IL Well Driller key terms

The gap between the outside of the well casing and the wall of the drilled borehole, running from the surface downward. It must be sealed with grout to stop surface water and shallow groundwater from moving down along the casing.

A cement-based or bentonite-based material placed in the annular space to form a permanent, low-permeability barrier. It prevents contamination from traveling down the outside of the casing and helps stabilize the borehole.

A mixture of Portland cement and clean water with no sand added, producing a dense slurry. It is a common approved sealing material because it bonds to both casing and soil and resists shrinkage better than clay slurries.

A swelling clay product used to make drilling mud and, in some applications, sealing slurries. When hydrated it forms a low-permeability gel, but it must be mixed and placed per code to serve as an effective seal.

A method of placing grout by pumping it through a pipe whose discharge end stays submerged in the rising grout column. It prevents voids and dilution by keeping grout from falling freely through water in the annular space.

The watertight connection at the top of the well where the casing, well cap, and pump wiring meet the surface. It blocks insects, surface water, and debris from entering the well opening.

The pipe installed in a borehole to keep the hole open and to separate the well interior from surrounding soil and water. It may be steel or plastic and must meet strength and wall-thickness requirements.

A slotted or perforated section of casing installed opposite a water-bearing formation. It holds back formation material while letting water enter the well, and its slot size is matched to the aquifer's grain size.

A graded bed of washed gravel or sand placed between the well screen and the formation or borehole wall. It filters out fine particles and improves flow into the well while reducing sand production.

The level at which water stands in a well when the pump is off and the water table has stabilized. It is measured from a fixed reference point and is used to plan pump depth and estimate available drawdown.

The water level in a well while it is being pumped at a steady rate, after the cone of depression has formed. The difference between this and the static level is the drawdown.

The drop in water level in a well caused by pumping, measured as the difference between static and pumping water levels. It reflects how much head the pump must overcome and how efficiently the aquifer yields water.

The pumping rate divided by the drawdown it produces, usually expressed in gallons per minute per foot. A higher value means the well yields more water for each foot of water-level decline.

A controlled pumping test that measures the rate and drawdown a new well can sustain. Results guide pump selection and confirm the well meets the water demand intended for its use.

The process of removing drilling mud, fines, and loose material from the screen and surrounding formation after drilling. It improves yield, stabilizes the borehole, and reduces sand and turbidity in the pumped water.

A development technique that forces water back and forth through the screen using a plunger or surge block. The surging loosens and flushes fine material from the gravel pack and formation so it can be pumped out.

A development method that injects compressed air into the well to lift water and fines out of the screen and gravel pack. Alternating air and water movement dislodges material and cleans the intake area.

Treating a new or repaired well with a strong chlorine solution to kill bacteria introduced during construction. The chlorinated water is held in contact with the well and then flushed out before use.

A group of indicator organisms whose presence in well water suggests contamination or a construction defect. A water sample is tested for them, and a positive result requires investigation and corrective action.

A water specimen collected from a well using clean, approved containers and proper technique for laboratory analysis. Careful collection and prompt delivery are needed so results reflect actual well conditions.

The required minimum horizontal separation between a well and a potential contamination source such as a septic system, animal lot, or fuel tank. The distance protects the well from nearby pollution.

Choosing the location for a well so it avoids flooding, contamination sources, and subsurface hazards while still providing adequate yield. Siting decisions must satisfy setback and access requirements.

A small-diameter exploratory boring drilled to learn about geology, water depth, and water quality before the final well is designed. It helps confirm that a site can supply the needed quantity and quality of water.

A saturated rock or sediment layer that can store and transmit enough water to supply a well. Its depth, thickness, and permeability determine how much water a well can produce.

A drilling method that turns a rotating bit while circulating drilling fluid to cut rock and carry cuttings to the surface. It is common for deep or large-capacity wells in consolidated formations.

A percussion method that repeatedly lifts and drops a heavy bit to break rock, with a bailer removing cuttings. It works well in unconsolidated formations and allows careful sampling of water-bearing zones.

A fluid mixture of water, clay, and additives circulated during drilling to cool the bit, carry cuttings, and hold the borehole wall open. Its properties must be controlled so it does not clog the producing formation.

A tight-fitting cover secured over the top of the casing to keep out rain, insects, and debris. It must allow pressure relief or venting while still maintaining a watertight seal.

A fitting that lets the pump discharge pipe pass through the casing below frost depth without a pit. It keeps the wellhead sealed and protects the water line from freezing and contamination.

A pump installed down inside the well below the pumping water level, with the motor sealed against water. It pushes water to the surface and is chosen for depth, flow rate, and power supply.

The required process of permanently decommissioning an unused well by sealing it so it cannot act as a pathway for contamination. It typically involves removing obstructions, filling with approved material, and sealing the top.

A well in which natural pressure raises water above the ground surface without pumping. It needs special controls to prevent uncontrolled discharge and to protect the aquifer from contamination.

A person who holds the state-issued credential authorizing them to construct, alter, or abandon water wells. Licensing requires meeting education, experience, and examination requirements and renewing on schedule.

The approval required before drilling or major alteration of a well begins. It records the proposed location, design, and intended use so the work can be inspected against code requirements.

The required record of a well's construction, including depth, casing, screen, grout, and water-bearing zones encountered. It is filed with the state and serves as a permanent reference for the site.

Training hours a licensed driller must complete during each renewal cycle to keep the license active. It keeps practitioners current on code changes, safety, and construction practices.