CT Well Driller cheat sheet

Cable-tool drilling advances by repeatedly lifting and dropping a heavy bit on a chisel edge; cuttings are removed with a bailer, and casing is driven behind the bit. It is the traditional method for unconsolidated glacial deposits common in Connecticut.

Rotary air drilling uses a rotating tricone or button bit with compressed air as the circulating medium; it is fast in hard bedrock but requires a stable hole and dust control, and it cannot control formation water inflow without foam or additives.

Mud rotary drilling circulates a bentonite- or polymer-based fluid that cools the bit, lifts cuttings, and stabilizes the borehole wall with a filter cake; mud weight and viscosity must be balanced to avoid formation damage and lost circulation.

Drilling-fluid velocity in the annulus must exceed the cuttings' slip velocity; rule of thumb for effective hole cleaning is an annular return velocity of roughly 100-150 ft/min in mud rotary, higher in large-diameter holes.

Borehole deviation increases with depth, bit weight, and formation dip; straight-hole drilling practice limits deviation to about 1 degree per 100 ft of depth, verified with a plumb-bob or downhole survey.

In overburden, temporary surface casing or a conductor pipe is set through unconsolidated soils and shallow water-bearing zones before drilling into bedrock, preventing caving and cross-connection of shallow and deep water.

Penetration rate drops sharply when a bit dulls; gauge wear, broken teeth, and bit balling in clay are the main causes, and trip time is weighed against continued slow drilling.

Well development by surging, bailing, or jetting removes drilling fines and wall cake so the formation transmits water freely; development continues until discharge runs clear of sediment.

Loss of circulation occurs in fractured or cavernous bedrock or high-permeability gravel; remedies include reducing pump rate, adding lost-circulation material, or setting casing past the loss zone.

Connecticut requires a minimum of 6 inches of annular space between the borehole wall and the outside of the well casing, and a minimum of 2 inches between the casing and any inner casing or liner, so grout can be placed and sealed.

Neat cement grout is mixed at no more than 6 gallons of clean water per 94-pound sack of cement; a common specification is a minimum of 1.5 cubic feet of grout per cubic foot of annular space to allow for hole irregularities.

Grout is placed by pumping through a tremie pipe from the bottom of the annular space upward, so the grout displaces water and drilling fluid and no voids or bridging occur.

Bentonite grout is prepared with a minimum of 1 part bentonite to 10 parts water by weight and must be allowed to hydrate before placement; cement-based grout is used where a hard, durable seal is required.

The annular seal must extend from the top of the well down to the first competent confining layer, or to the full depth of the casing where no confining unit is present, and must be at least 20 feet deep in bedrock wells.

Casing must extend at least 12 inches above finished grade or the floor of the well pit; the top is fitted with a sanitary, vermin-proof well cap that is not vented directly to the atmosphere.

The well casing must be new steel meeting ASTM or API standards; used or reconditioned casing is not acceptable for potable water wells in Connecticut.

A pitless adapter, where used, must be installed below the frost line and be of a type that provides a watertight, sanitary connection through the casing wall.

A well screen or open borehole in bedrock is selected by formation; screens are sized to the formation gradation so that the screen retains at least 90 percent of the aquifer material while passing fines during development.

Porosity is the fraction of rock or sediment volume that is void space; specific yield is the drainable porosity, and specific retention is water held by capillary forces. Effective porosity, not total porosity, controls groundwater flow.

Darcy's law: Q = K i A, where Q is discharge, K is hydraulic conductivity, i is hydraulic gradient, and A is cross-sectional area; flow is proportional to gradient and conductivity in laminar conditions.

Transmissivity T = K b, where b is saturated thickness; storativity S is the volume of water released from storage per unit area per unit decline in head.

Connecticut bedrock is largely crystalline metamorphic rock (schist, gneiss, granite); groundwater occurs in fractures and faults, so well yield depends on intersecting fracture zones rather than rock porosity.

The water table is the upper surface of the saturated zone in an unconfined aquifer; it rises and falls with recharge and is the level to which water stands in an open observation well.

A confined aquifer is bounded by confining layers and stores water under pressure; the potentiometric surface is the level to which water would rise in a well, and artesian flow occurs where that surface is above land surface.

Recharge to Connecticut aquifers comes mainly from precipitation infiltrating through overburden; discharge occurs through wells, springs, streams, and evapotranspiration, and long-term withdrawal must not exceed recharge.

The cone of depression around a pumping well deepens with higher pumping rate and lower transmissivity; overlapping cones from nearby wells cause interference and reduced yields.

Groundwater flows from high head to low head perpendicular to equipotential lines; a flow net of equipotential and flow lines shows direction and relative rate of movement.

A submersible pump is rated by its performance curve: capacity (gpm) and total dynamic head (feet) at a given efficiency; the operating point is where the pump curve intersects the system curve.

Total dynamic head equals the static lift plus drawdown plus the friction loss in the discharge pipe plus the pressure head required at the point of use.

Friction loss in plastic pipe rises roughly with the square of flow; small-diameter drop pipe and long laterals cause large head losses, so pipe sizing must be checked against the pump curve.

A pressure tank with a bladder holds water under precharge pressure; the tank precharge should be set about 2 psi below the pump cut-in pressure, and the tank must be sized to limit pump cycling.

A pressure switch controls pump start and stop; typical settings are 30/50 psi or 40/60 psi, and the differential and cut-in must match the tank precharge and system design.

A constant-pressure or variable-frequency drive varies pump speed to hold a set pressure; the pump still must be selected so it operates within its recommended flow range at all speeds.

A pump test records static water level, pumping water level, pumping rate, and time; drawdown is the difference between static and pumping levels, and specific capacity is yield divided by drawdown in gpm per foot.

A safe yield test pumps the well at a controlled rate for a specified period (commonly 1 to 4 hours or longer) and measures recovery; the well is accepted if water level recovers to within a set percentage of static level.

Water quality testing for a new well typically includes coliform bacteria, nitrate, and other parameters; a potable supply must be free of coliform bacteria and meet Connecticut drinking water standards.

Well drilling contractors must be registered with the Connecticut Department of Consumer Protection and hold a current well drilling contractor registration; individual drillers must be licensed by the state.

A well permit or registration must be filed with the local health department before drilling a new well or substantially altering an existing one; the local director of health approves the location and construction.

The well must be located at least 25 feet from a septic tank, 50 feet from a septic leaching field or subsurface sewage disposal area, and 75 feet from a manure storage or animal enclosure, with greater distances required for other contamination sources.

The well must be at least 50 feet from a watercourse or wetland and at least 10 feet from a property line, unless a variance is granted by the local health authority.

A well completion report must be filed with the state and the local health department, documenting depth, casing, grout, yield, and water quality; the driller must provide the well owner a copy.

The well driller must be licensed and must supervise drilling; unlicensed persons may not drill, deepen, or repair wells except under direct supervision as allowed by regulation.

Casing and grouting standards are enforced at inspection; a well that fails to meet annular seal or casing requirements must be corrected before it is approved for use.

Abandoned wells must be properly abandoned by filling with approved grout or material and sealing, and the abandonment must be reported to the state; an unsealed well is a direct pathway for surface contamination.

Continuing education and renewal requirements apply to well drilling licenses, and a driller must carry proof of registration and comply with state bonding and insurance requirements.

Before drilling, call 811 (Call Before You Dig) and have underground utilities located; drilling into a gas, electric, or fuel line can be fatal.

Confined-space entry into a well pit or vault requires atmospheric testing for oxygen, hydrogen sulfide, and combustible gas, plus a permit, attendant, and retrieval system; never enter alone.

Rigging and hoisting safety: keep personnel clear of the rotary table and suspended loads, inspect cables and slings, and never exceed the rig's rated capacity.

Dust from air rotary drilling contains silica; use water spray or dust suppression and respiratory protection, and monitor noise exposure around compressors and rigs.

Fuel, oil, and drilling fluids must be stored and handled to prevent spills; use containment, absorbent materials, and a spill kit, and report releases to the state.

Drilling fluids and cuttings must not be discharged to wetlands or watercourses; contain and dispose of them according to state and local requirements.

Electrical safety around pumps and controls: use ground-fault protection, lock out and tag out before servicing, and verify that the well casing and pump are properly grounded.

A well that is not properly sealed can transmit surface contamination directly to groundwater; the annular grout seal, sanitary cap, and proper abandonment are the primary environmental protections.

Personal protective equipment for drilling includes hard hat, safety glasses, hearing protection, steel-toe boots, and gloves; high-visibility clothing is required near traffic.