What is the fine-grained topic of the following text: Following his discharge from the Air Force, Keith worked in heavy construction, where he gained valuable experience prior to becoming a founding member of Mechanical Systems, Inc. As company vice president, Keith has been responsible for the development and growth of the site utility side of the business, and he continues in his role of business development and operational oversight. Only return the topic.
Keith's career progression and responsibilities in Mechanical Systems, Inc.