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Zelen provides engineering and consulting services in the southwest including Arizona, California, and New Mexico.

Zelen is a small firm that is equipped to handle larger projects normally handled by larger, national consulting and engineering firms.


Our clients vary from small, family businesses to school districts and oil companies. Zelen’s ability to manage a diverse array of projects from small to large, is found in its employees and associates who pride themselves in their work and provide personalized service.

Our company philosophy is simple, treat the client as you would want to be treated, with respect and by experienced individuals who understand a client’s needs, not the billability requirement of a corporate office.




Michael Kazz

Principal Engineer

B.S. M.S. Agricultural and Biosystems Engineering, The University of Arizona.  Mr. Kazz has a wide range of engineering experience including Process Engineering, Mechanical Engineering (Vibration and Acoustic) and Environmental Engineering.  A National Science Foundation Fellow, Mr. Kazz is one of Zelen's key administrators and is the Customer Service Manager.

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Dennis Krantz LLC


B.S. Geology, University of Wisconsin, M.S. Geology, Southern Illinois University.  Mr. Krantz has a background as a mining geologist with over 20 years experience and has been in environmental consulting for over 20 years as well.  He is the senior technical lead for risk based corrective action projects and Corrective Action Plan development.  He is also involved in directing field investigations.


Roksolana Tourkevich

Chief Financial Officer

B.S. Molecular and Cellular Biology, The University of Arizona.  Mrs. Tourkevich is chief financial administrator for the company.  She has over 17 years experience in environmental consulting and fiscal management.


Helen Giesel

Office Manager

M.A. Social Sciences, The University of Arizona.  Mrs. Giesel is responsible for report review and is the reimbursement coordinator.

Certifications and Registrations

Arizona Registrar of Contractors, ROC207067

State of Arizona, Board of Technical Registration, Firm Registration Number 11402

Arizona Department of Environmental Quality, Consultant Qualification

Arizona Department of Environmental Quality, Permanent Tank Service Provider Certification

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