The purpose of this study was to investigate the knowledge, skills, abilities and traits environmental engineers need. Two questions were asked: what skills are considered important, and where are they learned? Dreyfus and Dreyfus' novice-to-expert model, which describes a progressive, five-step process of skill development that occurs over time on the job and through practical application, was used to frame this study. This study extended prior research by including data on professional skills and seeking the input of working professionals: in this case, the technical staff at the California Department of Toxic Substances Control. Quantitative methodology and descriptive statistics were used for data collection and analysis. Results showed that experienced professionals agree that professional or soft skills are essential are essential in the workplace Many technical skills are learned over time, through practice and meaningful application on the job that builds on principles learned through formal training. Professional skills are developed through a combination of formal training and experiential learning from work, or through life experiences. The implications for higher education are twofold. Environmental engineering programs would benefit by integrating professional skills development with existing curricula, and by giving students opportunities to develop experiential knowledge in the workplace. Results indicated that environmental engineering professionals with higher levels of education and more experience believed that science and mathematics were most appropriately learned in school, while engineering, skills in technology and other technical areas were best developed through a combination of formal education with experiential learning. The more experienced people also believed that life experiences, rather than work or school, were the best way to develop professional skills. These findings confirm the Dreyfus & Dreyfus model, which indicates that individuals move from novice to expert based on experience. Environmental engineers would benefit through continuing education and in-service training. Collaborative initiatives between higher education and practitioners in environmental engineering may prove mutually effective and beneficial to students, workers, educational institutions and employers. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com/en-US/products/dissertations/individuals.shtml.]