U.S. Department of the Interior

U.S. Geological Survey

Open-File Report 2013–1162

Prepared in cooperation with the Hopi Tribe

Quality, Isotopes, and Radiochemistry of Water Sampled from 

the Upper Moenkopi Village Water-Supply Wells, Coconino 

County, Arizona
FRONT COVER

Overview of Upper and Lower Moenkopi Villages from the south looking north across Moenkopi Wash. Photograph 

taken by D.J. Bills, Fall 2008.
Quality, Isotopes, and Radiochemistry of 

Water Sampled from the Upper Moenkopi 

Village Water-Supply Wells, Coconino 

County, Arizona

By Robert L. Carruth, Kimberly Beisner, and Greg Smith

Prepared in cooperation with the Hopi Tribe

Open-File Report 2013–1162

U.S. Department of the Interior

U.S. Geological Survey
U.S. Department of the Interior

SALLY JEWELL, Secretary

U.S. Geological Survey

Suzette M. Kimball, Acting Director

U.S. Geological Survey, Reston, Virginia: 2013

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Suggested citation:

Carruth, R.L., Beisner, Kimberly, and Smith, Greg, 2013, Qualilty, isotopes, and radiochemistry of water sampled from 

the Upper Moenkopi Village water-supply wells, Coconino County, Arizona: U.S. Geological Survey Open-File Report 

2013-1162, 18 p. 
 iii

Contents

Abstract...........................................................................................................................................................1

Introduction.....................................................................................................................................................1

Purpose and Scope ..............................................................................................................................2

Previous Investigations........................................................................................................................2

Description of Study Area ...................................................................................................................2

Upper Moenkopi Village Water-Supply Wells ........................................................................2

Methods of Study...........................................................................................................................................6

Depth-Dependent Sampling and Well-Bore Flow...........................................................................6

Water-Chemistry Data Collection and Analysis...............................................................................7

Results of Water-Quality, Isotope, and Radiochemistry Analysis .........................................................7

Water Quality.........................................................................................................................................7

Field Parameters and Inorganics..............................................................................................7

Nutrients......................................................................................................................................13

Trace Elements...........................................................................................................................14

Isotopes................................................................................................................................................14

Radiochemistry....................................................................................................................................16

Summary .......................................................................................................................................................16

Acknowledgments.......................................................................................................................................17

References....................................................................................................................................................17

Figures

1. Map showing location of the study area in northeastern Arizona ................................................3

2. Map showing Upper Moenkopi water-supply wells near the Moenkopi Villages, 

Coconino County, Arizona ...........................................................................................................4

3. Generalized stratigraphic section for the area near the Upper Moenkopi Village 

water-supply wells, Coconino County, Arizona .......................................................................5

4. Trilinear diagram showing relative compositions of groundwater samples collected 

from the Upper Moenkopi Village water-supply wells in Coconino County, Arizona......12

5. Graph showing oxygen-18 (18O) and deuterium (2H) data from the Upper Moenkopi 

Village water-supply wells and comparison with other water sources in the 

surrounding area, Coconino County, Arizona ........................................................................15

Tables

1. Construction, water-level, and pumping data from the Upper Moenkopi Village 

water-supply wells, Coconino County, Arizona .......................................................................5

2. Water quality data from Upper Moenkopi Village water-supply wells, Coconino 

County, Arizona .............................................................................................................................8

3. Carbon-14 radioisotope data used to estimate ages of groundwater sampled from 

the upper Moenkopi Village water-supply wells, Coconino County, Arizona...................14
iv 

Inch/Pound to SI

Multiply By To obtain

Length

inch (in.) 2.54 centimeter (cm)

inch (in.) 25.4 millimeter (mm)

foot (ft) 0.3048 meter (m)

mile (mi) 1.609 kilometer (km)

Volume

gallon (gal) 3.785 liter (L) 

gallon (gal) 0.003785 cubic meter (m3) 

gallon (gal) 3.785 cubic decimeter (dm3) 

Flow rate

gallon per day (gal/d) 0.003785 cubic meter per day (m3/d)

gallon per minute (gal/min) 3.785 liter per minute (L/min)

Radioactivity

picocurie per liter (pCi/L) 0.037 becquerel per liter (Bq/L) 

SI to Inch/Pound

Multiply By To obtain

millimeter (mm) 0.03937 inch (in.)

Volume

liter (L) 1.057 quart (qt)

liter (L) 0.2642 gallon (gal)

Temperature in degrees Celsius (°C) may be converted to degrees Fahrenheit (°F) as follows: °F=(1.8×°C)+32

Vertical coordinate information is referenced to the North American Vertical Datum of 1988 (NAVD 88).

Horizontal coordinate information is referenced to the insert North American Datum of 1983 (NAD 83).

Altitude, as used in this report, refers to distance above the vertical datum.

Specific conductance is given in microsiemens per centimeter at 25 degrees Celsius (μS/cm at 25 °C).

Concentrations of chemical constituents in water are given either in milligrams per liter (mg/L) or micrograms per liter (μg/L).

Conversion Factors
Quality, Isotopes, and Radiochemistry of Water Sampled 

from the Upper Moenkopi Village Water-Supply Wells, 

Coconino County, Arizona

By Robert L. Carruth, Kimberly Beisner, and Greg Smith

Abstract

The Hopi Tribe Water Resources Program has granted 

contracts for studies to evaluate water supply conditions for 

the Moenkopi villages in Coconino County, Arizona. The 

Moenkopi villages include Upper Moenkopi Village and 

the village of Lower Moencopi, both on the Hopi Indian 

Reservation south of the Navajo community of Tuba City. 

These investigations have determined that water supplies 

are limited and vulnerable to several potential sources of 

contamination, including the Tuba City Landfill and a former 

uranium processing facility known as the Rare Metals Mill. 

Studies are ongoing to determine if uranium and other metals 

in groundwater beneath the landfill are greater than regional 

groundwater concentrations.

The source of water supply for the Upper Moenkopi 

Village is three public-supply wells. The wells are referred to 

as MSW-1, MSW-2, and MSW-3 and all three wells obtain 

water from the regionally extensive N aquifer. The N aquifer 

is the principal aquifer in this region of northern Arizona and 

consists of thick beds of sandstone between less permeable 

layers of siltstone and mudstone. The relatively fine-grained 

character of the N aquifer inhibits rapid movement of water 

and large yields to wells. In recent years, water levels have 

declined in the three public-supply wells, causing concern that 

the current water supply will not be able to accommodate peak 

demand and allow for residential and economic growth. 

Analyses of major ions, nutrients, selected trace metals, 

stable and radioactive isotopes, and radiochemistry were 

performed on the groundwater samples from the three publicsupply wells to describe general water-quality conditions and 

groundwater ages in and immediately surrounding the Upper 

Moenkopi Village area. None of the water samples collected 

from the public-supply wells exceeded the U.S. Environmental 

Protection Agency primary drinking water standards. 

The ratios of the major dissolved ions from the samples 

collected from MSW-1 and MSW-2 indicate water with a 

major ion composition of calcium and sulfate. There is no 

significant vertical distribution of ion concentrations in the 

samples collected from the upper and lower portion of the 

water column within the two wells. The samples collected at 

MSW-3 are higher in sodium and lower in calcium than the 

samples collected from MSW-1 and MSW-2, and contain a 

similar sulfate-ion percentage. There is a vertical distribution 

of ion concentrations in the samples collected from the upper 

and lower portion of the water column in MSW-3. 

Groundwater samples from the three water-supply wells 

analyzed for oxygen-18 and deuterium stable isotopes plot on 

a local water line that is approximately parallel to the global 

meteoric water line. Tritium concentrations in samples from 

MSW-1 and MSW-3 were equal to or less than laboratory 

detection limits and were interpreted to contain no modern 

(post-1952) water. Tritium concentration in a sample from 

the top of the water column at MSW-2 was 0.41 tritium units, 

indicating that the composition is primarily pre-bomb (pre1952) water, but may contain a small fraction of post-bomb 

modern water. 

The calculated carbon-14 ages of groundwater in 

MSW-1 and MSW-2, both completed about 140 feet into 

the Navajo Sandstone, are about 3,000 years before present. 

The calculated carbon-14 age of groundwater in MSW-3, 

completed about 240 feet into the Kayenta Formation–Navajo 

Sandstone transition zone is about 5,000 years before present 

in the upper portion of the water column and about 8,500 

years before present in the lower portion of the water column. 

The gross alpha radioactivity of samples collected from the 

three water-supply wells ranged from 5.1 to 9.8 picocuries per 

liter—less than the U.S. Environmental Protection Agency 

primary drinking water standard of 15 picocuries per liter. 

The gross beta radioactivity of samples collected from the 

wells ranged from 0.9 to 2.8 picocuries per liter and are 

not considered elevated relative to the U.S. Environmental 

Protection Agency primary drinking water standard. 

Introduction

In 2010, the Hopi Tribe and the Indian Health Service 

(IHS) requested assistance from the U.S. Geological Survey 

(USGS) in evaluating the source of water to the public 

water supply and water quality as it relates to the possible 

migration of contaminated groundwater to supply wells in the 
2 Quality, Isotopes, and Radiochemistry of Water Sampled from the Upper Moenkopi Village Water-Supply Wells

Upper Moenkopi Village area. Previous investigations have 

determined that local water supplies are limited and vulnerable 

to potential sources of contamination, including the Tuba 

City Landfill and a former uranium processing facility known 

as the Rare Metals Mill. Studies are ongoing to determine if 

uranium and other metals in groundwater beneath the landfill 

are greater than regional groundwater concentrations and if a 

flow path exists between the Tuba City Landfill area and the 

village water-supply wells.

This report documents the collection and analyses of 

depth-dependent water samples under pumping conditions 

from the three public water-supply wells in Upper Moenkopi 

Village, referred to as MSW-1, MSW-2, and MSW-3 (figs. 1 

and 2). Samples from these wells were analyzed for a range 

of chemical and isotopic constituents including major ions, 

nutrients, trace elements, stable and radioactive isotopes, and 

radiochemistry. These data were collected to evaluate the 

quality of water that makes up the municipal water supply for 

Upper Moenkopi Village. The analytical results were reviewed 

to determine if degradation of water quality has occurred. 

The depth-dependent water-quality samples were analyzed 

to determine if any vertical distribution of water quality or 

contaminants exists within the Navajo Sandstone and Kayenta 

Formation (stratigraphic units of the N aquifer penetrated by 

the water-supply wells). Additionally, an attempt was made to 

collect well-bore flow data from the three wells to determine 

the flow distribution into the wells from the surrounding 

aquifer; however, limitations caused by the well construction 

and the relatively low permeability of the surrounding aquifer 

prohibited collection of well-bore flow data.

Purpose and Scope

The purpose of this report is to assess the source, 

distribution of flow, and quality of water from each of the 

three public water-supply wells under pumping conditions. 

Data collected during this study can be used to (1) assess the 

quality of the existing municipal water supply, (2) provide a 

baseline for comparison with future water-quality monitoring, 

(3) evaluate management options to address possible 

contaminant sources, and (4) provide information to design 

and locate future water-supply wells.

Previous Investigations

Previous investigations of the N aquifer have evaluated 

water availability for local needs. A study by Cooleyand 

others (1969) provided the regional hydrogeologic 

characterization of the N aquifer in the Moenkopi and Tuba 

City area. Additional investigations by the USGS have added 

to this characterization over the years (Levings and Farrar, 

1977; Farrar, 1980; Eychaner, 1983; Lopes and Hoffmann, 

1997; Hoffmann and others, 2006; Macy, 2010; Macy and 

others, 2012). Additional studies have characterized the 

aquifer at the scale of individual test wells (Tetra Tech EM 

Inc., 2004; Carruth and Bills, 2012). Local geology and 

geologic structure also has been investigated (Macy, 2012) and 

is important because it affects the occurrence and movement 

of groundwater and movement of potential contaminants in 

the area. Additionally, geologic maps and cross sections, and 

geochemical analyses of rock, sediment, and groundwater 

have been done in the vicinity of the Tuba City landfill 

(Johnson and Wirt, 2009; Otton and others, 2009).

Description of Study Area

Upper Moenkopi Village is on the Hopi Indian 

Reservation south of the Navajo Nation community of Tuba 

City and west of Pasture Canyon on the southern side of U.S. 

Highway 160, approximately 80 mi northeast of Flagstaff, 

Arizona (figs. 1 and 2). Upper Moenkopi Village is one of 12 

villages that make up the communities of the Hopi Nation in 

northeastern Arizona. Exposed rocks in the study area include 

the Jurassic Navajo Sandstone, and eolian sand and dunes 

eroded from the Navajo Sandstone. The surface deposits are 

covered with sparse desert grasses, cactus, and sagebrush. 

The regional dip of rock units at the surface is about 2 degrees 

northeast toward the Tuba City syncline, whose axis is about 

5miles from the study area (Cooley and others, 1969). 

Upper Moenkopi Village Water-Supply Wells

Water for the Upper Moenkopi Village is supplied from 

three wells (MSW-1, MSW-2, and MSW-3) completed in the 

regionally extensive N aquifer, the principal aquifer in this 

region of northern Arizona. The N aquifer is a moderately 

productive groundwater-flow system that underlies most of 

the Navajo and Hopi Indian Reservations in northern Arizona. 

The Moenkopi Villages, however, are at the western edge 

of the N aquifer where rock units of the groundwater-flow 

system are thinned by exposure and erosion or locally pinch 

out. The N aquifer is composed of thick beds of sandstone 

between less permeable layers of siltstone and mudstone. The 

relatively fine-grained character of the N aquifer inhibits rapid 

movement of water and large yields to wells. In recent years, 

water levels have declined in the three public-supply wells, 

causing concern that the current water supply will not be able 

to accommodate peak demand and allow for residential and 

economic growth. 

The wells generally are aligned east-west along the 

southern side of, and approximately parallel to, Highway 160 

(fig. 2). MSW-1 (easternmost well) and MSW-2 (westernmost 

well) are separated by a distance of approximately 500 ft. 

MSW-3 is between MSW-1 and MSW-2, but closer to MSW1. MSW-1 and MSW-2 were constructed in 1977 and 1982, 

respectively. Both wells were originally completed to about 

140 ft below land surface. MSW-3 was constructed in 1991 

to a depth of 280 ft below land surface. Construction details 

for the wells (including the screened intervals and depths to 

the pumps) were provided by the Hope Tribe Water Resources 
Introduction 3

Shonto 

Page 

111°30' 111° 30' 110° 109°30'

Ganado 

Chinle Valley

Echo

Cliffs

Na vajo Creek

Little

Co lorado Ri ver

Din

bi

ne

to

Phoenix 

Flagstaff 

NATION

NAVAJO

ca

Polac

sh a W sh

a W

sh a W

bi ai Or

sh a W

Mine

Moenkopi

Coal

sh a W

Howell

Mesa

TRIBAL

HOPI

LANDS

Coal-lease

Area

NAVAJO

NATION

NAVAJO CO. 

NAVAJO CO. 

COCONINO CO. 

APACHE CO. 

0

0

25 KILOMETERS

MAP AREA

25 MILES

Tsegi

Betatakin

Red Lake 

Cow Springs 

Rocky 

Ridge 

Keams

Canyon 

Forest Lake 

Kitsillie 

Rough Rock 

Hard Rock Pinon ~ 

Dennehotso

Chilchinbito 

Goldtooth 

Shonto 

Junction 

Bacavi 

Kykotsmovi 

Hotevilla 

Polacca 

Low Mountain 

Base from U.S. Geological Survey digital data, 1:100,000, 1980

Lambert Conformal Conic projection, 

Standard parallels 29°30' and 45°30',

central meridian −111°30' 

La

C hsa W hi e nl

guna Creek

ARI Z O N A

77

191

160

163

160

Tuba City

89

Shipaulovi 

264

87

30'

36°

35°30'

37°

Kayenta

Former

rare

metals

mill

Moenkopi

Villages

Modified from Brown and Eychaner, 1988

98

UTAH

ARIZONA

NAVAJO

IND. RES.

Chinle 

Mishongnovi 

264

Colorado

River Little Colorado River

Second Mesa 

Shungopavi 

Figure 1. Map showing location of the study area in 

northeastern Arizona. Photograph shows pulling pump at 

well MSW-2.
4 Quality, Isotopes, and Radiochemistry of Water Sampled from the Upper Moenkopi Village Water-Supply Wells

264

160

Moenkopi villages 

Base from U.S. Department of Agriculture, National Agriculture Imagery Program, 

Universal Transverse Mercator Projection, North American Datum 1983, Zone 12 North

Pasture

Canyon

Tuba City 

landfill

(administratively

closed)

Tuba City 

landfill

new cell

THE NAVAJO NATION

HOPI TRIBAL LANDS

Moenkopi water-supply wells

MSW-1

MSW-2 MSW-3

0 1 Mile

0 0.5 1 Kilometer

0.5

480000 3998000480500 481000 481500 482000

3997500 3997000 3996500 3996000

Tuba City

Figure 2. Map showing Upper Moenkopi water-supply wells near the Moenkopi villages, Coconino County, Arizona.
Introduction 5

Program and water levels were measured by the USGS during 

the fieldwork in April and May 2010 (table 1). 

The wells produce groundwater from the Navajo 

Sandstone and the upper part of the Kayenta FormationNavajo Sandstone transition zone, both units of the N aquifer 

(fig. 3). MSW-1 produced 60 gal/min upon completion in June 

1977. The well discharge decreased to about 45 gal/min by 

October 2007, and was measured at 42.5 gal/min on May 5, 

2010. MSW-2 produced about 40 gal/min upon completion in 

February 1982 and was measured at 25 gal/min on May 12, 

2010. MSW-3 has been the lowest producing well of the three 

supply wells from the time it was completed in 1991. The 

well was originally reported to be capable of producing about 

35 gal/min, but discharge has decreased with time; discharge 

at MSW-3 was measured at 8 gal/min in October 2007, and 

was measured at 10 gal/min on April 28, 2010. Water levels 

in the three wells also have declined in recent years (U.S. 

Department of Health and Human Services, 2008).

The close spacing of the wells may be leading to 

additional drawdown and decreased production from well 

interference when the wells are operated simultaneously. As 

a result, Upper Moenkopi Village water operators rotate the 

Year well

constructed

USGS site

identification

number

Local

identification

number

Top of

casing 

elevation

(ft)

Depth to top 

and bottom 

of screened 

interval(s)

(ft)

Constructed 

depth and 

actual depth 

to bottom of 

well (ft)

Depth to

top of 

pump

(ft)

Static

depth 

to water1

(ft)

and date

Pumping 

depth

to water1

(ft) 

and date

Pumping 

discharge 

(gpm) and 

date

Upper Moenkopi Village water-supply well name

MSW-1

1977 360719111125901 A-32-11 

28DCA1

4,847 69-129 

(perforated 8-inch

 steel casing)

140

(backfilled 

with 

sediment to 

125)

100 87.0

May 12, 

2010

99.15

April 28, 

2010

42.5

May 5, 

2010

MSW-2

1982 360719111130401 A-32-11 

28DCA

4,846 72-77

105-125

(perforated 

intervals are

8-inch stainless 

steel

well screen)

142

(backfilled 

with 

sediment to 

127)

109 79.7

May 5, 

2010

1002

April 28, 

2010

25

May 12, 

2010

MSW-3

1991 360719111130001 A-32-11 

28DCA3

4,845 71-81 

125-145

166-176

226-236

(perforated 

intervals are

8-inch stainless 

steel

well screen)

280

(backfilled 

with 

sediment to 

241)

220 72.75

May 5, 

2010

88.5

April 28, 

2010

10

April 28, 

2010

1

 Measuring point at top of well casing 

2

 Measurement error possible due to cascading water

Alluvial and eolian deposits

Navajo Sandstone

Kayenta Formation

Moenave Formation

Chinle Formation

Modified from Harshbarger and others (1957)

Kayenta-Navajo Transition Zone

Well

QUATERNARY

JURASSIC

TRIASSIC

N Aquifer,

Water-bearing in places

Figure 3. Generalized stratigraphic section for the area near the 

Upper Moenkopi Village water-supply wells, Coconino County, Arizona.

Table 1. Construction, water-level, and pumping data from the Upper Moenkopi Village water-supply wells, Coconino County, Arizona.

[gpm, gallons per minute; ft, feet; water level and pumping data collected during fieldwork in April and May, 2010] 
6 Quality, Isotopes, and Radiochemistry of Water Sampled from the Upper Moenkopi Village Water-Supply Wells

of the perforated interval is above the water column under 

pumping conditions. This information guided the collection 

of water samples at MSW-1—samples were collected from 

a depth of 105 ft near the top of the water column and from 

a depth of 120 ft near the bottom of the perforated interval. 

MSW-2 has two perforated intervals, the first from 72 to 77 

ft and the second from 105 to 125 ft below the top of the well 

casing (table 1). Both perforated intervals consist of 8-in. 

stainless steel well screen. The pumping depth-to-water was 

about 100 ft on April 28, 2010—causing the upper perforated 

interval to be exposed above the water column under pumping 

conditions. Water samples from MSW-2 were collected from 

a depth of 107 ft near the top of the water column and from 

a depth of 120 ft near the bottom of the lower perforated 

interval. MSW-3 has four perforated intervals, the first from 

71 to 81 ft, the second from 125 to 145 ft, the third from 166 

to 176 ft, and the fourth from 226 to 236 ft below the top of 

the well casing (table 1). The four perforated intervals consist 

of 8-in. stainless steel well screen. The pumping depthto-water was 88.5 ft on April 28, 2010, causing the upper 

perforated interval to be exposed above the water column 

under pumping conditions. Water samples from MSW-3 were 

collected from a depth of 135 ft, within the zone of the second 

perforated interval, and from a depth of 230 ft, within the zone 

of the lowermost perforated interval. 

An attempt was made to collect well-bore flow data under 

pumping conditions in the three wells using a technique called 

the “tracer-pulse method” (Izbicki and others, 1999). The 

method uses a high-pressure hose equipped with valves for 

dye injection. The hose is filled with fluid containing an easily 

measured tracer, such as water colored with Rhodamine dye. 

The hose is lowered to a known depth in the well and a pulse 

of the tracer is injected into the water column. The travel time 

of the tracer to a detector on the surface is measured. The hose 

is then lowered to a deeper depth and another pulse of dye is 

released. The velocity is calculated as the difference in the 

travel times. The flow rate, given a known well diameter, is then 

calculated. A series of dye injections are released at different 

depths to construct a velocity profile for the well. If successful, 

the velocity profile can be used to guide the collection and 

interpretation of depth-dependent water-quality data. 

In addition to the limitations observed during the waterquality sampling, well construction issues with the three watersupply wells prevented the collection of meaningful well-bore 

flow data. At MSW-1 and MSW-2, the high-pressure hose used 

for dye injection could not be lowered past the top of the pump 

because the pumps were fitted with sand shrouds with diameters 

close to the inside diameter of the well casing, and the small 

space between the two would not allow for the passage of the 

dye-injection hose. At MSW-2 and MSW-3, leaking fittings in 

the discharge pipes at the top of the wells caused pumped water 

to cascade back into the wells, resulting in erroneous values in 

the well-bore flow data. Additionally, groundwater-level decline 

coupled with the relatively low permeability of the surrounding 

aquifer resulted in larger than predicted drawdown in the three 

wells. This resulted in a short column of water in the wells 

operation of the pumps on a nearly daily basis. The larger than 

predicted drawdown in the three wells and the resulting short 

column of water in the wells under pumping conditions—even 

during low pumping rates of 10–25 gal/min—resulted in the 

collection of fewer water-quality samples and prevented the 

collection of meaningful well-bore flow data. 

Methods of Study

Depth-Dependent Sampling and Well-Bore Flow

Coupled well-bore flow and depth-dependent waterquality data that were collected from wells under pumping 

conditions can be used to directly measure the vertical 

distribution of flow and contaminants into wells from aquifers. 

Recent advancements in interpretation of these data use 

numerical groundwater-flow models and particle tracking at 

the well-bore scale to estimate aquifer hydraulic properties, 

and to predict the change in well yield and quality with 

changes in well construction (Halford, 2009). Collection of 

coupled well-bore flow and depth-dependent water-quality 

data can facilitate redesign of existing wells to improve 

water quality, or guide construction of future wells to ensure 

suitable-quality water (Izbicki and others, 1999). 

Depth-dependent water samples were collected by the 

USGS from the three water-supply wells, (MSW-1, MSW-2, 

and MSW-3) for May 5–13, 2010. The samples were collected 

under pumping conditions to determine if there is a vertical 

distribution of water entering the wells from the surrounding 

aquifer. Depth-dependent samples were collected from the 

three production wells under pumping conditions using a gasdisplacement sample pump (Izbicki, 2004). The pump used 

in this study is about 6 in. long, less than 1 in. in diameter, 

and operated through repeated application and release of 

compressed gas. The pump is intended for use in production 

wells having limited access that prevents the use of traditional 

geophysical tools (such as wire-line bailers) used to collect 

depth-dependent water samples. Data collected at different 

depths within the production well reflect water quality at those 

depths under actual pumping conditions. 

The original scope of work called for the collection of 

water-quality samples at three positions within the water 

column of each well under pumping conditions—at the 

top, midpoint, and bottom portions of the screened interval. 

However, owing to the larger than predicted drawdown in the 

three wells and the resulting short column of water available 

to sample from in each well, a decision was made to collect 

water-quality samples from two positions in each well—at the 

top and bottom portions of the available water column.

The perforated interval within MSW-1 consists of a 60 ft 

section of 8-in. perforated steel casing from 69 to 129 ft below 

the top of the well casing (table 1). The pumping depth-towater was about 99 ft on April 28, 2010, thus about one-half 
Results of Water-Quality, Isotope, and Radiochemistry Analysis 7

under pumping conditions, even during low pumping rates of 

10–25 gal/min. The combination of these factors prevented the 

collection of meaningful well-bore flow data.

Water-Chemistry Data Collection and Analysis

Sampling procedures followed standard protocols for collection and preservation established in the USGS National Field 

Manual for the Collection of Water Quality Data (U.S. Geological 

Survey, variously dated). The major ion, nutrient, and trace metal 

water samples were analyzed by the USGS National WaterQuality Laboratory in Denver, Colorado. The radiochemistry 

water samples were analyzed by the Eberline Analytical Services 

in Richmond, California, and the carbon-14 (14C) water samples 

were analyzed by the McLean Laboratory at the Woods Hole 

Oceanographic Institute in Woods Hole, Massachusetts. 

Field parameters including temperature, pH, and specific 

conductance were measured with a Hydrolab MS5 multiparameter water-quality monitoring probe (manufactured 

by Hach Hydromet). Dissolved-oxygen concentrations were 

measured with an InSitu Troll® 9500 water-quality monitoring 

probe (InSitu, Inc.). The water-quality monitoring probes were 

calibrated each day of the sampling fieldwork. Titrations to 

determine total alkalinity and bicarbonate concentrations of the 

water samples were conducted in the field within 4 hours of 

sample collection using the inflection point method (Rounds, 

2012). Buffer solutions for the titrations were provided by 

the USGS National Water Quality Laboratory and pH was 

measured during the titrations with a ThermoOrion 5 Star pH 

meter (Thermo Scientific Orion).

Chemical constituents from the water-supply wells 

were compared to the U.S. Environmental Protection Agency 

(USEPA) primary and secondary drinking-water standards 

(U.S. Environmental Protection Agency, 2009). Maximum 

contaminant levels (MCLs), which are the primary regulations, 

are legally enforceable standards that apply to public water 

systems. MCLs protect drinking-water quality by limiting the 

levels of specific contaminants that can adversely affect public 

health. Secondary maximum contaminant levels (SMCLs) 

provide guidelines for the control of contaminants that may 

cause cosmetic effects (such as skin or tooth discoloration) or 

aesthetic effects (such as taste, odor, or color) in drinking water. 

The USEPA recommends compliance with SMCLs for public 

water systems; however, compliance is not enforced (U.S. 

Environmental Protection Agency, 2009).

Results of Water-Quality, Isotope, and 

Radiochemistry Analysis

Results of the water-quality, stable isotope, and 

radiochemistry sample analyses are shown in tables 2 and 3 

and also are available online at http://nwis.waterdata.usgs.gov/

az/nwis/qwdata by entering the USGS well site identification 

numbers listed in table 1. For comparison, table 2 also 

contains water-quality data for MSW-2 from samples collected 

in January 1992 and October 1993.

Water Quality

Field Parameters and Inorganics

At MSW-1, specific conductance was 533 and 603 μS/

cm for samples collected from the top and bottom portions 

of the water column, respectively. The pH was 8.7 and 7.3 

for samples collected from the top and bottom portions of 

the water column, respectively. Dissolved oxygen was not 

determined for the sample collected from the top of the water 

column and was 5.75 mg/L for the sample collected from 

the bottom portion of the water column. The total dissolved 

solids (TDS) was 332 mg/L for the sample collected from the 

top portion of the water-column sample and slightly higher 

at 374 mg/L for the sample from the bottom portion of the 

water column. Alkalinity was similar for the two samples 

collected at MSW-1, measuring 135.1 and 136.5 mg/L for 

the samples collected from the top and bottom portions of 

the water column, respectively. At MSW-1, bicarbonate 

concentrations were 164.7 and 166.4 mg/L for samples 

collected from the top and bottom portions of the water 

column, respectively. 

For MSW-2, specific conductance was 525 and 561 

μS/cm for the samples collected from the top and bottom 

portions of the water column, respectively. The pH was 8.06 

and 7.19 for the samples collected from the top and bottom 

portions of the water column, respectively. Dissolved oxygen 

was not determined for the sample collected from the top 

of the water column; however, a value of 7.86 mg/L was 

measured for the sample collected from the lower portion of 

the water column. TDS was not determined for the sample 

collected from the top of the water column; however, a value 

of 318 mg/L was measured for the sample from the bottom 

portion of the water column. Alkalinity also was similar for 

the two samples collected at MSW-2— 98.7 and 96.6 mg/L 

for the samples collected from the top and bottom portions 

of the water column, respectively. At MSW-2, bicarbonate 

concentrations were 120.3 and 117.8 mg/L for the samples 

collected from the top and bottom portions of the water 

column, respectively. 

For MSW-3, specific conductance was 596 and 488 

μS/cm for the samples collected from the top and bottom 

portions of the water column, respectively. The pH was 8.6 

for samples collected from the top and bottom portions of the 

water column. Dissolved oxygen was not determined for the 

sample collected from the top of the water column; however, 

a value of 5.3 mg/L was measured for the sample collected 

from the bottom portion of the water column. TDS was not 

determined for the sample collected from the top portion of the 

water column; however, a value of 303 mg/L was measured 

for the sample from the bottom portion of the water column. 
8 Quality, Isotopes, and Radiochemistry of Water Sampled from the Upper Moenkopi Village Water-Supply Wells

Alkalinity was similar for the two samples collected at MSW3, measuring 136.1 and 132.0 mg/L for the samples collected 

from the top and bottom portions of the water column, 

respectively. At MSW-3, bicarbonate concentrations were 

157.3 and 135.1 mg/L for the samples collected from the top 

and bottom portions of the water column, respectively. None of 

the water samples collected at MSW-1, MSW-2, and MSW-3 

and analyzed for TDS were greater than the USEPA SMCL 

standard of 500 mg/L. The USEPA SMCL range for pH is 6.5–

8.5. At MSW-1, the pH for the sample collected from the top 

of the water column was 8.65, slightly exceeding the SMCL. 

Additionally, at MSW-3, pH was 8.55 and 8.63 for the samples 

collected from the top and bottom portions of the water 

column, respectively. These pH values also slightly exceeded 

the USEPA SMCL and indicate that the water is alkaline.

The ratios of the major dissolved ions from the samples 

collected from MSW-1 and MSW-2 indicate water with a 

calcium and sulfate-ion composition (figs. 4A and 4B; table2). 

MSW-1 and MSW-2 are completed to similar depths in the 

Navajo Sandstone (table 1). There is not a significant vertical 

distribution of the major ion concentrations in the samples 

collected from the top and bottom portion of the water column 

in the two wells. Concentrations of the major dissolved ions 

for the four samples collected from MSW-1 and MSW-2 

ranged from 49.9 to 56.5 mg/L for calcium, 30.8 to 44.5 mg/L 

for sodium, 11.3 to 13.3 mg/L for magnesium, 1.96 to 2.13 

mg/L for potassium, 41.6 to 52.7 mg/L for chloride, 0.15 to 

0.29 mg/L for fluoride, and 62.5 to 81.7 mg/L for sulfate. The 

major ion concentrations for the samples collected at MSW-2 

as part of this study are similar to the samples collected in 

January 1992 and October 1993 (table 2). 

The samples collected at MSW-3 were higher in sodium 

and lower in calcium than the samples collected from MSW-1 

and MSW-2 and contained a similar sulfate-ion percentage 

(fig. 4; table 2). MSW-3 is about 140 ft deeper than MSW-1 

and MSW-2, with the lower portion of the well completed 

in the Kayenta Formation-Navajo Sandstone transition zone 

(fig. 3). Additionally, there was a vertical distribution of ion 

concentrations in the samples collected at MSW-3. Calcium 

concentrations for the samples collected at MSW-3 were 30.6 

mg/L for the sample collected from the top portion of the water 

column (135 ft below the top of the casing) and 8.21 mg/L 

for the sample collected from the bottom portion of the water 

column (230 ft below the top of the casing). In contrast, the 

sodium concentration increased with depth in the water column. 

Sodium concentrations were 78.8 and 96.6 mg/L for the 

Barometric 

pressure, 

(mm of 

mercury)

Dissolved 

oxygen, 

(mg/L)

Flow rate, 

(gpm)

pH, field, 

(standard 

units)

pH,

laboratory, 

(standard 

units)

Specific

conductance, 

(μS/cm at 25 

°C)

Temperature,

(25 °C)

Depth of well, 

feet below 

land 

surface datum

Sampling 

condition

Sampling 

method

Moenkopi water-supply well name and sample date

MSW-1, May 6, 2010

633 5.8 -- 7.3 7.9 603 18.6 -- Pumping Submersible 

pump

MSW-1, May 13, 2010

-- -- -- 8.7 8.2 533 18.4 -- Pumping Other

MSW-2, January 31, 1992

574 5 100 8 7.9 589 16.3 -- -- --

MSW-2, October 18, 1993

643 5.6 106 7.8 7.9 522 17 180 -- --

MSW-2, May 5, 2010

634 7.9 -- 7.2 7.6 525 24.3 -- Pumping Submersible 

pump

MSW-2, May 12, 2010

-- -- -- 8.1 8.1 561 18.8 -- Pumping Other

MSW-3, May 6, 2010

634 5.3 -- 8.6 9.2 488 19.9 -- Pumping Submersible 

pump

MSW-3, May 11, 2010

-- -- -- 8.6 8.7 596 19.1 -- Pumping Other

Table 2. Water quality data from Upper Moenkopi Village water-supply wells, Coconino County, Arizona.

[--, no data; <, less than; E, estimated; R, radchem non-detect, below ssLc; mg/L, milligrams per liter; mm, millimeters; gpm, gallons per minute; μs/cm, microsiemens per centimeter; °C, degrees Celsius]
Results of Water-Quality, Isotope, and Radiochemistry Analysis 9

Dissolved 

solids dried

at 180 °C,

 (mg/L)

Calcium, 

 (mg/L)

Magnesium, 

 (mg/L)

Potassium, 

 (mg/L)

Sodium,

 (mg/L)

Alkalinity, 

as calcium 

carbonate

 (mg/L)

Bicarbonate, 

 (mg/L)

Bromide, 

 (mg/L)

Carbonate, 

 (mg/L)

Chloride,

 (mg/L)

Moenkopi water-supply well name and sample date

MSW-1, May 6, 2010

374 56.5 13.3 2.13 44.5 136 166 0.431 -- 52.7

MSW-1, May 13, 2010

332 49.9 11.3 1.99 40 135 165 0.336 -- 41.6

MSW-2, January 31, 1992

345 56 13 2.1 42 130 159 -- 0 59

MSW-2, October 18, 1993

290 51 12 1.9 36 104 127 -- 0 48

MSW-2, May 5, 2010

318 51.5 11.6 1.96 33.3 96.6 118 0.46 -- 51.1

MSW-2, May 12, 2010

-- 52.4 11.9 1.99 30.8 98.7 120 0.538 -- 59.2

MSW-3, May 6, 2010

303 8.21 2.09 1.16 96.6 132 135 0.128 12.7 31.5

MSW-3, May 11, 2010

-- 30.6 7.57 1.71 78.8 136 157 0.373 4.2 51

Fluoride, 

 (mg/L)

Silica, 

 (mg/L)

 as SiO2

Sulfate,

 (mg/L)

As nitrogen (mg/L) As phosphorus (mg/L)

Aluminum, 

(μg/L)

Ammonia

plus organic 

nitrogen

Ammonia Nitrate 

plus nitrite Nitrite Orthophosphate

Phosphorus

Moenkopi water-supply well name and sample date

MSW-1, May 6, 2010

0.24 14.4 81.7 0.21 < .020 1.24 < .002 0.011 < .04 < 3.4

MSW-1, May 13, 2010

0.29 13.6 62.5 < .10 < .020 1.07 < .002 0.01 < .04 < 3.4

MSW-2, January 31, 1992

0.3 14 80 -- 0.01 1.2 < .010 < .01 -- --

MSW-2, October 18, 1993

0.2 15 69 -- 0.02 1.8 < .010 < .01 -- --

MSW-2, May 5, 2010

0.15 13 73.8 E .05 < .020 2.06 < .002 0.011 < .04 < 3.4

MSW-2, May 12, 2010

0.16 13.1 81.7 0.1 < .020 2.24 E .001 0.01 < .04 < 3.4

MSW-3, May 6, 2010

0.94 12.1 51.1 E .05 < .020 1.63 < .002 0.029 E .02 7

MSW-3, May 11, 2010

0.58 13.6 86.9 0.14 < .020 1.84 < .002 0.039 < .04 5.1

Table 2. Water quality data from Upper Moenkopi Village water-supply wells, Coconino County, Arizona.—Continued

Table 2. Water quality data from Upper Moenkopi Village water-supply wells, Coconino County, Arizona.—Continued
10 Quality, Isotopes, and Radiochemistry of Water Sampled from the Upper Moenkopi Village Water-Supply Wells

Barium, 

(μg/L)

Beryllium, 

(μg/L)

Cadmium,

(μg/L)

Chromium,

(μg/L)

Cobalt, 

(μg/L)

Copper, 

(μg/L)

Iron, 

(μg/L)

Lead, 

(μg/L)

Lithium,

(μg/L)

Manganese, 

(μg/L)

Moenkopi water-supply well name and sample date

MSW-1, May 6, 2010

91.7 < .20 < .6 < 1.2 < 1.6 < 2.8 < 6.0 0.259 45.6 0.22

MSW-1, May 13, 2010

80.3 < .20 < .6 < 1.2 < 1.6 < 2.8 15.8 E .018 48.5 1.11

MSW-2, January 31, 1992

-- -- -- -- -- -- < 3.0 -- -- --

MSW-2, October 18, 1993

-- -- -- -- -- -- 7 -- -- --

MSW-2, May 5, 2010

94.5 < .20 < .6 < 1.2 < 1.6 < 2.8 E 5.8 0.222 36.6 0.73

MSW-2, May 12, 2010

104 < .20 < .6 < 1.2 < 1.6 < 2.8 12.7 E .021 44.3 1.8

MSW-3, May 6, 2010

12.2 < .20 < .6 < 1.2 < 1.6 < 2.8 15.8 0.044 59.7 1.78

MSW-3, May 11, 2010

44.4 < .20 < .6 < 1.2 < 1.6 < 2.8 13.2 < .030 69.8 3.13

Mercury, 

(μg/L)

Molybdenum, 

(μg/L)

Nickel, 

(μg/L)

Silver, 

(μg/L)

Strontium, 

(μg/L)

Vanadium, 

(μg/L)

Zinc, 

(μg/L)

Antimony, 

(μg/L)

Arsenic, 

(μg/L)

Boron, 

(μg/L)

Moenkopi water-supply well name and sample date

MSW-1, May 6, 2010

< .010 < 4.4 < 4.2 < 4.0 1,030 6.6 14.9 < .054 2.4 75

MSW-1, May 13, 2010

< .010 < 4.4 < 4.2 < 4.0 864 5.9 26.9 E .052 2 71

MSW-2, January 31, 1992

-- -- -- -- -- -- -- -- 2 80

MSW-2, October 18, 1993

-- -- -- -- -- -- -- -- 2 70

MSW-2, May 5, 2010

< .010 < 4.4 < 4.2 < 4.0 884 7.6 18 < .054 2.1 69

MSW-2, May 12, 2010

< .010 < 4.4 < 4.2 < 4.0 883 7.2 93.5 0.056 1.8 74

MSW-3, May 6, 2010

< .010 7.1 < 4.2 < 4.0 234 13.5 5 < .054 6.8 323

MSW-3, May 11, 2010

< .010 < 4.4 < 4.2 < 4.0 682 10.3 8.7 E .041 4.1 219

Table 2. Water quality data from Upper Moenkopi Village water-supply wells, Coconino County, Arizona.—Continued

Table 2. Water quality data from Upper Moenkopi Village water-supply wells, Coconino County, Arizona.—Continued
Results of Water-Quality, Isotope, and Radiochemistry Analysis 11

Thorium-228,

(pC/L)

Thorium-230, 

(pC/L)

Thorium-232, 

(pC/L)

Tritium, 

(pC/L)

Uranium (natural), 

(μg/L)

d Carbon-13, 

(per mil)

d Oxygen-18, 

(per mil)

Deuterium/protium ratio, 

(per mil)

Moenkopi water-supply well name and sample date

MSW-1, May 6, 2010

R -.01 R .02 R .000 R .1 3.85 -8.04 -8.61 -74.7

MSW-1, May 13, 2010

0.04 0.09 R .000 R .3 3.16 -7.1 -8.73 -74.7

MSW-2, January 31, 1992

-- -- -- -- -- -- -- --

MSW-2, October 18, 1993

-- -- -- -- -- -- -- --

MSW-2, May 5, 2010

R -.02 R .01 R .000 1.3

(0.41 TU)

3.4 -8.06 -9.03 -74.9

MSW-2, May 12, 2010

0.07 R -.10 R .000 R .3 3.52 -8.03 -9.09 -75.5

MSW-3, May 6, 2010

R .01 R -.01 0.034 R -.7 4.51 -7.52 -9.52 -79.1

MSW-3, May 11, 2010

0.15 R -.05 R .000 R -.2 4.88 -8.37 -9.12 -76.7

Selenium, 

(μg/L)

Organic 

carbon, 

 (mg/L)

Suspended sediment,

dry weight, (pC/gm)

Carbon-14 (percent 

modern)

Gross alpha activity 

curve (pC/L)

Gross beta activity 

curve (pC/L)

Uranium234Uranium235Uranium238Counting 

error, filtered Filtered

 30-day 

count,

Th-230

72-hour 

count,

Th-230

30-day 

count,

Cs-137

72-hour 

count,

Cs-137

Moenkopi water-supply well name and sample date

MSW-1, May 6, 2010

2.1 0.72 0.005 R -.0003 0.0036 0.26 69.27 7.3 9.8 2.4 2.3

MSW-1, May 13, 2010

1.4 E .49 0.05 R .02 R .000 0.24 67.34 6 7.2 2.4 1.4

MSW-2, January 31, 1992

-- -- -- -- -- -- -- -- -- -- --

MSW-2, October 18, 1993

-- -- -- -- -- -- -- -- -- -- --

MSW-2, May 5, 2010

3.5 0.82 0.0031 R .0000 0.0012 0.22 65.2 5.1 8.1 2.8 1.6

MSW-2, May 12, 2010

3.9 0.97 R -.009 R -.011 R .009 0.23 65.24 6.4 8.7 2.6 1.9

MSW-3, May 6, 2010

1.1 E .64 0.0078 R .0004 0.003 0.18 33.44 6.4 5.1 1.4 1.3

MSW-3, May 11, 2010

2.2 1.1 R -.03 R -.031 R .000 0.2 52.72 8.6 9.1 2.3 0.9

Table 2. Water quality data from Upper Moenkopi Village water-supply wells, Coconino County, Arizona.—Continued

Table 2. Water quality data from Upper Moenkopi Village water-supply wells, Coconino County, Arizona.—Continued
12 Quality, Isotopes, and Radiochemistry of Water Sampled from the Upper Moenkopi Village Water-Supply Wells

A. Well MSW-1 Chloride (Cl) + Fluoride (F) + Sulfate (SO4)

Bicarbonate (HCO3) + Carbonate (CO3)

80

60

40

20

20

40

60

80

20

0

40

60

80

100

Magnesium (Mg)

100

80

60

40

20

0

Sodium (Na) + Potassium (K)

Calcium (Ca) + Magnesium (Mg)

20

40

60

80

80

60

40

20

80

100

100

60

40

20

0

Suflfate (SO4)

0

20

40

60

80

Calcium(Ca) Chloride(Cl) + Fluoride(F)

Percent of total milliequivalents per liter

100 100

100

100

80 60 40 20 0 20 40 60 80

0 0

0

Samples collected

May 6, 2010

(lower portion 

of water column)

May 13, 2010

(upper portion 

of water column)

B. Well MSW-2 Chloride (Cl) + Fluoride (F) + Sulfate (SO4)

Bicarbonate (HCO3) + Carbonate (CO3)

80

60

40

20

20

40

60

80

20

0

40

60

80

100

Magnesium (Mg)

100

80

60

40

20

0

Sodium (Na) + Potassium (K)

Calcium (Ca) + Magnesium (Mg)

20

40

60

80

80

60

40

20

80

100

100

60

40

20

0

Suflfate (SO4)

0

20

40

60

80

Calcium(Ca) Chloride(Cl) + Fluoride(F)

Percent of total milliequivalents per liter

Samples collected

January 31, 1992

October 18, 1993

May 5, 2010

(upper portion 

of water column)

May 12, 2010

(lower portion 

of water column)

100 100

100

100

80 60 40 20 0 20 40 60 80

0 0

0

Figure 4. Trilinear diagram showing 

relative compositions of groundwater 

samples collected from the Upper 

Moenkopi Village water-supply wells in 

Coconino County, Arizona, under pumping 

conditions; A. Well MSW-1; B. Well MSW2; C. Well MSW-3.
Results of Water-Quality, Isotope, and Radiochemistry Analysis 13

samples collected from the top and bottom portions of the water 

column, respectively. Magnesium concentrations decreased from 

7.57 to 2.09 mg/L for the samples collected from the top and 

bottom portions of the water column, respectively. Potassium 

concentrations were 1.71 and 1.16 mg/L for the samples 

collected from the top and bottom portions of the water column, 

respectively. Carbonate increased from 4.2 to 12.7 mg/L for the 

samples collected from the top and bottom portions of the water 

column, respectively. Chloride decreased from 51 to 31.5 mg/L 

for the samples collected from the top and bottom portions of the 

water column, respectively. Fluoride concentrations were higher 

for the samples collected at MSW-3 than the samples collected 

at MSW-1 and MSW-2, and increased with depth from 0.58 to 

0.94 mg/L for the samples collected from the bottom portion 

of the water column. Sulfate concentrations for the samples 

collected at MSW-3 decreased with depth from 86.9 to 51.1 

mg/L for the samples collected from the top and bottom portions 

of the water column, respectively. 

Previous studies of the Navajo Sandstone and the Kayenta 

Formation-Navajo Sandstone transition zone portions of the 

N aquifer generally reported calcium bicarbonate to sodium 

bicarbonate type water with low-to-moderate TDS and other 

trace elements (Cooley and others, 1969; Eychaner, 1983; 

Lopes and Hoffmann, 1997; Tetra Tech EM Inc., 2004; Carruth 

and Bills, 2012). Additionally, Cooley and others (1969) 

reviewed 140 groundwater samples from the Navajo Sandstone 

and found the principal chemical constituents to be calcium 

and sodium, and bicarbonate, sulfate, and chloride ions. TDS 

of the 140 samples ranged from about 90 to 1,000 ppm, and 

the most common minor chemical constituents were fluoride, 

nitrate, magnesium, silica, and iron. 

Nutrients

Nutrients including nitrogen, phosphorus, and ammonia 

compounds can be a water-quality concern in concentrations 

that exceed USEPA MCLs. Major sources of nutrients include 

fertilizers, sewage effluent, and dissolution of naturally 

occurring minerals (Mueller and Helsel, 1996). For the samples 

collected at MSW-1, MSW-2, and MSW-3, nitrate (as nitrogen) 

ranged from 1.07 to 2.24 mg/L—less than the USEPA MCL of 

10 mg/L. Additionally, concentrations of nitrite (as nitrogen), 

orthophosphate (as phosphorus), phosphorus, and ammonia (as 

nitrogen) generally were low or less than detection limits for 

samples from all three water-supply wells (table 2). None of 

the water samples collected at MSW-1, MSW-2, and MSW-3 

exceeded the USEPA MCL standards for nutrients (U.S. 

Environmental Protection Agency, 2009).

C. Well MSW-3 Chloride (Cl) + Fluoride (F) + Sulfate (SO4)

Bicarbonate (HCO3) + Carbonate (CO3)

80

60

40

20

20

40

60

80

20

0

40

60

80

100

Magnesium (Mg)

100

80

60

40

20

0

Sodium (Na) + Potassium (K)

Calcium (Ca) + Magnesium (Mg)

20

40

60

80

80

60

40

20

80

100

100

60

40

20

0

Suflfate (SO4)

0

20

40

60

80

Calcium(Ca) Chloride(Cl) + Fluoride(F)

Percent of total milliequivalents per liter

100 100

100

100

80 60 40 20 0 20 40 60 80

0 0

0

Samples collected

May 6, 2010

(lower portion 

of water column)

May 11, 2010

(upper portion 

of water column)

Figure 4.—Continued
14 Quality, Isotopes, and Radiochemistry of Water Sampled from the Upper Moenkopi Village Water-Supply Wells

Carbon-14, normalized Carbon-14, de-normalized Calculated Carbon-14

age, in years before present

pM, Error 1 s pM pM, Error 1 s pM normalized de-normalized

Moenkopi water-supply well name and sample date

MSW-1, May 6, 2010

67.34 0.24 69.84 0.24 3176 2884

MSW-1, May 13, 2010

69.27 0.26 71.70 0.26 2949 2672

MSW-2, May 5, 2012

65.24 0.23 67.53 0.23 3431 3154

MSW-2, May 12, 2012

65.2 0.22 3436

MSW-3, May 6, 2010

52.72 0.2 54.53 0.20 5143 4871

MSW-3, May 11, 2010

33.44 0.18 34.65 0.18 8799 8514

Trace Elements

The samples collected from MSW-1, MSW-2, and 

MSW-3 also were analyzed for selected trace elements, 

some of which can cause negative health effects if there 

is long-term exposure above the USEPA MCL (U.S. 

Environmental Protection Agency, 2009). Samples from the 

three water-supply wells analyzed for arsenic did not contain 

concentrations that exceeded the USEPA MCL of 10 μg/L. 

Arsenic concentrations ranged from 1.8 to 2.4 μg/L for the 

samples collected from MSW-1 and MSW-2. For MSW-3, 

arsenic concentrations ranged from 4.1 to 6.8 μg/L—the 

higher arsenic sample was collected from the bottom portion 

of the water column, 230 ft below the top of the casing. 

Uranium is an element of concern in the vicinity of 

Upper Moenkopi Village. Studies are ongoing to determine if 

elevated concentrations of uranium occur in the vicinity of the 

Tuba City Landfill and Open Dump Site and if groundwater 

from these sites could migrate toward the Upper Moenkopi 

Village water-supply wells (Morgan, 2002; Johnson and 

Wirt, 2009; Otton and others, 2009). Uranium is a naturally 

occurring radioactive element and can occur in groundwater 

when uranium deposits are present in the groundwater-flow 

system. Previous studies have indicated that uranium deposits 

occur at levels of economic importance in the surrounding 

area (Johnson and Wirt, 2009). Uranium ore mined from the 

Chinle Formation was processed in a nearby facility known as 

the Rare Metals Mill. In December 2003, the USEPA began 

regulating uranium in community water supplies in order to 

reduce the risk of cancer and kidney disease. For the samples 

collected from MSW-1 and MSW-2, uranium concentrations 

ranged from 3.16 to 3.85 μg/L. For MSW-3, uranium 

concentrations ranged from 4.51 to 4.88 μg/L. There is no 

significant vertical distribution of uranium concentrations in 

samples collected from the water-supply wells and no sample 

exceeded the USEPA MCL for uranium of 30 μg/L (table 2).

The samples collected from MSW-1, MSW-2, and 

MSW-3 were analyzed for other trace metals including 

aluminum, barium, chromium, copper, lead, mercury, 

nickel, selenium, silver, and zinc (table 2). Trace metals in 

groundwater may be derived from a variety of natural and 

anthropogenic sources. Many of these metals are required 

by humans in trace amounts but in larger, persistent dosages 

that exceed the USEPA MCL, these heavy metals can become 

toxic when they are not metabolized by the body (U.S. 

Environmental Protection Agency, 2009). None of the samples 

collected from MSW-1, MSW-2, or MSW-3 exceeded the 

USEPA MCL or SMCL for trace metals (table 2 and U.S. 

Environmental Protection Agency, 2009). 

Isotopes

Water samples from the three water-supply wells were 

analyzed for a suite of environmental tracers that included 

the stable isotopes of oxygen and hydrogen, and radioactive 

isotopes of carbon and hydrogen. The isotope data can be 

used to develop and refine conceptual models of groundwaterflow systems. They also can be used to investigate sources 

Table 3. Carbon-14 radioisotope data used to estimate ages of groundwater sampled from the 

upper Moenkopi Village water-supply wells, Coconino County, Arizona.

[--, no data; pM, percent modern carbon; mg/L, milligrams per liter; mm, millimeters; gpm, gallons per minute; μs/

cm, microsiemens per centimeter; °C, degrees Celsius]
Results of Water-Quality, Isotope, and Radiochemistry Analysis 15

of recharge and to determine rates of movement and ages of 

groundwater (Clark and Fritz, 1997).

The use of oxygen- 18 (18O) and deuterium (2H) stable 

isotopes are helpful in estimating groundwater recharge 

sources (Coplen, 1993). In general, water recharged under 

cooler climatic conditions is more depleted in 18O and 2H; such 

stable isotope signatures have been observed in the nearby 

Black Mesa area (Truini and Longsworth, 2003). Additionally, 

evaporation during recharge and (or) evaporation from the top 

of the water table can produce a waterline with a lower slope 

(Coplen, 1993). Groundwater samples from the three Upper 

Moenkopi Village water-supply wells aligns with a local 

waterline (LWL) that is approximately parallel to the global 

meteoric water line (fig. 5). These signatures are similar to 

other reported data for shallow wells and springs in the area 

that discharge from N aquifer (Johnson and Wirt, 2009).

Sampling of the radioactive isotope of hydrogen (3H 

or tritium) was done to approximate the age of groundwater 

pumped by the wells. Tritium was released into the Earth’s 

atmosphere in large quantities during nuclear bomb testing 

in the 1950s (Michel, 1989). The current level of tritium 

in the atmosphere in the Southwestern United States is 

approximately 5 tritium units (TU) (A. Manning, U.S. 

Geological Survey, oral commun., 2007). A surface-water 

sample in Pasture Canyon less than 0.5 mi from the Moenkopi 

water-supply wells (fig. 2) had a tritium concentration of 4.9 

TU, which probably represents current exchange with the 

atmosphere (Johnson and Wirt, 2009). Water samples with 

values of tritium less than 1 TU are interpreted to be primarily 

-60

-65

-70

-75

-80

-85

-90

-95

-100

-14.0 -13.0 -12.0 -11.0 -10.0 -9.0 -8.0

Meteoric water line

Surface water

Samples from regional groundwater wells

Upper Moenkopi water-supply wells Coconino 

Sandstone

Muav Limestone

Well 2 Well 1

Moenkopi

School

spring Global Meteoric Water Line (GMWL)

Local Water Line (LWL)

Redwall Limestone

Navajo 

Sandstone

Redwall Limestone

Well 3

δ2H (‰ VSMOW)

δ18O (‰ VSMOW)

pre-bomb water (pre-1952). Samples with 1–2 TU may have a 

significant portion of pre-bomb water but also may have some 

post-bomb water due to mixing. All but one sample collected 

during this study had 3H concentrations at or less than the 

detection limit for tritium and are interpreted to contain no 

modern water. The sample from the top of the water column 

in MSW-2 had a 3H concentration of 1.3 pC/L (0.41 TU), 

indicating that composition is primarily pre-bomb (pre-1952), 

but may contain a small fraction of post-bomb modern water 

water (table 2).

Carbon-14 (14C) is a naturally occurring radioactive 

isotope of carbon used to estimate the age of waters in 

the 500–50,000 years before present range. Carbon-14 is 

produced in the upper atmosphere as cosmic rays react with 

atmospheric nitrogen-14 (14N) to produce 14C and hydrogen-1 

(1H). In the upper atmosphere, 14C is rapidly oxidized to CO2

which readily mixes into the lower atmosphere. Any material 

using or reacting with atmospheric CO2 (plants and water) 

has a 14C activity equal to atmospheric 14C while it is in 

equilibrium with the atmospheric carbon reservoir (Pearson 

and White, 1967). Carbon-14 activity is reported as percent 

modern carbon (pmc) and, by convention, the modern pre1950 (pre-nuclear weapons testing) activity of atmospheric 

14C is 100 pmc. 

Carbon-14 generally enters the hydrologic cycle through 

the following pathways: (1) dissolution of atmospheric CO2

into rainwater and surface water, (2) plant respired CO2

in the soil zone that dissolves into water, (3) CO2 resulting 

from oxidation of organic material in the soil that dissolves 

Figure 5. Graph 

showing oxygen-18 (18O) 

and deuterium (2H) data 

from the Upper Moenkopi 

village water-supply 

wells and comparison 

with other water sources 

in the surrounding 

area, Coconino County, 

Arizona.
16 Quality, Isotopes, and Radiochemistry of Water Sampled from the Upper Moenkopi Village Water-Supply Wells

into water, and (4) dissolution of mineral phases containing 

geologically young carbon, particularly in carbonate rocks. 

Kalin (2000) provides a comprehensive review of the 

radiocarbon groundwater dating method. Table 3 shows the 

14C radioisotope data used to estimate ages of groundwater 

sampled from Upper Moenkopi Village water-supply wells. 

Data were used to estimate the pmc and ages of groundwater 

in the wells. The estimated 14C age of groundwater in MSW-1 

and MSW-2, both completed about 140 ft into the Navajo 

Sandstone, is about 3,000 years before present. The estimated 

14C age of groundwater in MSW-3, completed about 240 ft 

into the Navajo Sandstone-Kayenta Formation transition zone 

is older, about 5,000 years before present in the upper portion 

of the water column and about 8,500 years before present in 

the lower portion of the water column (table 3).

Radiochemistry

Radioactive elements are naturally present in a wide 

range of concentrations in rocks, soil, and water and the 

occurrence and distribution of radionuclides in groundwater 

is controlled primarily by the local geology and geochemistry 

(Zapecza and Szabo, 1988). In the vicinity of Upper 

Moenkopi Village, uranium processed at the Rare Metals Mill 

(RMM) was not derived from the local Navajo Sandstone, 

but from the Chinle Formation near Cameron and from other 

formations in northeastern Arizona (Johnson and Wirt, 2009). 

Measurements of gross alpha and beta activities serve 

as a useful screening technique that can provide information 

about natural and mined sources of radiation in the water 

supply and to estimate the corresponding potential public 

health impact. Gross alpha particle activity is a measure of the 

total amount of radioactivity in a water sample attributable 

to the radioactive decay of alpha-emitting elements. Gross 

alpha can be a concern for natural radioactivity in water as 

it refers to the radioactivity of uranium (U), thorium (Th), 

radium (Ra), as well as radon (Rn) and descendants (U.S. 

Environmental Protection Agency, 2009). Alpha particles 

are highly ionizing, but the particles travel short distances 

in air (< 2 in.) before being absorbed. Alpha particles have 

little ability to penetrate objects; thus, they can be stopped 

by a sheet of paper or the outer layer of skin. The external 

hazard from alpha particles is minimal, but the internal 

hazard when they are inhaled or ingested may be significant 

(U.S. Environmental Protection Agency, 2009). The USEPA 

MCL for gross alpha particle activity in drinking water is 15 

pCi/L (U.S. Environmental Protection Agency, 2009). The 

gross alpha radioactivity of all samples collected from the 

three water-supply wells were less than the USEPA MCL and 

ranged from about 5.1 to 9.8 pCi/L (table 2).

Gross beta particle activity is a measure of the total 

amount of radioactivity in a water sample attributable to the 

radioactive decay of beta-emitting elements. Beta particles 

usually travel greater distances in air than alpha particles 

(about 6 ft) before being absorbed. Beta particles are more 

penetrating than alpha particles, and some are capable of 

penetrating the skin and causing radiation damage (U.S. 

Environmental Protection Agency, 2009). Gross beta particle 

activity is reported in pCi/L as cesium-137 (Cs-137). The 

USEPA MCL for gross beta particle activity states that the 

average annual concentration of beta particle activity from 

radionuclides in drinking water shall not produce an annual 

dose equivalent to the total body or any internal organ greater 

than 4 millirems per year. The gross beta radioactivity of 

samples collected from the three water-supply wells are not 

considered elevated and ranged from about 0.9 to 2.8 pCi/L 

(table 2).

Summary 

This report documents the collection and analysis of 

depth-dependent water samples under pumping conditions 

from the three public water-supply wells in Upper Moenkopi 

Village, referred to as MSW-1, MSW-2, and MSW-3. 

Samples from these wells were analyzed for a range of 

chemical and isotopic constituents including major ions, 

nutrients, trace elements, stable and radioactive isotopes, and 

radiochemistry. The study assessed the source, distribution 

of flow, and quality of water from each of the three public 

water-supply wells. Data collected during this study can be 

used to (1) assess the quality of the existing municipal water 

supply, (2) provide a baseline for comparison with future 

water-quality monitoring, (3) evaluate management options 

to address possible contaminant sources, and (4) provide 

information to design and locate future water-supply wells.

Previous hydrologic and geochemical investigations 

have determined that water supplies for the Upper Moenkopi 

Village are limited and vulnerable to potential sources of 

contamination including the Tuba City Landfill and a former 

uranium processing facility known as the Rare Metals Mill. 

Studies are ongoing to determine if uranium and other metals 

in groundwater beneath the landfill are greater than regional 

groundwater concentrations and if a flow path exists between 

the Tuba City Landfill area and the village water-supply 

wells.

Analyses of major ions, nutrients, selected trace metals, 

isotopes, and radiochemistry were done on the groundwater 

samples from the three wells to describe general waterquality conditions and groundwater ages in and immediately 

surrounding the Upper Moenkopi Village public-supply 

wells. Chemical constituents from the water-supply wells 

were compared to the U.S. Environmental Protection Agency 

(USEPA) primary and secondary drinking water standards. 

None of the water samples collected at MSW-1, MSW-2, and 

MSW-3 exceeded USEPA primary drinking water standards. 

The pH for a water sample collected from the top of the water 

column in MSW-1 measured 8.65, exceeding the USEPA 

secondary drinking water standard for a pH range of 6.5–8.5. 

Additionally, at MSW-3, the pH ranged from 8.55 and 8.63 
References 17

for the samples collected from the top and bottom portion of 

the water column—these pH values also exceeded the USEPA 

secondary drinking water standard.

The ratios of the major dissolved ions from the samples 

collected from MSW-1 and MSW-2 indicate water with 

a calcium and sulfate-ion composition and no significant 

vertical distribution of ion concentrations within the wells. 

Samples collected at MSW-3 are higher in sodium and lower 

in calcium than the samples collected from MSW-1 and 

MSW-2 and contain a similar sulfate-ion percentage. MSW-3 

is about 140 ft deeper than MSW-1 and MSW-2 and there is 

a vertical distribution of ion concentrations in the samples 

collected at the well.

Groundwater samples from the three water-supply wells 

analyzed for oxygen-18 and deuterium stable isotopes appear 

to align with a local water line that is approximately parallel 

to the global meteoric water line. Tritium concentrations 

in samples from MSW-1 and MSW-3 were at or less than 

laboratory detection limits; these samples were interpreted to 

contain no modern water. A sample from the top of the water 

column at MSW-2 had a tritium concentration of 0.41 tritium 

units, indicating that the composition is primarily pre-bomb 

(pre-1952) water, but may contain a small fraction of postbomb modern water. 

The estimated carbon-14 age of groundwater sample 

from MSW-1 and MSW-2, both completed about 140 feet 

into the Navajo Sandstone, is about 3,000 years before 

present. The estimated carbon-14 age of groundwater sampled 

from MSW-3, completed about 240 feet into the Kayenta 

Formation-Navajo Sandstone transition zone is older, about 

5,000 years before present in the top portion of the water 

column and about 8,500 years before present in the bottom 

portion of the water column. The gross alpha radioactivity of 

samples collected from the three water-supply wells ranged 

from 5.1 to 9.8 picocuries per liter (pCi/L)—less than USEPA 

primary drinking water standard of 15 pCi/L. The gross beta 

radioactivity of samples collected from the wells ranged from 

0.9 to 2.8 pCi/L and are not considered elevated relative to 

the USEPA primary drinking water standard. 

Acknowledgments

The authors thank William Charley, Governor of Upper 

Moenkopi Village, for providing logistical support, wellvideo logs, and well-operations technicians from his staff. 

Governor Charley also approved a contract on short notice 

with Flagstaff Well and Supply Company to replace a leaking 

pump column on MSW-2 and to remove the sand shrouds 

on MSW-1 and MSW-2 to allow for the collection of depth 

dependent water samples. Pete Mitchell of the Indian Health 

Service provided onsite logistical support and assistance. 

Hopi Water Resources Program Director, Lionel Puhuyesva, 

provided support for the project and valuable input during 

project meetings. 

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Manuscript approved for publication July 10, 2013

Edited by John Buursma

Design and layout by Jeanne S. DiLeo
Carruth and others—Quality, Isotopes, and Radiochemistry of Water Sampled from the Upper Moenkopi Village Water-Supply Wells—Open-File Report 2013–1162