Callan has 16 years of experience as a geotechnical engineer. He has provided geotechnical engineering consultation for flood control levees, dams, repair of landslides, marsh restoration projects, seismic hazard evaluations, hydraulic structures, marine and waterfront structures, and commercial development. Callan has designed several new Bayfront levees for restoration projects including Sears Point and Bel Marin Keys. Callan is a technical leader and is proficient with the use of analytical methods and modeling related to slope stability, retaining structures, deep foundations, settlement, seepage, and seismic hazards.