GA Well Driller flashcards
GA Well Driller · Build recall with a focused review session.
32 cards. Read the term and the definition here. The deck at the top of this page is optional.
- Specific capacity
- Pumping rate divided by drawdown, usually in gallons per minute per foot. It measures well efficiency and declines if the screen or formation plugs with fines.
- Potentiometric surface
- The imaginary level to which water in a confined aquifer would rise under its own pressure. Where it stands above land surface, a flowing artesian well results.
- Cone of influence
- The area around a pumping well where the water level is lowered. Its radius grows with pumping time and transmissivity and shrinks with higher storativity.
- Fractured crystalline bedrock
- Georgia Piedmont aquifer type in which water is stored in and transmitted through fractures and faults. A borehole that misses fractures will produce little or no water.
- Gravel pack
- A sorted sand or gravel envelope placed around a well screen, typically 3 to 5 inches thick, to stabilize the formation and improve yield while blocking fine sediment.
- Sanitary seal
- A watertight seal at the wellhead around the pump pipe and casing that prevents surface water, insects, and debris from entering the well.
- Screen slot size
- The width of the openings in a well screen, chosen to retain most of the formation sand. Typical Coastal Plain values are 0.010 to 0.040 inch.
- Mud rotary drilling
- A method that circulates bentonite-based fluid down the drill pipe and up the annulus to remove cuttings and hold the borehole wall open in unstable formations.
- Cable tool drilling
- A percussion method in which a heavy bit is repeatedly lifted and dropped to break rock; cuttings are removed with a bailer. It uses no drilling mud.
- Lost circulation
- The escape of drilling fluid into a permeable or fractured formation, so that returns to the surface stop. It is treated with cement, lost-circulation material, or air drilling.
- Neat cement grout
- A mixture of Portland cement and water at no more than about 6 gallons per 94-pound sack. Excess water causes shrinkage and cracking of the seal.
- Tremie placement
- Pumping grout down a pipe to the bottom of the annular space so the grout rises from below. This avoids bridging and voids that occur with free-fall placement.
- Annular seal
- The continuous grout column between the casing and the borehole wall, extending from the bottom of the casing to land surface, that blocks contamination movement.
- Casing centralizer
- A device attached to the casing to hold it centered in the borehole so the grout envelope is uniform and no unsealed channel forms along the wall.
- Well development
- Removal of drilling fluid, filter cake, and fine sediment from the formation around the screen, using surging, jetting, bailing, or air lifting until discharge runs clear.
- Step-drawdown test
- A pumping test run at three or more increasing rates to separate aquifer loss from well loss and to estimate well efficiency.
- Well disinfection
- Treatment of a new or repaired well with a chlorine solution of about 50 to 100 mg/L for at least 12 hours, followed by pumping to waste.
- Constant-rate pumping test
- A test that pumps a well at a steady rate, usually 24 hours or more, while measuring drawdown and recovery to estimate transmissivity and storativity.
- Pressure tank precharge
- The air pressure in a bladder tank, set about 2 psi below the pump cut-in pressure. Loss of precharge causes waterlogging and rapid pump cycling.
- Jet pump suction limit
- A shallow-well jet pump can lift water only about 25 feet at sea level because atmospheric pressure limits the suction. Deeper wells need a submersible or deep-well jet.
- Pump operating point
- The intersection of the pump performance curve and the system head curve. It defines the actual flow and head at which the pump will run.
- Drawdown volume
- The water a pressure tank can supply between cut-in and cut-out, roughly 25 percent of nominal tank volume for a bladder tank. It sets pump cycle length.
- Well abandonment seal
- A continuous grout or cement column filling the borehole from bottom to land surface, with the top 20 feet sealed in cement and the casing cut off.
- Flowing artesian well
- A well in which the confined aquifer pressure raises water above land surface. It must be controlled during drilling and sealed during abandonment to prevent cross-aquifer flow.
- Abandonment record
- A filed report giving the well location, depth, method, and sealing materials used. Georgia requires it to be submitted to the EPD after the work is complete.
- Georgia EPD
- The Environmental Protection Division of the Georgia Department of Natural Resources, which administers the state water well standards and licenses well contractors.
- Well contractor license
- A credential issued by the Georgia EPD that is required before a person may construct, repair, or abandon a water well in the state.
- Well log filing
- The driller's record of depth, casing, screen, grout, and water levels, which must be submitted to the Georgia EPD within the required period after completion.
- Fifty-foot setback
- The minimum separation in Georgia between a water well and a septic tank or sewage disposal area, intended to keep contamination from reaching the well.
- Call 811 before drilling
- The utility locate request made before excavation. It marks buried gas, electric, and communications lines and prevents struck-line injuries on the drill site.
- Hydrogen sulfide hazard
- A toxic gas found in some wells and pits that deadens smell above low concentrations and is lethal at about 100 ppm. Atmospheric testing is required before entry.
- Drilling fluid containment
- Use of a pit or tank to hold mud and cuttings so they are not released to streams or wetlands. Disposal must follow permit requirements.