saline (1,000 to 3,000 mg/l)27. Among cations, sodium plays the greatest role in predicting TDS concentrations while among anions, the best predictor is chloride. Overall among major ions, sodium is by far the best predictor of TDS concentrations (multiple regression analysis, p # 0.05). Levels of pH were slightly-alkaline (above 7 su) at 60 sites and slightly-acidic (below 7 su) at 3 sites 22. Hardness concentrations (Figure 16) were divided into soft (9 sites), moderately hard (5 sites), hard (29 sites), and very hard (20 sites)21. Nutrient concentrations were generally low with only nitrate, total phosphorus, and total Kjeldahl nitrogen (TKN) detected at more than 20 percent of the sites. Nitrate (as nitrogen) concentrations were divided into natural background (15 sites at < 0.2 mg/l), may or may not indicate human influence (40 sites between 0.2 - 3.0 mg.l), may result from human activities (6 sites between 3.0 - 10 mg/l), and probably result from human activities (1 site > 10 mg/l)38. Most trace elements were rarely detected. These include antimony, arsenic, barium, beryllium, cadmium, copper, iron, lead, manganese, mercury, nickel, selenium, silver, and thallium. Only boron and fluoride (Figure 16) were detected at more than 20 percent of the sites while arsenic (Figure 15), barium, iron, manganese (Figure 15), selenium, and zinc were detected at more than 10 percent of sites. Groundwater Chemistry - The chemical composition of the 63 groundwater sites in the LSP is illustrated using several methods. The groundwater chemistry of each site is mapped in Figure 18 and plotted using Piper trilinear diagrams in Figure 20. These figures revealed several patterns. The cation triangle Groundwater Composition 23 unconfined basin-fill sites (clustered within the purple border) were generally calciumbicarbonate, floodplain sites (clustered within the green border) were generally mixed-mixed, and confined basin-fill sites (clustered within the blue border) were generally sodium-mixed. Groundwater chemical evolution is hypothesized to follow the pink arrow, changing from calcium-bicarbonate to mixedmixed to sodium-mixed46. Constituent Covariation - The covariation of constituent concentrations from the 63 sites were determined to scrutinize the strength of the association. The results of each combination of constituents were examined for statistically-significant, positive or negative correlations. A positive correlation occurs when, as the level of a constituent increases or decreases, the concentration of another constituent also correspondingly increases or decreases. A negative correlation occurs when, as the Figure 20 . Sample sites plotted on a Piper tri-linear diagram illustrates concentration of a constituent increases, the that aquifers in the LSP generally have characteristic groundwater concentration of another constituent chemistries as indicated by the colored borders. The groundwater evolution decreases, and vice-versa. A positive flowpath is thought to follow the route indicated by the pink arrows. correlation indicates a direct relationship between constituent concentrations, a diagram (lower left in Figure 20) shows that the negative correlation indicates an inverse relationship. dominant (> 50 percent) cation is calcium at 24 sites, sodium at 23 sites, magnesium at 1 site, and is mixed The overall basin (63 sites) had many significant (no constituent > 50 percent) at 15 sites. The anion correlations among constituents (Pearson Correlation triangle diagram (lower right in Figure 20) shows that Coefficient test, p# 0.05). The most prevalent pattern the dominant anion (> 50 percent) is bicarbonate at 38 involved the positive correlation among TDS, SC, sites, sulfate at 6 sites, chloride at 1 site, and is mixed hardness, major ions (calcium, magnesium, sodium, (no constituent > 50 percent) at 18 sites. The cationpotassium, sulfate (Figure 21), and chloride), nitrate, anion diamond diagram (in the center of Figure 20) and boron. Other constituents such as pH-field, shows that the groundwater chemistry is highly temperature, and fluoride exhibited unique patterns. variable in the basin. With pH-field, a positive correlation occurred with fluoride and temperature: in contrast, negative Water chemistries found in the LSP include: calciumcorrelations occurred with hardness (Figure 22), bicarbonate (22 sites), mixed-bicarbonate (12 sites), calcium, magnesium, bicarbonate, and nitrate. sodium-mixed (10 sites), mixed-mixed (8 sites), Temperature was positively correlated with pH-field sodium-bicarbonate (4 sites), calcium-sulfate and and fluoride; in contrast, negative correlations mixed-sulfate (2 sites apiece), and mixed-chloride, occurred with bicarbonate and potassium. Fluoride sodium-sulfate, and magnesium-sulfate (1 site apiece). was positively correlated with temperature, pH-field, sodium, sulfate, boron, gross alpha, and gross beta; The 63 groundwater sites were divided into four negative correlations occurred with bicarbonate. aquifers for chemical comparison: hardrock, Each of the four aquifers examined separately for unconfined basin-fill, floodplain, and confined basinsignificant correlations exhibited different patterns fill. Empirical patterns appeared with each group and (Pearson Correlation Coefficient test, p# 0.05). are highlighted in Figure 20. Hardrock and Conclusions 24 800 The confined basin-fill aquifer (4 sites) had a positive correlation among TDS, SC, hardness, turbidity, the major ions, and boron. The only significant correlations involving pH-field and fluoride was a positive one with each other. Temperature was not correlated to any other constituents. 600 GROUNDWATER QUALITY PATTERNS 400 Groundwater in the LSP was characterized by assessing the spatial variation of groundwater quality among aquifers, geologic classifications, and watersheds as well as the variation of groundwater quality in relation to groundwater depth. Sulfate (mg/l) 1000 200 0 0 1000 2000 TDS (mg/l) 3000 Figure 21 . The positive correlation between TDS and sulfate is shown above (Pearson Correlation Coefficient, p # 0.01). The highest sulfate concentrations are typically found in the floodplain aquifer between Mammoth and Kearny and may be the result of elevated sulfate concentrations in surface water flow, gypsum deposits, and extensive mine tailings in the area. The floodplain aquifer (27 sites) showed similar patterns to the overall basin, but with interesting differences. Again the major pattern is the positive correlations among TDS, SC, hardness, major ions, boron and fluoride (instead of nitrate). Very different patterns emerged with pH-field, temperature, and fluoride. With pH-field, a positive correlation occurred with TDS, hardness, calcium, magnesium, bicarbonate, and sulfate. There were no significant correlations with temperature. Fluoride had the above-noted positive correlations. The hardrock aquifer (23 sites) also exhibited similar patterns to the overall basin but with unique differences. Again the major pattern is the positive correlations among TDS, SC, hardness, major ions, nitrate, and boron. With pH-field, negative correlations occurred with TDS, SC, hardness, calcium, magnesium, and bicarbonate. Temperature had a negative correlation with nitrate. Fluoride was positively correlated with sodium, gross alpha, and gross beta; negative correlations occurred with hardness and calcium. The unconfined basin-fill aquifer (9 sites) had a positive correlation among TDS, SC, hardness, turbidity, the major ions, nitrate, and boron. There were no significant correlations involving pH-field, temperature, and fluoride. Aquifer Comparison - Analytical results were compared between the four major aquifers in the LSP: floodplain (27 sites), unconfined basin-fill (9 sites), confined basin-fill (4 sites), and hardrock (23 sites) to examine for significant differences. Three constituents, pH-field, sodium, and fluoride (Figure 23), were higher in the confined basin-fill aquifer than in the other three aquifers. Four other constituents had unique patterns. Temperature was higher in the confined basin-fill aquifer than in hardrock. Bicarbonate/total alkalinity was lower in the confined basin-fill aquifer than in the floodplain 1500 Hardness as CaCO3 (mg/l) 1200 1000 500 0 6 7 8 pH-field (su) 9 10 Figure 22. Hardness and pH have a negative correlation (Pearson Correlation Coefficient, p # 0.01). Calcium, a major component of hardness, is typically removed from solution by precipitation of calcium carbonate and formation of smectitie clays while pH typically increases downgradient through silicate hydrolysis reactions44. Groundwater Quality Patterns 25 In many cases, the confined basin-fill aquifer sites were data outliers which may have been masking other patterns. For this reason, the four confined basin-fill aquifer sites were deleted from the data set and analytical results were compared between three LSP aquifers: floodplain, unconfined basin-fill, and hardrock to examine for significant differences. 600 500 Bicarbonate (mg/l) aquifer and hardrock; and in the unconfined basin-fill aquifer than in the hardrock (Figure 24). Sulfate was lower in hardrock than in the confined basin-fill aquifer and the floodplain aquifer. Finally, potassium was higher in the floodplain aquifer than in the hardrock (Kruskal-Wallis test in conjunction with Tukey test, p# 0.05). 400 300 200 100 0 Six constituents--SC, TDS, sodium, potassium, sulfate, and fluoride–were higher in the floodplain aquifer than in hardrock. Bicarbonate/total alkalinity was higher in hardrock than in the unconfined basin-fill aquifer (Kruskal-Wallis test in conjunction with Tukey test, p# 0.05). Fluoride (mg/l) 15 10 5 0 in ed pla nfin od o Co l F k oc rdr Ha d fine on c Un Aquifer Figure 23. Fluoride concentrations are frequently elevated over Primary and Seconday MCLs in the confined, basin-fill aquifer. At these sites, calcium appears to be an important control on fluoride through precipitation of the mineral, fluorite44. These sites had depleted levels of calcium constituting a small percentage of the total cation concentration. in ed pla nfin od o Co l F ock rdr Ha d fine con n U Aquifer Figure 24 . Bicarbonate concentrations are higher in hardrock than in the confined and unconfined-basin fill aquifers and in the floodplain aquifer than in the confined basin-fill aquifer (Kruskal-Wallis test, p # 0.05). These patterns support earlier reports that indicate most recharge occurs in the hardrock mountains and along river floodplains28. Floodplain Aquifer Comparison - Analytical results were compared for groundwater quality data collected in the floodplain aquifer between the four watersheds: Redington, Mammoth, Winkelman, and Kearny to examine for significant constituent concentration differences along this flowpath . Three patterns were revealed. SC and sodium (Figure 25) were higher in the Kearny watershed than in the Redington and Winkelman watersheds. Potassium and chloride (Figure 26) were higher in the Kearny watershed than in the other three watersheds. Finally, fluoride was higher in the Mammoth watershed than in the other three watersheds (Kruskal-Wallis test in conjunction with Tukey test, p# 0.05). Geological Comparison - Hardrock sites in the LSP were divided into four rock types (Figure 10): sedimentary (17 sites), volcanic (7 sites), granitic (6 sites), and metamorphic (1 site) that are interspersed Groundwater Quality Patterns 26 temperature (Figure 28), and bicarbonate/total alkalinity had concentrations that increased with increasing groundwater depth (regression analysis, p # 0.05). Constituent concentrations from sample sites in the four aquifers (floodplain, confined basin-fill, unconfined basin-fill, and hardrock) were compared with groundwater depth for significant trends within each aquifer. No significant trends were found within the floodplain, and unconfined basin-fill aquifers as well as hardrock. Total alkalinity concentration was found to decrease with increasing groundwater depth bls (regression analysis, p # 0.05). 200 100 Groundwater Quality Time Trend Analysis 0 th n ton mo ma ing m d kel a e n i M R 2 13-W rny ea K 4 Watershed Figure 25 . Sodium concentrations in the floodplain aquifer generally increase from upgradient (left) to downgradient (right) watersheds, particularly in the most downgradient, Kearny. This may be partially due to recharge from the Gila River that has higher salt levels than are found in the San Pedro River7 56. throughout mountainous areas of the basin. Analytical results were again examined for concentration differences. No significant patterns were revealed with this geological comparison (Kruskal-Wallis test, p# 0.05). Geographic Comparison - The LSP was divided into southern (upgradient) and northern (downgradient) sub-basins at the USGS gauging station at Mammoth for further analyses. TDS (Figure 27), SC, hardness, calcium, magnesium, sodium, potassium, chloride, and sulfate had higher concentrations in the northern, downgradient portion than the southern, upgradient portion. In contrast, pH values were higher in the southern, upgradient portion than in the northern, downgradient portion (Kruskal-Wallis test, p# 0.05). Groundwater Depth Comparison - The vertical variation of groundwater quality was examined by comparing constituent concentrations with groundwater depth below land surface (bls) for the 63 sites in the LSP. Many constituent concentrations tended to significantly decrease with increasing groundwater depth bls. Hardness, calcium, magnesium, sodium, chloride, fluoride, and boron followed this pattern. In contrast, pH-field, A time-trend analysis (Table 4) compared groundwater quality data collected from six ADEQ sites previously sampled in the early 1950s by the USGS28. 250 200 Chloride (mg/l) Sodium (mg/l) 300 150 100 50 0 n n oth ma gto mm kel din a n e i 2-M 1-R 3-W rny ea 4-K Watershed Figure 26 . Chloride increases in the Kearny watershed is even more dramatic than with sodium. Gila River recharge to the floodplain aquifer probably accounts for much of this increase. Degradation of Gila River water quality is caused by irrigation-return flows and highly-mineralized springs and flowing artesian wells, particularly in times of low flows10. Groundwater Quality Patterns 27 Table 4. Time-Trend Comparison of LSP Sample Sites LSP-11 LSP-14 LSP-24 LSP-37/38 LSP-54 LSP-63/64 1950/1999 -% Difference 1950/1999 -% Difference 1951/2000 - % Difference 1950/2000 - % Difference 1965/2000 - % Difference 1950 /2000 - % Difference Constituent Physical Parameters and General Mineral Characteristics Temp. ( 0 C) 42 - 38 SC (FS/cm) 683 - 700 2% 928-1100 17% Alk., Total -- -- 9% 21 - 20.8 0% 42 - 34 22% 20 - 21.4 7% 20 - 17.7 12% 27 - 22 20% 287 - 290 1% 457 - 430 6% 614 - 608 1% 338 - 330 -- 218 - 180 19% 263 - 270 3% -- 2% Hardness 36 - 32 12% 284 - 310 9% 12 - 9.2 26% -- 310 - 310 0% 158 - 160 1% TDS 441 - 450 2% 624 - 700 6% 218 - 195 11% -- 376 - 380 1% 205 - 195 5% Major Ions Calcium 12 - 12 0% 84 - 95 6% 4 - 3.5 13% -- 60 - 69 13% 45 - 48 1% Magnesium 1.6 - .5 105% 18 - 18 0% 0.4 - 0.5 22% -- 39 - 37 5% 11 - 9.7 6% Sodium & Potassium 133 - 142 6% 100 - 116 7% 68 - 65 -- 18 - 26 38% Bicarbonate 114 - 104 9% 287 - 270 4% 173 - 135 25% 266 - 220 19% 321 - 330 3% 188 - 180 2% Chloride 42 - 41 29 - 33 4 - 3.1 5 - 4.9 20 - 22 10% 4 - 4.5 6% Sulfate 152 - 150 1% -- 48 - 47 2% 15 - 13 7% -- 1.8 - 2.5 33% .31 -.39 11% -- .70 - 71 0.4 - .25 23% 2% 7% 209 - 260 11% 4% 25% 4.9 - 3.9 23% 2% 9 - 14 22% Nutrients Nitrate (as nitrogen) .25 - .34 30% .53 - .42 12% .29 - .07 122% Trace Elements Fluoride 5.6 - 6.6 16% 2.4 - 2.1 7% 2 - 1.8 11% 1% All units in milligrams per liter (mg/l) except where noted. Historic samples collected by the U.S. Geological Survey28 47. Basic Data 31 The conclusions of this study are summarized in three different sections: Groundwater suitability for domestic use. Groundwater quality patterns unique to subareas of the basin. Study design and data evaluation. • • 2000 • Suitability of Groundwater for Domestic Use 1000 0 North South Watershed Figure 27 . TDS concentrations are higher in the northern (downgradient) portion than in the southern (upgradient) portion (Kruskal-Wallis test, p # 0.05). Factors related to this pattern may be a combination of natural and cultural impacts such as gypsum deposits, large-scale mining operations, and recharge of saline surface water from the Gila River10. The six sites are distributed as follows: confined basin-fill aquifer (one site), unconfined basin-fill aquifer (two sites), floodplain aquifer (one site), and hardrock (two sites). Analytical results were compared between the two sampling events. Of twelve constituents examined (mainly general mineral characteristics and major ions), only temperature levels significantly varied, being higher in the 1950s (Wilcoxon rank-sum test, p # 0.05). Temperature differences may be due to different equipment and purging requirements. Empirically examining the results provided in Table 4, constituent concentrations appear remarkably stable especially when considering potential differences in sampling and analytical techniques. The largest percentage differences typically involve very low concentrations where the absolute difference is small. CONCLUSIONS Groundwater quality of the LSP was assessed in 2000 by the ADEQ Groundwater Monitoring Unit. Sampling was conducted at 63 sites. Groundwater samples were collected for inorganic analyses at all sites, and for VOCs, radiochemistry, radon, and pesticide analyses at fewer sites. Eighteen (18) percent of sites had at least one constituent exceeding a health-based, Primary MCL standard. Primary MCL exceedances largely involved fluoride in the floodplain and confined basin-fill aquifers generally between the communities of Redington and Dudleyville. Both antimony exceedances were also in this area (Figure 13). Other Primary MCL exceedances included gross alpha at two sites located in granitic geology near Oracle and Redington Pass, nitrate at one site near Kearny, and arsenic at one site near Cascabel. If the new arsenic standard scheduled to be implemented in 2006 is considered, 11 additional sites near Mammoth and Cascabel (Figure 15) would exceed drinking water standards. log-Groundwater Depth (feet bls) TDS (mg/l) 3000 1 2 3 4 5 6 7 8 2.0 2.5 3.0 3.5 log-Temperature (Celsius) 4.0 Figure 28 . Temperatures generally increase with increasing groundwater depth bls (regression analysis, p # 0.05). Groundwater temperatures increase approximately 3 degrees Celsius with every 328 feet in depth 13. This relationship is best displayed using a biphasic method utilizing the log values of both factors. Conclusions 29 Similarly, 49 percent of sites had at least one constituent exceeding an aesthetics-based, Secondary MCL guideline. Their spatial distribution is largely constituent-specific: from along the San Pedro and Gila River corridors north of Redington because of potentially elevated fluoride concentrations as well as increased salinity levels. Groundwater Quality Patterns Unique to Aquifers • TDS exceedances (24 sites), sulfate exceedances (11 sites), and chloride exceedances (2 sites) occurred primarily along the San Pedro-Gila River corridor from the Aravaipa Creek confluence downstream to Kearny. • Fluoride exceedances (16 sites) occurred primarily along the San Pedro River corridor stretching from north of Redington to Winkelman. • Manganese exceedances (9 sites) and iron exceedances (4 sites) were randomly distributed throughout the basin. • pH exceedances (4 sites) occurred primarily in the Gailuro Mountains. Salinity related exceedances such as TDS, sulfate, and chloride appear to be related to recharge from the Gila and the San Pedro Rivers, dissolution of gypsum deposits, and recharge impacted by mine tailings and farming. Fluoride exceedances may be associated with calcium-depleted, alkaline conditions in the confined basin-fill aquifer that leaks groundwater into the floodplain aquifer28. Iron and manganese exceedances appear to be site specific with no large clusters of elevated concentrations of either constituent evident. Radon, the naturally occurring, intermediate breakdown product from the radioactive decay of uranium-238 to lead-206, had a mean concentration of 507 piC/l determined from 19 sites in the LSP. Recent radon data collected in three central Arizona basins had a similar mean of 590 piC/l20. As with the LSP data, this previous USGS study identified few relations between radon concentrations and various hydrologic factors. There are widely conflicting opinions on the risk assessment of radon in drinking water, with drinking water standards varying from 300 piC/l to 4,000 piC/l20. Based upon comparing the results of this regional study with water quality standards/guidelines, groundwater in large expanses of the LSP appears to be largely suitable for domestic purposes. Caution should be exercised when using groundwater Individual aquifers were examined for groundwater quality patterns. Hardrock Analyses of groundwater samples collected from sites in hardrock areas indicate that water quality typically is suitable for domestic or municipal uses. However, caution should be exercised in wells or springs located in granitic geology as elevated radiochemistry concentrations are often found in this rock type. The limited potential water production in hardrock areas usually makes these sites suitable only for domestic or stock use35. Of the 23 hardrock sample sites, only three had constituents exceeding a Primary MCL which consisted of gross alpha (two sites) and arsenic and fluoride (one site apiece). The 15 piC/l gross alpha standard was exceeded twice, with one site near Oracle having a concentration (69 piC/l) more than four times the MCL. Radiochemistry is typically elevated in areas of granite rocks, with the highest concentrations near mining areas 37. Mining may effect gross alpha concentrations through increased rock surface exposure. In contrast, four other sample sites were also located in or near granitic rock but did not have gross alpha concentrations over the Primary MCL. This indicates that not all groundwater in areas of granitic geology necessarily have elevated gross alpha concentrations. These patterns have occurred in previous basin studies in Arizona51 52 53. The site near Oracle also exceeded the fluoride Primary MCL standard. This well had a relatively high pH (7.93 su) and a calcium-depleted chemistry (sodiumbicarbonate) often reflective of groundwater with high fluoride concentrations. Groundwater in areas of granitic rock have previously been found to have fluoride concentrations at least twice that of other rock types 59. A site in the southern Gailuro Mountains exceeded the current arsenic Primary MCL standard. This spring had a low pH (6.97 su), a mixed-bicarbonate chemistry, and a low concentration of fluoride (0.30 mg/l), unusual for sites with elevated arsenic concentrations51 53. Conclusions 30 Unconfined Basin-Fill Aquifer Analyses of groundwater samples collected from sites in the unconfined basin-fill aquifer indicate that water quality is typically suitable for domestic or municipal uses. Furthermore, this aquifer appears to have the highest quality groundwater in the LSP as evidenced by the lowest constituent concentrations. Only two of the nine sites in the unconfined basinfill aquifer had water quality standard exceedances. A site near Mammoth had fluoride concentrations exceeding the Primary MCL; the arsenic concentration also exceeded the 2006 standard. Figure 29. The highest sulfate concentrations usually occur in wells withdrawing water from the floodplain aquifer, particularly those between the towns of Mammoth and Kearny. One such well that exceeds the 250 mg/l Secondary MCL is pictured above, which supplies water to ASARCO’s milling activities near the town of Hayden. The influence of surface water recharge from the Gila River to nearby shallow wells is evident in this photograph. Eight (8) of the 24 hardrock sites had constituent concentrations exceeding Secondary MCLs. These exceedances included manganese (five sites), pH (three sites), TDS (two sites), fluoride (one site). The chemistry of hardrock sites was typically a calcium or mixed-bicarbonate type, which is typical of recharge areas 46. The occasional site where sodium is the dominant cation are springs associated with fault zones, reversing the typical groundwater chemistry in hardrock areas 28. Many constituents (SC, TDS, sodium, potassium, sulfate, and fluoride) have lower concentrations in hardrock than in the floodplain aquifer; the opposite pattern occurs with bicarbonate. This indicates that although recharge occurs in both areas, mountain precipitation and runoff is more dilute than surface water flow from the San Pedro and Gila Rivers (Figure 29) (Kruskal-Wallis in conjunction with the Tukey test, p # 0.05). No significant differences were found among different rock types (Kruskal-Wallis in conjunction with the Tukey test, p # 0.05). A site near Kearny exceeded water quality standards for nitrate as well as TDS, sulfate, iron, and manganese. However, caution should be exercised in using data from this well. The analytical results do not match up with previous samples collected by the U.S. Geological Survey in 1980 and seem very out-of-character with other area samples. In particular, the nitrate (as nitrogen) concentration of 30 mg/l seems unusual. Both the ADHS laboratory and the well owner were contacted, but no errors could be found either with sample collection or analytical testing. Except for the above two sites, the unconfined basinfill aquifer sites had a calcium-bicarbonate chemistry, which is typical of recharge areas 46. However, bicarbonate concentrations are less than in hardrock, probably indicating less recharge is occurring here than in the mountains (Kruskal-Wallis in conjunction with the Tukey test, p # 0.05). Median concentrations of TDS, hardness, magnesium, sodium, chloride, sulfate, and fluoride were lower in the unconfined basin-fill aquifer than in hardrock, the floodplain aquifer, and the confined basin-fill aquifer, though these differences were not typically statistically-different. Conclusions 31 Floodplain Aquifer Analysis of groundwater samples collected from 27 floodplain aquifer sites indicate that while healthbased water quality standards were only exceeded at 4 sites (15 percent), aesthetics-based water quality standards were exceeded at 19 sites (70 percent). Groundwater from this most productive aquifer in the LSP generally can be used for domestic or municipal purposes, but often has aesthetic drawbacks associated with salinity concentrations. Primary MCL exceedances in the floodplain aquifer involved fluoride (three sites) and antimony (two sites). All four sites were located between Redington and Duddleyville. In addition, six sites exceeded the revised arsenic Primary MCL scheduled to be implemented in 2006. Secondary MCL exceedances included TDS (18 sites), fluoride (10 sites), sulfate (nine sites), and iron and manganese (3 sites apiece). The chemistry of floodplain aquifer sites varied widely. Interestingly, a previous groundwater quality study near Cascabel also revealed the characteristic clusters of Secondary MCL exceedances in the floodplain aquifer that were found in this study42. Many constituents (SC, TDS, sodium, potassium, sulfate, and fluoride) had higher concentrations in the floodplain aquifer than hardrock (Figure 30). Fluoride, sodium, and pH were lower in the floodplain aquifer than in the confined basin-fill aquifer; the opposite pattern occurred with bicarbonate. These patterns suggest that more dilute recharge occurs in the mountains than along the streams and that little recharge occurs in the confined basin-fill aquifer. Examining floodplain aquifer data by watershed, the most downgradient (Kearny) had significantly higher concentrations of SC, sodium, chloride, and potassium (Kruskal-Wallis in conjunction with the Tukey test, p # 0.05). These patterns may be explained by a combination of factors including impacts from surface water, natural factors, and human activities. Surface water quality was examined from the four major waterways influencing the LSP: Figure 30 . ADEQ employee Elizabeth Boettcher kicks up her heels in excitement upon discovering a commercial water outlet touted as dispensing “Mountain Water” as compared to the Town of Kearny tanks holding groundwater pumped from the floodplain aquifer in the background. Although precise analytical techniques and proper statistical applications are indispensable to hydrology reports, often a great deal of information about a region’s water resources can be discerned from examining the landscape and conversing with the residents. The entrepreneur operating this water stand shows it doesn’t take an ADEQ hydrology report to determine that “Mountain Water” tastes better than “Valley Water”, although perhaps not coincidently constituents with aesthetic-based standards such as TDS and sulfate were significantly higher in the floodplain aquifer than in hardrock areas (Kruskal-Wallis test in conjunction with the Tukey test, p # 0.05). Conclusions 32 concentrations in the San Pedro River near Cascabel (288 mg/l), and near Feldman (353 mg/l), as well as the Gila River above Coolidge Dam near Calva (308 mg/l) are all near the median 270 mg/l floodplain aquifer concentration. The shallow groundwater levels the floodplain aquifer may indicate that groundwater is open to soil CO2 46. Using mean TDS concentrations as a measurement, these waterways may be ranked in the following order from Figure 31. Coolidge Dam, constructed in 1928, impounds the Gila River upriver of the LSP freshest to most saline:7 56 and creates San Carlos Reservoir. Water is stored here for power generation and irrigation in Aravaipa Creek (261 mg/l), San Carlos Irrigation Project lands near the Coolidge/Casa Grande area. The USGS collects upper San Pedro River (437 water quality samples from the river near Calva upgradient of the reservoir. All ready highly mg/l), lower San Pedro River mineralized especially during low flows10, evaporation from the reservoir adds to the salinity concentrations32. This surface water recharges the floodplain aquifer in portions of the LSP. (670 mg/l), and the Gila River Water is released from San Carlos Reservoir into the Gila River according to regulations (1500 mg/l) (Appendix E). contained in the Gila Decree of 1936 for San Carlos Project lands10. TDS concentrations in the stretch of the Gila River • The San Pedro River (upgradient site near through the LSP are probably even higher after being Cascabel and a downgradient site near subjected to evaporation while impounded in the San Duddleyville). Carlos Reservoir (Figure 31). Recharge of this surface • Aravaipa Creek (site upgradient of the LSP). water should contribute both to the generally higher • The Gila River (site near Calva upgradient of both salinity concentrations found in the floodplain aquifer the LSP and Coolidge Dam). in general, and specifically to the most downgradient portion (Kearny) part of the aquifer influenced by the The San Pedro River sites appear to be closely related Gila River. to local precipitation levels. Another study has indicated that the groundwater quality of side canyon Recharge from surface water also appears to influence inflows have a major impact on the quality of the specific concentrations of major ions. Comparing floodplain aquifer42. This concurs with another floodplain aquifer data by watershed, the most study which indicates very little flow from south to downgradient (Kearny) watershed had significantly north along the axis of the basin 46. In contrast, Gila higher concentrations of sodium, chloride, and River flows are regulated by releases from San Carlos potassium (Kruskal-Wallis in conjunction with the Reservoir41. Surface water infiltrates readily from the Tukey test, p # 0.05). A similar pattern occurred with both rivers into the floodplain deposits and is the surface water quality with sodium, chloride, and source of most groundwater recharge to the potassium having much higher concentrations in the floodplain aquifer as indicated by rising groundwater Gila River than in the other three noted waterways. levels after periods of high streamflow41. As such, this aquifer is considered a chemically open Another major ion, sulfate, exhibits some unique hydrologic system46. patterns that may indicate a different contributing source. Sulfate was significantly higher in the Bicarbonate patterns support previous statements floodplain aquifer than hardrock although no spatial that considerable recharge occurs from surface flows patterns were found within the floodplain aquifer in the San Pedro and Gila Rivers. Bicarbonate (Kruskal-Wallis in conjunction with the Tukey test, p # Conclusions 33 0.05). Surface water quality data reveals the highest sulfate concentrations are found at the most downgradient site on the San Pedro River. A potential source of sulfate in this area is the large gypsum deposit that is mined (Figure 32) near the mouth of Aravaipa Creek41. Gypsum dissolves readily in contact with water and release sulfate and calcium ions into solution:17 CaSO4 C 2H2O = Ca 2+ + SO42- + 2H2O Another sulfate source may be the extensive mine tailings found along the San Pedro River near San Manuel. Previous studies indicated much of the groundwater pumped for mining is later recharged to the floodplain aquifer28. Groundwater quality impacts from mine tailings may include elevated concentrations of both sulfate and radiochemical constituents as well as low, acidic pH values which can leach heavy metals 33 46. Leachate from tailings ponds is considered the source of elevated sulfate concentrations in the Bisbee-Naco area36. Salinity concentrations in the floodplain aquifer could also be impacted by land uses in the area. Though not extensive, irrigated farming is common along the San Pedro River and Gila River floodplains. Seepage from irrigated fields was estimated to be 3,000 af/yr28. With groundwater depths typically less than 50 feet bls, it is probable that this shallow aquifer may receive impacts by groundwater recharge from irrigation applications. Deterioration of groundwater quality associated with irrigation development has also been commonly observed worldwide31, as well as in other agricultural areas of Arizona48 53. Constituents such as TDS become concentrated by evaporation during the irrigation and are subsequently recharged to the aquifer18. Best management practices can reduce concentrations of nitrate and pesticides in this recharge water but not salt loadings on the groundwater14. Other human activities such as domestic and municipal wastewater treatment systems do not appear to have an extensive impact on th floodplain aquifer at this time, a conclusion also reached in previous reports 42. Nitrate concentrations were generally low. When elevated over 3 mg/l which may indicate impacts from human activities 38, these sites were generally located in hardrock or the unconfined basin-fill aquifer. In the floodplain aquifer, fluoride concentrations were significantly higher in the Mammoth watershed than in the other three (one upgradient, two downgradient) watersheds. This may be because this portion of the floodplain aquifer largely overlies the confined basinfill aquifer. Through both natural fault zones and inadequately sealed wells, groundwater high in fluoride concentrations migrates upwards into the floodplain aquifer28 45. This relationship could potentially reverse in the future if the continued discharge of deep artesian aquifer water reduces the head below water table levels 41. Sulfate and chloride variability in the floodplain aquifer could be impacted by upward leakage through gypsum or halite deposits, materials which are less common in the stream alluvium46. Confined Basin-Fill Aquifer The four sites from which samples were collected from this artesian aquifer represent three areas of confined conditions previously detailed46. The confined basinfill aquifer averaging around 300 feet in depth near Redington is represented by LSP-18/19 and is significant for dilute groundwater which indicates an absence of gypsum deposits found at the other artesian sites 46. This is the beginning and the shallowest part of the artesian aquifer. The deeper Mammoth-area artesian wells are represented by LSP-11. Artesian conditions near Feldman are represented by LSP-50/51. The fourth site, LSP-47 appears to be transitional, having a depth similar to Redington-area wells but a chemical composition reflective of Mammoth-area wells. Robertson46 notes that recharge for the artesian aquifer occurs as precipitation and runoff in the Galiuro Mountains and moves toward the center of the basin, eventually discharging along the line of dense phreatophytes near the San Pedro River with very little moving downgradient. Analysis of groundwater samples collected from four sites in the confined basin-fill aquifer indicate that health-based and aesthics-based water quality standards were exceeded at 3 sites (75 percent). Thus, groundwater from this artesian aquifer, especially away from shallow depths near Redington generally shouldn’t be relied upon for domestic or municipal purposes without treatment for elevated fluoride concentrations. Irrigation use is also not recommended because of sodium hazards since the sites are sodiumdominated with an almost complete lack of calcium ions. Basic Data 34 Water quality standard exceedances in the confined basin-fill aquifer involved fluoride (three sites), TDS (two sites), and pH, chloride, and sulfate (one site apiece). Two sites had arsenic concentrations exceeding the new 2006 arsenic standard. Another artesian site sampled (LSP-77/78) located just outside the LSP in the Donnelly Wash Basin had a pH exceedance as well as arsenic concentrations exceeding the 2006 standards. The elevated fluoride concentrations as well prevailing sodium-bicarbonate chemistry of the confined basin-fill aquifer have been noted in previous studies 16. The chemistry of confined basin-fill aquifer sites were of a sodium-bicarbonate/mixed type and represent a chemically closed hydrologic system in which the aqueous chemistry is determined solely by the reactions of the initial recharge water with the various minerals as it moves downgradient 46. The high sodium concentrations are likely the result of ion exchange of calcium for sodium 46. Ion exchange is a significant reaction in basins having high TDS and sulfate concentrations caused by the dissolution of gypsum. The additional sulfate concentrations caused by the dissolution of gypsum are made up by the exchange of calcium for sodium. In other areas of Arizona where groundwater is more dilute, high sodium concentrations are usually caused by silicate hydrolysis 46. Chemically closed hydrologic systems favor high pH values and the removal of calcium, factors that may produce large fluoride concentrations46. Calcium is an important control of higher fluoride concentrations (> 5 mg/l) through precipitation of the mineral fluorite44. In a chemically closed hydrologic system, calcium is removed from solution by precipitation of calcium carbonate and formation of smectite clays, which may result in large fluoride concentrations45. High concentrations of dissolved fluoride may occur if the groundwater is depleted in calcium and a source of fluoride ions is available for dissolution45. Results from this study support this finding. The three of the four sites with fluoride concentrations greater than 5 mg/l had corresponding depleted calcium concentrations. Constituents such as pH, fluoride, and sodium were higher in the confined basin-fill aquifer than in the other three LSP aquifers. Sulfate and temperature were higher in the confined basin-fill aquifer than in hardrock. In contrast, bicarbonate was lower than in the floodplain aquifer and hardrock (Kruskal-Wallis in conjunction with the Tukey test, p # 0.05). These patterns indicate that groundwater in the confined basin-fill aquifer is probably highly evolved and receives little recent recharge. Overview of Basin Interestingly, few significant relationships were found between groundwater depth and constituent concentrations. Although previous studies had found TDS concentrations increasing with depth in the floodplain aquifer46, this study did not reveal a significant relationship between these two indices (regression analysis, p # 0.05). In other ADEQ studies in Arizona basins, many significant relationships were typically present 50 51 52 53. The LSP is similar to the Virgin River basin in extreme northwestern part of the state on the Arizona Strip 49. In this basin, there were significant relationships between groundwater depth and constituent concentrations; however, few relationships existed within individual aquifers. Thus in the Virgin River basin, as well as in the LSP basin, it was thought that groundwater depth relationships were the result of differences in constituent concentrations and groundwater depth between aquifers than any actual relationship within aquifers. Study Design and Data Evaluation Methods of Investigation - The 63 groundwater sample sites were selected using a stratified, random sampling strategy. The sample collection methods for this study conformed to the Quality Assurance Project Plan4 and the Field Manual for Water Quality Sampling 11. Data Evaluation - Quality assurance procedures were followed and quality control samples were collected to ensure the validity of the groundwater quality data. Analysis of equipment blank samples indicated systematic contamination by SC-lab and turbidity; however, the extent of the contamination by these parameters was not considered significant. Analysis of duplicate and split samples revealed excellent correlations; those constituents with large percent differences typically had only minor absolute differences. Data validation was also examined in six QA/QC correlations that validated the acceptability of the groundwater quality data for further analysis. Overall, the effects of sampling procedures and laboratory methods on the samples were not considered significant. Conclusions 35 Data analysis for this study was conducted using Systat software 58. The non-normality of both the nontransformed data and the log-transformed data was determined by using the Kolmogorov-Smirnov onesample test with the Lilliefors option 15. Spatial variations in constituent concentrations were investigated using the non-parametric Kruskal-Wallis test. Constituent concentration changes over time were investigated using the non-parametric Wilcoxon rank-sum test29. Vertical (groundwater depth) variations were examined using three regression models. Correlations among constituent concentrations were analyzed using the Pearson Correlation Coefficient test. Determining the most important major ion influences on TDS concentrations was conducted using multiple regression 29. private well meets all water quality standards for domestic use, tests should be conducted on a range of constituents. < The following recommendations are provided for public water systems within the LSP. < RECOMMENDATIONS Recommendations for domestic well owners, public water supply systems, and future groundwater quality studies are provided in this section. These recommendations are based on interpretations of the analytical results from groundwater samples collected for this study. < ADEQ encourages well owners concerned about their water supply to periodically collect samples with the assistance of certified laboratories for analysis of the full range of groundwater quality constituents. The ADHS, Environmental Laboratory Licensure and Certification Section at (602) 255-3454 provides a list of certified labs. Well owners interested in less expensive and more targeted testing of their water source should include the following constituents in their sampling and analysis: fluoride and arsenic particularly at sites located along the San Pedro and Gila River corridor between San Manuel and Kearny and in wells drawing groundwater from the confined basin-fill aquifer, and gross alpha in areas of granite rock, especially near Oracle. Primary MCL exceedances may occur in other areas of the LSP; however, based upon the results of this regional groundwater quality report, their occurrence should not be widespread on a basinwide basis. Again, it should be stressed that for full assurance that groundwater pumped by a Groundwater quality data collected during this study should assist in the site selection process of new public supply wells. Some sample sites exceeded health-based, water quality standards and caution should be used in developing new public water supplies in these aquifers and areas . The following recommendations are provided for future groundwater quality studies within the LSP. < The following recommendations are provided for domestic well owners in the LSP. < ADEQ encourages well owners to inspect and, if necessary, repair faulty surface seals, degraded casing, or other factors that may affect well integrity. Septic systems should also be inspected periodically to assure safety and compliance with ADEQ’s Engineering Bulletin #12 1. Resampling of the ADEQ index wells appears to be unnecessary at intervals of less than approximately ten years. Although a comprehensive time-trend analysis was not able to be conducted, limited historical data in conjunction with other studies in Arizona suggests that most of the constituents are largely controlled by natural factors and are not prone to vary significantly over time in the near term. REFERENCES 1 American Smelting and Refining Company Website, 2001, www.asarcocu.com/ray/ray2.htm 2 Arizona Department of Environmental Quality, 1989. Engineering Bulletin No. 12: Minimum Requirements for the Design and Installation of Septic Tank Systems and Alternative on-Site Disposal Systems. ADEQ: Phoenix, Arizona. 3 Arizona Department of Commerce Website, 2001,www.commerce.state.az.us/publications/comm unity_profile_index.htm 4 Arizona Department of Environmental Quality, 1991. Quality Assurance Project Plan. ADEQ Water Quality Standards Unit: Phoenix, Arizona. Recommendations 36 5 Arizona Department of Environmental Quality, 1998. Arizona Laws Relating to Environmental Quality. West Group: St. Paul, Minnesota. 6 Arizona Department of Environmental Quality, 1998b. Drinking Water Section Fact Sheet #3. ADEQ Fact Sheet 98-16, Phoenix, Arizona. 7 Arizona Department of Environmental Quality, 2001. Surface Water Quality Database. ADEQ Surface Water Quality Unit: Phoenix, Arizona. 8 Arizona Department of State Lands, 1997. Arizona Land Resource Information Systems. ADSL: Phoenix, Arizona. 9 Arizona Department of Water Resources, 1990. Preliminary Hydrographic Survey Report for the San Pedro River Watershed: Volume 1 - General Assessment. ADWR: Phoenix, Arizona. 10 11 12 13 14 15 16 17 Coes, A. L., D.J. Gellenbeck, and D.C. Towne, 1999. Ground-Water Quality in the Sierra Vista Subbasin, Arizona, 1996-97. U.S. Geological Survey Water-Resources Investigations Report 99-4056: Tucson, Arizona. 18 Coes, A.L., D.J. Gellenbeck, D.C. Towne, and M.C. Freark, 2000. Ground-Water Quality in the Upper Santa Cruz Basin, Arizona, 1998. U.S. Geological Survey Water-Resources Investigations Report 004117: Tucson, Arizona. 19 Cohen, P., W.A. Alley, and W.G. Wilber, 1988. National Water-Quality Assessment: Future Directions of the U.S. Geological Survey. Water Resources Bulletin 24: 1047-1051. 20 Cordy, G.E., H.W. Sanger, and D.J. Gellenbeck, 2000. Radon in Ground Water in Central and Southern Arizona: A Cause for Concern? Paper Presented at ASH 2000, Annual Symposium of the Arizona Hydrologic Society, Phoenix, Arizona, September 20th to 23rd. 21 Crockett, Janet K., 1995. Idaho Statewide Groundwater Quality Monitoring Program Summary of Results, 1991 Through 1993. Idaho Department of Water Resources: Boise, Idaho. 22 Del Mar Laboratory, 2000. Personal communication from Del Mar laboratory staff member. 23 Ducote, Richard, 2002. San Manuel’s Mining Hopes Fade, BHP Copper to Trim More Jobs, Allow Underground Mine to Flood. Arizona Daily Star, January 17: Tucson, Arizona. 24 Duncan, J.T. and J.E. Spencer, 1993. “Uranium and Radon in Southeastern Arizona” in Radon in Arizona, Spencer, Jon. E. ed, Geological Survey Bulletin 1999, p. 40-42. 25 Freethey, G.W. and T.W. Anderson, 1986. Predevelopment Hydrologic Conditions in the Alluvial Basins of Arizona and Adjacent Parts of California and New Mexico. U.S. Geological Survey Hydrologic Investigations Atlas HJA-664. 26 Graf, Charles, 1990. An Overview of Groundwater Contamination in Arizona: Problems and Principals. ADEQ Seminar: Phoenix, Arizona. Arizona Department of Water Resources, 1994. Arizona Water Resources Assessment. ADWR: Phoenix, Arizona. Arizona Water Resources Research Center, 1995. Field Manual for Water-Quality Sampling. University of Arizona College of Agriculture: Tucson, Arizona. Bedient, P.B., H.S. Rifai., and C.J. Newell, 1994. Ground Water Contamination: Transport and Remediation. Prentice Hall, Inc: Englewood Cliffs, New Jersey. Bitton, Gabriel and C.P. Gerba, 1994. Groundwater Pollution Microbiology. Krieger Publishing Company: Malabar, Florida. Bouwer, Herman, 1997. Arizona’s Long-Term Water Outlook: From NIMTO to AMTO-Part II. Arizona Hydrologic Newsletter, Vol. 14, Issue 5. Brown, S.L., W.K. Yu, and B.E. Munson, 1996. The Impact of Agricultural Runoff on the Pesticide Contamination of a River System - A Case Study on the Middle Gila River. ADEQ Open File Report 96-1: Phoenix, Arizona. Bryan, Kirk, G.E.P. Smith, and G.A.Waring, 1934. Ground-Water Supplies and Irrigation in San Pedro Valley, Arizona. U.S. Geological Survey Open File Report, 167 p. References 37 27 Heath, Ralph C., 1989. Basic Ground-Water Hydrology. U.S. Geological Survey WaterSupply Paper 2220. 28 Heindl, L.A., 1952. Groundwater in the Gila River Basin and Adjacent Areas, Arizona–A Summary, Halpenny, L.C., ed. USGS Open File Report: Tucson, Arizona. 29 30 31 Helsel, D. R., and R.M. Hirsch, 1997. Statistical Methods in Water Resources. Elsevier Publishing: New York, New York. Hem, John D., 1947. “Section on Quality of the Water” in Geology and Ground-Water Resources of the Willcox Basin, Cochise and Graham Counties, Arizona, Jones, R.S. and Cushman, R.L. eds. U.S. Geological Survey in conjunction with the Arizona State Land Department. Hem, John D., 1970. Study and Interpretation of the Chemical Characteristics of Natural Water. USGS Water-Supply Paper 1473: Washington, D.C. 32 Hem, John D., 1985. Study and Interpretation of the Chemical Characteristics of Natural Water, Third Edition. USGS Water-Supply Paper 2254: Washington, D.C. 33 Henderson, Timothy R., 1984. Groundwater Strategies for State Action. The Environmental Law Institute: Washington, D.C. 34 Hood, Wayne K, III., 1991. A Plan To Establish Ambient Groundwater Quality Monitoring Networks in Arizona. ADEQ: Phoenix, Arizona. 35 Jones, S.C., 1980. Maps Showing Ground-Water Conditions in the Lower San Pedro Basin Area, Pinal, Cochise, Pima, and Graham Counties, Arizona–1979. USGS Water-Resources Investigations Open-File Report 80-954. 36 37 Littin, G.R., 1987. Groundwater Resources of the Bisbee-Naco Area, Cochise County, Arizona. USGS Water-Resources Investigations Reprt 874103: Denver, Colorado. 38 Madison, R.J. and J.O. Brunett, 1984. “Overview of the Occurrence of Nitrate in Ground Water of the United States,” in National Water Summary 1984 Water Quality Issues. 39 Muffley, Bernard W., 1938. The History of the Lower San Pedro Valley in Arizona. Masters Thesis, University of Arizona: Tucson, Arizona. 40 Nature Conservancy, Arizona Chapter Website, 2001, www.tncarizona.org/ 41 Page, Harry G., 1963. Water Regimen of the Inner Valley of the San Pedro River near Mammoth, Arizona (A Pilot Study). USGS Water-Supply Paper 1699-1: Washington, D.C. 42 Riverside Technology, Inc, 1992. An Assessment of Well and Stream Water Quality along the San Pedro River near the town of Cascabel, Arizona. Riverside Technology: Fort Collins, Colorado.. 43 Roberts, Isaac, 2000. Personal communication from ADHS laboratory staff member. 44 Robertson, F. N., 1986. "Occurrence and Solubility Controls of Trace Elements in Groundwater in Alluvial Basins of Arizona" Anderson, T. W., and Johnson, A. I., eds., Regional Aquifer Systems of the United States, Southwest Alluvial Basins of Arizona. American Water Resources Association Monograph Series No. 7, p. 69-80. 45 Robertson, F. N. and W.B. Garrett, 1988. Distribution of Fluoride in Ground Water in the Alluvial Basins of Arizona and Adjacent Parts of California, Nevada, and New Mexico. U.S. Geological Survey Hydrologic Investigations Atlas HA-665. 46 Robertson, F. N., 1991. Geochemistry of Ground Water in Alluvial Basins of Arizona and Adjacent Parts of Nevada, New Mexico, and California. U.S. Geological Survey Professional Paper 1406-C. 47 Roeske, R.H. and W.L. Werrell, 1973. Hydrologic Conditions in the San Pedro River Valley, Arizona, 1971. Arizona Water Commission Bulletin #4. Lowry, J.D. and S.B. Lowry,, 1988. “Radionuclides in Drinking Waters,” in American Water Works Association Journal. July 1988. References 38 48 Towne, D.C. and W.K. Yu, 1998. Ambient Groundwater Quality of the Yuma Basin: A 1995 Baseline Study. ADEQ Open File Report 98-07: Phoenix, Arizona. 49 Towne, D.C. 1999. Ambient Groundwater Quality of the Virgin River Basin: A 1997 Baseline Study. ADEQ Open File Report 99-4: Phoenix, Arizona. 50 Towne, D.C. 1999. Ambient Groundwater Quality of the Douglas Basin: A 1995-1996 Baseline Study. ADEQ Open File Report 99-11: Phoenix, Arizona. 51 Towne, D.C. and M.C. Freark, 2000. Ambient Groundwater Quality of the Prescott AMA: A 1997-98 Baseline Study. ADEQ Open File Report 00-01: Phoenix, Arizona. 52 Towne, D. C. and M.C. Freark, 2001. Ambient Groundwater Quality of the Sacramento Valley Basin: A 1999 Baseline Study. ADEQ Open File Report 01-04, Phoenix, Arizona. 53 Towne, D. C. and M.C. Freark, 2001. Ambient Groundwater Quality of the Willcox Basin: A 1999 Baseline Study. ADEQ Open File Report 01-09, Phoenix, Arizona. 54 U.S. Environmental Protection Agency, 1993. The Safe Drinking Water Act - A Pocket Guide to the Requirements for the Operators of Small Water Systems. USEPA Region 9: San Francisco, CA. 55 U.S. Geological Survey, 2001. Water Resources Data Arizona Water Year 2000. USGS WaterData Report AZ-00-1: Springfield, VA. 56 U.S. Salinity Laboratory, 1954. Diagnosis and Improvement of Saline and Alkali Soils. USDA Agriculture Handbook No. 60: Washington, D.C. 57 Water Quality Association, 2002, www.wqa.org/ 58 Wilkinson, L. and M.A. Hill, 1994. Using Systat. Systat, Inc: Evanston, IL. 59 White, D.E., J.D. Hem, and G.A. Waring, 1963. “Chemical Composition of Sub-Surface Waters,” in Data of Geochemistry, 6 th Edition. USGS Professional Paper 440-F: Washington, D.C. 60 Childs, Craig, 2001. The Secret Knowledge of Water: Discovering the Essence of the American Desert. Little, Brown & Company. References 39 Appendix A. Data for Sample Sites, Lower San Pedro Basin, 1999-2000 Sample # Cadastral Latitude Longitude ADWR # ADEQ # Samples Collected Well Depth Water Depth Watershed Aquifer 1 st Field Trip, November 30-December 2, 1999 - Towne & Boettcher (Equipment Blank, LSP-13) LSP-01 (D-13-19)23dba 32°17'16.210" 110°22'22.452" 513520 58167 Inorganic 98' 30' Redington Floodplain LSP-02 (D-13-19)23dab 32°17'21.662" 110°22'08.235" 629462 58168 Inorganic VOC Radon 122' 60' Redington Floodplain LSP-03 (D-13-20)31bcc 32°15'41.795" 110°20'50.617" 645667 58169 Inorganic 90' 29.7' Redington Floodplain LSP-04 (D-08-17)31acd 32°41'43.911" 110°38'27.999" 532355 58170 Inorganic VOC 501' 295' Mammoth UBF LSP-05/06 (D-12-18)13bda 32°23'24.428" 110°27'20.607" 608218 58171 Inorganic VOC Radon 150' 80' Mammoth Floodplain LSP-07 (D-12-18)03aaa 32°25'37.421" 110°29'06.186" 608217 58172 Inorganic 127' 42' Mammoth Floodplain LSP-08/09 (D-14-20)08bbd 32°14'12.964" 110°19'32.787" 608065 58173 Inorganic VOC Radon 100' 42' Redington Floodplain LSP-10 (D-09-17)04aaa 32°41'05.891" 110°36'20.791" 607862 58174 Inorganic VOC Radon 150' 80' Mammoth Floodplain LSP-11 (D-08-17)32add 32°41'38.803" 110°37'17.996" 624632 58175 Inorganic VOC Radon 1485' Artesian Mammoth CBF LSP-12 (D-10-16)28bdb 32°32'17.997" 110°43'01.918" 806798 58176 Inorganic Radiochem 97' 25' Mammoth Hardrock 2 nd Field Trip, December 15-17, 1999 - Towne & Lucci (Equipment Blank, LSP-23) LSP-14 (D-06-16)08cbb 32°55'26.917" 110°44'26.234" 612036 58218 Inorganic 120' 26' Winkelman Floodplain LSP-15/16 (D-07-16)22ddd 32°48'29.594" 110°41'45.509" 618760 58219 Inorganic VOC Radon 140' 43' Winkelman Floodplain LSP-17 (D-06-16)06dbc 32°56'14.895" 110°44'55.955" 612039 58220 Inorganic 90' 23.7' Winkelman Floodplain LSP-18/19 (D-11-18)03bbc 32°30'38.356" 110°30'08.518" 600350 58221 Inorganic VOC Radon 195' Artesian Mammoth CBF LSP-20 (D-08-17)19ddd 32°43'05.789" 110°38'22.355" 643305 58222 Inorganic VOC Radon 130' 10' Mammoth Floodplain LSP-21 (D-04-14)08ddc 33°05'40.824" 110°55'44.306" 540818 58223 Inorganic VOC 320' 200' Kearny UBF LSP-22 (D-04-14)35bad 33°02'32.863" 110°53'09.233" 607497 27719 Inorganic Radon 500' 22' Kearny UBF 80' Redington UBF 3 rd Field Trip, January 12-13, 2000 - Towne & Flora LSP-24* (D-13-18)11aad 32°19'24.679" 110°28'05.914" 613547 36630 Inorganic Radiochem 230' * = LSP-25 and LSP-26 were splits for the City of Tucson that were never analyzed. Basic Data 40 Appendix A. Data on Sample Sites, Lower San Pedro Basin, 1999-2000--Continued Sample # Cadastral Latitude Longitude ADWR # ADEQ # Samples Collected Well Depth Water Depth Watershed Aquifer LSP-26* (D-13-18)06adb 32°20'10.370" 110°32'19.596" 613550 58789 Inorganic VOC Radiochem 300' 150' Redington Hardrock LSP-28 (D-05-15)24baa 32°59'24.905" 110°45'55.803" 616618 28881 Inorganic VOC 120' 23' Kearny Floodplain LSP-29/30 (D-05-15)24baa 32°59'23.856" 110°45'56.091" 616694 28882 Inorganic Radon 412' 22' Kearny Floodplain 4 th Field Trip, February 2-4, 2000 - Towne & Boettcher LSP-31 (D-12-20)21cca 32°22'16.985" 110°18'58.924" 648764 58271 Inorganic VOC Radiochem 147' 30' Redington Hardrock LSP-32 (D-13-19)04bad 32°20'11.779" 110°24'34.277" 545407 58272 Inorganic 100' 55' Redington Floodplain LSP-33 (D-13-20)21dbb 32°17'16.200" 110°18'27.225" none 58273 Inorganic spring spring Redington Hardrock LSP-34/35 (D-12-20)11dad 32°24'08.554" 110°16'09.585" 648765 58274 Inorganic VOC Radiochem 140' 50' Redington Hardrock LSP-36 (D-11-20)26cab 32°26'49.398" 110°16'42.644" none 58275 Inorganic spring spring Redington Hardrock LSP-37/38 (D-13-21)06abd 32°20'09.108" 110°14'18.338" none 58276 Inorganic VOC Radiochem spring spring Redington Hardrock LSP-39 (D-11-19)15aaa 32°29'06.282" 110°23'02.569" none 58277 Inorganic Radiochem spring spring Mammoth UBF LSP-40 (D-06-16)33bbc 32°52'22.482" 110°42'45.447" 617384 55093 Inorganic Radon Pesticide 101' 13' Winkelman Floodplain LSP-41 (D-06-16)29aba 32°53'18.790" 110°43'40.869" 617385 58278 Inorganic Pesticide 100' 22' Winkelman Floodplain 5 th Field Trip, February 24-25, 2000 - Towne & Freark LSP-42 (D-08-18)14dad 32°44'02.189" 110°29'59.461" none 58449 Inorganic Radiochem spring spring Mammoth Hardrock LSP-43 (D-08-18)23aba 34°43'44.453" 110°28'13.814" none 58786 Inorganic spring spring Mammoth Hardrock LSP-44 (D-05-15)23bda 32°59'07.361" 110°47'17.739" 617374 28877 Inorganic VOC Radion 80' 21' Kearny Floodplain LSP-45/46 (D-05-15)23bda 32°59'08.325" 110°46'59.328" 617367 58450 Inorganic VOC Radion 100' 29' Kearny Floodplain * = LSP-25 and LSP-26 were splits for the City of Tucson that were never analyzed. Basic Data 41 Appendix A. Data on Sample Sites, Lower San Pedro Basin, 1999-2000--Continued Sample # Cadastral Latitude Longitude ADWR # ADEQ # Samples Collected Well Depth Water Depth Watershed Aquifer 6 th Field Trip, March 29-31, 2000 - Towne & Boettcher LSP-47 (D-10-18)08cbb 32°34'43.288" 110°31'24.910" 561754 58542 Inorganic VOC Radion 400' artesian Mammoth CAF LSP-48 (D-14-20)27ccc 32°34'43.705" 110°31'24.585" none 58546 Inorganic VOC Radion 90' 16' Redington Floodplain LSP-49 (D-15-20)03ccd 32°09'13.435" 110°17'31.815" none 58590 Inorganic 90' 16' Redington Floodplain LSP-50/51 (D-06-16)33bbb 32°11'59.845" 110°14'35.475" 526520 58591 Inorganic Radon 1250' artesian Winkelman CBF LSP-52 (D-06-16) 32°52'27.525" 110°43'22.425" none 58592 Inorganic spring spring Winkelman Floodplain LSP-53 (D-07-16)18bcd 32°49'28.145" 110°45'16.675" none 31851 Inorganic Radiochem spring spring Winkelman Hardrock LSP-54 (D-14-20)12cac 32°13'39.665" 110°15'25.255" 651298 38003 Inorganic Radiochem 14‘ 5‘ Redington Hardrock LSP-55 (D-15-21)07bcd 32°08'43.245" 110°14'23.285" none 58593 Inorganic Radiochem spring spring Redington Hardrock LSP-56/57 (D-09-16)31bad 32°36'50.515" 110°44'58.225" 575608 33951 Inorganic Radiochem 300' 70' Mammoth Hardrock LSP-58 (D-10-18)08abc 32°34'48.125" 110°31'25.825" 542755 58594 Inorganic VOC 80' 30' Mammoth Floodplain LSP-59 (D-15-19)01add 32°09'31.035" 110°20'50.900" none 38952 Inorganic spring spring Redington Hardrock 7 th Field Trip, April 19-21, 2000 - Towne & Boettcher LSP-60 (D-07-17)09bcb 32°50'32.207" 110°37'12.000" 806142 58652 Inorganic 65' 12' Winkelman Floodplain LSP-61 (D-11-16)10dda 32°29'32.877" 110°41'50.930" none 58653 Inorganic spring spring Mammoth Hardrock LSP-62 (D-11-17)19ddd 32°27'22.477" 110°38'23.126" none 58654 Inorganic Radiochem spring spring Mammoth Hardrock LSP-63/64 (D-11-17)24cac 34°27'42.985" 110°33'43.919" 624301 58655 Inorganic VOC Radon -- 32' Mammoth UBF LSP-65 (D-07-16)11adc 32°50'21.925" 110°40'31.823" 538345 58656 Inorganic 108' 12' Mammoth Floodplain LSP-66 (D-07-16)10cdd 32°49'59.352" 110°41'57.569" 636185 58657 Inorganic 157' 12' Mammoth Floodplain LSP-67 (D-07-16)22add 32°48'41.820" 110°41'20.280" none 58658 Inorganic 100' 25' Mammoth Floodplain Basic Data 42 Appendix A. Data on Sample Sites, Lower San Pedro Basin, 1999-2000--Continued Sample # Cadastral Latitude Longitude ADWR # ADEQ # Samples Collected Well Depth Water Depth Watershed Aquifer 8 th Field Trip, June 28-30, 2000 - Towne & Boettcher (Equipment Blank, LSP-68) LSP-69/70 (D-01-13)14dbd 32°34'43.705" 110°31'24.585" 526188 58806 Inorganic VOCs Radiochem 545' 450' Kearney Hardrock LSP-71 (D-15-18)11bbd 32°09'13.435" 110°17'31.815" 604357 58807 Inorganic Radon 300' 36' Redington UBF LSP-72 (D-15-18)01dbc 32°11'59.845" 110°14'35.475" 645893 58808 Inorganic VOCs 40' 35' Redington UBF LSP-73 (D-15-19)06ada 32°52'27.525" 110°43'22.425" none 58819 Inorganic Radiochem spring spring Redington Hardrock LSP-74 (D-10-17)27dbd 32°31'57.632" 110°35'24.659" 629393 58820 Inorganic 360' 320' Mammoth UBF LSP-75 (D-01-14)27caa 33°18'48.703" 110°55'31.160" none 58818 Inorganic Radiochem spring spring Kearney Hardrock 9 th Field Trip, July 10-12, 2000 - Towne & Boettcher (Equipment Blank, LSP-84) LSP-76 (D-03-13)08ba 33°11'27.34" 111°02'40.12" 633774 55034 Inorganic VOCs Radiochem 30' 8' Kearney Hardrock LSP-77/78** (D-03-12)24bcb 33°09'25.604" 111°04'47.346" none 58801 Inorganic Radon deep' artesian Kearney CBF LSP-80 (D-10-20)07bdd 32°34'48.125" 110°31'25.825" none 58802 Inorganic Radiochem spring spring Redington Hardrock LSP-81 (D-09-20)33cbb 32°36'23.559" 110°18'47.704" none 58803 Inorganic spring spring Redington Hardrock LSP-82 (D-05-14)03adb 32°50'32.207" 110°37'12.000" none 58804 Inorganic Radiochem spring spring Kearney Hardrock LSP-83 (D-05-14)02bba 32°29'32.877" 110°41'50.930" 615376 58805 Inorganic VOCs Radon 45' 37' Kearney Floodplain ** Reported for information purposes only as the sample site was in the Donnelly Wash groundwater basin. Basic Data 43 Appendix B. Groundwater Quality Data, Lower San Pedro Basin, 1999-2000 Sample # ADEQ # MCL Exceedances Temp (o C) pH-field (su) SC-lab (FS/cm) TDS (mg/l) Hardness (mg/l) Total Alk (mg/l) Turbidity (ntu) LSP-01 58167 TDS, Fe 19.35 7.43 1100 720 340 250 1.3 LSP-02 58168 TDS 22.26 7.34 1000 690 310 210 2.5 LSP-03 58169 TDS, Fe, Mn, As* 19.99 7.41 1100 710 310 260 8.1 LSP-04 58170 F, As* 29.70 8.01 590 390 58 110 0.45 LSP-05/06 58171 -- 19.77 7.58 725 375 220 220 0.05 LSP-07 58172 TDS 18.92 7.27 840 550 300 260 0.33 LSP-08/09 58173 TDS 21.34 7.45 905 600 240 230 1.0 LSP-10 58174 TDS, SO4, F, As* 25.21 7.55 1100 740 260 210 6.6 LSP-11 58175 F, As* 38.60 8.47 700 450 32 92 0.15 LSP-12 58176 -- -- 8.33 400 220 200 180 0.08 LSP-14 58218 TDS, SO4, F 20.80 7.31 1100 700 310 220 0.60 LSP-15/16 58219 TDS, SO4, F 21.16 7.15 1100 775 360 235 1.6 LSP-17 58220 TDS, F 19.37 7.44 930 600 280 210 1.3 LSP-18/19 58221 -- 22.55 7.91 320 200 57 140 0.06 LSP-20 58222 F, As* 26.50 8.36 510 310 53 100 2.2 LSP-21 58223 -- 25.53 7.19 670 400 290 190 0.12 LSP-22 27719 TDS,SO4,NO3,Fe,Mn 24.45 6.78 4300 2800 1200 220 16 LSP-24 36630 -- 21.21 8.01 430 260 200 180 0.30 LSP-26 58789 Gross Alpha -- 7.67 690 440 270 260 1.1 LSP-28 28881 TDS, Mn 19.09 8.05 1300 760 280 190 0.09 LSP-29/30 28882 TDS 19.99 8.08 1300 740 260 190 0.32 LSP-31 58271 -- 20.46 7.25 723 460 310 300 0.22 LSP-32 58272 -- 22.28 7.48 720 450 140 260 2.2 LSP-33 58273 TDS, As 11.52 6.97 960 550 390 440 9.0 LSP-34/35 58274 -- 20.81 6.91 505 335 240 225 0.90 LSP-36 58275 -- 13.75 7.07 460 310 210 200 0.75 LSP-37/38 58276 pH, As* 34.37 9.24 290 195 9.2 130 0.04 LSP-39 58277 -- 11.77 7.45 560 310 250 240 0.12 LSP-40 55093 -- 18.74 7.33 660 470 270 200 0.18 bold = constituent level exceeds Primary or Secondary MCL italics = constituent exceeded holding time * = concentration exceeds the revised arsenic SDW Primary MCL of 0.01 mg/l which becomes effective in 2006 Basic Data 44 Appendix B. Groundwater Quality Data, Lower San Pedro Basin, 1999-2000--Continued Sample # Calcium (mg/l) Magnesium (mg/l) Sodium (mg/l) SAR (value) Potassium (mg/l) Bicarbonate (mg/l) Carbonate (mg/l) Chloride (mg/l) Sulfate (mg/l) LSP-01 85 30 100 2.37 3.6 300 ND 41 230 LSP-02 82 24 110 2.75 3.6 260 ND 45 240 LSP-03 83 22 120 3.03 6.1 320 ND 30 240 LSP-04 20 1.7 100 5.76 3.1 130 ND 34 110 64.5 12.5 49 1.50 4.05 269 ND 12.5 75.5 85 20 71 1.80 4.6 320 ND 21 120 60.5 19 110 3.15 3.85 280 ND 34 185 LSP-10 78 12 130 3.62 5.0 260 ND 34 280 LSP-11 12 ND 140 11.12 1.9 100 4.2 41 150 LSP-12 34 28 9.6 0.30 0.82 210 3.1 9.0 20 LSP-14 95 18 110 2.71 5.3 270 ND 33 260 LSP-15/16 100 23 120 2.81 5.3 285 ND 33 295 LSP-17 83 16 110 2.89 4.6 260 ND 28 230 LSP-18/19 18 2.8 50 2.93 2.8 170 ND 4.3 18 LSP-20 16 2.6 95 5.81 2.5 120 ND 26 95 LSP-21 84 20 29 0.74 3.0 230 ND 31 91 LSP-22 330 95 500 6.24 15 270 ND 810 700 LSP-24 67 9.8 15 0.45 1.2 220 ND 4.9 26 LSP-26 79 17 46 1.22 1.9 320 ND 30 34 LSP-28 79 20 150 3.91 6.4 230 ND 200 140 LSP-29/30 74 19 150 4.03 6.2 230 ND 205 125 LSP-31 56 41.5 51 1.26 2.7 370 ND 39 43 LSP-32 37 11 120 4.01 3.05 320 ND 18 86 LSP-33 72 49.5 67.5 1.48 1.45 540 ND 28 51 LSP-34/35 48 31.5 19 0.52 0.91 275 ND 5.45 40.5 LSP-36 47 26 20 0.57 0.845 240 ND 4.9 41 LSP-37/38 3.5 ND 64.5 7.60 0.63 107 28 3.1 3.9 LSP-39 73 18 20 0.54 5.6 290 ND 9.7 47 LSP-40 91 12 36 0.94 3.4 240 ND 10 140 LSP-05/06 LSP-07 LSP-08/09 bold = constituent level exceeds Primary or Secondary MCL Basic Data 45 Appendix B. Groundwater Quality Data, Lower San Pedro Basin, 1999-2000--Continued Sample # Nitrate-Nitrite-N (mg/l) Nitrate-N (mg/l) Nitrite-N (mg/l) TKN (mg/l) Ammonia-N (mg/l) Total Phosphorus (mg/l) LSP-01 0.72 0.72 ND 0.085 ND ND LSP-02 0.71 0.71 ND 0.080 ND ND LSP-03 ND ND ND 0.15 0.078 0.052 LSP-04 0.90 0.90 ND ND ND ND LSP-05/06 0.92 0.92 ND ND ND 0.061 LSP-07 2.3 2.3 ND ND ND 0.042 LSP-08/09 1.3 0.77 ND ND ND 0.022 LSP-10 0.45 0.45 ND ND ND ND LSP-11 0.34 0.34 ND ND ND ND LSP-12 0.52 0.52 ND ND 0.024 0.032 LSP-14 0.42 0.42 ND ND ND 0.027 LSP-15/16 0.70 0.70 ND ND ND 0.055 LSP-17 0.25 0.25 ND ND ND 0.10 LSP-18/19 0.18 0.18 ND ND ND ND LSP-20 0.96 0.96 ND ND ND 0.033 LSP-21 3.9 3.9 ND ND ND ND LSP-22 30 29.78 0.22 0.30 ND ND LSP-24 2.3 2.3 ND ND ND ND LSP-26 6.8 6.8 ND 0.11 ND ND LSP-28 0.04 0.04 ND 0.30 0.17 0.042 LSP-29/30 0.05 0.05 ND 0.10 0.052 0.067 LSP-31 3.4 3.4 ND ND ND ND LSP-32 0.99 0.99 ND ND ND ND LSP-33 2.2 2.2 ND 0.070 ND 0.086 0.585 0.585 ND 1.2 ND 0.05 4.2 ND 0.054 LSP-34/35 LSP-36 ND ND ND LSP-37/38 0.31 0.31 ND ND ND 0.034 LSP-39 0.24 0.24 ND 0.082 ND 0.19 LSP-40 0.40 0.40 ND ND ND 0.068 bold = constituent level exceeds Primary or Secondary MCL italics = constituent exceeded holding time Basic Data 46 Appendix B. Groundwater Quality Data, Lower San Pedro Basin, 1999-2000--Continued Sample # Antimony (mg/l) Arsenic (mg/l) Barium (mg/l) Beryllium (mg/l) Boron (mg/l) Cadmium (mg/l) Chromium (mg/l) Copper (mg/l) Fluoride (mg/l) LSP-01 ND ND ND ND 0.15 ND ND 0.013 1.3 LSP-02 ND ND ND ND 0.16 ND ND ND 1.3 LSP-03 ND 0.012* ND ND 0.18 ND ND ND 1.2 LSP-04 ND 0.016* ND ND 0.14 ND ND ND 5.2 LSP-05/06 ND ND ND ND ND ND ND ND 0.825 LSP-07 ND ND ND ND 0.13 ND ND ND 0.82 LSP-08/09 ND ND ND ND 0.205 ND ND ND 1.4 LSP-10 ND 0.013* ND ND 0.17 ND ND ND 4.0 LSP-11 ND 0.020* ND ND 0.17 ND ND ND 6.6 LSP-12 ND ND ND ND ND ND ND ND 0.13 LSP-14 ND ND ND ND 0.13 ND ND ND 2.1 LSP-15/16 ND ND ND ND 0.14 ND ND ND 2.45 LSP-17 ND ND ND ND 0.14 ND ND ND 2.2 LSP-18/19 ND ND ND ND ND ND ND ND 1.1 LSP-20 ND 0.048* ND ND 0.10 ND ND ND 3.0 LSP-21 ND ND ND ND ND ND ND ND 0.51 LSP-22 ND ND ND ND 0.72 0.001 ND ND 0.45 LSP-24 ND ND ND ND ND ND ND ND 0.32 LSP-26 ND ND ND ND ND ND ND ND 0.86 LSP-28 ND ND ND ND 0.18 ND ND ND 1.2 LSP-29/30 ND ND ND ND 0.20 ND ND ND 1.2 LSP-31 ND ND 0.20 ND 0.38 ND ND 0.007 0.78 LSP-32 ND ND ND ND 0.13 ND ND ND 1.6 LSP-33 ND 0.11 0.185 ND 0.30 ND ND ND 0.30 LSP-34/35 ND ND ND ND ND ND ND ND 0.555 LSP-36 ND ND ND ND ND ND ND ND 0.33 LSP-37/38 ND 0.021* ND ND ND ND 0.0052 ND 1.8 LSP-39 ND ND ND ND ND ND ND ND 0.22 LSP-40 ND ND ND ND ND ND ND ND 1.2 bold = constituent level exceeds Primary or Secondary MCL * = concentration exceeds the revised arsenic SDW Primary MCL of 0.01 mg/l which becomes effective in 2006 Basic Data 47 Appendix B. Groundwater Quality Data, Lower San Pedro Basin, 1999-2000--Continued Sample # Iron (mg/l) Lead (mg/l) Manganese (mg/l) Mercury (mg/l) Nickel (mg/l) Selenium (mg/l) Silver (mg/l) Thallium (mg/l) Zinc (mg/l) LSP-01 0.34 ND ND ND ND ND ND ND ND LSP-02 ND ND ND ND ND ND ND ND ND LSP-03 0.81 ND 0.76 ND ND 0.0069 ND ND ND LSP-04 ND ND ND ND ND ND ND ND 0.11 LSP-05/06 ND ND ND ND ND ND ND ND ND LSP-07 ND ND ND ND ND 0.0077 ND ND ND LSP-08/09 ND ND ND ND ND 0.0074 ND ND ND LSP-10 ND ND ND ND ND 0.0089 ND ND ND LSP-11 ND ND ND ND ND ND ND ND ND LSP-12 ND ND ND ND ND ND ND ND 0.059 LSP-14 ND ND ND ND ND 0.0060 ND ND ND LSP-15/16 ND 0.0055 ND ND ND 0.0074 ND ND 0.095 LSP-17 ND ND ND ND ND ND ND ND ND LSP-18/19 ND ND ND ND ND ND ND ND ND LSP-20 ND ND ND ND ND ND ND ND ND LSP-21 ND ND ND ND ND ND ND ND ND LSP-22 1.2 ND 0.58 ND ND 0.007 ND ND ND LSP-24 ND ND ND ND ND ND ND ND 0.11 LSP-26 ND ND ND ND ND ND ND ND 0.34 LSP-28 ND ND 0.056 ND ND ND ND ND ND LSP-29/30 ND ND ND ND ND ND ND ND ND LSP-31 ND ND ND ND ND ND ND ND ND LSP-32 ND ND ND ND ND ND ND ND ND LSP-33 ND ND ND ND ND ND ND ND ND LSP-34/35 ND ND ND ND ND ND ND ND 0.195 LSP-36 ND ND ND ND ND ND ND ND ND LSP-37/38 ND ND ND ND ND ND ND ND ND LSP-39 ND ND ND ND ND ND ND ND ND LSP-40 ND ND ND ND ND ND ND ND ND bold = constituent level exceeds Primary or Secondary MCL Basic Data 48 Appendix B. Groundwater Quality Data, Lower San Pedro Basin, 1999-2000–Continued Sample # Radon-222 (pCi/L) Alpha (pCi/L) Beta (pCi/L) Ra-226 (pCi/L) Uranium (µg/l) VOCs (µg/l) GWPL Pesticides Type of Chemistry LSP-01 -- -- -- -- -- -- -- mixed-mixed LSP-02 430+/-83 -- -- -- -- ND -- mixed-mixed LSP-03 -- -- -- -- -- -- -- mixed-mixed LSP-04 -- -- -- -- -- ND -- sodium-mixed 384+/-55 -- -- -- -- ND -- mixed-bicarbonate -- -- -- -- -- -- -- mixed-bicarbonate LSP-08/09 925+/-94 -- -- -- -- ND -- sodium-mixed LSP-10 350+/-65 -- -- -- -- ND -- sodium-sulfate LSP-11 550+/-77 -- -- -- -- ND -- sodium-mixed LSP-12/13 -- 0.76+/-0.4 < 1.25 -- -- -- -- magnesium-bicarbonate LSP-14 -- -- -- -- -- -- -- mixed-mixed 375+/-68 -- -- -- -- ND -- mixed-sulfate -- -- -- -- -- -- -- mixed-mixed LSP-18/19 1050+/-93 -- -- -- -- ND -- sodium-bicarbonate LSP-20 910+/-88 -- -- -- -- ND -- sodium-mixed LSP-21 -- -- -- -- -- ND -- calcium-bicarbonate 1080+/-95 -- -- -- -- -- -- mixed-chloride LSP-24 -- 7.3+/-1.0 3.3+/-0.88 < LLD -- -- -- calcium-bicarbonate LSP-26 -- 19+/-1.4 4.0+/-0.94 < LLD 6.9+/-1.8 ND -- calcium-bicarbonate LSP-28 -- -- -- -- -- ND -- sodium-mixed 295+/-58 -- -- -- -- -- -- sodium-mixed LSP-31 -- 12+/-0.96 5.9+/-1.1 < LLD -- ND -- bicarbonate-mixed LSP-32 -- -- -- -- -- ND -- sodium-bicarbonate LSP-33 -- -- -- -- -- -- -- mixed-bicarbonate LSP-34/35 -- 1.5+/-0.72 < LLD -- -- -- -- mixed-bicarbonate LSP-36 -- -- -- -- -- -- -- mixed-bicarbonate LSP-37/38 -- 10.85+/-1. 2.25+/-0.9 < LLD -- ND -- sodium-bicarbonate LSP-05/06 LSP-07 LSP-15/16 LSP-17 LSP-22/23 LSP-29/30 bold = Primary MCL Exceedance LLD = Lower Limit of Detection italics = constituent exceeded holding time Basic Data 49 Appendix B. Groundwater Quality Data, Lower San Pedro Basin, 1999-2000--Continued Sample # ADEQ # MCL Exceedances Temp (o C) pH-field (su) SC-lab (FS/cm) TDS (mg/l) Hardness (mg/l) Total Alk (mg/l) Turbidity (ntu) LSP-41 28278 TDS, F 21.07 7.75 980 650 290 240 0.03 LSP-42 58449 As* 13.80 8.15 310 220 120 140 0.97 LSP-43 58786 As*, Mn 11.21 8.07 590 400 240 220 0.63 LSP-44 28877 TDS, SO4, As*, F 19.39 7.56 1200 790 310 230 0.13 LSP-45/46 58450 TDS, SO4, As* 17.88 7.52 1400 855 325 225 0.38 LSP-47 58542 pH, TDS, As*, F 22.27 8.86 820 500 14 140 0.04 LSP-48 58546 -- 29.46 7.77 430 250 120 180 0.03 LSP-49 58590 -- 21.14 7.30 740 450 250 220 0.03 LSP-50/51 58591 TDS, Cl, SO4, F 25.21 8.26 4450 2850 257 110 2.5 LSP-52 58592 -- 21.51 8.23 560 320 220 220 0.59 LSP-53 31851 -- 24.91 7.43 580 330 220 240 0.67 LSP-54 38003 -- 17.67 7.41 670 380 320 270 0.06 LSP-55 58593 -- 20.18 7.62 640 380 270 250 0.11 LSP-56/57 33951 F, Mn, Gross Alpha 18.55 7.93 850 480 170 300 2.35 LSP-58 58594 TDS,SO4,Sb,F,Fe,Mn 21.74 7.31 1940 800 880 150 110 LSP-59 38952 -- 16.95 7.67 550 320 240 250 0.34 LSP-60 58652 -- 19.61 7.43 440 270 190 200 0.24 LSP-61 58653 -- 17.88 7.23 524 290 250 250 3.1 LSP-62 58654 -- 19.77 7.12 560 310 310 260 0.13 LSP-63/64 58655 -- 21.95 7.81 330 195 160 150 0.33 LSP-65 58656 -- 19.01 7.53 490 310 210 180 0.10 LSP-66 58657 TDS, SO4, Sb 20.11 7.22 1100 820 500 200 0.26 LSP-67 58658 TDS, SO4, As*, F 22.90 7.16 1900 1400 540 240 0.11 LSP-69/70 58806 -- 21.33 7.29 240 190 87 100 0.64 LSP-71 58807 -- 22.91 7.12 170 140 60 65 3.8 LSP-72 58808 -- 22.23 7.28 420 280 200 170 0.40 LSP-73 58819 Mn 20.67 7.10 780 480 330 360 0.54 LSP-74 58820 -- 25.13 7.94 270 200 150 120 8.8 LSP-75 58818 TDS, Mn 19.52 7.41 810 580 440 248 0.66 italics = constituent exceeded holding time bold = constituent level exceeds Primary or Secondary MCL * = concentration exceeds the revised arsenic SDW Primary MCL of 0.01 mg/l which becomes effective in 2006 Basic Data 50 Appendix B. Groundwater Quality Data, Lower San Pedro Basin, 1999-2000--Continued Sample # Calcium (mg/l) Magnesium (mg/l) Sodium (mg/l) SAR (Value) Potassium (mg/l) Bicarbonate (mg/l) Carbonate (mg/l) Chloride (mg/l) Sulfate (mg/l) LSP-41 89 17 110 2.80 4.0 290 ND 30 240 LSP-42 45 6.6 22 0.81 1.1 170 ND 6.4 ND LSP-43 66 19 28 0.78 3.3 270 ND 15 61 LSP-44 94 22 130 3.14 5.3 280 ND 66 280 LSP-45/46 92.5 24 170 3.84 6.25 270 ND 155 260 LSP-47 9.6 ND 170 15.11 2.4 140 13 31 150 LSP-48 32 11 55 2.14 2.5 220 ND 8 28 LSP-49 73 18 68 1.85 3.0 270 ND 14 130 70.5 20 895 24.30 14.5 130 ND 705 1100 LSP-52 70 11 34 1.00 5.1 270 ND 9.4 57 LSP-53 63 17 42 1.21 0.79 290 ND 21 21 LSP-54 69 37 24 0.58 2.4 330 ND 22 47 LSP-55 72 23 42 1.11 0.53 300 18 18 58 LSP-56/57 39.5 17.5 140 4.62 2.65 370 ND 37 71.5 LSP-58 310 27 140 2.05 4.0 180 ND 15 970 LSP-59 84 8.9 30 0.83 2.6 300 ND 18 ND LSP-60 60 11 29 0.90 3.0 244 ND 9.3 34 LSP-61 80 14 22 0.60 1.7 305 ND 11 28 LSP-62 100 15 ND 0.00 ND 320 ND 4.6 39 LSP-63/64 48 9.7 12 0.41 2.05 180 ND 4.5 13 LSP-65 65 12 29 0.87 2.9 220 ND 9.5 62 LSP-66 160 23 68 1.33 3.2 240 ND 34 360 LSP-67 170 24 250 4.76 5.0 290 ND 64 680 LSP-69/70 27 3.8 17 0.81 2.1 120 ND 6.3 ND LSP-71 20 2.5 11 0.62 1.1 79 ND 3.4 11 LSP-72 69 3.2 15 0.48 1.5 210 ND 8.8 ND LSP-73 89 26 48 1.15 3.8 440 ND 26 46 LSP-74 37 6.8 9.8 0.38 1.8 150 ND 3.6 15 LSP-75 120 26 23 0.50 4.2 300 ND 4.8 210 LSP-50/51 bold = constituent level exceeds Primary or Secondary MCL italics = constituent exceeded holding time Basic Data 51 Appendix B. Groundwater Quality Data, Lower San Pedro Basin, 1999-2000--Continued Sample # Nitrate-Nitrite-N (mg/l) Nitrate -N (mg/l) Nitrite-N (mg/l) TKN (mg/l) Ammonia-N (mg/l) Total Phosphorus (mg/l) LSP-41 0.85 0.85 ND ND ND 0.036 LSP-42 ND ND ND 0.067 ND 0.059 LSP-43 ND ND ND 0.21 0.050 0.18 LSP-44 0.22 0.22 ND 0.077 ND 0.045 0.375 0.375 ND 0.12 ND 0.052 LSP-47 0.37 0.37 ND 0.09 ND 0.029 LSP-48 1.0 1.0 ND 0.057 ND ND LSP-49 0.99 0.99 ND ND ND ND LSP-50/51 ND ND ND ND ND ND LSP-52 N/A N/A ND 1.1 ND N/A LSP-53 3.7 3.7 ND 0.20 0.023 0.047 LSP-54 2.5 2.5 ND ND ND ND LSP-55 0.90 0.90 ND ND ND 0.036 LSP-56/57 ND ND ND ND 0.0225 ND LSP-58 0.23 0.166 0.064 0.068 0.074 0.35 LSP-59 1.2 1.2 ND ND 0.022 0.044 LSP-60 0.26 0.26 ND ND ND 0.046 LSP-61 ND ND ND 0.65 0.026 0.10 LSP-62 0.35 0.35 ND 0.05 ND 0.044 LSP-63/64 0.39 0.39 ND ND ND ND LSP-65 0.42 0.42 ND ND ND 0.057 LSP-66 2.8 2.8 ND 0.084 ND 0.026 LSP-67 0.74 0.74 ND 0.15 ND ND LSP-69/70 0.94 0.94 ND ND ND 0.14 LSP-71 0.17 0.17 ND 0.095 ND 0.12 LSP-72 6.4 6.4 ND 0.20 ND 0.26 LSP-73 0.44 0.44 ND 0.24 ND ND LSP-74 0.37 0.35 0.022 0.54 ND ND LSP-75 0.052 0.052 ND 0.13 ND ND LSP-45/46 bold = constituent level exceeds Primary or Secondary MCL italics = constituent exceeded holding time Basic Data 52 Appendix B. Groundwater Quality Data, Lower San Pedro Basin, 1999-2000--Continued Sample # Antimony (mg/l) Arsenic (mg/l) Barium (mg/l) Beryllium (mg/l) Boron (mg/l) Cadmium (mg/l) Chromium (mg/l) Copper (mg/l) Fluoride (mg/l) LSP-41 ND ND ND ND 0.16 ND ND ND 2.2 LSP-42 ND 0.011* ND ND ND ND ND ND 0.53 LSP-43 ND 0.018* ND ND ND ND ND 0.014 0.54 LSP-44 ND 0.011* ND ND 0.22 ND ND ND 2.0 LSP-45/46 ND 0.0043 0.032 ND 0.25 ND ND ND 1.35 LSP-47 ND 0.022* ND ND 0.30 ND ND ND 13 LSP-48 ND ND ND ND ND ND ND ND 1.3 LSP-49 ND ND ND ND 0.18 ND ND ND 1.0 LSP-50/51 ND ND ND ND 2.0 ND ND ND 4.3 LSP-52 ND ND ND ND ND ND ND ND 1.4 LSP-53 ND ND ND ND ND ND ND ND 0.68 LSP-54 ND ND 0.13 ND ND ND ND ND 0.71 LSP-55 ND ND 0.12 ND ND ND ND ND 0.93 LSP-56/57 ND ND ND ND 0.225 ND ND ND 4.25 LSP-58 0.0073 ND ND ND 0.30 ND ND ND 7.4 LSP-59 ND ND ND ND ND ND ND ND 0.48 LSP-60 ND ND ND ND ND ND ND ND 0.86 LSP-61 ND ND ND ND ND ND ND ND 0.35 LSP-62 ND ND ND ND ND ND ND ND ND LSP-63/64 ND ND ND ND ND ND ND ND 0.25 LSP-65 ND ND ND ND ND ND ND ND 0.78 LSP-66 0.75 ND ND ND ND ND ND ND 1.1 LSP-67 ND 0.013* ND ND 0.42 ND ND ND 4.1 LSP-69/70 ND ND ND ND ND ND ND ND 0.22 LSP-71 ND ND ND ND ND ND ND ND 0.20 LSP-72 ND ND ND ND ND ND ND ND ND LSP-73 ND ND ND ND ND ND ND ND 0.51 LSP-74 ND ND ND ND ND ND ND ND 0.24 LSP-75 ND ND ND ND ND ND ND ND 0.40 bold = constituent level exceeds Primary or Secondary MCL italics = constituent exceeded holding time * = concentration exceeds the revised arsenic SDW Primary MCL of 0.01 mg/l which becomes effective in 2006 Basic Data 53 Appendix B. Groundwater Quality Data, Lower San Pedro Basin, 1999-2000--Continued Sample # Iron (mg/l) Lead (mg/l) Manganese (mg/l) Mercury (mg/l) Nickel (mg/l) Selenium (mg/l) Silver (mg/l) Thallium (mg/l) Zinc (mg/l) LSP-41 ND ND ND ND ND 0.0070 ND ND ND LSP-42 ND ND ND ND ND ND ND ND ND LSP-43 0.15 ND 0.12 ND ND 0.008 ND ND ND LSP-44 ND ND ND ND ND 0.014 ND ND ND LSP-45/46 ND ND ND ND ND 0.010 ND ND ND LSP-47 ND ND ND ND ND ND ND ND ND LSP-48 ND ND ND ND ND ND ND ND ND LSP-49 ND ND ND ND ND ND ND ND ND LSP-50/51A 0.27 ND ND ND ND ND ND ND ND LSP-51B ND ND ND ND ND ND ND ND ND LSP-53 ND ND ND ND ND ND ND ND ND LSP-54 ND ND ND ND ND ND ND ND ND LSP-55 ND ND ND ND ND ND ND ND ND LSP-56/57 ND ND 0.10 ND ND ND ND ND 0.285 LSP-58 2.1 ND 0.50 ND ND ND ND ND ND LSP-59 ND ND ND ND ND ND ND ND ND LSP-60 ND ND ND ND ND ND ND ND ND LSP-61 ND ND ND ND ND ND ND ND ND LSP-62 ND ND ND ND ND ND ND ND ND LSP-63/64 ND ND ND ND ND ND ND ND ND LSP-65 ND ND ND ND ND ND ND ND ND LSP-66 ND ND ND ND ND ND ND ND ND LSP-67 ND ND ND ND ND ND ND ND ND LSP-69/70 ND ND ND ND ND ND ND ND 0.058 LSP-71 0.12 ND ND ND ND ND ND ND 0.064 LSP-72 ND ND ND ND ND ND ND ND ND LSP-73 ND ND 0.12 ND ND ND ND ND ND LSP-74 ND ND ND ND ND ND ND ND 0.18 LSP-75 ND ND 0.13 ND ND ND ND ND 0.22 bold = constituent level exceeds Primary or Secondary MCL italics = constituent exceeded holding time Basic Data 54 Appendix B. Groundwater Quality Data, Lower San Pedro Basin, 1999-2000–Continued Sample # Radon-222 (pCi/L) Alpha (pCi/L) Beta (pCi/L) Ra-226 (pCi/L) Uranium (µg/l) VOCs (µg/l) GWPL Pestidicdes Type of Chemistry LSP-39 -- 2.9+/-0.84 4.9+/-1. 0 -- -- -- -- calcium-bicarbonate LSP-40 374+/-48 -- -- -- -- -- ND calcium-sulfate LSP-41 -- -- -- -- -- -- ND calcium-bicarbonate LSP-42 -- 3.5 +/10.76 < LLD -- -- -- -- calcium-bicarbonate LSP-43 -- -- -- -- -- -- -- calcium-bicarbonate LSP-44 317+/-48 -- -- -- -- ND -- mixed-bicarbonate LSP-45/46 300+/-47 -- -- -- -- ND -- mixed-mixed LSP-47 554+/-45 -- -- -- -- ND -- sodium-bicarbonate LSP-48 577+/-46 -- -- -- -- ND -- mixed-bicarbonate LSP-49 -- -- -- -- -- -- -- mixed-bicarbonate 601+/-43 -- -- -- -- -- -- sodium-mixed LSP-52 -- -- -- -- -- -- -- calcium-bicarbonate LSP-53 -- 7.0+/-1.1 2.5+/-0.84 < LLD -- -- -- mixed-mixed LSP-54 -- 6.1+/-1.1 3.7+/-0.86 < LLD -- -- -- mixed-bicarbonate LSP-55 -- 7.4+/-1.1 1.8+/-0.82 < LLD -- -- -- mixed-bicarbonate LSP-56/57 -- 68+/-3.0 16.5+/-1.1 < LLD 61.5+/-4.7 -- -- sodium-bicarbonate LSP-58a -- -- -- -- -- ND* -- calcium-sulfate LSP-59 -- -- -- -- -- -- -- calcium-bicarbonate LSP-58b -- -- -- -- -- ND* -- calcium-sulfate LSP-60 -- -- -- -- -- -- -- calcium-bicarbonate LSP-61 -- -- -- -- -- -- -- mixed-bicarbonate LSP-62 -- < LLD < LLD -- -- -- -- calcium-bicarbonate 80+/-20 -- -- -- -- ND -- calcium-bicarbonate LSP-65 -- -- -- -- -- -- -- calcium-bicarbonate LSP-66 -- -- -- -- -- -- -- calcium-sulfate LSP-67 -- -- -- -- -- -- -- mixed-sulfate LSP-50/51 LSP-63/64 bold = Primary MCL Exceedance LLD = Lower Limit of Detection italics = constituent exceeded holding time * = methylethyl ketone and another unidentified VOC detected Basic Data 55 Appendix B. Groundwater Quality Data, Lower San Pedro Basin, 1999-2000--Continued Sample # ADEQ # MCL Exceedances Temp (o C) pH-field (su) SC-lab (FS/cm) TDS (mg/l) Hardness (mg/l) Total Alk (mg/l) Turbidity (ntu) 25.18 7.21 720 400 360 330 0.07 LSP-76 55034 LSP-77/78** 58801 pH, As* 29.40 9.31 505 300 17 194 0.05 LSP-80 58802 pH, Mn 22.95 9.14 320 290 130 103 2.5 LSP-81 58803 pH, F 18.66 8.53 190 150 53 88 0.41 LSP-82 58804 TDS N/A 7.46 1200 730 470 310 0.05 LSP-83 58805 TDS, SO4, F 24.63 7.40 1800 1100 350 260 1.7 bold = constituent level exceeds Primary or Secondary MCL italics = constituent exceeded holding time * = concentration exceeds the revised arsenic SDW Primary MCL of 0.01 mg/l which becomes effective in 2006 ** Reported for information purposes only as the sample site was in the Donnelly Wash groundwater basin. Appendix B. Groundwater Quality Data, Lower San Pedro Basin, 1999-2000--Continued Sample # LSP-76 Calcium (mg/l) Magnesium (mg/l) Sodium (mg/l) SAR (Value) Potassium (mg/l) Bicarbonate (mg/l) Carbonate (mg/l) Chloride (mg/l) Sulfate (mg/l) 78 38 15 0.35 2.0 400 ND 30 26 7 ND 120 52.20 ND 230 ND 14.5 35 LSP-80 38 6.2 14 0.56 11 126 ND 7.1 46 LSP-81 20 1.3 21 1.23 ND 110 ND ND ND LSP-82 120 39 68 1.38 0.65 380 ND 51 230 LSP-83 90 26 250 5.98 5.9 320 ND 210 360 LSP-77/78 bold = constituent level exceeds Primary or Secondary MCL italics = constituent exceeded holding time ** Reported for information purposes only as the sample site was in the Donnelly Wash groundwater basin. Appendix B. Groundwater Quality Data, Lower San Pedro Basin, 1999-2000--Continued Sample # Nitrate-Nitrite-N (mg/l) Nitrate-N (mg/l) Nitrite-N (mg/l) TKN (mg/l) Ammonia-N (mg/l) Total Phosphorus (mg/l) LSP-76 0.94 0.94 ND ND ND ND LSP-77/78** 0.64 0.64 ND ND ND 0.022 LSP-80 0.032 0.032 ND 5.2 0.096 0.31 LSP-81 0.19 0.19 ND 0.14 ND ND LSP-82 6.6 6.6 ND 0.13 ND 0.040 LSP-83 ND ND ND 0.090 ND 0.056 bold = constituent level exceeds Primary or Secondary MCL italics = constituent exceeded holding time ** Reported for information purposes only as the sample site was in the Donnelly Wash groundwater basin. Basic Data 56 Appendix B. Groundwater Quality Data, Lower San Pedro Basin, 1999-2000--Continued Sample # Antimony (mg/l) Arsenic (mg/l) Barium (mg/l) Beryllium (mg/l) Boron (mg/l) Cadmium (mg/l) Chromium (mg/l) Copper (mg/l) Fluoride (mg/l) LSP-76 ND ND 0.14 ND ND ND ND ND 0.38 LSP-77/78** ND 0.011* ND ND 0.32 ND ND ND 1.95 LSP-80 ND ND ND ND ND ND ND ND 0.36 LSP-81 ND ND ND ND ND ND ND ND 2.8 LSP-82 ND ND ND ND 0.11 ND ND ND 0.30 LSP-83 ND ND ND ND ND ND ND ND 2.0 bold = constituent level exceeds Primary or Secondary MCL italics = constituent exceeded holding time ** Reported for information purposes only as the sample site was in the Donnelly Wash grondwater basin. * = concentration exceeds the revised arsenic SDW Primary MCL of 0.01 mg/l which becomes effective in 2006 Appendix B. Groundwater Quality Data, Lower San Pedro Basin, 1999-2000--Continued Sample # Iron (mg/l) Lead (mg/l) Manganese (mg/l) Mercury (mg/l) Nickel (mg/l) Selenium (mg/l) Silver (mg/l) Thallium (mg/l) Zinc (mg/l) LSP-76 ND ND ND ND ND ND ND ND ND LSP-77/78** ND ND ND ND ND ND ND ND ND LSP-80 0.28 ND 0.23 ND ND ND ND ND ND LSP-81 ND ND ND ND ND ND ND ND ND LSP-82 ND ND ND ND ND ND ND ND 0.052 LSP-83 ND ND ND ND ND ND ND ND 0.064 bold = constituent level exceeds Primary or Secondary MCL italics = constituent exceeded holding time ** Reported for information purposes only as the sample site was in the Donnelly Wash groundwater basin. Basic Data 57 Appendix B. Groundwater Quality Data, Lower San Pedro Basin, 1999-2000–Continued Sample # Radon-222 (pCi/L) Alpha (pCi/L) Beta (pCi/L) Ra-226 (pCi/L) Uranium (µg/l) VOCs (µg/l) GWPL Pestidicde Type of Chemistry -- 0.75+/-0.50 1.9+/-0.86 -- -- ND -- calcium-bicarbonate LSP-71 128+/-15 -- -- -- -- -- -- calcium-bicarbonate LSP-72 -- -- -- -- -- ND -- calcium-bicarbonate LSP-73 -- 4.6+/-0.68 4.6+/-0.98 -- -- -- -- calcium-bicarbonate LSP-74 -- -- -- -- -- -- -- calcium-bicarbonate LSP-75 -- 8.7+/-0.82 6.0+/-1.0 < LLD -- -- -- calcium-bicarbonate LSP-76 -- 2.1 +/- 0.62 2.6 +/- 0.09 -- -- Chloroform 4.4 -- calcium-bicarbonate 536+/-55 -- -- -- -- -- -- sodium-bicarbonate LSP-80 -- 0.96+/-0.58 11+/-1.1 -- -- -- -- calcium-bicarbonate LSP-81 -- -- -- -- -- -- -- mixed-bicarbonate LSP-82 -- 3.1+/-0.62 1.5+/-0.98 -- -- -- -- mixed-mixed LSP-83 348+/-35 -- -- -- -- ND -- sodium-mixed LSP-69/70 LSP-77/78* bold = Primary MCL Exceedance LLD = Lower Limit of Detection italics = constituent exceeded holding time * Reported for information purposes only as the sample site was in the Donnelly Wash groundwater basin. Basic Data 58 Appendix C. Groundwater Quality Data by Aquifer, Lower San Pedro Basin, 1999-2000 Hardrock Constituent # of sites Median Unconfined Basin-Fill 95% CIs # of sites Median 95% CIs Floodplain # of sites Median Confined Basin-Fill 95% CIs # of sites Median 95% CIs Physical Parameters and General Mineral Characteristics Temp. 20 19.7 17.1 to 21.9 9 22.9 19.0 to 26.5 27 20.8 20.2 to 22.2 4 23.9 14.8 to 39.5 pH-field 23 7.43 7.38 to 7.94 9 7.45 7.16 -to 7.86 27 7.44 7.41 to 7.66 4 8.37 7.74 to 9.01 Turbidity 23 0.6 0.3 to 1.9 9 0.4 -0.9 to 7.6 27 0.4 -3.1 to 13.6 4 0.1 -1.2 to 2.6 Total Alk. 23 250 200 to 275 9 170 118 to 203 27 220 200 to 209 4 125 83 to 158 SC-lab 23 580 484 to 695 9 430 - 139 to 1859 27 1000 850 to 1178 4 760 -1499 to 4644 Hardness 23 240 194 to 296 9 200 15 to 556 27 280 242 to 362 4 45 -96 to 283 TDS 23 335 307 to 427 9 280 -98 to 1204 27 690 534 to 741 4 475 -974 to 2974 Major Ions Calcium 23 66 50 to 76 9 67 10 to 156 27 83 68 to 111 4 15 -18 to 73 Magnesium 23 19 16 to 27 9 10 -4 to 41 27 19 16 to 21 4 2 -9 to 21 Sodium 23 24 24 to 49 9 15 -44 to 202 27 110 85 to 130 4 155 -308 to 936 Potassium 23 1.7 1.1 to 3.1 9 2.1 0.4 to 7.2 27 4.1 3.9 to 4.9 4 2.6 -4.2 to 15.1 Bicarbonate 23 300 239 to 334 9 210 143 to 248 27 270 244 to 279 4 135 89 to 181 Chloride 23 15 11 to 23 9 8.8 -103 to 306 27 30 27 to 76 4 36 -345 to 737 Sulfate 23 41 25 to 74 9 26 -58 to 285 27 230 150 to 309 4 150 -442 to 1152 Basic Data 59 Appendix C. Groundwater Quality Data by Aquifer, Lower San Pedro Basin, 1999-2000–Continued Hardrock Constituent # of sites Median Unconfined Basin-Fill 95% CIs # of sites Median 95% CIs Floodplain Confined Basin-Fill # of sites Median 95% CIs # of sites Median 95% CIs Nutrients Nitrate (N) 23 0.52 0.52 to 2.24 9 0.9 -2.4 to 12.4 26 0.56 0.44 to 0.96 4 0.26 -0.04 to 0.49 Phosphorus 23 0.04 0.03 to 0.09 9 0.01 0.00 to 0.14 26 0.04 0.02 to 0.08 4 0.01 0.00 to 0.03 TKN 23 0.07 -0.02 to 1.14 9 0.08 0.01 to 0.28 27 0.25 0.02 to 0.19 4 0.03 -0.01 to 0.09 Trace Elements Boron 23 0.05 0.05 to 0.12 9 0.05 -0.04 to 0.31 27 0.14 0.11 to 0.18 4 0.24 -0.83 to 2.09 Fluoride 23 0.51 0.38 to 1.21 9 0.25 -0.43 to 2.10 27 1.35 1.34 to 2.46 4 5.45 -1.76 to 14.3 Radiochemistry Constituents Gross Alpha 17 4.6 1.1 to17.4 2 5.1 -22.9 to 33.1 -- -- -- -- -- -- Gross Beta 17 2.5 1.9 to 6.1 2 4.1 -6.1 to 14.3 -- -- -- -- -- -- Radon -- -- -- 3 128 -972 to 1830 12 374 323 to 608 4 576 304 to 1074 Well Characteristics GW Depth 8 40 -26 to 224 7 80 22 to 260 26 26 23 to 39 4 825 -171 to 1836 Well Depth 8 144 49 to 345 8 310 135 to 436 26 100 91 to 144 4 825 -171 to 1836 Basic Data 60 Appendix D. 601/602 Volatile Organic Compounds (VOCs) Analyte List Benzene cis-1,2-Dichloroethene * Bromodichloromethane trans-1,2-Dichlorothene Bromoform 1,2-Dichloropropane Bromomethane cis-1,3-Dichloropropene Carbon Tetrachloride trans-1,3-Dichloropropene Chlorobenzene Ethylbenzene Chloroethane Methylene Chloride Chloroform Methyl-t-butyl ether (MTBE) * Chloromethane 1,1,2,2-Tetrachloroethane Dibromochloromethane Tetrachloroethene 1,2-Dichlorobenzene Toluene 1,3-Dichlorobenzene 1,1,1-Trichloroethane 1,4-Dichlorobenzene 1,1,2-Trichloroethane Dichlorodifluormethane Trichloroethene 1,1-Dichloroethane Trichlorofluormethane 1,2-Dichloroethene Vinyl Chloride 1,1-Dichloroethene Total Xylenes * * = Not a target compound listed by either method 601 or 602 but included as an analyte of interest. All VOCs have a Minimum Reporting Level (MRL) of 1 Fg/l. Source 43 . Basic Data 61 Appendix E. MRLs of Groundwater Protection List (GWPL) Pesticides GWPL Carbamates Diuron (Fragment) - 10 Pebulate - 5 Aldicarb - 1 DPX-M6316 - 25 Permethrin - 5 Carbaryl - 1 Endosulfan - 10 Phosmet - 10 Carbofuran - 1 EPTC - 5 Phosphamidon - 5 Methiocarb - 1 Ethofumesate - 10 Piperonyl Butoxide - 10 Methomyl - 1 Ethoprop - 10 Profenofos - 25 Oxamyl - 1 Fenamiphos - 25 Prometon - 10 GWPL Herbicides Fenarimol - 5 Prometryn - 10 2,4-D - 0.5 Fluazifop-p-butyl - 10 Pronamide - 10 Dacthal (Acids) - 0.5 Flucythrinate - 10 Propiconazole - 10 Dicamba - 0.5 Fluometuron (Fragment) - 10 Pyrazon - 10 GWPL Pesticides Fluridone - 10 Sethoxydim (Fragment) - 10 Ametryn - 10 Hexazinone - 5 Sulfometuron-methyl - 10 Azinphos-methyl - 10 Imazalil - 10 Sulprofos - 10 Bromacil - 10 Isaazophos - 10 Tebuthiuron - 25 Butylate - 10 Linuron - 10 Terbacil - 5 Captan - 25 Metalaxyl - 10 Terbufos - 10 Carboxin - 5 Metaldehyde - 5 Thidiazuron (Fragment) - 10 Chlorothalonil - 5 Methyl Parathion - 10 Triadimefon - 10 Cyanazine - 10 Metolachlor - 5 Vernolate - 5 Cycloate - 5 Metribuzin - 10 Vinclozolin - 10 Dacthal - 5 Mevinphos - 10 GWPL Pesticides - SIM Diazinon - 10 Myclobutanil - 10 Alachlor - 1 Dichloran - 10 Napropamide - 5 Atrazine - 1 Diethatyl ethyl - 10 Norflurazon - 10 Lindane 0.1 Dimethoate - 10 Parathion - 10 Simzine - 1 Diphenamid - 5 All units in Fg/l Source 43 Basic Data 62 Appendix F. Constituent Surface Water Quality Data Related to the LSP Study San Pedro River near Cascabel1 San Pedro River near Feldman2 Aravaipa Creek in Aravaipa Canyon3 Gila River near Calva 4 19.0 141.8 Quantity of Surface Water Flow Rate (cfs) 2.5 12.5 Physical Parameters and General Mineral Characteristics Temperature 18.1 20.5 18.5 18.6 pH-field 8.08 8.19 8.45 8.09 Turbidity 1.4 299 8 2810 Alkalinity, total 238 293 175 257 SC-lab 661 997 391 2506 Hardness 257 407 166 287 TDS 437 670 261 1500 Major Ions Calcium 73 130 52 79 Magnesium 17 22 9 22 Sodium 53 110 25 425 Potassium 4.6 6.3 3.0 7.5 Bicarbonate 288 353 203 308 Chloride 18 31 7 521 Sulfate 106 268 29 239 Fluoride 0.82 1.96 0.76 1.7 1 Mean of eight samples collected between November 1991 and May 2000 (7). Mean of nine samples collected between May 1998 and April 2001 (7). 3 Mean of ten samples collected between April 1992 and May 2001 (7). 4 Mean of four samples collected between November 1999 and August 2000 (55). 2 Basic Data 63 Appendix G. Drillers’ Logs of Selected Wells Representative of Each LSP Aquifer Stratum Thickness (ft) Depth (ft) Stratum Thickness (ft) Depth (ft) Brown shale with sand 10 1,015 Red clay and gravel 15 1,030 Sticky black clay 5 1,035 Confined Basin-Fill (Artesian) Aquifer - LSP-11 Floodplain Alluvium Sand and gravel 80 80 Basin-Fill Deposits Sand 5 85 Sticky brown shale 5 1,040 Sand and boulders 55 140 Red clay and gravel 65 1,105 Sand 20 160 Gypsum 5 1,110 Gravel 45 205 Red clay and gravel 25 1,135 Hard sand 15 220 Brown lime 9 1,144 Gravel 65 285 Red clay and gravel 16 1,160 Sand 30 315 Hard sand (some water) 35 1,195 Sand and boulders 136 451 Red clay 2 1,197 Sand 144 595 Hard brown sand 8 1,205 Sand and gravel 10 605 Hard clay lime 15 1,220 Gravel 20 625 Conglomerate w/ lime 37 1,257 Sand and gravel 35 660 Red clay 8 1,265 Running gravel 5 665 Hard conglomerate 2 1,267 Sand 80 745 Red clay 8 1,275 Clay and gravel 10 755 Sandstone (artesian water) 95 1,370 Sand and clay 10 765 Hard sandstone 70 1,440 Red beds 45 1,485 Consolidated to Semi-Consolidated Sedimentary Rocks Red clay and gravel 240 1,005 Floodplain Aquifer - LSP-14 Floodplain Alluvium Basin-Fill Deposits Clay 15 15 Sand and gravel 96 111 Clay 8 119 Hard conglomerate 40 205 Unconfined Basin-Fill Aquifer - LSP-71 Floodplain Alluvium Sandy soil 10 10 Hard rock ledge 10 215 Gravel, water at 35 feet 26 36 Sticky clay 20 235 Medium hard conglomerate 55 290 Basin-Fill Deposits Hard and soft conglomerate 109 145 Soft conglomerate, water 20 165 Crystalline and Consolidated Sedimentary Rocks Very hard rock 10 300 Basic Data 64 INVESTIGATION METHODS Various groundwater sites were sampled by the ADEQ Groundwater Monitoring Program to characterize regional groundwater quality in the LSP. Samples were collected at all sites for inorganic (physical parameters, major ions, nutrients, and trace elements) analyses. At many sites VOCs, radon, and radiochemistry samples were collected for analysis. At limited sites, samples were collected for GWPL pesticide analyses. No bacteria sampling was conducted since microbiological contamination problems in groundwater are often transient and subject to a variety of changing environmental conditions including soil moisture content and temperature.26 undamaged. Other factors such as casing access to determine groundwater depth and construction information were preferred but not essential. If no registered wells were available, springs or unregistered wells were randomly selected for sampling. Springs were considered adequate for sampling if they had a constant flow through a clearlydefined point of egress, and if the sample point had minimal surface impacts (Figure 33). Well information compiled from the ADWR well registry and spring characteristics are found in Appendix A. Sampling Strategy This study focused on groundwater quality conditions that are large in scale and persistent in time. This research is designed to identify regional degradation of groundwater quality such as occurs from non-point sources of pollution or a high density of point sources. The quantitative estimation of regional groundwater quality conditions requires the selection of sampling locations that follow scientific principles for probability sampling. Sampling in the LSP conducted by ADEQ followed a systematic stratified random site-selection approach. This is an efficient method because it requires sampling relatively few sites to make valid statistical statements about the conditions of large areas. This systematic element requires that the selected wells be spatially distributed while the random element ensures that every well within an aquifer has an equal chance of being sampled. This strategy also reduces the possibility of biased well selection and assures adequate spatial coverage throughout the study area. The main benefit of a statistically-designed sampling plan is that it allows much greater groundwater quality assumptions than would be allowable with a nonstatistical approach. Wells pumping groundwater for a variety of purposes - domestic, stock, and irrigation - were sampled for this study, provided each individual well met ADEQ requirements. A well was considered suitable for sampling if the well owner gave permission to sample, if a sampling point existed near the wellhead, and if the well casing and surface seal appeared to be intact and Figure 32. Springs that rise along fault planes are an often overlooked source of groundwater samples and are especially useful in lightly developed mountainous areas such as the LSP. ASARCO’s Kip Gambee observes ADEQ hydrologist Douglas Towne collect a sample from a headgate used to control inflow from a spring into Cooks Lake. Water is stored in this shallow reservoir until sufficient head is available to distribute the water in irrigation ditches.16 Several factors were considered to determine sample size for this study. Aside from administrative limitations on funding and personnel, this decision was based on three factors related to the conditions in the area:31 Investigation Methods 65 • < < Amount of groundwater quality data already available; Extent to which impacted groundwater is known or believed likely to occur; and Hydrologic complexity and variability of the area. Sample Collection The personnel who designed the LSP study were also responsible for the collection and interpretation of the data16. This protocol helps ensure that consistently high quality data are collected, from which are drawn relevant and meaningful interpretations. The sample collection methods for this study conformed to the Quality Assurance Project Plan (QAPP)4 and the Field Manual For Water Quality Sampling 11. While these sources should be consulted as references to specific sampling questions, a brief synopsis of the procedures involved in collecting a groundwater sample is provided. After obtaining permission from the owner to sample the well, the water level was measured with a sounder if the casing had access for a probe. The volume of water needed to purge the well three bore hole volumes was calculated from well log and on-site information. Physical parameters - temperature, pH, and specific conductivity - were monitored at least every five minutes using a Hydrolab multi-parameter instrument. Typically, after three bore volumes had been pumped and the physical parameters were stabilized within 10 percent, a sample representative of the aquifer was collected from a point as close to the wellhead as possible. In certain instances, it was not possible to purge three bore volumes. In these cases, at least one bore volume was evacuated and the physical parameters had stabilized within 10 percent. sealing the vials with Teflon caps, litmus paper was used to make certain the pH of the sample was below 2 su; additional HCl was added if necessary. VOC samples were also checked to make sure there was no headspace. Pesticide samples were collected in two bottles: an unpreserved, one-gallon, amber glass container; and, for carbamates which break down at higher pH levels, a 60 ml glass container preserved with 1.8 ml monochloro (13.3 percent ) - acedicitic acid (5.6 percent) and potassium hydroide (5.1 percent). The inorganic constituents were collected in 3, 1-liter polyethylene bottles: < Samples to be analyzed for dissolved metals were filtered into bottles preserved with 5 mL nitric acid (70 percent). An on-site positive pressure filtering apparatus with a 0.45 micron (µM) pore size groundwater capsule filter was used. < Samples to be analyzed for nutrients were collected in bottles preserved with 2 ml sulfuric acid (95.5 percent). < Samples to be analyzed for other parameters were collected in unpreserved bottles. Radiochemistry samples were collected in 2, collapsible 1-liter plastic containers and preserved with 5 ml nitric acid to reduce the pH below 2.5 su. All samples were kept at 40C using ice in an insulated cooler, with the exception of the radiochemistry samples. Chain of custody procedures were followed in sample handling. Samples for this study were collected between November 1999 and July 2000. Sample bottles were filled in the following order: Laboratory Methods 1. Radon 2. VOC 3. Pesticide 4. Inorganic 5. Radiochemistry Radon samples were collected in 2, unpreserved, 40-ml clear glass vials. Radon samples were filled so there was no air trapped within the bottles. The inorganic, VOC, and pesticide analyses for this study were conducted by the ADHS Laboratory in Phoenix, AZ, the only exception being inorganic splits analyzed by Del Mar Laboratory in Phoenix. A complete listing of inorganic parameters, including laboratory method, EPA water method, and Minimum Reporting Level (MRL) for both laboratories is provided in Table 5. VOC samples were collected in 2, 40-ml amber glass vials which contained 10 drops 1:1 hydrochloric (HCl) acid preservative prepared by the laboratory. Before Radon samples were analyzed by Lucas Laboratories of Sedona, AZ with the one split analyzed by Bolin Laboratories of Phoenix, AZ. Radiochemistry samples Investigation Methods 66 Table 5. ADHS/Del Mar Laboratory Methods Used for the LSP Study Constituent Instrumentation ADHS / Del Mar Water Method ADHS / Del Mar Minimum Reporting Level Physical Parameters and General Mineral Characteristics Alkalinity Electrometric Titration SM232OB 2/5 SC (FS/cm) Electrometric EPA 120.1/ SM2510B 1/2 Hardness Titrimetric, EDTA EPA 130.2 / SM2340B 10 / 1 pH (SU) Electrometric EPA 150.1 0.1 TDS Gravimetric EPA 160.1 / SM2540C 10 / 20 Turbidity (NTU) Nephelometric EPA 180.1 0.01 / 1 Major Ions Calcium ICP-AES EPA 200.7 5/2 Magnesium ICP-AES EPA 200.7 1 / 0.5 Sodium ICP-AES EPA 200.7 / EPA 273.1 5 Potassium Flame AA EPA 258.1 0.5 / 1 Chloride Potentiometric Titration Sulfate Colorimetric SM 4500 CLD / EPA 300.0 EPA 375.2 / EPA 300.0 1/5 10 / 5 Nutrients Nitrate as N Colorimetric EPA 353.2 0.02 / 0.50 Nitrite as N Colorimetric EPA 353.2 0.02 Ammonia Colorimetric EPA 350.1/ EPA 350.3 0.02 / 0.5 TKN Colorimetric EPA 351.2 / SM4500 0.05 / 0.5 Total Phosphorus Colorimetric EPA 365.4 / EPA 365.3 0.02 / 0.05 All units are mg/l except as noted Source22 43 Investigation Methods 67 Table 5. Constituent ADHS/Del Mar Laboratory Methods Used for the LSP Study--Continued Instrumentation ADHS / Del Mar Water Method ADHS / Del Mar Minimum Reporting Level Trace Elements Antimony Graphite Furnace AA EPA 200.9 0.005 / 0.004 Arsenic Graphite Furnace AA EPA 200.9 0.01 / 0.003 Barium ICP-AES EPA 200.7 0.1 / 0.01 Beryllium Graphite Furnace AA EPA 200.9 0.0005 Boron ICP-AES EPA 200.7 0.1 / 0.5 Cadmium Graphite Furnace AA EPA 200.9 0.001 / 0.0005 Chromium Graphite Furnace AA EPA 200.9 0.01 / 0.004 Copper Graphite Furnace AA EPA 200.9 0.01 / 0.004 Fluoride Ion Selective Electrode SM 4500 F-C 0.2 / 0.1 Iron ICP-AES EPA 200.7 0.1 Lead Graphite Furnace AA EPA 200.9 0.005 / 0.002 Manganese ICP-AES EPA 200.7 0.05 / 0.02 Mercury Cold Vapor AA SM 3112 B / EPA 245.1 0.0005 / 0.0002 Nickel ICP-AES EPA 200.7 0.1 / 0.05 Selenium Graphite Furnace AA EPA 200.9 0.005 / 0.004 Silver Graphite Furnace AA EPA 200.9 / EPA 273.1 0.001 / 0.005 Thallium Graphite Furnace AA EPA 200.9 0.002 Zinc ICP-AES EPA 200.7 0.05 All units are mg/l Source22 43 Investigation Methods 68 were analyzed by the Arizona Radiation Regulatory Agency (ARRA) laboratory in Phoenix, AZ with the one split analyzed by Lucas Laboratories of Sedona, AZ. The analysis of radiochemistry samples was treated according to the following SDW protocols 6. Gross alpha and gross beta were analyzed, and if the gross alpha levels exceeded 5 pCi/L, then radium-226 was measured. When radium-226 exceeded 3 pCi/L, radium-228 was measured. If gross alpha levels exceeded 15 pCi/L, then radium-226/228 and mass uranium were measured. Sample Numbers Sixty-three (63) sites - 46 wells and 17 springs - were sampled for the study. Various numbers and types of samples were collected and analyzed: < < < < < 63 - inorganic 25 - VOC 19 - radon 19 - radiochemistry 2 - pesticide DATA EVALUATION Quality Assurance Quality-assurance (QA) procedures were followed and quality-control (QC) samples were collected to quantify data bias and variability for the LSP study. The design of the QA/QC plan was based on recommendations included in the Quality Assurance Project Plan (QAPP) 4 and the Field Manual For Water Quality Sampling11. The types and numbers of QC samples collected for this study are as follows: Inorganic: VOC: Radiochemical: Radon: Pesticide: (6 duplicates, 7 splits, 4 blanks). (4 duplicates, 0 splits, 9 blanks). (3 duplicates, 1 splits, 0 blanks). (4 duplicates, 1 splits, 0 blanks). (0 duplicates, 0 splits, 0 blanks). Based on the QA/QC results which follow, sampling procedures and laboratory equipment did not significantly affect the groundwater quality samples of this study. Blanks - Equipment blanks for inorganic analyses were collected to ensure adequate decontamination of sampling equipment, and that the filter apparatus and/or deionized water were not impacting the groundwater quality sampling. Equipment blank samples for major ion and nutrient analyses were collected by filling unpreserved and sulfuric acid preserved bottles with deionized water. Equipment blank samples for trace element analyses were collected with deionized water that had been filtered into nitric acid preserved bottles. Systematic contamination was judged to occur if more than 50 percent of the equipment blank samples contained measurable quantities of a particular groundwater quality constituent. As such, SC-lab and turbidity were considered to be affected by systematic contamination; however, the extent of contamination was not considered significant. Both SC and turbidity were detected in all four equipment blanks. SC had a mean level of 2.3FS/cm which was less than 1 percent of the SC median level for the study. The SC detections may be explained in two ways: water passed through a deionizing exchange unit will normally have an SC value of at least 1 FS/cm while carbon dioxide from the air can dissolve in deionized water with the resulting bicarbonate and hydrogen ions imparting the observed conductivity31. Similarly, turbidity had a mean level of 0.11 ntu, less than 1 percent of the turbidity median level for the study. Testing indicates turbidity is present at 0.01 ntu in the deionized water supplied by the ADHS laboratory, and levels increase with time due to storage in ADEQ carboys43. The only other constituent detections were calcium (9.4 mg/l) and hardness (15 mg/l) in one equipment blank. There were no detections of any organic compounds in the nine VOC travel blanks. Duplicate Samples - Duplicate samples are identical sets of samples collected from the same source at the same time and submitted to the same laboratory. Data from duplicate samples provide a measure of variability from the combined effects of field and laboratory procedures. Duplicate samples were collected from sampling sites that were believed to have elevated constituent concentrations as judged by field SC values. Variability in constituent concentrations between each pair of duplicate samples is provided both in terms of absolute levels and as the percent difference. Percent difference is defined as the absolute difference between levels in the duplicate samples divided by the average level for the duplicate samples, multiplied by 100. Only parameters having Data Evaluation 69 levels exceeding the Minimum Reporting Level (MRL) were used in this analysis. Analytical results indicate that of the 26 constituents examined, the maximum difference between duplicate constituents rarely exceeded 17 percent (Table 6). Median differences were within 6 percent except for gross beta (17 percent), turbidity (25 percent), total phosphorus (58 percent), and TKN (78 percent). Gross beta concentrations were not large in absolute difference levels. Turbidity values can be impacted by the exceedance of this parameter’s holding time 43; this occurred frequently during the study due to turbidity’s short holding time. Phosphorus and TKN differences might be related to the analysis of these nutrients, which are particularly difficult and sensitive43. One pair of duplicate samples involving arsenic, total phosphorus, and TKN had a constituent concentration exceeding the MRL in one sample while its duplicate sample was a non-detect. In each of the three cases, the measurable concentration was at or close to the MRL resulting in little variation between the duplicate samples. Median differences were within 8 percent except for nitrate as nitrogen (31 percent). This nutrient only had a 0.05 mg/l median absolute difference however. Split samples were also evaluated using the non-parametric Sign test to determine if there were any significant (p # 0.05) differences between ADHS laboratory and Del Mar Laboratory analytical results 29. Results of the Sign test showed that none of the 13 constituents examined had significantly different concentrations between the laboratories. In addition, 24 pairs of split samples had a constituent concentration exceeding the MRL in one sample while there was a non-detection in its split sample. In all but five cases this discrepancy was due to different constituent MRLs between laboratories. The other five cases involved calcium (twice), hardness, selenium, and TKN. With the exception of TKN, these cases involved the measurable concentration close to the MRL resulting in little sample variation. Based on these results, the differences in parameter levels of split samples were not considered to significantly impact the groundwater quality data. Data Validation Six pairs of duplicate samples were also submitted to test for differences between field and lab filtering of cations and trace elements. The results indicated that with 126 pairs of duplicate constituents, all but 4 pairs had concentrations within 10 percent of each other. One pair involving sodium had a 17 percent difference while copper, iron, and zinc each had a pair in which there was a concentration above the MRL in one sample while the other sample was a non-detect. Based on these results, the differences in constituent concentrations of duplicate samples were not considered to significantly impact the groundwater quality data. Split Samples - Split samples are identical sets of samples collected from the same source at the same time that are submitted to two different laboratories to check for laboratory differences. Seven inorganic split samples were collected. Analytical results from the split samples were evaluated by examining the variability in constituent concentrations in terms of absolute levels and as the percent difference. The analytical work for this study was subjected to the following six QA/QC correlations. Cation/Anion Balances - In theory, water samples exhibit electrical neutrality. Therefore, the sum of milliequivalents per liter (meq/L) of the cations must equal the sum of the anions. However, this neutrality is rarely seen in practice due to unavoidable variation present in all water quality analyses. Still, cation/anion balance is an analysis such that, if found to be within acceptable limits, it can be assumed there are no gross errors in concentrations reported for major ions25. Overall, cation/anion balances of LSP samples were significantly correlated (regression analysis, p # 0.01) and within acceptable limits (90 - 110 percent) with the exception of three samples (LSP-35, 42, and 63) all which barely exceeded the acceptable limits. In each of the above instances, the cation sum was greater than the anion sum. Laboratory personnel indicated that other parameters not tested for, such as bromide and iodine, could have effected the cation/anion balances 43. Analytical results indicate that of the 18 constituents examined, the maximum difference between split constituents rarely exceeded 20 percent (Table 7). Data Evaluation 70 Table 6. Summary Results of LSP Duplicate Samples from ADHS/ARRA Laboratories Difference in Percent Parameter Difference in Concentrations Number Minimum Maximum Median Minimum Maximum Median Physical Parameters and General Mineral Characteristics Alkalinity, Total 6 0% 4% 0% 0 10 0 SC (FS/cm) 6 0% 3% 0% 0 30 0 Hardness 6 0% 17% 0% 0 15 0 pH (su) 6 0% 3% 1% 0 0.2 0.1 TDS 6 0% 9% 0% 0 30 0 Turbidity (ntu) 5 1% 160% 25% 0.01 1.6 0.09 Major Ions Bicarbonate 6 0% 10% 0% 0 10 0 Calcium 6 0% 6% 0% 0 3 0 Magnesium 6 0% 6% 0% 0 2 0 Sodium 6 0% 1% 0% 0 1 0 Potassium 6 0% 12% 1% 0 0.3 0.01 Chloride 6 0% 8% 0% 0 10 0 Sulfate 5 1% 8% 5% 1 10 10 Nutrients Ammonia 2 4% 8% --- 0.001 0.004 -- Nitrate (as N) 5 0% 16% 1% 0 0.01 0.008 Total Phosphorus 4 7% 94% 58% 0.01 0.051 0.038 TKN 1 78% -- -- 0.084 -- -- Trace Elements Boron 4 0% 5% 0% 0 0.1 0 Fluoride 6 0% 4% 0% 0 0.1 0 Lead 1 2% -- -- 0.001 -- -- Manganese 1 0% -- -- 0 -- -- Selenium 2 8% 14% -- 0.0006 0.001 -- Zinc 4 3% 16% 5% 0.003 0.03 0.009 Radiochemical Constituents Gross Alpha 31 5% 21% 6% 0.04 4 2.3 Gross Beta 31 6% 67% 17% 0.3 1.5 1.0 Radon-222 2 2% 17% 3% 10 50 10 4 All units are mg/l except as noted with certain physical parameters 1 ARRA Laboratory 2 Lucas Laboratory Data Evaluation 71 Table 7. Summary Results of LSP Split Samples From ADHS/Del Mar Labs Difference in Percent Constituents Difference in Levels Significance Number Minimum Maximum Median Minimum Maximum Median Physical Parameters and General Mineral Characteristics Alkalinity, total 7 0% 5% 0% 0 10 0 ns SC (FS/cm) 7 0% 32% 2% 0 230 10 ns Hardness 5 0% 11% 0% 0 10 0 ns pH (su) 7 1% 14% 1% 0.8 1.24 0.2 ns TDS 7 1% 13% 5% 10 100 20 ns Turbidity (ntu) 1 8% -- -- 0.2 -- -- ns Major Ions Calcium 5 1% 11% 2% 1 3 1 ns Magnesium 5 0% 8% 7% 0 .2 1 ns Sodium 7 0% 12% 5% 0 20 3 ns Potassium 5 0% 18% 7% 0 1.1 0.3 ns Chloride 7 1% 27% 8% 0.4 10 1 ns Sulfate 6 0% 18% 1% 0 20 1 ns Nutrients Nitrate as N 6 3% 86% 31% 0.01 0.78 0.05 ns Phosphorus, total 1 35% -- -- 0.026 -- -- ns TKN 1 167% -- -- 0.98 -- -- ns Trace Elements Fluoride 7 4% 22% 7% 0.01 0.6 0.1 ns Iron 1 30% -- -- 0.08 -- -- ns 171 -- -- ns Radiochemical Constituents Radon-2221 1 44% -- -- All units are mg/l except as noted with certain physical parameters 1 = Split conducted between Lucas Laboratory (LSP-5) and Bolin Laboratory (LSP-6) ns = No significant (p # 0.05) difference between labs Data Evaluation 72 SC/TDS - The SC and TDS concentrations measured by contract laboratories were significantly correlated as were field-SC and TDS concentrations (regression analysis, p # 0.01). Typically, the TDS concentration in mg/l should be from 0.55 to 0.75 times the SC in FS/cm for groundwater up to several thousand mg/l32. Groundwater in which the ions are mostly bicarbonate and chloride will have a factor near the lower end of this range and groundwater high in sulfate may reach or even exceed the upper end 31. The relationship of TDS to SC becomes indefinite for groundwater both with very high and low concentrations of dissolved solids31. Hardness - Concentrations of laboratory-measured and calculated values were significantly correlated (regression analysis, p # 0.01). Hardness concentrations were calculated using the following formula: [(Ca x 2.497) + (Mg x 4.118)]. SC - The SC measured in the field using a Hydrolab at the time of sampling was significantly correlated with the SC measured by contract laboratories (regression analysis, p # 0.01). pH - The pH value is closely related to the environment of the water and is likely to be altered by sampling and storage31. Even so, the pH values measured in the field using a Hydrolab at the time of sampling were significantly correlated with laboratory pH values (regression analysis, p # 0.01). Groundwater Temperature/Groundwater Depth Groundwater temperature measured in the field was compared to groundwater depth to examine the relationship that exists between temperature and depth. Groundwater temperature should increase with depth, approximately 3 degrees Celsius with every 100 meters or 328 feet13. Groundwater temperature and well depth were significantly correlated (regression analysis, p # 0.01). The analytical work conducted for this study was considered valid based on the quality control samples and the QA/QC correlations. Statistical Considerations Various methods were used to complete the statistical analyses for the groundwater quality data of this study. All statistical tests were conducted on a personal computer using SYSTAT software. Data Normality: Initially, data associated with 21 constituents were tested for both non-transformed and log-transformed normality using the KolmogorovSmirnov one-sample test with the Lilliefors option15. Results of this test using non-transformed data revealed that only bicarbonate was normally distributed. The distribution of many groundwater quality parameters is often not Gaussian or normal, but skewed to the right. The results of the log-transformed test revealed that 7of the 21 log-transformed constituents were normallydistributed. In summary, non-transformed data are overwhelmingly not normally-distributed while roughly one-third of the log-transformed constituents are normally-distributed. The most recent and comprehensive statistical references specifically recommend the use of nonparametric tests when the non-normality assumption is violated 29. Various aspects of LSP groundwater quality were analyzed using the following statistical methods: Spatial Relationships: The non-parametric KruskalWallis test was applied to investigate the hypothesis that constituent concentrations from groundwater sites in different groundwater aquifers, geologic types, and/or watersheds of the LSP were the same. The Kruskal-Wallis test uses the differences, but also incorporates information about the magnitude of each difference. The null hypothesis of identical median values for all data sets within each test was rejected if the probability of obtaining identical medians by chance was less than or equal to 0.05. Comparisons conducted using the Kruskal-Wallis test include aquifers (floodplain, basin-fill, confined basin-fill, and hardrock), basin watersheds (Redington, Mammoth, Winkleman, and Kearny), and geologic (alluvium, granite rock, metamorphic rock, volcanic rock, and sedimentary rock). If the null hypothesis was rejected for any of the tests conducted, the Tukey method of multiple comparisons on the ranks of the data was applied. The Tukey test identified significant differences between constituent concentrations when compared to each possibility within each of the four tests 29. Both the Kruskal-Wallis and Tukey tests are not valid for data sets with greater than 50 percent of the Data Evaluation 73 constituent concentrations below the MRL29. Consequently, the Kruskal-Wallis test was not calculated for trace parameters such as antimony, arsenic, barium, beryllium, boron, cadmium, chromium, copper, iron, lead, manganese, mercury, nickel, selenium, silver, thallium, zinc as well as phenolphthalein alkalinity, carbonate, nitrite, ammonia, and TKN. Highlights of these statistical tests are summarized in the groundwater quality section. Groundwater Level Relationships: Simple regression was used to examine relationships between constituent concentrations and groundwater depth. Groundwater depth was determined using a sounder in the field when possible or obtained from well driller’s logs. Comparisons were conducted using three distinct methods: < < < Linear Model [P] = md + b [P] vs d Exponential Model [P]d = [P]d=0e-rd ln[P] vs d Biphasic Model [P] = a(d)-b ln[P] vs lnd The null hypothesis of no association between variables was rejected if the probability of obtaining the correlation by chance was less than or equal to 0.05. Significant correlations between the data sets are summarized in the groundwater quality section. Correlation Between Constituent Concentrations: In order to assess the strength of association between constituents, their various concentrations were compared to each other using the Pearson Correlation Coefficient test. quality section. Time-Trend Analysis: Changes in constituent concentrations over time were examined utilizing data collected from the same wells by the USGS in 1950/1951 and ADEQ in 1999/200028. The Wilcoxon rank-sum statistic, which is a nonparametric measure of association between two independent sets of data, was used to determine any significant changes in constituent concentrations between the different time periods. The Wilcoxon test was used to test the null hypothesis that constituent concentrations collected in 1950/1951 were the same as constituent concentrations collected during 1999/2000. The null hypothesis of identical median values for each data set was rejected if the probability of obtaining identical medians by chance was less or equal to 0.05. The Wilcoxon test is not valid for data sets with greater than 50 percent of the constituent concentrations below the MRL29. Consequently, the Wilcoxon test was not calculated for trace parameters such as antimony, arsenic, barium, beryllium, cadmium, chromium, copper, iron, lead, manganese, mercury, nickel, selenium, silver, thallium, as well as phenolphthalein alkalinity, nitrite, ammonia, and total phosphorus. Highlights from these statistical tests are summarized in the groundwater quality section. The Pearson correlation coefficient varies between -1 and +1, with a value of +1 indicating that a variable can be predicted perfectly by a positive linear function of the other, and vice versa. A value of -1 indicates a perfect inverse or negative relationship. The results of the Pearson Correlation Coefficient test were then subjected to a probability test to determine which of the individual pair wise correlations were significant. The Pearson test is not valid for data sets with greater than 50 percent of the constituent concentrations below the MRL29. Consequently, Pearson Correlation Coefficients were not calculated for trace parameters such as antimony, arsenic, barium, beryllium, boron, cadmium, chromium, copper, iron, lead, manganese, mercury, nickel, selenium, silver, thallium, zinc as well as phenolphthalein alkalinity, carbonate, nitrite, ammonia, and TKN. Significant highlights from this statistical test are summarized in the groundwater Data Evaluation 74