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NC Well Driller practice questions

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Question 1Well Construction and Drilling Methods

Under the North Carolina well construction rules, what is the minimum required annular seal (grout) depth for a new private drinking water well?

  1. 50 feet below land surface
  2. 20 feet below land surface Correct answer.
  3. 100 feet below land surface
  4. 10 feet below land surface

Explanation

North Carolina requires a continuous annular seal of at least 20 feet for a private drinking water well, extending from land surface downward around the casing. The seal prevents surface water and shallow groundwater from migrating down the annulus into the well. Deeper seals may be required by local conditions or the permitting agency, but 20 feet is the statewide minimum.

Question 2Well Construction and Drilling Methods

A drilled well penetrates a shallow sand layer at 25 feet and a confining clay layer below it. The driller wants to prevent shallow groundwater from entering the annulus. What is the most appropriate construction approach?

  1. Complete the well open-hole with no casing through the sand
  2. Set surface casing through the clay and grout the annulus before drilling ahead Correct answer.
  3. Drill the full hole and grout only the bottom 10 feet of casing
  4. Backfill the annulus with drill cuttings after setting the screen

Explanation

Setting surface casing through the confining layer and grouting its annulus isolates shallow groundwater before the borehole advances into deeper aquifers. This prevents shallow water from short-circuiting down the annulus. Grouting only the bottom or leaving the hole open would allow cross-contamination between aquifers.

Question 3Well Construction and Drilling Methods

What is the primary purpose of a sanitary well seal at the top of a well casing?

  1. To increase the well yield by pressurizing the casing
  2. To measure the static water level in the well
  3. To prevent surface water and contaminants from entering the well at the casing top Correct answer.
  4. To anchor the pump drop pipe to the borehole wall

Explanation

A sanitary seal caps the casing around the pump piping and wiring so surface water, insects, and debris cannot enter the well. It maintains the integrity of the wellhead as a barrier against contamination. It has no role in measuring water level, boosting yield, or anchoring pipes.

Question 4Well Construction and Drilling Methods

A driller is using the mud rotary method and observes that cuttings are no longer returning to the surface while pump pressure rises. What is the most likely cause?

  1. The drill string is rotating too slowly
  2. The bit has reached the water table
  3. The mud weight is too low for the formation
  4. The borehole wall has collapsed or a fracture is causing lost circulation Correct answer.

Explanation

Loss of cuttings return combined with rising pump pressure signals a blockage or loss of circulation, often from a collapsed wall or a fracture taking the drilling fluid. The driller should stop and assess before continuing. Reaching water or slow rotation would not produce this combination of symptoms.

Question 5Well Construction and Drilling Methods

Which drilling method uses a heavy cable and bit that breaks rock by repeated impact rather than by rotation?

  1. Direct rotary drilling
  2. Mud rotary drilling
  3. Air rotary drilling
  4. Cable tool drilling Correct answer.

Explanation

Cable tool drilling, also called percussion drilling, lifts and drops a heavy bit on a cable to crush rock by impact. The cuttings are removed periodically with a bailer. Rotary methods cut by turning a bit, not by repeated impact.

Question 6Well Construction and Drilling Methods

During air rotary drilling, the driller notices large volumes of fine dust blowing from the discharge and no water in the returns. What does this most likely indicate?

  1. The bit is plugged with clay
  2. The formation is yielding abundant groundwater
  3. The hole is above the water table and producing dry cuttings Correct answer.
  4. The air pressure is too low to lift cuttings

Explanation

Dry, dusty returns during air rotary drilling indicate the borehole is above the saturated zone and the cuttings are dry rock dust. Once the bit enters the water table, returns typically become wet and heavier. Low air pressure would reduce return velocity rather than produce copious dry dust.

Question 7Well Construction and Drilling Methods

What is the standard purpose of a gravel pack placed around a well screen?

  1. To increase the strength of the casing string
  2. To seal the annulus against surface water
  3. To measure the hydraulic head in the aquifer
  4. To filter formation material and stabilize the borehole around the screen Correct answer.

Explanation

A gravel pack is sized to the formation so it filters out fine particles while allowing water to flow into the screen. It also supports the borehole wall around the screen. It is not a sealing material, a structural casing component, or a measuring device.

Question 8Well Construction and Drilling Methods

A well is completed in a confined sandstone aquifer. The driller observes that the water level rises above the top of the aquifer after drilling stops. What is this condition called?

  1. Artesian conditions Correct answer.
  2. Cone of depression
  3. Perched water table
  4. Specific capacity

Explanation

When the static water level in a well rises above the top of a confined aquifer, the aquifer is artesian and the well is under pressure. A perched water table sits above a local impermeable layer and does not produce this rise. Cone of depression and specific capacity describe drawdown and yield, not static head.

Question 9Well Construction and Drilling Methods

What is the minimum recommended screen slot size relationship to the gravel pack material?

  1. The slot should be larger than the largest gravel particle
  2. The slot should be smaller than the finest formation particle
  3. The slot should equal the casing diameter
  4. The slot should retain most of the gravel pack while allowing fines to pass Correct answer.

Explanation

Screen slot size is selected to retain the gravel pack so the pack acts as a filter, while allowing formation fines to move through and be developed out. Slots larger than the gravel would let the pack pass and defeat the filter. Slot size is independent of casing diameter.

Question 10Well Construction and Drilling Methods

Why is a bentonite seal often placed above the gravel pack in a screened well?

  1. To lubricate the casing during installation
  2. To increase the flow of water into the screen
  3. To separate the gravel pack from the grout above and prevent grout intrusion Correct answer.
  4. To provide a source of chloride for disinfection

Explanation

A bentonite seal above the gravel pack acts as a barrier that keeps the cement or bentonite grout from migrating down into the filter pack. This preserves the pack's filtering function and ensures a proper annular seal. It does not increase flow, lubricate casing, or disinfect the well.

Question 11Well Construction and Drilling Methods

A driller is developing a new gravel-packed well and wants to remove drilling mud and fines from the formation near the screen. Which method relies on surging water back and forth through the screen?

  1. Surge block development Correct answer.
  2. Overpumping at high rate
  3. Jetting with a high-pressure nozzle
  4. Air lift development

Explanation

Surge block development moves a plunger or block up and down to force water alternately out through the screen and back into the well, loosening and flushing fines. Air lift and jetting use forced air or directed water jets rather than surging. Overpumping removes fines but does not reverse flow through the screen.

Question 12Well Construction and Drilling Methods

What is the main purpose of a test well or pilot hole before completing a production well?

  1. To measure the elevation of the land surface
  2. To grout the annulus of the future well
  3. To evaluate formation depth, water quality, and yield before final design Correct answer.
  4. To serve permanently as the production well

Explanation

A test hole or pilot hole lets the driller log formations, sample water, and estimate yield so the production well can be designed with appropriate depth, screen, and casing. It is not intended as the final well and does not perform grouting or surveying functions.

Question 13Well Construction and Drilling Methods

A driller plans to grout the annulus of a well using a positive displacement pump and a tremie pipe. Why is the tremie pipe method preferred over pouring grout from the surface?

  1. It eliminates the need for a sanitary seal
  2. It allows grout to be mixed in the hole
  3. It places grout from the bottom up and avoids bridging and voids Correct answer.
  4. It reduces the total volume of grout needed

Explanation

Pumping grout through a tremie pipe from the bottom of the annulus upward displaces water and prevents bridging, gaps, and dilution that occur when grout is poured from the top. This produces a continuous, competent seal. Grout is mixed at the surface, and the method does not remove the need for a sanitary seal.

Question 14Well Construction and Drilling Methods

What does the term "static water level" refer to in a well?

  1. The elevation of the screen top
  2. The depth of the pump intake
  3. The water level during maximum pumping
  4. The water level when the well is not being pumped Correct answer.

Explanation

Static water level is the stabilized water level in a well under non-pumping conditions, reflecting the natural hydraulic head of the aquifer. Pumping water level is measured while the well is being drawn down. It is not a pump setting or a screen elevation.

Question 15Well Construction and Drilling Methods

A driller is logging a borehole and notes that a clay layer is encountered between two sand layers. What is the significance of this clay layer for well construction?

  1. It guarantees the well will be artesian
  2. It means the gravel pack must be omitted
  3. It indicates the borehole should be abandoned
  4. It can act as a confining layer separating aquifers and should guide casing and seal placement Correct answer.

Explanation

A clay layer can separate aquifers and prevent vertical movement of water, so the driller uses it to decide where to set casing and seals to avoid mixing waters of different quality. It does not by itself require abandonment, guarantee artesian flow, or dictate omission of a gravel pack.

Question 16Well Construction and Drilling Methods

Which of the following best describes the function of a well casing?

  1. To filter fine particles from the formation
  2. To provide pressure to lift water to the surface
  3. To seal the annulus against contamination
  4. To maintain the borehole opening and prevent collapse into the well Correct answer.

Explanation

Casing holds the borehole open and prevents formation material from collapsing into the well. Filtering is done by the screen and gravel pack, lifting is done by the pump, and annular sealing is done by grout.

Question 17Well Construction and Drilling Methods

A driller is using a hollow-stem auger and needs to sample the formation ahead of the auger. What is the standard method?

  1. Remove the auger and hand-dig a sample
  2. Drop a weighted bailer down the auger
  3. Pass a sampling tool through the hollow stem to the bottom of the hole Correct answer.
  4. Pump water up the auger to wash out a sample

Explanation

Hollow-stem augers allow a sampler or split-spoon to be lowered through the hollow center to the undisturbed formation below the cutting head. Removing the auger would cause the hole to collapse, and washing or bailing does not collect a representative formation sample.

Question 18Well Construction and Drilling Methods

What is the purpose of a well screen in an unconsolidated sand aquifer?

  1. To measure the flow rate of the well
  2. To support the weight of the pump and drop pipe
  3. To hold back formation material while allowing water to enter the well Correct answer.
  4. To prevent corrosion of the casing

Explanation

A well screen is designed with openings that retain the gravel pack and formation while permitting water to flow into the well. It is not a structural support for the pump, a corrosion control measure, or a flow meter.

Question 19Well Construction and Drilling Methods

During well construction, a driller encounters a cavernous limestone formation and loses all drilling fluid. Which approach is most appropriate for maintaining hole stability and completing the well?

  1. Increase mud weight to force fluid into the cavern
  2. Set casing to seal the loss zone and use a controlled drilling method below it Correct answer.
  3. Abandon the site because caverns cannot be cased
  4. Continue drilling without circulation until the bit reaches total depth

Explanation

In cavernous or highly permeable formations, casing off the loss zone isolates it and allows drilling to continue with controlled circulation below. Increasing mud weight may worsen losses, and drilling blind without returns risks stuck tools and hole instability. Cavernous zones can be cased successfully.

Question 20Well Construction and Drilling Methods

What is the purpose of a packer in a well completion?

  1. To filter sediment from the produced water
  2. To increase the pumping rate of the well
  3. To isolate a section of the borehole or casing from the rest of the well Correct answer.
  4. To measure the water level in the well

Explanation

A packer is an inflatable or mechanical device that seals the annulus at a chosen depth to isolate zones, direct flow, or protect casing. It does not boost pumping rate, filter sediment, or measure water level.

Question 21Well Construction and Drilling Methods

A driller is selecting casing material for a well in acidic groundwater with elevated chloride. Which casing material is generally most resistant to corrosion in this environment?

  1. Galvanized steel casing
  2. Thermoplastic (PVC) casing Correct answer.
  3. Carbon steel casing
  4. Cast iron casing

Explanation

Thermoplastic casing such as PVC resists corrosion from acidic and high-chloride water, whereas steel and iron casings can corrode. Galvanized coatings provide only temporary protection and can fail in aggressive water. Material selection should also consider structural strength requirements.

Question 22Well Construction and Drilling Methods

What does a driller mean by "developing" a well?

  1. Installing the pump and pressure tank
  2. Disinfecting the well with chlorine
  3. Removing drilling fluids and fines from the formation and filter pack to improve flow Correct answer.
  4. Drilling the borehole to its final depth

Explanation

Well development removes mud, silt, and fines from the filter pack and the formation near the screen so the well produces clear water at its full capacity. Drilling, pump installation, and disinfection are separate steps that do not accomplish development.

Question 23Well Construction and Drilling Methods

A driller is completing a well and must choose the depth to set the casing shoe. Which principle best guides this decision?

  1. Set the shoe into a competent confining layer below the zones to be sealed Correct answer.
  2. Set the shoe at the bottom of the screen
  3. Set the shoe just below land surface in all wells
  4. Set the shoe at the static water level

Explanation

The casing shoe should be seated in a competent, low-permeability layer so the annulus seal above it can isolate shallower zones from the producing aquifer. Setting it near the surface, at the water level, or at the screen bottom would not provide a proper seal.

Question 24Well Construction and Drilling Methods

What is the main reason for keeping a drilling log during well construction?

  1. To track fuel consumption of the rig
  2. To record formation depths, water strikes, and construction details for the well record Correct answer.
  3. To calculate the driller's labor hours
  4. To determine the price of the well

Explanation

A drilling log documents the geology encountered, depth of water-bearing zones, casing and screen settings, and grouting details. This record supports permitting, future maintenance, and verification of construction. It is not a labor, fuel, or pricing document.

Question 25Well Construction and Drilling Methods

A well is drilled to 200 feet and the driller plans to grout the annulus. The grout mix is designed with a density of about 15 pounds per gallon. Why is grout density important during placement?

  1. Higher density grout increases the well yield
  2. Higher density grout lowers the pumping head
  3. Higher density grout helps displace water and resist dilution in the annulus Correct answer.
  4. Higher density grout reduces the need for casing

Explanation

A properly weighted grout slurry displaces water in the annulus and resists dilution, helping form a continuous seal. Density does not increase well yield, replace casing, or change pumping head. Grout density must be balanced against formation pressures to avoid fracturing.

Question 26Well Construction and Drilling Methods

A driller is setting the casing shoe in a well completed in unconsolidated sand and gravel. The casing must pass through a soft clay confining layer before reaching the producing sand. Which placement of the casing shoe best protects the well?

  1. Set the shoe exactly at the static water level to control the pump setting
  2. Set the shoe just above the top of the producing sand so the screen hangs free
  3. Set the shoe at the total drilled depth and perforate the casing later
  4. Set the shoe a few feet into the clay confining layer to seal off the sand above Correct answer.

Explanation

The casing shoe should be seated into a competent confining layer so the annular seal and cement can be tied into low-permeability material, preventing water from upper zones from moving down the annulus. Landing the shoe in clay a few feet below the contact gives a reliable seat for the seal and leaves the producing sand open for the screen.

Question 27Well Construction and Drilling Methods

Which drilling method uses a heavy steel bit that is lifted and dropped on a cable to break and crush formation material, with the cuttings removed by a bailer?

  1. Direct rotary drilling
  2. Reverse circulation drilling
  3. Cable tool drilling Correct answer.
  4. Hollow-stem auger drilling

Explanation

Cable tool drilling, also called percussion drilling, breaks rock by repeated impact of a heavy bit suspended on a wire line, and cuttings are removed periodically with a bailer. It is the traditional method suited to hard rock and boulder formations and requires no circulating drilling fluid.

Question 28Well Construction and Drilling Methods

A driller is advancing a borehole with a mud rotary rig and wants cuttings to rise in the annulus. Which relationship between annular velocity and the cuttings' settling velocity must be maintained?

  1. Annular velocity must equal the settling velocity of the cuttings
  2. Annular velocity is irrelevant as long as pump pressure is high
  3. Annular velocity must be less than the settling velocity of the cuttings
  4. Annular velocity must exceed the settling velocity of the cuttings Correct answer.

Explanation

For cuttings to be transported to the surface, the upward velocity of the drilling fluid in the annulus must be greater than the rate at which the cuttings would settle through that fluid. If the annular velocity falls below the settling velocity, cuttings accumulate downhole and can cause sticking or loss of circulation.

Question 29Well Construction and Drilling Methods

What is the primary function of a surface casing string in a water well?

  1. To measure the water level and record pump drawdown
  2. To house the pump and provide a sanitary seal at the wellhead
  3. To seal off shallow formations and protect the borehole from caving near the surface Correct answer.
  4. To screen the producing aquifer and control sand entry

Explanation

Surface casing is the upper string installed to stabilize the shallow borehole and seal off unconsolidated or contaminated shallow materials. It provides a competent base for the wellhead seal and helps protect groundwater from surface contamination.

Question 30Well Construction and Drilling Methods

A driller is using a hollow-stem auger and needs to collect a relatively undisturbed sample of saturated sand below the water table. Which sampler is most appropriate for this condition?

  1. Standard split-spoon sampler driven with a hammer
  2. Thin-walled Shelby tube pushed into the formation Correct answer.
  3. Solid-stem auger with continuous flighting
  4. Bailer lowered through the hollow stem

Explanation

A thin-walled Shelby tube is pushed hydraulically or by hand into fine-grained or saturated cohesionless material to obtain a relatively undisturbed sample. Driving a split spoon with a hammer disturbs the matrix, and a bailer recovers only loose cuttings and slurry.

Question 31Well Construction and Drilling Methods

A driller is mixing a bentonite-based drilling fluid and wants to increase its viscosity to improve cuttings transport. Which change is the standard approach?

  1. Add a thinning agent to reduce the yield point
  2. Add more bentonite to the mix and allow proper hydration time Correct answer.
  3. Increase the sand content by recirculating dirty returns
  4. Dilute the mud with fresh water to lower its density

Explanation

Adding bentonite and allowing it to hydrate increases the viscosity and yield point of the mud, improving its ability to carry cuttings. Proper hydration time is essential for the clay to fully disperse and develop the desired properties.

Question 32Well Construction and Drilling Methods

A driller observes that the drill string is binding and the pump pressure has risen sharply while drilling in a shale formation. What is the most likely cause?

  1. The static water level has dropped below the pump intake
  2. The pump is running too slowly to lift cuttings
  3. The annulus is packing off with cuttings or swelling clay Correct answer.
  4. The bit has encountered a cavern and lost circulation

Explanation

Rising pump pressure combined with a binding drill string typically indicates the annulus is packing off, often from cuttings accumulation or swelling clay in shale. The restricted return path raises pressure and increases friction on the string.

Question 33Well Construction and Drilling Methods

In a reverse circulation rotary system, how is the drilling fluid routed through the borehole?

  1. Through the hollow stem of an auger only
  2. Down the drill pipe and up the annulus
  3. Down both the annulus and the drill pipe simultaneously
  4. Down the annulus and up the drill pipe Correct answer.

Explanation

Reverse circulation sends the drilling fluid down the annular space and returns it, along with cuttings, up through the inside of the drill pipe. This design allows large cuttings to be lifted efficiently and is common for large-diameter wells.

Question 34Well Construction and Drilling Methods

A driller is completing a well and must decide the grout placement method for the annular seal in a deep cased hole. Why is a positive displacement pump with a tremie pipe preferred over free-falling grout from the surface?

  1. Free-falling grout sets too slowly to seal the annulus
  2. Free-falling grout can bridge and trap drilling fluid, leaving voids in the seal Correct answer.
  3. A tremie pipe increases the density of the grout mix
  4. A positive displacement pump prevents the grout from curing

Explanation

Grout poured from the surface can bridge on casing centralizers or fall unevenly, trapping drilling fluid and leaving voids that compromise the seal. Pumping through a tremie pipe placed near the bottom displaces the fluid upward and produces a continuous, competent column.

Question 35Well Construction and Drilling Methods

What is the purpose of a drive shoe on the bottom of a casing string?

  1. To filter sand from the produced water
  2. To centralize the casing within the borehole
  3. To measure the depth of the casing string
  4. To provide a hardened cutting edge that protects the casing as it is driven Correct answer.

Explanation

A drive shoe is a hardened steel ring attached to the bottom of the casing to protect the pipe end and cut through formation material as the casing is driven. It provides a durable leading edge that reduces damage to the casing during driving.

Question 36Well Construction and Drilling Methods

A driller is evaluating whether to use a mud rotary or an air rotary method in a fractured bedrock aquifer where the static water level is 150 feet deep. Which condition most favors air rotary?

  1. The driller needs to maintain a heavy bentonite filter cake
  2. The formation is hard, dry, and stable with limited water inflow Correct answer.
  3. The formation is a soft clay that swells when wet
  4. The borehole produces abundant water that must be lifted

Explanation

Air rotary performs well in hard, stable, dry formations where there is little water to interfere with air lifting of cuttings. When abundant water flows into the hole, air rotary can lose its ability to lift cuttings and may require foam or a switch to mud.

Question 37Well Construction and Drilling Methods

A driller is installing a well in a formation where the water contains high levels of dissolved hydrogen sulfide and carbon dioxide. Which casing material is generally least suitable under these corrosive conditions?

  1. Carbon steel Correct answer.
  2. Stainless steel
  3. Fiberglass-reinforced plastic
  4. Thermoplastic (PVC)

Explanation

Carbon steel is susceptible to corrosion from dissolved carbon dioxide, hydrogen sulfide, and low-pH water, and can degrade quickly in aggressive groundwater. Stainless steel, PVC, and fiberglass-reinforced plastic offer better resistance to these corrosive conditions.

Question 38Well Construction and Drilling Methods

A driller is completing a well and needs to determine the length of blank casing to set above the screen. Which factor most directly governs the top of the screen interval?

  1. The grout volume required for the annular seal
  2. The total depth of the borehole and the pump setting
  3. The depth of the producing zone and the static water level Correct answer.
  4. The diameter of the borehole and the casing wall thickness

Explanation

The screen must be positioned to intersect the producing zone while accounting for the static water level and drawdown so the pump remains submerged. The top of the screen is set at the upper boundary of the producing interval, and blank casing extends upward from there.

Question 39Well Construction and Drilling Methods

During cable tool drilling, a driller notices the tools are dropping freely and the bailer returns very little material. What does this most likely indicate?

  1. The hole has entered a large void or cavern Correct answer.
  2. The casing has been set too shallow
  3. The bit is dull and needs to be sharpened
  4. The drilling line is too tight

Explanation

Free-falling tools and little recovered material suggest the bit has broken into an open void or cavern where there is nothing to break and no cuttings to bail. The driller should confirm the depth and adjust the completion plan for the cavity.

Question 40Well Construction and Drilling Methods

A driller is selecting a drilling method for a deep municipal well in a hard sandstone aquifer where large-diameter casing will be installed. Which method is generally best suited to this application?

  1. Reverse circulation rotary drilling Correct answer.
  2. Jetting with a wash pipe
  3. Cable tool drilling
  4. Hand auger drilling

Explanation

Reverse circulation rotary drilling is well suited to large-diameter, deep wells in hard rock because it lifts large cuttings efficiently through the drill pipe and maintains a stable borehole. It is commonly chosen for municipal and high-capacity wells.

Question 41Well Location, Siting, and Setback Requirements

Under the North Carolina well construction rules, which separation distance applies between a new private drinking water well and a septic tank absorption field (drainfield) trench?

  1. 25 feet
  2. 10 feet
  3. 100 feet Correct answer.
  4. 50 feet

Explanation

North Carolina requires a minimum horizontal separation of 100 feet between a drinking water well and the trenches of a septic system absorption field, because effluent moves laterally through soil toward the borehole. The 50-foot figure applies to other components such as the septic tank itself, so the drainfield distance must not be confused with the tank distance.

Question 42Well Location, Siting, and Setback Requirements

A driller is siting a well on a lot where a neighbor's existing well lies 40 feet away. What is the minimum required separation between two private drinking water wells in North Carolina?

  1. 25 feet
  2. 100 feet
  3. 75 feet
  4. 50 feet Correct answer.

Explanation

Wells must be separated from one another by at least 50 feet so that a failure or contamination at one borehole does not readily reach the other. This spacing also limits interference between pumping water levels.

Question 43Well Location, Siting, and Setback Requirements

Which condition makes a proposed well location unacceptable regardless of the setback distances achieved?

  1. The site is in a low area subject to surface water ponding or drainage Correct answer.
  2. The site is more than 500 feet from a paved road
  3. The site is within a designated floodplain
  4. The site is within 200 feet of a property line

Explanation

A well must be located where it will not be flooded or affected by surface drainage, since standing water at the casing can carry contaminants into the annulus. Floodplain location alone is not automatically disqualifying if the well head can be protected above flood level.

Question 44Well Location, Siting, and Setback Requirements

A well is to be placed near a barnyard where livestock are confined. What minimum separation from the barnyard or animal enclosure is required?

  1. 50 feet Correct answer.
  2. 150 feet
  3. 100 feet
  4. 25 feet

Explanation

North Carolina requires at least 50 feet between a well and a barnyard, feedlot, or similar animal confinement area because of the concentrated bacterial and nitrate loading in those areas. Greater distances may be needed where slope or drainage directs runoff toward the well.

Question 45Well Location, Siting, and Setback Requirements

What is the required minimum separation between a drinking water well and a public or private sewer line that is constructed of approved watertight material?

  1. 25 feet
  2. 100 feet
  3. 50 feet
  4. 10 feet Correct answer.

Explanation

A properly constructed, watertight sewer line may pass as close as 10 feet from a well, because the pipe is designed not to leak. Non-watertight or cast iron gravity lines require a larger separation.

Question 46Well Location, Siting, and Setback Requirements

A proposed well sits 75 feet from the edge of a septic tank absorption field on a neighboring parcel. How should the driller treat this location?

  1. Accept it, because the field is on another property
  2. Accept it if the well casing is extended 2 feet above grade
  3. Accept it only if the neighbor signs a waiver
  4. Reject it, because the 100-foot setback applies regardless of property lines Correct answer.

Explanation

Setback distances are measured to the contamination source itself, not to property boundaries, so a drainfield on an adjoining lot counts the same as one on the well owner's lot. At 75 feet the location fails the 100-foot requirement.

Question 47Well Location, Siting, and Setback Requirements

Which of these is the correct basis for measuring setback distances from a well?

  1. From the pump to the source
  2. From the well head to the center of the source
  3. From the property line to the source
  4. From the centerline of the well bore to the nearest edge of the source Correct answer.

Explanation

Setbacks are measured horizontally from the well bore to the nearest point of the contamination source, because that is the shortest path groundwater could travel. Measuring to the center of a large source would overstate the true separation.

Question 48Well Location, Siting, and Setback Requirements

A driller proposes a well 45 feet from a septic tank (not the absorption field). Is this acceptable?

  1. Yes, tanks require only 25 feet
  2. No, tanks require 10 feet
  3. No, tanks require 100 feet
  4. Yes, the required separation from a septic tank is 50 feet, so 45 feet fails Correct answer.

Explanation

The setback from a septic tank is 50 feet, so a 45-foot separation is short of the requirement and the location must be moved. The larger 100-foot distance applies only to the absorption field trenches.

Question 49Well Location, Siting, and Setback Requirements

Which setback applies between a well and a chemical or petroleum storage tank located above ground?

  1. 100 feet Correct answer.
  2. 150 feet
  3. 50 feet
  4. 25 feet

Explanation

A 100-foot separation is required from fuel and chemical storage tanks because a release could migrate rapidly to the borehole. This matches the protection level given to other high-risk contamination sources such as absorption fields.

Question 50Well Location, Siting, and Setback Requirements

A non-public water-supply well is proposed within 50 feet of a stream that carries water year-round but is not a groundwater-recharge source. What is the applicable requirement?

  1. A minimum 50-foot separation from surface water is required
  2. A minimum 25-foot separation from surface water is required Correct answer.
  3. A minimum 10-foot separation from surface water is required
  4. No setback is required from surface water

Explanation

Rule 02C .0107(a)(2)(R) requires a 25-foot separation from ordinary streams and other surface waters that are not groundwater-recharge sources. The separate 50-foot requirement in paragraph (Q) applies to recharge bodies. A stream's year-round flow alone does not establish that classification.