Our Team
R. Kevin Tillis
President / Senior Principal Engineer
M.S. Civil Engineering, University of California, Berkeley, 1986
B.S. Civil Engineering, University of Illinois, Urbana, 1983
Civil Engineer 41180 California
Geotechnical Engineer 2160 California
1993 - Present Hultgren – Tillis Engineers
1986 - 1993 Harding Lawson Associates
1983 - 1985 Lowney & Associates
Mr. Tillis is responsible for day to day operations, while concurrently managing and overseeing numerous geotechnical engineering projects each year. His experience includes management of complex levee, dam and earthwork projects for local and state agencies. His recent experience includes planning, design and implementation of construction for over 100 miles of levees in the Sacramento-San Joaquin Delta. He has an excellent track record for pushing projects through the design phase into and through the completion of construction. Construction contracts for his levee improvement projects exceed $25 million over the past five years.
Christian P. Muller
Vice President / Principal Engineer
M.S. Civil Engineering, University of California, Berkeley, 1979
B.S. Civil Engineering, University of California, Berkeley, 1978
Civil Engineer 33363 California
Geotechnical Engineer 2036 California
2004 - Present Hultgren – Tillis Engineers
1979 - 2004 Harding Lawson Associates/
MACTEC Engineering and Consulting
Mr. Muller oversees a majority of the firm's heavy industrial projects. He also specializes in deep excavation projects and marine structures. As the firm's resident safety officer, he is well versed in the safety practices and requirements of organizations such as OSHA and DISA Global Solutions. His recent industrial projects include 70 feet tall, 190 foot diameter crude oil storage tanks, both deep and shallow foundations for the associated pipe racks, seismic evaluation of a marine oil terminal with both vertical and battered piles, and a new mixed-use cargo wharf.
Callan J. Yu
Associate Engineer
M.S. Civil Engineering, University of California, Los Angeles, 2010
B.S. Civil Engineering, University of California, Davis, 2007
Civil Engineer 77899 California
Geotechnical Engineer 3117 California
2007 - Present Hultgren – Tillis Engineers
2006 - 2007 Sacramento Regional County Sanitation District
Mr. Yu provides 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. He has designed several new Bayfront levees for restoration projects including Sears Point and Bel Marin Keys. He 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.
Joseph C. Heavin
Associate Engineer
M.S. Civil and Environmental Engineering, Cal Poly State University,
San Luis Obispo, 2010
B.S. Civil Engineering, Cal Poly State University, San Luis Obispo, 2010
Civil Engineer 79187 California
Geotechnical Engineer 3083 California
2010 - Present Hultgren – Tillis Engineers
2008 - 2008 Cornerstone Earth Group
Mr. Heavin manages geotechnical engineering projects for rural and urban channels, flood control levees, marsh restoration, landslide remediation, industrial process equipment, and commercial real estate. Mr. Heavin works with numerous clients to evaluate the constructability of their projects with a focus on geotechnical constraints. He assesses erosion damage within restoration projects and designs remediation. He provides observation and testing for earthwork, shallow foundations, spread footings, drilled pier and driven pile foundations and compacted aggregate piers.
Gregory R. Olsen
Senior Engineer
M.S. Civil and Environmental Engineering, Cal Poly State University,
San Luis Obispo, 2011
B.S. Civil Engineering, Cal Poly State University, San Luis Obispo, 2011
Civil Engineer 82690 California
Geotechnical Engineer 3146 California
2012 - Present Hultgren – Tillis Engineers
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Mr. Olsen performs geotechnical investigations for a variety of public works, flood control, environmental and industrial projects. He also performs engineering analyses for a variety of projects, including slope stability analysis for landslide remediation, design configurations for levee rehabilitation, and foundation analysis for industrial structures. He provides observation and testing for grading, shallow foundations, pile and pier foundations, and lime treatment.