GLOSSARY

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GLOSSARY

Aquifer

An underground geological formation or group of formations containing water, 

which may be a source of groundwater for wells and springs.

Background Radiation 

The natural radiation that is always present in the environment. It includes cosmic 

radiation which comes from the sun and stars; terrestrial radiation which comes 

from the Earth; and internal radiation which exists in all living things. 

Background (Baseline) Water Quality

The constituents or parameters and the concentrations or measurements which 

describe water quality and water quality variability prior to the injection of 

lixiviant.

Borehole 

A hole that is drilled into the earth for exploration (exploration hole or drill hole) 

and/or for completion as a well (wellbore).

Casing

The pipe material, slightly smaller than the diameter of the drilled hole (the 

wellbore), placed inside the wellbore and cemented in place to prevent collapse 

of the wellbore. Casing seals off water-bearing strata that have been drilled 

through, preventing the wellbore from filling with water from that strata and the 

completed well from introducing water into that strata.

Checkerboard Land Pattern 

Alternating sections of federally owned lands and private or state lands on either 

side of the UPRR in southwestern Wyoming. This pattern of land ownership 

looks like a checkerboard on maps, using different colors to show land status. 

Cone of Depression

Depression of the water table (in an unconfined aquifer) or potentionmectic 

surface (in a confined aquifer) that develops around a well (or wells) from which 

water is being pumped.

Confined Aquifer 

An aquifer that is overlain by a confining bed, where the hydrostatic pressure at 

the top of the aquifer is greater than atmospheric pressure.
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Confining Zone

A geological formation (or part of a formation or group of formations) capable of 

limiting fluid movement out of an injection zone. The ideal confining zone has 

low permeability and sufficient thickness to prevent upward movement of the 

injected fluid.

Decommissioning

The process of removing a facility or site from operation, followed by 

decontamination, and license termination (or termination of authorization for 

operation) if appropriate. The objective of decommissioning is to reduce the 

residual radioactivity or contaminants in structures, materials, soils, groundwater, 

and other media at the site so that the concentration of each radionuclide 

contaminant that contributes to residual radioactivity is within the cleanup limits 

established for the site. 

Decontamination

A process used to reduce, remove, or neutralize radiological, chemical, or 

biological contamination to reduce the risk of exposure. Decontamination may be 

accomplished by cleaning or treating surfaces to reduce or remove the 

contamination; filtering contaminated air or water; subjecting contamination to 

evaporation and precipitation; or covering the contamination to shield or absorb 

the radiation. The process can also simply allow adequate time for natural 

radioactive decay to decrease the radioactivity. 

Dispersed Recreation 

Recreation activities of an unstructured type that are not confined to specific 

locations such as recreation sites. An example of these activities may be hunting, 

fishing, OHV use, hiking, and sightseeing. 

Drawdown

The distance between the static water level and the water level during pumping. 

Drilling Fluid

A water- or air-based fluid used in well drilling to remove cuttings from the 

borehole, to clean and cool the bit, to reduce friction between the drilling 

equipment and the sides of the borehole, and to seal the borehole. Water-based 

fluids are usually referred to as drilling mud.

Effective Porosity 

The volume of the void spaces through which water or other fluids can travel in a 

rock or sediment divided by the total volume of the rock or sediment.

Excursion

Any unwanted and unauthorized movement of recovery fluid out of the 

production zone as a result of in situ mining activities. 
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Exempted Aquifer

An aquifer or its portion that meets the criteria in the definition of "Underground 

Source of Water" but which has been exempted according to specific regulatory 

procedures.

Fire Suppression 

All work and activities associated with fire-extinguishing operations, beginning 

with discovery and continuing until the fire is completely extinguished. 

Forage 

All browse and herbaceous foods available to grazing animals that may be grazed 

or harvested for feeding. 

Fugitive Dust 

Airborne emissions of visible and nonvisible fine, dry particulate matter smaller 

than 100 micrometers (microns) that result from surface disturbance activities.

Greater Sage-grouse Core Area 

Areas delineated by the State of Wyoming with the intent of protection of greater 

sage-grouse populations and habitat as established in State of Wyoming Executive 

Order 2011-05, Greater Sage-grouse Core Area Protection. 

Groundwater Restoration

The condition achieved when the quality of all groundwater affected by the 

injection of recovery fluids is returned to a quality of use equal to or better than, 

and consistent with the uses for which the water was suitable prior to the 

operation by employing the best practicable technology;"

Grout 

A fluid mixture of cement and water (neat cement) of a consistency that can be 

forced through a pipe and placed as required. Various additives, such as sand, 

bentonite, and hydrated lime, may be included in the mixture to meet certain 

requirements. 

Grouting

Placement of grout between the casing and the side of the wellbore to secure the 

casing in place and exclude water and other fluids from the wellbore.

Health Physics

The science concerned with recognizing and evaluating the effects of ionizing 

radiation on the health and safety of people and the environment, monitoring 

radiation exposure, and controlling the associated health risks and environmental 

hazards to permit the safe use of technologies that produce ionizing radiation. 
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Hydraulic Conductivity

A measure of the capacity of a porous medium to transmit fluid, governed by the 

characteristics of the medium (porosity and permeability) and the physical 

properties of the fluid.

Hydraulic Gradient 

The change in static head or hydraulic potential per unit distance in a given 

direction.

Injection Well

For the purposes of in situ mining, a well or conduit through which recovery fluid 

is introduced into the subsurface. If a well is used for both injection and recovery, 

it is considered an injection well.

Invasive Weed 

A species that is not native (or is alien) to the ecosystem under consideration and 

whose introduction causes or is likely to cause economic or environmental harm 

or harm to human health. 

Ion Exchange

A common method for concentrating uranium from a solution. The uranium 

solution is passed through a resin bed where the uranium-carbonate complex ions 

are transferred to the resin by exchange with a negative ion like chloride. After 

build-up of the uranium complex on the resin, the uranium is eluted with a salt 

solution and the uranium is precipitated in another process. 

Lixiviant

A liquid medium that selectively extracts the desired metal from the ore or 

material to be leached rapidly and completely, and from which the desired metal 

can then be recovered in a concentrated form. A liquid medium used to 

selectively extract (or leach) uranium from ore bodies where they are normally 

found underground (in other words, in situ). This liquid medium, which typically 

contains an oxidant such as oxygen and/or hydrogen peroxide mixed with sodium 

carbonate or carbon dioxide, is injected through wells into the ore body in a 

confined aquifer to dissolve the uranium. The resulting solution is then pumped 

via other wells to the surface, where the uranium is recovered from it in a 

concentrated form for processing. 

Mechanical Integrity

The absence of significant leakage within the injection tubing, casing, or packer 

(known as internal mechanical integrity), or outside of the casing (known as 

external mechanical integrity). Mechanical Integrity Tests (MITs), conducted in 

accordance with approved methods, are required before well use to measure the 

adequacy of the construction of an injection well, and periodic MITs are needed 
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to confirm that an injection well maintains internal and external mechanical 

integrity. 

Mill Tailings 

Primarily, the sandy process waste material from a conventional uranium 

recovery facility. This naturally radioactive ore residue contains the radioactive 

decay products from the uranium chains (mainly the U-238 chain) and heavy 

metals. 

Mineral Right 

The ownership of the minerals under a given surface, with the right to enter 

thereon, mine, and remove them. It may be separated from the surface ownership.

Mine Unit (Wellfield)

The area of an in situ recovery operation that encompasses the array of injection 

and production wells (the Pattern Area) and the area out to the surrounding 

monitor well ring. 

Mining (Mineral) Lease 

A legal contract for the right to work a mine and extract the mineral or other 

valuable deposits from it under prescribed conditions of time, price, rental or 

royalties. 

Mitigation (Mitigating Measure)

An action aimed at reducing the severity, avoiding, or controlling impacts of a 

project through design alternatives, scheduling, or other means. A method or 

process by which impacts from actions can be made less injurious to the 

environment through appropriate protective measures. 

Monitoring 

Continuous or periodic measurement of a parameters or set of parameters to 

determinate of the status of a system.

Monitor Well

A well used to measure the water level in an aquifer and/or the chemical and 

radiological composition of the water in the aquifer. For the purposes of in situ 

mining, a monitor well ring is usually located around the pattern area in a mine 

unit, and monitor wells are also completed in overlying or underlying aquifers to 

detect lixiviant migration outside the pattern area (see Excursion). Monitor wells 

are also used to establish baseline conditions with and outside of the potential 

mine units.

Multiple Use

Coordinated management of various surface and subsurface resources so that they 

are used in the combination that will best meet present and future needs.
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National Register of Historic Places (NRHP)

The official register of districts, sites, buildings, structures, and objects significant 

in American history, architecture, archaeology, and culture, established by the 

National Historic Preservation Act of 1966, as amended, and maintained by the 

National Park Service on behalf of the Secretary of the Interior.

Natural Uranium 

Uranium containing the relative concentrations of isotopes found in nature (0.7 

percent uranium-235, 99.3 percent uranium-238, and a trace amount of uranium234 by mass). In terms of radioactivity, however, natural uranium contains 

approximately 2.2 percent uranium-235, 48.6 percent uranium-238, and 49.2 

percent uranium-234. 

Noxious Weed

A plant species designated by federal or state law as generally possessing one or 

more of the following characteristics: aggressive and difficult to manage; 

parasitic; a carrier or host of serious insects or disease; or non-native, new, or not 

common to the United States. 

Ore

A mixture of ore minerals and gangue from which at least one of the metals can 

be extracted at a profit. The term ‘ore’ denotes economically recoverable 

quantities of one or more of the ore minerals.

Oxidation

A chemical reaction caused by exposure to oxygen that results in a change in the 

chemical composition of a mineral and involves the formal transfer of electrons, a 

net gain in electrons being a reduction and a net loss of electrons being an 

oxidation.

Pattern Area

The area of an in situ recovery operation that encompasses the array of injection 

and production wells.

Perched Water 

Unconfined groundwater separated from an underlying body of groundwater by 

an unsaturated zone, such as a clay lens.

Permeability

The ability of rock or soil to transmit water (or other fluid) under a hydraulic 

gradient.

Potentiometric Surface 

The level to which water will rise in a well completed in a confined aquifer.
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Porosity 

The voids or openings in a rock. Porosity may be expressed quantitatively as the 

ratio of the volume of openings in a rock to the total volume of the rock.

Production Zone

The geologic interval into which recovery fluids are to be injected or extracted.

Pump Test

A test involving the withdrawal of measured quantities of water form a well and 

the measurement of resulting changes in head in the aquifer both during and after 

the pumping.

Radionuclide 

An unstable isotope of an element that decays or disintegrates spontaneously, 

thereby emitting radiation. Approximately 5,000 natural and artificial 

radioisotopes have been identified. 

Pump Test

A test involving the withdrawal of measured quantities of water form a well and 

the measurement of resulting changes in head in the aquifer, in the pumped well 

and adjacent monitoring wells, during and after the pumping.

Reclamation

The ‘reconstruction’ of a site, after mining or exploration activity is completed, to 

a condition appropriate for the approved post-exploration or post-mining land use. 

Activities may include equipment removal, well plugging, surface contouring, 

topsoil replacement, and revegetation.

Resource Management Plan (RMP)

A land use plan, as prescribed by the FLPMA, that establishes, for a given area of 

land, land-use allocations, coordination guidelines for multiple use, and objectives 

and actions to be achieved.

Reduction 

The addition of hydrogen, removal of oxygen, or addition of electrons to an 

element or compound resulting in a net gain in electrons.

Reverse Osmosis

The act of reversing a diffusion through a semipermeable membrane, typically 

separating a solvent and a solution, that tends to equalize their concentrations.

Roll Front

A type of uranium deposition localized as a roll or interface separating an 

oxidized interior from a reduced exterior. The reduced side of this interface is 

significantly enriched in uranium.
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Site Characterization

Detailed surface and subsurface investigations and activities to obtain information 

to determine the suitability of the site for the proposed action.

Storage Coefficient 

The volume of water release from storage in a unit prism of an aquifer when the 

head is lowered a unit distance.

Surface Disturbance

Any action created through mechanized or mechanical means that would cause 

soil mixing or result in alteration or removal of soil or vegetation and expose the 

mineral soil to erosive processes. Used in the literal context of actual, physical 

disturbance and movement or removal of the land surface and vegetation. 

Examples of surface disturbance include construction of well pads, pits, 

reservoirs, pipelines, and facilities (e.g., parking lot and tanks).

Transmissivity 

Rate at which water is transmitted through a unit width of the aquifer under a unit 

hydraulic gradient. It is expressed as the product of the hydraulic conductivity 

and the thickness of the saturated portion of the aquifer.

Trend Well

A monitor well (or series of monitor wells) installed to provide more detailed 

information in a specific area of a mine unit.

Unconfined Aquifer 

Upper limit of the aquifer is defined by the water table (level) itself. At the water 

table (the top of the saturated portion of the geologic formation), the water in the 

pores of the aquifer is at atmospheric pressure (as if it were in an open tank). 

Unconformity

The contact between older rocks and younger sedimentary rocks in which at least 

some erosion has removed some of the older rocks before deposition of the 

younger. The boundary between the two different rock sequences represents an 

interval of time during which new strata were not deposited and/or were eroded.

Underream

To enlarge the wellbore below the casing.

Unsaturated Zone 

The zone in which the pore openings of the functional permeable rocks are not 

(except temporarily) filled with water under hydrostatic pressure; the interstices 

are either not filled with water or are filled with water that is held by capillarity.
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Upper Control Limit (UCL)

A value greater than the maximum value of a chemical or physical parameter that 

can be attributed to natural fluctuations and analytical variability. UCL 

parameters and amounts are determined from the baseline sampling and agreed 

upon by the WDEQ-LQD and the operator prior to initiation of mining. UCLs are 

used to determine when there is movement of recovery fluid out of authorized 

areas or unapproved changes to a chemical or physical parameter. For certain 

parameters, such as pH, a UCL may be defined as an acceptable range of values.

Viewshed

Total visible area from a single observer’s position or the total visible area from 

multiple observer positions. Viewsheds are accumulated seen areas from 

highways, trails, campgrounds, towns, cities, or other view locations. Examples 

are corridors, feature, or basin view-sheds.

Visual Resource

Visible feature of the landscape, such as land, water, vegetation, and other 

features that make up the scenery of an area.

Visual Resource Inventory (VRI)

An inventory of visual resources in a defined area that serves as a baseline for 

BLM resource management decisions. The inventory determines the visual 

(scenic) values within a defined area at a specific point in time. The three primary 

components to a visual resource inventory include: scenic quality evaluation, 

sensitivity level analysis, and distances zones.

Visual Resource Management (VRM)

The system by which the BLM classifies and manages scenic values and visual 

quality of public lands. The system is based on research that has produced ways 

of assessing aesthetic qualities of the landscape in objective terms. After 

inventory and evaluation, lands are given relative visual ratings (management 

classes) that determine the amount of modification allowed for the basic elements 

of the landscape.

Wellbore

A hole drilled and completed as a well for the purpose of exploration or extraction 

of natural resources, such as an injection, production, or monitoring well, where 

the well may be produced or monitored for some period of time.

Wellfield (see Mine Unit)

Yellowcake 

The solid form of mixed uranium oxide produced from uranium ore. The material 

is a mixture of uranium oxides, varying in proportion and color from yellow to 

orange to dark green (blackish) depending on the temperature at which the 

material is dried (which affects the level of hydration and impurities), with higher 
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drying temperatures producing a darker and less soluble material. (The 

yellowcake produced by most modern mills is actually brown or black, rather than 

yellow, but the name comes from the color and texture produced by early milling 

operations.) Yellowcake is commonly referred to as U3O8, because that chemical 

compound comprises approximately 85 percent of the yellowcake produced by 

uranium recovery facilities. Yellowcake must be transported to a uranium 

conversion facility, for conversion into uranium hexafluoride (UF6), in 

preparation for fabricating fuel for nuclear reactors.