UNLV Retrospective Theses & Dissertations
1-1-1989
Hydrogeology and ground-water quality in the Sanders area, western Puerco River basin, Arizona
Earle Campbell Dixon University of Nevada, Las Vegas
Follow this and additional works at: https://digitalscholarship.unlv.edu/rtds
Repository Citation Dixon, Earle Campbell, "Hydrogeology and ground-water quality in the Sanders area, western Puerco River basin, Arizona" (1989). UNLV Retrospective Theses & Dissertations. 70. http://dx.doi.org/10.25669/cvc5-vjp4
This Thesis is protected by copyright and/or related rights. It has been brought to you by Digital Scholarship@UNLV with permission from the rights-holder(s). You are free to use this Thesis in any way that is permitted by the copyright and related rights legislation that applies to your use. For other uses you need to obtain permission from the rights-holder(s) directly, unless additional rights are indicated by a Creative Commons license in the record and/ or on the work itself.
This Thesis has been accepted for inclusion in UNLV Retrospective Theses & Dissertations by an authorized administrator of Digital Scholarship@UNLV. For more information, please contact [email protected]. INFORMATION TO USERS
The most advanced technology has been used to photograph and reproduce this manuscript from the microfilm master. UMI films the text directly from the original or copy submitted. Thus, some thesis and dissertation copies are in typewriter face, while others may be from any type of computer printer.
The quality of this reproduction is dependent upon the quality of the copy submitted. Broken or indistinct print, colored or poor quality illustrations and photographs, print bleedthrough, substandard margins, and improper alignment can adversely affect reproduction.
In the unlikely event that the author did not send UMI a complete manuscript and there are missing pages, these will be noted. Also, if unauthorized copyright material had to be removed, a note will indicate the deletion.
Oversize materials (e.g., maps, drawings, charts) are reproduced by sectioning the original, beginning at the upper left-hand corner and continuing from left to right in equal sections with small overlaps. Each original is also photographed in one exposure and is included in reduced form at the back of the book.
Photographs included in the original manuscript have been reproduced xerographically in this copy. Higher quality 6" x 9" black and white photographic prints are available for any photographs or illustrations appearing in this copy for an additional charge. Contact UMI directly to order.
University Microfilms International A Beil & Howell Information Company 300 North Zeeb Road. Ann Arbor. Ml 48106-1346 USA 313 761-4700 800 521-0600
Order Number 1340580
Hydrogeology and ground-water quality in the Sanders area, western Puerco River basin, Arizona
Dixon, Earle Campbell, M.S.
University of Nevada, Las Vegas, 1990
UMI 300 N. Zeeb Rd. Ann Arbor, MI 48106
HYDROGEOLOGY AND GROUND-WATER QUALITY
IN THE SANDERS AREA, WESTERN
PUERCO RIVER BASIN, ARIZONA
by
Earle Campbell Dixon
A thesis submitted in partial fulfillment of the requirements for the degree of
Master of Science in Geoscience
Department of Geoscience University of Nevada, Las Vegas May, 1990 The thesis of Earle Campbell Dixon for the degree of Master of Science in Geosciences is approved.
Chairperson, John W. Hess, Ph.D.
Examining Committee Meplber, Steve A. Mizell, Ph.D.
Exampiing Committee Menfber . Duebendorfer, Ph.D.
Gra^dW^e Faculty f^pnisent^tive, Gary B. Palmer, Fh.D
CJ Graduate Dean, Ronald W. Smith, Ph.D.
University of Nevada, Las Vegas May 1990 ABSTRACT
Ground-water in the western Puerco River basin near Sanders, Arizona, was evaluated to identify areas of poor water quality and possible radionuclide con tamination from natural and/or anthropogenic sources. In addition to docu mented radioactive occurrences in the regional Chinle Formation, the headwaters of the Puerco River have been host to uranium mine waste discharge and spoils from a tailings pond failure in 1979. Samples from 42 wells and springs were collected during 1987-88 for inorganic ion and radionuclide analysis. Waters, originating from the Alluvial, Bidahochi, and Chinle aquifers, contained variable amounts of dissolved solids and radioactivity. Dissolved solids content ranged from 105 to 1390 mg//, and combined gross alpha and beta activities ranged from 1 to 590 pCi//. In the Alluvial and the Chinle aquifers, major ion concentrations generally increased toward the river along the ground-water flow paths from NE to SW. Ground-waters samples were generally saturated with respect to calcite and quartz, but undersaturated with anhydrite, gypsum, and Si02. Trilinear diagrams defined mixed ion, Ca+Mg-HCO^-, and Na+K-HCCXf water-types. Data analysis and published literature suggested that cation-ion exchange of Na+ for Ca2+ and dissolution are important processes in water chemistry changes in the Alluvial and Chinle aquifers. Spearman rank correlation of selected chemical parameters to ion concentra tions and distance from sample location to the Puerco River, produced positive values, but few were large enough to suggest possible association. Significant correlation was observed for U and 226 Ra when paired with gross alpha and beta, TDS, HCO 3", and SO2-. Tritium analysis of 20 samples in the southeast part of the study area suggests that most ground water was more than 20 to 50 years old. Large spatial variations of 8 D and 8 180 in water samples suggest the ground-water system is complex and not easily explained with the small number of samples collected. However, regional radioactive occurrences and overall low correlation values suggested most elevated radioactivity in ground water was produced by natural sources and not by recharge water from the Puerco River. Table of Contents
ABSTRACT ...... iii LIST OF FIGURES ...... vi LIST OF TABLES...... viii LIST OF ABBREVIATIONS ...... ix ACKNOWLEDGMENTS ...... x
INTRODUCTION ...... 1 Purpose ...... 1 Objectives ...... 1 Historical Background ...... 2 Previous Works ...... 7
METHODOLOGY...... 10 Objective One ...... 10 Objective Tw o ...... 11 Objective Three ...... 12 Ground-water Sampling ...... 12 Laboratory Analysis ...... 16 Isotopic Analysis ...... 16 Literature Review and Database ...... 16
ENVIRONMENTAL SETTING ...... 18 Physiography ...... 18 Climate ...... 20 Vegetation and Soils ...... 22 Puerco River Basin ...... 24 Geology ...... 30 Stratigraphy ...... 30 Structure ...... 32 Geologic History ...... 32 Uranium Occurrence ...... 36
iv Hydrogeology ...... 40 Occurrence of Ground Water ...... 41 Hydrostratigraphy ...... 42 Ground-water Quality ...... 42
RESULTS AND DISCUSSION...... 48 Potentiometric Surface ...... 48 Ground-water Geochemistry ...... 50 General Ground-water Character ...... 50 Water Quality Standards ...... 52 Spatial Changes in Chemistry ...... 59 Geochemical Modeling ...... 68 Trilinear Diagrams ...... 69 Ground-water Radiochemistry ...... 76 Spatial Changes in Radiochemistry ...... 76 Trilinear Diagrams of Radioactive Water ...... 84 Statistical Correlation ...... 84 Environmental Isotopes ...... 88 Tritium Analyses ...... 88 Stable Isotope Analyses ...... 88
SUMMARY AND CONCLUSIONS ...... 94
FURTHER R ESEA RC H ...... 99
SELECTED REFERENCES ...... 102
APPENDICES ...... 110 A. Sample Biography ...... 110 B. Sample Location ...... 119 C. Total Chemistry Analyses ...... 132 D. Dissolved Chemistry Analyses ...... 137 E. Radiochemistry Analyses ...... 142 F. Radiochemistry Precision Variability ...... 147 G. Environmental Isotope Analyses ...... 150 H. Methods of Laboratory Analysis ...... 153 I. WATEQDR Output ...... 155
v LIST OF FIGURES
T itle P age
Little Colorado and Puerco River basins in the southern 3 Colorado Plateau region of Arizona and New Mexico.
Location of the New Lands and selected ranches in 6 northeastern Arizona.
Location of the study area in northeastern Arizona. 19
Black Creek tributary and major drainages in the western 26 Puerco River basin, Arizona.
Generalized stratigraphic section of sedimentary rocks in the 31 western Puerco River basin, Arizona.
Generalized geologic map of sedimentary rocks in the western 33 Puerco River basin, Arizona.
Regional structural elements that influenced the geologic his 35 tory of the Black Mesa basin.
Radioactive and uranium mineral occurrences in the Chinle 38 Formation in the Colorado Plateau region of northeastern Arizona.
Generalized, computer-generated, equipotential contour map 49 of the ground-water surface in the western Puerco River basin, Arizona.
Location and identification number of samples collected for 51 this investigation.
Location and identification number of samples collected by 53 Webb et al., 1987a,b.
Location and identification number of selected samples col 54 lected in the study area by previous investigators.
Sample TDS concentration (mg//) in the study area. 60
Sample HCO^- ion concentrations (mg//) in the study area. 61
Sample Ca2+ ion concentrations (mg//) in the study area. 62
vi Figure T itle Page
16 Sample Na+ ion concentrations (mg//) in the study area. 63
17 Sample SO |- ion concentrations (mg//) in the study area. 64
18 Sample Na:Ca ion ratios in the study area. 67
19 Trilinear diagram (% meq//) of ground-water samples from 70 the Alluvial aquifer.
20 Trilinear diagram (% meq//) of ground-water samples from 71 the Bidahochi aquifer.
21 Trilinea- diagram {% meq//) of ground-water samples from 72 the Chinle aquifer.
22 Modified trilinear diagram (% meq//) of water-types for geo 75 graphic areas.
23 Sample gross alpha and gross beta activities (pCi//) in the 77 study area.
24 Sample uranium ion concentrations {fJ-g/l) in the study area. 78
25 Dominant radioactive decay series of uranium-238. 79
26 pH-Eh diagram of the U-0 2-C 0 2-H20 system for; 25 ° C, 82 PCo2=10-2 atmosphere, and U concentration = 240 fxg/l.
27 Trilinear diagram (% meq//) of ground-water samples with 85 radioactivity above federal drinking water standards for gross alpha and gross beta.
28 Sample locations and tritium values (TU) of ground water 89 and the Puerco River in the study area.
29 Sample locations and 8T>/81S0 values ( °/oo) of ground 90 water, precipitation, and the Puerco River in the study area.
30 Stable isotope values of 8 lsO vs. 8 D ( °/oo) of ground water, 93 precipitation, and the Puerco River plotted with the Craig meteoric water line and the local meteoric water line.
31 Generalized diagram of a conceptual model illustrating the 97 hydrogeologic system in the study area.
vii LIST OF TABLES
Table Title P age
1 Chronological summary of major references and events that 28 document contamination of the Puerco River basin, Arizona- New Mexico.
2 Hydrostratigraphy of major aquifer units in the western 43 Puerco River basin, Arizona.
3 Summary statistics of major ion concentrations (mg//) for 55 aquifer units in the western Puerco River basin, Arizona.
4 Summary statistics of minor ion concentrations (mg//) for 55 ground water in the western Puerco River basin, Arizona.
5 Maximum contaminant levels (MCLs) and number of concen 57 trations in ground-water samples from the western Puerco River basin, Arizona that exceeded the MCL for selected inor ganic chemicals.
6 Secondary maximum contaminant levels (SMCLs) and 59 number of concentrations in ground-water samples from the western Puerco River basin, Arizona that exceeded the SMCL for selected inorganic chemicals.
7 Spearman rank correlation coefficient (r ) for uranium and 87 radium-226, and selected chemical species, TDS, and pH at the 0.05 significance level.
8 Correlation coefficient (r) for radiochemical parameters and 87 sample location distance to the Puerco River at the 0.05 significance level.
viii LIST OF ABBREVIATIONS cubic meters per day m3/day cubic meters per second m3/sec degrees Celsius °C delta deuterium 8 D delta oxygen-18 8 180 dissolved oxygen DO electrical conductivity EC hydrogen ion concentration pH kilometers per hour km /h r liters per minute // min maximum contaminant level MCL microsiemens per centimeter [iS/cm milliequivalents per liter m eq// milligrams per liter m g// micrograms per liter percent % per mil °/oo picocuries per liter pCi/Z redox potential Eh saturation index SI secondary maximum contaminant level SMCL square kilometers km 2 total dissolved solids TDS tritium units TU ACKNOWLEDGMENTS
The Navajo Nation Division of Water Resources (NNDWR) gave their con sent for the study and provided support for the collection of water samples and sample analysis. Carol Boughton, a former hydrologist with the Navajo Nation, is gratefully acknowledged for her contribution to this study. Thanks also to fellow workers of the NNDWR, the Navajo Tribal Utility Authority, and the
Navajo and Hopi Indian Relocation Commission. I am indebted to the commun ity of Sanders, Arizona for their permission to access water wells and collect samples.
This manuscript reflects months of drudgery under the guidance of my com mittee chairman, Dr. John Hess to whom I am grateful for his numerous ideas and critical review. Thanks also to the rest of my thesis committee, Dr. Steve
Mizell, Dr. Ernest Duebendorfer, and Dr. Gary Palmer for their participation in this work. Special appreciation goes to the Desert Research Institute, Water
Resources Center which supported my work with a graduate assistantship, the use of computer and office facilities to create this document, and a place to call home since this thesis was largely nonfunded.
I also acknowledge the Department of Geoscience and the Graduate Student
Association at the University of Nevada, Las Vegas; the American Geological
Institute; Lily and Wing Fong of Las Vegas; the Indian Health Service; and the
U.S. Geological Survey. I must also thank my parents for having patience and faith in their son that he would complete his goals in higher education. And last, but not least, thank you friends and fellow graduate students (past and present) for your support and understanding.
x 1
INTRODUCTION Purpose
The Puerco River has long been a subject of controversy over the problem of contaminated water from wells in the alluvial and bedrock aquifers along the river. Current residents of the western Puerco River basin in the Sanders,
Arizona area are concerned about the quality of ground water that they use for domestic and agricultural purposes. The anticipated increase in population in the area from the resettlement of Navajo Indians from the Hopi Partition Lands will necessitate further exploitation of ground-water resources. The environmen tal concerns of residents in the Sanders, Arizona area prompted an investigation to study the quality of ground water along the Puerco River. This investigation endeavored to: ( 1) characterize the ground-water quality, ( 2) identify areas of radioactive ground water, and (3) conceptualize the hydrogeologic system in the vicinity of Sanders, Arizona. The study was instituted by: the Navajo Nation
Division of Water Resources; the Desert Research Institute, Water Resources
Center, Las Vegas, Nevada; and the Department of Geoscience, University of
Nevada, Las Vegas in Las Vegas, Nevada.
O bjectives
The Navajo Nation Division of Water Resources, the Desert Research
Institute’s Water Resources Center, and the Department of Geoscience at the
University of Nevada, Las Vegas, proposed to study the hydrogeology and geo chemistry of ground water along the Puerco River in the Sanders, Arizona area.
The main objectives of this investigation are to: 2
1. Assemble ground-water chemistry data and relevant water well information in
the vicinity of Sanders, Arizona and construct a reliable data base for future
reference.
2. Characterize the ground-water quality of major aquifer units and identify areas
of possible radionuclide contamination along the Puerco River in the vicinity of
Sanders, Arizona.
3. Formulate a conceptual model of the hydrogeologic system that explains the
variation of ground-water quality along the Puerco River in the vicinity of
Sanders, Arizona.
Historical Background
This investigation focuses along the Puerco River which has been an impor tant source of water throughout the history of the arid region (Figure 1). The earliest people to frequent the Puerco River were the Anasazi Indians. The
Anasazi lived throughout a large section of what is now northeastern Arizona and northwestern New Mexico from about 950 AD to 1,200 AD (Canby, 1982).
The next group of people to inhabit the Puerco River area were the Apachean people. Apacheans were the southernmost group of Athabascan speaking Indi ans to have migrated across Asia to North America from 1,300 AD to 1,700 AD
(Goodman, 1982). One of the largest group of Apachean people was known as the Navajo.
The Spanish arrived with horse and sheep in the region during the late
1500’s AD and their tactics to control the New Mexico territory eventually forced another group of people to seek refuge in the area. Pueblo Indians from the Rio Grande Valley, New Mexico moved into the area during the early 1700’s 3
1
> 1. Little Little Colorado Plateau and Puerco region of Arizona River and basins New Mexico in (after the Goodman, southern 1982). Colorado m
u.v S3 #bO
M 4 and exerted a strong influence on the cultural evolution of the Navajos (Iverson, 1981).
The 1,700 AD to late 1,800 AD period was a time of more Anglo-American exploitation and control of the region (Goodman, 1982). In 1866 the Atlantic and Pacific Railroad was given permission to build a line along the 35th Parallel from Springfield, Missouri to the Pacific Ocean (Bailey and Bailey, 1986). The railroad was the economic base for the rapidly growing towns like Winslow in northeastern Arizona and Gallup in northwestern New Mexico.
The original Navajo Indian Reservation was established with the Treaty of
1868, but from the start the reservation was too small to accommodate the tribe
(Goodman, 1982). Competition for land between the Navajos and the white ranchers in the Little Colorado River Valley during the late 1800’s made the availability of water for stock an important factor to keep Navajo livestock grazing within reservation boundaries. The early attempts at the time to supply the Navajo with permanent water sources were the development of springs, reservoirs, windmills, and irrigation ditches within a 50 km radius of Fort
Defiance, Arizona (Bailey and Bailey, 1986).
The southern end of the Puerco River basin was first described by U.S.
Army expeditions in the late 1800’s for the abundance of fossilized wood in the landscape. By the early 1900’s, the locality had become world famous for some of the most prized specimens of fossilized forest debris. The importance of the area as a scientific, cultural, and scenic resource was recognized and the Petrified
Forest National Park was proclaimed in 1906 (Billingsley, 1985).
Historically, the basin has been examined and exploited for its mineral resources. In the early 1920’s, the area was prospected and tested for bleaching clay deposits at Allentown, Chambers, and Sanders (Kiersch, and Keller, 1955). 5
From 1925 to 1954 over four million metric tons of clay were mined in the area, and limited mining continues today in the open pits at the Cheto mine southeast of Sanders. The basin is situated within a region that was prospected for coal, uranium, oil, natural gas, and helium. From 1950 to 1976, helium gas was pro duced from three fields in the area south of Navajo, but the fields were aban doned due to decreasing reservoir pressure and low market prices (Agenbroad,
1985).
Completion of historic Highway 66 by the 1950’s opened up the Southwest to interstate travelers, and brought tourism to the small communities in the study area from Lupton to Navajo. In the 1970’s, Highway 66 was replaced with Interstate 40 and the amount of traffic greatly increased across the area.
Major employers in the area are the commercial businesses along 1-40, the Puerco
Unified School District at Sanders, the Cheto clay mine at Sanders, the silica sand quarry south of Houck, the Arizona vehicle inspection and weigh station at
Sanders, and the Arizona highway maintenance station at Chambers.
In 1980, over 120,000 hectares in the study area were selected by the Navajo
Nation for addition to the main Navajo Indian Reservation through the allowances of the Relocation Act; Public Law 93-531 (CH2M Hill, 1984). The study area is generally referred to as the "New Lands" which denotes the ranch land and communities that will become a new home to Navajo people who relo cate from the Hopi Partition Lands (Figure 2). Plans for the upgrading and con struction of facilities to support the needs of the growing community in the New
Lands is an ongoing enterprise. Provision for community services will necessitate further exploitation of areal water resources to support domestic and agricultural activities. 6
Kayonta Shlprock
A Tuba City N Kykotsm ovl
Ganado 0 acala In km 60 iiiiiiiiiiiiiiiiiiiii " " I
Flagstaff
Now L ands Holbrook
□ Nava|o Reservation P50i\ Hop! Reservation ^ Hopi Partition Lands
(enlarged view)
Cham bers / a
Navajo
NEW LANDS RANCH SYMBOLS BN = Bar-N C = Chambers F = Fitzgerald K = Kelsey R = Roberts S = Spurlock scale In km 25 W = Wallace
Figure 2. Location of the New Lands and selected ranches in northeastern Arizona (after CH2M Hill, 1984). 7
For over 20 years, the Puerco River was a conduit for the discharge and transport of uranium mine effluent from mines that operated near the headwa ters of the river in northwestern New Mexico (Gallaher and Cary, 1986). W ater
discharged into the Puerco River by uranium mining and milling operations was contaminated with high levels of radioactivity, metals, and trace elements.
Periods of active uranium mine operation produced a perennial stream of water that began near the Church Rock area of New Mexico and flowed over 160 km downstream into eastern Arizona where the river resumed its ephemeral nature.
The practice of using the Puerco River as a conduit for uranium mine effluent was given national attention when the United Nuclear Corporation
(UNC) uranium mine tailings pond at Church Rock failed in 1979 causing the largest volume release of radioactivity ever reported in the United States (Wei- mer et al., 1981; Shuey, 1986). This large volume of radioactive sediment and water flowed from the UNC mine in New Mexico to Chambers, Arizona before it infiltrated the alluvium. The UNC accident and many years of episodic tran sport of contaminated water and material along its reach has degraded the
Puerco River system to an undetermined extent.
Examination of ground-water quality in the Sanders, Arizona area by vari
ous groups have yielded interesting results. Water analyses show a large varia
tion in quality, and some waters are characterized by high levels of radionu
clides, trace elements, and dissolved solids. The wide variation in quality may
reflect natural conditions, and/or anthropogenic sources.
Previous Works
Previous works that support the achievement of the objectives of this inves
tigation are few in number and short in duration. Headwaters of the Puerco 8
River and the reach to Gallup, New Mexico have received closer study as a result of the UNC mine accident, however, ground water along the lower stretch of the river in Arizona has not been examined in detail. Numerous references address ing the ground-water contamination around the UNC mine and along the upper
Puerco were examined and cited where appropriate.
Vast amounts of literature are available dealing mostly with areal geology because of the proximity of the study area to major physiographic regions such as the Colorado Plateau, Black Mesa Basin, the Mogollon Slope, and the
Defiance Plateau. A comprehensive work on the geology of Black Mesa Basin was compiled by Anderson and Harshbarger (1958) for the New Mexico Geologi cal Society Ninth Field Conference.
A report on the occurrence of coal, oil, natural gas, helium, and uranium in
Arizona, was completed by Pierce et al. (1970). A descriptive report of all known, naturally anomalous radioactive occurrences in Arizona which includes locations around the study area was detailed by Scarborough (1981). Ranch land resource evaluation and economic potential in the area was completed by the Navajo Tribe (Nation) (1983), and Agenbroad (1983 and 1985).
Comprehensive hydrogeologic studies of the region that yield information for this investigation include Harrell and Eckel’s (1939) report which provides the earliest water chemistry from wells and springs in the study area. The report by AJkers (1964) on the geology and ground water of central Apache
County, Arizona provided useful geologic descriptions, well data, water chemis try, and a 1:125,000 scale geologic map of the lower half of the study area. The substantial work by Cooley et al. (1969) on the regional hydrogeology of the
Navajo and Hopi Indian Reservations provided excellent descriptions of areal stratigraphy, geology, aquifer descriptions, and a 1:125,000 scale geologic map of 9 the upper half of the study area. An investigation by Mann and Nemecek
(1983), which characterized ground water in southern Apache County and
located favorable areas for ground-water development, contributed important water chemistry and well data from numerous sites in the study area.
Following the 1979 UNC spill, wells along the Puerco River became suspect for contamination and monitoring efforts of wells in the study area were sporadic
and often did not include a complete major ion and radiochemical analysis for
collected samples. Concerns of the Arizona Department of Health Services
regarding the renewal of discharge permits for uranium mines along the Puerco
River in New Mexico led to the establishment of the Puerco River Working
Group in February 1985. The Puerco River Working Group addressed the
nature of water quality standards in New Mexico and Arizona, compiled existing water quality data for examination, collected new data in Arizona, and presented
a sediment loading model of Puerco River contaminants.
A brief examination of ground-water quality from 13 widely spaced loca
tions in and around the study area by Western Technologies (1986) revealed no
evidence of radiochemical contamination of ground water along the Puerco
River. A reconnaissance study by Webb et al. (1987a) of 15 alluvial water sam
ples failed to determine if a contaminant plume exists in the alluvium along the
Puerco River, although drinking water standards were exceeded in some samples. 10
METHODOLOGY Objective One
Ground-water chemistry data and relevant water well information in the vicinity of Sanders, Arizona were assembled and a computerized data base sys tem was constructed. Historical information was procured from the Navajo
Nation’s wells data base, published reports, and federal agencies. However, the information that pertained directly to the study area was limited in scope and detail. Many wells had no record of depth, screened interval, or water quality.
New information obtained from the inspection of water wells, measurement of field water chemistry during sample collection, and analyses of selected consti tuents in ground-water samples supplemented and expanded the data base incor porated into this investigation. Published literature was reviewed to correlate wells sampled in previous investigations with those of the current investigation.
The design of the data base noted well information, sample locations, and geo chemical data from previous efforts.
The computerized data base was constructed after the format of the Navajo
Nation wells data base using a data base management system. The data base contained biographical, geographical, chemical, and isotopical information from the sources mentioned above, in a framework that allowed ready correlation
between data records and fields through a unique sample number. The pub
lished version of the information contained in the data base forms the appen
dices of this report (Appendices A - G). 11
Objective Two
Characterization of ground-water quality of major aquifer units and
identification of areas of possible radionuclide contamination along the Puerco
River in the vicinity of Sanders, Arizona were determined through the collection
of water samples and examination of water quality. Examination of ground water quality was initiated by reconnaissance sampling of well and spring loca
tions throughout the Sanders area. Detailed sampling and elemental analysis of
ground water identified locations of poor ground-water quality and elevated
radioactivity. Circumstances were unfavorable for sampling on a quarterly schedule, and most sources were sampled only once during a 12 month period.
Field parameters (temperature, electrical conductivity or EC, and pH) of the
ground water were measured at the time of sample collection. Additional field
measurements of dissolved oxygen and bicarbonate were made as equipment
became available to measure these parameters.
Water quality was examined by comparison of individual constituents in the sample water with levels prescribed in federal regulations for drinking water
quality. Compliance with federal levels for selected constituents in drinking water are part of the regulation of a community water system. Most sources in
the study area fail to meet the criteria for a community water system, however,
they are treated as one in order to use federal drinking water standards in the
evaluation of their water quality. The definition of a community water system
and federal drinking water standards are described in the Code of Federal Regu
lations title 40, parts 141 and 143 (1988a,b). The regulations for public drinking
water supplies are administered by the Environmental Protection Agency (EPA)
as part of its responsibility to monitor the state of environs and protect the pub
lic health. Despite the inability of sources in the Sanders, Arizona area to 12 qualify as community water systems, many are used to supply drinking water on a private basis.
Objective 3
Observation of spatial changes in water chemistry, quantification of geo chemical data, and interpretations of the hydrogeologic system were used to for mulate a conceptual model that explains the variation of ground-water quality along the Puerco River in the vicinity of Sanders, Arizona. Interpretation of water chemistry and well data was performed using analytical and graphical techniques.
Computerized systems for statistics and graphics were used to compare ion concentrations, radioactivity, and isotopic chemistry between sample locations in the study area. Statistical treatment of the data determined the average, range, maximum, and minimum values for sample ion concentrations and radioactivity.
Relationships among chemical constituents were examined using comparison and correlation. A computer contouring program was used to produce a poten- tiometric contour map of the generalized ground-water surface in the study area.
Some ground-water samples were examined for selected geochemical properties using a computer speciation and saturation modeling . program called
WATEQDR (Bohm and Jacobson, 1981). Water quality diagrams after Piper
(1944) were used to categorize water by its "water-type". Isotopic analysis of hydrogen (H) and oxygen (O) were used to make inferences regarding type, sources, and age of ground water.
Ground-water Sampling
Water samples were collected from wells and springs in the study area dur ing the time periods: August 19-31, 1987; January 6-14, 1988; and August 8-11, 13
1988. Sampling protocol was based on the guidelines described by Wood (1976),
although some of his recommended procedures for determination of field parame ters of water chemistry were not followed exactly because of equipment shortage.
Windmills and wells were operated for at least 30 to 60 minutes prior to sampling to allow discharge of several well volumes and stabilization of tempera ture, pH, and EC. Windmills that were operating upon arrival for sampling were assumed to have already discharged several well volumes so further purging was not necessary. In some instances, windmills were left for afternoon sampling after observing their continuous operation from the mid-morning. Wells with submersible pumps and storage tanks were operated with open valves to force continuous operation of the pump and to prevent sampling of the water in the tank or well casing. Some springs were sampled by using a hand pump where they were developed. Other springs were sampled by bailing from the spring flow, storage pipe, or wooden timber-lined well.
Collection of samples and measurement of field parameters during August
1987 and January 1988 are different from those of August 1988. During the first and second sampling periods, equipment was not available for measurement of
DO and field alkalinity. Filtering apparatus was also not available so the sam ples were taken unfiltered. Samples from the January 1988 period (NL-21 to
NL-33) were lab filtered at the Barringer facility, and analyzed for total and dis solved concentrations. Three one-liter and one gallon samples of ground water were collected at each site. One liter was preserved with 2 mZ of sulfuric acid
(H2S04) for ammonia and nitrate analysis. One liter was preserved with 2 mZ of
nitric acid (HN03) for analysis of cations and minor elements. One liter was
unpreserved for analysis of anions. One gallon was unpreserved for analysis of
gross radioactivity and specific radionuclides. All cubitainers were rinsed with 14 sample water prior to use and filled with no air space. Cubitainers were sealed with Parafilm® or plastic wrap and plastic electrical tape.
Environmental isotope samples were collected at all locations of inorganic and radionuclide sampling. Samples of additional springs, precipitation, and
Puerco River surface flow were also collected for isotopic analysis. Only during the first period of sampling were samples taken for tritium ( 3H) analysis. Sam ples for deuterium ( 2H) and oxygen-18 ( 18 0) analysis were collected in 12 ml glass bottles with no air space. Samples for 3H analysis were collected in one liter glass bottles with no air space. Bottles were sealed with Parafilm® or or plastic wrap, and plastic electrical tape.
Field temperature and EC during the first and second sampling periods were measured using a YSI 33 S-C-T meter. Recommended EC standards for the YSI 33 S-C-T meter were not available at the Navajo Tribal Utility Author ity Laboratory (NTUA), so the meter was checked with NTUA standards and the measurements were correct. However, EC measurements for the first and second sampling periods are approximate values because of the inability to cali brate the YSI meter properly.
A LaMotte DHA-2 pH meter was used to measure field pH during the first and second sampling periods. Buffer standards of 4.0, 7.0, and 9.0 at the water temperature were used to calibrate the meter before and after each pH measure ment. If the pH check of the buffer varied by ± 0.05 pH units after the meas urement of ground-water pH, then the meter was recalibrated and the ground water pH was remeasured.
The third period of sampling involved the use of different and additional equipment. A Geotech 0.45 micron filter assembly and peristaltic pump was used to collect filtered samples. Two one-liter filtered samples and one gallon 15
filtered sample were collected at each site In addition to the unfiltered samples
collected in the manner described above. A filtered sample of one liter was
preserved with concentrated HN0 3 for dissolved cation analysis. Another
filtered sample of one liter filtered sample was preserved with H 2S 04 for dis solved nitrate analysis which eliminated the unfiltered liter with H 2S 0 4 preserva
tive. The one gallon filtered sample was collected for dissolved radionuclides.
Thus, the total number of samples collected at a single location during the third sampling period consisted of four liters and two gallons.
Dissolved oxygen was measured with a YSI 50 DO meter with a YSI 5791 submersible stirrer. The DO meter was zeroed with a sodium sulfite solution,
and calibrated with the proper correction value for the sample point altitude and
water temperature prior to use. Electrical conductance was measured with a
LaMotte DADH TDS-EC meter. The EC meter was calibrated NTUA buffer
standards of 500 and 1000 n S/cm at the temperature of the water prior to each
measurement and corrected to 25 ° C.
An Orion SA-250 automatic temperature compensating pH meter was used
to measure temperature and pH. The pH meter was calibrated with the same
method described earlier. The Orion pH meter was used in conjunction with a
Hach digital titrator and magnetic stirrer to perform field potentiometric alkalin
ity titrations. Titrations were taken down to a pH of approximately 3.5, and
the data were plotted to find the bicarbonate end point.
Samples for inorganic chemistry and radionuclide analysis were placed in
plastic coolers and shipped by bus to the Barringer facility in Golden, Colorado.
Samples for 3H analysis were shipped to the Desert Research Institute Water
Analysis Laboratory in Reno, Nevada. Samples for ^ and 180 analysis were 16 transported by car to the Desert Research Institute (DRI) Environmental Isotope Laboratory in Las Vegas, Nevada.
Laboratory Analysis
Determination of inorganic and radioactive parameters in water samples was performed by Barringer Laboratories according to the methodology specified largely in references EPA-600/4-79-020 and EPA-600/4-80-032. Documentation of Barringer’s standard operating procedures and quality assurance-quality con trol program is described by Zito and Blundell, (1988). The methodology and appropriate reference for each chemical assay used by Barringer is contained in Appendix H.
Isotopic Analysis
Water samples for 3H analysis were prepared for liquid scintillation count ing according to the enrichment method described by Johns (1975). Samples of
H were extracted as H gas following the uranium oxidation method described by
Friedmund (1953), and analyzed with a 3-60-HD Nuclide mass spectrometer for the 5D composition. Samples of O were prepared as carbon dioxide (C02) gas following the method described by Dugan et al. (1985), and analyzed with a
Finnigan-Matt Delta E mass spectrometer for the 8 lsO content.
Literature Review and Data Base
Communication via computer between systems of the Navajo Nation and
Desert Research Institute was not possible, so the system at DRI was used to construct a data base. A data base was created using the UNIFY Relational
Data Base Management System which is a Unix system produced by the Unify
Corporation. UNIFY is a menu-driven design that uses a structured query language (SQL) based on English keyword syntax to relate and manipulate data. 17
The data base was created to include records and fields similar to the format of the Navajo Nation wells data base.
Information comprising the data fields was obtained from published litera ture, the Navajo Nation wells data base, and from the field and lab work per formed for this investigation. Data base information was used in conjunction with graphics systems from PicSure, DI-3000, and AutoCAD to produce various figures. A report writer was used to produce tabular data in the appendices. 18
ENVIRONMENTAL SETTING Physiography
The study area is located along the southern margin of the Colorado Pla teau physiographic province in southern Apache County of northeast Arizona
(Figure 3). It is located between 1090 03’ and 109 ° 45’ west longitude and
35 0 00’ and 35 0 26’ north latitude. The area encompasses approximately 2,000 km from the New Mexico-Arizona border west to the Petrified Forest National
Park boundary, and includes part of the southeast section of the Navajo Indian
Reservation.
The Sanders area of the western Puerco River basin refers generally to the territory around the town of Sanders in the valley that trends diagonally northeast to southwest along a 75 km reach of the Puerco River in Arizona.
Land elevation in the area ranges from 2,100 m in the northeast part to 1,600 m in the southwest part. The Black Mesa basin occupies the west, north, and east sections of the study area. The Mogollon Slope occupies the southern section of the study area.
The Black Mesa basin is the central physiographic feature of the Colorado
Plateau. It has been described by Cooley (1958) as a broad circular trough 144 km across characterized by mesas, plateaus, and large broad valleys. Akers and
Harshbarger (1958) divided the Black Mesa basin into eight physiographic subdi visions. The two subdivisions of interest to this investigation are the Defiance
Plateau and the Painted Desert.
The Defiance Plateau forms the eastern part of the study area. It is a large oval upland 160 km long and 50 km wide. Sandstone rocks of the DeChelly 19
G anado Window Rock 264 AZ NM ______Church 1 Rock A oi"BT
3 5 ° 2 6 ’ m Gallup STUDY AREA'
at ro o Cham bers' o at
J osep h City Adamana Zunl 3 5 ° 0 0 ’ u r
Holbrook 'Petrified Forest National Park
LlJ
Hunt St. Johns
Figure 3. Location of the study area in northeastern Arizona. 20
(Coconino) and Chinle formations form a boundary of dip slopes and hogbacks around the plateau (Cooley et al., 1969). The southern portion of the Defiance
Plateau is cut deeply by a tributary of the Puerco River, Black Creek. The
Puerco River cuts across the southern toe of the Defiance Plateau at the
Arizona-New Mexico border.
The Painted Desert occupies the northwest, west, and southwest sections of the study area. It is an irregular, variegated landscape approximately 350 km in
length and 80 km in width. Landforms of the Painted Desert consist of eroded hogbacks, rock terraces, and gentle slopes carved in the Moenkopi, Chinle,
Moenave, and Kayenta Formations (Cooley, 1958). The Painted Desert gen erally spans the Little Colorado River Valley, however, it includes the Hopi
Buttes subunit of volcanic rock that borders the northwest corner of the study
area.
The Mogollon Slope occupies the extreme southern portion of the study area, and forms a gentle gradient 320 km long and 100 km wide along the south ern periphery of the Colorado Plateau (Kelley, 1958). It trends northwest- southeast and is comprised mostly of sandstone and siltstone units that have a prevailing northeast dip.
The sparsely populated communities in the study area from east to west are
Lupton, Allentown, Houck, Sanders, Chambers, and Navajo. The Lupton and
Houck communities represent the Navajo Nation system of government at the
chapter (local) level.
C lim ate
Climate for the western Puerco River basin is semiarid. Most months of
the year are generally dry except for late summer when heavy thunderstorms are 21
prevalent. The designated climate type for the northeastern region of Arizona is
a steppe-type climate (Goodman, 1982). A steppe climate characterizes a region where the annual amount of precipitation is greater than half of the annual
amount of potential loss of moisture by evaporation, and the twelve month aver
age temperature is 0 ° C or warmer. In this part of the Colorado Plateau, there
is a strong relation between elevation and annual precipitation. Lower elevations
(900-2,000 m) are usually dry, desert-like environments not subjected to extreme
temperatures during cold winters or hot summers. Higher elevations (2,000-
2,400 m) are more humid, have a greater annual temperature range, and are
marked by cold snowy winters.
This region of the Colorado Plateau is strongly affected by two important sources of moisture, the Gulf of Mexico and the Pacific Ocean. Southeasterly winds from tropical and subtropical areas of the Gulf of Mexico bring showers to
the study area during the summer months (Anderson, 1958). Western fronts from the Pacific Ocean produce a steady type of precipitation in the study area
during the winter months. The prevailing wind direction is southwesterly, and
the average wind velocity for hourly periods ranges from 7.7 km/hr to 24.5
km/hr (Cooley et al., 1969).
Summer precipitation usually occurs during convectional and frontal-
convectional storms in the form of isolated, brief, high energy periods of rainfall
(Cooley et al., 1969). Summer thunderstorms produce rapid runoff, flash floods,
high evaporation, and minor infiltration. Winter precipitation is able to
infiltrate and recharge ground water, because it occurs mostly from low energy
frontal storms that yield a more even distribution of moisture over a longer
period of time. 22
The average annual precipitation in the area is approximately 25 cm
although higher elevations like the Defiance Plateau may receive as much as 30
cm of precipitation a year. Nearby Petrified Forest National Park has an aver-
© age annual precipitation of 19 cm a year (Akers, 1964). Typically, July and
August are the wettest months, and May and June are the driest months. Rain
and snow can occur from late November to late March (CH2M Hill, 1984).
The average daily temperature for January in the southwestern part of the
study area (Pinta) is 0 ° C, and for July the average daily temperature is 240 C
(U.S. Department of Agriculture, 1981). Maximum daily temperatures during
the summer can be as high as 37 ° C in the lower elevations of the study area
(Cooley et al., 1969). The period of killing frost occurs from early October to
early May which gives an average growing season of 140 days (Akers, 1964;
CH2M Hill, 1984).
Vegetation and Soils
The western Puerco River basin is recognized as upper Sonoran zone except
for the Defiance Plateau which is designated as a Transition zone (Akers, 1964;
Goodman, 1982). Upper Sonoran zone covers most of northeastern Arizona
between a 1,200 to 2,100 m elevation, and it is represented by an mix of pinon
pine-juniper and grass-shrub types of vegetation (Anderson, 1958). The Defiance
Plateau part of the study area is considered Transition zone because the land is
between 2,100 to 2,400 m elevation, and it hosts ponderosa pine forest vegeta
tion (Anderson, 1958). In general, the kind and amount of vegetation in the
area is related to environmental factors like slope, precipitation, outcropping sed
imentary units, soils, and exposure (Hicks, 1969). 23
Major plants that characterize the Sonoran zone are pinon ( Pinus pon- derosa ), jumper ( Juniperus sp.), greasewood ( Sarcobatus vermiculatus), and sage brush {Artemisia sp.) (Hicks, 1969). Major plants of the Transition zone include pine, greasewood, and Douglas fir ( Pseudotsuga menziesit).
Drought resistant plants like greasewood, saltgrass {Distichlis stricta), and shadscale {A triplex confertifolia) grow in areas of sparse annual precipitation and lower elevation. Plants like alkali-sacaton ( Sporobolus airoides), Indian rice grass
{Oryzopsis hymenoides ), saltgrass {Distichlis stricta) are common in lower eleva tions where soils are alkaline and salty. Main rangeland grasses of the study area consist of alkali-sacaton, Indian rice grass, blue grama {Bouteloua gracilis), galleta {Hilaria jam esii), needle and thread {Stipa sp.), and dropseeds {Sporo bolus sp.) (CH2M Hill, 1984).
Phyreatophytes grow in areas of springs, seeps, and shallow ground water as well as along ephemeral stream channels throughout the area. Typical phyreatophytes of the region include cottonwood {Populus sp.), tamarisk
( Tamarix sp.), and willow {Salix sp.).
Pinon-juniper and grass vegetation of the Transition zone on the Defiance
Plateau is present where the soil is sandy to sandy loamy in composition. Com position of soils in the Sonoran zone of the study area ranges from loamy, sandy, and clayey loam to sandy, rocky, broken, and eroded badland. Parts of the study area have a large mantle of surficial deposits that consist of alluvial, ter race, and some eolian sediments. Alluvial deposits are usually permeable enough to support the growth of grass and browse since they will retain a sufficient amount of the annual precipitation. 24
Puerco River Basin
The western Puerco River basin is part of the entire Puerco River basin that includes territory in northwestern New Mexico and northeastern Arizona
(Figure 1). Total drainage area of the river basin is 7,500 km2. The western part of the basin in Arizona comprises approximately half of the basin’s total area (U.S. Army Eng. Report, 1984). The Puerco River is over 160 km long from its headwaters in New Mexico northeast of Gallup, to its junction with the
Little Colorado River near Holbrook, Arizona. The Little Colorado River is a main tributary of the Colorado River, the master stream of the Colorado Pla teau.
Entrenchment of the Colorado River system and its tributaries is best described by Cooley et al. (1969), and much of the following information is taken from their report. Erosional development of the Colorado River is divided into four general cycles: Valencia, Hopi Buttes-Zuni, Black Point, and Wupatki, based on the four respective erosional surfaces recognized in the geologic record of the Colorado Plateau. Erosion during late Cenozoic time superimposed the
Colorado River system on the Colorado Plateau. Development of the Little
Colorado system began during the Hopi Buttes-Zuni cycle and ended during the
Black Point and W upatki cycles.
Alluvial deposits vary in composition, thickness, and distribution. Terrace and alluvial deposits are scattered along the main part of the stream channel, and deposits may be separated by an unconformity caused by erosion (Cooley et a l, 1969). Alluvial deposits are composed primarily of interbedded and crossbedded sands, silts, clays, and gravels. Some deposits contain eolian beds of sand and fine-grained beds of carbonaceous material. 25
The Puerco River is an ephemeral stream with a normal average annual flow rate of less than 2 m3/sec. Erratic streamflow discharge measurements for the Puerco at the USGS gaging station at Chambers, Arizona have been over
400 m3/sec. Maximum discharge usually occurs during late summer in response to heavy thunderstorm surface runoff. When discharge is greater than 85 m3/sec, the Puerco River is loaded with sediments eroded from the bed and sides of the stream channel (Webb et al., 1987b). The river changed to a perennial stream during the times when the uranium mines were actively discharging waste water at Church Rock, New Mexico. Perennial flow continued across New
Mexico and well into Arizona as far as Chambers until mine dewatering activi ties stopped in 1986 (Shuey, 1986).
According to Aldis (1979), the Puerco is a losing stream in the upper basin except for the stretch from east to west Gallup, New Mexico. Discharge from the
Gallup sewage treatment plant on the west side of town helps the Puerco to change to a gaining stream. The Puerco returns to a losing stream again near the Arizona state line, although it does receive some minor recharge from smaller tributaries and bedrock seepage at certain times of the year. The entire river also loses a large amount of water to evaporation either directly from the water surface or indirectly through saturated stream bed sediments. The Black Creek tributary and nearby drainages that produce some recharge for the Puerco dur ing seasonal runoff events are shown in Figure 4.
The Puerco River follows a meandering course inside generally elongate channel walls 3 to 50 m high. The active river channel is usually less than one km wide. The gradient for the Puerco River as it crosses the 75 km stretch from the Arizona state line (1,900 m) to the Petrified Forest Park boundary (1,650 m) is approximately 3 m/km. The gradient for the upper basin east of Gallup, New
Mexico is approximately 9 m/km (U.S. Army Eng. Report, 1984). IS %£4-Chamb«ira M ^^^HvmSondfravv
IN D E X W AP
Saddle yyjt5®
Figure 4. Black Creek tributary and major drainages in the western Puerco River basin, Arizona. 27
o Water quality of the Puerco River basin is a matter of historic and current interest that has come to involve not only residents of the basin, but many regional, state, and federal groups as well. Most of these investigators have shown that there is usually some measure of contamination in stream channel sediments, high flow events, and shallow alluvial ground water for parts of the
basin (Table 1). It is widely agreed that the river basin water quality has been
affected by uranium mining and the 1979 UNC accident, but the extent of con
tamination, if any, is unknown. A comprehensive study of the occurrence and
movement of radionuclides and trace elements in the Puerco and Little Colorado
River basins is an ongoing investigation by the USGS, and information is being
made public on a yearly schedule (USGS written proposal, 1988).
A concise summary of radionuclide releases and water-quality investigations of the Puerco River basin is given by Webb et al. (1987b), and much of the fol
lowing information is from their report. Uranium mine effluent waters were
discharged periodically into the eastern Puerco River basin from the 1950’s through to February, 1986 when mine dewatering stopped. Discharge permits were required for the mines since 1969 under the National Pollution Discharge
Elimination System (NPDES), but the permits did little to control the effluent water quality. Shuey (1986) reported 63 violations of NPDES permit standards
between 1980 and 1983. In the 1970’s, the total discharge of contaminated
waste water from the uranium mines was about 16,000 m3/day (Kaufmann et
a l, 1976).
On July 16, 1979 the UNC tailings pond dam at Church Rock, New Mexico
failed and released over 900 metric tons of sediment and 3,500,000 m of3 liquid • •
into the Puerco River (Gallaher and Goad, 1981). The sediment and liquid mix
was characterized by high concentrations of radionuclides, trace elements, dis
solved solids, and low pH. Total concentration of uranium in the Puerco that 28
Table 1. Chronological summary of major references and events that document con tamination of the Puerco River basin, Arizona-New Mexico.
Date Document number Author(s) Information and/or events or source
1975 Report EPA 906/9-75- USEPA Progress report on contamination of potable ground water 002 Region VI in Grants-Bluewater area, Valencia County, NM. 1976 GROUNDWATER, vol. Kaufmann, Ground-water chemistry and quality impact from uranium 14., no. 5, Sept-Oct R.F. and oth mining and milling, Grants-Bluewater area, NM. 1976 ers 1979 July 16. 1979; Church United UNC uranium mine tailings pond failed releasing largest Rock, NM Nuclear Cor volume of radioactive material ever in US history into poration Puerco River basin (Shuey, 1982). (UNC) mine accident 1980 Arizona Department of Swanson, Report on AZ state investigation of sediment, surface Health Services E.K. water, and well water chemistry downstream in AZ after UNC mine accident. 1981 NUREG/CR-2449, Weimer, W.C. Statistical survey of radionuclide distribution in Puerco PNL-4122 and others River arroyo near UNC mine for plan to cleanup spilled material. 1982 MINE TALK, vol. 2, pg. Shuey, C. Gives attention to the long term effect of UNC accident on 10-26 Puerco River sediments and local ground water down stream of mine. 1983 NMSU WRRI Report Gallaher, Section on water quality problems in Puerco River as a 169, pg. 60-68, (08/83) B.M. result of mine dewatering at Church Rock, NM. 1984 NM Health & Environ Millard, J. Health and environmental evaluation of UNC mine ment Dept. Tech. and others accident. Report^ 92 p. 1986 The WORKBOOK, vol. Shuey, C. Environmental assessment of the Puerco River basin water DC, no. 1, pg. 1-10 quality shows violations of some standards and long term contamination hazard. 1986 Water Quality Study, AZ Dept. Results of 1985 sampling surface water along Puerco River Puerco River, AZ Health Ser in AZ-NM show pollution, high radioactivity, and heavy vices metals. 1986 NM Enviro. Improv. Gallaher, 1977-82 water sampling study shows impact of uranium Div„ GWH-86/2 B.M. and mining on surface and shallow ground water in Grants Cary, S.J. Mineral Belt area, NM. 1987 US Geological Survey, Webb, R.H. Water quality study of 15 alluvial ground water samples WRIR 87-4126 and others collected along the Puerco River in AZ showed some consti tuent concentrations exceed federal drinking water stan dards. 29 day was 6,900 picocuries per liter (pCi /I) uranium (Millard et al., 1984).
Measured activities of gross alpha in the river that day were 130,000 pCi/Z near
Church Rock and 26,000 to 40,000 pCi/Z at Gallup (Shuey, 1982).
Following the 1979 UNC accident, the surface water quality and shallow alluvial ground-water quality along the Puerco River were monitored sporadically for signs of contamination. A study by Gallaher and Cary (1986) showed some contamination of shallow alluvial wells along the Puerco in New
Mexico. Surface water samples taken in Arizona by the Arizona Department of
Health Services (Swanson, 1980) contained concentrations that exceeded levels for 25 Arizona water standards. Water samples of high surface flow collected in
July, 1986 from the Puerco near Lupton, Arizona exhibited gross alpha activities as high as 2,200 pCi/Z and gross beta activities as high as 2,100 pCi/Z (Shuey and Morgan, 1988). Combined gross alpha and gross beta activity of a sample collected from the Puerco River at Sanders, Arizona during a high flow event
(August 28, 1987) was 4,800 pCi/Z.
Recent studies of ground-water quality in the western Puerco River basin have not clarified the problem of suspected ground-water contamination.
Thirteen samples of ground water were collected and analyzed in 1985 by
Western Technologies, but only eight wells were located within three km of the
Puerco; and no sample revealed any elevated radioactivity. A more systematic study by Webb et al. (1987a and 1987b), which encompassed 15 samples of alluvial ground water, revealed a range of water quality, and some levels of contaminants exceeded federal drinking water standards. Samples of sediment and vegetation from transects along the Puerco River in Arizona revealed no elevated concentrations of radionuclides. Information from Webb’s study is contained in the section on "Hydrogeology" and in the appendices of this report. 30
G eology
The geology of the study area is described by Akers (1964), and Cooley et al. (1969), and the following description is based largely on their work. Basin geology is described simply as a horizontal sequence of sedimentary rocks rang ing in age from Pennsylvanian to Quaternary overlying a Precambrian crystal line basement. The sedimentary rocks have been subjected to numerous periods of erosion, and they generally thin eastward across the study area from the
Petrified Forest Park boundary to the Arizona-New Mexico state line. Jurassic and Cretaceous rocks are largely absent from the sequence except for small outcrops in the extreme eastern portion of the area.
Stratigraphy
The stratigraphy of rocks in the study area is complex because of lithologi- cal similarities, and the abundance of intraformational unconformities. Strati- graphic interpretation of the study area is based entirely on published literature.
Units generally consist of variegated sandstone, siltstone, and mudstone with minor conglomerate and limestone (Figure 5). The common minerals include quartz grains, argillaceous matter, and dark accessory minerals bonded together with a siliceous or calcareous cement. Various bedding configurations, channel deposits, gradational contacts, and interfingered units produced a complex arrangement of sedimentary rock in some sections. Irregular deposition and ero sion of the rocks in the study area has resulted in a sequence that varies in thickness and lithology from place to place.
The sequence of strata is reported to be from 363 to 454 m thick.
Occurrences of basement rock and deeper units like the Naco and the Supai For mations are known only from oil, gas, and mineral exploration wells drilled in the study area (Conley, 1977). 31
E r a P e r i o d R o c k Geologic D escription Quaternary Deposits Alluvial deposits occur along channel of Puerco River Ac tributaries. ® £ Alluvium: cross bedded eon da Ac gravels « / Interbedded silt Ac clay. Gravels grade up Into fines; some eollan sands near top of deposit. 2 c3 Gravels located in old stream valleys between ridges Ac spurs. 3 cJ Alluvium: width m few m to Ion. Thickness: 3 -6 0 m. o * O Terrace deposits: light gray to yellowish-gray sand, stlt, gravel beds. Terrace: 10 m above stream channel; thickness ■ less than IS m. h—1 __ _ O I p Bidahochi Formation N Formation consists of lower laouetrlne member Ac upper fluvlatlle member. O Upper member It yelowlah-gray argillaceous sandstone w / conglomerate Ac Calcareous sandstone In upper part. Some beds of white rhyoUllo ash. Ifembar Is oxidized red at Sanders Ac Red Hill. Thickness Is variable. c d WSS: Upper member: 138 m mas thickness SW of Daliancs Plateau. Blulfs W • r - 4 along Puerco River are 18 m to 48 m thick. h - j u Lower member la brown, pink, gray mudstone Ac argillaceous sandstone. Channel deposits of tuffaceous ash altered locally to bentonite olay. CD Iithology Ac color similar to Chinle because olaatio material eroded •* 77?% from lower unit has been redepoelled In lower member. Usually B-* conglomerate bads at base of member distinguish Bidahochi from Chinle. Lower member thins to south. Average thlokness In Puerco basin - 88 m. Chinle Formation ^ l l l l Formation consists of five members In western Puerco River basin. Members are similar In Iithology Ac structure. Color variegated: purple, red, brown to gray, green, orange. Mineralogy: quartz, clay, dark minerals, Jasper, chert, petrified wood. Rocks: sandstone, silts lone, mudstone, conglomerate. Struotures: lenticular beds, cross beds, graded beds, ohannel deposits. W S m Contacts are gradational. Intertongue, Ac not easy to recognize. Total W S 3 k %thickness In area Is about 420 m where erosion has not removed formation. sandstone. Intertongues w/ adjacent members. Variable thlokness. Thickness: 80 m at lupton. PETRIFIED FOREST MEMBER (u p p e r p e rt) : v arieg ated m u d sto n e, red slltsto n e. 1 ® sandstone, Bedding more extensive Ac natter than lower part. Thickness: 200 - 300 m In western Puerco River basin. o S0HSELA SANDSTONE BED : gray, purple, orange main sandstone bed w / h—< O minor mudstone Ac slltstone beds. May be eonglomeratlo Ac contain petrified wood. Variable thlokness Ac 48 m at Petrified Forest Park. o CO t s i CO i S S I S stones daystone w/ bentonite, petriued wood, uranium minerals. R N ? S r a * o cd Fluvial/shallow lacustrine deposits. Thickness: 121 m at Plnta. m MONITOR BUTTE MEMBER : (lower red member) variegated mudstone, sand- slone. conglomerate out mostly mudstone. Intertongues with adjacent M members. Thickness: IS - 108 m In Puerco River basin. S E- MESA RODONDO MEMBER : variegated conglomeratic Ban da tone between m s t sandstone Ac mudstone. Channel-type deposit. Thlokness: 0 m In area. SHINARUlfF. MRIffiER.: y ello w -g ray /o ran g o san d sto n e , m udetone. co n g lo m erate oonalaIs of ohannel depoelt network eroded Into Uoenkopt. Radioactive material w/ petrified wood. Thickness: 16 - 26 m In Puerco basin- e g g g g ^ g i l l l i l | l Moenkopi Formation Only Holbrook Member le present In area. Consists of yellowish-brown, reddish-brown, purple, gray-blue slltstone Ac mudstone. Very fine to medium-grained. Lentloular Ac wedge-ehaped beds of sandstone Ac conglo merate w/ gypsum Ac halite. Thickness: 38 - 80 m at Plnta.
o H 8 K 1 Coconino Formation h—1 fl Ught orange, white, fine to medium-grained, well sorted, oross-bedded O cd eollan sandstone. Usually silica cemented. Generally referred to as N • H j H H H DeChelly Ac Glorletta Sandstone In certain areas. Thickness: 80 m In O g In western Puerco River basin. W Supai Formation CD Pals red, reddish-brown mudetone, slltstone, sandstone, limestone w/ PRECAMBRIAN Precambrian Basement Figure 5. Generalized stratigraphic section of sedimentary rocks in the western Puerco River basin, Arizona (after Akers, 1964; Cooley et al., 1969; and Repenning et al., 1969). 32 S tru ctu re Most rocks are relatively undeformed, and there is a prevailing regional dip to the northeast. Bedding planes, on average, strike northwest-southeast, and individual dip measurements vary depending on proximity to a local structure. Faults and folds are present in the area, primarily on the Defiance Plateau and along its margin. Faults generally strike northeast and dip to the northwest. Folds generally trend north-south and plunge to the south or southwest. The general geology of the study area is presented in Figure 6. On the Defiance Plateau a monocline-anticline-monocline structure is present in the strata going from Lupton to Houck. Small synclines and anti clines occur in the center of the river valley from Sanders to Chambers. An anti cline and fault are present in the Pinta area and more faults may exist based on inferences made from oil and gas drilling logs (Dunlap, 1969). Faults in the sedi mentary strata are believed to have formed by reactivation of preexisting faults in the basement rock. The Tertiary and Quaternary rocks are generally unde formed and they cover underlying structures in older rocks in many parts of the area. Geologic History During the early Paleozoic Era, the western Puerco River basin was part of a stable shelf area situated between one geosyncline to the west and one to the northeast (Cooley et al., 1969). From the Paleozoic to middle Triassic time, sed imentation on the shelf area was controlled by the Cordilleran geosyncline. Dur ing Cretaceous time, it was controlled by the Rocky Mountain geosyncline. At the end of the Mesozoic Era, regional upwarping and orogenesis destroyed the Rocky Mountain geosyncline. The area of the geosyncline became the site of 33 EXPLANATION INDEX MAP Defiance Plateau :*• Qal v.' Quaternary alhiTjura Tertiary Bidahochi Fm (with younger sediment -«) Tnassic Chinle Fm (without Shioarump) Triassic Moenkopi Fm iillTrmlii (vitb Trc Shln&nimp) ;SsSjpcs*s Penm an Coconino Fm * ftfiUcUM Sanders 0 scale , , n km „ 5 7777?T7 lupton V'.Qal-.VlL X i uereo Rive ouck Chombors S a n d e rs V////////M Figure 6. Generalized geologic map of sedimentary rocks in the western Puerco River basin, Arizona (after Wilson et al., 1960 and Cooley et a l, 1969). 34 smaller structural basins, which were centers of depostion during Cenozoic time. Major features that influenced the geologic history of the area are shown in Figure 7. In the early to middle Paleozoic, the shelf area was encroached by seas from the Cordilleran geosyncline. Several thousand meters of deposits accumulated across the shelf and generally, thin eastward. During the late Paleozoic and early Triassic, the Uncompahgre Highlands in ancestral southwest Colorado supplied sediments to the shelf. A structural trough that developed prior to the deposition of Mesozoic strata was the Tusayan Downwarp of Gregory (1917). The Mogollon Highlands to the south were a source of sediment to the shelf area during much of the Mesozoic Era. From late Pennsylvanian and early Permian time, the shelf area was subjected to changing sea levels and deposition of sediment eroded from the highlands. The Pennsylvanian Naco Formation and the Pennsylvanian-Permian Supai Formation are characterized by marine, evaporite, tidal, eolian, and interbedded shallow marine and red bed deposits (Havenor and Pye, 1958). By middle Permian time, drier conditions on the shelf resulted in the deposition of the eolian Coconino Formation. The early Mesozoic was marked by vigorous erosion of the Mogollon Highlands. Sediment from the highlands was deposited in very still waters on the shelf area, which produced the mudstone and shale layers of the Moenkopi Formation. By early to middle Triassic time, general erosion of regional highlands continued and stream channels were eroded into the Moenkopi Formation. Additional uplift of the Mogollon Rim occurred at this time also. In middle to late Triassic time, the Cordilleran geosyncline was elevated to form a barrier to fluvial systems flowing northwest across the shelf. Reduced water 35 INDEX MAP NV CO CA Ar«a Mogollon Hlghtoi da AZ NM UT CO 0 km 2 5 0 AZ NM San Juan Basin Black Mesa Basin (L a ra m ld e ) -O STUDY AREA to 7 5 scale in km Iihiiiiiiiiiii Figure 7. Regional structural elements that influenced the geologic history of the Black Mesa basin (after Kelley, 1958; Akers, 1964; and Cooley et al., 1969). 36 velocities at the time resulted in the deposition of sands, silts, and muds of the Chinle Formation on the eroded surface of the Moenkopi. Late Triassic and early Jurassic structural changes in the southwest United States further uplifted the Cordilleran geosyncline. Mogollon Highlands continued to erode and furnish sediment northwest across the southern Colorado Plateau region. Early Cretaceous time was characterized by uplift, erosion, and tilting of older deposits. Mid Cretaceous seas advanced and retreated from the northeast. By the end of the Cretaceous, marine waters had retreated from the area for the last time. Erosion of nearby highlands and subsequent deposition in lowland areas continued in the beginning of the Tertiary. By late Miocene time, the southern Colorado Plateau region was host to an extensive lake system in which the lower member of the Bidahochi Formation was deposited. The upper member of the Bidahochi was deposited in the Pliocene by a fluvial system whose drainage pattern later developed into the Little Colorado River drainage. Succeeding cycles of erosion and planation in the region lasted from the late Pliocene to the late Pleistocene. Erosion initiated the early configuration of the Puerco River basin and all other tributaries of the Little Colorado River system. Quaternary fluvial action continued erosion and formed alluvial deposits that further defined the present morphology Uranium Occurrence Most uranium deposits in northeastern Arizona occur in Triassic and Jurassic sedimentary rocks. Deposits are usually located along the boundaries of major structural features in the Colorado Plateau region (Birdseye, 1958). Uranium occurs in the Jurassic Morrison Formation in the Carrizo and 37 Lukachukai Mountains, and at the northern end of the Defiance Uplift. It also occurs in the Triassic Chinle Formation along the southern part of the Monument Upwarp, and mostly along the western and southern margin of the Black Mesa basin (Figure 8). The uranium deposits in these units are preferentially referred to as "western-states-type uranium mineralization" because of the area and type recognition (Rackley, 1976). Generally, the uranium deposits are considered to result from processes involving oxidation, mobilization, reduction, and precipitation of ore minerals from ground-water solutions in a sandstone-host rock. Deposits in the Chinle Formation are given closer examination because of their relevance to the objectives of this investigation. Early interest in the occurrence of uranium in the Colorado Plateau region began in the late 1940’s and 1950’s when the United States started to use nuclear fission as a new source of energy. Mining of uranium in the region was quite productive in numerous areas at one time or another, but many ore deposits were small or low grade and have since been mined out or abandoned. Even many mines with large economic deposits have stopped operating from lack of public support for the nuclear industry and poor market prices for domestic uranium. Over one million metric tons of uranium ore have been mined from the Chinle Formation in Arizona (Pierce et a l, 1970). Uranium mineralization occurs mostly in old stream channel deposits of the Shinarump Member and the Petrified Forest Member. Ore is usually found in abrupt depressions in the stream channel or at places where the stream channel changed direction (Bollin and Kerr, 1958). 38 Monument Upwarp K a y e n ta Black Mesa Basin C h im e T u b a C ity K y k o tsm o v i C a m e r P Ganado"^3o S a n d e rs F la g s ta ff W inslow H o lb ro o k S t J o n n s 0 scale , In . km 5 ■ 0 Radioactive & U-mineral occurrence Figure 8. Radioactive and uranium mineral occurrences in the Chinle Forma tion in the Colorado Plateau region of northeastern Arizona (after Birdseye, 1958 and Scarborough, 1981). 39 Along the southern end of the Monument Upwarp in Monument Valley, channels eroded into the underlying Moenkopi and DeChelly Formations are filled with fluvial sediments of the Shinarump Member. The sediments consist generally of conglomeratic sandstone that were deposited with carbonaceous material, which later reacted with mineralized ground-water solutions to precipitate uranium and other metals. Detailed studies by Witkind and Thaden (1963) of the Monument Valley mining district show that the dimensions of the deposits vary significantly, however, the mineralization conforms generally with paleochannel directions. In the Cameron, Little Colorado River Valley, and Chinle Valley districts described by Pierce et al. (1970), the uranium deposits are located in the Shinarump and Petrified Forest Members. Occurrence of uranium in the Cameron area is confined mostly to old stream channel sediments. Uranium mineralogy in the Cameron area is more complex than the typical western- states-type uranium deposit because remobilization of some of the ore has occurred through oxidation, solution, and redeposition. The ore consists of secondary uranium-vanadium minerals filling pore spaces in the sandstone and in petrified logs. Most ore bodies show an alteration halo of gray sandstone bleached yellow from oxidation of sulfide minerals (Austin, 1964; Chenoweth and Malan, 1973). The Little Colorado River Valley district extends east from Cameron to the New Mexico border in southern Apache County. It includes the western margin of the study area. Uranium occurs in the lower to middle section of the Petrified Forest Member in the area near Cameron, and in the middle section of the Sonsela Sandstone Bed in the eastern area (Pierce et al., 1970). Mineralized deposits are found generally in sandy zones of shallow scours where the rocks have been altered, bleached, and iron stained. An impermeable layer of white 40 bentonitic clay usually occurs below most deposits. Deposits also contain associated carbonaceous material and petrified wood. Amounts of uranium ore produced from the Little Colorado area have been small, and only the locality on the west side of the Petrified Forest National Park produced enough ore for commercial shipment. Minor occurrences of uranium in the Chinle Formation have been documented in the Chinle Valley district which is located between the Black Mesa basin to the west and the Defiance Plateau to the east. The Petrified Forest Member is the host rock for the mineralization which occurs as disseminations, fracture fillings, and small, concentrated pods in lenses of carbonaceous material. No uranium ore has been produced from this area because the deposits are low grade. Uranium occurrence and ore production data in mining districts in Arizona have been compiled by the Atomic Energy Commission (AEC), by the USGS, and by the Department of Energy (DOE) for the National Uranium Resource (NURE) program (Scarborough, 1981). All known locations of uranium mineralization or naturally anomalous radioactive occurrences in Arizona that are twice the background radioactivity and greater, have been documented. The work by Scarborough (1981) summarizes the 965 radioactive occurrences in Arizona, and maps from his report were used to construct the map of uranium occurrences in Figure 8. Hydrogeology The hydrogeology in the study area is examined by describing major features of the hydrologic system that have a role in the occurrence and movement of ground water. Important considerations for understanding this system include not only the location, but the occurrence of ground water, 41 hydrostratigraphy, and ground-water quality. The study area is located in part of the Little Colorado River hydrologic basin which is a sub-basin of the larger Black Mesa hydrologic basin of northeastern Arizona. Black Mesa basin is bordered along its southern margin by recharge areas from the Defiance and Zuni Plateaus, and the Mogollon Slope-White Mountains territory (Akers, 1964). These areas serve as orographic barriers to precipitation for ground-water recharge. Generally, ground water moves downgradient from these topographically higher areas, through the Puerco basin, and to the west and northwest toward the Colorado River. Since the study area is part of the arid Colorado Plateau, it receives most recharge during the months of December to April when evaporation rates are low and precipitation infiltrates the saturated zone. Occurrence of Ground W ater Ground water occurs in permeable strata under both confined and unconfined conditions throughout most of the area. However, in the western part of the study area, where badlands dominate the landscape, there is a thick unsaturated zone. In some locations, old erosional surfaces concentrate ground water in an irregular manner making it difficult to locate productive wells (Mann and Nemecek, 1983). Springs and seeps are quite common, but their low yield limits development to livestock and private usage. Most springs are considered contact-type gravity springs, where water moving along an impermeable layer intersects the land surface and discharges (Cooley et al., 1969). Places of shallow ground water in the alluvial and bedrock aquifers are often indicated by the presence of a windmill. However, deeper aquifers or some alluvial wells are, in some cases, the reliable producers for high yield wells. 42 Hydrostratigraphy The major hydrostratigraphic units emphasized in this investigation are the Moenkopi, Chinle, and Bidahochi Formations; and the Quaternary deposits and alluvium which are referred to collectively as just "alluvium", or for this study as the "Alluvial aquifer". The regional scarcity of economic quantities of ground water has limited the number and location of wells, and subsequent hydrostratigraphic information available for these units is limited in the study area. Wells of higher yield (> 1,000 l/m \n) typically produce from the Alluvium along the Puerco River. Lower yield wells (<40 //min) produce from the Bidahochi and Chinle Formations. Wells are not known to produce from the Supai or Coconino Formations in the study area, however, the Tegakwitha Mission well near Houck was reported to produce from the Coconino (Harrell and Eckels, 1939). Hydrostratigraphic data summarized in Table 2 were taken from reports describing aquifer properties and well data in the western Puerco River basin. Well information is also contained in Appendices A and B. Geologic formations that comprise the aquifer units of the ground-water system in the river basin are considered anisotropic and heterogeneous. Ground-water Quality Ground water in the basin ranges from fresh, total dissolved solids (TDS) < 1,000 milligrams per liter (mg//) to brackish, TDS > 1,000 mg//, and it contains variable amounts of soluble minerals and trace elements. Quality is strongly related to lithology, and in general, the water quality difference between aquifers is more evident than changes of quality within a single aquifer (Akers, 1964). For most of the Black Mesa basin, ground water is either a calcium (Ca2+)- or sodium (Na+)-bicarbonate (HCO^~) type containing small to large 43 Table 2. Hydrostratigraphy of aquifer units in the western Puerco River basin, Arizona. Data summarized from reports by Akers, 1004; Cooley et al., I960; Mann and Nemecek, 1083; and Agenbroad, 1083. Hydro Lithology Hydrologic Well strati and unit and yield Remarks graphic depth to in thickness unit water //min A lluvial Mostly alluvium, terrace Aquifer 75- Alluvium present along Puerco Aquifer deposits, & (unconfined 1,900. stream channel, flood plains, & unconsolidated & confined) tributary drainages. Terrace sediments. Interbedded deposits present above stream 0-70 m. & graded sands, silts, channel. Unconsolidated sediments clays, & gravels. 0-70 on old erosional surfaces. Perched m. water zones. Shallow wells (< 4 m deep) may dry up. Wells > 30 m deep are more productive. Water quality is good to poor & reflects a mix from local recharRe sources. B idahochi Upper member: fluvial Aquifer 20-60 & May include Mancos Shale, Dakota A quifer elastics, sandstone, (unconfined) 150- Sandstone, or Wingate Sandstone in conglomerate; 15-100 m. 0-190 m. 380. places. Ground-water flow & Lower member: occurrence controlled by subsurface lacustrine deposits, clays structure. Contact springs & seeps; in paleochannels, perched water zones; and small sandstone, mudstone; isolated recharge basins are common. 65 m. 0-300 m overall Clays may be trouble during well unit thickness. construction. Water quality is good to excellent. C hinle Fluvial elastics, Aquifer- 0-20 & Complex lithology causes range in Aquifer interbedded sandstone, aquiclude 40-190. hydraulic character. Shinarump siltstone, mudstone, (confined & Mbr is good producer for springs & conglomerate, channel small wells. Monitor Butte Mbr is a deposits, lenticular unconfined) (?) producer for springs along Black bedding. Most 0-200 m. Creek. Sonsela Ss occupies productive members in paleostream channel deposits at Puerco basin are Lupton & Petrified Forest. Spurlock Petrified Forest Mbr reports high yield at 380 f/min. (Sonsela Ss) and Clays may be trouble during well Shinarump Mbr. 0-400 construction. Water quality is good m. to poor. M oenkopi Siltstone and mudstone. Aquiclude 0-20. Mostly impermeable & poor A quiclude 0-120 m. (confined) producer of water, if any. Water 200-400 m. quality is very poor. 44 amounts of TDS (Cooley et al., 1969). Highly mineralized water is often a Na+- Ca2+-HCO;f-sulfate (SO2-) water-type. Some water is high in minor constituents like iron (Fe), manganese (Mn), and nitrate (N03-). Naturally high concentrations of trace elements like arsenic (As), fluoride (F), and uranium (U) occur regionally in ground water. Cooley et al. (1969) reported th at most water with less than 700 mg /1 TDS is either a Ca2+- or Na+-HC03- water-type. Water with over 700 mg// TDS is usually a Ca2+- or Na+-S 02- water. Cooley also reported values for major ions in ground water. Average HC03- concentration ranges from 50 to 300 mg//, or higher in some sources. Sulfate concentration often exceeds 200 mg//, and scattered regional locations of ground water contain over 1,000 mg// of chloride (Cl- ) ions. Calcium, magnesium (Mg2+) and Na+, generally each have a concentration of less than 300 mg//. Calcium is highest in recharge waters. Generally, the Na+:Ca2+ ratio increases down gradient along ground-water flow paths in the basin. Ground-water quality in the Moenkopi Formation is poor because it is often too highly mineralized for economic use. Five water samples from wells in the Moenkopi contained concentrations of TDS ranging from 700 to 6,100 mg// (Mann and Nemecek, 1983). Quality in the Chinle Formation is variable because TDS can range from 200 to 8,300 mg//. One well in the Chinle was reported to have an EC of over 100.000 microsiemens per centimeter (ftS/cm), which indicates a TDS of about 60.000 mg//. The Shinarump Member and the Sonsela Sandstone beds of the Chinle produce good quality water in certain areas. The Shinarump contains excellent quality water in gravel beds that receive recharge from the Defiance Plateau. Shinarump units along the Puerco River generally contain less than 45 1,000 mg// TDS. The Sonsela Sandstone Bed is considered a producer of good quality water in areas along the Puerco when it can be found in the subsurface. The Bidahochi Formation contains generally good quality water which ranges from about 200 to 400 mg// in TDS for wells in the Puerco River area (Mann and Nemecek, 1983). Twenty-four water samples had an average of 230 mg// TDS, and were mainly a Na+-Ca2+-HCO;f water-type. Ground-water quality in the Alluvial aquifer is variable due to high concentrations of dissolved Na+, Ca2+, HCCtf, SO2-, and Cl- ions. The TDS ranges from about 200 to 3,400 mg//, and averages 1,000 mg//. Early geochemical data of Alluvial ground water along the Puerco reports 750 mg// TDS, 40 mg// Cl- , and 280 mg// SO2- (Harrell and Eckel, 1939). Mann and Nemecek (1983) attribute the wide range in Alluvial water quality to: (1) variation in surface water runoff quality; (2) hydraulic interconnection with adjacent aquifers; (3) evapotranspiration; and (4) variation in lithology. Concentrations of trace elements and radionuclides in surface and ground water in the basin for the 1975-1986 period have exceeded federal water standards several times (Webb et al., 1987). Natural conditions and mining discharges may constitute the sources of the elevated concentrations. Sampling of surface water quality of Black Creek by the Arizona Department of Health Services (Technical Committee of the Puerco River Working Group,1986) showed no violations of Arizona standards for trace elements and radionuclides. Median values of 8.0 )Ug//U and 0.1 pCi// radium (Ra) were reported as regional concentrations in ground water by Scott and Barker (1962). Statewide averages from 650 samples of Arizona well, surface, and treated water revealed 4.9 pCi// gross alpha, 6.4 pCi// gross beta, and 0.2 pCi//Ra (Thompson et al., 1978). 46 Webb et al. (1987b) examined concentrations of major ions, trace elements, and radionuclides from 15 samples of Alluvial ground water along the Puerco River. Water quality was characterized by high levels of TDS, SO|~, and Mn. Concentrations of trace elements were low, and activities of radionuclides were variable. Sample median values included 698 mg /I for TDS, 27 pC i// for gross alpha, 6 pCi fl for gross beta, 19.0 [J ig /1 for U, and 0.2 pCi /I for Ra. Uranium was the major alpha emitter in ground water. Radium-226 (226 Ra) plus radium-228 (228 Ra) activities were low despite high values of these isotopes in surface waters that are suspected to contribute some recharge water to Alluvial aquifer water. The sum of the measured radionuclide activities compared to the sum of gross alpha plus gross beta activity for each sample accounted for as little as 20% to as much as 84 % of the total radioactivity. Differences between measured radionuclide activities and total radioactivity were attributed to measurement error of total radioactivity and different methods of determining specific radionuclide activities. Beta-emitting isotopes including bismuth (Bi), lead (Pb), thorium (Th), and others were not measured. Three replicate samples from the Sanders School well (A-21-28-13cbc01) displayed similar concentrations of common ions, but radionuclide activities varied considerably. Gross alpha activity ranged from 16 to 29 pCi//, whereas gross beta activity was consistent at 6 pCi//. Webb et al. attributed the discrepancy to the use of unfiltered samples for some radiochemical analyses. Principal component analysis for distinct classes of water quality based on selected constituents of strontium (Sr), SO2-, U, and pH were inconclusive. Examination of radionuclide activities based on the distance of the well to the Puerco River revealed no evidence for a direct relation. Highest radionuclide 47 activities were not necessarily those wells closest to the river. The absence of extreme variation between sample radionuclide activities along the reach of the river from Lupton to Pinta, indicated contamination in the Alluvial aquifer is not related to the distance of sampling sites to headwaters of the river. Historical variations in ground-water quality for some Alluvial wells reflected a variation of recharge water quality within the basin. Sorption processes and complexation between ground water, surface water, and clay material may reduce the radioactivity of recharge water before reaching the Alluvial aquifer. Computer modeling of solution-equilibrium reactions to test if uranium minerals would precipitate out of Alluvial ground water of average composition produced negative values (no precipitation). Model concentrations of U increased to the average surface water value (0.10 mg//) and to the highest ground water value (0.36 mg//) yielded negative results. Sorption processes including ion exchange and adsorption are potential mechanisms for decreasing radionuclides in water, but no tests for these processes were performed in the study. 48 RESULTS AND DISCUSSION Potentiometric Surface An equipotential contour map suggested ground water in the study area flows generally from northeast to southwest (Figure 9). Data points from the Alluvial, Bidahochi, and Chinle aquifers were grouped together into a single file which was used by a computer to create equipotential lines representing a single hydrostratigraphic unit. Grouping of data from separate aquifers into a single file representing one aquifer was done because, water level measurements were sparse and only an approximation of the potentiometric surface was desired. Despite the general nature of the diagram, inferences about the ground-water flow system were made with reference to local topography and geologic struc tures. 0 Closely-spaced contours along the edge of the Defiance Plateau indicate a steep gradient, which suggests ground water flows southwest and south toward the Puerco River. In other parts of the map, however, widely-spaced contours indicate the gradient is less, and ground water flows in west or southwest direc tions. Exact losing and gaining sections of the river were not considered or determined because of the generalized nature of the contour map. The contour map was inaccurate in areas where the water surface elevation was higher than the land surface elevation. This is a result of grouping water level data from separate aquifers into a single plot file, which produced a diagram representing confined and unconfined systems. 49 EXPLANATION INOEX MAP Defiance ground water P l a t e a u flow directio • dato point SCALE in KM 0 v^Purrco Rive ou ck Sondara Figure 9. Generalized computer-generated equipotential contour map of the ground-water surface in the western Puerco River basin, Arizona (contour interval = 30 m). 50 Parts of the map displayed contour patterns which suggested mixing of ground water from different areas. In the areas north and south of the Puerco River between Chambers and Sanders, contours suggest a complex flow system where ground water may mix with water from other sources, including underflow from the river. A circular area of depression and mixing was displayed in the vicinity of Houck, which could reflect heavy pumpage by ground-water wells in this area. Equipotential contours suggest a resemblance to contour maps constructed by Akers (1964), Mann and Nemecek (1983), and CH2M Hill (1986). Com parison of the potentiometric surface with structural contour maps of the Coconino Formation, Sonsela Sandstone, and Bidahochi Formation suggested that subsurface structure may influence the shape of the water table in parts of the area. Faults described by Dunlap (1969) and emphasized by CH2M Hill may control, to some unknown extent, the flow of water through the area south of the river between Sanders and Chambers. Fault systems in the Defiance Plateau may influence ground-water flow near Sanders and Houck. Ground-water Geochemistry General Ground-water Character Geochemical information acquired through field work and from results of sample analyses were examined to evaluate ground-water chemistry in the study area. Forty-three samples were collected and analyzed. Sample locations and numbers (NLrOO) are shown in Figure 10. Nine springs, and 26 wells were sam pled. Seven samples were repeats from previous locations. One sample (NL-11), was a river sample collected during high flow. 51 EXPLANATION NDEX MAP WUH NL24 O s p rin g NL21 NL23 $ ° NL25.43 NL28 O NL30 SCALE In KM NL27 I NL29 NL22.40 NL26.41 NL 1 Tv NL1 6,33,38 NL44 NL1 1 (river) NL35 NL42 B NL15 NL36 NL31 .37 NL1 8 NL32.39 NL20 /9H-NL19 NL 1 4 O NL 1 3 NL05 NL04 O NL08 NL06 0 (a NL 1 2 NL07 NL01 © NL09 Lupton NL 1 0 O^Puereo R»v« Sondart O NL02 NL03 Figure 10. Location and identification number of samples collected for this investigation. 52 Analyses from published literature that provided supplemental geochemical data for trilinear diagrams are described in Appendices A - F, and their sample number and location are shown in Figures 11 and 12. Fifteen samples from Webb et al. (1987b) are identified with the "USGS" prefix. Thirty-five samples from Mann and Nemecek (1983) are identified with "QAL", "TBD", and "TRC" prefixes. One sample from CH2M Hill (1987) is identified with a TBD prefix. Two samples from the Indian Health Service, three samples from the 1986 Western Technologies report, and and 11 samples from the 1939 report by Har rell and Eckel are identified with "IHS", "WT", and "HE" prefixes, respectively. Summary statistics of chemical species from samples representing the three main aquifers in the study area are shown in Tables 3 and 4. Individual sample analyses and chemical parameters are listed in Appendices A - F. Concentra tions of major ions are similar values reported in previous investigations of water quality in the Puerco River basin. Sample minor constituents and trace elements were observed in low concentrations and typically averaged < 1.0 mg//. Generally, Alluvial and Chinle aquifers displayed a wider range of chemical constituents than did the Bidahochi aquifer. Dissolved solids content ranged from < 1,000 mg// (fresh water) to > 1,000 mg// (brackish water). High con centrations of Ca2+ and Mg2+ in most samples categorized most ground water as "hard" water. Hardness was higher in the Alluvial aquifer than in the Chinle and Bidahochi aquifers. W ater Quality Standards Water samples were evaluated with respect to federal regulations for drink ing water quality. The regulations are promulgated by the EPA in accordance with the allowances of the 1974 Safe Drinking Water Act (SDWA). Drinking water regulations are defined in the National Interim Primary Drinking Water Figure 11. Location and identification number of samples collected by Webb Webb by collected samples of number identification and Location 11. Figure 31* 58’ 109*50’ 3ft * 00 "I• io eter kilom ■ - -■ f AiUm>r>* al., 1987a,b. USGS 1USGS j USGS1 USGS12 A USGS11 USGS1O INDEX MAP uer ver y y ry e lv R o re e ’u I / ' Sanders s r t b m o i t C lo a v a N andars S Luplon USGS02 USGS01 USGS01 EXPLANATION CL I KM In SCALE ng in r p s USG^03 ndmill 4 53 et NEW M E X I C O 54 INOtX HAP EXPLANATION w indm ill AZ s p rin g TRC04 TBD 1 0 TBD 16$, TBD 14 TRCOI HE09 OTRC05 TBD1 1 TBD04 TBD08 TBD05 QAL01 TBD07 TBD 13 TRC03 HE 1 1 Kl QAL02 TBD01 ©TBD03 QAL03 TBD02 Figure 12. Location and identification number of selected samples collected in the study area by previous investigators. 55 Table 3. Summary statistics of pH and major ion concentrations (mg//) for aquifer units in the western Puerco River basin, Arizona. aquifer Alluvial Bidahochi Chinle no. of samples (21) (6) (7) stat min max m ean min max m ean min max m ean pH 6.85 9.43 7.66 7.00 8.10 7.65 6.96 9.04 7.72 TDS 168 1143 684 150 516 275 188 1390 645 HCO,- 148 621 339 105 271 174 147 1198 405 SOp" 2 494 157 4 99 32 10 267 140 c r 2 224 66 4 59 24 2 63 35 Ca2+ 1 212 65 8 92 41 2 116 56 Mr2+ 1 96 21 1 7 4 0.3 47 16 Na+ 29 355 173 10 191 57 11 505 149 K+ 0.4 8 3 1 3 2 1 9 4 SiO? 3 24 10 7 10 12 5 12 9 Table 4. Summary statistics of minor ion and trace element concentrations (m g//) for ground water in the western Puerco River basin, Arizona. ion/element min max m ean arsenic <0.001 0.072 0.007 cadmium <0.001 0.023 0.008 copper 0.010 0.080 0.013 fluoride 0.06 6.03 0.57 iron 0.02 4.52 0.87 manganese 0.01 1.38 0.21 molybdenum 0.010 0.070 0.013 nitrate 0.10 3.60 0.92 selenium <0.001 0.028 0.004 56 Regulations of 1975, and promulgated in the Code of Federal Regulations (CFR) title 40, parts 100 to 149.1 Arizona water quality regulations were not considered in this report. Two types of EPA regulations for inorganic chemicals and radionuclides are applicable for drinking water quality. First, the maximum contaminant level (MCL) is an enforceable regulation which establishes how pure a water from a public water supply (PWS) must be for human consumption. Second, the secondary maximum contaminant level (SMCL) is a regulation designed to control contaminants in drinking water for aesthetic quality. Unlike the MCLs, the SMCLs are not enforceable regulations, but are simple guidelines that represent reasonable goals for drinking water quality. A PWS has to have at least 15 service connections or serve 25 individuals on a daily basis at least 60 days per year. Many samples of water collected during this investigation were from sources that do not qualify as a PWS, however, ground water in the study area is and may become an even more important resource for current and future inhabitants. Thus, it is important to know ground-water quality because the ultimate use may be human consumption. Fifteen of 42 samples of ground water had constituent concentrations that exceeded at least one MCL. A total of 26 concentrations exceeded the MCLs. The values for those MCLs applicable in this report, and the number of concentrations in ground-water samples that exceeded the MCL are listed in Table 5. Additional information on the ion and trace element concentrations is contained in Tables 3 and 4, as well as in Appendices A - F. The MCLs were exceeded for the inorganic elements cadmium, fluoride, and selenium. No sample levels for arsenic or nitrate exceeded the MCL. 57 Table 5. Maximum contaminant levels (MCLs) and number of concentrations in ground-water samples from the western Puerco River basin, Arizona that exceeded the MCL for selected inorganic chemicals. contaminant reference no. EPA MCL no. exceeding arsenic 1 0.05 m g// 0 cadium 1 0.01 m g// 3 nitrate 1 10.0 m g// 0 selenium 1 0.01 m g// 3 fluoride 1 4.0 m g// 1 gross alpha 2 15 pCi// 10 gross beta 2,3 50 pCi// 6 radium 2 5 pCi// 3 1. U.S. Environmental Protection Agency 1988a, maximum contaminant levels, 40 CFR 141.11 Subpart B, page 530. Based on National Primary Drinking Water Regulations for public water systems. 2. U.S. Environmental Protection Agency 1988a, maximum contaminant levels, 40 CFR 141.15 Subpart B, page 533. Based on National Primary Drinking Water Regulations for public water systems. Gross alpha activity including radium-226 activity but excluding uranium activity. Combined radium-226 and radium-228 activity. 3. U.S. Environmental Protection Agency 1988b, maximum contaminant levels, 40 CFR 141.26 Subpart C, pages 544-546. Based on National Primary Drinking Water Regulations for public water systems. The MCLs for radioactivity were exceeded nineteen times. Gross alpha and beta activities displayed variation in all wells that were sampled more than once. The final value of gross alpha used for comparison to the MCL is rendered after the subtraction of U and 222 Rn activity from the total gross alpha activity of the sample. If gross alpha still exceeds the MCL of 15 pCi//, then all remaining alpha-emitting radionuclides should be identified. The discrepancy between gross alpha and the measured radionuclides indicates that some alpha-emitters were not analyzed. Radionuclides that contribute to the total gross beta activity were inadequately identified as well. 58 In principle, gross alpha and gross beta activity is the sum of all alpha- or beta-emitters in a water. The measurement is subject to inaccuracies from the effect of counting errors, TDS, and particularly for gross alpha activity, the assumptions of 234 U/ 238 U equilibrium. Activities of 226 Ra and 228 Ra exceeded the MCL in three samples. There is no MCL for U, however, it is considered a chemical toxin and the Adjusted Acceptable Daily Intake (AADI) is 60 fig/1 or 40 pCi /I (Webb et al., 1987b). Two samples contained concentrations that exceeded the AADI for U. Twenty-nine samples had at least one constituent concentration that exceeded the SMCL for inorganic contaminants. Eighty ion concentrations and five pH values exceeded the SMCLs. Table 6 indicates which SMCLs are applicable in this report and the number of concentrations in ground-water samples that exceeded the SMCL. The large number of concentrations that exceeded the SMCLs reflects the natural water quality and high mineral content of ground water in this region of the United States. The concentrations also reflect those sources of ground water used primarily for agricultural purposes in the Puerco basin, namely livestock. Levels of concentrations in wells developed for stock water are well below the upper limits for livestock. The presence of toluene was detected in sample NL-43 (Indian City) at a concentration of 1.16 parts per billion. Sample NL-43 was not collected according to the preferred methodology prescribed for the analysis of volatile organic compounds because proper equipment was unavailable at the time. Although only toluene was identified, multiple hydrocarbon peaks were detected in the sample which suggests the possibility of fuel contamination of ground water or the well. The Indian City craft shop operates an automobile refueling facility and stores petroleum products in underground tanks at the site. 59 Table 0. Secondary maximum contaminant levels (SMCLs) and number of concentrations in ground-water samples from the western Puerco River basin, Arizona that exceeded the SMCL for selected inorganic chemicals. contaminant reference no. EPA SMCL no. exceeding chloride 1 250 m g// 0 copper 1 1.0 m g// 0 fluoride 1,2 2.0 m g// 1 iron 1 0.3 m g// 18 manganese 1 0.05 m g// 20 pH 1 6.5-8.5 5 sulfate 1 250 m g// 12 TDS 1 500 m g// 29 1. U.S. Environmental Protection Agency 1988b, secondary maximum contaminant levels, 40 CFR 143.3, page 608. Based on National Primary Drinking Water Regulations for public water systems. 2. U.S. Environmental Protection Agency 1988b, secondary maximum contaminant level for fluoride based on average annual daily air temp. Table 6.8, page 103 in Groundwater and Wells (Driscoll, 1986) lists 1.6 mg// for 21.5 - 26.20 C. There is no current regulation for levels of toluene in drinking water. Toluene is a hazardous substance that is regulated under the Clean Water Act (Federal Water Pollution Control Act), and discharge levels of the pollutant are described in 40 CFR part 400 - 424. It is listed as number 086 on the 126- Priority Pollutants list of 40 CFR part 423 in Appendix A. Spatial Changes in Chemistry Sample major ion concentrations were plotted on a map of the study area in Figures 13 - 17. These maps were used to interpret spatial changes in ground-water chemistry across the study area. Dissolved solids content increased along the general flow path from northeast to southwest. Generally, samples from locations close to the Puerco River had higher TDS than samples from locations away from the river. The highest TDS value of 1,390 mg /I was 60 INDEX MAP EXPLANATION 0 WOll 0 windm ill O s p rin g K I 0 3 8 8 O SCALE In KM 1110 1390 O 7 2 9 ouck S o n d a ra Novoio '/tom Figure 13. Sample TDS concentration (mg//) in the study area. 61 EXPLANATION O well IS) windm ill o s p rin g tv 0 1i f „ 219 0 SCALE In KM 342 1 1 9 8 - Sanders o 148 O 271 H 160 ouck C ho m b trs 5ond«r« Figure 14. Sample HC03 concentration (mg//) in the study area. 62 NDEX MAP EXPLANATION O wull El w indm ill O s p rin g I 0 If i. 92 O In KM SCALE 1 78 E9 S u n d e rs O 0 50 31 O DUCK C ham bsrs S a n d a r i Figure 15. Sample Ca2+ concentration (mg//) in the study area. 63 EXPLANATION INDEX WAP AZ 29 15 30 O 66 SCALE In KM 296 235 50- •1 39 5 0 5 — G •107 22 1 25 133 f—355 142 Sanders 74 74 321. 304. O 190 1 78 247 •luptorv H 29 76 343 Figure 16. Sample Na+ concentration (mg/) in the study area. 64 EXPLANATION INDEX MAP w in d m i l l AZ s p rin g 38 15 46 208 Q 239 SCALE In KM 460 45 208 45 494 225- •302 146' 338' •273 1 09 27 99 f— 271 Sanders 123 86 33 36 - L u p to n j 'C ham bers; 27 264 Figure 17. Sample SOf concentration (mg//) in the study area. 65 observed in NL-35, a sample from the Chinle aquifer. Repeat samples with seasonal chemistry had a slightly higher TDS concentration in summer than in winter. Low TDS ground water is generally referred to as "recharge" water in this report. Overall, ground water had a slightly alkaline pH (7.70) in the study area. There was a minute increase of pH from northeast to southwest. The highest pH value (9.43) was recorded at the Navajo Springs well (NL-07), and the lowest pH (6.85) was recorded at the Porter well (NL-17) in Sanders. Bicarbonate and silica (Si) concentrations increased generally from northeast to southwest, and were highest in the Alluvial and Chinle aquifers. Highest HC03_ content (1,200 mg//) was observed in a sample from the Chinle aquifer, although Alluvial samples had higher, average HCO^-. The lowest HC03“ value was observed in a Bidahochi sample. The highest Si concentration observed in NL-08 (Salt Seep) seemed unusual for an Alluvial water from that location because nearby samples had lower Si values. The high Si value reflects suspended and dissolved species since the sample was not filtered, but processes that concentrate ions along flow path and incongruent dissolution of aluminosilicate minerals in clays may also contribute to the sample chemistry. There was a large spatial variation in the concentrations of Ca2+ and Mg2+, although these ions generally decreased from northeast to southwest. Concentrations of Ca2+ were higher in the Alluvial and Bidahochi aquifers than in the Chinle aquifer. In some flow paths toward the river, the decrease in Ca2+ suggests ion exchange of Ca2+ for Na+. An unexpected high Ca2+ concentration of 178 mg// was observed in a sample from the Bidahochi aquifer (NL-27). Highest Ca2+ concentration (212 mg//) in the Alluvial aquifer was observed in sample NL-17. 66 Sodium concentration increased along flow path, whereas K+ values differed by only one or two mg /1 between locations in the study area. Highest and lowest Na+ concentrations were observed in samples from the Chinle aquifer, although Alluvial wells had a higher overall Na+ content. Levels of K+ were greatest in the Alluvial aquifer. The increase in Na+ along flow path coincided with the decrease in Ca2+, and this observation also suggests ion exchange of Ca2+ for Na+. Chloride and SO2- values were higher in the northeast part of the study area, but no clear spatial trends were observed. Mean concentrations of SO 2_ were highest in the Alluvial aquifer and lowest in the Bidahochi aquifer. The 460 mg/I of SO2- in sample NL-27 was unexpected for a spring. The geochemistry of NL-27 may reflect a flow system where higher TDS water from underlying formations moves into the Bidahochi aquifer and discharges at John Silver Spring. High SO 2_ in NL-17 may reflect a similar chemistry and flow system. Dissolution of evaporite minerals, such as anhydrite (CaSOj and gypsum (CaS04 2H20) in Triassic and Permian rocks of the Defiance Plateau, are a natural source of SO2- in local ground water. The high Cl- concentration of NL-08 coincided with high values of most major ions and despite its total chemistry, reflects a unique and more chemically evolved ground water at this location. Ion ratios of HCOjf :Ca2+ and Na+:Ca2+ increased along flow path, whereas, ratios of Ca2+:Mg2+ and S042~:HC03“ decreased. The Na+:Ca2+ ratio was generally < 1.0 in recharge waters from the northeast and southeast parts of the study area (Figure 18). In contrast, the Na+:Ca2+ ratio was generally > 1.0 in most high TDS ground water. Some recharge waters had a Ca2+:Na+ ratio of ten, whereas high TDS ground water had a Ca2+:Na+ ratio of five. In some 67 EXPLANATION O well IS) w indm ill O s p rin g K I f - SCALE In KM 11 .o Lupton C h am b irs S anders Navajo Figure 18. Sample Na:Ca ion ratios in the study area. 68 waters from the Defiance Plateau, the Bidahochi aquifer, and the Sanders area, the S0 4 - :HCO^" ratio was > 1.0. Geochemical Modeling Samples with dissolved chemistry, pH, and temperature were examined using the computer model WATEQDR (Bohm and Jacobson, 1981). WATEQDR is an updated version of WATEQF, which is a FORTRAN IV program that models the thermodynamic speciation of inorganic ions and complex species in solution for a given water analysis (Plummer et al., 1976). Samples from the Alluvial (31), Bidahochi (8), and Chinle (7) aquifers were modeled with WATEQDR to determine the partial pressure C02 (Pco2) aQd the apparent state of saturation of the sample water with respect to several solid mineral phases. The saturation index (SI) for anhydrite, calcite, gypsum, quartz, and Si02 was examined because these minerals are common components of aquifer lithology in the study area. Values for Pqo2 an^ SI are given as the logarithm (log) to base 10 in the following discussion and in Appendix I. The samples were examined previously with the graphical method described by Hem (1985) to compute the SI value for calcite. Log PCo2 values ranged from -2.74 to -1.50 atmosphere (atm) in the Alluvial aquifer, and from -2.96 to -1.82 atm in the Bidahochi aquifer. Except for NL-35, log PCo2 ranged from -1.96 to -1.58 atm in the Chinle aquifer. Sample NL-35 had a log Pco2 °f -3.12 which suggests the water is apparently part of a closed system with respect to C0 2. Higher log Pco2 values in the Chinle aquifer indicate sources of dissolved C02 in the ground-water flow system (plant respiration and aerobic decay) are more active in this unit than in the other 69 aquifers. Locations with seasonal chemistry reflect a slightly lower log Pco2 in the winter than in the summer. All samples were undersaturated with respect to anhydrite, gypsum, and Si02, which suggests that ground water in the study area is apparently dissolving these types of minerals. Except for sample NL-30 (Alluvial aquifer), the samples were saturated with respect to quartz, and ground water may be dissolving this mineral. Nineteen samples from the Alluvial aquifer, one sample from the Bidahochi aquifer, and three samples from the Chinle aquifer were saturated with respect to calcite. Samples from the Bidahochi aquifer and the northeast part of the study area were undersaturated with respect to calcite, whereas samples from the Alluvial and Chinle aquifers in the Sanders-Chambers area were at equilibrium or slightly saturated. This information suggests that recharge waters are dissolving calcite, whereas ground water farther along the flow path is at equilibrium or saturated with calcite. Overall, the graphical method of calcite SI determination compared favorably with the computer-generated results of WATEQDR. Trilinear Diagrams Aquifer chemical behavior and water-types were studied using trilinear (Piper) diagrams, which show the relative percentage of ions in units of milliequivalents per liter (meq/Q. Figures 19 - 21 are trilinear diagrams for ground water in the Alluvial, Bidahochi, and Chinle aquifers. The diagram of samples from the Alluvial aquifer displayed a wide range of water-types. Ground water ranged from a Ca2+-SO 2_ to Ca2+-Na+-HCO^" water-type, although most samples were characterized as a Na+-Ca2+-H C 0f-S02- water. Fifteen Alluvial samples plotted in the region where waters have equal percents 70 X X XxxX ,s o/ ground-water r o / flow direction XX: 90 80 70 60 50 40 30 20 10 10 20 30 40 SO 60 70 80 90 CALCIUM CHLORIDE Figure 19. Trilinear diagram(% meq//) of ground-water samples from the Alluvial aquifer. 71 90 80 70 60 50 40 30 20 10 10 20 30 40 50 60 70 80 90 CALCIUM CHLORIDE Figure 20. Trilinear diagram(% meq /I) of ground-water samples from the Bidahochi aquifer. 72 90 80 70 60 50 40 30 20 10 10 20 30 40 SO 60 70 80 90 CALCIUM CHLORIDE Figure 21. Trilinear diagram{% meq//) of ground-water samples from the Chinle aquifer. 73 of major ions. This observation suggests that the Alluvial aquifer is composed of mixed-ion water-types. The trilinear diagram of samples from the Bidahochi aquifer showed a higher relative percent of Ca2+ to Na+ compared to the Alluvial aquifer. Although Ca2+-HCOjf was the dominant water-type of the Bidahochi aquifer, the trilinear diagram displayed a trend toward increasing percent Na+ and S042- with decreasing percent Ca2+. Ground water in the Chinle aquifer was mostly a Ca2+-S 02- water-type, although it ranged to a Na+-Ca2+-HC0^'-S02“ water. The higher SO2- content in Chinle ground water results from dissolution of evaporite minerals and residual solids that were introduced into the aquifer during or after deposition. Geochemical processes that resulted in the formation of regional western-states-type U mineralization in the Chinle; and the occurrence of U minerals and associated metals in the aquifer material, may control some of the ground-water chemistry in the Sanders area. Water-types in the three aquifers revealed a chemical composition that is a function of time and position along the ground-water flow path. Ground water moving along a flow path generally evolves from a composition of pure atmospheric precipitation to a composition of seawater (Chebotarev, 1955). Samples from the Chinle aquifer best illustrate the geochemical evolution of ground water in this manner. Moreover, the age of the aquifer and the possibility of longer residence times for some ground water in this unit, provides that some high TDS water-types in the Chinle should be more chemically evolved toward the composition of seawater. In contrast, some low TDS water- types in the Chinle are considered recharge water produced recently by 74 infiltration of precipitation (rain and/or snow melt water) to a zone of saturation. Geographic areas and their respective water-types are presented in Figure 22. Samples from each area were plotted on a trilinear diagram, and a boundary was drawn along the margin of outermost points in the sample group. Identifiable water-types for each geographic area were observed. Ground water in the Houck-Lupton area north of the Puerco River was a Ca2++Mg2+-SO |- -HCO^“ water-type, whereas, ground water in this area south of the river was a Na++K+-HC03- water-type. Ground water in the Navajo- Pinta area was also a Na++K+-HCOf water-type. The Chambers area had two general water-types: Na++K+-HC03" and Ca2++Mg2+-SO 2--HC03“. Sanders area ground water displayed a mixed-ion water-type which had a tendency toward a more Ca2++Mg2+-Cl- -SO 2_ water-type. Ground water in the Spurlock Ranch alluvium, (an irregular, geologically- mapped body of Alluvial material trending west across the ranch property), displayed increasing dissolved solids in samples located in a line perpendicular to the river. Spurlock Ranch Alluvial water changed from a Ca2++Mg2+-HCO the start of the flow path, and from a location 2 km away from the river at the end of the flow path. 75 Sanders area Chambers area Houck-Lupton area South of Puerco Navajo-Pinta a rea S p u rlo c k R a n c h A lluvium Houck-Lupton area North of Puerco Chambers area L u p t o n o^Puerco Riva DUCK C hom bars S a n d a r s Figure 22. Modified trilinear diagram (% meq//) of water-types for geographic areas. 76 Ground-water Radio chemistry Spatial Changes in Radiochemistry Spatial changes in radiochemistry were examined using Figures 23 and 24. General observations suggest that radioactivity is highly variable from northeast to southwest along ground-water flow paths, but was noticeably higher in sam ple locations north of the Puerco River. Ground water with elevated radioac tivity was from samples produced from the Alluvial and Chinle aquifers. Com bined gross alpha and gross beta ranged from 1 to 590 pCi /I. The highest gross alpha activity of 490 pCi /I was observed in sample NL-35. Zero (0.0) gross alpha activities were observed in samples: NL-01, -09, -10, -28, and -29. The highest gross beta of 180 pCi// was observed in sample NL-21. Zero (0.0) gross beta activity was observed in sample NL-29. The mean value of gross alpha was 36 pCi//; gross beta mean was 21 pCi//. The activities of measured radionuclides (U, 226 Ra, 228 Ra) accounted for as little as 0% to only as much as 40% of gross alpha plus gross beta activity. Numerous samples with elevated gross beta activity were unaccounted for by specific radionuclide measurement. Radionuclides such as radon-222 (222 Rn), thorium-234 (234 Th), lead-214 (214 Pb), bismuth-214 (214 Bi), and polonium-210 (21° Po) are radioisotopes of the U decay series (Figure 25) not measured in the water. These radionuclides probably contributed to the gross radioactivity of the samples. Values of gross alpha activity should be given careful consideration in an investigation of this sort, because the gross alpha method is known to produce some variability in the measurement depending on how the activity of 222 Rn daughters is handled (Oural et al., 1988). Polonium-210 is a 222 Rn daughter isotope that shows a noticeable variation in activity with holding time depend ing on the activity of lead-210 (21° Pb) and preparation method prior to count- 77 EXPLANATION O well El windm ill O s p rin g 6 /3 410/180 K I 0 f « 0.7 /3 O 13/10 SCALE In KU 4/4 H 71/38 36/36 32 /3 3 16/11 490/96 20/9^ 30/20 El 3 /8 3/1 2 7/8 40/1 7 A i—37/21 Sanders NEW NEW M E X IC O Lupton //Puerco Rive ouck C h o m b m Sondara 1 6 /8 5 Figure 23. Sample gross alpha and gross beta activities (pCi//) in the study area. 78 EXPLANATION O well H w indm ill O s p rin g 64.6 a I f r „ SCALE In KM 1 1.3 1 6.3 315.6 4.2 8 0.3 1 1 .4 O 6.9 ouck C ham bars S o n d art © Figure 24. Sample uranium ion concentrations (A*g//) in the study area. ATOMIC WEIGHT 8 3 2 4 3 2 0 3 2 8 2 2 222 210 8 1 2 214 iue 5 Dmnn rdocie ea eiso rnu-3 (rm eb e/ Webb (from uranium-238 of series decay radioactive Dominant 25. Figure URANIUM 4 3 2 2 .9 i .9 2 i .8 4 8 3 2 v c t U U i M l o h nt,days, s y a d t., in m pho h ip o NUCLIDE yoart) t r a o y r o 2 8 3 8 4 8 8 8 8 8 7 8 8 8 9 8 0 9 1 9 2 8 oata a to i 4 3 2 al., 1.21 o P 97, i. 2). fig. 1987b, MODE OF DECAY EXPLANATION THORIUM 4 3 2 0 3 2 Id . 4 2 h T Th h T RADIUM 6 2 2 1 602 y 602 1 R a a R A T O M I CN U M B E R a R RADON 222 0d .0 3 Rn n R POLONIUM 218 4 P« 14 2 Po o P 214 210 S.Od b P 210 4 1 2 LEAD Pb Pb 79 80 ing. Where U and 226 Ra activity exceeds the MCL, Oural et al. (1988) suggest the measurement of 210 Po to further identify important alpha-emitters in water. Samples from locations north of 1-40 at Sanders have a slightly different composition than samples south of 1-40 at Sanders (NL-16/33/38, NL-31/37, and NL-32/39), and this may influence the radiochemistry. Samples from locations north of 1-40 appear to reflect more the chemistry of waters in contact with bedrock aquifer material, whereas samples from locations south of 1-40 appear to reflect more the chemistry of waters in contact with alluvium. Higher radioac tivities were observed in samples north of 1-40 where alluvium has less effect on water chemistry. This observation suggests that in some locations, bedrock sources of radioactivity are a greater source of contamination to local ground water than water in or from the Alluvial aquifer. Uranium displayed a large spatial variation in concentration from northeast to southwest, and values were generally higher from sample locations north of the river. Concentrations of U ranged from the high of 315 fig/1 in sample NL- 35 to less than one fig/1 in samples: NL-01, -09, -10, -12, -15, and -18. The mean U concentration was 18 fig/1. The three main processes that possibly mobilize U in ground water of the Puerco basin include dissolution, complexa- tion, and sorption. Dissolution and complexation of U can be illustrated with information from published literature, but details of uranyl sorption processes in natural waters are not well understood (Langmuir, 1978). An understanding of U mobilization can be gleaned from a pH-Eh diagram, which is useful predicting and defining the equilibrium behavior of a multivalent element such as U. The pH-Eh diagram is constructed for a specific set of chem ical conditions and ion concentration. The Eh value (redox potential) indicates if a water is relatively oxidizing or reducing. Measurements of sample Eh were 81 not made in this investigation, but in a similar study Eh was measured and that data can provide insight here. Szabo and Zapecza (1987) generally considered that an Eh value > 0.2 volts categorized ground water as relatively oxidizing, and an Eh value < 0.2 volts categorized ground water as relatively reducing. Figure 26 is and pH-Eh diagram of the U-02-C02-H20 system at 25 ° C, P Cq2 = 10-2 atmosphere, and U concentration = 240 fxg/l. The diagram indicates that U species are stable in the range of pH observed in ground water of the Sanders area with elevated radioactivity. In sample NL-21, U is inferred to have mobilized as a result of oxygenated recharge water infiltrating the Chinle Formation and dissolving U minerals. The recharge water quality of NL-21 with its neutral pH (7.04) and low TDS (229 mg//) favors the presence of U in the form of the uranyl ion U02+2. Contrast ingly, the alkaline pH (9.04), high HCO;f (1,198 mg//), and evolved ionic charac ter (no Ca2+ content) suggest that the presence of high U in NL-35 results from the formation of uranyl carbonate complexes. The large Na+ concentration of NL-35 is supported by the idea from Hostetler and Garrels (1962) that this cation is the likely choice to balance a large excess of anionic complexes of U. The chemistry of NL-35 does not appear to support the occurrence of other U complexes described by Langmuir (1978) which include hydroxide, phosphate, fluoride, sulfate, and possibly silicate. The presence of U in samples NL-05 and NL-20 is also interpreted to result through carbonate complexes. Typical sorbents that could mobilize U in ground water of the Puerco basin include: organic matter; iron, manganese, and titanium oxyhydroxides; and clays. Sorption of U on iron hydroxide particles was suggested as the potential mechanism for U mobility in the Alluvial aquifer of the Puerco River basin (Webb et a/., 1987b). Langmuir (1978) suggested that 82 ' N o 0.8 UO. 0.6 0.4 V) 0.2 1 s£ LU ■Area of Uraninite - 0.2 -0.4 - 0.6 0 2 4 86 pH Figure 26. pH-Eh diagram of the U-02-C02-H20 system for; 25 ° C, Pco2 = 10-2 atmosphere, and U concentration = 240 fxg/l (from Guilbert and Park, 1986, fig. 20-15). 83 clays are relatively unimportant as concentrators of U, and the presence of sul fate, fluoride, and carbonate complexes may inhibit sorption. The lack of detailed information on sorption processes precludes determination of this con cept as a viable mechanism of U transport in this study. However, some evi dence suggests that uranyl sorption is an important step leading to the forma tion of uranyl and uranous minerals in solution (Barton, 1956; Kochenov et al., 1965). Activities of 226 Ra and 228 Ra were less than one or two pCi// for the majority of samples. The occurrence of 226 Ra was observed only in samples NL-21 (73 pCi//) and NL-26/41 (11 pCi /[), which were collected from wells that produce from the Chinle aquifer. Sample NL-21 was taken from windmill no. 18T-530 which is reported to produce from the Shinarump Member of the Chinle. Sample NL-26/41 was collected at the Indian Ruins store which is located in the Shinarump Member, and it is quite likely that the well produces from this unit. Sample NL-41 had a value of 5.6 pCi /I 228 Ra and was the only sample with a significant activity of this radionuclide. Low values of 226 Ra and 228 Ra suggest that the isotopes are not very mobile in ground water of the Puerco River basin. Similar observations on the absence of radium in Alluvial water was reported in New Mexico by Kaufmann et al. (1976), and in Arizona by Webb et al. (1987b). Gilkeson and Cowart (1987) observed in lower Paleozoic sandstone aquifers that the five year half life of 228 Ra does not allow it to mobilize a significant distance from its source. In a study of radioactive ground water in Triassic rocks of the Newark Basin, New Jersey, Szabo and Zapecza (1987) observed that though U and 226 Ra may be spatially related, elevated activities of both radionuclides were rarely found concurrently in the same sample of water. The presence of high U and no 84 226 Ra in sample NL-35 appears to support their observations. However, NL-21 and NL-26/41 contained measurable U and 226 Ra in the same sample water. This evidence suggests that samples NL-21 and NL-26/41 reflect a chemical environment influenced by nearby sources of U as well as 226 Ra. The recharge water quality of NL-21 and its high activities of radionuclides suggest a more recent water close to its place of origin in the ground-water flow system. Sample NL-26/41 geochemistry is slightly more evolved along flow path than NL-21. Trilinear Diagrams of Radioactive W ater Water-types of samples containing greater than 15 pCi fl gross alpha and greater than 50 pCi// gross beta were examined using a trilinear diagram (Figure 27). Most of the radioactive samples depicted in the diagram are those waters with a high TDS concentration. The large variation in water-types suggests that ground water with elevated radioactivity does not coincide with a single, unique water chemistry. Ground water with elevated radioactivities ranged from Ca2+- HCOjf or Ca2+-S02_ to Na+-Ca2+-HCO^-SO2_ and Na+-HCO^ water-types. The distribution of sample points reflect the range of water-types identified pre viously. The range of water-types indicates that radioactivity occurs in most all of the types of ground water identified in this study. Statistical Correlation Spearman rank correlation was used by Szabo and Zapecza (1987) in a study of radioactive ground water to correlate inorganic concentrations with activities of U and 226 Ra. If the Spearman correlation value is positive, the con centration of a chemical ion will tend to increase with increasing radioactivity. Inversely, if the Spearman correlation value is negative, the concentration of an ion will tend to decrease with decreasing radioactivity. Thus, chemical ions can be used to indicate the possible presence or absence of radioactivity in ground 85 , s CALCIUM CHLORIDE Figure 27. Trilinear diagram in meq/ / of samples with radioactivity greater than EPA standards for gross alpha and gross beta (A = samples > 15 pCi /I gross alpha; B = samples > 50 pCi// gross beta). 86 water. It is important to note that significant correlation alone does not indicate cause and effect relationships between radionuclides and ion concentrations. Table 7 lists the Spearman correlation coefficient for U and 226 Ra activities with inorganic constituents in samples collected in this study and samples from the study by Webb et al. (1987b). Significant correlation at the 0.05 level was observed between U and gross alpha, gross beta, 226 Ra, TDS, SO |“, Ca2+, and K+. Significant correlation at the 0.05 level was observed between 226 Ra and gross alpha, gross beta, U, TDS, SO2-, HC03“, K+, Cl", and pH. It is impor tant to note that no mininum detection value was substituted for samples of 226 R a th at measured zero. Generally, increasing activities of U and 226 Ra appear to be associated with increasing levels of TDS. Correlation of U with Ca2+ and SO2- suggests increasing concentration of these ions coincides with increasing U activity. Some radioactive ground water from the Defiance Plateau was identified as a Ca2+-SO2“ type-water. Correlation of 226 Ra with HCOjf and SO2- suggests increasing concentration of these ions coincides with increasing 226 Ra activity. Potassium correlates with U and 226 Ra and this suggests that increasing K+ concentration may coincide with increasing radionuclides. Increasing radioac tivity may reflect increasing K+ content from clays transporting radionuclides through sorption. Increasing 226 Ra activity also correlates with increasing pH. Correlation of gross alpha, gross beta, U, and 226 Ra with sample location distance to the Puerco River is shown in Table 8. Significant correlation at the 0.05 level was observed to be higher with greater distances from the river. This observation suggests that radioactivity in ground water is greater away from the Puerco River than toward it. Concurrently, simple comparison of radio 87 nuclide activities and location along or from the Puerco River displayed no direct relation to distance (Webb et ai, 1987b). Table 7. Spearman Rank correlation coefficient (r ) for uranium and radium-226, and selected chemical species, TDS, and pH at the O.Ss significance level. chemical rs for uranium rs for radium-226 parameter (46 samples) (46 samples) gross alpha 0.78 0.50 gross beta 0.37 0.36 uranium — 0.41 radium-226 0.41 — bicarbonate 0.17 0.36 sulfate 0.61 0.42 calcium 0.37 0.27 magnesium 0.25 0.29 sodium 0.04 0.23 iron 0.15 0.29 manganese 0.15 0.26 silica -0.24 0.27 TDS 0.56 0.35 pH -0.01 0.34 Table 8. Correlation coefficient (r) for radiochemical parameters and sample location distance to the Puerco River at the 0.05 significance level. chemical r: 0-0.5 km r: 0.5-1.0 km r: 1.0-5.0 km r: 5.0-13.0 km parameter (20 samples) (10 samples) (10 samples) (6 samples) gross alpha 0.24 0.14 -0.49 0.68 gross beta 0.34 0.59 -0.27 -0.82 uranium -0.17 0.19 -0.50 -0.90 radium-226 0.36 -0.18 -0.45 — 88 Environmental Isotopes Environmental isotopes of hydrogen and oxygen are used to indicate the type, source, and age of a given water. They are regarded as conservative tracers since they are an integral part of the H20 molecule. The isotope tritium (3H) and the stable isotopes deuterium (2H or D) and oxygen-18 (180) were used in this investigation. Tritium Analyses Analysis of 20 samples revealed the presence of tritium in the Puerco River and in four samples of ground water (See Figure 28). Two artesian springs (samples NL-13 and NL-20) had 5 TU. Two samples in Sanders (NL-16 and NL-17) had 19 TU. The grab sample of the Puerco River collected at Sanders during a high flow event (August 28, 1987) had 9 TU. Interestingly, the low tritium content of samples from the southern part of the study area suggests that most ground water is more than 20 to 50 years in age. Tritium in the Sanders school well and the Porter well suggests that some ground water pumped by these wells has received some recent recharge. The river contained some tritium because the flow in the channel was composed largely of surface runoff produced by storm activity only a few days prior to sampling. Stable Isotope Analyses Thirty-seven ground-water samples, two grab samples of the Puerco River, and four grab samples of precipitation were analyzed for their hydrogen and oxygen isotope ratios. The locations of sample collection and values of 5D and 5 180 are shown in Figure 29. Six locations (NL-Gl/34, NL-22/40, NL-25/43, NL-26/41, NL-31/37, and NL-32/39) were sampled once in the summer and once 89 EXPLANATION © well S3 windm ill o s p rin g (V I 0 if SCALE In KM 1 9 T U 19 TU H< 5 TU < 5 TU 9 TU (river) 5 TU < 5 TU 'Sanders < 5 TU 5 TU < 5 TU < 5 TU n 8 < 5 TU < 5 TU ° w s /m m Lupton < 5 TU H< 5 TU ruerco Rlvervv> ouek C h am b an S o n d ari < 5 TU Figure 28. Sample locations and tritium values (TU) of ground water and the Puerco River in the study area. 90 INDEX MAP EXPLANATION lost sample O ground water 9 3/ — 1 1.6 - 2 4 /- 3 .5 / •Luptorr 'Chambers; [Sanders1 iso06 (Gallup. NM) -29/-5.0 Figure 29. Sample locations and 5 D/5 180 values ( °/oo) of ground water, pre cipitation, and the Puerco River in the study area. 91 in the winter. One location (NL-16/33/38) was sampled once in the summer, once in the winter, and again in the following summer. Delta 180 values in ground water ranged from -12.5 °/o o to -7.9 °/o o , and 8 D values ranged from -97 °/o o to -62 °/o o . Average 8 lsO and 8 D values in ground water were -10.7 °/o o and -82 °/o o , respectively. Samples from the Chinle aquifer displayed the largest range in 8 D and 8 180 values compared to samples representing the Alluvial and the Bidahochi aquifers. The samples displayed a large spatial variation in isotope ratios of D and 8 180 , which suggests that the ground-water system is quite complex and not easily explained with the small number of samples. Sources of recharge to the ground water are unclear. Stable isotopic ratios of ground-water samples are dissimilar to ratios of the few Puerco River samples and summer precipitation samples collected. Thus, it is unclear if these waters are involved in recharge. Winter snows are probably part of the recharge system, but no samples were collected to test this idea. Moreover, the age of most of the ground water was not established, so it may contain a paleo component. Comparison of the isotopic and the geochemical composition of samples revealed that although many samples were similar in their ion concentrations, their isotopic ratios of 8 D and 8 180 were quite different. Some samples of ground water, considered to be chemically evolved along a flow path, displayed a more depleted or more enriched isotopic composition. Chemical composition of ground water along the inferred ground-water flow path in the Spurlock Ranch alluvium from sample NL-12 to NL-06 changes from a Ca2+-HCO^" to a Na+-HCO^" water-type. The 8 D value was -79 and -86 °/oo in samples NL-12 and NL-10 collected at the eastern extent of the alluvium, respectively; but decreased to -92 and -93 °/o o at samples NL-09 and NL-07 collected at the western extent of the alluvium, respectively. Sample NL-06 had 92 a 5D value of -77 °/oo. The variation of 8 180 values in the samples NL-12 to NL-06 collected no more than 10 km apart was < -2.0 °/oo. The cause of differences in the 8 D value of ground water along this flow path can not be explained. Sample NL-35 was from a water inferred to have an evolved chemical composition that was produced over a long period of time. However, the NL-35 8 D value of -90 °/oo does not indicate an age of the water. Figure 30 shows the Meteoric W ater Line (MWL) defined by Craig (1961) and the local meteoric water line (LMWL), as well as the stable isotope values of ground water, the river, and precipitation from the study area. Ground-water samples plot on or near the LMWL and below the global MWL. Precipitation samples consist of three samples of a single storm event, one sample of separate storm event, and one sample of a storm event in nearby Gallup, New Mexico. If snow samples were collected from the area, their isotopic values would be o suspected to plot on the LMWL and probably be more depleted than the ground-water samples. Plots of 8 180 and 8 D values of ground-water categorized by the sample’s location distance to the river, and the sample aquifer unit displayed no identifiable groups. Samples of ground water that were taken from wells < 0.5 km from the river were about 10 °/oo more enriched in deuterium than samples collected from wells >1.0 km from the river. The enriched deuterium content of Alluvial water close to the river appears to indicate some input from a more isotopically heavier source such as the river, or infiltration of water from the unsaturated zone enriched by evaporation. Locations with repeat samples displayed a small variation above the analytical precision (+/- 1.0 °/oo) in 8 D. Figure 30. Stable isotope values of of values isotope Stable 30. Figure delta deuterium (5D) o/oo J 0 0 1 - - - -40 - 2 0 -t 0 2 - 80 60 - - - 13 ae ie n te oa mtoi ae line. water meteoric local the and line water cipitation, and the Puerco River plotted with the Craig meteoric meteoric Craig the with plotted River Puerco the and cipitation, 5 D = 8(5>sO) 4.9 + 5 = D 12 1 1 10 = ( 8)+ 10. + 8(5,80) 5 = D et oxygen—18 delta -9 8 180 vs. vs. 180 -8 8 D °°)o rud ae, pre water, ground of °/°o) ( D -7 (5 8 ) o/oo 180) -6 lbl MWL global rcptto (rain) precipitation • Pec River Puerco water ★ ground ® - ■ local ■ local - EXPLANATION -5 MW l -4 93 94 SUMMARY AND CONCLUSIONS The ground-water system in the western Puerco River basin in the Sanders, Arizona area is complex and the chemical composition is quite variable. A gen eralized, equipotential water surface map indicated that ground water flows west and southwest across the study area under confined and unconfined conditions. Geologic structures and changes in aquifer permeability influence the occurrence and movement of ground water in the subsurface. Ground water was character ized as being hard water and having a quality that ranged from fresh to brack ish. Fifteen of 42 samples contained constituent concentrations that exceeded at least one MCL for inorganic contaminants. The MCLs for calcium, fluoride, selenium, gross alpha, gross beta, and radium were exceeded. Twenty-nine sam ples had at least one constituent concentration exceed the SMCL for inorganic contaminants. Toluene was detected in sample NL-43 from the Indian City facility, and this evidence suggests the possibility of fuel contamination in the well or in ground water at the site. High TDS water was inferred to be more chemically evolved and reflect a possible longer residence time than low TDS water. Low TDS water was con sidered recharge water. Ground water in the study area had a slightly alkaline pH overall. Lower TDS ground water is contained in the Bidahochi aquifer and higher TDS ground water is contained in the Chinle and Alluvial aquifers. Sul fate, HCO^", and Ca2+ were higher in samples from locations in or adjacent to 95 the Defiance Plateau, and concentrations of these ions generally decreased along the ground-water flow path. Sodium generally increased along flow path, whereas Ca2+ decreased, which suggests ion exchange of Na+ for Ca2+. The Ca2+:Na+ ratio was > 1.0 in ground water from the northeast part of the study area, but it was < 1.0 in the southwest part. Log Pco2 values were higher in the Chinle aquifer. The Bidaho- chi aquifer and ground water from the northeast area were undersaturated with calcite, whereas, the Alluvial and Chinle aquifers were at equilibrium or saturated with calcite. All water samples were undersaturated with respect to anhydrite, gypsum, and Si02, however, most waters were saturated with respect to quartz. Ground water from the Bidahochi aquifer was identified as a Ca2+-HCO^ water-type. Alluvial aquifer water was identified as being a mixed-ion or Na+- Ca2+-HC03--S02- water-type. The Chinle aquifer water was identified as a Ca2+-S 02- or Na+-Ca2+-HC0^"-S02- water-type. Water-types identified for a geographic area reflect the composition of aquifer materials in the area and the location of ground water along flow path. Radioactivity of ground water was quite variable across the study area, and due largely to the presence of U in solution. Elevated radioactivity was observed to occur most often in the Alluvial and Chinle aquifers. Average radioactivity in ground water for gross alpha was 36 pCi/Z, and for gross beta it was 21 pCi f l . Activities of measured radionuclides accounted for as little as 0% to as much as 40% of gross radioactivities. Unmeasured radionuclides in the U decay series and problems with the analytical methods of radiochemistry are responsible for the discrepancy between specific and gross activities. 96 Uranium concentration in ground water averaged 18 fj,g/l and displayed a large spatial variation, but was generally higher in samples from locations north of the Puerco River. Processes that were inferred to mobilize U in ground water include dissolution, complexation, and sorption. Activities of 226 Ra and 228 Ra were < 1.0 or 2.0 pCi /I in most samples. The sparse occurrence of Ra in solu tion suggests that it is not easily mobilized like ions of U, and local sources are probably responsible for the occurrence of Ra in ground water. Elevated radioactivities in ground water were not identified with a single, unique water- type. Spearman rank correlation of sample ion concentrations indicated that significant correlation was observed between U and 226 Ra when paired with gross alpha, gross beta, 226 Ra, TDS, SO2-, Ca2+, and K+. The presence of high TDS water and individual ions such as SO2-, Ca2+, HCO^", K+, and Cl- may serve as indicators of elevated radioactivity in ground water of the western Puerco River basin. Simple correlation of radioactivity with the sample’s loca tion distance from the Puerco indicated significant correlation was higher with greater distances from the river. Tritium analysis of 20 samples in the southeast part of the study area sug gested that most ground water was more than 20 to 50 years old. Samples of ground water with similar ionic character had dissimilar isotopic ratios of 5D and <518 O. The large spatial variation of 6 D and <518 O in water samples sug gested that the ground-water system is complex and not easily explained with the small number of samples collected for investigation. It is unclear as to the role of Puerco River water and summer precipitation in ground-water recharge. A conceptual model of the hydrogeologic system is shown in Figure 31. The variation of ground-water quality along the Puerco River in the vicinity of 97 ‘:Y: .•Water Table CONT^INANT§‘'^^^Saturated & S i Unsaturated "■'. y / : \ . s 9Rption river r e c h a r g e .:;• .•„• •; m ix i n g : . Bidahochi Aqfr Unconfined . . Saturated i- RECHARGE ;; • / ; . : - f . v .; T ION EXCHANGE • Bedrock Chinle Aqfr g ■ •~/-: • .••••". ^ rr-^ sa*. ->» _ • • T T - V i v />. • •••.. ^ > ;, r?7.CONy.LE^^O^:.;;;-:;;V’/ ^ M ^ENC E- TIME ? r-r3^ ^ ^ » « Figure 31. Generalized diagram of a conceptual model illustrating the hydro geologic system in the study area (after Webb et al, 1987b). 98 Sanders, Arizona is due largely, to physical controls such as lithology, residence time, recharge sources, and a complex ground-water flow system. Chemical processes such as dissolution, ion exchange, sorption, and complexation also exert some control on ground-water quality in the study area. Regional radioactive occurrences in the Chinle Formation and higher correlation of radioactivity with increasing distance suggests that most elevated radioactivity in ground water around the Sanders area was produced by natural sources and not anthropogenic sources associated with recharge water from the Puerco River. 99 FURTHER RESEARCH The areal and temporal variation of ground-water quality in the Sanders area, Arizona needs to be examined further through continued collection and interpretation of hydrogeologic data that would provide more detailed informa tion regarding the ground-water system. Categories for additional study include: monitoring of surface and ground water; geochemical analysis of water samples; geochemical modeling; collection of additional water samples; grid sampling and mapping of the Puerco River channel sediments; and determination of the hydraulic properties of the Alluvial aquifer and/or bedrock aquifers. Monitoring of surface water and ground-water quality changes on a seasonal basis would provide more information about fluctuations in recharge quality and changes in water quality during different times of the year. High flow events of the Puerco River should be sampled to determine the levels of potential contam inants that are physically mobilized during times when the river is actively tran sporting large volumes of water and sediment. Ground water may exhibit sea sonal variations in radioactivity in wells suspected to receive some recharge from the river. All wells used as sources of drinking water should be monitored on an annual basis, at minimum, to insure the water is safe or if it requires treatment to remove contaminants. All ground-water samples should be filtered in the field during collection and analyzed by a reliable laboratory for major ions, selected minor ions and trace elements, and gross radioactivity. If levels of gross radioactivity are high, then further analysis for specific radionuclides should follow to determine the 100 source of the elevated radioactivity. Problems discussed earlier in the methodol ogy of radiochemical analysis should be considered, particularly the presence of 222 Rn and its daughter product 210 Po, as well as sample holding time prior to analysis. Radon was not measured in this study and it is an element in the U decay series that is likely to be present in some areas. Sample collection should include measurement of dissolved oxygen and Eh when possible, because these parameters can provide more information about the geochemical behavior of ground water. Determination of the source of radioactive contaminants in the Alluvial and bedrock aquifers is complicated by the natural sources of radioactivity in the study area. Thompson et al. (1978) determined the statewide average of gross alpha activity for Arizona to be 4.9 pCi//, however, the average U concentration for ground water determined in this study (18 fJ.g/1) converts to an activity of 12 pCi//. This value suggests that the background radioactivity of ground water in the Sanders area is elevated, and determination of radioactivity from anthropo genic sources versus natural sources is not a simple task. Analysis of 234 U/ 238 U ratios in samples with elevated radioactivity may provide a means of determin ing the source of the activity. Geochemical modeling of surface and ground-water chemistry would provide information about the thermodynamic properties of water in the study area. Runnells and Lindberg (1981) used a version of WATEQ called WATEQFC to calculate the SI of calcite as a possible predictor of the presence of U ore depo sits. Modeling studies may also provide data on the oxidation-reduction state of water with respect to U, which is important in understanding the presence and mobility of the element in aqueous solutions. However, Runnells and Lindberg (1984) exercise caution in using measured Eh values in geochemical modeling 101 because the results could be misleading due to the fact a single, master Eh meas urement may not represent natural waters with multiple redox couples. Collection of additional ground-water samples from locations previously unsampled for water quality and radioactivity would provide better areal cover age of water chemistry and background radioactivity in the study area. Although this investigation did sample numerous wells without historical water quality data, many wells throughout the area have no record of water quality sampling and radiochemical analysis. Many wells should be resampled to update older water quality data. Isotope samples of snow, snowmelt water, and rain, and more samples of surface water and ground water should be collected if environmental isotopes (5D, 8 180 ) are to be used to understand the ground water flow system. Grid sampling and mapping of the Puerco River channel sediments would provide detailed information as to the type, location, and contaminant concen tration of material in the river channel across the study area. An areal radiometric survey may identify areas with high levels of radioactivity in the channel, and any elevated areas could be further examined with sediment analysis. Hydraulic properties of the Alluvial and bedrock aquifers could be deter mined through the drilling of monitoring wells which could be lithologically and geophysically logged before known screened intervals of well casing were installed in the open well. A tracer test performed in an area where wells were suspected to receive recharge from the Puerco River may identify some manner of hydraulic connection between the river and nearby wells. Continuous water level recorders installed on wells near the river may show a relation between the well and fluctuations of flow in the river channel on a periodic basis. 102 SELECTED REFERENCES Agenbroad, L.D., 1983, Hydrology of the Wallace and Roberts Ranches, Apache County, Arizona—An evaluation of the Wallace and Roberts Ranches and vicinity: Bellevue, Washington, CH2M Hill, Inc., report prepared for the Navajo and Hopi Indian Relocation Commission. 1985, Hydrogeology of the Wallace Ranch, Apache County, Arizona: Bellevue, Washington, CH2M Hill, Inc., report prepared for the Navajo and Hopi Indian Relocation Commission. Akers, J.P., 1964, Geology and groundwater in the central part of Apache County, Arizona: U.S. Geological Survey Water-Supply Paper 1771, 107 p. Akers, J.P. and Harshbarger, J.W., 1958, Ground water in Black Mesa basin and adjacent areas, in Anderson, R.Y. and Harshbarger, J.W., eds., in Guidebook of the Black Mesa Basin, northeastern Arizona: New Mexico Geological Society, Ninth Field Conference, p. 173-183. Aldis, H., 1979, United Nuclear mine tailings spill hydrologic assessment: Cincinnnati, Ohio, Ecology and Environment, Inc., report to EPA Region IX, 11 p. Anderson, R., 1958, Life zones of northeastern Arizona, in Anderson, R.Y. and Harshbarger, J.W., eds., in Guidebook of the Black Mesa Basin, northeastern Arizona: New Mexico Geological Society, Ninth Field Conference, p. 199-200. Anderson, R.Y., and Harshbarger, J.W., eds, 1958, Guidebook of the Black Mesa Basin, northeastern Arizona: Ninth Field Conference, New Mexico Geological Society, 202 p. Arizona Department of Health Services, 1986a, Puerco River sediment loading model: Phoenix, Arizona, Arizona Department of Health Services report, 23 P- 1986b, Water quality study, Puerco River, Arizona, 1985: Phoenix, Arizona, Arizona Department of Health services report, 31 p. Austin, S.R., 1964, Mineralogy of the Cameron area: U.S. Atomic Energy Commission, report RME-99, p. ?. 103 Bailey, G.H., and Bailey, R.G., 1986, A History of the Navajos: Santa Fe, New Mexico, School of American Research, 360 p. Barton, P.B., Jr., 1956, Fixation of uranium in the oxdized base metal ores of the Goodsprings District, Clark County, Nevada: Economic Geology, v. 51, p. 178-191. Billingsley, G.H., 1985, General stratigraphy of the Petrified Forest National Park, Arizona, in Colbert, E.H. and Johnson, R.R., eds., in The Petrified Forest Through the Ages: Flagstaff, Arizona, Museum of Northern Arizona, bulletin 54, p. 3-8. Birdseye, H.S., 1958, Uranium deposits in northern Arizona, in Anderson, R.Y. and Harshbarger, J.W., eds., in Guidebook of the Black Mesa Basin, northeastern Arizona: New Mexico Geological Society, Ninth Field Conference, p. 161-163. Bohm, B., and Jacobson, R.L., 1981, WATEQDR, an updated version of WATEQF-a computerized chemical model of natural waters: M.S. thesis, University of Nevada, Reno and Desert Research Institute, 79 p. Bollin, E.M. and Kerr, P.F., 1958, Uranium mineralization near Cameron, Arizona, in Anderson, R.Y. and Harshbarger, J.W., eds., in Guidebook of the Black Mesa Basin, northeastern Arizona: New Mexico Geological Society, Ninth Field Conference, p. 164-168. Canby, T., 1982, The Anasazi—riddles in the ruins: Washington, D.C., National Geographic Magazine, National Geographic Society, v. 16, no. 5, p. 554-592. Chenoweth, W.L., and Malan, R.C., 1973, The uranium deposits of northeast Arizona, in New Mexico Geological Society Guidebook, no. 24, p. 139-149, also published as Atomic Energy Commission Technical Manual 191, 1973 (AEC TM-191). Cherbotarev, I.I., 1955, Metamorphism of natural waters in the crust of weathering: Geochimica and Cosmochimica Acta, v. 8 , p. 22-48, 137-170, 198-212. CH2M Hill, Inc., 1984, Planning for the New Lands, prepared for the Navajo and Hopi Indian Relocation Commission: Bellevue, Washington, CH2M Hill, Inc., report, 54 p. 1986, Groundwater evaluation of the New Lands, Phases 1 and 2, Technical memorandum task order Dl: Bellevue, Washington, CH2M Hill, Inc., report, 59 p. 1987, Construction and testing of test/production well no. 1, Technical memorandum, Task order Dl, Phase 3: Bellevue, Washington, CH2M Hill, Inc., report, 98 p. 104 Conley, J.N., 1977, Structure and correlation sections, eastern Mogollon Slope region, east-central Arizona: Arizona Oil and Gas Conservation Commission, Phoenix, Arizona. Cooley, M.E., 1958, Physiography of the Black Mesa basin area, Arizona, in Anderson, R.Y. and Harshbarger, J.W., eds., in Guidebook of the Black Mesa Basing northeastern Arizona: New Mexico Geological Society, Ninth Field Conference, p. 146-149. Cooley, M.E., Harshbarger, J.W., Akers, J.P., and Hardt, W.F., 1969, Regional hydrogeology of the Navajo and Hopi Indian Reservations, Arizona, New Mexico, and Utah: U.S. Geological Survey Professional Paper 521-A, 61 p. Craig. H., 1961, Standard for reporting concentrations of deuterium and oxygen-18 in natural waters: Science, v. 133, p. 1833-1834. Driscoll, F., 1986, Groundwater and Wells: St. Paul, Minnesota, Johnson Division, p. 102-103. Dugan, J.P. Jr., Borthwick, J., Harmon, R.S., Gagnier, M.A., Glahn, J.E., Kinsel, E.P., MacLeod, S., Viglino, J.A., and Hess, J.W., 1985, Guanidine hydrochloric method for determination of water oxygen isotope ratios and the oxygen-18 fractionation between carbon dioxide and water at 24 degrees celsius: Analytical Chemistry, v. 57, p. 1734-1736. Dunlap, R.E., 1969, The geology of the Pinta Dome-Navajo Springs helium fields, Apache County, Arizona: University of Arizona (Tucson), unpublished M.S. thesis, 73 p. Friedmund, L., 1953, Deuterium content of natural waters and other substances: Geochimica et Cosmochimica Acta, v. 4, p. 84-103. Gallaher, B., 1983, The Puerco River, Muddy issues raised by a mine water dominated ephemeral stream, in Water Quality in New Mexico—Proceedings of the 28th Annual New Mexico W ater Conference, New Mexico W ater Resources Research Institute, New Mexico State University, Las Cruces, New Mexico, report no. 169, p. 60-68. Gallaher, B.M., and Goad, M.S., 1981, Water-quality aspects of uranium mining and milling in New Mexico in Wells, S.J., and Lambert, W., eds., Environmental Hydrology and Geology in New Mexico: New Mexico Geological Society Special Publication No. 10, p. 85-92. Gallaher, B.M., and Cary, S.J., 1986, Impacts of uranium mining on surface and shallow ground waters, Grants Mineral Belt, New Mexico: Santa Fe, New Mexico, New Mexico Environmental Improvement Division Report, EED/GWH-86/2, 152 p. 105 Gilkeson, R.H. and Cowart, J.B., 1987, Radium, radon and uranium isotopes in ground water from cambrian-ordovician sandstone aquifers in Illinois, in Graves, B., ed., Radon, Radium, and Other Radioactivity in Ground Water, Hydrogeologic impact and application to indoor airborne contamination, Proceedings of the NWWA Conference: Chelsea, Michigan, Lewis Publishers, p. 283-308. Goodman, J., 1982, The Navajo atlas—environments, resources, people, and history of the Dine’ Bikeyah: Norman, Oklahoma, University of Oklahoma Press, Civilization of American Indian Series, v. 157, Gregory, H.E., 1917, Geology of the Navajo Country—A reconnaissance of parts of Arizona, New Mexico, and Utah: U.S. Geological Survey Professional Paper 93, 161 p. Guilbert, J.M. and Park, C.H. Jr., 1986, Ore deposits: New York, New York, W.H. Freeman and Company, p. 91G-921. Harrell, MA., and Eckel, E.B., 1939, Ground-water resources of the Holbrook region, Arizona: U.S. Geological Survey Water-Supply Paper 836-B, p. 19- 105. Havenor, K. and Pye, W.D., 1958, Pennsylvanian paleogeography of Arizona, in Anderson, R.Y. and Harshbarger, J.W., eds., in Guidebook of the Black Mesa Basin, northeastern Arizona: New Mexico Geological Society, Ninth Field Conference, p. 78-81. Hem, J.D., 1985, Study and intepretation of the chemical characteristics of natural water: U.S. Geological Survey Water Supply Paper 2254, 265 p. Hicks, O.N., 1969, Vegetation, in Regional Hydrogeology of the Navajo and Hopi Indian Reservations, Arizona, New Mexico, and Utah: Washington, U.S. Geological Survey Professional Paper 521-A, p. 31-34. Hostetler, P.B. and Garrels, R.M., 1962, Transportation and precipitation of uranium and vanadium at low temperatures, with special references to sandstone type uranium deposits: Economic Geology, v. 57, p. 137-167. Iverson, P., 1981, The Navajo Nation: Westport, Connecticut, Greenwood Press, 273 p. Johns, F.L., 1975, Handbook of radiochemical analytical methods, Program element 1HA325: Las Vegas, Nevada, National Environmental Research Center, Office of Research and Development, U.S. Environmental Protection Agency, 5 p. Kaufmann, R.F., Eadie, G.G., and Russell, C.R., 1976, Effects of uranium mining and milling on ground water in the Grants Mineral Belt, New Mexico: Ground W ater, v. 14, no. 5, p. 296-308. 106 Kelley, V.C., 1958, Tectonics of the Black Mesa basin region of Arizona, in Anderson, R.Y. and Harshbarger, J.W., eds., in Guidebook of the Black Mesa Basin, northeastern Arizona: New Mexico Geological Society, Ninth Field Conference, p. 136-145. Kiersch, G.A., and Keller, W.D., 1955, Bleaching clay deposits, Sanders-Defiance Plateau district, Navajo Country, Arizona: Economic Geology, v. 50, p. 469-494. Kochenov, A.V., Zinev’yev, V.V., and Lovatera, S.A., 1965, Some features of the accumulation of uranium in peat bogs: Geochemistry International 1-3, p. 65-70. Kreiger, H.L. and Whittaker, E.L., 1980, Prescribed procedures for measurement of radioactivity in drinking water: U.S. Environmental Protection Agency Report EPA-600/4-80-032, 143 p. Landa, E., 1980, Isolation of uranium mill tailings and their component radionuclides from® the biosphere—some earth science perspectives: U.S. Geological Survey Circular 814, 32 p. © Langmuir, D., 1978, Uranium solution-mineral equilibrium at low temperatures with applications to sedimentary ore deposits: Geochimica and Cosmochimica Acta, v. 42, p. 547-569. Mann, L.J., and Nemecek, E.A., 1983, Geohydrology and water use in southern Apache County, Arizona: Phoenix, Arizona, Arizona Department of Water Resources Bulletin 1 , 86 p. Millard, J., Buhl, T., and Baggett, D., 1984, The Church Rock uranium mill tailings spill—A health and environmental assessment, technical report I, radiological impacts: Albuquerque, New Mexico, New Mexico Health and Environment Department report, 92 p. Miller, J.R., and Wells, S.G., 1986, Types and processes of short-term sediment and uranium-tailings storage in arroyos—Ail example from the Rio Puerco of the West, New Mexico, in Hadley, R.F., ed., Drainage basin sediment delivery: IAHS International Commission on Continental Erosion, IAHS Publication 159, p. 335-353. The Navajo Tribe, 1983, Evaluation of the Spurlock Ranch and vicinity: The Navajo Tribe, Office of Navajo Land Development report prepared for the Navajo and Hopi Indian Relocation Commission, 55 p. Oural, C.R., Upchurch, S.B., and Brooker, H.R., 1988, Radon progeny as sources of gross alpha radioactivity anomalies in ground water: Health Physics, v. 55, no. 6 , p. 889-894. 107 Pierce, H.W., Keith, S.B., and Wilt, J.C., 1970, Coal, oil, natural gas, and helium in Arizona: Tucson, Arizona, Arizona Bureau of Mines Bulletin 182, p. 43-79, 103-121. Plummer, L.N., Jones, B.F., and Truesdell, A.H., 1976, WATEQF - A FORTRAN IV version of WATEQ, a computer program for calculating chemical equilibrium of natural waters: U.S. Geological Survey Water Resources Investigations 76-13, 61 p. Piper, A.M., 1944, A graphic procedure in the geochemical interpretation of water analysis, in Back, W. and Freeze, R.A., eds., 1983, Chemical Hydrogeology: New York, New York, Hutchinson Ross Publishing, v. 25, p. 914-923. Rackley, R., 1976, Origin of western-states-type uranium mineralization, in Wolf, K.H., ed., Handbook of stratabound and stratiform ore deposits: New York, New York, Elsevier Scientific Publishing Co., v. 7, p. 89-156. Repenning, C.A., Cooley, M.E., and Akers, J.P., 1969, Stratigraphy of the Chinle and Moenkopi Formation, Navajo and Hopi Indian Reservations, Arizona, New Mexico, and Utah: U.S. Geological Survey Professional Paper 521-B, 34 p. Repenning, C.A., Lance, J.F., and Irwin, J.H., 1958, Tertiary stratigraphy of the Navajo Country, in Anderson, R.Y. and Harshbarger, J.W., eds., in Guidebook of the Black Mesa Basin, northeastern Arizona: New Mexico Geological Society, Ninth Field Conference, Society Ninth Field Conference, p. 123-129. Runnells, D.D. and Lindberg, R.D., 1981, Hydrochemical exploration for uranium ore deposits, Use of the computer model WATEQFC: Journal of Geochemical Exploration, v. 15, p. 37-50. 1984, Ground water redox reactions, An analysis of equilibrium state applied to Eh measurements and geochemical modeling: Science, v. 225, p. 925-927. Scarborough, R., 1981, Radioactive occurrences and uranium production in Arizona: Tucson, Arizona, Arizona Bureau of Geology and Mineral Technology open-file report, 297 p. Scott, R.C., and Barker, F.B., 1962, Data on uranium and radium in ground water in the United States, 1954 to 1957: U.S. Geological Survey Professional Paper 426, 115 p. Shuey, C., 1982, Accident left long-term contamination of Rio Puerco, but seepage problem consumes New Mexico’s reponse: Mine Talk, v. 2, p. 10- 26. 108 1986, The Puerco River—Where did the water go?, in The Workbook: Albuquerque, New Mexico, Southwest Research and Information Center, v. XI, no. 1. p. 1-10. Shuey, C. and Morgan, R., 1988, Report to the Public Welfare Foundation by the Puerco River Education Project: Albuquerque, New Mexico, Southwest Research and Information Center report, 24 p., Appendix B, Historic water quality data for surface water in the Puerco River, p. B-2. Swanson, E.K., 1980, Water quality problems in the Puerco River, Arizona, in Symposium on water quality monitoring and management: Tucson, Arizona, American Water Resources Association Arizona Section, p. 99-110. Szabo, Z. and Zapecza, O.S., 1987, Relation between natural radionuclide activities and chemical constituents in ground water in the Newark Basin, New Jersery, in Graves, B., ed., Radon, Radium, and Other Radioactivity in Ground Water, Hydrogeologic impact and application to indoor airborne contamination, Proceedings of the NWWA Conference: Chelsea, Michigan, Lewis Publishers, p. 283-308. Technical Committee of the Puerco River Working Group, 1986, Final report of the Technical Committee of the Puerco River Working Group for consideration by policy representatives on July 31, 1986: Arizona Division of Environmental Health Services, New Mexico Environmental Improvement Division, and U.S. Environmental Protection Agency, 11 p. Thompson, P.J., McKlveen, J.W., and Ochoa, R., 1978, Baseline radioactivity in Arizona’s water: Health Physics, v. 34, p. 697-700. U.S. Army Corps of Engineers, 1984, Puerco River and tributaries, Gallup, New Mexico: Communication from the Assistant Secretary of the Army (Civil Works), 98th Congress, 2d Session, House Document No. 98-148, 530 p. U.S. Department of Agriculture, 1981, Little Colorado River Basin, Arizona-New Mexico, Summary report and four appendices: U.S. Department of Agriculture report, p. ?. U.S. Environmental Protection Agency, 1975, Water quality impacts of uranium mining and milling activities in the Grants Mineral Belt, New Mexico: Dallas, U.S. Environmental Protection Agency Report EPA-906/9-75-002, 128 p. 1988a, Maximum contaminant levels (Subpart B of P art 141): National Primary Interim Drinking-Water Regulations, U.S. Code of Federal Regulations, Title 40, P arts 100 to 149, revised as of July 1, 1988, p. 526- 533. 109 1988b, Secondary maximum contaminant levels (Section 143.3 of Part 143, National Secondary Drinking-Water Regulations: U.S. Code of Federal Regulations, Title 40, P arts 100 to 149, revised as of July 1, 1988, p. 607- 609. 1988c, Effluent Guidelines and Standards (Subchapter Nj, U.S. Code of Federal Regulations, Title 40, Part 414, Organic chemicals, plastics, and synthetic fibers, revised as of July 1, 1988, p. 256-283. USGS, 1988, Occurrence and movement of radionuclides and other trace elements in the Puerco and lower Little Colorado River basins, Arizona and New Mexico: U.S. Geological Survey, Water Resources Division, Arizona District, 30 p. Webb, R.H., Rink, G.R., and Favor, B.O., 1987a, Distribution of radionuclide and trace elements in ground water, grasses, and surficial sediments associated with the alluvial aquifer along the Puerco River, northeastern Arizona~A reconnaissance sampling program: U.S. Geological Survey Open-File Report 43-73, 13 p. Webb, R.H., Rink, G.R., and Radtke, D.B., 1987b, Preliminary assessment of water quality in the alluvial aquifer of the Puerco River basin, northeastern Arizona: U.S. Geological Survey Water Resources Investigations Report 87-4126, 70 p. Weimer, W.C., Kinnison, R.R., and Reeves, J.H., 1981, Survey of radionuclide distributions from the Church Rock, New Mexico, uranium mill tailings pond dam failure: Washington, D.C., U.S. Nuclear Regulatory Commission report NUREG/CR-2449. 59 p. Western Technologies Inc., 1985, Water quality investigation Navajo and Hopi Indian Relocation Commission: Phoenix, Arizona, Western Technologies, Inc., report prepared for the Navajo-Hopi Indian Relocation Commission, 13 P- Wilson, E.D., Moore, R.T., and O’Haire, R.T., 1960, Geologic map of Navajo and Apache Counties: Arizona Bureau of Mines County Geologic Map Series 3-7, scale 1:375,000. Wood, W.W., 1976, Guidelines for collection and field analysis of ground-water samples for selected unstable constituents: U.S. Geological Suvery Techniques of Water-Resources Investigations, book 1 , chap. D2, 24 p. Witkind, I.J., and Thaden, R.E., 1963, Geology and uranium-vanadium deposits of the Monument Valley area: U.S. Geological Survey Bulletin 1103, 171 p. Zito, G. and Blundell, T., 1988, Inorganic laboratory, Standard operating procedures, Quality assurance quality control program: Golden, Colorado, Barringer Laboratories Inc., 108 p. APPENDIX A. Sample Biography WESTERN PUERCO RIVER BASIN, ARIZONA GROUND - WATER QUALITY DATA BASE I u <0 rH iH. ■8 4J $ ■P s 0 8 o ) s T ■8 o 'O < & SL M s s W) (0 3 C O H • 0000 0 rH erara* m in •P -P P £ £ P •P-P i i i i 1 i m f W Em W ffl Em O •h z z z z z OS •U 0 3S a> M < CO CO COCO 00 63 4 J Or zz o»m oj vd Vi w w 3 < 63 E E S _ n o at o o H* O a* x A 0 * H*n Q)*H H P W n * O rH H H o o o o «pr*> oo A QQQQQ « l f H H W j Z « « «j iH m z w u J u w z m n a a a os ZZZZZ H o v n i * a r a r e o o v o v o n i m n i m rH n i m U U U U U 3 3 63 63 03 ID n i S S WW K >co > i a r* in - r * p » r o i o i 03 03 00 GD 03 n i n i n i ra*ra* 3 3 < t r 63 63 Z Q Q Q Q Q «C 63 63 «C H 0 0 W J rH 4 > -P C 0 0 T 'C S 0 ►, TO >!£«*S ) • P 0 0 0) C U *. *.fl p M > S 8 8 S S S 8 8 S I I I I i I i *C W w j**C i « r « 0 i D> Qi Qi IJ TI I T to a M =1 ^ 0 2 < 0 • s *• ■'J \ a 3 ( 0 J J C tJ 3 o H >43 OS 6 0 H H H H H H O t i Q c A H rHera ra* m in iiiii bUZQiO ZZZZZ Q Q u Q u w Q Q cam 03 03 00 CD CO GO 0 0 CO CO 00 CO 00 CO 0 GO 0 CO CD 00 03 03 3 63 < 63 wo zz towo zz < >a m 0) u M ^ W M 0 a H l)tf < - - < l)tf H m m jC *3 3 < 63 «*63 2 OOP P : O 'O w w (D » - m * 0 0 0 0 *0 10 0 N H H H l r tor*03oiO 43 'D H ' p I'S V rH WOr S3 32 E WJQ) Q Q Q Q Q 0 * ZZZZZ § § § § O O O O O O O O O a. a E s z s E a a. §§m H H H W l/J w w n u u A 63 63 y u y i t c 0 0 0 0 0 i t a g s s A < 0 0 o j ) a» a) cj to M d 0 10 10 id M M (0 h a .h * «h £ w s dHDD D H Id Tj CD Tj 45 H l r H S H H r H 6 £ 3 i A A 63 63 0 0 a> c a ra m E J H iJ 3 0 m O *• to 63 (8 5 •HI d oo era era id era era m r r* o - <• en o © n <*• i r-i vo ra* era n i o e a a c vo kkzzk 3C 0 C CO CO 03 CD □3 CD 03 CO COCD H* *H*H *H *H O * * * * * -O X u u u u u QQQQQ S I S S D C wo o a c rama h* w a 09 6 6 6 63 63 63 63 W *>*0 03 1 W H 1 I P H H H rH rH rH rH GO 00 CO 00 t** H rH a H r a in n i ra* rH H ra* J i I - o e t J E < < < z z z z z z z e ra Or to id id ra id id j T 2 0 O rH rH O 3 h o\ *0 & < 0) 6 33 oo 43 *0 tf 3 o 6 S n n n n n Q P - q C a r H r m r* n i ra* m era rH o* 0 p e* .p *0 *o »o *0 > Q Q Q Q Q S Em W < OS 2 u u u u u u u Q u Q Q u Q Q O H H H H M C N C O ra * C N 3 3 3 < 63 63 63 Z Z Z Z Z u a w o t w < h o M 4J 43 M 4J a> -H io *H 63 63 *H io -H a> E ra *> aj p a> rH rH rH n i n i r*»ra* * rH rH rH ra*ra* o O O O ra* ra* in 03 05 E E ra ra a a h d ra 43 ra W Mu S d _ w 0)0 a a a 1 1 T 10 HI M O 3 a) CPf CPf a) < b a r o o osa> oam d N O O N d ih 043 043 ra JB & 63 111 WESTERN PUERCO RIVER BASIN, ARIZONA GROUND - WATER QUALITY DATA BASE 1 2 T3 P $ ■P 44 ft)o ft) i& •8 44 B o u a ft) 2 as a s « o r * » 0 3 o n o mm mm ««j* z z z z z z i z z i z i j i 3 5 O < CO S 05 h3 n i n n n * * m o o f - r 05 M Cft C *H C Cft M 05 UUUUU o w w w w QQQQO N C C C CO T3 C T3 (D 13 N *H>i J T S u 0 (3 10 (3 C *0 <0 (3 flj rH flj <0 (3 *0 s ccc a>© u c Hf CXi fH rH 44 a D a 'D * 0 'O * X 3 C D << < o *H« o *. V v 3 v V*. E O O a e f H H O O in m n i n i rH CD n i fh £ 3 <3 a <3 m a t (ft«Hft) 1 CO 1 I H S O h e fh o V o ro - r ^ 3 h ^ id E U - fh in < h «. r H 0 3 r > r j * z z z z z z J z J J J H Q C O ( J ^ c TJ U H U H *j* ro(>a *h Q Q &3 D u h Q u i I S fi CQ CO S CD •* < f t M or a v a> corH C 05 05 C ) Jh hNNU V) l I l l I 3 W M O <3 a) < < *a O <3 CO S B m O1 1 1 CO £ < 1 CO VO TJ *r 'V (3 44 >* v CU rH O (ft m | O | VO « I *«• N cn i w w w w w w w w w n w w w w w w w w w H H 5 O 3 J 05 *H •H Q-EOJW 5 H 44 U *H 05 3 S 0 3 * 3 3 0 H 3 O 44 M dud <3 H - H h U o m > &3 U Da Da U &3 > : a'o o q q q a u a o d E &» a«c o a 44 < eg § £ 3 0 c r B rH B s a fH C l J CO 03 ««• ^ ^ ^ ^ o u u u u u u u s 3 5 0 Q Q Q Q c m 4J to J 4 m co a a <3 o a 'O < eg CO 3r 13 <3rH M'OCD t C ft) C H ft) 44 eft H o eft t »a ft) g e - < eg < < i f CO r o o - r rH I e 1 103 1 1 1 e 1 \ r* co n i r-* I l ' H C v H n ( o o o o o fh D U * P J J H 03 CO o a rH 3 3 D 3 D CO CO C/3CO CO CD CD CD CDCD CO CO CO COc/3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 4 4 JO 0 0 0 0 eg 0 0 0 0 3 03 03 03 03 03 03 g e 04 04 04 03 Og f OJ 04 04 U o c U o c o U c o c U o c 3 ( CO CO CO CO CO CO CO CO W CO CO CO CO CO CO ) ! C 9 CO C CO COCO W U 3 C (0 CO U (0 (0 CO i o ai > i f E O 3 B> 4J c3 >,4= a) a> w 5 ) CJV 3 Q) H 3 n in o c 03 co a co z coa D O O O - CD O 3 03 03 3 *rift) a! S < f z 'D'D'O'O H O H S CO C/3 S S egeg «c < eg eg ) 4 £ i c 3 <3 3 S <3 OHH1 H H O I f H < j s co co s j < H CO U 3 3 ' n'O ♦ 03 o*. O *H O o*. i m rH IM j J H O H O j h 0 S3 h *>< ) § in in n i a a a io io a co HrH n i n i H* *H rH f E E E <3 (3 a a H h f r>- TJ f < H H H H H H H O O O O rH O o O ov O o c O - r vo rH «H *rt J 4 M ♦H o» rH D D D D H H W H H 0 3 CO CD CD 03 CD CD CO vo 3 0 vo vo vo CO CO Oft CO co co co co CO OftCO CD CD CD Q CD CO CO CO CO co H HJ aFH rH 'O g g < < < < s « eg eg O O ( COCO 3 h h i3 O h z aa a z a a <3 (3 ft) H x)> <3 ft) > > t ( ft) (0 ft) *0 ^ ^ ^ ^ ^ 3 vm I eg eg eg eg eg eg E (3 a E tn a D a J AJ JJ f H f f H H HHF WESTERN PUERCO RIVER BASIN, ARIZONA GROUND - WATER QUALITY DATA BASE 2 8 8 2 'O i a 4J O 'O 4J O §L J-i 8 W W id 0 M HrH o o o o o •H *H -H *H *r| *H -H *H •H £ £ £ OOOOO £ £ •H «H *rl *H *H *H *rl «H •H \ 3 5 Q i iQ iQ *5 T3 in i n i n i n t i u n i n i n i n i n i m n i - t r- - r - r * t- r-* O H H H O O O O O O O O N 4J J J S J 4 N J 4 cn a J » 4 4 4J 4J 4J -»J 4J L E L ( CL L L L CL CL CL & CL s id os u S3 u § § 33335 § § § 55555 § § § § § N 4J N J 4 N J 4 N M 9 M D M tH if Q tft i 0M ) i ( Id ) 7<0 i (d f Id t Id )f t ] f t ) a a a a vo r-» ® o o i iQ T) cn cn - lHiHm d id c id e 0)0) i o h to to h s s s s s E H CQ CQ i f f CQCQ •g-g-l n < os in in in in in in in in in in c vo o i o \ co n i n i n i n i n i n i n i n i n i n i n i *“ x X c z cn X x ® j o ---- v v h j-g £ n c h .— v ® v o p o ovp — * r. E H cn o y y y h m m a a * i u h * H H O o r - r*» - r o VO I H rH n i O * H I «*• H r * C CJ1C •H H O r H r H rH rH . O f ' H o ' O V rH rH O rH O rH COO rH ' CO' ® js id js z 5 S 8 2 8 ■ « rH h os n U cn h H J f O l C I EH r- id j o a L i g L >i id H id id o C rH U l oa vo oa l 3 n - H H &3 U U U U d cn cn ® u £ o cn » o c o tr»o vo H 3 J L H a oi M oi LH a M aua) aua) M a T nos h z j o h H H H H H • 434 9 * E H H m § 8 8 3 u a M x (d » g ft)-H £ ® O O D O O V ^ J £ ^ 5 ^ £ J 4 4J 8 S 8 W 3 * a g S ' g z z z z « ,n ,n >n ,n Z o “ o o o h ft) ft> w - id id id id u id g o> o> g > > > > > n i n i n i < TBD16 Pwell 1 B igFlow ing CH2MHill P o rtla n d ,O re g o n 0 4 /2 8 /8 7 113 WESTERN PUERCO RIVER BASIN, ARIZONA GROUND - WATER QUALITY DATA BASE rH t 2 9* 0) S TJ 8 HrH o o o o o Eh H oz os osos as u u o u u u o u u H rH rH H O H O O O 1 3 0 CO 3 0 m 3 0 J O in in o in in 3 3 * 5 3* 33 S3 Z Z 2 Z co ta 2 Z n c o o o o o o o o H H H m m «c« m m o cn oi rH m in rH H r rH 'O lO O m m <• m m h e e B <0 o* cu& * *»« m in £* 10 h H £h r H rH H r %£ rH oj i S in to in z z E 8 8 > > a (0 g a 3 2 § o> (0(0 10 (0 m rH u c co co u in in in o* CDo* in o o o o O rH in rH in H H H H H u osos as u u OJ H H H H H co' in oo in in in o* in o* in o* e <0 a t cn cn o o in r 05 S' a r H 04 04 H r O O O 00 in in r» o s s X X cncn O- CO > r m o » o r i c in j o u-s >: s s o S o u o ; 1 * e e QJO (0 <0a a (0(0 u o c c HP w 00 W W W k k k Q o j a) a> Or a o o o o o rH *£S as S o h • X X X X X Ei3b3 Ei3 Ei3 Et3 o o o o o o o o o o so n o^^ co in h o as < < H . n t/} eg S I I U I in a j= E m m E j= a in CO H CO GO B3coas I WHHH H H W II) Eh O (D <0 3 DNOH4U] tn w cn-H s cn OUS O O rH O O OUS M K t *H r r l H h •( 0 C E 0 C U M(0 * p oj cn W 33 C3 * cn ^ in in ^ cn HE11 205 Lil Silversmith Spurlock Navajo,RZ 01/09/34 HH,EE 114 WESTERN PUERCO RIVER BASIN, ARIZONA GROUND - WATER QUALITY DATA BASE I JZ'O ■S’S S fls. z > -z i t * a u -P re N o a O' i s & Q Q _ reai s y o 01 o>re e oire r a re a a> 4 •H 4 os 2 & & os 0 u 01 1 II 01 -> a J S o > w w t>*o 01 n o o o o o r*-r*- - r r» - r 0 0 0 0 0 h o o o o o w W WW 03 w a o a o a o a a o o D0 0 GD GD 03 GD03 W 10 VO vO ID J J J J J J 2 2 z J Z 2 J J c c e c c c c o»o» o>O' O' o> oi o> oi m oi p U 01 01 01 01 01 a H MO' cncn o' v)M H M a O O O M O § 1 I I I I I I 1 3 n n n n n n omr e re ( ro n m re re d (I m n n m n n n rn n n n »H M M M 5 cn 01 0',0 cn M M u § i i m *0 n * *T in u 3 •H *1-1 *H *H •H *H *0 1 t 0 0 OJ 01 0 ft)01 W 10 to Mto O O O O »H O O O O COC- O ID O' o o o o o COGO 03 GD 03 IO VO 10 10 10 a o c o c a o c o o G Q(O C QG Qff l J J J J J J J 2 J J KBHBK O'O'O'O'O' UU 01 O'O'O'O' O' U M B H M ki M B B B B r er er er er e a aa o a u a u m u o § »w w O' w wo» w I I I I1 I I C H M C 'O 'tl O'O O' M 2 01 H H 3 *H •H s M M 2 0 a a ) 3 2 01 B 2 U 01 U u z j •H "H *H iH *rt *H *H*H *H *H n nn n n n n r H C N c n ^ in vo r vo in ^ n c N C H r vm O O O O O ft) to w 10 to to c o c c o c o s o o s c c c c O'O'O'O' O' H H 2 iiiii 1 ) ) ) 0101 0) 0) 0) u B B S B B E O'O'O'O' O' 01 01 01 0) 0) M M lH M H M M HH U (0 3 e © s b re U T w H M H H m M O O'W W O' 0 2 U 3 01 01 0)) 3 OiM a 'E'O O *H rH □ra U 2 r M P H H 2 4 (0 J J O 2 3 *H -H *H *H*H i i i i) >» >i >i ii >i >i u ii oi 10 to to (0 to o o o ' O o l C ' O o ' O ' O r e r e r e r eO ' O O O O O n n re n reCOr-» r- CD - 03 03r 00 - r-«r o o c c o c o o / ' \ O O O \ O O *0**0* S J J J J * J J 2 J J H M 1 M M M iH 01 01 0) 01 0) H H H H H ^ iH H M M H H C E B fl B O'O'O' O'O' u O'O'O' O'w u 5 u § i § § 0 I I I I 1 o o o re w 2 e e e re CQ CQ re CQ O re re - / go 2 'o O a m a a 2 u h , H Q( U (U SQ •H HH H H H H H • •B _B 0> W f GO GO GO CD fft M 0) J J D Q Q Q o Q o o o o •H »H »rt *i»rt »H *H •H 3 H H h O 3 > *H tH *rt»H tH *H o OHH H H 'O U to 3 CN CN OJ CN CN CNOJ OJ CN CN CNCN CN CN in iH iH tl) 10 t/1 til (0 (0 til 01 01 t/1 01 01 10 0) tl) O O O O O CN CN CN CN CN re re cq O' O'O' O' O'O' u u u u u u i i i i 2 1 H ' B! c a B c B 01 0101 01 01 UU U BBBBB B B B B B O'O' O'O'O' 010) 01 01 0) ee rerere re re % H % O'O' W O'O' n a M % In O M O O % O % U & e e f £ cn 2 m 0)1) ) 1 ) .0 Bre re 2 0 M 'ro *o 4 > > 3 3 n 2 J J * in 4 5 2 J J U i—1 GO GO 00 00 00 (—IrH fHfH i f & Q Q O Q O O O O •H -H *H *H -H *H *H -H •H N £N$N CN CNCN CN CN (N CN CN CN CN N* W W (M) (0 i > (OMU) 01 WW W W O O O O O O O O O O O re re o'ro re E B B S B O' O'O'O' O' 010) 01 01 01 u U U O' O'O' O' O' M P M O' O'W P O' i O' a MH i O O M O S O - i § 01 T 01 >i 3 W M M > > > > > >1 >1 >1 >1 >1 >1 01 01 H i—I •—I rH i—I H GO GO GD GO GO O O O O O 010101 O Q Q Q Q •H *H•H *H*H ,C H »H ■H o o « o « CD o * o H o H rH o o o « N*N* N* * r e r e r e r e r e CQ CQ CQ CQ B 01 01 01 1-1 0 B B B EO'O'O' B B B ID fl fl ID B B B Mp 'O 'E O' O'EO' O' 01 01 0) 01 *0 ’'tJ’ u ts i N O'O'O'O' O' O P M i O O u i O O i § 'H re>i (D Moi U U U titi0 e e o rere (0 M 43 U O i ■ O B ‘H B w in •*' Z • JZ •p 115 0 re U ) 116 oo ci •rt M H 01-rt O rt EDO) 4J JJ 3 e.G ai , 0) 45 *9 j j > J J 3 J J J J _ * 0 q * > JJ 3 G Ql-rt 01 0) 0) 01 o Cna g rt ai 4 3 H rH •rt Cl rt O >i o u o ci o a 3 -rt 3 rt o I 53 3 id 3 3 3 A 3 3 3 3 xj 3 a 3 01 3 id > i ro i0 id id io oi id ai p id ►nd j j a o j j j j M »H45 *H 4J Qj fl) Cl rt W J J Q) £ £ r8 ' Q M 0) O to 01 01 W H r l r H U »*J l*H C c *o rt i u I D X H H 45 *8 0*45 A > H r l H 3 • rt G irH Id •• . Id > O H H ♦rt 01 01 0) fl id oi r t ai id a -rt o a> ai H St 3 3 ** •rt fH (0 rt rt rt o 'O a rt •rt H H 3 3 3 D 1 0 3 3 00 00 00 CD 03 00 00 00 00 ^ rH r-4 ^ rH H ^4 r t pH o o o o o O O O o o o o o o o ' o o o V) VI (0 tl] ID tf) W W U] CO CO CO CO CO CO CO CO CO CO 0) 0) 0) (1) 0) Q1 0) 01 1 to to to to to to to to to to 2 45 45 45 45 45 45 45 45 45 JQ o 3 3 id id fl 3 3 id 3 S' M h Ih M h M H M 0) 0) Cl i f l to to CO to to to to to to to rH H i ■ >—* r—* i—* i—i ri n n n f—i 15 0 ( 5 0 1 5 O C5 C5 O C3 to to to to to to to to to to ggggg ggggg D D » D S D & D D D