section 8 / navajo-gallup groundwater report and ... · this report discusses the results of the...

Daniel B. Stephens & Associates, Inc. 6020 Academy NE, Suite 100 • Albuquerque, New Mexico 87109

Section 8 / Navajo-Gallup

Groundwater Report and

Conjunctive Use Evaluation

Prepared for Navajo Nation, City of Gallup, and

Uranium Resources, Inc.

October 29, 2012

D a n i e l B . S t e p h e n s & A s s o c i a t e s , I n c .

Table of Contents

Section Page

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

2. Summary of Proposed Project ................................................................................................ 2

3. Water Supply Wells................................................................................................................. 4 3.1 Existing Wells .................................................................................................................. 4 3.2 Planned NGWSP Groundwater Development................................................................. 5

4. Hydrogeologic Conditions .......................................................................................................7 4.1 Geology ........................................................................................................................... 7 4.2 Hydrogeology .................................................................................................................. 8 4.3 Aquifer Hydraulic Properties.......................................................................................... 10

4.3.1 Alluvial Aquifer.................................................................................................... 11 4.3.2 Major Mesozoic Sandstone Aquifers .................................................................. 11 4.3.3 Minor Mesozoic Sandstone Aquifers .................................................................. 12 4.3.4 San Rafael Group............................................................................................... 13 4.3.5 Chinle Group ...................................................................................................... 13 4.3.6 San Andres-Glorieta Aquifer............................................................................... 13

4.4 Groundwater Quality...................................................................................................... 14 4.4.1 Alluvial Aquifer.................................................................................................... 15 4.4.2 Point Lookout Sandstone and Menefee Formation of the Mesa Verde

Group.................................................................................................................. 15 4.4.3 Gallup Sandstone Aquifer................................................................................... 15 4.4.4 Dakota Sandstone Aquifer.................................................................................. 15 4.4.5 Morrison Formation and Westwater Canyon Aquifer.......................................... 16 4.4.6 San Rafael Group............................................................................................... 16 4.4.7 Chinle Group ...................................................................................................... 16 4.4.8 San Andres-Glorieta Aquifer............................................................................... 17

5. Conjunctive Use Well Placement Constraints....................................................................... 18 5.1 Physical Constraints ...................................................................................................... 18 5.2 Land Ownership Constraints ......................................................................................... 19

6. Assessment of Potential Impacts from Section 8 ISR........................................................... 21 6.1 ISR Operations .............................................................................................................. 21 6.2 Potential for Impacts from Section 8 ISR....................................................................... 22

7. Summary and Conclusions ................................................................................................... 26

References.................................................................................................................................. 28

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List of Figures

Figure

1 Study Area

2 Conceptual Design of ISR Process

3 Existing Well Locations

4 Navajo Chapters Where Future Conjunctive Use Wells Could Be Constructed

5 Surface Geology Map

6 South to North Geologic Cross Section A-A’

7 Southwest to Northeast Geologic Cross Section B-B’

8 Geologic Block Diagram Showing Cross Sections A-A’ and B-B’

9 Conceptual Diagram of a Layered Aquifer System

10 Observed Morrison Formation Water Levels and Groundwater Flow Direction in the Southern San Juan Basin, New Mexico

11 Simulated Pre-Development Water Levels for Aquifers Near the Section 8 Site

12 Topography

13 FEMA Flood Hazard Areas

14 Probable Maximum Flood Floodplain

15 Surface Ownership

16 Subsurface Ownership


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List of Tables

Table

1 City of Gallup Existing Well Information

2 Navajo Nation Existing Well Information

3 Recommended Municipal Conjunctive Groundwater Development, Navajo-Gallup Water Supply Project

4 Navajo Nation Conjunctive Groundwater Projects

5 General Hydraulic Characteristics of Aquifers Near Section 8

6 Aquifer Properties of the Westwater Canyon Member Within Section 8

7 General Chemistry Water Quality Statistics Summary

8 Trace Elements Water Quality Statistics Summary


1. Introduction

Uranium Resources, Inc. (URI) has contracted with Daniel B. Stephens & Associates, Inc.

(DBS&A) to complete a Section 8/Navajo-Gallup Groundwater Report and Conjunctive Use

Evaluation that (1) presents the hydrogeologic conditions in the vicinity of URI’s proposed

Section 8 uranium in situ recovery (ISR) project, and (2) assesses the risk for future

contamination from proposed URI ISR activities of groundwater supply to be developed and

conjunctively used as part of the Gallup regional water system component of the Navajo-Gallup

Water Supply Project (NGWSP). Although URI contracted and paid for this study, the study is a

collaborative effort between URI, the City of Gallup, and the Navajo Nation. The study scope

was developed jointly by these entities, and all information and analysis has been shared

equally with all parties. This report discusses the results of the technical evaluation and

presents DBS&A’s findings.

The area of review for this project is the 10-mile radius from the center of Section 8,

Township 16 North, Range 16 West, McKinley County, New Mexico (Figure 1), and all City of

Gallup well locations, all of which are located outside of the 10-mile radius. Data sources used

include published reports, City of Gallup well records, the Navajo Nation Department of Water

Resources (NNDWR) wells database, and other publicly available data. The Navajo Nation

supplied their chapter boundaries for inclusion on report figures as appropriate. Figure 1 shows

the project location and 10-mile radius of interest and its proximity to the City of Gallup and

Navajo Nation chapters. As illustrated by the inset image in Figure 1, the ore body to be mined

is approximately 2,200 feet by 800 feet in the southeastern quarter of Section 8.

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2. Summary of Proposed Project

URI is developing an ISR operation to extract uranium from the Westwater Canyon Member of

the Morrison Formation, which is a sandstone. The process involves injection of an oxidizing

solution called lixiviant into the geologic zone of interest at injection wells, and extraction of the

lixiviant at pumping wells. At the Section 8 site, URI proposes to use a lixiviant composed of

native groundwater enriched with oxygen. The injected lixiviant, containing low concentrations

of uranium, is termed “barren”. As the barren lixiviant flows through the sandstone from the

injection wells toward the extraction wells, it dissolves uranium minerals that have been

deposited on grains of sand that compose the sandstone. In this way, the barren lixiviant

continues to dissolve uranium minerals into solution, and the uranium stays in solution as the

soluble uranyl carbonate ion [UO2(CO3)]. The uranium-rich lixiviant (referred to as “pregnant”

lixiviant) is removed from the sandstone at pumping wells. At the surface, uranium is removed

from the pregnant lixiviant using an ion-exchange process. The lixiviant is then recharged with

oxygen and is reinjected into the ore body to recover additional uranium. The general nature of

the proposed ISR operation is illustrated conceptually in Figure 2.

Several types of wells are used in the uranium recovery process, including injection wells to

deliver the barren lixiviant to the ore zone, extraction wells to remove the pregnant lixiviant from

the ore zone and bring it to the surface, and a network of monitor wells for collecting water level

and water quality data across the site (Figure 2). The injection and extraction wells will be

placed across the ore body in a network designed to efficiently recover uranium through the ISR

process; these wells will be screened at specific depth intervals that correspond to mineralized

zones within the Westwater Canyon Member. The monitor well network is designed to surround

the area from which the uranium ore is recovered, so that any excursions of lixiviant not

extracted by the pumping wells can be detected. Monitor wells would also be completed in the

immediately overlying and underlying geologic units to determine any excursions in the vertical

direction (i.e., above or below the Westwater Canyon Sandstone).

Ore-grade concentrations of uranium are present in the Westwater Canyon Member of the

Morrison Formation, and the ore-bearing zone is reported to contain mineralization at a grade of

approximately 0.15 percent uranium oxide (U3O8). The Westwater Canyon Member is a



sandstone unit that is found between two lower-permeability rock units: the Brushy Basin

Member, which is a bentonite clay, and the Recapture Shale. These low-permeability units will

naturally confine the lixiviant within the ore zone, allowing greater control of the injection and

recovery processes.

The injection and recovery processes control the movement of the leach solution in the ground.

As the lixiviant is pumped into the ground, pumping by a series of extraction wells pulls

groundwater and pregnant lixiviant toward these capture wells. The lixiviant will not travel

significantly upgradient from the injection wells due to the local hydraulic gradient and capture

zone created by the extraction wells. URI will extract more water than is injected in order to

maintain an overall hydraulic sink in the ore body.

Upon cessation of the active uranium recovery activities, URI proposes to remediate

groundwater at the site by continuing to circulate groundwater without adding oxygen (i.e.,

lixiviant will no longer be injected). If uranium concentrations are high enough, uranium

recovery may continue during a portion of the site remediation period. In addition, reverse

osmosis (RO) will be applied to treat elevated solute concentrations in the extracted

groundwater. The concentrate from the RO process will be injected into a deep well or

otherwise disposed of in accordance with regulatory requirements. Water quality in monitor

wells will be monitored during this phase of the ISR operation as well to detect any excursions

of impacted groundwater away from the mined area. When the water quality returns to

acceptable levels as determined by baseline water quality analysis, the injection and extraction

system will be shut down, allowing the natural hydraulic gradient within the Westwater Canyon

Sandstone to be restored over time.



3. Water Supply Wells

DBS&A compiled an inventory of existing wells and possible locations of future wells in the area

of review using data provided by the City of Gallup, the Navajo Nation, and as generally

described by the NGWSP Planning Report and Final Environmental Impact Statement (FEIS)

(USBR, 2009) and the Conjunctive Groundwater Development Plan (NNDWR, 2010). The

results of this compilation are provided below.

3.1 Existing Wells

The City of Gallup provided well location and construction data for the City’s existing wells

(Table 1) (Thompson, 2012). The City has 17 wells completed in two well fields: (1) the

Ya-ta-hey well field located north of Gallup, which includes the City’s high-producing wells, and

(2) the Santa Fe well field located in town. All of the City’s wells are located west of the 10-mile

radius study area (Figure 3). These wells extract groundwater from the Gallup Sandstone,

Dakota Sandstone, and Westwater Canyon Member of the Morrison Formation aquifers. Most

of the City’s wells have multiple screened intervals, and some wells are completed across

multiple aquifers (Table 1).

The Navajo Nation provided well location and available construction data for 54 documented

wells within the study area (Foley, 2012), 7 of which have been abandoned. The 47 existing

wells (not abandoned) are plotted in Figure 3. These wells occur throughout the 10-mile radius

area of interest and obtain water from 1 or more of 13 aquifers identified in the region: alluvium,

Mesa Verde Group (Dalton Sandstone Member, Crevasse Canyon Formation, or Menefee

Formation), Gallup Sandstone, Dakota Sandstone, Westwater Canyon Member of Morrison

Formation, Entrada Sandstone, San Andres Limestone, Glorieta Sandstone, Chinle Group, and

Todilto Limestone (Table 2).

Other supply wells identified in the study area are also included on Figure 3, including wells for

Fort Wingate Army Depot and Rehoboth Christian School; locations for these wells were

obtained from the New Mexico Office of the State Engineer (OSE) Water Rights Reporting

System (WATERS) database (NM OSE, 2012). The WATERS database was also searched for



New Mexico Department of Transportation (NMDOT) wells located within the Gallup

underground water basin; none were identified within the region of interest.

3.2 Planned NGWSP Groundwater Development

The purpose of the NGWSP is to provide for the long-term (year 2040) supply, treatment, and

transmission of municipal and industrial water to the Navajo Nation, the City of Gallup, and the

Jicarilla Apache Nation. The NGWSP includes a conjunctive groundwater component to

supplement surface water diversions from the San Juan River. The FEIS called for the Navajo

Nation to complete a conjunctive groundwater development plan, which was completed in 2010

(NNDWR, 2010).

Both the FEIS and conjunctive groundwater development plan discuss planned groundwater

development on the Navajo Nation. The conjunctive use wells are limited to municipal and

domestic purposes, with maximum groundwater diversions by basin of 1,670 acre-feet per year

(ac-ft/yr) in the San Juan Basin in New Mexico, 680 ac-ft/yr in the Little Colorado River Basin in

New Mexico, 80 ac-ft/yr in the Rio Grande Basin in New Mexico, and 770 ac-ft/yr in the Little

Colorado Basin in Arizona (USBR, 2009).

The NGWSP FEIS evaluates many alternatives and presents the San Juan River Public Service

of New Mexico (SJRPNM) alternative as the preferred alternative (USBR, 2009). The SJRPNM

alternative calls for diverting water from the San Juan River downstream of Fruitland, New

Mexico, just above the existing Public Service of New Mexico (PNM) diversion structure,

treating the water, and delivering it along Highway N36 and U.S. Highway 491, as well as

diverting water from Cutter Reservoir, an existing Navajo Indian Irrigation Project reservoir, and

delivering it to the eastern portion of the Navajo and Jicarilla Apache Nations (USBR, 2009).

The NGWSP also calls for conjunctive groundwater development; the initial recommended

number of wells and their locations are included on Table 3 (USBR, 2009). Groundwater

development is recommended for five of the eight Navajo chapters that are included within the

study area. A total of 11 wells are proposed in the FEIS, within the Chinle Group, Dalton

Sandstone of the Crevasse Canyon Formation, Glorieta Sandstone, and Gallup Sandstone

aquifers (Table 3). The estimated well depths range from 1,500 to 2,000 feet below ground



surface (bgs), and the projected well yields are between 20 and 125 gallons per minute (gpm)

(Table 3).

The Navajo Nation Conjunctive Groundwater Development Plan (NNDWR, 2010) identifies and

prioritizes construction and rehabilitation of Navajo community water system wells and related

facilities within the NGWSP service area. An initial list of potential projects was drafted as a part

of the conjunctive groundwater development plan, and the plan calls for a more detailed

assessment of wells and pipeline facilities, project ranking, and design. The conjunctive

groundwater projects planned for Navajo Nation Chapters located within or near the 10-mile

radius of interest are summarized in Table 4 and Figure 4. A total of 33 wells are proposed

within the following aquifers: alluvium, the Menefee Formation of the Mesaverde Group, San

Andres Limestone and Glorieta Sandstone, the Westwater Canyon Member of the Morrison

Formation, the Entrada Sandstone, and the Gallup Sandstone. Target well depths range from

160 to 3,500 feet bgs. As the NNDWR (2010) document is the most recent report available on

potential conjunctive use well locations and target aquifers, it is assumed that information

provided in this document supersedes that provided in USBR (2009) with respect to the

conjunctive groundwater use components of the NGWSP.

The City of Gallup has also investigated possible new appropriations of groundwater from the

San Andres-Glorieta aquifer under New Mexico OSE application number G-22, although the

application has been protested. The Navajo Nation and the City of Gallup reached a settlement

over the Navajo Nation objections, but other protestants remain. If the City is successful in

obtaining approval of its G-22 application, the new water supply may provide a partial short-term

supply until the NGWSP can be completed (USBR, 2009) and will provide a groundwater

reserve during periods of NGWSP surface water shortages (Allgood, 2012). Based on

information in the WATERS database (NM OSE, 2012), five of the proposed G-22 wells (POD4

through POD8) are located east of Gallup near the southwest boundary of the 10-mile radius

area of interest. The approximate depth for these proposed wells is 4,000 feet.



4. Hydrogeologic Conditions

This section presents the hydrogeologic conditions in the vicinity of URI’s proposed Section 8

uranium mining project, and includes a description of the hydrogeologic conditions in the area of

review. Sections 4.1 and 4.2 provide an overview of the study area geology and hydrogeology,

respectively. Section 4.3 briefly summarizes aquifer hydraulic properties. Section 4.3

summarizes water quality information.

4.1 Geology

The hydrogeology of the study area is dominated by sandstone aquifers that occur in rocks of

the Mesozoic Era (Triassic, Jurassic, and Cretaceous age rocks) and the Permian San Andres-

Glorieta aquifer, which is composed of the San Andres Limestone and the Glorieta Sandstone.

Each of the sandstone units is considered a regional aquifer and has been studied by the

U.S. Geological Survey (USGS) to determine water resource potential for potable and other

uses. The sandstone aquifer units are separated by intervening units of low-permeability rocks,

primarily shale. A generalized surface geologic map is provided is provided as Figure 5. The

region where each of the geologic units occurs at the land surface is called the outcrop area for

that unit.

Figure 5 also provides the locations of two geologic cross sections. A cross section is a

representation of the geology in the vertical direction from the land surface to a selected depth

below the land surface. The south to north cross section A–A’ is provided in Figure 6; the

southwest to northeast section B–B’ is provided in Figure 7. Figure 8 is a geologic block

diagram of the geology in the vicinity of the study area; it provides a three-dimensional

perspective of the information provided in Figures 5 through 7.

Review of Figures 5 through 8 illustrates the major geologic units and their distribution at and

beneath the surface within the study area. The “banded” nature of the geologic units at the

surface (Figure 5) is evident in the south-north cross section (Figure 6). This geology is typical

of a sedimentary basin such as the San Juan Basin. The study area lies on the southern edge

of the basin, and the geologic units dip (slope downward) to the north toward the basin center.



The geology has a layer cake appearance with older geologic units occurring deeper in the

section and younger units found at shallower depths.

The area near Gallup is underlain by a complex geologic structure called the Nutria Monocline,

where the rocks have been folded by geologic forces and the strata resemble an “S” shape

(Figures 7 and 8). On the west side of the monocline, geologic units will be encountered at

greater depths compared with areas east and northeast of the monocline. The rocks in the

Gallup area have also been deformed into a series of folds called the Gallup Anticline and

Nakaibito Syncline (Figures 7 and 8).

4.2 Hydrogeology

Within the layered geologic sequence presented above, sandstones (and limestone where it

occurs) typically act as aquifers because of their ability to transmit significant quantities of

groundwater as compared to other geologic units such as shale and mudstone. The sandstone

and limestone units have high hydraulic conductivity compared to the shale units, which have

low hydraulic conductivity. Recharge areas are the regions where precipitation, snowmelt or

streamflow can infiltrate from the land surface to the water table. The primary recharge areas

for each sandstone unit occur where the unit outcrops at the land surface (Figures 6 and 7). As

groundwater flows from the outcrop area into the basin, it generally becomes “confined”

between lower-hydraulic conductivity units (e.g., shale) that occur above and below the

sandstone aquifer unit. This confinement and differences in elevation cause pressure to build in

the aquifer in the direction of groundwater flow, and the aquifer is referred to as a confined

aquifer. If a well is completed in a confined aquifer, the water level in the well will rise to level

above the top of the aquifer. This type of groundwater system is illustrated conceptually in

Figure 9. Groundwater may flow between aquifers under confined conditions, although the rate

of flow is generally quite small compared to that which occurs in the aquifer units. A USGS

evaluation of chemistry and potential mixing between aquifers in the San Juan Basin (Dam,

1995) determined that upward leakage was possible between aquifers based on water quality

data.



At the Section 8 site, the primary aquifer of interest is the Westwater Canyon Member of the

Morrison Formation, as this is the unit that will be the target of ISR. Here the Westwater

Member is “sandwiched” between the underlying Recapture Shale and the overlying Brushy

Basin Member of the Morrison Formation. The Entrada Sandstone aquifer of the San Raphael

Group underlies the Morrison Formation, but is separated from it by the low-hydraulic

conductivity Recapture Shale. The Dakota Sandstone aquifer occurs above the Morrison

Formation and is separated from it by clay in the Brushy Basin Member of the Morrison

Formation.

Rocks exposed at the ground surface at the Section 8 site belong to the Cretaceous Mancos

Shale. The Mancos Shale consists of a thick sequence of shale with some interbedded

sandstones; it is a low-hydraulic conductivity unit that generally will not yield usable quantities of

water to wells. Below the Mancos Shale is the Dakota Sandstone, which is used as a water

supply at some locations in the study area.

The potentiometric surface of the Morrison Formation aquifer (which includes the sandstone of

the Westwater Canyon Member) begins at recharge areas where the rocks outcrop (Figures 10

and 11). The natural groundwater flow direction in all of the aquifers at the site is toward the

north into the San Juan Basin, where the groundwater eventually discharges along the San

Juan River. Some groundwater may also seep upward to overlying aquifer units within the

basin. Figure 10 shows the potentiometric surface of the Morrison for the late 1980s based on

data from the USGS. During this time frame, groundwater levels were recovering following

mine dewatering activities related to conventional underground mining for uranium. The

conventional mining occurred at levels below the water table and required that the Morrison

Formation and often the Dakota Sandstone aquifers be dewatered to allow excavation and

mining. Although the water levels in the study area were affected (lowered) due to past mining

at other sites, the direction of groundwater flow remained essentially the same.

Figure 11 shows simulated steady-state potentiometric head values for the Dakota Sandstone,

Morrison Formation, and Entrada Sandstone based on a USGS groundwater flow model

(Kernodle, 1996). The data indicate that each unit is recharged at the outcrop area from which

groundwater flows north into the San Juan Basin or west across the Nutria Monocline. The

model results represent pre-development conditions of the basin and indicate that water levels



were lowered hundreds of feet by previous mine dewatering. The limited amount of net

pumping that will occur as part of the Section 8 ISR project is not expected to have the same

impact.

During mining the groundwater in the Westwater Canyon Member will be drawn toward the

extraction wells. More water will be extracted than injected to ensure that the gradient remains

toward extraction wells at all times during operations. Following mining the natural groundwater

flow direction and gradient (slope of the potentiometric surface) will slowly restore itself as

groundwater from recharge areas and upgradient of the site flows through the Westwater

Canyon Member. The natural flow direction at the Section 8 mine is toward the north-northwest

(Figures 10 and 11).

Under pre-development conditions, the aquifers at the site had similar water level elevations,

with an overall downward direction of groundwater flow between aquifer units as indicated in

Figure 11 (e.g., the simulated hydraulic head in the Dakota Sandstone is higher than that in the

underlying Morrison Formation and Entrada Sandstone).

The effects of the Nutria Monocline east of Gallup on the water levels in the aquifer units are

also evident on Figures 10 and 11. The direction of groundwater flow is to the west across the

monocline, but the hydraulic gradient becomes noticeably steeper, indicating greater resistance

to groundwater flow due to the steep dip of the geologic units.

4.3 Aquifer Hydraulic Properties

The following subsections provide a brief description of hydraulic properties for each of the

aquifer units that occur within the study area. Hydraulic properties are discussed in terms of

hydraulic conductivity and transmissivity. Hydraulic conductivity can be thought of as the

permeability of a given aquifer unit, or the ease with which groundwater can pass through it. A

high hydraulic conductivity indicates that groundwater can flow through the rock material

relatively easily, as would be the case for sandstone. A low hydraulic conductivity indicates that

the material is not very permeable to the flow of groundwater, as is the case with a shale or

mudstone. Hydraulic conductivity has units of length per time, and the units of feet per day (ft/d)

are used in this report. Note that the value of hydraulic conductivity, even though it has units of



ft/d, does not indicate the rate of groundwater movement. The rate at which groundwater flows

through an aquifer is dependent on hydraulic conductivity and other factors that are presented in

detail in Section 6.

In the following subsections, the term transmissivity is also used to describe aquifer properties.

Transmissivity can be thought of as the hydraulic conductivity of a given aquifer unit times the

thickness of the unit, and therefore has units of square feet per day (ft2/d). Sometimes

transmissivity is used as a measure of aquifer production potential rather than hydraulic

conductivity because the aquifer thickness is taken into account. For example, a high-hydraulic

conductivity aquifer that is thin may not produce much water, while a lower-hydraulic

conductivity aquifer that is thick may yield large quantities of water.

4.3.1 Alluvial Aquifer

The alluvial aquifer in the study area occurs within the alluvium of the Puerco River and its

tributaries. The transmissivity of the alluvium varies widely depending on the lithology and

thickness of the fill materials (Stone et al., 1983). Transmissivity values in the Puerco River

valley near Gallup are reported to be about 1,000 ft2/d or less (Stone et al., 1983).

Recharge to alluvial aquifers in the San Juan Basin may occur from precipitation, surface runoff,

recharge from the waterways, return flow from irrigation, and upward leakage from the bedrock

aquifers (Baldwin and Anderholm, 1992). The depth of the water table in the alluvial aquifer

probably varies seasonally due to variable surface flows (which are primarily ephemeral) in the

stream channel and pumping demands for domestic and irrigation supply. The relatively

shallow nature of the alluvial aquifer makes it susceptible to drought conditions. As recharge

diminishes during drought, the water table may lower, causing deeper pumping levels and lower

production, and some wells may go dry.

4.3.2 Major Mesozoic Sandstone Aquifers

The Dakota Sandstone, Gallup Sandstone, and Westwater Canyon Member of the Morrison

Formation each have the potential to be a source of water for municipal, domestic, or livestock



wells. Transmissivity values presented in Table 5 range from single digits up to 930 ft2/d, and

are typical for sandstone aquifers in the Four Corners area.

As noted in Section 2, the Section 8 ISR project will be conducted in the Westwater Canyon

Member of the Morrison Formation. Aquifer properties of the Westwater Canyon aquifer were

calculated based on aquifer tests performed by URI in Section 8 (HRI, 1988).

In 1988 HRI performed an aquifer test on well CR-3 to determine aquifer properties of the

Westwater Canyon aquifer and observe hydrologic connections within the Westwater Canyon

(wells CR-5, CR-6, and CR-8) and other geologic units above and below the Westwater

Canyon, including the Brushy Basin (CR-2) and Recapture Members (well CR-7) of the

Morrison Formation and the Dakota Sandstone (well CR-1). This hydrologic testing report is

included as an appendix (Section C-7) to the New Mexico Environment Department (NMED)

groundwater discharge permit application.

Based on 72 hours of pumping and recovery monitoring, the test results were evaluated to

establish aquifer properties of the Westwater Canyon Member and determine connectivity with

overlying and underlying geologic units. The results of aquifer tests conducted within the

Westwater Canyon aquifer at the Section 8 site (HRI, 1988) indicate transmissivity on the order

of 124 to 177 ft2/d, which corresponds to hydraulic conductivity of about 0.6 to 0.9 ft/d assuming

an aquifer thickness of 200 feet (Table 6). Aquifer test results also indicated that pumping in the

Westwater Canyon Member had no effect on water levels in adjacent units, indicating low

hydraulic conductivity of the confining beds adjacent to the Westwater Canyon aquifer.

4.3.3 Minor Mesozoic Sandstone Aquifers

The sandstones of the Menefee Formation, the Point Lookout Sandstone, and the Dalton

Sandstone Member of the Crevasse Canyon Formation each have the potential to meet the

relatively low demand of domestic or livestock wells. The transmissivity of the units, reported in

Table 5, ranges from 1 to 240 ft2/d. While the Menefee Formation is a common source of water

for stock and domestic uses, the Point Lookout Sandstone is not widely used as a source of

water in the San Juan Basin (Stone et al., 1983). Because the Dalton Sandstone Member of



the Crevasse Canyon Formation has a limited geographic extent, it also is not a major aquifer in

the basin (Kernodle, 1996).

4.3.4 San Rafael Group

The San Rafael Group includes two water-producing units: the Cow Springs-Bluff and Entrada

Sandstones. Wells completed in the Cow Springs-Bluff Sandstone yield sufficient amounts of

water for stock use (0.5 to 20 gpm) (Risser and Lyford, 1983) and have transmissivity values

ranging from 3 to 300 ft2/d in the San Juan Basin (Stone et al., 1983). Entrada Sandstone

yields range from 3 to 200 gpm, with an average of 40 gpm and a median of about 5 gpm

(Risser and Lyford, 1983). Transmissivity of the Entrada Sandstone is reported to range from

50 to 350 ft2/d (Stone et al., 1983).

The Wanakah Formation, which consists of the Summerville Formation and Todilto Limestone,

is considered to be a regional confining unit (Risser and Lyford, 1983). Wells completed in the

Summerville Formation yield little water, and wells completed in the Todilto Formation have both

poor yield (except where fractured) and poor water quality (Risser and Lyford, 1983).

4.3.5 Chinle Group

Where present the Chinle Group acts as a confining unit for the underlying San Andres-Glorieta

aquifer (Baldwin and Anderholm, 1992). The Chinle Group sediments contain thick sequences

of low hydraulic conductivity shale that impedes the movement of groundwater. Recharge to

and discharge from the Chinle Group is mainly from leakage of water through the formation

(Baldwin and Anderholm, 1992). Sandstone members of the Chinle Group may provide limited

water supplies in some areas.

4.3.6 San Andres-Glorieta Aquifer

The contact between the Glorieta Sandstone and San Andres Limestone is gradational, and the

two units are hydraulically connected, forming the San Andres-Glorieta aquifer, the major

aquifer in west-central New Mexico (Baldwin and Anderholm, 1992). Hydraulic conductivity and

transmissivity for the aquifer range widely. Stone et al. (1983) cite transmissivity values ranging



from 5 to 3,700 ft2/d near Fort Wingate, and estimate that a value of 90 ft2/d may be typical for

areas away from outcrops and not subject to dissolution of carbonates (Table 5).

4.4 Groundwater Quality

Water quality data for major ions and dissolved trace elements were compiled for the principal

aquifers near the Section 8 area and southern San Juan Basin; these data are presented in

Tables 7 and 8. For comparison, the tables also include U.S. Environmental Protection Agency

(EPA) primary and secondary drinking water standards. Water quality data for the area were

compiled from several sources by individual aquifer as follows: Dam (1995) for the Gallup

Sandstone, Dakota Sandstone, and the Morrison Formation; Risser and Lyford (1983) for the

Entrada Sandstone and the Chinle Formation; Baldwin and Anderholm (1992) for the San

Andres Limestone and Glorieta Sandstone; and Stone et al. (1983) for the alluvial aquifer.

Water quality is variable in the sandstone aquifers, reflecting the proximity of the sampling point

to the recharge area, leakage between aquifers, and cross-communication in wells that are

screened across multiple aquifers. In general, better quality water would be expected near the

recharge area for each aquifer unit, and water quality generally deteriorates (contains higher

concentrations of dissolved constituents) at distance from the recharge area. This pattern

occurs because, as groundwater moves away from the recharge area, it has been in contact

with the geologic material of the host aquifer for greater periods of time.

The following subsections reference specific conductance and total dissolved solids (TDS)

concentrations as measures of water quality. TDS concentration is a laboratory measurement

of the total amount of dissolved solids that are within a given volume of water; it has units of

milligrams per liter (mg/L). Specific conductance is a measure of the ease with which a given

water sample can conduct an electrical current, and is therefore an indirect measure of TDS

(the greater the amount of dissolved salts in the water, the more readily the sample will conduct

electrical current). Specific conductance is often obtained using field meters, and has units of

microsiemens per centimeter (µS/cm), which is equivalent to the units micromhos per

centimeter (µmhos/cm) used in some older references. If the specific conductance is known,

the equivalent TDS concentration can be approximated as the specific conductance times 0.7.



4.4.1 Alluvial Aquifer

The quality of water in alluvial aquifers is highly variable. Stone et al. (1983) report that the

specific conductance of water from alluvium in the Puerco River east of Gallup generally does

not exceed 1,500 µS/cm.

4.4.2 Point Lookout Sandstone and Menefee Formation of the Mesa Verde Group

The specific conductance of water from the Point Lookout Sandstone, like that of the Menefee

Formation, generally exceeds 1,500 µS/cm (Stone et al., 1983). Fluoride concentrations in the

Menefee Formation exceed recommended limits for drinking water for areas west and south of

the Chaco River (Stone et al., 1983).

4.4.3 Gallup Sandstone Aquifer

Groundwater in the Gallup Sandstone is a calcium-bicarbonate water type near recharge areas,

changing to a sodium-bicarbonate water type downgradient (Dam, 1995). Water quality in the

Gallup Sandstone is variable but is generally acceptable for domestic, livestock, industrial, and

municipal use (Dam, 1995). In some areas the groundwater has elevated sulfate and TDS

concentrations that exceed standards, and fluoride concentrations and pH values exceed

standards in a few samples (Table 7). Trace elements detected at concentrations above

standards include iron and manganese (Table 8).

4.4.4 Dakota Sandstone Aquifer

Groundwater in the Dakota Sandstone is a sodium-bicarbonate water type near recharge areas

with increasing sulfate concentrations downgradient (Dam, 1995). Water quality in the Dakota

Sandstone is variable but is generally acceptable for domestic, livestock, and industrial use

(Dam, 1995). Most Dakota Sandstone wells produce water of acceptable quality, with TDS

concentrations ranging from 800 to 1,100 mg/L (Risser and Lyford, 1983). In some areas the

groundwater has elevated sulfate and TDS concentrations that exceed standards, and fluoride

and chloride concentrations and pH values exceed standards in several samples (Table 7).



Trace elements that were detected at concentrations above standards include iron and

manganese (Table 8).

4.4.5 Morrison Formation and Westwater Canyon Aquifer

The Morrison Formation is the host of uranium mineralization in the area; the top of the

formation is located at a depth of about 600 to 800 feet bgs at the Section 8 proposed ISR site.

Groundwater in the Morrison Formation is a sodium-bicarbonate type water near recharge

areas, changing to a sodium-sulfate water type downgradient (Dam, 1995). Water quality in the

Morrison Formation and Westwater Canyon aquifer is variable, but generally acceptable for

domestic, livestock, and industrial use (Dam, 1995). In some areas the groundwater has

elevated sulfate and TDS concentrations that exceed standards, and fluoride and chloride

concentrations and pH values exceed standards in several samples (Table 7). Trace elements

detected at concentrations above standards include iron and manganese (Table 8). Natural

mineralization in this unit will locally affect water quality; water quality standards for other

constituents may be exceeded in some areas.

4.4.6 San Rafael Group

Water quality in the Entrada Sandstone is generally poor in deep parts of the San Juan Basin,

with TDS concentrations exceeding 10,000 mg/L (Table 7). The quality is better near recharge

areas, but still poor for domestic use, with TDS concentrations near 1,500 mg/L (Stone et al.,

1983). Specific conductance of water from the Cow Springs-Bluff Sandstone in or near

outcrops on the southern and western margins of the basin is probably less than 2,000 µS/cm

(Stone et al., 1983). The limited water quality data at greater depths indicate specific

conductance of groundwater in the Gallup area to be 4,300 µS/cm (Stone et al., 1983).

4.4.7 Chinle Group

The Chinle Group typically yields poor-quality water in the San Juan Basin, except in or very

near outcrop areas (Stone et al., 1983). Locally sandstones of the Chinle Group will produce

water of sufficient quantity and quality for domestic uses such as in the Churchrock area.



4.4.8 San Andres-Glorieta Aquifer

The San Andres Limestone and Glorieta Sandstone form a hydraulically connected aquifer in

the Section 8 area. The water quality in the San Andres-Glorieta aquifer is highly variable in the

San Juan Basin due the composition of the water that recharges the aquifer, the mineralogy of

the aquifer, and the residence time. Specific conductance of San Andres-Glorieta groundwater

in the Thoreau area, east of the area of interest, ranges from 470 to 1,390 µS/cm (Baldwin and

Anderholm, 1992). The dominant cations were found by Baldwin and Anderholm (1992) to be

calcium and magnesium, while bicarbonate and sulfate were determined to be the dominant

anions.



5. Conjunctive Use Well Placement Constraints

The following subsections document the physical and land ownership constraints to the

placement of NGWSP conjunctive use wells in the future.

5.1 Physical Constraints

Figure 12 shows the topography of the area of interest, including the Puerco River Valley and

multiple mesas and canyons. Steep mesa side slopes occur immediately north of the URI

Section 8 site, followed by flatter elevated mesa top surfaces. Wells would not be drilled on the

steep side slopes. The elevated mesa top surfaces may somewhat constrain the placement of

future public supply wells in this area, as the mesa tops are rugged and have limited access.

Mesa top drilling would add unnecessary drilling footage, and new public supply wells may be

better located in the valleys, where the saturated portions of the target aquifers can be more

readily accessed. Furthermore, current conjunctive use wells for the Churchrock Chapter are

targeted for the alluvial aquifers only, which are located south of Section 8 (Figures 4 and 5).

Figure 13 shows the Federal Emergency Management Agency (FEMA) flood hazard areas for

the area of interest. These include (1) a special hazard flood area along the Puerco River,

which is subject to inundation by a 1 percent annual chance flood, (2) an area in the southern

portion of the area of interest that is outside of the 0.2 percent annual chance floodplain, and

(3) an area in the northwest portion of the area of interest that does not include any special flood

hazard area (Figure 13).

The FEMA special hazard flood area that follows the Puerco River falls within the Churchrock,

Iyanbito, and Pinedale Chapters (Figure 1). The area that FEMA has determined is outside of

the 0.2 percent annual chance floodplain includes portions of the Rock Springs, Tsayatoh,

Churchrock, Iyanbito, and Pinedale Chapters (Figure 1). FEMA has not determined the flood

hazards for the northern portion of the area of interest (Figure 13), within the Coyote Canyon

and Nahodishgish (Dalton Pass) Chapters (Figure 1).



As discussed in Section 3.2, the Project FEIS recommends conjunctive groundwater

development in the Churchrock, Coyote Canyon, Iyanbito, Nahodishgish (Dalton Pass), and

Rock Springs Chapters (Table 3) (USBR, 2009). In addition to the chapters discussed in the

FEIS, the more recent Navajo Nation conjunctive groundwater project list also includes the

Pinedale, Tsayatoh, and Twin Lakes Chapters (Table 4) (NNDWR, 2010). Well placement

constraints in these chapters due to flood hazards include:

For the Tsayatoh, Churchrock, Iyanbito, and Pinedale Chapters, new wells should not be

located within the special hazard flood area along the Puerco River.

The flooding potential will need to be accessed in the field when the well sites are being

identified in the Coyote Canyon and Nahodishgish [Dalton Pass] Chapters, as FEMA

has not determined the flood hazards for the northern portion of the area of interest.

No well placement constraints due to flood hazard were identified for the Twin Lakes or

Rock Springs Chapters.

URI had a site-specific surface water drainage analysis conducted as a part of their permit

applications, and used the U.S. Army Corps of Engineers HEC-2 Water Surface Profile

computer model to determine the probable maximum precipitation event water surface

elevations and velocities for the site (Espey, Huston & Associates, 1996). Figure 14 shows the

delineation of the probable maximum precipitation floodplain based on the HEC-2 model

elevation determinations. This floodplain area is located in the center of the area of interest

(Figure 14), within the Churchrock Chapter, and does not include the site of the proposed mine

(Espey, Huston & Associates, 1996). This area should also be avoided when locating any

future wells within the Churchrock Chapter.

5.2 Land Ownership Constraints

The majority of the study area is owned by the Navajo Nation, with a small checkerboard of

state, U.S. Bureau of Land Management (BLM), U.S. Department of Defense (Fort Wingate

Army Depot), and private ownership (Figure 15). Land ownership is not thought to significantly



constrain placement of future NGWSP conjunctive use wells. The conjunctive use wells that are

planned will be located within, and will supply, various Navajo Nation chapters (Section 2.2).

Subsurface ownership for the area of interest is shown on Figure 16. Mineral ownership for the

majority of the study area is non-federal, and likely the Navajo Nation for the region north of

Section 8. Subsurface ownership is not thought to significantly constrain placement of future

NGWSP conjunctive use wells.



6. Assessment of Potential Impacts from Section 8 ISR

This section presents discussion and analysis concerning the potential for NGWSP conjunctive

use wells to be impacted from Section ISR activities. ISR operations are briefly discussed in

Section 6.1 order to lay the foundation for site-specific controls for impacted groundwater that

will be in place during active ISR operations and the subsequent aquifer remediation period.

Section 6.2 evaluates the potential for impacts to conjunctive use wells based primarily on

conservative (faster than expected) time of travel computations based on the summary

information and the hydrogeologic framework provided in previous sections of the report.

6.1 ISR Operations

Uranium mining using ISR methods is described in Section 2. The process involves injection of

barren lixiviant (URI proposes to use native groundwater enriched with oxygen) at injection wells

and extraction of pregnant lixiviant (lixiviant that contains uranium) at extraction wells. The

exact nature of the injection and extraction well layout is not yet known, but it will be configured

based on the characteristics of the ore body and local hydrogeology of the Westwater Canyon

member.

Potential problems may arise if the lixiviant is not fully captured and extracted by the wells, and

adjacent groundwater outside of the ore body becomes impacted. A ring of monitor wells will

surround the injection and extraction well system in order to monitor for this type of situation

(Figures 1 and 2). URI will be required to monitor water levels and water quality at these wells

both during active ISR operations and during post-ISR groundwater remediation. These data

are evaluated in order to detect potential excursions of lixiviant and alert the operator so that

corrective actions can be taken to reestablish complete capture of lixiviant and impacted

groundwater.

After mining ceases, URI has proposed to conduct aquifer restoration through continued

circulation of the groundwater without the addition of lixiviant. The groundwater is remediated

using RO (Section 2). During this step, residual uranium will still be actively removed from the

groundwater if it exists at sufficient concentration, facilitating the restoration efforts. Use of



oxygen-enriched groundwater will greatly facilitate groundwater cleanup efforts as compared to

outdated approaches that relied on the addition of large quantities of chemical additives to the

lixiviant. Groundwater quality improves significantly during the groundwater sweep process

(Davis and Curtis, 2007), although complete restoration to all numerical baseline values has

been problematic at some sites (Hall, 2009). URI is required to demonstrate that restoration

goals have been met at the site.

Impacts to groundwater would be the result of the interaction of the ore with lixiviant. Uranium,

selenium, vanadium, arsenic, and sulfur may form soluble oxyanions that typically remain in

solution while the aquifer remains under oxidizing conditions. If an excursion (failure to capture

lixiviant) were to occur, increased chloride and sulfate concentrations, followed by increased

concentrations of other metal anions, would be detected at monitor wells. Observed water

levels at the monitor wells would also assist in the identification of an excursion. If an excursion

occurs, URI will be required to take action to eliminate it. For example, the rate of groundwater

pumping could be increased, or the distribution of injection and pumping within the well field

could be adjusted to eliminate the excursion.

6.2 Potential for Impacts from Section 8 ISR

If impacted groundwater from ISR activities were to somehow move undetected past the ring of

monitor wells in place at the site during operations, the impacted water would migrate in

accordance with the natural hydraulic gradient that exists in the vicinity of the site, which is

north-northwest. In such a case, the concentrations of various constituents would be diminished

by natural attenuation, which includes dilution (mixing with non-impacted water), and

geochemical reactions within the aquifer that would reduce solute concentrations.

In order to assess the potential risk that a hypothetical excursion could pose to NGWSP

conjunctive use wells, groundwater travel times were estimated based on the hydraulic

properties and other hydrogeologic information compiled for the Westwater Canyon Member of

the Morrison Formation within the study area. Time of travel was calculated based on the

following equation:

TOT = K i / n



where TOT = average travel time (years)

K = hydraulic conductivity (feet per year [ft/yr])

i = hydraulic gradient (feet per foot [ft/ft])

n = effective porosity (unitless)

Note that this equation does not account for geochemical processes within the groundwater

system that tend to substantially reduce the rate of migration of uranium and other metals.

The average hydraulic gradient in the Section 8 area based on Figure 10 is about 0.008 ft/ft,

and a reasonable effective porosity for the Westwater Canyon Member would be between 0.15

and 0.25. Using a hydraulic conductivity of 1 ft/d, a hydraulic gradient of 0.008, and an effective

porosity of 0.15, the estimated time of travel for a contaminant in the Section 8 area is 0.05 ft/d,

or about 20 ft/yr. Note that this would be a maximum expected value; if a hydraulic conductivity

of 0.8 ft/d is applied (Table 6) in conjunction with an effective porosity of 0.25, the calculated

time of travel in the Westwater Canyon Member would be about 9 ft/yr.

Aquifer properties taken from the regional groundwater flow model of Kernodle (1996) were also

used to calculate estimated travel times in the sandstones of the Morrison Formation. The

USGS provides transmissivity data for the Morrison Formation ranging from 2 to 480 ft2/d with a

median value of 115 ft2/d (Kernodle, 1996). Values from the on-site tests fall within the range

presented by the USGS and also near median values. Using the highest aquifer transmissivity

value of 480 ft2/d and an aquifer thickness of 200 feet, the corresponding hydraulic conductivity

would be 2.4 ft/d (i.e., 480 ft2/d divided by 200 ft is 2.4 ft/d). Using a hydraulic conductivity of

2.4 ft/d and an effective porosity of 0.15, the estimated time of travel would be 47 ft/yr.

Based on the estimated travel times calculated above, impacted water from the URI Section 8

mine site would take at least 100 years to travel 1 mile; in all likelihood the time of travel would

be much greater. As indicated in Figure 3, the nearest downgradient well (north and west of

Section 8), Navajo Nation livestock well 14K-313, is about 3 miles from the proposed mine site.

In addition, this well is not completed in the Morrison Formation sandstones, but is likely

completed in either the overlying Crevasse Canyon Formation of the Mesa Verde Group

(Figure 5) or the Gallup Sandstone (Table 2). Regardless, this well obtains water from a

sandstone aquifer that is separated from the Westwater Canyon Member by the Mancos Shale



and other low-permeability geologic units. It would take groundwater from the Section 8 area

more than 300 years to reach this well, not accounting for the fact that water would have to

move vertically upward through hundreds of feet of low-permeability materials to reach the well

screen.

As outlined in Section 3, exact locations for the NGWSP conjunctive use wells are not known. A

summary of current plans, based on NNDWR (2010), is provided in Table 4 and Figure 4. As

indicated in Figure 4, Westwater Canyon aquifer wells (the same aquifer as the proposed ISR

project) are identified for the Navajo Nation Twin Lakes Chapter. In addition, although wells are

not specifically identified for the Nahodishgish/Dalton Pass Chapter, the Westwater Canyon

aquifer is identified as the target aquifer should wells be completed in that area. Based on this

information, the closest possible Westwater Canyon aquifer well to Section 8 would be

approximately 3.6 miles from the Section 8 ISR site, assuming that a well were constructed at

the far southwestern corner of Nahodishgish/Dalton Pass Chapter. Based on the fastest travel

time provided above, the shortest time of travel from the Section 8 ISR project to the closest

corner of the Nahodishgish/Dalton Pass Chapter would be slightly more than 400 years.

Furthermore, based on Figures 10 and 11, groundwater from Section 8 is unlikely to travel to

the Nahodishgish/Dalton Pass Chapter at all; it is more likely to travel to the Twin Lakes

Chapter, the closest point of which is about 5.2 miles from Section 8 (Figure 4), which would be

time of travel of nearly 600 years based on the fastest calculated groundwater flow velocity.

The Coyote Canyon Chapter is also downgradient (north) of Section 8. Conjunctive use wells

for this chapter are identified for aquifers of the Mesa Verde Group sediments, the deepest of

which is the Gallup Sandstone (Figure 6). If water from Section 8 were to impact these wells, it

would need to travel more than 2 miles north and at the same time migrate vertically upward

from the Westwater Canyon aquifer, pass through the Dakota Sandstone aquifer and the

Mancos Shale confining unit, and ultimately reach the Gallup Sandstone aquifer. This is a

highly implausible scenario.

Other chapters of interest where conjunctive use wells could be placed include the Churchrock

Chapter (in which Section 8 is located), the Rock Springs Chapter to the west of Section 8, and

the Iyanbito Chapter to the southeast of Section 8. The Iyanbito Chapter is hydrologically

upgradient of Section 8, and groundwater from Section 8 will not flow to this chapter.



Conjunctive use wells for the Churchrock Chapter are identified for the alluvial aquifer, which

would be south of Section 8 (Figure 5), also hydrologically upgradient. The majority of the Rock

Springs Chapter is crossgradient from Section 8, and groundwater is more likely to flow to the

north than to the west-northwest toward this chapter (Figure 10). Even if groundwater from

Section 8 did flow toward the Rock Springs Chapter, it is farther away than the Twin Lakes

Chapter discussed earlier, and conjunctive use wells would be shallower in the geologic profile

than the Westwater Canyon aquifer, similar to the situation described for the Coyote Canyon

Chapter to the north.



7. Summary and Conclusions

The potential impacts to water supply in the vicinity of the Section 8 ISR project are expected to

be minimal outside the proposed monitor well ring (Figure 1). During operations, lixiviant will be

injected and extracted in such a way as to contain the groundwater impacted by the ISR

operation. The effectiveness of the operation will be monitored using a ring of monitor wells that

will surround the ore body in the Westwater Canyon aquifer; monitor wells will also be

completed in the overlying and underlying geologic units. Once ISR is complete, aquifer

restoration will be conducted using continued groundwater pumping and injection combined with

an RO method to reduce constituent concentrations in the water. URI will be required to meet

water quality goals defined in their permits before restoration is considered complete.

As distance from the Section 8 mine increases, the potential threat of impacts to groundwater

supplies decreases dramatically. Groundwater in the Westwater Canyon aquifer migrates at a

rate of about 9 to 20 ft/yr, although a conservative estimate of travel time (faster than expected)

of 47 ft/yr was used for the impact analysis. The direction of groundwater flow in the Section 8

area is predominantly to the north-northwest. Leakage of Westwater Canyon aquifer water

upward or downward to adjacent aquifer units can occur across low-hydraulic conductivity

confining units, but the amount of such leakage is small compared to the magnitude of

groundwater flow that occurs within the aquifer unit itself.

Existing City of Gallup wells are located over 10 miles from Section 8, and the proposed

locations of five of the City’s G-22 wells are along the southwest perimeter of the 10-mile radius

of interest to the east of Gallup. The City’s existing wells are located to the west of the Nutria

monocline, which limits groundwater flow to the west. In addition, groundwater flows to the

north/northwest from Section 8, away from the City. The proposed G-22 wells would be

approximately 4,000 feet deep and would be located upgradient of Section 8. Based on the

groundwater flow direction, well depths, and other factors documented in this report, Section 8

ISR activities will have no effects on existing or future (G-22) City of Gallup wells, either during

mining or at any time after mining ceases.

Existing Navajo Nation wells are located throughout the region within the 10-mile radius of the

Section 8 study area. The wells are completed in multiple aquifer units, including the Westwater



Canyon Member of the Morrison Formation. Wells that are completed in overlying aquifers are

protected from impacted water that could result from interaquifer leakage due to the presence of

shale and clay units that typically separate aquifers in the San Juan Basin. The relatively slow

travel time of groundwater in the Morrison Formation and other aquifers also acts to protect

existing supply wells. Vertical travel times through shale and clay units would be significantly

slower compared to the travel times within the sandstone aquifers. The concentrations of metal

constituents in groundwater will also be reduced due to geochemical processes, particularly as

the groundwater flows through shale and clay units.

Two existing Navajo Nation wells (16T-513 and 16T-534) are reported to be completed in the

Morrison Formation, which includes the Westwater Canyon Member (Table 2 and Figure 3).

Both wells 16T-513 and 16T-534 are domestic wells located upgradient of Section 8 in

southeast and southwest directions, respectively. The wells are closer to the recharge area

where the Morrison Formation is at the land surface, and groundwater will not flow from

Section 8 toward these wells. Two livestock wells immediately south of Section 8—16T-532

(listed as inactive in the NNDWR database) and 16T-606—may be completed in the Morrison

Formation, but these wells are also upgradient (south) of the proposed ISR operation.

Wells located at Fort Wingate and Rehoboth will not be impacted by Section 8 ISR activities.

The Morrison Formation is generally eroded in this area, so there is no direct connection to the

Westwater Canyon aquifer unit that would be the target of ISR in Section 8. These sites are

also located several miles upgradient of the mine site, eliminating the potential for impacts from

contaminated groundwater.

The primary purpose of this project was to assess the risk for future contamination from proposed

Section 8 ISR activities on groundwater supply to be developed and conjunctively used as part of

the Gallup regional water system component of the NGWSP. Based on the existing information

and analysis compiled in this report, including conservative estimates of groundwater flow rates

(faster than expected) and future conjunctive use well locations (closer to Section 8 than they will

likely be), there is no discernible risk that ISR activities conducted in Section 8 will adversely affect

future NGWSP conjunctive use groundwater supplies.



References

Allgood, L. 2012. Personal communication between Lance Allgood, Gallup Joint Utilities

Executive Director, and Amy Ewing, DBS&A. October 19, 2012.

Anderson, O.J., S.G. Lucas, and C.H. Maxwell. 2003. Geologic map of the Fort Wingate

quadrangle. Geologic Quadrangle Map, Open-File Report. New Mexico Bureau of Mines

and Mineral Resources.

Baldwin, J.A. and S.K. Anderholm. 1992. Hydrogeology and ground-water chemistry of the San

Andres-Glorieta Aquifer in the Acoma Embayment and Eastern Zuni Uplift, west-central New

Mexico. U.S. Geological Survey (USGS) Water-Resources Investigations Report 91-4033.

304 p.

Cooley, M.E., J.W. Harshbarger, J.P. Akers, and W.F. Hardt. 1969. Regional hydrogeology of

the Navajo and Hopi Indian Reservations, Arizona, New Mexico, and Utah. USGS

Professional Paper 521-A. 61 p.

Dam, W.L. 1995. Geochemistry of ground water in the Gallup, Dakota, and Morrison aquifers,

San Juan Basin, New Mexico. USGS Water-Resources Investigations Report 94-4253.

Dam, W.L., J.M. Kernodle, G.W. Levings, and S.D. Craig. 1990. Hydrogeology of the Morrison

Formation in the San Juan structural basin, New Mexico, Colorado, Arizona, and Utah.

USGS Hydrologic Atlas 720-J.

Davis, J.A. and G.P. Curtis. 2007. Consideration of geochemical issues in groundwater

restoration at uranium in-situ leach mining facilities. U.S. Nuclear Regulatory Commission

Office of Nuclear Regulatory Research. January 2007. NUREG/CR-6870.

Espey, Huston & Associates, Inc. 1996. Supplement to surface water analysis for proposed

HRI, Inc. Churchrock in-situ uranium leach project, McKinley County, New Mexico.

September 1996.




Foley, M. 2012. Personal communication between Michael Foley, Principal Hydrologist, Navajo

Nation Water Management Branch, and Amy Ewing, DBS&A. July 2 and 26, 2012.

Hall, S. 2009. Groundwater restoration at uranium in-situ recovery mines, South Texas Coastal

Plain. USGS Open-File Report 2009-1143.

HRI Inc. 1998. Hydrological testing report, Churchrock Project. December 1, 1988.

Kernodle, J.M. 1996. Hydrogeology and steady-state simulation of ground-water flow in the San

Juan Basin, New Mexico, Colorado, Arizona, and Utah. USGS Water-Resources

Investigations Report 95-4187. 117 p.

Navajo Nation Department of Water Resources (NNDWR). 2010. Conjunctive groundwater

development plan. Navajo-Gallup Water Supply Project, Navajo Nation Department of Water

Resources, Water Management Branch. March 30, 2010.

New Mexico Office of the State Engineer (NM OSE). 2012. WATERS database. Available at

<http://www.ose.state.nm.us/waters_db_index.html>.

Risser, D.W. and F.P. Lyford. 1983. Water resources on the Pueblo of Laguna, west-central

New Mexico. Prepared in cooperation with the U.S. Bureau of Indian Affairs. USGS Water-

Resources Investigations Report 83-4038.

Stone, W.J., F.P. Lyford, P.F. Frenzel, N.H. Mizell, and E.T. Padgett. 1983. Hydrogeology and

water resources of San Juan Basin, New Mexico. New Mexico Bureau of Mines and Mineral

Resources Hydrologic Report 6. 70 p.

Thompson, E. 2012. Personal communication between Ernest Thompson, GJU Water and

Wastewater Superintendent, and Amy Ewing, DBS&A. June 1, 2012.

U.S. Department of the Interior Bureau of Reclamation (USBR). 2009. Planning report and final

environmental impact statement. Navajo-Gallup Water Supply Project, U.S. Department of

the Interior, Bureau of Reclamation, Upper Colorado Region. July 2009.

Figures

40

491

566

400

602

264

WingateIyanbito

Fort Wingate

Mexican Springs

Rehoboth Church Rock

COYOTE CANYON

TWIN LAKES

PINEDALECHURCHROCK

IYANBITO

ROCK SPRINGS

RED ROCK #16

NAHODISHGISH/D PASS

TOHATCHI

STANDING ROCK

TSAYATOH

THOREAU

MEXICAN SPRINGS

BREADSPRINGS

MARIANOLAKE

Pinedale

Twin Lakes

Coyote Canyon

GallupGallup

Puerco River

Dye Brush

Was

h

Burne

d De

ath

Was

h

Bread Springs Wash

Pinetree

Can

yon

N0 2 4

Miles

S:\PROJECTS\WR12.0085_URI_SECTION_8_GROUNDWATER_STUDY\GIS\MXDS\FINAL_REPORT_10-2012\FIG01_STUDY_AREA.MXD 122410

Figure 1

JN WR12.008510/24/2012Daniel B. Stephens & Associates, Inc.

URI SECTION 8 GROUNDWATER STUDYStudy Area

Explanation

Ore bodyProposed monitor well ring10-mile radius

Navajo chapterCity/community

0 750 1500Feet

Conceptual Diagram of ISR ProcessURI SECTION 8 GROUNDWATER STUDY

Daniel B. Stephens & Associates, Inc.10-28-12 JN WR12.0085

Fig

ure

2

Source: Modified image provided by URI

Note: Diagram is for simplified conceptual illustration only

A

B

C

Explanation

Water table surface forunconfined Aquifer B

S:\PROJECTS\WR12.0085_URI_SECTION_8_GROUNDWATER_STUDY\VR_DRAWINGS_FIG02_CONCEPT_DIAGRAM_ISR_PROCESS.CDR

DRAFT

Recapture Member (shale) - confining unit

Westwater Canyon Sandstone

Monitor wells(safeguard system)

Injection well

Extraction well Extraction well

Brushy BasinMember (bentonite)

- confining unit

Uranium bearingresin to plantfor processing

Uranium in solutionUranium in solution

O CO3 2

Uranium ore body

Ion exhangecolumn

(water softener)

Not to scale

40

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400

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264

14A-79

16T-612

16T-532

14T-592

14T-579

14T-573

14T-572

14T-571

14T-56514T-563

14T-553

14T-552

14T-551

14T-54614T-545

14T-542

14T-540

16-066816-0666

14T-584

14T-559

14T-555

14T-524

14T-324

14T-321

14T-538

16T-606

16T-60316T-602

16T-560

16T-537

16T-535

16T-534

16T-51316T-510

16K-340

15T-30314T-586

14T-510

14K-313

16T-538E16T-538B

WGT ORDN 2

14T-566

14T-564

16T-538A

16T-538UNC

Well#17

Well#16Well#15

Well#13

Well#12Well#11

Ray Well

Pena Well

Munoz Well

Erwin Well

Allan Well

Galanis Well

Junker 1 Well

Colaianni Well

Well#10

Lewis WellJunker 2 Well

WingateIyanbito

Fort Wingate

Mexican Springs

RehobothChurch Rock

Fort Wingate Army Depot

Rehoboth Christian School

Cibola National Forest

Pinedale

Twin Lakes

Coyote Canyon

GallupGallup

Puerco River

Dye Brus

h Wash

Bread Springs Wash

Pinetree

Can

yon

Burn

ed D

eath

Was

h

N

Explanation(owner and aquifer of completion)Navajo Nation well

Aquifer unknownSan Andres Limestone/Glorieta SandstoneChinle GroupSan Rafael GroupWestwater Canyon Member of Morrison Frm.Gallup SandstoneDakota SandstoneMesa Verde GroupQuaternary alluvium

City of Gallup wellWestwater Canyon Member of Morrison Frm.Dakota WestwaterDakota/Westwater/Gallup SandstoneGallup Sandstone

Other wellAquifer unknownSan Andres Limestone/Glorieta Sandstone

10-mile radiusNavajo reservation and trust landsCity/community

0 2 4Miles

S:\PROJECTS\WR12.0085_URI_SECTION_8_GROUNDWATER_STUDY\GIS\MXDS\FINAL_REPORT_10-2012\FIG03_WELL_LOCATIONS.MXD 122810

Figure 3


URI SECTION 8 GROUNDWATER STUDYExisting Well Locations

5.2 miles3.6 miles

40

491

566

400

602

264

Wingate

Iyanbito

Fort Wingate

Mexican Springs

Rehoboth

Church Rock

COYOTE CANYONMesa Verde Group

8 wells, TD = 2600 ft

TWIN LAKESWestwater Canyon1 well, TD = 3500 ft

PINEDALE(No projects planned)

CHURCHROCKAlluvial


IYANBITOSan Andres/Glorieta2 wells, TD = 1500 ft

ROCK SPRINGSGallup Sandstone


RED ROCK #16

NAHODISHGISH/D PASSWestwater Canyon

Number of wells is unclearTD = 2600 ft

TOHATCHI STANDING ROCK

TSAYATOH

THOREAU

MARIANOLAKE

MEXICAN SPRINGS

BREADSPRINGS

Pinedale

Twin Lakes

Coyote Canyon

GallupGallup

Puerco Rive r

Dye Brush

Was

h

Burne

d De

ath

Was

h

Bread Springs Wash

Pinetree

Can

yon

N

ExplanationChapterChapter that has potentialWestwater Member wellswithin 10 miles of Section 810-mile radiusCity/communityNGWSP pipeline alignment

0 2 4Miles

TD = Total estimated depth

S:\PROJECTS\WR12.0085_URI_SECTION_8_GROUNDWATER_STUDY\GIS\MXDS\FINAL_REPORT_10-2012\FIG04_NAVAJO_CHAPTERS_FUTURE_WELLS.MXD 122810

Figure 4


URI SECTION 8 GROUNDWATER STUDYNavajo Chapters Where Future

Conjunctive Use Wells Could Be Constructed

Chapter nameInformation from NNDWR (2010)

A’

A

B

B’

Figure 5Daniel B. Stephens & Associates, Inc.10/28/2012 JN WR12.0085

0 1.5 3 Miles

Explanation

10-mile radius

Cross section line

N

S:\P

RO

JEC

TS\W

R12

.008

5_U

RI_

SE

CTI

ON

_8_G

RO

UN

DW

ATE

R_S

TUD

Y\G

IS\M

XD

S\F

INA

L_R

EP

OR

T_10

-201

2\FI

G05

_CR

OS

S_S

EC

TIO

N_L

INE

S_S

UR

FAC

E_G

EO

LOG

Y.M

XD

122

810

URI SECTION 8 GROUNDWATER STUDYSurface Geology Map

Source: Regional hydrogeology of the Navajo and HopiIndian Reservations, Arizona, New Mexico, and Utah witha section on vegetation (Cooley, M.E., et al, 1969).

Chinle Group

Quaternary alluvium

Wingate Sandstone

Mancos Shale

Morrison Formation

Dakota Sandstone

San Rafael Group

Gallup Sandstone

Crevasse Canyon Formation(Mesa Verde Group)

Point Lookout Sandstone(Mesa Verde Group)

Menefee Formation(Mesa Verde Group)

S:\

PR

OJE

CT

S\W

R1

2.0

08

5_U

RI_

SE

CT

ION

_8_G

RO

UN

DW

AT

ER

_ST

UD

Y\V

R_D

RA

WIN

GS

\FIG

08

_3D

_BLO

CK

_DIA

GR

AM

.CD

R

Geologic Block Diagram Showing Cross Sections A-A’ and B-B’

URI SECTION 8 GROUNDWATER STUDY


San Andres Limestone

Glorieta Sandstone

Permian

Well

Well screen

Explanation

Figure 8

DRAFT

Qal

Mancos Shale

Chinle Group (locally includes Moenkopi Formation)

Wingate Sandstone

TriassicT cR

Quaternary alluviumCretaceous

Dakota Sandstone

San Rafael Group (locally includes Entrada Sandstone, Cow Springs,Bluff Sandstone, Todilto Limestone, and Summerville Formation)

Morrison Formation (locally includes Recapture Member, Brushy Basin Member,and Westwater Canyon Member)

Kd

KmJsr

Jm

T wR

Jurassic

Point Lookout SandstoneKpl

Crevasse Canyon FormationKc

Gallup SandstoneKg

Mes

aV

erd

eG

rou

p

Quaternary

Pg

Psa

Conceptual Diagram of a Layered Aquifer SystemURI SECTION 8 GROUNDWATER STUDY


Fig

ure

9

Confined aquifer - permeable rock, sand, and sandstone

Unconfined aquifer - permeable rock, sand, and sandstone

Confining unit - lower permeability rock such as shale

Primary direction of groundwater flow

A

B

C

Explanation

Confined aquiferrecharge area

Potentiometric surface for confinedAquifer A under pressure

Water table surface forunconfined Aquifer B

Upward seepage acrossconfining unit

CA

BC

S:\PROJECTS\WR12.0085_URI_SECTION_8_GROUNDWATER_STUDY\VR_DRAWINGS_FIG09_CONCEPT_LAYERED_AQUIFER_SYS.CDR

DRAFT

40

491

566

32

400

602

264

602

WingateIyanbito

Fort Wingate

Mexican Springs

RehobothChurch Rock

Fort Wingate Army Depot

Rehoboth Christian School

6400

65006600

6300

6700

6300

Cibola National Forest

Cibola National ForestCibola National Forest

Pinedale

Twin Lakes

Coyote Canyon

GallupGallup

Fort DefianceFort Defiance

Puerco River

Chaco Wash

Fajada Wash

Indian Creek

Mitchell D raw

Voght Draw

Coyote

Was

h

Dye B

rush W

ash

Rio Nutria

Red Willow Wash

Manuelito Canyon

Standing Rock Wash

San Mateo Creek

San

Miguel Cre

ek

Canada Marcelina

Bread Springs Wash

Kim-me-ni-oli Valley

Cottonwood Creek

Kim Klizhin W

ash

Burne

d Dea

th W

ash

Seven Lakes Wash

Sand Springs Arro

yo

Navajo Nation wellCity of Gallup wellOther wellSection 8 Site with 10 mile radius

McKinley County boundaryPotentiometric contour for Morrison Fm. (dashed where inferred) (ft msl)Navajo Reservation and trust landsCity/community

S:\PROJECTS\WR12.0085_URI_SECTION_8_GROUNDWATER_STUDY\GIS\MXDS\FINAL_REPORT_10-2012\FIG10_OBSER_MORRISON_FRM_WL_AND_GW_FLOW.MXD 122810

Figure 10


URI SECTION 8 GROUNDWATER STUDYObserved Morrison Formation Water Levels and Groundwater

Flow Direction in the Southern San Juan Basin, New MexicoSource: Dam and others, 1990, Hydrologic Atlas 720-J

Morrison Formation outcrop

Water well (upper number is altitude ofpotentiometric surface (ft msl);lower number is year of measurement

Groundwater flow direction

Explanation

N0 4.5 9

Miles

40

491

566

32

400

602

264

Crownpoint CDP

Tohatchi CDP

Mexican Springs CDP

6800

7000

6600

7200

7400

7000

6800

6800

7000

7200

7200

6800

7000

6600

7200

7400

76007800

6800

7400

6800

7000

7200

7000

6800

7000

6600

7200

7400

7400

7200

6800

6800

7000

Cibola National ForestCibola National Forest

Pinedale

Twin Lakes

Coyote Canyon

GallupGallup

Puerco River

Indian Creek Chaco Wash

Fajada Wash

Coyote W

ash

Voght Draw

Dye B

rush W

ash

Red Willow Wash

Standing Roc k Wash

Kim

-me-ni-oli Valley

Kim Klizhin Wash

Canada Marcelin a

Bread Springs Wash

San Miguel C

reek

Seven Lakes Wash

Can

ada

Alem

ita

Pinetree Canyon

Sand Springs Arroyo

North Fork Arroyo Chico

S:\PROJECTS\WR12.0085_URI_SECTION_8_GROUNDWATER_STUDY\GIS\MXDS\FINAL_REPORT_10-2012\FIG11_SIM_PREDEV_WL_AQUIFERS_NEAR_SEC8.MXD 122810

Figure 11


URI SECTION 8 GROUNDWATER STUDYSimulated Pre-Development Water Levels for

Aquifers Near the Section 8 SiteNote: See Figure 2 for well identifications.

Source: Kernodle, 1996

ExplanationSimulated water levels (ft msl)

Dakota SandstoneMorrison FormationEntrada SandstoneMonocline

Formation outcropDakota SandstoneMorrison FormationEntrada Sandstone

Navajo Nation wellCity of Gallup wellOther wellSection 8 site with 10-mile radius

McKinley County boundaryNavajo Reservation and trust landsCity/community

N0 4 8

Miles

40

491

566

400

602

264Ram Mesa

MesaButte

Big RockHill

UmbrellaButte

CoalMine Hill

WhiteRockMesa

White Rock Canyon

Bla

ck M

esa

Can

yon

SheepSpring Hill

Har

d Gro

und C

anyon

Wild B

erry

Can

yon

Fallen Timber Ridge

WingateRehoboth

Iyanbito

Church Rock

Fort Wingate

Mexican Springs

Pinedale

Twin Lakes

Coyote Canyon

6500

7000

7500

6000

8000

7500

7500

6500

6500

7500

7500

7500

75007000

7000

6500

7500

6500

8000

75007000

GallupGallup

Puerco River

Dye Brush W

ash

Bread Springs Wash

Pinetree

Can

yon

Burn

ed D

eath

Was

h

N

Explanation10-mile radiusLand surface elevationcontour (ft msl)

0 2 4Miles

S:\PROJECTS\WR12.0085_URI_SECTION_8_GROUNDWATER_STUDY\GIS\MXDS\FINAL_REPORT_10-2012\FIG12_TOPOGRAPHY.MXD 122810

Figure 12


URI SECTION 8 GROUNDWATER STUDYTopography

40

491

566

400

602

264

Pue

rco

Rive

r

Dye B

rush W

ash

Burne

d De

ath

Was

h

Bread Springs Wash

Pinetree C

anyo

n

Wingate

Rehoboth

Iyanbito

Church Rock

Fort Wingate

Mexican Springs

Pinedale

Twin Lakes

Coyote Canyon

GallupGallup

N0 2 4

Miles

S:\PROJECTS\WR12.0085_URI_SECTION_8_GROUNDWATER_STUDY\GIS\MXDS\FINAL_REPORT_10-2012\FIG13_FEMA_FLOOD_HAZARD_AREAS.MXD 122810

Figure 13


URI SECTION 8 GROUNDWATER STUDYFEMA Flood Hazard AreasSource: FEMA Flood Insurance Rate Map (FIRM) panels.

ExplanationCity/community10-mile radius

Flood hazard area

Panel not printed - no special flood hazard area

X - Areas determined to be outside the 0.2% annual chance floodplain

D - Areas in which flood hazards are undetermined, but possible

A - Special flood hazard area (SFHA) subject to inundation by the 1% annual chance flood

X - Areas of 0.2% annual chance flood, areas of 1% annual chance flood with average depths of less than 1 foot or with drainage areas less than 1 square mile, and areas protected by levees from 1% annual chance flood

N0 1500 3000

Feet

S:\PROJECTS\WR12.0085_URI_SECTION_8_GROUNDWATER_STUDY\GIS\MXDS\FINAL_REPORT_10-2012\FIG14_CHURCHROCK_FLOODPLAIN.MXD 122810

Figure 14


URI SECTION 8 GROUNDWATER STUDYProbable Maximum Flood FloodplainSource: Church Rock Project, PMF Floodplain Map (EH&A, 1996)

ExplanationCenter of 10-mile radius10-mile radiusProbable maximumflood (PMF) floodplain

Maparea

40

491

566

400

602

264

Wingate

Rehoboth

Iyanbito

Church Rock

Fort Wingate

Mexican Springs

Pinedale

Twin Lakes

Coyote Canyon

GallupGallup

Puerco River

Dye Brush

Was

h

Burne

d De

ath

Was

h

Bread Springs Wash

Pinetree

Can

yon

N

ExplanationCity/community10-mile radius

OwnershipBureau of Land ManagementDepartment of DefenseForest ServicePrivateStateTribal

0 2 4Miles

Source: Bureau of Land Management - New Mexico State Office, 2011

S:\PROJECTS\WR12.0085_URI_SECTION_8_GROUNDWATER_STUDY\GIS\MXDS\FINAL_REPORT_10-2012\FIG15_SURFACE_LAND_OWNERSHIP.MXD 122810

Figure 15


URI SECTION 8 GROUNDWATER STUDYSurface Ownership

40

491

566

400

602

264

Wingate

Rehoboth

Iyanbito

Church Rock

Fort Wingate

Mexican Springs

Pinedale

Twin Lakes

Coyote Canyon

GallupGallup

Puerco River

Dye Brush

Was

h

Burne

d De

ath

Was

h

Bread Springs Wash

Pinetree

Can

yon

N0 2 4

Miles

Source: Bureau of Land Management - New Mexico State Office, 2012

S:\PROJECTS\WR12.0085_URI_SECTION_8_GROUNDWATER_STUDY\GIS\MXDS\FINAL_REPORT_10-2012\FIG16_SUBSURFACE_LAND_OWNERSHIP.MXD 122810

Figure 16


URI SECTION 8 GROUNDWATER STUDYSubsurface Ownership

ExplanationFederal mineral (subsurface) ownership

All minerals owned by the U.S.No minerals are owned by the U.S.Only coal is owned by the U.S.Only oil and gas are owned by the U.S.Only oil, gas, and coal are owned by the U.S.City/community10-mile radius

Tables

Table 1. City of Gallup Existing Well Information

Page 1 of 3

Source: Thompson, 2012 OSE = Office of the State Engineer bgs = Below ground surface

P:\_WR12-085\Sec8-GW Study.O-12\T01_GallupWellInfo.doc


Well OSE File No. Latitude Longitude Depth

(feet bgs)

Screened Interval(s) (feet bgs) Aquifer Completion Comments

Well#10 G-96-S-11, G-97-S-6

35.52235 –108.76369 2,398 930–1,280 1,930–2,400

Dakota Westwater/ Gallup Sandstone

12-inch casing to 1,300 feet, 8-inch casing from 1,300 to 2,398 feet. Screen information is estimated as this well was originally a Santa Fe Railroad well.

Well#11 G-96-S-12, G-97-S-7

35.52098 –108.76833 2,305 946–1,300 1,935–2,305


12-inch casing to 1,300 feet, 8-inch casing from 1,300 to 2,305 feet. Screen information is estimated as this well was originally a Santa Fe Railroad well.

Well#12 G-96-S-13 35.51842 –108.77715 1,600 743–970 991–1,600

Gallup Sandstone 14-inch casing with liner. Liner perforation intervals based on video observation are 556 to 600 feet, 641 to 683 feet, and 725 to 1,311 feet. Debris at 1,311 feet.

Well#13 G-96-S-2 35.53446 –108.70745 260 — Gallup Sandstone 10-inch casing to 207 feet, no perforations, open borehole from 207 to 260 feet.

Well#15 G-96-S-15 35.54461 –108.75987 1,610 828–1,152 1,152–1,538

Gallup Sandstone 18-inch-inner diameter casing.

Well#16 G-96-S-16 35.55189 –108.75986 1,760 ?–1,760 Gallup Sandstone 16-inch casing. Screen information is estimated as this well was originally a Santa Fe Railroad well.


Page 2 of 3





(feet bgs)


Well#17 G-96-S-7, G-97-S-4

35.52643 –108.76192 2,320 960–1,000 1,030–1,070 1,090–1,130 1,170–1,330 1,980–2,200


10¾-inch casing.

Allan Well G-97-S-9 35.65381 –108.78262 3,511 3,004–3,089 3,168–3,336 3,448–3,470

Dakota Westwater 13⅜-inch casing to 2,900 feet, 7-inch casing from 2,900 feet to total depth.

Colaianni Well G-96-S-22 35.59435 –108.77657 2,230 1,583–1,628 1,665–1,710 1,746–1,879 1,917–2,048

Gallup Sandstone 16-inch casing to 1,502 feet, 10¾-inch casing from 1,502 feet to total depth.

Erwin Well G-96-S-18 35.62336 –108.79295 2,100 1,168–1,188 1,222–1,232 1,278–1,300 1,358–2,045

Gallup Sandstone 18-inch casing to 1,100 feet, 10¾-inch casing from 1,100 feet to total depth.

Galanis Well G-96-S-21 35.60907 –108.77421 2,104 1,503–1,543 1,624–1,664 1,684–1,744 1,764–1,804 1,824–1,984

Gallup Sandstone 10¾-inch casing.

Junker 1 Well SJ-113 35.65387 –108.76641 2,100 1,116–2,020 Gallup Sandstone/ San Juan Basin

16-inch casing to 1,116 feet, 8⅝-inch casing from 1,116 to 2,100 feet.

Junker 2 Well G-96-S-20 35.63734 –108.77611 2,174 1,234–1,315 1,486–2,134

Gallup Sandstone 16-inch casing to 1,214 feet, 8⅝-inch casing from 1,214 to 2,174 feet.


Page 3 of 3





(feet bgs)


Lewis Well G-97-S-8 35.63740 –108.77715 3,310 2,810.5–2,874.5 2,910.5–2,974.5 2,994.5–3,014.5 3,034.5–3,074.5 3,090.5–3,198.5

Dakota Westwater 13⅜-inch casing to 2,624 feet, 7-inch casing from 2,624 to 3,310 feet.

Munoz Well G-96-S-17 35.62280 –108.76907 2,120 1,504–1,510 1,534–1,574 1,630–1,650 1,678–1,683 1,690–1,700 1,710–1,740 1,748–1,772 1,808–1,842 1,894–1,990 2,002–2,024

Gallup Sandstone 16-inch-inner diameter casing to 1,300 feet, 8⅝-inch casing from 1,300 to 2,120 feet.

Pena Well G-96-S-23 35.65388 –108.78296 2,523 1,380–1,420.2 1,460.4–1,560.7 1,600.8–1,660.9 1,701–1,721 1,761–1,881.4 1,981.8–2,062 2,102–2,142.2 2,202.3–2,442.9

Gallup Sandstone 10¾-inch casing to 2,523 feet.

Ray Well G-96-S-19 35.63735 –108.79282 2,147 1,238–2,007 Gallup Sandstone 16-inch casing to 1,212.7 feet, 8⅝-inch casing to 2,147 feet.


Table 2. Navajo Nation Existing Well Information

Page 1 of 2

Source: Foley, 2012 msl = Above mean sea level NTUA = Navajo Tribal Utility Authority a

UTM NAD 27, Zone 12 bgs = Below ground surface IHS = Indian Health Service

O&M = Operations and maintenance OEHE = Office of Environmental Health and Engineering

P:\_WR12-085\Sec8-GW Study.O-12\T02_NvjoWellInfo.doc


Location a Screened Interval(s) (feet bgs)

Well No. North (feet)

East (feet) Operator Well Use Well Type Well Status

Completion Date

Elevation (feet msl)

Depth (feet bgs) Aquifer

14A-79 3955057 709328 Tribe O&M Domestic Artesian Active 3/31/1937 6,240 873 713–873 Dalton Sandstone Member of Crevasse Canyon Formation of Mesaverde Group

14K-313 3949416 720174 Tribe O&M Livestock Water Active 5/02/1953 7,005 622 560–600 Gallup Sandstone

14P-558 3953834 721550 — Domestic Artesian Abandoned — — — — —

14T-321 3956333 714454 Tribe O&M Livestock Water Active 10/10/1958 6,379 1,082 580–1,082 Gallup Sandstone

14T-324 3961110 723155 Tribe O&M Domestic Artesian Active 3/25/1957 6,120 505 421–505 Mesaverde Group

14T-510 3951900 707775 Tribe O&M Domestic Artesian Active 5/09/1960 6,400 818 550–560 590–610 630–730 750–770 790–815

Crevasse Canyon Formation of Mesaverde Group

14T-524 3953540 713450 Tribe O&M Domestic Artesian Active 7/22/1958 6,645 726 240–726 Dalton Sandstone Member of Crevasse Canyon Formation of Mesaverde Group

14T-538 3954606 720037 Tribe O&M Domestic Water Active — — — — —

14T-540 3952063 713503 Tribe O&M Agricultural Artesian Active — — — — —

14T-542 3960084 714886 Unknown Unknown Artesian Active — — — — —

14T-545 3957213 714066 — Unknown Artesian Unknown — — — — —

14T-546 3957857 716400 — Domestic Artesian Unknown — — — — —


14T-552 3953029 712457 — Unknown Artesian Active — — — — —

14T-553 3958098 725332 Unknown Unknown Artesian Unknown — — — — —

14T-555 3957133 711813 NTUA Municipal Artesian Active 5/31/1973 6,242 2,520 300–400 Menefee Formation of Mesaverde Group

14T-559 3960538 717469 Unknown Livestock Water Inactive 8/01/1973 6,407 2,636 981–1,100 Gallup Sandstone

14T-563 3957529 729516 — Unknown Water Unknown — — — — —







14T-579 3959892 728544 Tribe O&M Livestock Artesian Active 10/31/1974 6,490 2,670 — —

14T-584 3954030 726143 Kerr-McGee Unknown Water Inactive 8/09/1975 6,080 1,160 Mesaverde Group

14T-586 3949101 724991 Tribe O&M Domestic Water Active 3/27/1976 7,090 750 — Mesaverde Group

Table 2. Navajo Nation Existing Well Information

Page 2 of 2

Source: Foley, 2012 msl = Above mean sea level NTUA = Navajo Tribal Utility Authority a

UTM NAD 27, Zone 12 bgs = Below ground surface IHS = Indian Health Service

O&M = Operations and maintenance OEHE = Office of Environmental Health and Engineering

P:\_WR12-085\Sec8-GW Study.O-12\T02_NvjoWellInfo.doc


Location a Screened Interval(s) (feet bgs)

Well No. North (feet)

East (feet) Operator Well Use Well Type Well Status

Completion Date

Elevation (feet msl)

Depth (feet bgs) Aquifer

14T-592 3955684 722033 Tribe O&M Unknown Water Active — — — — —

15T-303 3950171 728291 Tribe O&M Livestock Water Active 1/11/1952 7,038 614 537–614 Gallup Sandstone

16-0666 3932610 728725 Tribe O&M Domestic Artesian Active 1/27/1988 6,900 1,419 1,134–1,166 1,180–1,194

San Andres Limestone

16-0668 3931586 728194 IHS OEHE Domestic Water Inactive 1/10/1994 6,850 1,171 900–910 970–1,098

Glorieta Sandstone Member of San Andres Formation

16K-340 3941251 717664 Tribe O&M Livestock Water Active 6/23/1954 6,682 141 101–141 Quaternary alluvium

16T-510 3944092 715269 Tribe O&M Livestock Water Active 8/30/1960 6,818 680 520–550 575–595 620–630

Dakota Sandstone

16T-513 3943735 724982 Tribe O&M Domestic Water Active 7/27/1959 6,875 318 206–318 Westwater Canyon Member of Morrison Formation

16T-532 3944640 721605 Tribe O&M Livestock Water Inactive — 6,810 450 — —

16T-534 3941570 713451 Tribe O&M Domestic Water Active 7/29/1965 6,825 410 300–410 Westwater Canyon Member of Morrison Formation

16T-535 3941105 728297 Tribe O&M Domestic Water Active 10/28/1965 7,115 1,052 628–896 974–1,033

Entrada Sandstone

16T-537 3933850 729270 Tribe O&M Municipal Water Active 6/17/1967 7,005 1,367 — San Andres Limestone

16T-538A 3934560 714167 NTUA Municipal Water Active 1/26/1966 — 148 — Chinle Group

16T-538B 3934570 714280 NTUA Municipal Water Active 1/24/1966 6,610 148 — Chinle Group

16T-538C 3934670 715080 Unknown Unknown Water Abandoned — 6,610 86 — —

16T-538D 3934560 715400 Unknown Unknown Water Abandoned — 6,620 87 — —

16T-538E 3934550 715790 NTUA Municipal Water Active 3/25/1966 6,620 88 — Chinle Group

16T-538UNC 3934552 716127 NTUA Municipal Water Active — 6,625 56 — Chinle Group

16T-560 3941439 734032 Tribe O&M Other Unknown Active 7/26/1971 7,212 398 373–393 Todilto Limestone

16T-602 3934340 717300 NTUA Municipal Water Active 1/29/1971 6,647 120 — Chinle Group

16T-603 3934540 717270 NTUA Municipal Water Inactive 1/18/1971 6,659 136 — Chinle Group

16T-606 3943978 721599 Tribe O&M Livestock Water Active 7/03/1980 6,780 417 277–417 Dakota Sandstone

16T-612 3939874 732252 Tribe O&M Unknown Water Active — — — — —

KM CR II G-1 3950821 723956 Kerr-McGee Other Observation Abandoned 10/31/1977 7,290 1,090 857–1,030 Gallup Sandstone

KM CR II G-2 3950753 724012 Kerr-McGee Other Observation Abandoned 10/31/1977 7,290 1,090 857–1,030 Gallup Sandstone

KM CR II G-3 3950770 723932 Kerr-McGee Other Observation Abandoned 10/31/1977 7,290 1,090 857–1,030 —

KM CR II W-2 3950870 723958 Kerr-McGee Other Observation Abandoned 10/31/1977 7,290 2,514 2,019–2,383 Westwater Canyon Member of Morrison Formation

WGT ORDN 2 3930846 719681 — Unknown Water Unknown — — — — —

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Table 3. Recommended Municipal Conjunctive Groundwater Development, Navajo-Gallup Water Supply Project

Well Location a (Navajo Chapter) Number of Wells Proposed Target Aquifer

Estimated Well Depth

(feet)

Estimated Well Production

(gpm)

Churchrock 2 Chinle Group 2,000 30

Coyote Canyon 2 Dalton Sandstone of the Crevasse Canyon Formation

1,500 60

Iyanbito 2 Glorieta Sandstone 2,000 125

Nahodishgish (Dalton Pass)

2 Gallup Sandstone 2,000 20

Pinedale No groundwater component recommended

— — —

Rock Springs 3 Gallup Sandstone 1,700 40

Tsayatoh No groundwater component recommended

— — —

Twin Lakes No groundwater component recommended

— — —

Source: USBR, 2009 a

Well project data for Navajo Nation chapters located near the 10-mile radius of interest. gpm = Gallons per minute

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Table 4. Navajo Nation Conjunctive Groundwater Projects

Project Location a (Navajo Chapter) Description Basin Target Aquifer

Estimated Well Depth

(feet)

Churchrock Install 14 new wells; intertie to Mariano Lake using 12 miles of 10-inch PVC; intertie to Iyanbito using 2 miles of 10-inch PVC

Little Colorado (New Mexico)

Alluvial 160

Coyote Canyon Install 8 new wells; intertie to Standing Rock using 3.5 miles of 10-inch PVC

San Juan Menefee 2,600

Iyanbito Install 2 new wells; intertie to Churchrock using 2 miles of 10-inch PVC; intertie to Thoreau using 9 miles of 10-inch PVC

Little Colorado (New Mexico)

San Andres/ Glorieta

1,500

Nahodishgish (Dalton Pass)

Intertie to Standing Rock using 2 miles of 10-inch PVC (no wells planned)

San Juan Westwater 2,600

Pinedale No projects planned — Entrada at Mariano Lake

1,700

Rock Springs Install 4 new wells Little Colorado (New Mexico)

Gallup 1,900

Tsayatoh Install 4 new wells Little Colorado (New Mexico)

Gallup 1,400

Twin Lakes Install 1 new well San Juan Westwater 3,500

Source: NNDWR, 2010 a Well project data for Navajo Nation chapters located near the 10-mile radius of interest.

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Table 5. General Hydraulic Characteristics of Aquifers Near Section 8

Thickness (feet)

Yield (gpm) Transmissivity (ft2/d) Geologic Unit Range Median

Alluvial aquifer Variable — — 15–1,000 a

Point Lookout Sandstone 40–415 a 1–360 b 20 b 1–240 a

Menefee Formation 700–800 c 2–308 b 10g 35–40 c

Crevasse Canyon Formation 420–700 a — — <50 a

Gallup Sandstone of Mesaverde Group 0–600 d 1–645 b,d 30 d 5–930 b,c

Dakota Sandstone 50–370 a,c 1–200 d 13 d 44–85 a,b

Morrison Formation 330–915 a 1–401 c 30 b 2–480 a,b

Westwater Canyon Sandstone 250 a

San Rafael Group 150–800 e 3–200 f 5 c 3–300 a

Cow Springs-Bluff Sandstone 60–400 a,c

Summerville Formation 90–185 c

Todilto Limestone 0–140 c

Entrada Sandstone 0–130 c 5–350 a

Chinle Group 150–500 f <10 c — —

San Andres Limestone/Glorieta Sandstone

400–550 c — — 5–90 a,g

a Stone et al., 1983

e Includes Bluff Sandstone, Summerville Formation, Todilto Limestone, and Entrada Sandstone members

b Kernodle, 1996

f Anderson et al., 2003

c Risser and Lyford, 1983

g Can be much higher within and near outcrop areas

d Dam, 1995

gpm = Gallons per minute ft2/d = Square feet per day — = Not available

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Table 6. Aquifer Properties of the Westwater Canyon Member Within Section 8

Well Transmissivity

(gpd/ft) Transmissivity

(ft2/d)

Hydraulic Conductivity a

(ft/d)

CR-5 926 123.8 0.61

CR-6 1,208 161.5 0.81

CR-8 1,326 177.3 0.88

gpd/ft = Gallons per day per foot of drawdown ft2/d = Square feet per day ft/d = Feet per day a

Hydraulic conductivity calculated using a 200-foot aquifer thickness

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Table 7. General Chemistry Water Quality Statistics Summary

Concentration (mg/L)

Statistic EC

(µS/cm) pH

Temper-ature (°C) Calcium Magnesium Sodium

Sodium + Potassium Potassium Bicarbonate Sulfate Chloride Fluoride Bromide Silica Nitrate Boron Iron

Total Dissolved

Solids

EPA Standard NS 6.5-8.5 a NS NS NS NS NS NS NS 250 a 250 a 4.0 b, 2.0 a NS NS 10 b NS 0.3 a 500 a

Alluvial Aquifer

Minimum 405 6.8 6.0 2 0 7 11 ND 140 18 7 ND NR 10 ND 0.03 ND NR

Geometric mean 1,503 7.7 15.3 87 37 136 121 3 320 345 45 1 NR 22 2 c 0.165 0.24 c NR

Maximum 10,100 9.1 24.0 590 390 850 1,900 11 940 4,000 1,300 4 NR 60 8 0.84 2.8 NR

Gallup Sandstone

Minimum NR 7.8 15.5 0.28 0.06 36 NR 0.7 170 19 2.8 0.3 0.034 9.9 NR NR 0.016 210

Geometric mean NR 8.4 21.9 10.54 2.63 216 NR 1.9 289 276 19.3 0.8 0.07 13.3 NR NR 0.082 847

Maximum NR 9.2 32.9 400 120 720 NR 6.4 610 1,700 240 4.4 0.16 17 NR NR 0.64 3,200

Dakota Sandstone

Minimum NR 7.6 15.5 1 0.16 100 NR 1.1 140 25 2.6 0.2 0.038 8.5 NR NR 0.017 262

Geometric mean NR 8.5 17.7 16 3.39 326 NR 3 241 365 48.5 0.9 0.078 9.7 NR NR 0.081 1,002

Maximum NR 9.4 19.5 170 95 1,300 NR 11 360 1,600 720 8.2 0.16 12 NR NR 0.68 3,780

Morrison Formation

Minimum NR 7.52 15.4 0.86 0.06 42 NR 0.3 57 3 0.8 0.2 0.035 10 NR NR 0.003 167

Geometric mean NR 8.59 24.1 8.11 1.21 226 NR 1.8 179 156 15.8 0.9 0.11 17 NR NR 0.095 725

Maximum NR 9.65 51.8 160 28 1,700 NR 18 383 3,800 750 8 0.38 35 NR NR 0.98 6,000

Entrada Sandstone

Minimum 754 8 15 19 0 200 140 7 280 100 12 1 ND 8 ND 0.84 0.63 NR

Geometric mean 1,994 9 17 38 11 c 787 246 8 355 204 35 1 ND 10 ND 1.12 0.63 NR

Maximum 8,500 9 21 130 31 2,800 530 9 420 1,200 210 2 1 13 3 1.4 0.63 NR

Chinle Group

Minimum 160 7 13 0 0 21 10 ND 34 9 1 ND ND 5 ND 0.01 ND NR

Geometric mean 6,539 c 8 17 51 84 c 410 337 5 360 442 111 1 4 13 1 c 0.55 1.43 c NR

Maximum 65,000 10 34 1,100 460 12,000 5,800 260 1,910 4,800 27,000 4 45 30 17 6.0 22.0 NR

San Andres-Glorieta

Minimum 420 6.2 1.5 1.6 0.1 6.9 3 0.8 3 19 3.8 ND 0.05 6.7 ND ND ND NR

Geometric mean 2,879 c 7.3 17.4 148.4 40.5 91.0 64 5.5 349 c 626 c 166 c 0.7 c 0.45 15.7 2.7 c 0.97 c 1.77 c NR

Maximum 165,000 12 53 5,800 290 3,900 2,800 120 1,840 6,200 3,000 4 7 53 17 8.7 30.0 NR

Bold indicates that value exceeds the applicable water quality standard. mg/L = Milligrams per liter NS = No standard set a

U.S. Environmental Protection Agency (EPA) (2009) secondary drinking water standard (non-enforceable, aesthetic) EC = Electrical conductivity ND = Not detected b

U.S. EPA (2009) primary drinking water standard µS/cm = Microsiemens per centimeter NR = Not reported c Calculated as mean value °C = Degrees Celsius

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Table 8. Trace Elements Water Quality Statistics Summary

Concentration (mg/L)

Statistic Aluminum Arsenic Barium Iron Manganese Molybdenum Selenium Strontium Vanadium

EPA Standard 0.05–0.2 a 0.010 b 2 b 0.3 a 0.05 a NS 0.05 b NS NS

Gallup Sandstone

Minimum 0.01 0.002 0.014 0.016 0.002 0.003 0.01 0.018 ND

Geometric mean 0.01 0.002 0.034 0.082 0.010 0.003 0.01 0.119 ND

Maximum 0.01 0.002 0.1 0.64 0.15 0.003 0.01 0.92 ND

Dakota Sandstone

Minimum ND 0.001 0.01 0.017 0.007 ND ND 0.14 0.002

Geometric mean ND 0.001 0.015 0.081 0.023 ND ND 0.62 0.002

Maximum ND 0.001 0.024 0.68 0.06 ND ND 3.3 0.002

Morrison Formation

Minimum 0.01 0.001 0.01 0.003 0.001 0.001 0.003 0.038 0.003

Geometric mean 0.02 0.003 0.032 0.095 0.015 0.004 0.003 0.528 0.003

Maximum 0.03 0.012 0.1 0.98 0.13 0.03 0.003 11 0.003

Bold indicates that value exceeds the applicable water quality standard. NS = No primary or secondary standard set a U.S. Environmental Protection Agency (EPA) (2009) secondary drinking water standard (non-enforceable, aesthetic) ND = Not detected b U.S. EPA (2009) primary drinking water standard

section 8 / navajo-gallup groundwater report and ... · this report discusses the results of the...

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