Exam A/B is a 50-question, one-hour, closed-book exam with a 70 percent minimum passing score, and the PSI outline shows most questions fall under constructing the water well. Study the percussion cycle as a mechanism, not a tool list; practice recognizing method differences and computing specific capacity with same-time readings; then confirm the CWD eligibility rules, which require passing the General Drilling exam plus a specialized drilling exam within one 12-month period.
What Exam A/B is and where it fits
Exam A/B: Cable tool drilling is a specialized drilling exam in NGWA's contractor certification program. To earn the Certified Well Driller designation, you must pass the General Drilling exam and at least one specialized drilling exam, both within one 12-month period.
NGWA's contractor certification program is voluntary and national. The organization describes it as the only national certification program for contractors and pump installers in the groundwater industry, and notes that many state agencies use the same exams as part of their own licensing requirements. Certification and state licensure remain separate processes.
The CWD credential requires two exams at 70 percent or better each: the general drilling exam plus a specialized drilling exam such as A/B. NGWA's current exam page also lists other specialized drilling options, including air rotary, mud rotary, reverse circulation, jetting and driving wells, and augering and monitoring.
This guide covers the combined A/B cable-tool category. The required General Drilling exam has its own content outline; taking another specialized exam does not replace that general exam.
Official sources used: Groundwater | NGWA Certification exams — Certification Exams page, NGWA; Groundwater | NGWA Certification for contractors — Contractor certification page, NGWA
Format and the official question breakdown
Exam A/B has 50 questions with a one-hour time limit and a 70 percent minimum passing score, and it is closed book. The PSI bulletin's content table breaks those questions across six duty areas.
No NGWA approval is needed to sit an exam; certification eligibility and application are separate. The allocation below is from PSI’s September 2022 candidate bulletin.
The weights tell you where preparation time pays off. Constructing the water well accounts for 30 of the 50 questions, so that duty area deserves the largest share of your study, with well development next at 7 questions.
Each row is a duty area, not a guaranteed question-order or subtopic list. Use the weights to budget time, and NGWA's recommended study guides for depth.
| Duty area | Questions |
|---|---|
| Mobilize for the site | 3 |
| Construct water well | 30 |
| Rehabilitate wells | 4 |
| Develop wells | 7 |
| Decommission wells | 3 |
| Demobilize the site | 3 |
Official sources used: PSI NGWA candidate information bulletin — Visually checked content tables, pages 5-7, dated May 2022
Know the method, not just the tool names
Cable tool drilling is the percussion method: a heavy chisel-shaped bit is repeatedly raised and dropped, shattering rock, and the resulting slurry is removed with a bailer. Rotary methods cut differently and circulate fluid or air, so recognizing the mechanism is what separates A/B content from other specialized exams.
The percussion method alternately raises and drops a heavy weight equipped with a chisel bit. It shatters rock at the bottom of the hole; the rock mixes with water into a slurry that a bailer removes.
Contrast this with the rotary family. The hydraulic rotary method rotates a drill pipe with a drag or roller bit, circulating fluid down the pipe and up the annular space to cool the bit and remove cuttings; the reverse rotary variant circulates down the annulus and up the pipe. The air rotary method is similar but uses air instead of mud as the drilling fluid.
The original example below asks you to recognize the mechanism from a short log. Compare the cutting action and the way cuttings are removed.
Practice exercise
A drilling log describes a rig that repeatedly raises and drops a heavy, chisel-shaped bit on a line. Crushed rock at the bottom of the hole mixes with water into a slurry, and a crew removes that slurry in batches with a bailer. No fluid is circulated continuously through the bit. Which well construction method does this describe, and which two observations in the log identify it?
Show answer
The method is cable tool drilling, commonly called the percussion method. The identifying observations are the repeated raising and dropping of a heavy chisel-shaped bit that shatters the formation, and removal of the cuttings-and-water slurry in batches with a bailer.
By definition, the percussion method cuts by impact: a heavy weight with a chisel bit is alternately raised and dropped, shattering rock at the bottom of the hole. The shattered rock mixes with water into a slurry that a bailer removes. Rotary methods instead rotate a bit and circulate fluid or air to lift cuttings continuously, so a log describing batch bailing with no circulation points to cable tool, not to hydraulic rotary or air rotary.
Official sources used: USGS Basic Ground-Water Hydrology — Water-Supply Paper 2220 (1983), selected pages 52, 53, 58
Where to focus your study time
Build your plan around the duty areas in the PSI table, use the industry task chart to see how the duty areas connect to real work, and prepare with the materials NGWA recommends for all drilling exams.
Give the most time to constructing water wells, which carries 30 of the 50 questions, then to well development with 7. Mobilization, rehabilitation, decommissioning, and demobilization together account for 13 questions, so cover each at least once rather than skipping the small rows.
The NGWA task analysis chart for drilling contractors and operators maps major duties from assessing client needs through close out, and catalogs the equipment and knowledge the profession itself lists, including drill bits, casing, bailers, screens, and the math and geology behind them. It is a job task analysis, not a procedure manual, so use it to check coverage, not as a how-to guide.
NGWA recommends specific texts for all drilling exams, including Groundwater & Wells, third edition, and the Manual of Water Well Construction Practices, third edition, and publishes a Professional Designations Information and Study Guide covering all exams. NGWA University also offers self-paced online training for the general drilling exam with knowledge checks and study guides.
A workable sequencing, as study advice: read the duty areas first to see the whole job, study construction and development in depth through your chosen text, then use a timed 50-question practice run to check your pacing for a one-hour exam.
- Start with the 30-question construction duty area and the 7-question development area.
- Scan the task analysis chart for duty areas your field experience has not covered.
- Choose at least one NGWA-recommended drilling text and work the construction and development chapters first.
- Finish with timed practice so 50 questions in one hour feels routine.
Official sources used: Groundwater | NGWA Certification exams — Certification Exams page, NGWA; PSI NGWA candidate information bulletin — Visually checked content tables, pages 5-7, dated May 2022; Drilling contractors and operators — DACUM Research Chart, NGWA/CETE-OSU, June 2003
The calculation worth drilling: specific capacity
Specific capacity is yield per unit of drawdown: divide the pumping rate by the drawdown at the same time during the test. It is a clean arithmetic skill, and knowing its limits prevents misreading it.
Two habits matter. First, divide the pumping rate at any time during the test by the drawdown at that same time, so the two readings share an elapsed time. Second, do not stretch the result beyond its definition: a specific capacity figure alone cannot prove a well's sustainable yield or select a pump.
The exercise below uses the definition directly. Work it before reading the answer, and notice how the comparison before and after development is interpreted strictly in terms of the ratio.
Practice exercise
During a pumping test, a well produces 24 gallons per minute with a pumping level 30 feet below static; both readings are taken at the same elapsed time. Compute the specific capacity. After a development program, the same well at the same elapsed time yields 30 gallons per minute with 12 feet of drawdown. Compute the new specific capacity and state what the comparison does and does not show.
Show answer
Before development: 24 ÷ 30 = 0.8 gallons per minute per foot of drawdown. After development: 30 ÷ 12 = 2.5 gallons per minute per foot. The higher ratio means the well yields more water per foot of drawdown after development, but the figures alone do not prove sustainable yield or determine a pump choice.
Divide each pumping rate by its corresponding drawdown: 24/30 = 0.8 and 30/12 = 2.5 gpm/ft. The second observation has a higher flow-to-drawdown ratio at the stated elapsed time. That comparison does not identify the cause of the change or establish long-term yield or pump sizing.
Official sources used: USGS Basic Ground-Water Hydrology — Water-Supply Paper 2220 (1983), selected pages 52, 53, 58
Eligibility and the path after passing
You must be at least 20 years old with at least 24 consecutive months of full-time drilling or pump installation experience, pass the two required exams within one 12-month period at 70 percent or better, and submit references, an agreement form, and an affidavit.
The experience requirement is full-time and consecutive, and the two exams for your designation, such as General Drilling plus Exam A/B for the CWD, must be passed within one 12-month period. Planning your two exam dates inside that window is part of preparation.
Beyond exams and experience, NGWA requires written references verifying your experience from two professional contacts who are not affiliated with your current company, plus an agreement form and an affidavit for the current year. Application materials must be received within 12 months of the qualifying exam session, so the exam pass date starts a clock on your paperwork too.
Because NGWA certification is voluntary and separate from state licensing, check your state's own contractor or well driller licensing requirements independently. The organization notes that numerous state agencies have adopted these tests for their own programs, which can make the same exam count toward more than one goal.
Official sources used: Groundwater | NGWA Certification for contractors — Contractor certification page, NGWA
Scheduling and exam day
Exams are offered year-round at more than 400 PSI test centers nationwide, scores are issued immediately after completion, and accommodations can be arranged through NGWA.
PSI Services administers the online exams, and scheduling is done through PSI's website or by phone. Because you choose when and where to test, you can set your A/B date to leave room for the General Drilling exam within the same 12-month period.
Scores are issued immediately following exam completion, and you should collect your score report at the test center before leaving. NGWA can reissue scores for a fee, but scores are never issued over the phone.
If you need special accommodations, contact NGWA by phone or email first; NGWA records your information, sends approval to PSI, and PSI then contacts you to complete registration. All testing centers are ADA compliant.
Before test day, confirm both required exam passes can fall within one 12-month period, review the duty-area table, and plan to collect your score report.
- Schedule through PSI's website or by phone, year-round.
- Collect your score report at the test center before leaving.
- Request accommodations through NGWA before completing PSI registration.
- Keep both required CWD exams inside one 12-month window.
Official sources used: Groundwater | NGWA Certification exams — Certification Exams page, NGWA
Official sources used
Key exam facts: