Geothermal Driller (CVCLD)

Certified Vertical Closed Loop Driller

Advances in geothermal technologies and their usage created the need for a specific voluntary certification designation for geothermal drillers. NGWA responded to this need with the designation of Certified Vertical Closed Loop Driller (CVCLD).

The CVCLD is considered an independent designation from the CWD or CWD/PI. The designation reflects an individual who has passed a written exam administered by NGWA that evaluates an individual’s knowledge of the skills and competencies associated with constructing a loop well.

Tax credit certainty has long been elusive for the industry, but, finally, as the credits are now good through the year 2034, it has leveled the playing field for geothermal to be more competitive with a traditional HVAC system. Therefore, the need for CVCLDs to drill and install geothermal systems will only increase in the ensuing years.



  • Applicant must be at least 20 years old.
  • Applicant must have 24 consecutive months experience constructing loop wells or conventional water supply wells.
  • Applicant must pass the 75 multiple-choice question Vertical Closed Loop (VCL) exam.
  • Applicant must submit the application forms, which consist of the forms described below:
    • Certification Agreement Form — applicant agrees to adhere to the statutes of the NGWA Voluntary Certification Program and its policies.
    • Candidate Reference Form — applicant must provide the names of two references who can verify experience.
    • Current Affidavit — a signed document claiming the individual has never been convicted of any civil or criminal legal action as a result of professional activities relating to geothermal applications.

Exam information

The exam encompasses the skills and competencies reflected on the geothermal vertical closed loop drilling operations DACUM.

Study materials for the exam include NGWA’s Guidelines for the Construction of Loop Wells for Vertical Closed Loop Ground Source Heat Pump Systems and Lexicon of Groundwater and Water Well System Terms, as well as Groundwater & Wells, third edition. For more information about other NGWA-recommended study materials, visit the certification study materials section of the online NGWA bookstore.

Visit PSI’s website​ to schedule your exam and to find scheduling information, or call PSI at (855) 579-4642.

VCL exam fees

  • NGWA members: $125
  • Nonmembers: $300