An aviation gasoline (Avgas) spill of near 35,000 gallons occurred over 20 years ago at the U.S. Coast Guard Air Station in Traverse City, Michigan. The site has a relatively uniform subsurface of beach sand to a depth of 50 feet. A three-feet vertical smear of oily globules was near the water table depth of 15 feet. Two pilot-scale bioventing systems were evaluated on a portion of the 240 x 1100 foot surface area plume. The vadose zone contaminated with aviation gasoline was satisfactorily bioremediated by both venting systems. Differential performance between the two systems was not apparent. Operational time for clean-up was eight months. Surface emissions of gasoline vapor during systems operation were minimal.