David Folkes David Folkes is a Senior Principal with Geosyntec Consultants, Inc. in Denver, Colorado. Dave has worked on over 200 vapor intrusion (VI) projects across North America and overseas since 1998, including sites in Europe, South America, Australia, and Southeast Asia. He is Project Director of the Redfield Site, one of the largest VI sites in the US, and has served as an expert witness on several major VI cases, including class action lawsuits. Dave has been extensively involved with development of VI practice and guidance in the US, including training of regulators and consultants on use of the 2002 draft EPA VI guidance; and assistance with VI guidance development and training in many states over the past decade. As a member of the Interstate Technology and Regulatory Council (ITRC) VI and PVI Teams, Dave helped develop its 2007 VI and 2014 PVI guidance and served as a training instructor for both. He is currently a member of the ITRC VI Mitigation Training Team. Dave earned his bachelor's degree in Geological Engineering in 1977 and his master's degree in Civil Engineering in 1980, both from the University of Toronto, Canada. He is a registered professional engineer in Colorado.