NGWA Certified Well Driller (CWD) — Questions and Answers

Question 1: Why is regular review important in CWD risk management?

Only needed after incidents
Assessments stay valid forever
Prohibited more than annually
Conditions change and new risks emerge requiring updates (Correct answer)

Correct answer: Conditions change and new risks emerge requiring updates

Regular reviews ensure assessments remain current as conditions change and lessons from incidents are incorporated.

Question 2: What is the function of a drilling rig’s mud pump?

To control rig speed.
To circulate drilling fluid through the system (Correct answer)
To supply air to the compressor.
To power the drill bit.

Correct answer: To circulate drilling fluid through the system

The mud pump is a critical component of a drilling rig, responsible for circulating the drilling fluid (mud) through the drill string, out through the drill bit, and back up the annulus to the surface. This continuous circulation is essential for cooling the bit, removing cuttings from the borehole, and stabilizing the wellbore walls.

Question 3: On a well drilling invoice, 'per-foot pricing' typically covers:

Only labor costs for the drilling crew
Equipment rental only
All costs including mobilization, materials, and permits
The cost of drilling each foot of borehole, usually excluding casing, screen, and grout materials (Correct answer)

Correct answer: The cost of drilling each foot of borehole, usually excluding casing, screen, and grout materials

Per-foot drilling prices typically cover only the cost of advancing the borehole and are quoted separately from casing, screen, grout materials, development, pump, and other components listed as line items.

Question 4: The primary purpose of a pitless adapter in a well installation is to:

Provide electrical conduit access
Prevent surface water entry at the casing
Allow the discharge pipe to exit the casing below the frost line without a pit (Correct answer)
Support the pump column inside the casing

Correct answer: Allow the discharge pipe to exit the casing below the frost line without a pit

A pitless adapter allows the water supply pipe to exit through the well casing below the frost line, eliminating the need for a below-grade pump house pit while maintaining a sanitary seal.

Question 5: What is a work breakdown structure in CWD practice?

Hierarchical decomposition of deliverables into manageable work packages (Correct answer)
Organizational reporting diagram
Team member roster
Employee schedule report

Correct answer: Hierarchical decomposition of deliverables into manageable work packages

A WBS breaks total scope into progressively smaller components for easier estimation, scheduling, and tracking.

Question 6: What is porosity?

The color of a rock.
The ability of water to pass through rock.
The weight of the rock.
The amount of open space in rock or soil (Correct answer)

Correct answer: The amount of open space in rock or soil

Porosity refers to the amount of open space, or void space, within a rock or soil material. These interconnected or isolated pores can hold water or air. A material with high porosity can store a large volume of water, which is a fundamental characteristic for an effective aquifer, though permeability is also crucial for water extraction.

Question 7: Which drill bit is most suitable for drilling through hard rock formations?

Drag bit
PDC bit
Diamond coring bit
Tricone roller bit (Correct answer)

Correct answer: Tricone roller bit

Tricone roller bits are highly effective for drilling through a wide range of formations, including very hard rock. They feature three rotating cones with hardened teeth or inserts that crush and shear the rock as the bit rotates. This design allows them to withstand the forces required to penetrate dense geological structures efficiently and durably.

Question 8: Which grain size class generally has the highest hydraulic conductivity?

Fine sand
Coarse gravel (Correct answer)
Silt
Clay

Correct answer: Coarse gravel

Coarse gravel has large, well-connected pore spaces that offer minimal resistance to flow, resulting in the highest hydraulic conductivity of common sediment types.

Question 9: When should a well driller notify a client of a potential cost overrun during drilling?

Notification is not required if drilling is progressing
As soon as unforeseen conditions are encountered, before significant additional costs are incurred (Correct answer)
When the overrun exceeds 50% of the original contract value
Only after project completion when the final invoice is prepared

Correct answer: As soon as unforeseen conditions are encountered, before significant additional costs are incurred

Professional and ethical practice requires notifying the client immediately when unforeseen conditions are encountered so the owner can make informed decisions before significant additional costs accumulate.

Question 10: What is a dashboard in CWD reporting?

An IT-only tool
A physical control panel
A visual display of key metrics for at-a-glance performance monitoring (Correct answer)
A written monthly report

Correct answer: A visual display of key metrics for at-a-glance performance monitoring

A dashboard consolidates important metrics and trends visually for quick assessment of performance status.

Question 11: Which sedimentary rock type is MOST commonly associated with karst aquifer systems?

Granite
Limestone (Correct answer)
Shale
Sandstone

Correct answer: Limestone

Limestone is soluble in slightly acidic groundwater, creating caves, sinkholes, and conduit flow networks characteristic of karst systems.

Question 12: A well driller notices the static water level has permanently dropped 40 feet over 10 years in an area of heavy agricultural irrigation. This most likely indicates:

Pump setting too shallow
Seasonal drought conditions only
Well screen corrosion
Long-term aquifer overdraft from regional pumping exceeding recharge (Correct answer)

Correct answer: Long-term aquifer overdraft from regional pumping exceeding recharge

A permanent multi-decade decline in regional static water levels is the hallmark of aquifer overdraft, where cumulative regional pumping (agriculture, municipal) consistently exceeds natural recharge rates.

Question 13: When drilling near an underground storage tank (UST), what is the PRIMARY risk assessment concern?

Potential cross-contamination of the aquifer (Correct answer)
Equipment corrosion from fuel vapors
Permit processing delays
Increased drilling costs

Correct answer: Potential cross-contamination of the aquifer

USTs can leak petroleum hydrocarbons that may contaminate the aquifer if drilling penetrates contaminated soil or connects pathways to groundwater.

Question 14: Workers' compensation insurance is required in most US states for well drilling companies because:

It is optional coverage for companies with fewer than 5 employees in all states
It covers employee medical costs and lost wages for job-related injuries without requiring fault (Correct answer)
It protects clients from driller negligence
It insures drilling equipment against damage

Correct answer: It covers employee medical costs and lost wages for job-related injuries without requiring fault

Workers' compensation provides mandatory no-fault coverage for employees injured on the job, paying medical expenses and lost wages regardless of who caused the injury, as required by most state laws.

Question 15: Which hazard is most associated with confined spaces in well drilling?

Crowd of people.
Too much space.
Lack of sunshine.
Presence of toxic gases or low oxygen levels (Correct answer)

Correct answer: Presence of toxic gases or low oxygen levels

Confined spaces, such as well shafts or storage tanks, are particularly dangerous in well drilling because they can accumulate hazardous gases like methane or hydrogen sulfide, or have depleted oxygen levels. These atmospheric hazards can quickly lead to unconsciousness, asphyxiation, or poisoning, making proper ventilation and atmospheric monitoring critical before entry.

Question 16: What does professional competency require of a CWD practitioner?

Maintaining current knowledge through continuing education (Correct answer)
Accepting all work regardless of qualifications
Learning only during initial schooling
Relying solely on original training

Correct answer: Maintaining current knowledge through continuing education

Professional competency requires ongoing education, staying current with developments, and practicing only within qualified areas.

Question 17: What is the primary mechanism by which an artesian well flows at the surface without pumping?

The water table is perched above ground level
Hydrostatic pressure in a confined aquifer exceeds the land surface elevation (Correct answer)
Capillary action draws water upward
Tidal forces create upward pressure

Correct answer: Hydrostatic pressure in a confined aquifer exceeds the land surface elevation

A flowing artesian well occurs when the potentiometric surface of a confined aquifer lies above the ground surface at the well location.

Question 18: Which document legally defines the scope of work, payment terms, and liability for a well drilling project?

Well completion report
Permit application
Drilling log
Written contract or work order (Correct answer)

Correct answer: Written contract or work order

A written contract or work order is the legally binding document that specifies the scope of work, pricing, payment schedule, warranties, and liability allocation between the driller and client.

Question 19: When a well screen is corroded beyond rehabilitation, the recommended remedy is:

Add chlorine annually
Increase pump setting depth
Install a whole-house filter only
Install a liner or sleeve, or construct a replacement well (Correct answer)

Correct answer: Install a liner or sleeve, or construct a replacement well

A corroded well screen that cannot be rehabilitated requires either installing a well liner/sleeve to bypass the damaged section or constructing a new replacement well.

Question 20: What is the primary purpose of maintaining accurate job cost records for each drilling project?

To satisfy OSHA inspection requirements
To track employee vacation hours
To compare estimated vs. actual costs, improve future bidding accuracy, and demonstrate profitability per job (Correct answer)
Required for state licensing renewal only

Correct answer: To compare estimated vs. actual costs, improve future bidding accuracy, and demonstrate profitability per job

Job cost records allow drillers to compare actual versus estimated costs for each project, improving the accuracy of future bids and identifying which job types are most profitable.

Question 21: Before lowering rehabilitation tools into a well, the driller should always:

Run the pump at full capacity for 1 hour
Shock chlorinate the well first
Remove the pump and measure the casing ID and depth to obstructions (Correct answer)
Notify the EPA regional office

Correct answer: Remove the pump and measure the casing ID and depth to obstructions

Before any rehabilitation work, the driller must pull the pump and measure the casing inside diameter and depth to any obstructions to ensure tools will fit and not become stuck.

Question 22: During a pump test, 'recovery data' refers to:

Water level measurements taken after pumping stops to track aquifer recharge (Correct answer)
The pumping rate needed to recover target yield
Chemical concentration recovery after treatment
Pump efficiency rating after rehabilitation

Correct answer: Water level measurements taken after pumping stops to track aquifer recharge

Recovery data are water level measurements recorded after pumping ceases, tracking how quickly the aquifer refills the well — this data helps determine aquifer transmissivity using the Theis recovery method.

Question 23: What is the primary function of a gravel pack (filter pack) installed around a well screen?

To stabilize the borehole formation and filter fine particles from entering the well (Correct answer)
To prevent chemical contamination migrating from the surface
To reduce overall well construction costs
To increase hydrostatic pressure in the aquifer zone

Correct answer: To stabilize the borehole formation and filter fine particles from entering the well

A gravel pack stabilizes fine aquifer materials around the screen and acts as a granular filter that passes water while blocking sand and silt.

Question 24: Stream gauging data shows baseflow increases after no recent rainfall. This MOST likely indicates:

Evapotranspiration has increased
Surface runoff is delayed
Groundwater is discharging into the stream (gaining stream) (Correct answer)
The stream is recharging the aquifer

Correct answer: Groundwater is discharging into the stream (gaining stream)

A gaining stream receives groundwater discharge from adjacent aquifers, which can sustain or increase streamflow during dry periods.

Question 25: A change order in a well drilling contract is used to:

Replace the drilling permit after expiration
Document the final well completion for the state
Transfer the contract to a subcontractor
Modify the original scope, schedule, or price due to unforeseen conditions or client requests (Correct answer)

Correct answer: Modify the original scope, schedule, or price due to unforeseen conditions or client requests

A change order formally documents and authorizes modifications to the original contract scope, timeline, or cost when unforeseen site conditions or client-requested changes arise during the project.

Question 26: What is the primary purpose of well redevelopment after installation?

Test for bacterial contamination
Measure aquifer transmissivity
Increase the water table elevation
Remove drilling fluid and fine particles to restore natural permeability (Correct answer)

Correct answer: Remove drilling fluid and fine particles to restore natural permeability

Well redevelopment removes residual drilling fluids and fine particles that clog the formation, restoring the natural permeability around the well screen.

Question 27: When estimating a drilling project, what does 'contingency' typically refer to?

Equipment depreciation allowance
Overhead allocation for office expenses
A percentage added to cover unforeseen costs or risks (Correct answer)
Profit margin built into labor rates

Correct answer: A percentage added to cover unforeseen costs or risks

Contingency is a percentage (typically 5-15%) added to a project estimate to cover unforeseen conditions, cost overruns, or risks that cannot be precisely predicted before drilling begins.

Question 28: What is change management in CWD technology?

Replacing all systems at once
Making changes immediately without review
Monthly password changes
A structured process for evaluating and implementing changes safely (Correct answer)

Correct answer: A structured process for evaluating and implementing changes safely

IT change management ensures changes are evaluated, approved, tested, and implemented in a controlled manner.

Question 29: Polyphosphate sequestering agents added to well water are used to:

Prevent iron and manganese from staining fixtures (Correct answer)
Increase well yield
Remove nitrates
Disinfect the water supply

Correct answer: Prevent iron and manganese from staining fixtures

Polyphosphate sequestering agents chemically bind iron and manganese ions, keeping them in solution and preventing oxidation that causes staining on fixtures and laundry.

Question 30: A well drilled in a valley-fill alluvial aquifer adjacent to a perennial stream is likely to exhibit what behavior?

Exclusively artesian conditions
Complete hydraulic isolation from the stream
Declining yields regardless of pumping rate
Induced recharge from the stream when pumped heavily (Correct answer)

Correct answer: Induced recharge from the stream when pumped heavily

Heavy pumping can reverse the hydraulic gradient between the stream and aquifer, inducing the stream to recharge the aquifer—a process called induced infiltration.

Question 31: Which business structure provides the strongest personal liability protection for a well drilling business owner?

Sole proprietorship
Limited Liability Company (LLC) or Corporation (Correct answer)
Joint venture with no formal agreement
General partnership

Correct answer: Limited Liability Company (LLC) or Corporation

An LLC or Corporation creates a legal separation between the owner's personal assets and business liabilities, providing the strongest protection if the business faces lawsuits or debt.

Question 32: How do regulations differ from standards in CWD practice?

Standards are always stricter
They are the same
Regulations only apply to individuals
Regulations are legally binding; standards are typically voluntary (Correct answer)

Correct answer: Regulations are legally binding; standards are typically voluntary

Regulations are legally enforceable government rules; standards are industry-developed guidelines that may become requirements through adoption.

Question 33: Why is it necessary to develop a well after drilling?

To improve well efficiency and water quality (Correct answer)
To deepen the borehole.
To test the water temperature.
To install the pump.

Correct answer: To improve well efficiency and water quality

Well development is a process performed after drilling to remove fine sediments, drilling fluids, and other debris from the borehole and the surrounding aquifer. This process improves the hydraulic connection between the well and the aquifer, increasing the well's yield and efficiency, and enhancing the quality of the water produced by reducing turbidity and sediment.

Question 34: A step-drawdown test is used primarily to:

Determine aquifer boundaries
Evaluate well efficiency and identify non-linear head losses (Correct answer)
Measure aquifer storativity
Test pump motor amperage

Correct answer: Evaluate well efficiency and identify non-linear head losses

A step-drawdown test pumps a well at sequentially increasing rates to separate aquifer losses from well losses, determining well efficiency and identifying turbulent (non-linear) head losses.

Question 35: What is the purpose of a casing in well drilling?

To reduce drilling time.
To increase water pressure.
To filter the water before pumping.
To line the borehole and prevent collapse (Correct answer)

Correct answer: To line the borehole and prevent collapse

Casing is a large-diameter pipe inserted into a drilled well. Its main purpose is to line the borehole, preventing the surrounding earth and rock from collapsing into the well. It also isolates different water-bearing zones, preventing contamination from surface water or undesirable aquifers, ensuring the structural integrity and water quality of the well.

Question 36: Which type of rock is most likely to form a good aquifer?

Granite
Marble
Sandstone (Correct answer)
Basalt

Correct answer: Sandstone

Good aquifers are typically composed of permeable and porous materials that can store and transmit water effectively. Sandstone, formed from cemented sand grains, possesses both high porosity (ample space between grains) and high permeability (connected spaces allowing water flow). In contrast, granite, basalt, and marble are generally much less porous and permeable, making them poor aquifer materials unless extensively fractured.

Question 37: A certificate of insurance (COI) is typically requested from a well driller by:

A client or property owner before work begins to verify coverage (Correct answer)
The equipment manufacturer
The local health department
The state well driller licensing board

Correct answer: A client or property owner before work begins to verify coverage

Clients and property owners request a COI before work begins to verify that the well driller carries adequate general liability and workers' compensation insurance, protecting the owner from liability.

Question 38: What is the minimum distance typically required between a well and a septic system?

50 feet (Correct answer)
100 feet
10 feet
500 feet

Correct answer: 50 feet

A minimum separation distance between a well and a septic system is essential to prevent contamination of the drinking water supply. Septic systems discharge wastewater containing pathogens and other pollutants into the ground. While specific regulations vary, a general minimum of 50 feet is often recommended to allow for natural filtration and absorption of contaminants in the soil before they can reach the well.

Question 39: What is the primary purpose of using a mud rotary drilling method?

To drill through solid rock formations.
To install casing during drilling.
To stabilize the borehole and remove cuttings efficiently (Correct answer)
To improve groundwater recharge.

Correct answer: To stabilize the borehole and remove cuttings efficiently

In mud rotary drilling, drilling mud (or fluid) is continuously circulated down the drill pipe and back up the annulus. Its primary purposes are to stabilize the borehole walls by creating a filter cake, preventing collapse, and efficiently carrying drill cuttings to the surface. The mud also cools and lubricates the drill bit, extending its lifespan and improving drilling efficiency.

Question 40: The vadose zone is best defined as:

The saturated zone below the water table
The zone of capillary rise just above the water table
The unsaturated zone between the land surface and the water table (Correct answer)
The zone of groundwater discharge to streams

Correct answer: The unsaturated zone between the land surface and the water table

The vadose zone (unsaturated zone) extends from the land surface to the water table and contains both air and water in pore spaces.

Question 41: A driller uses drone-mounted LiDAR to survey a well site before construction. What key benefit does LiDAR provide over traditional ground surveying?

It detects underground aquifer boundaries
It identifies formation lithology from the surface
It creates a precise 3D terrain model for site planning, drainage, and access road design (Correct answer)
It measures borehole deviation during drilling

Correct answer: It creates a precise 3D terrain model for site planning, drainage, and access road design

LiDAR (Light Detection and Ranging) rapidly generates high-resolution 3D point-cloud terrain models, enabling precise site layout, grading plans, and stormwater management design.

Question 42: A well experiencing gradual decline in yield over several years most likely indicates:

Biofouling or mineral encrustation of the screen (Correct answer)
Pump wear only
Seasonal water table fluctuation
Aquifer depletion

Correct answer: Biofouling or mineral encrustation of the screen

Gradual yield decline over years is a classic sign of biofouling (iron bacteria) or mineral encrustation (calcium/manganese deposits) plugging the well screen and formation.

Question 43: General liability insurance for a well drilling contractor primarily protects against:

Employee injury on the job site
Non-payment by clients
Equipment breakdown costs
Third-party bodily injury and property damage claims (Correct answer)

Correct answer: Third-party bodily injury and property damage claims

General liability insurance covers third-party claims for bodily injury or property damage caused by the contractor's operations, such as a rig damaging a client's property or injuring a bystander.

Question 44: Which indicator best signals that a submersible pump is wearing out rather than the well declining?

Pump amp draw increases while yield decreases (Correct answer)
Decreasing static water level
Sand in the water
Water pressure fluctuates with weather

Correct answer: Pump amp draw increases while yield decreases

Increasing amp draw combined with decreasing yield indicates pump impeller wear, as a worn pump draws more current to overcome internal bypass while producing less water.

Question 45: What is the minimum waiting period after shock chlorination before a well can be returned to domestic service according to standard US practice?

12 hours
72 hours regardless of test results
At least 24 hours, plus a clear bacteriological test (Correct answer)
1 hour

Correct answer: At least 24 hours, plus a clear bacteriological test

Standard practice requires waiting at least 24 hours for the chlorine to dissipate and then passing a clear bacteriological test (absent for total coliform and E. coli) before returning the well to service.

Question 46: Which casing material is most appropriate for deep, high-pressure water wells where significant structural loads are anticipated?

Fiberglass-reinforced plastic
Schedule 40 PVC
Carbon steel (Correct answer)
Copper alloy

Correct answer: Carbon steel

Carbon steel casing is used for deep or high-pressure wells because its tensile and compressive strength far exceeds that of thermoplastic materials.

Question 47: A well driller is required to maintain Safety Data Sheets (SDS) on site for which materials?

For all hazardous chemicals present on the job site, regardless of quantity (Correct answer)
For fuels only, as required by EPA
Only for chemical drilling additives used in quantities greater than 50 gallons
Only for chemicals classified as carcinogens

Correct answer: For all hazardous chemicals present on the job site, regardless of quantity

OSHA's Hazard Communication Standard (HazCom 2012) requires SDS availability for all hazardous chemicals in the workplace, with no minimum quantity threshold.

Question 48: What factor primarily determines the appropriate inside diameter of a production well casing?

The geographic location and state jurisdiction
The total depth of the well
The pump size and required yield capacity (Correct answer)
The type of aquifer material encountered

Correct answer: The pump size and required yield capacity

Casing diameter must accommodate the pump bowl assembly and intake pipe while providing sufficient annular clearance for installation and the required flow velocity.

Question 49: What does confined aquifer mean?

A dry rock formation.
An aquifer under pressure between impermeable layers (Correct answer)
An aquifer located near a volcano.
An aquifer with no water.

Correct answer: An aquifer under pressure between impermeable layers

A confined aquifer is an aquifer that is situated beneath a relatively impermeable layer of rock or sediment, known as an aquiclude or confining layer. This overlying layer restricts the vertical movement of water, causing the water within the aquifer to be under pressure. Consequently, the water level in a well drilled into a confined aquifer will rise above the top of the aquifer itself, often resulting in artesian conditions.

Question 50: A well driller's warranty on a new well installation typically covers:

Government-mandated water quality standards permanently
Workmanship defects and materials for a specified period, but not aquifer yield changes (Correct answer)
All pump maintenance for the life of the well
Any future decline in water yield due to drought

Correct answer: Workmanship defects and materials for a specified period, but not aquifer yield changes

A standard well driller's warranty covers defects in workmanship and materials for a defined period (commonly 1 year), but cannot guarantee aquifer yield since that depends on hydrogeologic conditions outside the driller's control.

Question 51: What is the PDCA cycle in CWD quality management?

A one-time checklist
A budgeting method
Plan-Do-Check-Act: an iterative continuous improvement method (Correct answer)
A performance rating system

Correct answer: Plan-Do-Check-Act: an iterative continuous improvement method

PDCA is a continuous improvement cycle: Plan a change, Do implement it, Check the results, Act on findings — then repeat.

Question 52: Glacial outwash deposits are valued as aquifer materials primarily because they consist of:

Fine-grained lacustrine clays
Consolidated ice-contact sediments
Fractured glacial till with secondary porosity
Well-sorted sands and gravels with high permeability (Correct answer)

Correct answer: Well-sorted sands and gravels with high permeability

Glacial outwash is deposited by meltwater streams and consists of well-sorted, coarse-grained sands and gravels that form highly productive aquifers.

Question 53: Which surging method uses a tight-fitting piston to alternately push and pull water through the screen?

Mechanical surging with a surge block (Correct answer)
Overpumping
Jetting
Air surging

Correct answer: Mechanical surging with a surge block

Mechanical surging with a surge block uses a tight-fitting piston (surge block) that is moved up and down to force water back and forth through the well screen, dislodging fine particles.

Question 54: Groundwater age dating using tritium-helium methods is most useful for determining:

The rate of aquifer compaction
The chemical composition of recharge water
Whether groundwater was recharged before or after 1952 (nuclear testing era) (Correct answer)
Depth of the water table

Correct answer: Whether groundwater was recharged before or after 1952 (nuclear testing era)

Tritium from nuclear weapons testing peaked in precipitation around 1963, so its presence (or decay product helium-3) indicates modern recharge after 1952.

Question 55: Regional groundwater flow from recharge areas to discharge areas is driven primarily by:

Precipitation intensity alone
Differences in hydraulic head between topographically high and low areas (Correct answer)
Differences in water temperature
Tidal forces in coastal regions

Correct answer: Differences in hydraulic head between topographically high and low areas

Groundwater flows from areas of high hydraulic head (elevated recharge zones) to areas of low hydraulic head (discharge zones) following the potentiometric gradient.

Question 56: When working near an energized power line during drilling operations, what is the minimum safe approach distance for equipment under 50 kV?

10 feet (Correct answer)
20 feet
50 feet
3 feet

Correct answer: 10 feet

OSHA requires a minimum 10-foot clearance from energized power lines up to 50 kV for equipment and workers.

Question 57: Which factor can lead to groundwater contamination?

Proper well casing.
Wind erosion.
Chemical spills and faulty well construction (Correct answer)
Sunlight exposure.

Correct answer: Chemical spills and faulty well construction

Groundwater contamination occurs when pollutants from the land surface or subsurface migrate into the aquifer. Chemical spills, whether from industrial accidents or agricultural runoff, can leach into the ground. Additionally, faulty well construction, such as inadequate casing or improper sealing, creates direct pathways for surface contaminants to bypass natural filtration and enter the well and aquifer, posing significant risks.

Question 58: What is permeability?

Ability to reflect sunlight.
Ability to allow water to pass through (Correct answer)
Ability to absorb sound.
Ability to conduct electricity.

Correct answer: Ability to allow water to pass through

Permeability is a measure of a material's ability to allow fluids, specifically water, to pass through it. A highly permeable material, such as sand or gravel, allows water to flow easily, which is essential for an aquifer to yield water to wells. While porosity indicates the amount of space, permeability describes how well those spaces are connected to permit water movement.

Question 59: A driller uses a borehole acoustic televiewer (ATV) instead of an optical televiewer in a formation. The primary reason would be:

ATV measures formation porosity directly
ATV works in opaque, turbid, or dark borehole fluids where optical tools fail (Correct answer)
ATV is less expensive to operate in all conditions
ATV only functions above the water table

Correct answer: ATV works in opaque, turbid, or dark borehole fluids where optical tools fail

Acoustic televiewers use ultrasonic pulses to image the borehole wall and function in turbid or opaque water, unlike optical televiewers that require clear water and adequate lighting.

Question 60: What is the minimum recommended height for well casing above finished ground surface as specified by most well construction standards?

8 inches
12 inches (Correct answer)
4 inches
18 inches

Correct answer: 12 inches

A minimum of 12 inches above finished grade is required to prevent surface water and debris from flowing directly into or over the well casing top.

Question 61: Which component is responsible for rotating the drill bit in a cable tool drilling rig?

Walking beam (Correct answer)
Swivel
Drill collar
Kelly bar

Correct answer: Walking beam

In a cable tool drilling rig, the walking beam is a large, oscillating lever that moves up and down. This motion lifts and drops the drill string, causing the drill bit to repeatedly strike the bottom of the borehole. This percussive action breaks up the rock, allowing for drilling in hard formations by crushing and chipping away at the material.

Question 62: What is the primary purpose of well casing in a drilled water well?

To provide a pathway for monitoring groundwater temperature
To reduce construction costs by minimizing excavation volume
To prevent borehole collapse and protect the water supply from contamination (Correct answer)
To increase water flow rates by compressing surrounding formations

Correct answer: To prevent borehole collapse and protect the water supply from contamination

Well casing maintains borehole integrity, prevents collapse, and seals out surface water and contaminants from reaching the aquifer.

Question 63: The primary purpose of a lien waiver signed by a well drilling subcontractor is to:

Release the property owner's land from potential mechanic's liens after payment is received (Correct answer)
Document water quality test results
Authorize additional drilling depth
Transfer equipment ownership

Correct answer: Release the property owner's land from potential mechanic's liens after payment is received

A lien waiver is a document signed by the contractor/subcontractor confirming they have received payment and waiving their right to file a mechanic's lien against the owner's property for that portion of work.

Question 64: What is informed consent in CWD professional practice?

Third-party consent
Verbal agreement only
Having clients sign without explanation
Providing complete information about services, risks, and alternatives for voluntary decisions (Correct answer)

Correct answer: Providing complete information about services, risks, and alternatives for voluntary decisions

Informed consent requires clear, complete information about proposed services, risks, outcomes, and alternatives so clients can make knowledgeable decisions.

Question 65: A well driller operating without a required state license may face which of the following consequences?

Loss of equipment only
Civil fines, stop-work orders, contract voiding, and criminal charges in some states (Correct answer)
A verbal warning only on first offense
Mandatory continuing education only

Correct answer: Civil fines, stop-work orders, contract voiding, and criminal charges in some states

Unlicensed well drilling can result in significant civil penalties, stop-work orders, voiding of contracts (making payment collection impossible), and even criminal misdemeanor charges in many states.

Question 66: The specific capacity of a well is defined as:

Drawdown divided by pumping rate
Pumping rate divided by drawdown (Correct answer)
Total gallons pumped per day
Static water level minus pumping water level

Correct answer: Pumping rate divided by drawdown

Specific capacity is the pumping rate (gpm) divided by the drawdown (ft), expressing how many gallons per minute the well yields per foot of drawdown.

Question 67: When rehabilitating an old well, which test should be performed BEFORE chemical treatment to establish a baseline?

Video camera inspection
Pumping test to measure current specific capacity
pH test of the water
All of the above (Correct answer)

Correct answer: All of the above

Before rehabilitation, a video inspection, pumping test for specific capacity, and water chemistry/pH testing together establish a complete baseline to measure the success of rehabilitation.

Question 68: A well drilling company's overhead costs include which of the following?

Subcontractor costs billed per project
Office rent, insurance premiums, and administrative salaries (Correct answer)
Drill bit costs charged to a specific job
Fuel used directly on a project site

Correct answer: Office rent, insurance premiums, and administrative salaries

Overhead costs are indirect expenses not attributable to a specific project, including office rent, insurance premiums, administrative staff, utilities, and other costs of keeping the business running.

Question 69: Which geologic process is responsible for creating the primary porosity in sandstone aquifers?

Volcanic vesicle formation
Dissolution by acidic water
Tectonic fracturing
Depositional pore spaces between grains (Correct answer)

Correct answer: Depositional pore spaces between grains

Primary porosity in sandstone results from the spaces between sand grains that were preserved during original sediment deposition and cementation.

Question 70: Why is written communication important in CWD practice?

Only for legal disputes
Eliminated by technology
It creates permanent records and ensures clarity for future reference (Correct answer)
Less effective than verbal always

Correct answer: It creates permanent records and ensures clarity for future reference

Written communication creates documented records, provides clarity, and serves as reference material for decisions and actions.

Question 71: Iron bacteria in a well are best characterized as:

Coliform bacteria from surface contamination
Sulfur-reducing anaerobes causing black water
Non-pathogenic bacteria that oxidize iron and form reddish-brown slime (Correct answer)
Pathogenic organisms requiring immediate health advisory

Correct answer: Non-pathogenic bacteria that oxidize iron and form reddish-brown slime

Iron bacteria (such as Gallionella and Leptothrix) are non-pathogenic organisms that oxidize dissolved iron, producing characteristic reddish-brown gelatinous slime that can foul screens and pipes.

Question 72: What is the purpose of data analysis in CWD practice?

Creating attractive charts only
Collecting data regardless of relevance
Replacing professional judgment
Transforming raw data into insights for informed decision-making (Correct answer)

Correct answer: Transforming raw data into insights for informed decision-making

Data analysis examines, cleans, and models data to discover useful information and support decision-making.

Question 73: What does a negative water-level trend in a long-term monitoring well most likely indicate?

Aquifer depletion where withdrawals exceed recharge (Correct answer)
Increased recharge from precipitation
An improvement in water quality
Seasonal variation returning to normal

Correct answer: Aquifer depletion where withdrawals exceed recharge

A persistent downward trend in water levels indicates the aquifer is being mined—long-term withdrawals exceed natural recharge rates.

Question 74: Acid treatment of a water well is most effective for which type of fouling?

Organic matter buildup
Sand infiltration
Iron bacteria colonies
Calcium carbonate and mineral scale deposits (Correct answer)

Correct answer: Calcium carbonate and mineral scale deposits

Acid treatment (typically hydrochloric or muriatic acid) is most effective at dissolving calcium carbonate and mineral scale deposits that block well screens and the surrounding formation.

Question 75: When reviewing a digital pump curve on a manufacturer's software, the intersection of the system curve and the pump curve defines:

The minimum static water level required
The total dynamic head caused by friction losses only
The maximum horsepower the motor can sustain
The operating point — the actual flow rate and head at which the pump will run in the system (Correct answer)

Correct answer: The operating point — the actual flow rate and head at which the pump will run in the system

The intersection of the pump performance curve and the system resistance curve is the operating point, defining the flow rate and total head the pump will deliver in that specific well system.

Question 76: Hydraulic head in a groundwater system is the sum of:

Velocity head and gravity
Specific yield and storativity
Porosity and permeability
Pressure head and elevation head (Correct answer)

Correct answer: Pressure head and elevation head

Hydraulic head (h) = pressure head (p/ρg) + elevation head (z), representing the total mechanical energy per unit weight of groundwater.

Question 77: What minimum annular seal depth is required by most US state regulations for a new domestic well?

20 feet (Correct answer)
5 feet
10 feet
50 feet

Correct answer: 20 feet

Most US state regulations require a minimum grouted annular seal of 20 feet from the surface to prevent contamination from surface water migration down the outside of the casing.

Question 78: What is the first step when responding to an on-site injury?

Wait for instructions.
Ensure the area is safe, then administer first aid (Correct answer)
Report the injury after your shift.
Continue working.

Correct answer: Ensure the area is safe, then administer first aid

The immediate priority in any on-site injury situation is to ensure the safety of the injured person and others, preventing further harm. Once the area is secured and any immediate dangers are controlled, providing prompt first aid can stabilize the injured person and potentially mitigate the severity of the injury before professional medical help arrives.

Question 79: What chemical is commonly used to treat iron bacteria fouling in a domestic water well?

Hydrogen peroxide only
Sodium hypochlorite (chlorine bleach) (Correct answer)
Potassium permanganate
Hydrochloric acid

Correct answer: Sodium hypochlorite (chlorine bleach)

Sodium hypochlorite (chlorine bleach) is the most common chemical used to shock-chlorinate wells to kill iron bacteria and other biological fouling organisms.

Question 80: Which safety measure is essential when operating drilling equipment?

Working alone for faster results.
Avoiding protective gear for flexibility.
Wearing appropriate personal protective equipment (PPE) (Correct answer)
Using equipment without manuals.

Correct answer: Wearing appropriate personal protective equipment (PPE)

Operating drilling equipment involves significant hazards, including heavy machinery, rotating parts, and potential exposure to dust and chemicals. Wearing appropriate Personal Protective Equipment (PPE), such as hard hats, safety glasses, hearing protection, gloves, and steel-toed boots, is essential to protect workers from injuries and ensure a safe working environment, minimizing risks on the job site.

Question 81: What does the hierarchy of controls prioritize as the MOST effective means of controlling a drilling site hazard?

Administrative controls (rotating job assignments)
Substitution with a less hazardous material
Personal protective equipment (PPE)
Elimination of the hazard (Correct answer)

Correct answer: Elimination of the hazard

The hierarchy of controls ranks elimination first because completely removing the hazard provides the highest level of protection with no residual risk.

Question 82: GIS (Geographic Information System) mapping software is used by well drillers and hydrogeologists to:

Perform downhole geophysical logging
Calculate drill bit weight-on-bit requirements
Design the electrical wiring for submersible pump controls
Spatially analyze well locations, aquifer data, and regulatory setback compliance (Correct answer)

Correct answer: Spatially analyze well locations, aquifer data, and regulatory setback compliance

GIS software overlays well locations, aquifer boundaries, contamination plumes, land use, and regulatory setback zones to support spatial decision-making and compliance analysis.

Question 83: Which depositional environment typically produces laterally discontinuous, heterogeneous aquifer units?

Marine carbonate platform
Aeolian dune field
Alluvial fan and braided river systems (Correct answer)
Deep ocean basin

Correct answer: Alluvial fan and braided river systems

Alluvial fans and braided streams deposit sediments in rapidly shifting channels, creating complex interbedded layers of varying grain size and permeability.

Question 84: What term describes the pressure surface to which water in a confined aquifer will rise in a tightly cased well?

Capillary fringe
Water table
Piezometric surface (Correct answer)
Saturated zone

Correct answer: Piezometric surface

The piezometric (potentiometric) surface represents the hydraulic head in a confined aquifer and is the level to which water rises under artesian pressure.

Question 85: What is the primary concern with upconing in a coastal aquifer?

Subsidence of the land surface
Upward movement of the freshwater-saltwater interface toward a pumping well (Correct answer)
Vertical recharge being blocked
Loss of artesian pressure

Correct answer: Upward movement of the freshwater-saltwater interface toward a pumping well

Upconing occurs when pumping draws the denser saltwater interface upward beneath a well, potentially leading to saltwater intrusion and well contamination.

Question 86: A driller's 'mobilization cost' in a bid refers to:

Expense of moving equipment to and setting up at the job site (Correct answer)
Disposal cost for drill cuttings
Cost of drilling permits
Labor cost per foot of drilling

Correct answer: Expense of moving equipment to and setting up at the job site

Mobilization cost covers the expense of transporting the drilling rig and equipment to the job site and setting it up, which is typically a fixed charge separate from per-foot drilling costs.

Question 87: What should be done before starting drilling equipment?

Ask the supervisor only.
Check equipment, surroundings, and perform safety checks (Correct answer)
Wear casual clothes.
Immediately start the machine.

Correct answer: Check equipment, surroundings, and perform safety checks

Before operating any drilling equipment, it is crucial to conduct thorough safety checks to prevent accidents. This includes inspecting the machinery for any damage or malfunctions, assessing the immediate work area for potential hazards, and ensuring all safety guards and emergency stops are functional. These proactive steps minimize risks to personnel and equipment.

Question 88: A perched water table occurs when:

Tidal fluctuations raise water levels seasonally
The main water table is under artesian pressure
Groundwater accumulates above a localized impermeable layer above the regional water table (Correct answer)
Two aquifers merge at depth

Correct answer: Groundwater accumulates above a localized impermeable layer above the regional water table

A perched aquifer forms when a lens of low-permeability material intercepts downward-percolating water, creating a localized saturated zone above the main water table.

Question 89: Which type of bond protects a project owner if a licensed well driller fails to complete the contracted work?

Fidelity bond
Equipment floater bond
Pollution liability bond
Surety performance bond (Correct answer)

Correct answer: Surety performance bond

A surety performance bond guarantees that if the contractor defaults or fails to complete the project, the surety company will either complete the work or compensate the owner for losses up to the bond amount.

Question 90: When bidding a well drilling project on a time-and-materials basis, the contractor's risk compared to a lump-sum bid is:

Lower, because actual costs plus markup are reimbursed (Correct answer)
Higher, because unknown formations may increase costs
Higher due to fixed overhead recovery
The same regardless of formation conditions

Correct answer: Lower, because actual costs plus markup are reimbursed

In a time-and-materials contract, the contractor is reimbursed for actual costs plus an agreed markup, so unexpected formation difficulties are passed to the owner, reducing the contractor's financial risk.

Question 91: A driller is working adjacent to an active agricultural field. Which risk is MOST specific to this setting?

Volcanic gas emissions
Pesticide and fertilizer contamination of shallow groundwater (Correct answer)
Salt water intrusion from the ocean
Rock fall from nearby cliffs

Correct answer: Pesticide and fertilizer contamination of shallow groundwater

Agricultural chemicals including nitrates, herbicides, and pesticides commonly leach into shallow aquifers and pose contamination risk to new wells drilled nearby.

Question 92: Which hazard classification applies to a drilling site located within a 100-year floodplain?

Moderate risk — only affects surface equipment
Low risk — floods rarely occur
High risk — well construction standards must address flood inundation (Correct answer)
No special classification required

Correct answer: High risk — well construction standards must address flood inundation

Drilling in a 100-year floodplain is high-risk because floodwaters can inundate and contaminate a newly constructed well, requiring elevated wellhead designs.

Question 93: What is trend analysis in CWD reporting?

Predicting exact futures
Examining data over time to identify patterns and changes (Correct answer)
Analyzing fashion trends
Comparing single data points

Correct answer: Examining data over time to identify patterns and changes

Trend analysis examines historical data to identify patterns, directions, and rates of change.

Question 94: What does a 'stop-work authority' policy mean in the context of drilling site safety?

Stop-work applies only to mechanical failures
Only the site foreman can pause drilling operations
Work stoppages require written approval from the client
Any worker can halt work when they observe an imminent hazard without fear of reprisal (Correct answer)

Correct answer: Any worker can halt work when they observe an imminent hazard without fear of reprisal

Stop-work authority empowers every employee to halt operations immediately upon identifying a serious hazard, creating a culture where safety supersedes production pressure.

Question 95: For tax purposes, a well drilling company's heavy equipment is typically depreciated using which method under US tax law?

Market value appraisal annually
First-in, first-out (FIFO) method
MACRS (Modified Accelerated Cost Recovery System) with Section 179 expensing options (Correct answer)
Straight-line depreciation only

Correct answer: MACRS (Modified Accelerated Cost Recovery System) with Section 179 expensing options

Under US tax law, business equipment is depreciated using MACRS, which allows accelerated depreciation over defined asset class lives, and Section 179 allows immediate expensing of qualifying equipment purchases.

Question 96: Why is it important to use drilling mud during rotary drilling?

To improve bit speed.
To prevent the rig from overheating.
To provide lubrication only.
To cool the bit and stabilize the borehole (Correct answer)

Correct answer: To cool the bit and stabilize the borehole

Drilling mud serves multiple vital functions in rotary drilling. It cools the drill bit, preventing overheating and extending its lifespan, and lubricates the drilling components. Crucially, it also stabilizes the borehole walls by forming a filter cake, preventing collapse and ensuring the integrity of the well during drilling operations.

Question 97: What is the role of a well screen in a drilled well?

To allow water entry while filtering out sediments (Correct answer)
To cap the well permanently.
To pump water into the aquifer.
To block all external fluids.

Correct answer: To allow water entry while filtering out sediments

A well screen is a specialized pipe section with precisely sized openings (slots or perforations) installed in the water-bearing zone of a well. Its primary function is to allow groundwater to flow into the well while effectively filtering out sand, gravel, and other fine sediments. This protects the pump from abrasion and ensures the production of clean, sediment-free water.

Question 98: What is the primary purpose of a code of ethics in CWD practice?

To establish professional conduct standards and guide ethical decision-making (Correct answer)
To define standard office hours
To determine salary structures
To set pricing for professional services

Correct answer: To establish professional conduct standards and guide ethical decision-making

A code of ethics provides a framework of professional values and behavioral standards that guides practitioners in ethical decisions while maintaining public trust.

Question 99: According to AWWA A100, what is the minimum recommended thickness for an annular grout seal around well casing?

1 inch
1.5 inches
2 inches (Correct answer)
3 inches

Correct answer: 2 inches

AWWA A100 specifies a minimum 2-inch annular grout thickness to ensure a complete, void-free seal that prevents contaminant migration along the borehole wall.

Question 100: What is the primary purpose of a sanitary well seal installed at the top of a well casing?

To prevent insects, rodents, and surface water from entering the well (Correct answer)
To serve as a measurement port for water level monitoring
To allow air circulation and prevent pressure buildup inside the casing
To increase well yield by maintaining positive casing pressure

Correct answer: To prevent insects, rodents, and surface water from entering the well

The sanitary well seal creates a watertight, vermin-proof closure at the casing top, preventing biological and physical contaminants from entering the well.

NGWA Certified Well Driller (CWD)

The NGWA Certified Well Driller (CWD) certification validates professional competency in water well drilling, covering well construction, geology, groundwater hydrology, well maintenance, business operations, and professional standards. Candidates must pass the general drilling exam plus at least one specialized drilling exam with a score of 70% or better.

100

Questions

120 min

Time Limit

70%

To Pass

Checking for saved progress...

Exam Rules

You can skip questions and return to them later
Flag questions for review before submitting
No feedback shown until you submit the entire exam
Unanswered questions count as wrong — answer everything
10 pretest questions are mixed in and don't affect your score
Timer auto-submits when time runs out
Your progress is auto-saved every 30 seconds

These practice questions were written with AI tools. They are not real exam questions. Exam facts are checked against the official sources listed below. Not reviewed by a subject-matter expert. Editorial policy

Sources & references

Exam facts on this page (fees, format, dates, passing scores) are checked against these official sources; the date is our last check. Editorial policy

groundwaterweek.com — Exam dates, registration deadline, exam information · verified Oct 2026
ngwa.org — Fees, exam format, passing score, score release, test dates, time limit, test delivery, retake policy, eligibility · verified Oct 2026
test-takers.psiexams.com — Retake fee · verified Oct 2026