Colleen Marnell Named to ENR’s 2025 National Top 20 Under 40 List

This year, we congratulate Colleen Marnell, PE, for being named to Engineering News-Record’s (ENR) 2025 National Top 20 Under 40 list! This recognition is given to the top young professionals under 40 years old who are rising leaders in the AEC industry. ENR’s National Top 20 Under 40 are selected from more than 450 entries for the regional Top Young Professionals competition. In 2025, Colleen was named among ENR Midwest’s Top Young Professionals before achieving national recognition as well.

This honor is more than deserved, evidenced by Colleen’s tremendous service to the firm and her industry as well as her dedication to inspiring the next generation of engineers. As one of the youngest regional leaders in the history of the firm as of January 2024, Colleen is a testament to exceptional leadership. Spearheading the creation and integration of solar services across 50+ Kimley-Horn offices, Colleen has been a pioneer in the solar industry, with the results of her forward thinking resulting in multi-million-dollar contracts in solar and natural gas services. She led the expansion of Kimley-Horn’s solar practice into Virginia, Maryland, North Carolina, Minnesota, and Georgia. In partnership with colleagues on the West Coast, she also helped establish teams in California and Nevada.

A native of Chicagoland, Colleen has led committees for Commercial Real Estate Women Chicago, Women of Renewable Industries and Sustainable Energy, Women’s Energy Network, International Council of Shopping Centers Next Generation. In addition to her industry involvement, Colleen has a deep personal commitment to inspiring the next generation of engineers. She has actively mentored young professionals—from interns to emerging leaders—through Kimley-Horn’s robust training programs, which cover everything from consulting to technical skills, professional development, marketing, leadership, business practices, and company culture.