Some of the terms in this Glossary are borrowed with permission from the following sources:

  • GWW = Groundwater and Wells: Third Edition. 2007. Robert J. Sterrett (editor). Johnson Screens/a Weatherford Company. New Brighton, Minnesota. Glossary (Pp. 753-774)
  • NGWA Inc. = Illustrated Glossary of Driller’s Terms. 2004. National Ground Water Association Inc., Westerville, Ohio
  • ASTM D5092 = Standard Practice for Design and Installation of Ground Water Monitoring Wells. ASTM International, West Conshohocken, PA.
  • Gowen = Gowen Environmental Ltd. – Online Glossary
Any chemical compound containing hydrogen capable of being replaced by positive elements or radicals to form salts. In terms of the dissociation theory, it is a compound which, on dissociation in solution, yields excess hydrogen ions. Acids lower the pH. Examples of acids or acidic substances are hydrochloric acid, tannic acid, and sodium acid pyrophosphate.(GWW)
Granular mineral or rock material (e.g. sand, gravel) that is mixed with cement to form concrete.(Gowen)
Air Vacuum Value
A relief valve designed to allow air to enter into and vent from a water system at a high volume. When water encounters the valve, a weighted ball seals to a plate in the valve and creates a watertight seal.
Air Release Valve
A relief valve designed to allow gases (that build up in the water column) to slowly vent from the water column. When water encounters the valve, a weighted ball seals to a plate in the valve and creates a watertight seal.
Air Lift
To lift water or drilling fluid to the ground surface by pushing high velocity compressed air through the drilling stem.(GWW/NGWA)
Any of various soluble mineral salts found in natural water and arid soils having a pH greater than 7. In water analysis, it represents the carbonates, bicarbonates, hydroxides, and occasionally the borates, silicates, and phosphates in the water.(GWW)
An outdated term for a geologic layer of very low permeability located so that it forms an upper or lower boundary to a groundwater flow system. Aquitard or Confining Layer are preferred terms.(Gowen)
Aquifer Test
A test which involves adding to or discharging measured quantities of water from a well, and recording the resulting changes in head in the aquifer (during and after addition/withdrawal). Examples are slug tests, bail tests and pumping tests.(Gowen)
A geological formation that may contain groundwater but it is not capable of transmitting significant quantities of groundwater under normal hydraulic gradients (e.g. clay layers). In some situations aquitards may function as confining beds.(Gowen)
The condition of water in a confined aquifer being under sufficient pressure that the potentiometric surface is above the bottom of the overlying confining bed. The water level within a well in an artesian (or confined) aquifer rises to a point above the bottom of the confining bed that overlies the aquifer. It is not necessary for the water to flow at ground surface. If the water is under enough pressure, the potentiometric surface may be above the ground surface. In this case, water may actually flow from the well without pumping. Such a well is a flowing artesian well (or flowing well).(Gowen)
Artesian Aquifer
See Confined Aquifer
Material used temporarily during construction or permanently to replace material being removed.(Gowen)
Backwashing (Well Development)
A well development technique that uses surging or reversal of water flow in a well. The procedure removes fine material from the formation surrounding the well screen which can enhance well yield.
Unicellular microorganisms that exist as free living organisms or as parasites and have a broad range of biochemical, and often pathogenic, properties.(Gowen)
A substance that destroys bacteria.(Gowen)
To remove sediment, water, drill cuttings or other debris from a well or borehole with a bailer.(GWW/NGWA)
A cylinder (or tube) suspended from a cable or rope to remove sediment, drill cuttings, water or other material from a well. A bailer has an open top and a check valve at the bottom. Bailers such as dart valve or flapper valve bailers can be large and operated from a drilling rig. Other bailers used to sample water are small enough to be hand held.
Bail Test(Rising Head Test)
An aquifer test carried out to determine in-situ hydraulic conductivity by instantaneously removing a known volume of water from a well and measuring the resulting water level recovery in the well.(Gowen)
Ball Valve
A valve regulated by the position of a free-floating ball that moves in response to fluid or mechanical pressure.(Gowen)
Natural finely ground barium sulfate used for increasing the density of drilling fluids.(GWW)
Bentonite Granules And Chips
Irregularly shaped particles of bentonite (free from additives) that have been dried and separated into a specific size range.(ASTM D5092) For further information on bentonite see Table 2-1 of Chapter 2: Definitions & Clarifications.
Bentonite Pellets
Roughly spherical shaped or disc shaped units of compressed bentonite powder that may be coated with some chemicals.(ASTM D5092) For further information on bentonite see Table 2-1 of Chapter 2: Definitions & Clarifications.
Bit(Drill Bit)
The cutting tool attached to the base or bottom end of the drill string that breaks the formation into smaller pieces (cuttings) during drilling. Its design varies according to the type of formation and drilling equipment used.(GWW/NGWA)
An uncontrolled escape of drilling fluid, gas, oil or water from the well, caused by the formation pressure being greater than the hydrostatic head of the fluid in the hole.(GWW)
An open or uncased subsurface hole that is circular in plan view. The borehole is typically drilled, augered or bored into the earth.(ASTM D5092)
Breathing Well (Sucking & Blowing)
Conditions where the well and aquifer formation are significantly affected by changes in atmospheric pressure which can cause the periodic suction and expulsion of gases. Sucking and blowing (breathing) wells have been linked to the accumulation of gases low in oxygen in well pits leading to asphyxia.
Conditions where the well and aquifer formation are significantly affected by changes in atmospheric pressure which can cause the periodic suction and expulsion of gases. Sucking and blowing (breathing) wells have been linked to the accumulation of gases low in oxygen in well pits leading to asphyxia.(GWW/NGWA - modified)
Bulk Density
The amount of mass of a soil per unit volume of soil; where mass is measured after all water has been extracted and the total volume includes the volume of the soil itself and the volume of the air space (voids) between the soil grains.(Gowen)
Casing Driver
A device fitted to the tophead drive of a direct rotary rig’s mast. It allows the casing to be advanced during drilling but allows the drilling and driving to be adjusted independently.(GWW)
Casing Jacks
Hydraulic jacks used to pull casing or the drill stem from the well.(GWW/NGWA)
Casing Rotator
A device installed on a drilling rig that clamps around the casing. Once the rotator clamps onto the casing, the rotator can be rotated clockwise or counter clockwise into the ground. It also can adjust the distance between the casing and the drilling bit.(GWW)
Caving (Sloughing)
The inflow of unconsolidated material into a borehole that occurs when the borehole walls lose their cohesiveness.(ASTM D5092)
A phenomena of cavity formation, or formation and collapse, especially in regard to pumps, when the absolute pressure within the water reaches the vapour pressure, causing the formation of vapour pockets.(GWW)
(Portland Cement) – A mixture that consists of calcareous, argillaceous, or other silica, alumina-, and iron-oxide-bearing materials that is manufactured and formulated to produce various types which are defined in Specification ASTM standard C 150 Specification for Portland Cement.(ASTM D5092)
A device that assists in the centering of a casing or well screen within a borehole or another casing.(ASTM D5092)
Centrifugal Pump
A pumping mechanism that spins water by means of an “impeller”. Water is pushed out by centrifugal force. Centrifugal deep-well jet pumps work with two lines into the well. As water is moved at the surface by an impeller, some of the water is returned to the well to the ejector assembly above the intake. This return water creates a “venturi” effect in the ejector, sucking well water through the check valve.
Check Valve
A mechanical device which normally allows a fluid or gas to flow through it in only one direction. There are various types of check valves for various needs. Check valves typically work automatically. An important concept in a check valve is the cracking pressure which is the minimum upstream pressure at which the valve will operate. Thus, the check valve is designed for a specific cracking pressure.
A length of extremely heavy steel tube used in well drilling. It is placed in the drill string immediately above the drill bit to minimize bending, maintain plumbness, and provide weight on the drill bit while drilling.(GWW/NGWA)
Cone Of Depression
The area around a discharging well where the hydraulic head (potentiometric surface) in the aquifer has been lowered by the pumping. In an unconfined aquifer, the cone of depression is a cone-shaped depression in the water table where the formation has actually been dewatered.(Gowen)
Confined Aquifer (Artesian Aquifer)
A fully saturated aquifer overlain by a confining layer. The potentiometric surface (hydraulic head) of the water in a confined aquifer is at an elevation that is equal to or higher than the base of the overlying confining layer. Discharging wells in a confined aquifer lower the potentiometric surface which forms a cone of depression, but the saturated formation is not dewatered.(Gowen)
Confining Bed(Unit)
A geologic bed of impermeable (or very low permeable) material stratigraphically adjacent to one or more aquifers. Confining bed is commonly used to replace terms such as aquiclude, aquitard and aquifuge.(Gowen)
Confining Layer
A geologic body of low hydraulic conductivity above or below one or more aquifers. Confining layer is commonly used to replace the term aquiclude.(Gowen)
Consolidated Formations
Geologic formations of natural material that has been lithified. The lithification creates a material with high strength and resistance to disintegration.(Gowen)
The act or process of dissolving or wearing away metals.(GWW)
Cuttings (Drill Cuttings)
Fragments of soil or rock created by the drilling process with or without a drilling fluid (e.g. water).(Gowen)
The amount of mass per unit volume.(Gowen)
Removing or draining water to lower the water table or potentiometric surface (e.g. by pumping a well or letting groundwater flow from a flowing well). Dewatering is commonly done during construction activities and to keep underground structures dry.
Discharge Area
An area in which there is upward groundwater flow in the subsurface. Groundwater flows toward the surface in a discharge area and may escape as a spring, seep or baseflow. A discharge area can also be an area where water, heavily chlorinated water or other material is discharged from a well.(Gowen)
A downward hydrologic slope that causes groundwater to move toward lower elevations. Wells downgradient of a source of contamination are prone to receiving the contaminant’s parameters at elevated concentrations.(Gowen)
A lowering of the water table in an unconfined aquifer or the potentiometic surface of a confined aquifer caused by the pumping of groundwater from a well.(Gowen) The difference between the static water level (SWL) and the pumping water level (PWL) in a well. Drawdown = PWLSWL.
Drill Bit
See Bit.
Drill Collar
See Collar.
Drill Cutting
See Cuttings.
Drill Hole
See borehole.
Drill Rod (Pipe)
Special hollow jointed or coupled rods (pipes) that are used in creating a drill string from the rotating mechanism (typically with the drilling rig) to the bit.(Gowen)
Drill String
The string includes the drill rods (pipes) attached from the rotating mechanism to the collar, the collar and the bit. The drill string is used to transmit rotation from the rotating mechanism (typically with the drilling rig) to the bit. The drill string conveys air or drilling fluid which removes cuttings from the borehole and cools the bit.
Drilling Fluid
A water, bentonite-water or air-based fluid used in well drilling to remove cuttings from the hole, to clean and cool the bit, to reduce friction between the drill string and the sides of the hole, and to seal the borehole. When a bentonite-water mixture is used it is sometimes called mud or drilling mud.
Drive Shoe
A forged steel collar on the bottom of a casing. The collar has a cutting edge to shear off irregularities in the hole as it advances. A drive shoe is considered casing and is used to form a seal between the casing and the bedrock.(Gowen)
Drop Pipe
The pipe (riser pipe or waterline) that carries water from a pump in a well (or from a foot valve) up to the surface through the top of the well or to a pitless adapter. The drop pipe is considered to be part of a pump as defined by the Wells Regulation.
Dry Weight
The weight of a sample based on % solids. The weight after drying in an oven.(Gowen)
Dual Porosity
A subsurface formation in which groundwater flow occurs through fractures and through pore space. For example, in a fractured till, groundwater can flow through the fractures and through the pore space among the till particles.(Gowen)
Effective Hydraulic Diameter
The area in which water from the aquifer can move freely into a well. If a well is completed with a well screen and surrounded by filter pack material, the effective hydraulic diameter is equal to the diameter of the borehole.
Effective Porosity
The amount of interconnected pore space through which fluids can pass. Effective porosity is usually less than total porosity because some pores may be occupied by static fluid.(Gowen)
Condition that exists in a system when the system does not undergo any change of properties with the passage of time. Typically multiple forces produce a steady state (balance) resulting in no change over time.(Gowen)
The general process whereby the materials of the earth’s crust are moved from one place to another by running water (including rainfall), waves and currents, glacier ice, or wind.(Gowen)
Filter Pack

A filter pack is a well sorted gravel or coarse sand that can be:

  • Developed around the well screen (naturally developed from native granular material);
  • Selected and placed into the hole surrounding the well screen and developed (artificial filter pack), or
  • Pre-packed between two manufactured well screens (called “pre-packed well screens”) and developed.

This “packed” zone separates the well screen from the natural aquifer material to prevent finer materials from entering the well and increases the effective well diameter. The filter pack should extend several metres above the top of the screen to allow for settling during development.

Retrieving a lost object in a well.
Flowing (Active) Sand
A saturated sand deposit that flows upward into a well. Flowing sand problems typically occur during well construction when the hole reaches the saturated sand deposit. Flowing sand is also known in the industry as “running sand” or “active sand”.
Flowing Artesian Well
A flowing well (see flowing well and static water level in Table 2-1 in Chapter 2: Definitions & Clarifications)
Flush-Mounted Well Pit(Vault)
An enclosure for the top of a test hole or dewatering well that is flush with the ground surface. This enclosure is a type of well pit.
A mappable body of bedrock or overburden material that is recognizable by its physical and mineralogical characteristics and by its location within the geological time record (see subsurface formation in Chapter 2: Definitions & Clarifications, Table 2-1)
Formation Stabilizer
Sand or gravel placed in the annular space of the well to provide temporary to long-term support for suitable sealant in the annular space of a well.
Voids in bedrock or overburden (e.g. till or clay) as a result of structural stresses (e.g. folding or faulting).
A state of a colloidal suspension in which shearing stresses below a certain finite value fail to produce permanent deformation. Gels commonly occur when the dispersed colloidal particles have a great affinity for the base fluid.(GWW)
Gel Strength
The thixotropic (i.e. fluid when mixed that gels when left to stand) property of a drilling fluid that allows it to form a gel when it stops moving.(GWW/NGWA)
Geological Log
See Log of Overburden and Bedrock materials in Table 2-3 in Chapter 2: Definitions & Clarifications.
An engineering term pertaining to a soil or an unconsolidated sediment consisting of particles of several or many sizes. The material can be described as well graded or poorly graded.(GWW)
The rate of change in value of a physical or chemical parameter per unit change in position.(GWW/NGWA)
Grain Size
General dimensions of sediment or rock particles.(GWW/NGWA)
Gravel Pack
See filter pack
Underground water that fills pores in soils or openings in bedrock to the point of saturation.(Gowen)
Groundwater Divide
The rather vague division between groundwater basins.(Gowen)
Groundwater Flow
The movement of groundwater through openings in overburden and bedrock.(Gowen)
Groundwater Mining
The permanent depletion of groundwater resources.(Gowen)
Groundwater Recharge (Catchment) Area
An area that contributes to the natural replenishment (recharge) of the groundwater. It may include localized discharge areas. It typically includes the infiltration of precipitation and its movement through pores and fractures to the groundwater.(Gowen)
Groundwater Table
The surface between the zone of saturation and the zone of aeration and includes the surface of an unconfined aquifer.(Gowen)
A fluid mixture of cement or bentonite with water of a consistency that can be forced through a pipe and placed as required.(GWW) It can be a suitable sealant or an abandonment barrier material if it meets the requirements of the Wells Regulation.
The operation by which a sealant is placed in a well’s annular space or abandonment barrier is placed in an abandoned well including its annular space.
A property of water causing the formation of an insoluble residue when the water is used with soap. It is primarily caused by calcium and magnesium ions.(GWW)
Head(Hydraulic Head)
The energy contained in a mass of water that is produced by elevation, pressure, or velocity.(GWW)
Head Loss
That part of head energy which is lost because of friction as water flows.(GWW)
Nonuniform in structure of composition throughout.(GWW)
Hole Stabilizer
A steel casing, a concrete tile, other temporary structure or drilling fluid (mud) which prevents the formation from collapsing into the well during well construction.
Uniform in structure or composition throughout.(GWW)
The act by which a substance takes up water by absorption and/or adsorption.
Hydraulic Conductivity
A measure of the ability of a fluid to flow through a porous medium determined by the size and shape of the pore spaces or fractures in the formation and their degree of interconnection and also by the viscosity of the fluid.
Hydraulic Gradient
The slope of the groundwater level or water table. It is the driving force of fluid flow in a porous medium. The hydraulic gradient indicates which direction groundwater will flow and how rapidly.
See Hydrofracturing
Hydrofracturing (Hydraulic Fracturing)
The process whereby water is pumped under high pressure into a bedrock well to fracture and clean out the reservoir rock surrounding the well bore. It is used in an attempt to increase the yield of low producing water wells in bedrock where joint systems or fractures are poorly developed. It is also used in well development immediately after new well construction.
A person who specializes in hydrogeology and is a Professional Engineer or a Professional Geoscientist.
A of geology dealing with the study of groundwater, with particular emphasis on the chemistry and movement of water.
Hydrologic Cycle
The continued circulation of water between the ocean, atmosphere and land.
Watertight, or not capable of being penetrated, as in the case of rock or soil not allowing the passage of water.
Impermeable Layer
Layer of solid material, such as rock or clay, which does not allow water to easily pass through
Inertial Lift Pump
A manual well pump with a one-way foot valve typically attached to polyethylene tubing. This pump operates by moving the top of the tube up and down. This type of pump is commonly used in monitoring wells to sample the well water.
Flow of water from the land surface into the subsurface. The movement of water (typically from precipitation), or other liquid down through pores or fractures in soil and bedrock.
In Situ
In its original place; unmoved; unexcavated; remaining in the subsurface.
The condition occurring when the cone (area) of influence of a water well comes into contact with or overlaps that of a neighbouring well that are both pumping from the same aquifer or are located near each other. In some cases the pumping causes a well to go dry.
Propulsion of water under high pressure into sandy aquifers to create a hole for the installation of a driven-point well.
Hollow steel bar that is the main section of drill string to which the power is directly transmitted from the rotary table of a drilling rig to rotate the drill pipe and bit or to rotate the bucket on a boring rig.
A threaded metal device covered in neoprene, or other type of rubber, that is used to connect the top of the well screen to near the bottom of the casing. The device can be used to seal the annular space between two casings or between a casing and the open borehole. A k-packer can be considered a suitable sealant in some cases.
Larminar Flow
Water flow in which the stream lines remain distinct and in which the flow direction at every point remains unchanged with time. It is characteristic of the movement of groundwater through a well screen.
The flow of water from one hydrogeologic unit to another. It may be natural or through a structure like a well or other preferential pathway.
Lower Explosive Limit (LEL)
The concentration of a gas in air above which the concentration of vapours is sufficient to support an explosion.
Lost Circulation
The result of drilling fluid escaping from the borehole into the formation by way of pores or fractures in the formation.
Naturally Developed Well
A well in which the well screen is placed in direct contact with the aquifer materials and developed such that the fine native material is drawn through the well screen and the coarse material is graded against the outside of the screen forming a natural filter pack.
Used to describe standard sizes for pipe from 3.2 mm to 305 mm (1/8 inch to 12 inches). The nominal size is specified on the basis of the inside diameter. Depending on the wall thickness, the inside diameter may be less than or greater than the number indicated.
Oxidation - Reduction (Redox)
A chemical reaction consisting of two half reactions. They are an oxidation reaction in which a substance loses (or donates) electrons and a reduction reaction in which a substance gains (or accepts) electrons.
Partial Penetraion
A condition where the intake portion of the well is less than the full thickness of the aquifer.
A tightly fitting device placed in a well to isolate or seal a portion of a well. Packers can be installed in pairs to seal the section of a well between two packers. In some cases only one packer will be placed to isolate the section of the well between the packer and the bottom of the well.
A disease causing microbial agent. Generally, any bacteria, viruses, protozoans or fungi that can cause disease in humans, plants or animals.
Peak Water Demand
The highest rate of water use each day. Well capacities or storage facilities should be designed to meet this demand.
Perched Aquifer
It is considered a special case of an unconfined aquifer. It can occur wherever an impervious (or semi-impervious) layer of limited aerial extent is located between the regional water table of an unconfined aquifer and the ground surface.
Perched Groundwater
Unconfined groundwater separated from an underlying main body of groundwater by a confining layer.
See Infiltration
Slits cut into the well casing to form a well screen allowing groundwater to enter the well. They may be located at more than one level, to coincide with water-bearing strata in the earth.
The ability of an aquifer or water-bearing formation to allow water to pass through it; the capacity of an aquifer to permit the movement of water. It is also a measure of how easily water flows through a material. Often used as a synonym for hydraulic conductivity.
A measure of the relative acidity or alkalinity of water. A pH of 7 is neutral. Values less than 7 are acidic and greater than 7 are basic (alkaline).
Piezometric Surface
See Potentiometric Surface.
Pitless Adapter
A metallic (usually brass) fitting that is attached to the casing below the frost line to connect the in-well drop pipe (waterline) to the buried horizontal pipe (waterline) leading to point of use. If properly installed, the connection will be watertight to the casing. It allows the pipe to pass horizontally through the casing so that no pipe is exposed above ground where it could freeze. The device is designed to replace the need for well pits and pump houses.
A substance formed by the union of two or more molecules of the same kind linked end to end into another compound having the same elements in the same proportion but a higher molecular weight and different physical properties.
Pore Space
Small openings in a formation filled with air or water.
The ratio of voids or porous openings in overburden or bedrock to the total volume of the overburden and bedrock.
Potentiometric Surface
A surface that represents the level to which groundwater in a confined aquifer would rise in a well when encountering the aquifer. If the hydraulic head varies significantly with depth in the aquifer, then there may be more than one potentiometric surface. The water table can be considered to be the potentiometric surface for an unconfined aquifer.
Pressure Grouting
A process by which grout is confined within the hole or casing by the use of retaining plugs in packers, and by which sufficient pressure is applied to drive the grout slurry into the annular space or zone to be grouted.
Pressure Head
The height of a column of static fluid (water) which is necessary to develop a specific pressure.(Gowen)
Preofessional Engineer
An Engineer in good standing licensed pursuant to the Professional Engineers Act, R.S.O. 1990, c. P.28.
Professional Geoscientist
A Geoscientist in good standing registered pursuant to the Professional Geoscientists Act, 2000, S.O. 2000, c. 13.
Pumping Test
An aquifer test that is conducted to determine aquifer or well characteristics.
Pumping Water Level
An aquifer test that is conducted to determine aquifer or well characteristics.
Radius Of Influence
The distance from the centre of a well to the outermost point of the cone of depression where the drawdown approaches zero.
Raw Water
Surface or groundwater that is available as a source of drinking water but has not received any treatment.
The process by which an aquifer is replenished with water. This can also mean the quantity of water infiltrating from the surface and percolating to aquifers
Recharge Area
An area in an aquifer where there are downward components of hydraulic head. In this area, infiltration travels downward into the deeper sections of the aquifer.
Reciprocating Pump
A pump where the motor sitting above the well moves a piston up and down inside a cylinder in the well casing. On the upstroke, water is pulled into the pipe. A check valve at the foot of the pipe prevents water from flowing out of the pipe on the downstroke. It works the same way as a hand pump.
Recovery Rate
Rate at which the groundwater level rises in the well after pumping stops.
Residual Drawdown
The difference between the original static water level and the depth to the water level in a well at a given instant during the recovery period.
The pipe extending from the slots in the well screen to the well casing in a telescopic well screen. It is also sometimes referred to as the well casing or the drop pipe.
Safety Rope
Nylon rope used to secure the pump in case of pipe breakage.
Sampling And Analysis Plan
As part of the Records of Site Condition Regulation, this plan is created by a qualified person when planning for the site investigation component of a phase 2 environmental site assessment and includes a quality assurance and quality control program, data quality objectives, standard operating procedures and a description of any physical impediments that interfere with or limit the ability to conduct sampling and analysis.
Pores in a medium filled with water.
Saturated Zone
The zone below and including the water table in which all pore spaces or fissures are totally filled with water. Also referred to as the phreatic zone.
see Shear Strength and Shear Stress
Shear Strength
The maximum resistance of a soil or rock to shearing stresses. It can also refer to the measure of shear or gel properties of a drilling fluid or grout.
Shear Stress
The component of stress which acts tangential to a plane through any given point in a body.
Shore Well
A hole in the ground located at or near the shore or bank of any surface water that is designed to take water only from surface water sources such as a lake or river. For further clarification, a hole is not considered a well as long as the hole does not encounter groundwater and is not subject to the requirements of the Wells Regulation or the licensing requirements in the Ontario Water Resources Act. Some holes close to surface water features which may have been designed to take surface water may also take groundwater. In this case the hole is considered a well under the Ontario Water Resources Act and the Wells Regulation requires the well owner to prevent the entry of surface water from entering the well.
Sieve Analysis
Determination of the particle-size distribution of a soil, sediment, or rock by measuring the percentage of the particles that will pass through standard sieves of various sizes.
Slug Test
A test carried out to determine in situ hydraulic conductivity by instantaneously adding a known water quantity (or solid object of known displacement) to a well and measuring the resulting recovery of the water level. Also known as a falling head test.
Specific Capacity
The yield of water per unit (metre or foot) of drawdown while pumping the well. Typically, specific capacity will decrease as pumping time or the pumping rate increase.
Specific Gravity
The weight of a particular volume of any substance compared to the weight of an equal volume of water at a reference temperature.
Specific Storage
The quantity of water released from or taken into storage per unit volume of a porous medium per unit change in head.
Specific Yield
The ratio of the volume of yield of water by gravity drainage from bedrock or overburden (after being saturated) to the volume of the bedrock or overburden.
A natural groundwater discharge on the land where the water table is higher than the ground surface. Pressure forces the water out of the land at a weak point, which creates the spring. For further clarification, if works are constructed around a spring or if equipment is installed for the collection or transmission of water, and the water is likely to be used for human consumption, then the spring is considered a well.
Standard Operating Procedures

as part of the Records of Site Condition Regulation, these procedures are developed by a qualified person when any of the following field investigation methods are used in the field investigation component of a phase 2 environmental site assessment:

  • borehole drilling;
  • excavating;
  • soil sampling;
  • field screening measurements, including calibration pridcedures;
  • monitoring well installation;
  • monitoring well development;
  • field measurement of water quality indicators, including calibration precedures;
  • sediment sampling, and
  • groundwater sampling.
Layers of deposited rock, overburden, etc. which are distinguishable from each other.
Submersible Pump
Submersible pumps are long, narrow pumps that fit into the well and sit below the water level. They are connected to the surface by a plastic or steel pipe and a waterproof electrical cable. The water flow in the well provides cooling for the motor.
Surface Water
Water that is on the earth’s surface, such as streams, rivers, lakes or reservoirs.
A substance capable of reducing the surface tension of a liquid in which it is dissolved. Used in air-based drilling fluids to produce foam, and during well development to disaggregate clays.
Surge Block
See Surging
Development technique used with cable tool and rotary drills utilizing a surge block. A surge block consists of two or more rubber disks sandwiched between steel plates. Up and down movement of the surge block in the well forces water to flow into and out of formation
Sustained Yield
The rate at which groundwater can be withdrawn from an aquifer without long term depletion of the supply.
See Collar
Tensile Strength
The resistance of a material to a force tending to tear it apart.
Total Dissolved Solids (TDS)
Term that expresses the quantity (mass) of dissolved material in a sample of water typically expressed in milligrams per litre.
The rate at which groundwater can flow through an aquifer section of unit width under a unit hydraulic gradient. It is the average permeability of a section of the entire aquifer at a given location multiplied by the thickness of the formation.
Unconfined Aquifer (Water Table Aquifer)
An aquifer confined only by the lower impermeable layer. Water usually saturates only part of the geologic unit and there is no upper confining layer. In an unconfined aquifer the water table is exposed to the atmosphere through openings in the overlying materials. In an unconfined aquifer, the cone of depression is a cone-shaped depression in the water table where the formation has actually been dewatered.
Unconsolidated Formations
Formations of materials that are loose (not lithified), such as sand, gravel, silt and clay.
A wing on a drill bit that can allow a drill bit to swing out into the formation below the casing during drilling and retract into the casing when drilling is completed.(GWW)
Pores containing air or a mixture of air and water.
Unsaturated Zone
The zone above the water table in which soil pores or fissures are less than totally saturated. It is also called the vadose zone or the zone of aeration.
An upward hydrologic slope. Wells that are upgradient of a source of contamination are less prone to receive the contaminants at elevated concentrations.
The property of a substance to offer internal resistance to flow. Specifically, the ratio of the shear stress to the rate of shear strain.
Water Table
The top of the zone of saturation where the surface is not formed by a confining unit.
Water Table Aquifer
See Unconfined Aquifer
The visible part of the well above the ground surface or above a floor.