Medical Staff



              Haku Kahoano MD,  Medical Director

Haku Kahoano MD is the newest physician at Mathiesen Memorial Health Clinic. Internal medicine trained, Dr. Kahoano received his MD from the John A. Burns School of Medicine, Honolulu, Hi and his medical licensure while at Tripler Army Medical Center. During his 9 year career in the U.S. Army, Dr. Kahoano primarily served as an operational flight surgeon and primary care staff physician across multiple med sends and missions. He was deployed three times in service to his country. With both Native Hawaiian and American Indian Ancestry, Dr. Kahoano comes from a background with high regard for health and functionality.  A renaissance man incarnate his hobbies include Muay Thai  (martial arts), Art, Music, Science and Leadership. Dr.Kahoano was born and raised in Honolulu HI and once was a starting defensive end for the University of Hawaii where he received Honorable Mention All Western Athletic Conference Honors and lettered for 4 years.


         Gina Valente Moore, BSN,RN,MSN,ND,PNPc,FNP

Dr. Gina grew up in a small town in Northern California as the second oldest of five children.  After high school she set out college at Santa Clara University where she Obtained a degree in marketing and went to work for Macy’s selling sleepwear and lingerie.  It was not long before she realized that half the world did not even wear underwear and this was not her life’s’ work.  She left this job after less than one year and returned to her childhood home where she was greeted by one particular medically fragile infant that sparked her interest and lit a fire that still motivates her today. Dr. and Mrs. Valente have cared for hundreds of medically fragile foster children and on her return home Dr. Gina was able to fall into the daily care of tiny Brian.  It was here that she discovered meaning and where she should be applying herself.  She returned to school and gained Bachelors, Masters and Doctorate degrees in Nursing with a specialty in Pediatrics from Case Western Reserve University in Cleveland, Ohio.  She then returned to California as a National Health Service Scholar and worked as a Pediatric Nurse Practitioner and School Nurse for several years. Never being content with her level of education she returned to school at Sonoma State University and attended their Post Masters Family Nurse Practitioner Program in order to be able to care for the entire family not just the children.  On the same day that she completed that program in 2000 she gave birth to her first son Garrison.  Three years later Ryan would bless their home. She worked in Family Practice in Ukiah for 10 years before following her husband Steve to the Mother Lode where he works in the winemaking industry.  Not only have they enjoyed all the Sierra foothills have to offer in the outdoor activities but Dr. Gina was given the opportunity of a lifetime to train in Gastroenterology under a Stanford trained Gastroenterologist, Dr. Cox. He shared his knowledge as they worked together for three years at Sierra Gastroenterology Consultants in Sonora. Dr. Gina is currently practicing at Mathiesen Memorial Health Clinic, still specializing in intestinal disorders, loving especially treating hepatitis C, cirrhosis and liver disorders.

Melissa Ronneburg, FNP

Melissa Ronneburg is a family nurse practitioner. She completed her degree at Loma Linda University in Southern California. After finishing school she worked in a very busy asthma and allergy practice. Melissa and her husband moved to Sonora 2003. It did not take long to consider Sonora home. In January 2015 Melissa joined the Mathiesen Memorial Health Clinic family. She is enjoying being back practicing medicine after taking a brief leave of absence while raising her children. In her “spare time”, Melissa is active in her children’s school, soccer and 4-H. The Ronneburg family enjoys camping and fishing in the Sierras.

     David DeMattei, PA-c

David DeMattei is a Certified Physician Assistant who completed his medical training at Stanford University in Palo Alto, California. Born and raised in Tuolumne County, he worked extensively as an Emergency Medical Technician before pursuing his education at the Stanford School of Medicine. He enrolled at Stanford in hopes of one day bringing his knowledge back to his home town; he is pleased to have accomplished this by joining the team at Mathiesen Memorial Health Clinic. He and his wife live in Sonora; they enjoy hiking, camping, and snowboarding. David looks forward to serving the families of Tuolumne County and seeing patients of all ages.

Dolora Dossi, Psy.D. Registered Psychologist

Dr. Dossi’s family has deep roots in Tuolumne County where her grandfather was the track master at Railtown. Her dad graduated from Sonora High 40 years before she did. She has been a K-12 teacher here at Jamestown Elementary and SUHS. She received a doctorate degree in Clinical Psychology and has been offering care to patients for nearly 20 years. She specializes in depth psychology and has certification in the practice of hypnosis. Her professional interests include postpartum depression,
trauma, sleep disorders, and piecing together someone’s life story to help see patterns and habits (the good ones and the not-so-helpful ones!) Dr. Dossi offers individual, couple, family, child, and adolescent counseling.


Jennifer Hemminger, LCSW

Jennifer Hemminger is a Licensed Clinical Social Worker (LCSW) at Mathieson Memorial Health Clinic. Born and raised in a small Kansas town, Jennifer moved to Sonora six years ago from Los Angeles, seeking a better community connection and change of pace.  Since then, the Hemmingers have embraced the beautiful area and its people. Jennifer received her Bachelor’s degree in Psychology from the University of Colorado at Colorado Springs and her Master’s in Social Work from San Diego State University. She has broad experience providing mental health services and therapy to people of all ages and has a specific passion working with victims of trauma, violence and abuse. During her graduate education, she received inpatient psychiatric training at UCSD, as well as experience with trauma victims at San Diego Children’s Hospital. While completing her LCSW in Los Angeles, Jennifer worked at various programs including the Violence Intervention Program- an outpatient community health clinic, affiliated with LA County-USC Hospital. Her professional interests include working with trauma victims, supporting and advocating for parents, play therapy as well as community outreach within the mental health field. She has experience in providing individual, family and group therapy. While not helping people achieve their therapeutic goals, Jennifer enjoys running, cooking, and spending time with family and friends.






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