NC Well Driller cheat sheet

Cased borehole must extend into competent rock or an impermeable layer; annular space above the screen or open hole is the grout zone, so casing depth and grout depth are set together.

Rotary air and mud drilling suit unconsolidated Coastal Plain sediments; cable tool is preferred where boulders, hard rock, or cave-prone formations make hole cleaning difficult.

Minimum annular clearance between borehole wall and casing is 2 inches nominal in NC; a larger annulus risks grout bridging, a smaller one prevents proper grout placement.

Well casing must be new steel or NSF/ANSI 61-certified plastic; used casing is prohibited in new wells unless approved for a specific non-potable use.

Casing must extend at least 12 inches above finished grade or 12 inches above the floor of a well house, and the top must be fitted with a sanitary, vermin-proof well cap.

Screen openings are sized to retain 90 percent or more of the formation sample; slot size is selected from sieve analysis of the aquifer material, not guessed.

A well's total depth and casing/grout depths must be recorded on the well log at the time of construction; the log is filed with the state and is the legal record of the well.

When drilling through a confining layer, do not penetrate it deeper than necessary; each additional aquifer tapped increases the risk of cross-contamination between zones.

Minimum setback from a septic tank or septic system is 50 feet; from the drainfield or other absorption field is 100 feet, measured horizontally from the well head.

Minimum setback from a sanitary sewer line is 50 feet; from a sewer force main or gravity line under pressure, 100 feet, unless the line is constructed of specified pressure-rated materials.

Setback from a landfill, hazardous waste site, or land application of sludge is 100 feet or more depending on the activity; confirm the current rule table before siting.

Wells must be located where surface drainage flows away from the casing; the ground must be graded so the well head is not a low point or in a drainage swale.

A well must not be located in a floodway or area subject to frequent flooding unless the casing is extended and sealed to prevent floodwater entry.

Setbacks are measured horizontally from the well casing to the nearest edge of the facility, not to the centerline of a building or the middle of a drainfield.

Animal feedlots, barnyards, and chemical storage must be at least 100 feet from a well; fuel tanks and their lines have their own separation distances.

Property-line and building distances are governed by local zoning and by the state well rule; the more restrictive requirement controls when they conflict.

Neat cement grout is mixed at no more than 6 gallons of clean water per 94-pound sack of cement; bentonite grout is mixed per the manufacturer's density specification, typically 9.4 lb/gal or heavier.

Grout must be placed by the pump-and-tremie method from the bottom of the annular space upward; free-fall dumping of grout from the surface is not acceptable.

Positive displacement grout pumps and a tremie pipe are required so grout is not diluted or segregated as it travels down the annulus.

Where the annular space is dry and stable, granular bentonite may be used; below the water table or in caving formations, a bentonite slurry or cement grout is required.

Abandonment of a well requires filling the entire borehole with grout or approved sealing material, removing or perforating the casing as specified, and capping the top.

An abandoned well must be sealed within a specified time after it is taken out of service; leaving an open, unsealed hole is a violation and a direct pathway for contamination.

Grout volume is calculated as annulus area times height: V = 0.7854 x (D^2 - d^2) x L, using consistent units; add a margin for lost circulation and washouts.

A grout seal must extend from the top of the screen or open interval to land surface, or to the base of the well house floor, with no unsealed gap in between.

Well development removes drilling fines and mud cake to increase yield; methods include surging, jetting, bailing, and air-lift pumping until the discharge runs clear.

Development should not be so aggressive that it destabilizes the formation or pulls fines into the gravel pack; stop when turbidity stabilizes at a low level.

Pump setting depth must keep the pump intake above the screen and above the expected drawdown water level so the pump does not cavitate or run dry.

Submersible pump sizing uses the well yield, total dynamic head, and required pressure: TDH = static lift + drawdown + friction loss + discharge pressure head.

A pitless adapter provides a below-frost, sanitary connection through the casing; the casing top must still be sealed with a well cap and vent.

Pump tests should record static water level, pumping water level, yield, and drawdown; specific capacity is yield divided by drawdown, in gallons per minute per foot.

A check valve on the pump discharge prevents backflow and protects the pump; the pressure tank maintains system pressure and limits pump cycling.

Water quality sampling should follow a period of pumping to clear the line, and samples must be collected from a clean, sanitized tap ahead of treatment.

Well construction in North Carolina requires a certified well contractor; certification is issued by the state and must be current and in good standing at the time of work.

A well permit must be obtained before construction begins; the permit application includes the proposed location, depth, casing, and intended use.

The well log and completion report must be filed with the state within the required time after construction, and a copy must be provided to the well owner.

Certification can be suspended or revoked for violations such as constructing without a permit, failing to grout, or falsifying a well log.

Contractors must carry the insurance and bonding required by the certification program and must display or provide their certification number as required.

Continuing education is required to maintain certification; the required hours and renewal cycle are set by the state program and must be tracked.

Changes to a permitted well's location or construction must be approved before the change; a revised permit or authorization is required.

The contractor is responsible for compliance with the well rule and with local health department requirements; local rules may be stricter than state minimums.