Department FACT SHEET of Environmental Quality

Janice K. Brewer, Governor • Henry R. Darwin, Director Publication Number: FS 13-18

Ambient Groundwater Quality of the Basin: A 2002-2012 Baseline Study – November 2013

Introduction A baseline groundwater quality study of the Tonto Creek basin was conducted from 2002 to 2012 by the Arizona Depart- ment of Environmental Quality (ADEQ) Ambient Groundwater Monitoring Pro- gram. ADEQ carried out this task pursuant to Arizona Revised Statutes §49-225 that mandates ongoing monitoring of waters of the state including its aquifers. The fact sheet is a synopsis of the ADEQ Open File Report 13-04.1 Located 40 miles northeast of Phoenix, the Tonto Creek groundwater basin contains approximately 955 square miles within Gila County (Map 1).2 More than Map 1 – Sample sites in 97 percent of the basin consists of federal the Tonto Creek basin are land managed by the U.S. Forest Service color-coded according to their water quality status: No . Low-intensity Water Quality Exceedences, livestock grazing and recreational activi- Secondary MCLs Exceedences, Primary MCL Exceedances, and Primary and Secondary MCL (Map by Douglas Towne) Exceedances.

ties are the predominant forest uses with portion of the basin. Other perennial the remaining private lands being used streams include Houston, Christopher, for residential homes or ranches. Small and Greenback creeks. communities include Gisela, Kohl’s Ranch, Punkin Center, Rye, and the Town of Star Groundwater occurs in four geologic for- Valley; the Town of Payson is located just mations: stream alluvium, basin-fill sedi- to the northwest of the basin. ments, Paleozoic sedimentary rocks, and Precambrian igneous, metamorphic, and sedimentary rocks.2 The primary aquifer is Hydrology composed of unconsolidated sediments The basin is drained by Tonto Creek, a pe- including stream alluvium (along Tonto rennial tributary to the , which Creek and its major tributaries) and basin flows from north to south discharging fill that underlie much of the basin south an average of 105,000 acre-feet annually of Rye. The basin fill is divided into two into (Figure 1).2 parts: a lower and an upper unit with the latter consisting of coarse-grained and Figure 1 – Tonto Creek, shown upgradient of Gisela, Major tributaries to Tonto Creek include has perennial flow throughout the basin which it exits Rye Creek to the west and Spring and fine-grained depositional components. just before emptying into Theodore Roosevelt Lake in The coarse-grained depositional com- 2 Haigler creeks flowing from the eastern the Salt River basin. ponent is moderately permeable but is OUR MISSION To protect and enhance public health and the environment in Arizona. OUR VISION To lead Arizona and the nation in protecting the environment and improving the quality of life for the people of our FACT SHEET state. Arizona Department of Environmental Quality generally located above the water table. ownership. Most wells are low-yield procedures were not significant based The fine-grained depositional compo- domestic and stock wells, though some on quality assurance/quality control nent is largely impermeable, although irrigation wells in the stream alluvium PRINCIPLESevaluations. AND VALUES thin sand layers yield small amounts of along the lower reaches of Tonto Creek We advocate for Arizona’s environment. 3, 4 3, 4 We adhere to the highest standards of water to wells near Punkin Center. produce up to 2,500 gpm. There are technicalWater professionalism. Quality Sampling Results an estimated 170 springs in the basin.2 We commit to the highest standards Paleozoic sedimentary rocks along the of ethical behavior. Groundwater is used for all public water We Groundwaterare committed to openness, sample honesty results were can also produce abun- and transparency. supply and domestic uses and most We comparedfoster relationships builtwith on r espect,the Safe Drinking Water dant water from a limestone aquifer courtesy and service. irrigation and stock uses in the basin. We Actvalue c(SDW)reativity, innovation health and aesthetics-based whose source is the C-aquifer in the Small diversions on Tonto Creek and andwater performance. quality standards.5 adjacent Little River basin. We turn challenges into opportunities. its tributaries supply surface water for We value our employees This limestone aquifer is the source irrigation use, such as near Gisela. andPublic work as a team. drinking water systems must of many of the basin’s 10 springs that meet health-based, water quality stan- have discharges exceeding 10 gallons dards, called Primary Maximum Con- per minute (gpm) including the larg- Methods of Investigation taminant Levels (MCLs), when supplying est, Tonto Spring, which flows at 1,291 To characterize regional groundwater water to their customers. These enforce- gpm (Figure 2). Precambrian igneous, quality, samples were collected from 31 able standards are based on a lifetime metamorphic, and sedimentary rocks in (70 years) consumption of two liters sites (20 wells and 11 springs). Of the 20 5 the basin’s margins sometimes produce wells, 17 used submersible pumps, two per day. Primary MCLs were exceeded limited groundwater. 2, 3, 4 at eight of the 31 sites (26 percent). were windmills (Figure 3), and one was a turbine pump. Samples for inorganic Constituents exceeding Primary MCLs Groundwater flows generally from north include arsenic (six sites), gross alpha to south. Depth to groundwater varies constituents were collected from all 31 sites while at selected sites, radionu- (two sites), and one site each for nitrate, significantly across the basin from just radium-226+228, and uranium. 40 feet below land surface (bls) along clide (19 sites), oxygen and deuterium stretches of the lower Tonto Creek to isotopes (10 sites), volatile organic com- Public drinking water systems are more than 100 feet bls in most other pounds or VOCs (eight sites), and radon encouraged by the SDW to meet areas of the basin. 2 (five sites) samples were collected. unenforceable, aesthetics-based water Sampling protocol followed the ADEQ quality guidelines, called Secondary Groundwater development in the basin Quality Assurance Project Plan (see MCLs, when supplying water to their is limited because of its rugged topog- www.azdeq.gov/function/programs/lab/). customers. Water exceeding Second- raphy and predominant federal land The effects of sampling equipment and ary MCLs may be unpleasant to drink and/or create unwanted cosmetic or laundry effects but is not considered a health concern.5 Secondary MCLs were exceeded at four of the 31 sites (13 percent). Constituents exceeding Secondary MCLs include fluoride (one site), manganese (one site), and total dissolved solids or TDS (three sites). Radon is a naturally occurring, inter- mediate breakdown product from the radioactive decay of uranium-238 to lead-206. Of the five sites sampled for radon, none exceeded the proposed 4,000 picocuries per liter (pCi/L) stan- dard that would apply if Arizona estab- lishes a multimedia program to address the health risks from radon in indoor air.5 Five sites (100 percent) exceeded the proposed 300 pCi/L standard that would apply if Arizona does not develop Figure 3 – Clover Well consists of a windmill, storage a multimedia program.5 There were no Figure 2 – Former ADEQ employee Susan Determann tank, and pipelines transporting water to troughs for detections of any of the 34 VOCs in the collects a sample from Tonto Spring just below the livestock use. The windmill is located west of Rye at Mogollon Rim. Tonto is the largest spring in the basin the base of the overlooking the eight samples. with an average discharge of 1,291 gpm. 2 Tonto Creek basin. OUR MISSION To protect and enhance public health and the environment in Arizona. OUR VISION To lead Arizona and the nation in protecting the environment and improving the quality of life for the people of our FACT SHEET state. Arizona Department of Environmental Quality

Groundwater Composition divided into natural background (19 Groundwater Patterns sites at <0.2 mg/L) may or may not Groundwater quality varied throughout Groundwater constituent concentra- indicate human influence (11 sites PRINCIPLES AND VALUES the basin in the following ways: tions were influenced by geology. Con- at 0.2 – 3.0 mg/L) ), and probably We advocate for Arizona’s environment. result from human activities (one We stituentsadhere to the highest such standards as oftemperature, Specific • Groundwater chemistry in the basin technical professionalism. site > 10 mg/L).6 We Conductivitycommit to the highest standards (SC)-field, SC-lab, TDS is predominantly calcium-bicarbon- of ethical behavior. We (Figureare committed 5), to openness, sodium, honesty potassium, chloride, ate or mixed-bicarbonate (Figure 4). • Most trace elements such as alumi- andstrontium, transparency. oxygen-18, and deuterium We foster relationships built on respect, • Levels of pH measured in the field num, antimony, beryllium, boron, courtesyhad and significantly service. higher constituent con- cadmium, chromium, iron, lead, We value creativity, innovation were slightly alkaline (above seven andcentrations performance. at sites in unconsolidated manganese, mercury, nickel, sele- Wesediment turn challenges into than opportunities. at sites in consolidated standard units ranging from 7.20 – We value our employees 7.90 su) except for six sample sites nium, silver, and thallium were rarely androcks work as a (Kruskal-Wallis team. test, p ≤ 0.05). Con- that were slightly acidic (below detected. Only arsenic, barium, stituents such as temperature, SC-field, seven standard units ranging from copper, fluoride, strontium, and zinc SC-lab, TDS, sodium, potassium, chloride 6.98 - 6.80 su). were detected at more than (Figure 6), strontium, oxygen-18, and one-third of the sites. gross alpha generally had significantly • Total dissolved solids (TDS) concen- greater concentrations in sites located Oxygen and deuterium isotope values trations were all considered fresh in stream alluvium than in basin fill, at most sites appear to be a product of (below 999 mg/L). and consolidated or sedimentary rock the elevation at which the sample sites (Kruskal-Wallis test, p ≤ 0.05). • Hardness concentrations were were located. The two samples that soft (below 75 mg/L) at one site, experienced the most evaporation were moderately hard (75 - 150 mg/L) at characterized as enriched and were six sites, hard (151 - 300 mg/L) at 17 collected from shallow wells located sites, very hard (301 – 600 mg/L) at along the lower reach of Tonto Creek. seven sites. The remaining eight samples were more depleted, suggesting the water from • Nitrate (as nitrogen) concentrations these higher elevation sites was subject at most sites may have been influ- to much less evaporation.7 Consolidated enced by human activities and were Unonsolidated

Figure 5 – Samples collected from sites in unconsolidated sediment have significantly higher TDS concentrations than samples collected from sites in consolidated rock that are often upgradient (Kruskal-Wallis, p ≤ 0.05). Factors such as low rock solubility, limited carbon dioxide, and few human impacts influence this trend.8 Alluvium Basin fill Other Rock Sedimentary

Figure 6 – Samples collected from sites in stream alluvium have significantly higher chloride concentrations than Figure 4 – Groundwater samples are predominantly a calcium-bicarbonate or mixed-bicarbonate chemistry sample sites collected from basin-fill sediments, sedimen- which is reflective of young groundwater that has been recently recharged.8 The exception was one sample with tary or other consolidated rock (Kruskal-Wallis, p ≤ 0.05). a sodium-bicarbonate chemistry that appears to produce water from the fine-grained depositional component Downgradient areas often evolve towards sodium-chloride chemistry as TDS concentrations increase. 8 of the upper unit of the basin-fill aquifer. OUR MISSION To protect and enhance public health and the environment in Arizona. OUR VISION To lead Arizona and the nation in protecting the environment and improving the quality of life for the people of our FACT SHEET state. Arizona Department of Environmental Quality

Discussion samples collected in the southern por- 5 U.S. Environmental Protection Agency tion of Tonto Creek basin however, had website, www.epa.gov/water- Groundwater in the Tonto Creek basin arsenic concentrations exceeding water PRINCIPLESscience/criteria/humanhealth/, AND VALUES accessed is generally suitable for drinking water quality standards. An oxidizing environ- We advocate09/19/13. for Arizona’s environment. uses based on results from this ADEQ We adhere to the highest standards of ment and lithology appear to be factors technical professionalism. 6 Madison, R.J., and Brunett, J.O., 1984, study and earlier research by the U.S. in the five Primary MCL exceedances We commit to the highest standards 3,4 of ethOverviewical behavior. of the occurrence of nitrate Geological Survey. Samples were that narrowly exceeded the 0.01 mg/L We are committed to openness, honesty and transparency. predominantly of calcium or mixed- 8 in ground water of the , in arsenic standard. We foster relationships built on respect, bicarbonate chemistry which is charac- courtesyNational and service. Water Summary 1984-Water We value creativity, innovation teristic of recently recharged ground- Aquifer residence time appears to cause and Qualityperformance. Issues: U.S. Geological Survey water having low concentrations of the basin’s highest arsenic concentra- We turnWater challenges Supply into opportunities. Paper 2275, pp. 93-105 We value our employees TDS, nutrients, and trace elements.8 The tion, which was found in a split sample and work as a team. 7 Earman, Sam, et al, 2003, An investiga- limestone aquifer along the Mogollon collected from a well located near Pun- tion of the properties of the San Ber- Rim, in particular, produces especially kin Center.8 The sample also had unusu- nardino groundwater basin, Arizona and high-quality water. al sodium-bicarbonate chemistry and aesthetics-based water quality exceed- , : Hydrology program, New Samples from 22 of the 31 sites (71 per- ances of fluoride and TDS. Although no Mexico Institute of Mining and 5 cent) met all water quality standards. Of isotope sample was collected from the Technology, 283 p. the remaining nine sample sites, the con- site, the sample’s water chemistry make 8 Robertson, F.N., 1991, Geochemistry of stituents that most commonly impacted it likely the well is producing water that ground water in alluvial basins of Arizona the acceptability of water for drinking was recharged long ago. The same phe- and adjacent parts of , New purposes were arsenic and, to a lesser nomena were detailed in an earlier U.S. Mexico, and : U.S. Geological degree, radionuclides and nitrate. These Geological Survey study when a sample Survey Professional Paper 1406-C, 94 p. are three of the four constituents that collected from a well in the same gen- most commonly exceed health-based eral area also had a sodium chemistry 9 Towne, D.C. and Jones, J., 2011, Ground- 9 water quality standards in Arizona. and exceeded water quality standards water quality in Arizona: A 15-year over- 4,5 view of the ADEQ ambient groundwater Gross alpha exceeded health-based, for arsenic, fluoride, and TDS. Both quality program (1995-2009): Arizona water quality standards in radionuclide wells appear to be tapping groundwa- Department of Environmental Quality samples collected from two of 19 sites ter from the fine-grained depositional Open File Report 11-04, 44 p. (11 percent). The two exceedances component of the upper part of the were located at sites in or near granitic basin fill, which should be avoided as a 10 Lowry, J.D. and Lowry, S.B., 1988, “Radio- geology which is often associated with drinking water source in the basin. nuclides in Drinking Waters,” in American elevated radionuclide concentrations References Cited Water Works Association Journal, 80 in groundwater.10 This correlation is not (July), pp. 50-64. strong however, since other radionu- 1 11 clide samples collected from sites in Towne, D.C., 2013, Ambient groundwater Bedient, P.B. Rifai, H.S. and Newell, C.J., granitic geology did not exceed water quality of the Tonto Creek basin: A 2002 - 1994, Ground Water Contamination: quality standards. 2012 baseline study: Arizona Department Transport and Remediation: Englewood of Environmental Quality Open File Report Cliffs, N.J., Prentice-Hall, Inc. Nitrate exceeded health-based, water 13-04, 49 p. quality standards in duplicate samples 2 collected from a well located at a Arizona Department of Water Resources remote ranch surrounded by U.S. Forest website, www.azwater.gov/azdwr/de- Service lands north of Punkin Center fault.aspx, accessed 09/26/13. along Tonto Creek. The sample also had 3 Dennis, E.E., 1981, Maps showing the study’s highest TDS and chloride ground-water conditions in the Tonto For More Information Contact: concentrations. The elevated nitrate Basin area, Gila County, Arizona—1979: Douglas C. Towne concentration is likely due to septic sys- U.S. Geological Survey Water Resources Hydrologist, ADEQ Monitoring Unit tem discharge as this also elevates TDS Investigations 82-116, 1 sheet, scale, 1110 W. Washington St. #5330D and chloride concentrations.11 1:250,000. Phoenix, AZ 85007 Arsenic exceedances in the Tonto Creek 4 Schumann, H.H. and Thomsen, B.W., email: [email protected] basin all occurred in samples collected 1972, Hydrologic regimen of Lower Tonto www.azdeq.gov/environ/water/ from six sites located in unconsolidated Creek Basin, Gila County, Arizona: A recon- assessment/ambient.html#studies sediment (basin fill or stream alluvium) naissance study: Arizona Water Commis- Publication Number: FS-13-18 downgradient from Gisela. Not all of the sion Bulletin #3, 39 p.