In cooperation with the Bureau of Indian Affairs

Results and Interpretations of U.S. Geological Survey 

Data Collected in and around the Tuba City 

Open Dump, Arizona

By Raymond H. Johnson, James K. Otton, and Robert J. Horton

Open-File Report 2009–1154

U.S. Department of the Interior

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

KEN SALAZAR, Secretary

U.S. Geological Survey

Suzette M. Kimball, Acting Director 

U.S. Geological Survey, Reston, Virginia: 2009 

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Suggested citation:

Johnson, R.H., Otton, J.K., and Horton, R.J., 2009, Results and interpretations of U.S. 

Geological Survey data collected in and around the Tuba City Open Dump, Arizona: U.S. 

Geological Survey Open-File Report 2009–1154, 125 p.

Any use of trade, product, or firm names is for descriptive purposes only and does not imply 

endorsement by the U.S. Government. 

Although this report is in the public domain, permission must be secured from the individual 

copyright owners to reproduce any copyrighted material contained within this report.
Presented on March 3 and 4, 2009, in Phoenix, Arizona, for a technical meeting 

called by the Bureau of Indian Affairs. A select number of technical experts who 

have worked on issues related to the Tuba City Open Dump were present to discuss 

their findings (data collection, results, and interpretations). Jim Otton presented 

geologic maps and cross sections in poster format during this presentation. 

1 
Abstract for this presentation. 

2 
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This talk will focus specifically on these questions. Other questions may be 

important, but are not the focus of this talk. 

3 
General categories of data collection. Each category and the data collected are 

briefly summarized in the next few slides. 

4 
MW wells were installed in the first phases of the Tuba City Open Dump 

investigations by Daniel B. Stephens and Associates on Hopi lands.
 

NAV wells were installed by Walker and Associates on Navajo lands.
 

WP wells were installed by Stantec, Inc. during the most recent investigations and 

are on Hopi and Navajo lands.
 

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ICP-MS = inductively coupled plasma – mass spectrometry 

ICP-AES = inductively coupled plasma – atomic emission spectrometery 

IC = ion chromatography 

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OFR = USGS Open-File Report 

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10 
The following maps, which were created specifically for TCOD related USGS 

reports, are included for reference. Stantec, Inc. provided additional maps related to 

the TCOD during the meeting on March 3 and 4, 2009. The discovery of elevated 

uranium concentrations at MW-07 in the initial investigations at the Tuba City Open 

Dump is what prompted additional investigations at the site. 

11 
Site location outlined in red. 

12 
Monitoring well locations. 

13 
Rock sample locations. 

14 
Residence = residence water tap sample.
 

Borings = hand auger locations.
 

Sediment = surficial grab sample locations.
 

15 
Reminder of the first key question. Format from here is to discuss each key 

question, provide conclusions and interpretations for that question, and then provide 

supporting evidence for each key conclusion/interpretation. 

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17 
Reminder on conclusion (a) related to key question number 1. 

18 
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19 
Geology by Cooley and others, 1969. This mapping was based on a much different 

scale, so the Kayenta/Navajo boundary is not that precise. Regional samples were 

collected by Laurie Wirt. Samples were also taken in the Chinle Formation at old 

mining sites (map not presented here, but is available in OFR 2009-1020). 

20 
 

As expected, rock from the Chinle Formation is elevated in uranium concentration, 

as are the sediments derived from the Chinle Formation. Chinle Formation rocks 

were collected in old mining areas and(or) prospect areas. Chinle Formation 

sediments are surficial grab samples generally taken near the rock samples of the 

Chinle Formation. Regional rocks are Navajo Sandstone and Kayenta Formation 

samples, which generally have concentrations of uranium below the crustal 

abundance. Note the slightly elevated solid phase uranium concentration in the 

regional sediments over the regional rock samples The regional sediment samples regional sediments over the regional rock samples. The regional sediment samples 

are surficial grab samples generally taken near the rock samples. Regional indicates 

Navajo Sandstone and Kayenta Formation samples in the area in and around Tuba 

City. Exact rock type and collection location details are found in OFR 2009-1020. 

21 
Chinle Formation whole rock elements are most elevated in As, Co, Pb, U, and Zn 

compared to the Navajo Sandstone and Kayenta Formation whole rock elements. 

Orders of magnitude greater concentration in the Chinle Formation are 3, 2.5, 1.5, 

2.5, and 1.5, respectively for As, Co, Pb, U, and Zn. 

22 
Only outlined boxes were flown. TCL = Tuba City landfill.
 

Very little radiation above background outside of the Chinle Formation, except for an 

area downwind of the RARE Metals Mill site (RMM in this slide and following slides).
 

23 
Flight lines for radiometric data collected during the NURE program in the Marble 

Canyon quadrangle. 

24 
Radiometric data for uranium (Marble Canyon) that has been contoured. Note 

outline of area for Chinle Formation outcrop. Note that value for crustal abundance 

of uranium at 2.7 ppm is a moderate orange color and note that this data is only 

detecting surficial material (< 5 cm). Will zoom into boxed area for the next slide.

25
Again, contoured radiometric data for uranium with same uranium concentration 

scale as last slide. RMM = RARE Metals Mill. TCL = Tuba City Landfill. Geology is 

based on Cooley and others, 1969. Note that the red area of higher uranium 

concentrations follows up the valley of Moenkopi Wash. This may be due to slightly 

higher uranium in the Kayenta Formation and(or) wind blown sediment from the 

Chinle Formation at the surface. The winds in this area often come from the 

southwest and blow up the Moenkopi Wash valley (based on personal observation 

and information from local residents) information from local residents). Dashed black Dashed black outline indicates possible outline indicates possible

elevation of uranium in surficial sediments due to wind blown deposition up the 

canyon of Moenkopi Wash. Box indicates area zoomed into for next slide 

radiometrics slide. 

26
Dust storm along Moenkopi Wash just SW of Lower Moenkopi, April 2008. Photo by 

James K. Otton. 

27 
Again, contoured radiometric data for uranium with same uranium concentration 

scale as last two slides. RMM = RARE Metals Mill. TCL = Tuba City Landfill. Black 

lines indicate flight lines and thickness is approximately equal to the area that is 

actually being detected on the ground. Note that the Tuba City landfill is not below a 

flight line detection zone. High detection of radiometrics downwind of the RMM site 

is similar to the EPA data. Note that the apparent spread to this zone to the north 

and south may be an artifact of contouring, as the only measurements detected 

were directly directly below the black flight line detection detection zone.

28
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29 
 

Rock and sediment samples were leached in a 20 to 1 ratio of DI water to solids. 

These data do not represent what actual ground water uranium concentration might 

be produced, but are used to directly compare different potential sources of 

naturally occurring uranium using a standard method to determine variations in 

soluble (leachable) uranium from different solid samples. Uranium concentrations 

are higher for Chinle Formation rocks and sediments, as expected. Note the higher 

amount of leachable uranium seen in the regional sediments compared to the 

regional rock samples Regional Navajo Sandstone and Kayenta Formation regional rock samples. Regional Navajo Sandstone and Kayenta Formation 

samples (regional rock) in and around the Tuba City area are much lower in 

leachable uranium (note that one sample was from a rock near a spring with an 

evaporitic salt coating apparently containing some leachable uranium, this adds to 

the tail on the regional rock data). Exact rock type and collection location details are 

found in OFR 2009-1020. 

30 
These key points answer the question of where the uranium in the ground water is 

derived. Will address more in the next section. 

31 
Reminder of conclusion (b) for key question number 1. 

32 
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33 
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34 
This is a summary of the evidence from the whole rock data presented in the next 

few slides. The main conclusion is that the surficial sands are not derived from 

Navajo Sandstone. 

35 
Will look at data in next slide from three sample sites for whole rock data with depth. 

WP-01 is upwind from the TCOD with 20 feet of sand and a water table at 46.8 feet 

(Stantec, Inc. borehole). B29 is a USGS hand augered hole in the gulley below the 

TCOD (11.4+ feet of sand and 12.5 feet to the water table). WP-07 is a Stantec, Inc. 

borehole with 5 feet of sand over Navajo Sandstone and a water table at 17.5 feet 

deep. 

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37 
38 
39 
Most values for uranium are below crustal abundance (agrees with radiometric 

data). Main “salt” concentration zones occur above the water table. Navajo 

Sandstone in WP-07 is low in most all elements, especially below the water table. 

Water table for B29 = 12.5, WP-07 = 17.5, and WP-01 = 46.8 feet below ground 

surface. 

40 
TC08SS02 is a surficial grab sample and WP-07 sample is from 17.4 foot depth 

(Navajo Sandstone). SEM = scanning electron microscope. Note large amount of 

surficial coatings (secondary mineral precipitation and(or) blown in?) in TC08SS02. 

Shallow sand has a greater number of smaller grains. SEM images taken by 

Raymond H. Johnson. 

41 
Example of secondary mineral precipitation of strontianite (strontium carbonate) in 

WP-01 sample (at 27.5 feet). This is 20 feet above the water table. This 

demonstrates likely active precipitation and dissolution of strontianite occurring in 

the vadose zone. SEM images taken by Raymond H. Johnson. 

42 
Significant landmarks to see on dc line L9 in next slide are north gully (at MW-23), 

south gully crossing (just before WP-05), MW-07, and the portion of the old dump. 

dc = direct current. 

43 
Well depths are drawn to scale. A highly conductive zone near the surface between 

WP-05 and MW-23 is most likely a damp salt zone. This is confirmed by borings in 

the area, which do not indicate significant clay zones. Note that resistivity surveys 

would detect dry salt zones as very resistive, thus a water table close to the surface 

is required to detect these zones with dc resistivity. 

dc = direct current. 

44 
Significant landmarks to see on dc line L2 in next slide are north and south gully 

crossing, MW-07, and the edge of the old dump.
 

dc = direct current.
 

45 
Well depth is drawn to scale. Similar evidence of “salt” zones in the vadose zone 

along south gully. These profiles will be revisited later in the talk from the aspect of 

transferring the “salts” into the ground water. 

dc = direct current. 

46 
Red outline highlights the four landfill wells that show some evaporation (lie below 

the LMWL near the green line). Arrow points to a hand-dug well sample that shows 

a strong evaporation signature. GMWL = global meteoric water line and LMWL = 

local meteroic water line. All other samples are regional water (OFR 2009-1020). 

47 
48 
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49 
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50 
Regional water table based on spring elevations; generally follows topography. 

51 
Conceptual cross section based on expected ground-water flow in a regional 

setting. Note that shallow and deep ground water may discharge at Pasture Canyon 

and Moenkopi Wash. 

52 
Some regional water samples do show elevated uranium concentrations in shallow 

ground water. Highest is Goldtooth Spring at 41 ppb. Zoom into boxed area for next 

slide. 

53 
54 
55 
READ – “modern” precipitation can mean within the last few thousand years. 

56 
Significant landmarks to see on dc (direct current) line L1 in next slide are north and 

south gully crossing, MW-07, and the edge of the old dump. 

dc = direct current.
 

57 
Well depth is drawn to scale. Areas with red outlines are zones of more conductive 

ground water (no change in geology based on borings in the area), which appear to 

be close to highly conductive zones in the above vadose zone. Note that the north 

gully has few ground water samples, except for the Begay hand-dug well (no USGS 

data for this well, but reported by Brown and Caldwell, 2008 as 580 uS/cm specific 

conductance). 

dc = direct current. 

58 
Significant landmarks to see on dc line L9 in next slide are north gully (at MW-23), 

south gully crossing (just before WP-05), MW-07, and the portion of the old dump. 

dc = direct current. 

59 
Well depths are drawn to scale. 

dc = direct current. 

60 
Leaching of uranium ore-bearing material (Chinle rock and mill tailings) produce a 

ratio near 1. This is because the ore material is near secular equilibrium (long 

enough time for uranium decay series to reach similar U-234 and U-238 

concentrations). Dissolution of the soluble uranium gives values similar to or less 

than the rock values (1 or less). In slow moving ground water, the alpha recoil 

mechanism produces uranium isotope ratios greater than 1 (Zielinski and others, 

1997). 

61 
Uranium isotope ratios from TCOD ground-water samples overlap with regional 

waters and regional rock and sediment leachates. Leachate from Chinle rock and 

sediment do not overlap with the TCOD ground water samples for uranium isotope 

ratios. 

62 
Blue tones generally indicate shallow ground water and red tones generally indicate 

deeper ground water (this is confirmed by geochemistry and tritium/C-14 data). The 

red outline indicates the zoomed in area shown on the next slide. 

63 
Blue tones generally indicate shallow ground water and red tones generally indicate 

deeper ground water (this is confirmed by geochemistry and tritium/C-14 data). This 

slide is the zoomed in area shown in red on the previous slide. 

64 
Data source from DOE Office of Legacy Management web site 

(http://gems.lm.doe.gov/imf/imf.jsp?site=tubacitydisposal&title=Tuba City, AZ, 

Disposal Site). 

UMTRA = Uranium Mill Tailings Remedial Action. 

65 
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66 
Conceptual model of ground water flow and associated data. Evaporation (evap) is 

considered based on 18O and deuterium isotopes. Susungva Spring stands out as 

being on a deep ground-water flow path containing N-aquifer water. Other wells are 

on a more shallow ground water flow path. Note that the uranium isotope ratios for 

TCOD up gradient well and MW-07 are similar (does not allow for a mixing 

scenario). 

67 
READ. Reminder of key question #2. 

68 
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69 
READ. Reminder of key conclusion/interpretation 2a. 

70 
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Water table elevations are in feet above mean sea level.
 

71 
READ. Reminder of key conclusion/interpretation 2b. 

72 
READ. uS/cm = microsiemens per centimeter. 

73 
Significant landmarks to see on dc (direct current) line L1 in next slide are north and 

south gully crossing, MW-07, and the edge of the old dump. 

74 
Well depth is drawn to scale. Plume is indicated by higher conductivity below the 

water table. Note that higher conductivity zones could indicate higher clay content 

(or general change in geology), but this was not noted in the well logs for MW-07. 

75 
Significant landmarks to see on dc line L9 in next slide are north gully (at MW-23), 

south gully crossing (just before WP-05), MW-07, and the portion of the old dump. 

dc = direct current. 

76 
Well depth is drawn to scale. 

77 
READ. Reminder of key conclusion/interpretation 2c. 

78 
READ. uS/cm = microsiemens per centimeter. 

79 
Significant landmarks to see on dc line L2 in next slide are north and south gully 

crossing, MW-07, and the edge of the old dump. 

80 
Well depth is drawn to scale. 

81 
82 
Note the labels on lines are slightly different. For example dc1 = L1 in other images. 

Black outline = plume extent? 

83 
84 
READ. Reminder of key conclusion/interpretation. 

85 
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86 
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87 
Black boundary indicates area zoomed into for next slide. 

88 
Green line indicates the idea of following a ground-water flow pathline downgradient 

from MW-06 

89 
90 
READ. Reminder of key question #3. 

91 
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92 
READ. Reminder of key conclusion 3a. 

93 
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94 
Uranium uptake by shallow sands at the TCOD is generally 60-100 percent, which 

suggests limited mobility for uranium. 

95 
Example of variation in dissolved oxygen and some locations with low dissolved 

oxygen measurements. A fully DO saturated water would be approximately 8 mg/L. 

Low DO could produce dissolution of Fe coatings with release of any associated 

uranium. 

96 
97 
Plots use all of Stantec’s ground water sampling data in 2008 from all wells with 

both alkalinity and uranium values. This suggests the increased mobility of uranium 

when it is complexed as a carbonate-uranyl species. 

98 
Uranium and other constituents were initially concentrated by evapotranspiration 

and other processes discussed earlier. 

99 
TCLP leach is meant to simulate landfill leachate. 

100 
READ.
 

101 
Most values for uranium are below crustal abundance (agrees with radiometric 

data). Main “salt” concentration zones occur above the water table. Navajo 

Sandstone in WP-07 is low in most all elements, especially below the water table. 

Water table for B29 = 12.5, WP-07 = 17.5, and WP-01 = 46.8 feet below ground 

surface. 

102 
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103 
 

 

 

Here are some important details for interpreting the geochemical profiles: 

Slight dampness first noted in the 32-43 inch interval (2.67 to 3.58 feet).
 

The 43-59 in interval (3.58 to 4.92 feet) is siltier than the intervals above and below. 

It is also pale red in color. There was no caliche observed.
 

Traces of soft, punky, calcite-cemented material from 103 to 112 inches (8.58 to 

9.33 feet), possible older caliche zone now mostly gone (dissolved away?). 

From the geochemical data it is apparent that From the geochemical data it is apparent that “salts ” are accumulating in the 36 are accumulating in the 36-60 

inch (3 to 5 foot) interval where the silty zone occurs. 

Almost no leachable U below 10 feet. This may represent systematic removal of 

uranium from the sediment in the zone where the water table fluctuates up and 

down. Evidence for this leaching in the geologic logging observations: above 10 

feet, the sand is light to moderate red-orange except in the silty zone where it is 

pale red in color and below ten feet the sediment is mottled to streaky light to pale red in color, and below ten feet, the sediment is mottled to streaky, light to 

moderate red-orange with mottles that vary in color including moderate yellowbrown, pale gray-orange, yellow-gray, gray orange-pink (some darker streaks of 

pale red also occur). 

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105 
There is so little geologic detail here that there is a limited amount to say.
 

Caliche present from 6 feet to about 7 feet in the weathered bedrock. This appears 

to be the zone of salt and trace metal accumulation. Note that the detection limit for 

uranium was 0.1 ug/L. Samples below the detection limit are plotted as 0.05 ug/L.
 

106 
107 
Note that the detection limit for uranium was 0.1 ug/L. Samples below the detection 

limit are plotted as 0.05 ug/L. 

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110 
Note that chloride and sulfate for DI versus TCLP are not much different. Major 

difference is the increased calcium, alkalinity, conductivity, and uranium with the 

TCLP leach. Probably dissolves all of the calcite. Is uranium from the calcite and(or) 

iron oxide coatings? What is the influence of uranium complexes? 

111 
Note that chloride and sulfate for DI versus TCLP are not much different. Major 

difference is the increased calcium, alkalinity, conductivity, and uranium with the 

TCLP leach. Probably dissolves all of the calcite. Is uranium from the calcite and(or) 

iron oxide coatings? What is the influence of uranium complexes? 

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This presentation has focused specifically on these questions. Other questions may 

be important, but are not the focus of this presentation. 

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