MD Well Driller key terms

A saturated geologic formation of sand, gravel, or rock that holds and transmits enough groundwater to supply a well. Its permeability and yield determine how much water a completed well can reliably produce.

A low-permeability bed of clay or dense rock that restricts water movement between aquifers. It separates shallow and deep water-bearing zones and influences whether a well is completed in confined or unconfined conditions.

A well that penetrates a confined aquifer in which water rises above the top of the aquifer under its own pressure. If pressure is sufficient, water may flow at the surface without pumping.

The level at which water stands in a well when it is not being pumped or disturbed. It is measured from a fixed reference point and is used to track seasonal and long-term aquifer changes.

The stabilized water level in a well while it is being pumped at a constant rate. The difference between it and the static level is the drawdown, which indicates how the well and aquifer respond to withdrawal.

The drop in water level inside a well caused by pumping, measured as the difference between static and pumping levels. Excessive drawdown can expose the pump intake and reduce yield.

The yield of a well expressed in gallons per minute per foot of drawdown under stabilized pumping conditions. It is a practical indicator of well efficiency and aquifer productivity.

The pipe installed in a borehole to keep the hole open, prevent collapse, and seal out unwanted water and contamination. Casing material and wall thickness must suit the depth and intended use.

A slotted or perforated section installed at the producing zone that admits water while holding back formation material. Slot size is matched to the aquifer grain size to limit sand entry.

A graded filter of washed gravel or sand placed around a well screen to improve flow and block fine formation particles. Its gradation is designed relative to the aquifer material it surrounds.

The gap between the borehole wall and the outside of the casing. It must be sealed with grout to prevent surface water and shallow contamination from moving down along the casing.

A cement-based or bentonite slurry placed in the annular space to form a permanent, low-permeability seal. Proper placement and volume are critical to protecting groundwater from contamination.

The grouted and capped connection at the top of a well that blocks surface water, insects, and debris from entering. It typically includes a watertight cap and a seal extending below frost depth.

Measures taken at and around the top of a well to prevent contamination from entering the water supply. These include a proper cap, graded drainage away from the casing, and control of nearby land use.

The minimum required horizontal distance between a well and a potential contamination source such as a septic system, animal lot, or fuel tank. Distances are set by regulation and vary by feature type.

A drilling method in which a rotating bit cuts the formation while drilling fluid circulates to remove cuttings and cool the bit. It is the most common technique for deep and large-diameter water wells.

A rotary method that uses a circulating bentonite or polymer slurry to lift cuttings and stabilize the borehole wall. The mud also forms a filter cake that must be removed during development.

A rotary method in which compressed air, often with foam, carries cuttings to the surface instead of liquid mud. It is well suited to hard rock and provides fast, clean samples.

Liquid or air circulated down the drill string to remove cuttings, cool the bit, and maintain borehole stability. Its density and viscosity must be controlled to avoid formation damage.

Rock and soil fragments carried to the surface by the drilling fluid during rotary drilling. Their character and depth of return help the driller identify formations and set casing or screen intervals.

A written record of the materials, depths, water levels, and construction details encountered while drilling. It documents the well as built and supports later decisions about screen placement and pump setting.

A percussion method that breaks rock with a heavy bit repeatedly dropped on a cable, with cuttings removed by a bailer. It is slower than rotary but effective in boulder formations.

A layer of fine solids deposited on the borehole wall by drilling mud. It helps stabilize the hole but can clog the formation and must be removed to restore flow.

The process of removing drilling mud, fines, and loose material from the aquifer around the screen to improve flow. Methods include surging, jetting, and air lifting until discharge runs clear.

A development technique that repeatedly forces water in and out of the screen to loosen and flush fine particles. It is used with care to avoid damaging the formation or the screen.

The movement of fine formation particles into a well, causing cloudy water and possible pump wear. It may indicate an undersized screen, a poor gravel pack, or incomplete development.

A controlled pumping test that measures a well's flow rate and drawdown over time to estimate sustainable capacity. Results guide pump sizing and pump setting depth.

The depth at which a submersible pump is placed in a well, chosen to stay submerged during pumping drawdown. Setting it too shallow risks running dry; too deep may waste capacity and complicate service.

Treating a completed well with a chlorine solution to kill bacteria introduced during construction. The solution is held in contact for a specified period, then flushed before sampling.

A group of indicator organisms used to assess bacterial contamination of well water. Their presence suggests a pathway for surface contamination or a defect in the well seal.

Collecting a representative water specimen from a well under controlled conditions for laboratory analysis. Proper technique and the right sample container are needed to avoid false results.

The Maryland credential required of a person or business that drills, constructs, or repairs water wells. Work must be performed under the license, and the holder is responsible for compliance.

The approval a property owner must obtain from the appropriate Maryland authority before drilling or altering a well. The permit sets conditions the driller must follow during construction.

The record filed after a well is finished, describing its location, depth, construction, and yield. It becomes part of the permanent record and is required by the regulatory authority.

A well no longer in use that must be properly sealed to prevent contamination and physical hazard. Maryland rules require filling and sealing with approved materials by qualified personnel.

A regulatory minimum distance between a well and a contamination source or property feature. The driller must verify setback compliance before construction begins.