Gregg began his career with TxDOT as a summer hire in the Austin District in 1986. After graduating from Texas A&M University with a Bachelor of Science degree in Civil Engineering, he joined the TxDOT Bridge Division in January of 1987 as an Engineering Assistant in the Bridge Design Section. He became a Registered Professional Engineer in 1991. In March of 2001 he became a Bridge Design Group Leader. Gregg assumed the duties of Design Section Director in December 2010. In October 2011, Gregg was appointed Director of the Bridge Division. Gregg Subsequently retired from TxDOT in 2018 after a 32 year career with the agency. Gregg is currently serving as the Executive Director of the American Segmental Bridge Institute. He is the elected President of Infrastructure Advancement Institute and the outgoing Chairman of the AASHTO T-10 Concrete Committee.