Our Team


Our providers share a commitment to outstanding and compassionate patient care. Pacific Redwood Medical Groups has managed the emergency department at Ukiah Valley Medical Center for over 25 years and continues to do so in collaboration with Adventist Health.


Brandon Begley, DO
Georgina Calderon, MD MPH

Dr. Calderon completed medical school at the University of California San Francisco and residency in Emergency Medicine at Alameda County Medical Center- Highland Hospital. She earned her Masters Degree in Public Health from Johns Hopkins Bloomberg School of Public Health and her undergraduate BA in Chemistry and Political Science at Williams College.

Prior to joining PRMG, she served as Country Director for sidHARTe- part of the Columbia University Mailman School of Public Health- in Rwanda, where her efforts focused on health system strengthening by providing technical expertise to the Rwandan Ministry of Health to develop robust emergency care systems. Dr. Calderon has worked in a number of international settings, including Syria, Liberia, Honduras, Micronesia and the Palestinian Territories and continues to consult for the WHO on emergency medicine delivery systems in low-resource environments.

As faculty of the AHUV Family Medicine Residency program, she leads the emergency medicine and point-of-care ultrasound curriculums and is the Director of Emergency Ultrasound Services for the Emergency Department. She currently serves as the Chief Medical Officer for PRMG.

She serves on the Board of Directors for the Sonoma-Mendocino-Lake County Medical Association and Corazon-Healdsburg.

Dr. Calderon is Board Certified in Emergency Medicine.

Drew Colfax, MD

Dr. Colfax moved to Mendocino County with his family in 1973. He left to attend Harvard College, where he graduated with magna cum laude and, subsequently, received a Rockefeller fellowship which took him to North and West Africa for 18 months. Upon his return, he attended the University of Michigan, where he received a MA in Anthropology, and Juris doctorate. A multiyear stint as an attorney in Alabama representing people under a sentence of death eventually led him back to medical school.

Gary Fausone, MD

Dr. Fausone was born and raised in San Francisco and attended UC Santa Barbara where he received a BS in Genetic Engineering. After spending two years at the Salk Institute for Biological Studies, he attended McGill Medical School in Montreal. He completed his residency in Emergency Medicine at Metropolitan Hospital in Manhattan. Dr. Fausone is a diplomate with Board Certification in Emergency Medicine.

Mike Hausberger, DO

Dr. Hausberger earned his BS in Biology from SUNY Geneseo in 2010 and Doctor of Osteopathic Medicine from West Virginia Osteopathic School in 2014. He completed his
Emergency Medicine residency at Ohio Valley Medical Center Wheeling, where he was Chief Resident.

He became ABEM Board Certified in 2019.

Dr. Hausberger’s hobbies include weightlifting, tennis, farming, investing, reading, and hiking all over the world with his wife and little girl.

Duncan Johnston, MD

Dr. Johnston is a Northern California native who graduated from UC Davis with a BS in Genetics in 2007. He attended medical school at UC Davis and completed his Emergency Medicine residency at the University of Arizona. He is Board-Certified in Emergency Medicine.

He joined PRMG in 2016 and currently works at AHUV, AHHM and AHMC. He is the Vice Chief of Staff, the Emergency Department Director and the Trauma Director for AHUV. He previously served as the Chair of Infection Prevention and Pharmacy and Therapeutics.
Dr. Johnston lives in Ukiah with his family and is passionate about his work.

Ilan Kolkowitz, MD

Dr. Kolkowitz grew up in Northern California and went to Stanford University for his undergraduate degree.

He attended UC San Diego for medical school and completed his Emergency Medicine residency at the University of Wisconsin, where he also completed a Global Health fellowship.

Dr. Kolkowitz currently serves as Co-Medical Director of the Emergency Department at the Mendocino Coast Hospital and serves on the Medical Executive Committee.

Debbie Marks, MD

Dr. Marks attended Medical School and completed her Emergency Medicine Residency at Loma Linda University. She is Board Certified in Emergency Medicine.

Dr. Marks joined PRMG in 2006 and has served as Emergency Department Director and subsequently was elected as the CEO for PRMG, and served in that role for six years.

As part of the Medical Staff, she serves on the Credentials Committee, the CME Committee and the Medical Executive Committee for several years at AH Ukiah Valley.

Martha Montgomery
Martha Montgomery, MD
Kellie Olson, MD

Dr. Olson, attended medical school at Loma Linda University and completed her residency in Emergency Medicine at St John Hospital.

She is Board Certified in Emergency Medicine.

E. Xavier Ortiz, MD
Dr. Erica Valdovinos, MD

Dr. Valdovinos trained in Emergency Medicine at Alameda Health System (Highland Hospital) in Oakland, California. She attended medical school at the University of California San Francisco and graduated from UC Berkeley with a degree in English. She is a diplomate with Board Certification in Emergency Medicine.

Jennifer Zernec, DO

Dr. Zernec, completed her BS in Exercise and Health Sciences from Alma College and subsequently graduated from Midwestern University School of Osteopathic Medicine.

She completed her Emergency Medicine residency at Ohio Valley Medical Center, where she was Chief Resident. She is Board certified in Emergency Medicine.

Dr. Zernec enjoys spending my time playing soccer and tennis, weightlifting and hiking and has a passion for travelling with my husband and daughter.

Advanced Practice Providers

Noah Chutz, PA

Mr. Chutz is a Physician Assistant who practices Emergency and Addiction Medicine throughout Northern California. His undergraduate degree is from the University of California, Berkeley where he studied natural resource management with an emphasis on forestry, and later earned a dual Masters Degree in Sustainable Development and International Affairs from American University in Washington, DC as well as the United Nations Mandated University for Peace in Costa Rica.

Gretchen Duran, PA

Ms. Duran has a degree in Physician Assistant Studies from Stanford University. She has a Master’s in Education from Grand Canyon University and a Bachelor of Arts in Spanish from Indiana University.

She resides on the southern Mendocino coast and also works as a PA in Urgent Care at Redwood Coast Medical Services.

Ms. Duran is married and has two dogs and two cats and loves hiking, jogging, biking, kayaking and spending time at the beach.

Tod Imperato FNP

Mr. Imperato pursued his undergraduate degree at UCLA before teaching health as a Peace Corps Volunteer in Guatemala and building cisterns in a potable water project in Bolivia. He later applied his experience abroad to a master's degree in International Affairs at Ohio University. Upon graduation he spent two years teaching at the Universidad Austral de Chile on a Fulbright grant, then returned to the US to train as a Family Nurse Practitioner at Yale University.

David McIntosh, FNP
Jason Ullyot, PA