Dr. Johns is an aquatic scientist who specializes in aquatic ecological risk assessments (ERAs), particularly those associated with contaminated sediment. The focus of his 30 years of professional experience has been on the effects of toxic pollutants on aquatic organisms. Dr. Johns is responsible for the management of large, multi-task, multi-disciplinary environmental investigations, including remedial investigation/feasibility studies (RI/FSs) and natural resource damage assessments (NRDAs). He has served as the program manager for investigations at several large Superfund sites, including the Lower Duwamish Waterway RI/FS and the Portland Harbor ERA. Dr. Johns has also served in an advisory capacity as a technical expert in the regulatory arena, providing technical review and comments on proposed environmental regulations. In addition, he has provided technical support to clients involved in litigation regarding mining sites, petrochemical facilities, heavy industrial sites, and ports.

As a principal investigator at the EPA National Research Laboratory in Narragansett, Rhode Island, he served as assistant technical director of the joint EPA/US Army Corps of Engineers (USACE) Field Verifications Program, one of the first comprehensive programs to assess the impacts of contaminated sediment on aquatic species, and one of the first applications of an ERA to contaminated sediments. Dr. Johns is a recognized expert on the use of bioassessment techniques to evaluate sediment contamination, and he was responsible for the development of the Neanthes bioassay used by EPA and USACE.