Free Well Drilling (C-57) Examination Practice Questions

Sample Practice Questions

Try these 10 sample questions from the Well Drilling (C-57) Examination practice bank. Each includes the answer and explanation. Continue with the interactive practice above to review the full question set.

1. 1A proposed domestic well site has an ordinary septic tank and leach field nearby. What minimum horizontal separation is generally considered adequate under California's well standards?

   1. A. 50 feet
   2. B. 100 feet
   3. C. 150 feet
   4. D. 200 feet

   Answer: B

   Explanation: The controlling source states “Watertight septic tank or subsurface sewage leaching field”; California DWR lists 100 feet for both a watertight septic tank and a subsurface sewage leaching field, so the well should be sited at least that far away.

   Reference: Part II. Water Well Construction — Part II, Section 8.A, Table 1

2. 2For a community water well, which upper-annular sealing depth should be selected when no approved exception applies?

   1. A. 10 feet
   2. B. 20 feet
   3. C. 30 feet
   4. D. 50 feet

   Answer: D

   Explanation: The controlling source states “Community water supply wells”; California requires the annular seal for community water-supply wells to extend at least 50 feet below ground surface unless an authorized alternative applies.

   Reference: Part II. Water Well Construction — Part II, Section 9.B.1

3. 3A contractor wants to use one monitoring well to screen two aquifers of different water quality. What is the principal California concern?

   1. A. The well may interconnect the aquifers
   2. B. The casing will be too visible
   3. C. The surface slab will cure too fast
   4. D. The pump motor will draw less current

   Answer: A

   Explanation: The controlling source states “shall not have openings in multiple water-bearing units”; Monitoring-well construction must prevent vertical movement of water between zones; a multilevel completion cannot be allowed to create an interaquifer pathway.

   Reference: Part II. Monitoring Well Construction — Part II, Section 12.B, Multiple Screens

4. 4After installing a pump in a domestic well, when must the well be disinfected?

   1. A. Only if the motor is three-phase
   2. B. Before the well returns to service
   3. C. After one year of operation
   4. D. Only when the casing is steel

   Answer: B

   Explanation: The controlling source states “when work is done on the pump”; DWR requires domestic-use wells to be disinfected after work is done on the pump and before the well is placed back in service.

   Reference: Part II. Water Well Construction — Part II, Section 11

5. 5Repair work leaves the domestic-well casing temporarily open while the pump is away. What must protect the opening?

   1. A. A secure temporary cover
   2. B. An open rag
   3. C. Loose drill cuttings
   4. D. A surface-water hose

   Answer: A

   Explanation: The controlling source states “adequately covered”; California requires an unattended well under repair to have a temporary cover that prevents entry of contaminants, people, and animals.

   Reference: Part III. Destruction of Water Wells — Part II, Section 19

6. 6A well's yield has declined because mineral scale is blocking the screen. Which activity is rehabilitation rather than destruction?

   1. A. Treating and developing the well to restore performance
   2. B. Filling the bore from bottom to top
   3. C. Removing the casing five feet below grade
   4. D. Sealing every water-bearing zone permanently

   Answer: A

   Explanation: The controlling source states “well rehabilitation”; California treats work intended to restore a well's usefulness, such as chemical or mechanical cleaning followed by development, as rehabilitation.

   Reference: Part II. Monitoring Well Construction — Part II, Section 18

7. 7The rig must be moved across the site with drill steel and loose tools on the mast. Which preparation is required?

   1. A. Leave the tools loose for quick access
   2. B. Secure the tools and place the mast in a safe position
   3. C. Raise the mast fully
   4. D. Disconnect the service brake

   Answer: B

   Explanation: The controlling source states “drill steel, tools, and other equipment shall be secured”; California drilling rules require drill steel, tools, and other equipment to be secured and the mast placed in a safe position when moving a drill.

   Reference: California Code of Regulations, Title 8, Section 7005. Drilling Operations. — Title 8, section 7005(i)

8. 8A driller is laying out a water well near a sanitary sewer made of approved watertight pipe. Which separation shown in the California standards applies?

   1. A. 25 feet
   2. B. 50 feet
   3. C. 100 feet
   4. D. 150 feet

   Answer: B

   Explanation: The controlling source states “Any sewer (sanitary, industrial, or storm; main or lateral)”; DWR's separation table assigns 50 feet to sanitary, industrial, and storm sewers when approved watertight pipe is used.

   Reference: Part II. Water Well Construction — Part II, Section 8.A, Table 1

9. 9Before positioning a rig, the crew discovers an unmarked underground utility crossing the setup area. What should occur first?

   1. A. Probe with the drill string
   2. B. Start with reduced rotation
   3. C. Establish the utility location before drilling
   4. D. Increase drilling-fluid viscosity

   Answer: C

   Explanation: The controlling source states “underground installations”; California excavation safety practice requires underground installations to be located before excavation; slower drilling does not make an unknown utility safe.

   Reference: Cslb Law Reference 2026 — Title 8, section 1541(b), underground installations

10. 10A monitoring-well seal is being designed around casing. What minimum radial annular thickness is ordinarily required for sealing material?

    1. A. One-half inch
    2. B. One inch
    3. C. Two inches
    4. D. Six inches

    Answer: C

    Explanation: The controlling source states “A minimum of two inches of sealing material”; California's monitoring-well construction standard ordinarily requires at least two inches of sealing material around the casing.

    Reference: Part II. Monitoring Well Construction — Part II, Section 9.C, Radial Thickness of Seal