NJ Well Driller flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Rotary air drilling

A drilling method that uses compressed air or air-foam to cool the bit and lift cuttings. It is suited to hard rock and fractured aquifers but needs a stable or cased hole above the water table.

Cable-tool drilling

A percussion method that breaks formation with a heavy bit on a cable and removes cuttings with a bailer. It handles boulders and unconsolidated gravel where circulation loss defeats rotary methods.

Annular velocity

The upward speed of drilling fluid in the space between the drill pipe and the borehole wall. It must exceed the settling velocity of the largest cuttings to keep the hole clean.

Lost circulation

The loss of drilling fluid into permeable or fractured formations. It reduces cuttings lift, lowers hole stability, and must be remedied with lost-circulation material or casing before drilling continues.

Down-the-hole hammer

A percussion tool driven by compressed air that strikes the bit directly in the hole. It is used for hard, abrasive rock and large-diameter holes where rotary bits wear quickly.

Grout volume calculation

Annular grout volume equals pi/4 times the difference between hole diameter squared and casing outside diameter squared, times the sealed length, plus a placement excess.

Neat cement grout

A mixture of Portland cement and clean water, commonly about 5 to 6 gallons per 94-pound sack. Bentonite may be added to reduce shrinkage and improve suspension.

Screen slot selection

The slot opening is chosen from sieve analysis of the formation sample so the screen retains roughly 40 to 50 percent of the aquifer material while allowing fines to pass during development.

Gravel pack gradation

The pack is sized at about 4 to 6 times the D50 of the formation, and the screen slot is sized to retain the pack. This stabilizes fine or uniform aquifers and improves well efficiency.

Sanitary well cap

A vermin-proof, vented cap that seals the top of the casing against surface water and debris. New Jersey requires a proper wellhead seal for a completed well.

Specific capacity

The pumping rate divided by drawdown in the well, usually expressed in gallons per minute per foot. It is a standard measure of well efficiency and is compared before and after rehabilitation.

Surge block development

A development technique that uses cyclic pressure reversals to pull fines and drilling fluid out of the screen and gravel pack. It is more effective than simple overpumping in screened wells.

Iron bacteria fouling

Biological growth that produces a reddish sheen, odor, and declining specific capacity. Shock chlorination followed by flushing is the usual first rehabilitation step.

Well rehabilitation

Mechanical and chemical treatment to restore specific capacity by removing scale, fines, and biological fouling. A follow-up pumping test verifies whether the well recovered.

Total dynamic head

The total energy the pump must supply: static lift plus drawdown plus discharge pressure head plus friction losses in the drop pipe, fittings, and distribution system.

Submersible pump setting

The pump is set below the expected pumping water level with margin for seasonal decline, yet above the screen. Incorrect setting causes cavitation or loss of prime.

Pressure tank precharge

The air charge in a bladder tank, set slightly below the pump cut-in pressure. A precharge lower than cut-in causes short cycling and premature pump and motor wear.

Friction loss

Pressure loss from water moving through pipe and fittings. It rises roughly with the square of flow, so undersized drop pipe sharply reduces delivered flow and increases energy use.

Transmissivity

Hydraulic conductivity multiplied by saturated aquifer thickness. It describes how much water an aquifer transmits through its full thickness and is estimated from pumping test data.

Specific yield

The drainable porosity of an unconfined aquifer, or the volume of water released per unit area per unit decline in water table. It is the storativity used in unconfined flow analysis.

Darcy's law

Flow rate equals hydraulic conductivity times cross-sectional area times hydraulic gradient. It is the basis for estimating groundwater flow and for interpreting aquifer tests.

Cone of depression

The drawdown surface around a pumping well. Its shape depends on pumping rate, transmissivity, and nearby boundaries such as streams, recharge areas, or impermeable layers.

Saltwater intrusion

Movement of saline water toward coastal wells caused by freshwater withdrawal. The Ghyben-Herzberg relation links freshwater head above sea level to the depth of the interface.

Coliform bacteria test

A required test for new and transferred private wells that indicates a pathway for contamination. A positive result triggers investigation, disinfection, and resampling rather than a health standard.

Nitrate MCL

The federal maximum contaminant level for nitrate is 10 mg/L as nitrogen. It is a health concern for infants, and reverse osmosis or ion exchange can remove it.

Arsenic treatment

Naturally occurring arsenic in New Jersey groundwater is removed by anion exchange, adsorptive media, or coagulation-filtration. Treatment selection depends on arsenic species and competing ions.

Well abandonment seal

The borehole is filled from bottom to land surface with approved cement or bentonite grout placed by tremie. Casing is removed or perforated so the seal is continuous.

Tremie placement

Placing grout from the bottom of the well upward through a pipe. It prevents bridging and voids that free-fall placement would create in a deep water column.

Bentonite chip seal

A sealant of bentonite pellets or chips placed in the annulus or borehole where they hydrate and swell. It is used where cement grout is impractical, with care to avoid bridging.

Well permit

A state authorization required before drilling a well. The licensed driller applies, and the permit number and construction details must appear on the filed well record.

Private Well Testing Act

A New Jersey law requiring testing of private wells at the time of sale or lease of property. The seller must test and provide results to the buyer.

Well record filing

The driller must submit a well log to the state within the required timeframe, including location, construction, grout volumes, yield, and water quality results.