• DFI Europe
  • DFI India
  • DFI Trust

Tunneling and Underground

The purpose of this committee is to identify and facilitate the advancement of new methods and technologies for design, construction, inspection, maintenance and operation of tunnels and underground systems.



Bob Stier
Drill Tech Drilling & Shoring, Inc.
[email protected]

In 2018 Bob Stier joined Drill Tech Drilling & Shoring (DTDS) and brought with him with over 35 years of tunneling and underground experience to oversee Drill Tech’s Eastern Region. DTDS is a leader in specialty geotechnical construction industry and performs tunneling operations throughout the United States.  In the three years he has been a part of DTDS, he helped procure tunnel projects on both the West and East coasts of the U.S. and has procured and managed Drill Tech’s first foundation projects in the eastern region.  Under his guidance Drill Tech procured its largest GC Design-Build Contract for National Parks Service and he is currently managing the project.

Prior to joining DTDS Stier worked as area manager for various tunnel construction companies.  He has overseen various tunneling operations including conventional drill-and-blast tunnels, pressurized face operations, and hard rock tunnel boring machine (TBM) and micro tunnel projects. He has both direct field supervision and project management experience on major underground projects across the nation.

Stier graduated from Southern Polytechnic State University (Kennesaw State) in Marietta, Georgia with a bachelor’s of science in civil engineering technology.



Renee Fippin, P.E., G.E.
Delve Underground
[email protected]

Renée L. Fippin, P.E., G.E., is a principal engineer at Delve Underground in the Walnut Creek, California, office. She is a registered Geotechnical Engineer in California, and a registered Professional Engineer in California, Massachusetts, North Dakota and New York. Fippin’s expertise spans both geotechnical and structural engineering, including a thorough background in the design of shafts and tunnels, and with investigation and evaluation of new tunnels as well as existing tunnels for rehabilitation. Her combined detailed design and management experience, along with geotechnical and structural background, have given her unique insights to understand how to efficiently plan a project from initial to final design phases.

She is on the board of directors for Delve Underground and has published numerous papers for the Underground Construction Association of the Society of Mining, Metallurgy & Exploration. Her most recent paper is “Flood Resilience in San Francisco.”

Fippin holds a bachelor’s degree in engineering physics from Miami University.


DFI Shotcrete Short Course

2.75-day course covering shotcrete engineering, mix designs, materials, equipment, ACI Codes and specifications, construction, inspection, QA/QC, and field demonstrations used for civil and geotechnical, underground construction, shaft/tunnel, and mining projectsents and seek acceptance for use in highway projects.

GBR initiative – teaming with DFI Subsurface Characterization Committee

Geotechnical baseline reports are fundamental to all projects, but maybe all don’t see the benefits.  If you don’t know what type of soil you are building on, the potential for issues both during and after construction increases. The goal of this initiative is to raise the awareness and encourage the adoption of required geotechnical baseline reports to help promote timely, safer and more fiscally responsible projects by providing a clearer understanding of the soil conditions.

Tunnel Segment Book

Committee members writing book on tunnel segment design and state of practice

USACE Tunneling Specifications Review

Providing review and commentary on the U.S. Army Corps of Engineers’ newly draft tunnel excavation specification

Support of Excavation State-of-Practice

White paper summary of the state-of-practice of excavation support methods and practices for tunnel construction


History of Tunneling in the United States

GeoConstructability – An Owner’s Guide to Obtaining Essential Geotechnical Information for Construction (documents the type of geotechnical information  that contractors need to estimate, plan and execute foundation projects)