Occupied Underground Space


  • Elmer L. Anderson Library
  • Mine Conversions to Underground Space
  • River Centre Connection
  • Underground Science City
  • University of Minnesota Civil Engineering Building

Elmer L. Andersen Library

CNA Engineers designed the underground storage space for the Elmer L. Andersen Library at the University of Minnesota. The library has two components – a storage of archives collections as well as overflow storage.
This University of Minnesota project consisted of two storage caverns, a four-story conventional surface building, two vertical shafts and a mined portal entrance. The mined caverns and tunnels have a footprint of 106,000 square feet and an excavated volume of 95,000 cubic yards. Each cavern is 600 feet long, 25 feet high and 70 feet wide. The shafts provide vertical circulation between the surface and mined space, as well as emergency egress. The 50 foot high mined portal provides a drive-in entrance for vehicles as large as a semi-trailer. Our firm provided the following services for the library’s mined space, shafts and portal structure: feasibility study, preliminary and final design, construction engineering and administration.

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Mine Conversions to Underground Space


CNA Engineers have provided survey, evaluation and rehabilitation for more than 30 million square feet of underground mines for conversion to warehouse space.
Tasks have included calculating rock conditions, rock support, concrete linings, steel structures, water control and drainage, recommendations for rock trimming, and concrete placement for the relocation of an underground railroad line.
Our firm has worked on facilities in: Louisville, Kentucky, Independence, Missouri, Kansas City, Missouri, Wampum, Pennsylvania and Cumberland Furnace, Tennessee


RiverCentre Connection

CNA Engineers provided geotechnical engineering and design services for the River Centre Connection project in St. Paul, Minnesota. The all-weather connection was critical to the long-term growth of St. Paul’s convention industry.
The project consisted of designing an underground tunnel and a skyway from the River Centre’s east entrance down Fourth Street to the southeast side of the Landmark Towers building where it enters into the existing downtown skyway system. The design was complicated by combined building aspects, a fixed budget and the downtown location. Our technical leadership was needed to deal with the wide range of geotechnical engineering, architectural, risk-assessment and utility conflict issues.




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Underground Science City

Our firm conducted a feasibility assessment of a very large underground office park in Singapore. The assessment included: site analysis, site geology appraisal, space programming, preliminary planning and design for three underground space layouts, detailed layout developed for the preferred layout and construction cost estimate.
The preferred layout was a regular, room-and-pillar underground complex consisting of 36 caverns each 20 meters wide by 22 meters high by 75 meters long. All caverns branch off a main concourse that connects underground entry points. The gross underground floor area was approximately 290,000 square meters. The design featured a flexible layout and provided daylight and connection to the surface deep underground through a massive open atrium.

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University of Minnesota Civil Engineering Building


CNA Engineers was part of the team that received the “Outstanding Civil Engineering Achievement” award in 1983 from the American Society of Civil Engineers for work on the University of Minnesota Civil Engineering Building. The project was funded by the National Science Foundation.
The building was comprised of four upper floors of cut-and-cover construction and two lower floors of mined underground space 100 feet below the surface. A flat-lying, 30 foot thick limestone layer separated the two parts of the structure. The mined underground space was excavated in a soft sandstone layer below the limestone roof.

The decision by the U of M to design and build this underground structure relied on extensive experience and research in the area. The space was finished into two floors of offices, a laboratory and common space.
Charles Nelson was co-principal investigator on this National Science Foundation funded project. The test room, which is now beneath parking ramps, demonstrated the features of such construction and led to the development of design and construction techniques applicable to full-scale projects.
CNA Engineers planned and directed site investigation, as well as designed and monitored construction of the mined space of the Civil Engineering Building.


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