GLOSSARY 

GLOSSARY 

7Q10. A statistical measure for the lowest flow 

expected for a continuous 7-day period in 10 years. 

ABANDON. To cease producing gas from a well 

when it becomes unprofitable. A wildcat 

(exploration) well may be abandoned after it has been 

proven nonproductive. Usually, some of the casing is 

removed and salvaged, and one or more cement plugs 

placed in the borehole to prevent migration of fluids 

between formations. 

ABNORMAL PRESSURE. Pressure exerted by a 

formation and exceeding or falling below the normal 

pressure to be expected at a given depth. Normal 

pressure increases approximately 0.433 psi per foot 

of depth. Formations with abnormally high pressure 

must be controlled to prevent a blowout. 

ACID NEUTRALIZING CAPACITY. The extent 

to which natural water bodies are able to buffer 

atmospheric deposition of sulfate and/or nitrate 

particulate matter from air pollution emission 

sources. 

ACRE-FOOT. A term used in measuring the volume 

of fluid. An acre-foot is the amount of fluid required 

to cover 1 acre to a depth of 1 foot, or 43,560 cubic 

feet (325,829 gallons). 

AIR QUALITY. Air quality is based on the amount 

of pollutants emitted into the atmosphere and the 

dispersion potential of an area to dilute those 

pollutants. 

ALKALINITY. The quantity and kinds of 

compounds present in water that collectively shift the 

pH to the alkaline side of neutrality. See salinity. 

ALLOTMENT CATEGORIZATION. The 

grouping of livestock grazing allotments into the 

categories “M” (maintain current satisfactory 

condition), “I” (improve current unsatisfactory 

condition), and “C” (manage custodially while 

protecting existing resource values). 

ALLUVIUM. General term for debris deposited by 

streams on river beds, floodplains, and alluvial fans, 

especially deposits brought down during a flood. 

Applies to stream deposits of recent time. Does not 

include below water sediments of seas and lakes. 

ANIMAL UNIT. A standardized unit of 

measurement for range livestock or wildlife. 

Generally, one mature cow, one horse, five sheep, 

9.6 antelope, 5.8 deer, or 1.9 elk, based on an average 

forage consumption of 26 pounds of dry matter per 

day. 

ANIMAL UNIT MONTH. A standardized unit of 

measurement of the amount of forage necessary for 

the complete sustenance of one animal for one 

month; also, the measurement of the privilege of 

grazing one animal for one month. 

ANNULUS OR ANNULAR SPACE. The space 

around a pipe in a wellbore, the outer wall of which 

may be the wall of either the borehole or the casing. 

ANTICLINE. An arched, inverted-trough 

configuration of folded and stratified rock layers. 

AQUIFER. A body of rock that is sufficiently 

permeable to conduct groundwater and to yield 

economically significant quantities of water to wells 

and springs. 

APPLICATION FOR PERMIT TO DRILL, 

DEEPEN OR PLUG BACK (APD). The 

Department of Interior application permit form to 

authorize oil and gas drilling activities on federal 

land. 

AREA OF CRITICAL ENVIRONMENTAL 

CONCERN. An area that needs special management 

attention to preserve historic, cultural, or scenic 

values; to protect fish and wildlife resources or other 

natural systems or processes; or to protect life and 

provide safety from natural hazards. 

ARTESIAN. Groundwater with sufficient pressure 

to flow without pumping. 

BANKHEAD-JONES FARM TENANT ACT OF 

1937. This Act enabled the government to buy 

marginal farms and to put the farms back into 

grazing. 

BASIN. A closed geologic structure in which the 

beds dip toward the center; the youngest rocks are at 

the center of a basin and are partly or completely 

ringed by progressively older rocks. 

BEDROCK. The solid, unweathered rock underlying 

soils. 

 GLO-1
GLOSSARY 

BEST AVAILABLE CONTROL TECHNOLOGY 

(BACT). The best available air pollution control 

technology for a given emission source, considering 

environmental benefits, economic and energy costs, 

as defined by the applicable air quality regulatory 

authority. 

BITUMINOUS. The most abundant rank of coal 

(synonymous with soft coal). It is dark brown to 

black and burns with a smoky flame. 

BLOCK MANAGEMENT. Through cooperation 

with the Montana Fish, Wildlife, and Parks, a 

Memorandum of Understanding allows the BLM, the 

private landowners, and Montana Fish, Wildlife, and 

Parks to close off some public lands administered by 

BLM in exchange for opening up private lands to 

hunting. This is done on a rotating basis from year to 

year. 

BLOOEY PIT. The pit that receives cuttings and 

other discharges from a well drilled with air. 

BLOWOUT. An uncontrolled expulsion of gas, 

oil, or other fluids from a drilling well. A blowout, or 

“gusher,” occurs when formation pressure exceeds 

the pressure applied to it by the column of drilling 

fluid and when blowout prevention equipment is 

absent or fails. 

BLOWOUT PREVENTER. Equipment installed at 

the well head to prevent the escape of pressure either 

from the annular space between the casing and drill 

pipe or from an open hole during drilling and 

completion operations. 

BRACKISH WATER. Water that contains 

relatively moderate concentrations of any soluble 

salts. Brackish water is saltier than fresh water but 

not as salty as salt water or brine water. 

BRINE. Water containing relatively large 

concentrations of dissolved salts, particularly sodium 

chloride. Brine has higher salt concentrations than 

ordinary ocean water. 

BRINE PIT. An excavated pit used to hold brine 

produced from a well. 

BROWSE. As a verb, to consume or to feed on (as a 

plant); as a noun, the tender shoots, twigs, and leaves 

of trees and shrubs, often used as food by cattle, 

antelope, deer, elk, and other animals. 

BUFFER ZONE. 

1. An area between two different land uses that is 

intended to resist, absorb or otherwise preclude 

developments or intrusions between the two use 

areas. 

2. A strip of undisturbed vegetation that retards 

the flow of runoff water, causing deposition of 

transported sediment and reducing sedimentation 

in the receiving stream. 

CANOPY COVER. The percentage of ground area 

under an overstory vegetation that would not be 

impacted by raindrops falling straight down. 

CASING. Steel pipe placed in a gas well to prevent 

the hole from caving. 

CHANNEL INTEGRITY (STABILITY). A 

relative term describing erosion or movement of the 

channel walls or bottom because of water flow. 

CHECKERBOARD PATTERN. One in which 

ownership of sections of land alternates between 

federal and other ownership, usually private. On a 

map with different colors denoting type of 

ownership, the pattern resembles a checkerboard. 

CLAYEY. A soil containing more than 35 percent 

clay. The textural classes are sandy clay, silty clay, 

clay, clay loam, and silty clay loam. 

CLEAN AIR ACT. Public Law 84-159, established 

July 14, 1955, and amended numerous times since. 

The Clean Air Act: establishes federal standards for 

air pollutants emitted from stationary and mobile 

sources; authorizes states, tribes and local agencies to 

regulate polluting emissions; requires those agencies 

to improve air quality in areas of the country which 

do not meet federal standards; and to prevent 

significant deterioration in areas where air quality is 

cleaner than those standards. The Act also requires 

that all federal activities (either direct or authorized) 

comply with applicable local, state, tribal and federal 

air quality laws, statutes, regulations, standards and 

implementation plans. In addition, before these 

activities can take place in non-attainment or 

maintenance areas, the federal agencies must conduct 

a Conformity Analysis (and possible Determination) 

demonstrating the proposed activity will comply with 

all applicable air quality requirements. 

CLOSED MUD SYSTEM. A drill mud system that 

reuses or reclaims all the drilling fluid used. 

Oil-based mud systems are often closed mud 

systems. 

 GLO-2
GLOSSARY 

COAL BED NATURAL GAS. A clean-burning 

natural gas found deep inside and around coal seams. 

The gas has an affinity to coal and is held in place by 

pressure from groundwater. Mining for coalbed 

methane involves drilling into coal seams and 

discharging large volumes of groundwater to release 

the gas. 

COLLUVIAL. Loose, incoherent geological 

deposits at the bottom of a slope or cliff, having 

fallen from above. 

COMMUNITIZATION. The pooling of mineral 

acreages based on the spacing for a well or wells set 

by the state or BLM. 

COMPACTION. The process of packing firmly and 

closely together; the state of being so packed; for 

example, mechanical compaction of soil by livestock 

or vehicular activity. Soil compaction results from 

particles being pressed together so that the volume of 

the soil is reduced. It is influenced by the physical 

properties of the soil, moisture content, and the type 

and amount of compactive effort. 

COMPLETION. The activities and methods to 

prepare a well for production. Includes installation of 

equipment for production from a gas well. 

CONDITION OF APPROVAL (COA). Conditions 

or provisions (requirements) under which an 

Application for a Permit to Drill or a Sundry Notice 

is approved. 

CONTINENTAL DEPOSITS. A sedimentary 

deposit laid down on land (whether a true continent 

or only an island) or in bodies of water (whether 

fresh or saline) not directly connected with the ocean, 

as opposed to a marine deposit; a glacial, stream, 

lake, or windborne deposit formed in a nonmarine 

environment. 

CONTROLLED SURFACE USE (CSU). Use or 

occupancy is allowed (unless restricted by another 

stipulation), but identified resource values require 

special operational constraints that may modify the 

lease rights. CSU is used for operating guidance, not 

as a substitute for the NSO or Timing stipulations. 

CONVEYANCE LOSS. The percentage reduction 

in water volume between the time it is discharged to 

the surface and the time it reaches a perennial stream. 

This reduction in volume is due to the processes of 

infiltration and evaporation. 

CORRIDOR. A strip of land through which one or 

more existing or potential facilities may be located. 

CROW RESERVATION. The Crow Reservation as 

established by the September 17, 1851 Ft. Laramie 

Treaty and by federal statues and case law. 

CRUCIAL WINTER RANGE. That portion of the 

winter range on which a wildlife species is dependent 

for survival during periods of heaviest snow cover. 

CULTURAL RESOURCE. A term that includes 

items of historical, archaeological, or architectural 

items; a remnant of human activity. 

CUMULATIVE IMPACT. The impact on the 

environment that results from the positive or negative 

impacts of an action when added to other past, 

present, and reasonable foreseeable future actions, 

regardless of what agency or person performed such 

action(s). 

DANCING GROUNDS. An area used in the spring 

by sharp-tailed grouse for courtship displays and 

breeding. 

DECIBEL OR dB. A unit for measuring sound 

intensity, usually measured on the decibel A 

weighted scale (dBA) which approximates the sound 

levels heard by the human ear at moderate sound 

levels. 

DECIVEW OR dV. A visual index appropriate for 

characterizing visibility through uniform hazes, 

designed to be linear with respect to perceived visual 

changes over its entire range (from pristine to 

polluted conditions) in a way that is analogous to the 

decibel scale for sound. The deciview haze index is 

calculated based on the logarithmic distribution of the 

extinction coefficient, where a 10.0 deciview change 

is about a 10 percent change in extinction coefficient; 

a small but perceptible scenic change under many 

circumstances (“just noticeable change”). 

DEEPER COAL SEAM. Designates a coal seam 

that is deep enough that it can be drilled to at a 

directional angle from a well pad in one spacing unit 

to another spacing unit. This avoids the need for 

constructing additional roads and well pads. The 

exact depth that the term “deeper” applies to is 

relative and will vary according to field spacing 

requirements and local geology. 

DEVELOPMENT WELL. A well drilled in proven 

territory (usually within 1 mile of an existing well). 

DISPOSAL WELL. A well into which produced 

water from other wells is injected into an 

underground formation for disposal. 

 GLO-3
GLOSSARY 

DRAINAGE (GEOMORPHIC). A collective term 

for all the water bodies by which a region is drained; 

or, all the water features shown on a map. 

DRAINAGE (OIL AND GAS). The uncompensated 

loss of hydrocarbons from Federal, Indian tribal or 

Indian-allotted mineral lands from wells on adjacent 

non-jurisdictional lands or jurisdictional lands with 

lower participation, allocation, royalty rate, or 

distribution of funds, resulting in revenue losses to 

the Federal or Indian lessors. 

DRILL DIRECTIONALLY. The technique of 

drilling at an angle from a location at the surface to a 

different subsurface location at a specific target 

depth. The degree of angle that a well can be drilled 

is limited, which is why this technique is not 

employed for shallow coal seams. 

DRILL RIG. The mast, drawworks, and attendant 

surface equipment of a drilling or workover unit. 

DRILL STEM TEST. The use of a drill-stem testing 

tool to test a formations potential productivity. The 

tool is lowered to the formation and is packed off 

from the above formations. The tool is then operated 

to sample the formation and the results recorded. 

Also, called a formation test. 

DROP STRUCTURE. An in-stream structure of 

various materials designed to reduce the energy and 

force of stream flow. 

DRY HOLE. Any well incapable of producing oil or 

gas in commercial quantities. A dry hole may 

produce water, gas or even oil, but not enough to 

justify production. 

ECOLOGICAL CONDITION. The present state of 

vegetation of a site in relation to the potential natural 

community for the site. Ecological status is use 

independent. It is an expression of the relative degree 

to which the kinds, proportions, and amounts of 

plants in a plant community resemble that of the 

potential natural community. Four ecological status 

classes correspond to 0-25, 26-50, 51-75, or 

76-100 percent similarity to the potential natural 

community and are generally called early seral, midseral, late seral, and potential natural community, 

respectively. 

ECOLOGICAL SITE. A kind of land with a 

specific potential natural community and specific 

physical site characteristics, differing from other 

kinds of land in its ability to produce vegetation and 

to respond to management. 

ECOSYSTEM. A biological community, together 

with its nonliving environment, forming an 

interacting system inhabiting an identifiable space. 

ELECTRICAL CONDUCTIVITY. A measure of 

the salt content of water. 

EMERGENT AQUATIC VEGETATION. An 

aquatic plant having part of its vegetative parts above 

water. 

EMISSION. Air pollution discharge into the 

atmosphere, usually specified by mass per unit time. 

ENDANGERED SPECIES. Those species of plants 

or animals classified by the Secretary of the Interior 

or the Secretary of Commerce as endangered 

pursuant to Section 4 of the Endangered Species Act 

of 1973, as amended. See also Threatened and 

Endangered Species. 

ENHANCED RECOVERY. The use of artificial 

means to increase the amount of hydrocarbons that 

can be recovered from a reservoir. A reservoir 

depleted by normal extraction practices usually can 

be restored to production by secondary or tertiary 

methods of enhanced recovery. 

ENTRAINED PARTICULATES. Particulates 

contained within auto exhaust; mainly made of 

carbons. 

EPHEMERAL STREAM. A stream that flows only 

after a storm or during snowmelt, and whose channel 

is, at all times, above the water table. 

EPOCH. An interval of time based on similar rock 

formations and fossil groups. Used primarily as 

subdivisions of the Tertiary and Quaternary Periods. 

EXPLORATION. Building a two-track road to drill 

test wells for coalbed methane. See also 

development. 

EXPLORATION WELL. A well drilled in an area 

where there is no oil or gas production. Same as a 

“wildcat” well. 

FAULT. A fracture surface in rocks along which 

movement of rock on one side has occurred relative 

to rock on the other side. 

FLOODPLAIN. The relatively flat area or lowlands 

adjoining a body of standing or flowing water that 

has been or might be covered by floodwater. 

FLOW LINE. A small diameter pipeline through 

which fluids move on lease before being sold. 

 GLO-4
GLOSSARY 

FORAGE. Forms of vegetation available for animal 

consumption. 

FORB. A broad-leaved herb that is not grass or 

grasslike. 

FORMATION (GEOLOGIC). A rock body 

distinguishable from other rock bodies and useful for 

mapping or description. Formations may be 

combined into groups or subdivided into members. 

FRAC FLOWBACK. During the drilling process, 

fluid or product returns along fractures in the rock to 

the point where it is difficult to control; for example, 

flowback from a point high in the borehole or at the 

ground surface away from the boring. 

FUGITIVE DUST. Airborne particles emitted from 

any source other than through a controllable stack or 

vent. 

GABIONS. A hollow cylinder of wickerwork or 

strap iron constructed like a basket, filled with stones 

and sunk to form a bar, dike, or similar structure. 

GEOMORPHIC. Pertaining to the form of the earth 

or its surface features. 

GROUND COVER. Vegetation, mulch, litter, or 

rocks. 

GROUNDWATER. Subsurface water that is in the 

zone of saturation. The top surface of the 

groundwater is the “water table.” Source of water for 

wells, seepage, and springs. 

GULLYING. The erosion process whereby water 

accumulates in narrow channels and, over short 

periods, removes the soil from the narrow area to 

considerable depths, ranging from 2 feet to as much 

as 80 to 100 feet deep. 

GULLY PLUG. Any form of material placed in an 

existing gully to reduce the erosional effects of 

moving water and thereby starting a healing process 

of the gully. 

HABITAT. In wildlife management, the major 

elements of habitat are considered to be food, water, 

cover, and living space. 

HAZARDOUS WASTE. (A) Any substance 

designated pursuant to section 311(b)(2)(A) of the 

Federal Water Pollution Control Act. (B) Any 

element, compound, mixture, solution, or substance 

designated pursuant to section 102 of this Act. 

(C) Any hazardous waste having the characteristics 

identified under or listed pursuant to section 3001 of 

the Solid Waste Disposal Act (but not including any 

waste the regulation of which under the Solid Waste 

Disposal Act has been suspended by Act of Congress. 

(D) Any toxic pollutant listed under section 307(a) of 

the Federal Water Pollution Control Act. (E) Any 

hazardous air pollutant listed under section 112 of the 

Clean Air Act. (F) Any imminently hazardous 

chemical substance or mixture with respect to which 

the Administrator has taken action pursuant to 

section 7 of the Toxic Substances Control Act. The 

term does not include petroleum, including crude oil 

or any fraction thereof which is not otherwise 

specifically listed or designated as a hazardous 

substance under subparagraphs (A) through (F) of 

this paragraph, and the term does not include natural 

gas, natural gas liquids, liquefied natural gas, or 

synthetic gas usable for fuel (or mixtures of natural 

gas and such synthetic gas). 

HYDROGEN SULFIDE or H2S. A colorless, 

highly flammable, and very toxic gas that smells like 

rotten eggs at low concentrations. At higher 

concentrations, the sense of smell is lost, therefore 

becoming impossible to perceive dangerous 

concentrations. 

INFILTRATION. The flow of a fluid into a solid 

substance through pores or small openings; 

specifically, the movement of water into soil or 

porous rock. 

INJECTION WELL. A well used to inject fluids 

into an underground formation to increase reservoir 

pressure. 

INTERMITTENT STREAM. A stream that flows 

most of the time but occasionally is dry or reduced to 

pool stage when losses from evaporation or seepage 

exceed the available streamflow. 

LAND AND WATER CONSERVATION FUNDS. 

Federal revenues generated by a tax on federal offshore oil and gas development through the Land and 

Water Conservation Fund Act; used to acquire highly 

desirable lands for the United States by the various 

governmental agencies. 

 GLO-5
GLOSSARY 

LEASABLE MINERALS. Federal minerals subject 

to lease under the Mineral Leasing Act of 1920, as 

amended, and supplemented. Includes minerals, such 

as oil, gas, coal, geothermal, tar sands, oil shale, 

potassium, phosphate, sodium, asphaltic materials. 

LEASE. 

1. A legal document that conveys to an operator 

the right to drill for oil and gas. 

2. The tract of land, on which a lease has been 

obtained, where producing wells and production 

equipment are located. 

LEASE NOTICE. Provides more detailed 

information concerning limitations that already exist 

in law, lease terms, regulations, or operational orders. 

A lease notice also addresses special items the lessee 

should consider when planning operations, but does 

not impose new or additional restrictions. Lease 

notices attached to leases should not be confused 

with NTLs (Notices to Lessees). 

LEK. A traditional breeding area for grouse species 

where territorial males display and establish 

dominance. 

LIGNITE. A brownish-black coal that is 

intermediate between peat and subbituminous coal. 

LITHIC SCATTER. The waste material, chips, and 

flakes resulting from stone tool manufacture. 

LOAMY. Soil that is intermediate in texture and 

properties between sandy and clayey soils. Textural 

classes are sandy loam, fine sandy loam, very fine 

sandy loam, loam, silt loam, sandy clay loam, and 

clay loam with clay content between 18 and 

35 percent. 

LOCALITY. The area where paleontologic material 

is discovered. 

LOCATABLE MINERALS. Minerals or materials 

subject to disposal and development through the 

Mining Law of 1872 (as amended). Generally 

includes metallic minerals such as gold and silver and 

other materials not subject to lease or sale. 

MESIC AREA. A habitat having a moderate amount 

of moisture available for the support of plant life. 

MINERAL MATERIALS. Widespread deposits of 

common clay, sand, gravel, or stone that are not 

subject to disposal under the 1872 Mining Law, as 

amended. 

MITIGATION MEASURES. Methods or 

procedures developed for the purpose of reducing or 

lessening the impacts of an action. 

MONITORING. Specific studies that evaluate the 

effectiveness of actions taken toward achieving 

management objectives. 

NATIONAL AMBIENT AIR QUALITY 

STANDARDS OR NAAQS. The allowable 

concentrations of air pollutants in the air specified by 

the federal government. The air quality standards are 

divided into primary standards (based on air quality 

criteria and allowing an adequate margin of safety 

requisite to protect the public health) and secondary 

standards (based on air quality criteria and allowing 

an adequate margin of safety to protect the public 

welfare from any unknown or expected adverse 

effects of air pollutants). 

NO SURFACE OCCUPANCY. Use or occupancy 

of the land surface for fluid mineral exploration or 

development is prohibited to protect identified 

resource values. 

NORTHERN CHEYENNE RESERVATION. The 

Northern Cheyenne Reservation as established by 

Executive Orders of November 26, 1884 and March 

19, 1900. 

NOTICE TO LESSEES (NTL). The NTL is a 

written notice issued by the Authorized Officer. 

NTLs implement regulations and operating orders, 

and serve as instructions on specific item(s) of 

importance within a State, District, or Area. 

PARENT MATERIAL. The unconsolidated and 

chemically-weathered mineral or organic matter from 

which the horizons of soils develop by natural 

processes. 

PARTICULATE MATTER. A particle of soil or 

liquid matter (e.g., soot, dust, aerosols, fumes and 

mist). 

PERENNIAL STREAM. A permanent stream that 

flows 9 months or more out of the year. 

PERMEABILITY. The ease with which gases, 

liquids or plant roots pass through a layer of soil. 

Accepted as a measure of this property is the rate at 

which soil transmits water while saturated, and may 

imply how well water passes through the least 

permeable soil layer. 

pH. A measure of acidity or alkalinity. A solution 

with a pH of 7 is neutral, pH greater than 7 (to 14) is 

alkaline, and a pH less than 7 (to 0) is acidic. 

 GLO-6
GLOSSARY 

PLANNING AREA. For this supplemental 

environmental impact statement, the planning area is 

the Billings and Powder River RMP areas. This is the 

13-county area within which the BLM has CBNG 

development interest. 

POST-FLPMA LEASES. Oil and gas leases issued 

after the passage of the Federal Land Policy and 

Management Act of 1976. Where occurring in 

Wilderness Study Areas, these leases have no valid 

existing rights and could not impair wilderness 

values. 

POTENTIAL NATURAL COMMUNITY. The 

biotic community that would become established if 

all successional sequences were completed without 

interferences under the present environmental 

conditions. 

PARTS PER MILLION (PPM). A measurement to 

identify the amount of particulates in air or water. 

POD. Describes the general location of a series of 

wells that tap individual coal seams within a single 

80-acre spacing unit. For example, within the Powder 

River Basin, three coal seams are layered beneath the 

surface. On the surface, an operator may drill three 

separate wells to different depths to tap these 

individual seams. The wells may be located within 

20 feet of each other, representing a pod of wells. 

PRAIRIE DOG COLONY COMPLEX. A group 

of prairie dog colonies distributed so that individual 

black-footed ferrets can migrate among them 

commonly and frequently. This distance has been 

determined to be 7 kilometers (4.4 miles). 

PRE-FLPMA LEASES. Oil and gas leases issued 

prior to the passage of the Federal Land Policy and 

Management Act of l976. Where occurring in 

Wilderness Study Areas, these leases have valid 

existing rights which allow development even if 

wilderness values may be impaired. 

PREVENTION OF SIGNIFICANT 

DETERIORATION OR PSD. A regulatory 

program under the Clean Air Act (Public Law 

84-159, as amended) to limit air quality degradation 

in areas currently achieving the National Ambient Air 

Quality Standards. The PSD program established air 

quality classes in which differing amounts of 

additional air pollution is allowed above a legally 

defined baseline level. Almost any additional air 

pollution would be considered significant in PSD 

Class I areas (certain large national parks and 

wilderness areas in existence on August 7, 1977, and 

specific Tribal lands redesignated since then). PSD 

Class II areas allow that deterioration associated with 

moderate, well-controlled growth (most of the 

country). 

Class I. An area that allows only minimal 

degradation above “baseline.” The Clean Air Act 

designated existing national parks over 

6,000 acres and national wilderness areas over 

5,000 acres in existence on August 7, 1977, as 

mandatory Federal Class I Areas. These areas 

also have special visibility protection. In 

addition, four tribal governments have 

redesignated their lands as Class I Areas. 

Class II. An area that allows moderate 

degradation above “baseline.” Most of the 

United States (outside nonattainment areas) is 

Class II. 

Class III. Any area that allows the maximum 

amount of degradation above “baseline.” 

Although the U.S. Congress allows air quality 

regulatory agencies to redesignate Class II lands 

to Class III, none have been designated. 

PRODUCED WATER. Water produced from oil 

and gas wells. 

RAPTOR. Bird of prey with sharp talons and 

strongly curved beaks (hawks, falcons, owls, and 

eagles). 

RECLAMATION. Rehabilitation of a disturbed area 

to make it acceptable for designated uses. This 

normally involves regrading, replacement of topsoil, 

revegetation, and other work necessary to restore it 

for use. 

RESERVE PIT. 

1. Usually an excavated pit that may be lined 

with plastic, that holds drill cuttings and waste 

mud. 

2. Term for the pit that holds the drilling mud. 

RIGHT-OF-WAY GRANT. A document 

authorizing a nonpossessory, nonexclusive right to 

use federal lands for the limited purpose of 

construction, operation, maintenance, and termination 

of a pipeline, road, or powerline. 

RILL. Small, conspicuous water channel or rivulet 

that concentrates runoff; usually less than 6 inches 

deep. 

RIPARIAN/WETLAND AREA. An area of land 

directly influenced by permanent water. It has visible 

vegetation or physical characteristics reflective of 

permanent water influence. Lakeshores, streams and 

permanent springs are typical riparian areas. 

 GLO-7
GLOSSARY 

Excluded are such sites as ephemeral streams or 

washes that do not exhibit the presence of vegetation 

dependent upon free water in the soil. 

ROAD. A vehicle route that has either been 

improved and maintained by mechanical means to 

ensure relatively regular and continuous use, or been 

established where vehicle travel has created two 

parallel tracks lacking vegetation. 

SALINITY. A measure of the salts dissolved in 

water. See alkalinity. 

SEDIMENT. Soil, rock particles and organic or 

other debris carried from one place to another by 

wind, water, gravity, ice, or other geologic agent. 

SEDIMENTARY ROCK. A layered rock resulting 

from the consolidation of sediment, such as shale, 

sandstone, and limestone. 

SEISMIC OPERATIONS. Use of explosive or 

mechanical thumpers to generate shock waves that 

can be read by special equipment to give clues to 

subsurface conditions. 

SENSITIVE SPECIES. Species designated by a 

State Director, usually in cooperation with the State 

agency responsible for managing the species and 

State Natural heritage programs, as sensitive. They 

are those species that: (1) could become endangered 

in or extirpated from a state, or within a significant 

portion of its distribution; (2) are under status review 

by the FWS and or NOAA Fisheries; (3) are 

undergoing significant current or predicted 

downward trends in habitat capability that would 

reduce a species’’ existing distribution; (4) are 

undergoing significant current or predicted 

downward trends in population or density such that 

federal listed, proposed, candidate, or State listed 

status may become necessary; (5) typically have 

small and widely dispersed populations; (6) inhabit 

ecological refugia or other specialized or unique 

habitats; or (7) are State listed but which may be 

better conserved through application of BLM 

sensitive species status. 

SERAL COMMUNITY. One of a series of plant 

communities that follow one another in time on any 

given area. 

SERAL STAGE. A potential plant community made 

up of a mix of trees and shrubs. 

SHALLOW COAL SEAM. Those coal seams that 

are too shallow to drill to directionally given the area 

geology and spacing limitations. 

SHEET EROSION. The detachment of soil material 

from the land surface by raindrop impact and its 

subsequent removal by runoff. 

SHUT IN. To close the valves on a well so it ceases 

production. 

SHRUB. A low, woody plant, usually with several 

stems; may provide food and/or cover for wildlife. 

SODIUM ABSORPTION RATIO. An expression 

of relative activity of sodium ions in exchange 

reactions with soil, indicating the sodium or alkali 

hazard to soil. It is a particularly important measure 

in waters used for irrigation purposes. 

SODIUM-AFFECTED SOIL. A nontechnical term 

for sodic soil (also called alkali soil) that contains 

sufficient sodium to interfere with the growth of most 

crop plants and in which the exchangeable sodium 

percentage is 15 or higher. It is also a generic way of 

describing nonsaline-alkali soil or saline-alkali soil. 

SOIL DEPTH CLASSES. Classes overlap from 0 to 

60 or more inches with specific depths as follows: 

very shallow 0-10 inches, shallow from 5-30 inches, 

moderately deep from 20-50 inches, deep from 

30-60 inches, and very deep from 50 to more than 

60 inches. 

SOIL SERIES. The lowest category of soil 

classification, being a subdivision of a family and 

consisting of soils which are essentially alike in all 

major profile characteristics except in the texture of 

the “A” horizon (or surface layer). 

SOIL SURVEY. The systematic examination, 

description, classification, and mapping of soils in an 

area, usually a county. Soil surveys are classified 

according to the level of detail of field examination. 

Order I is the most detailed, then Order II, on to 

Order V which is the least detailed. Most BLM soil 

surveys are Order II or III. 

SOLID WASTE. Any solid, semi-solid, liquid, or 

contained gaseous material that is intended for 

disposal. 

SOUR WELL. A condition caused by the presence 

of hydrogen sulfide in an oil or gas well. 

SPACING UNIT. The number of acres that one oil 

or gas well will efficiently drain. The Montana Oil 

and Gas Commission establishes the size of spacing 

units for each oil and gas field. 

 GLO-8
GLOSSARY 

SPECIAL STATUS SPECIES. Includes the 

following; (1) species that have been officially 

proposed for listing as threatened or endangered by 

the Secretary of the Interior, (2) species officially 

listed as threatened or endangered by the Secretary of 

the Interior under the provisions of the ESA, (3) 

species designated as candidates for listing as 

threatened or endangered by the FWS or NOAA 

Fisheries, (4) species listed by a State in a category 

implying but not limited to potential endangerment or 

extinction, (5) sensitive species as designated by a 

state director. 

SPECIES OF SPECIAL INTEREST OR 

CONCERN. Plant or animal species not yet listed as 

endangered or threatened but that are undergoing 

status review by a federal or state agency. This may 

include plant or animal species whose populations 

could become extinct by any major habitat change. A 

species that is particularly sensitive to some external 

disturbance factors. 

SPLIT ESTATE. Surface and minerals of a given 

area in different ownerships. Frequently, the surface 

is privately-owned while the minerals are federallyowned. 

SPUDDING. To begin drilling; to start the hole. 

STEEP SLOPE. Slope greater than 30 percent. 

STEP OUT WELL. A well drilled some distance 

from a proven well to determine the limits of the oil 

or gas reservoir. 

STIPULATION. A condition or requirement 

attached to a lease or contract, usually dealing with 

protection of the environment, or recovery of a 

mineral. 

STRUCTURAL IMPROVEMENTS. Improvements such as fences, reservoirs, springs, pipelines, 

waterspreaders, wells, water troughs, land treatments 

and instream structures. These improvements are for 

the livestock grazing, wildlife, recreation, watershed 

and soils programs. 

STRUTTING GROUND. An area used in the spring 

by sage grouse for courtship displays and breeding. 

Synonymous with the term “lek.” 

SUBBITUMINOUS. A black coal, intermediate in 

rank between lignite and bituminous coal. 

Distinguished from lignite by higher carbon and 

lower moisture content. 

SULFUR DIOXIDE OR SO2. A colorless gas 

formed when sulfur oxidizes, often as a result of 

burning trace amounts of sulfur in fossil fuels. 

SWEET WELL. An oil or gas well lacking any 

significant amounts of hydrogen sulfide. 

SYNCLINES. A downward, trough-shaped 

configuration of folded, stratified rocks. 

TERRACE DEPOSITS. A terrace is one of a series 

of level surfaces in a stream valley, flanking and 

more or less parallel to the stream channel. It is above 

the level of the stream, and represents the dissected 

remnants of an abandoned flood plain, stream bed, or 

valley floor produced during a former stage of 

erosion or deposition. 

TOTAL DISSOLVED SOLIDS (TDS). The dry 

weight of dissolved material, organic and inorganic, 

contained in water. 

TMDL (Total Maximum Daily Load). A TMDL is 

the total amount of a pollutant that a water body may 

receive from all sources without exceeding water 

quality standards. A TMDL can also be defined as a 

reduction in pollutant loading that results in meeting 

water quality standards. The TMDL process was 

established under Section 303(d) of the Clean Water 

Act. A TMDL includes both a waste load allocation, 

which focuses on point sources, and a load allocation, 

which addresses non-point sources. 

TRANSMISSION LINE. A large diameter pipeline 

through which oil or gas moves off lease after being 

sold. 

TURBIDITY. An interference to the passage of light 

through water due to insoluble particles of soil, 

organic material, micro-organisms, and other 

materials. 

UNDERGROUND INJECTION CONTROL 

PROGRAM. A program administered by the 

Environmental Protection Agency, primacy State, or 

Indian Tribe under the Safe Drinking Act to ensure 

that subsurface waste injection does not endanger 

underground sources of drinking water. 

UNDERSTORY VEGETATION. Plants, usually 

grasses, forbs, and low shrubs, growing beneath the 

canopy of other plants. 

UNITIZATION. Pooling of mineral acreages 

proposed by a company to facilitate the efficient 

development of a reservoir based on geology and 

reservoir characteristics of a producing formation or 

formations. 

 GLO-9
GLOSSARY 

UNNECESSARY OR UNDUE DEGRADATION. 

Conditions, activities, or practices that: 

(1) Fail to comply with one or more of the 

following: The performance standards in 

Sec. 3809.420 (43 CFR), the terms and 

conditions of an approved plan of 

operations, operations described in a 

complete notice, and other Federal and State 

laws related to environmental protection and 

protection of cultural resources; 

(2) Are not “reasonably incident” to 

prospecting, mining, or processing 

operations as defined in Sec. 3715.0-5 of 

this title; 

(3) Fail to attain a stated level of protection 

or reclamation required by specific laws in 

areas such as the California Desert 

Conservation Area, Wild and Scenic Rivers, 

BLM-administered portions of the National 

Wilderness System, and BLM-administered 

National Monuments and National 

Conservation Areas; or 

(4) Occur on mining claims or millsites 

located after October 21, 1976 (or on 

unclaimed lands) and result in substantial 

irreparable harm to significant scientific, 

cultural, or environmental resource values of 

the public lands that cannot be effectively 

mitigated. 

USABLE WATER. Those waters containing up to 

10,000 parts per million of total dissolved solids. 

VIEWSHED. Landscape that can be directly seen 

under favorable atmospheric conditions, from a 

viewpoint or along a transportation corridor. 

WATER QUALITY. The chemical, physical, and 

biological characteristics of water with respect to its 

suitability for a particular use. 

WATERSHED. All lands which are enclosed by a 

continuous hydrologic drainage divide and lie 

upslope from a specified point on a stream. 

WELL COMPLETION. See completion. 

WELL LIFE. For the purposes of this plan the well 

life is defined as from the time the well is drilled until 

the final abandonment of the well is approved. 

WETLANDS. Permanently wet or intermittently 

flooded areas where the water table (fresh, saline, or 

brackish) is at, near, or above the soil surface for 

extended intervals; where hydric wet soil conditions 

are normally exhibited, and where water depths 

generally do not exceed two meters. 

WILDCAT. A well drilled in an area where no oil or 

gas production exists. 

WILDCAT WELL. An exploratory well drilled in 

an area where there is no oil or gas production (see 

exploration well). 

WILDERNESS STUDY AREA (WSA). An area 

deter-mined to have wilderness characteristics. 

WSAs are submitted to the President and Congress 

for wilderness designation. These areas are an interim 

designation, valid until either designated as 

wilderness or released to multiple-use management. 

WORKOVER. To perform one or more remedial 

operation on a producing well to increase production. 

Deepening, plugging back, pulling, and resetting the 

liner are examples of workover operations. 

 GLO-10