The project consisted of rehabilitating one mile of storm tunnel in St. Paul, Minnesota. The tunnel was 6 feet in diameter, and contained large voids outside the liner and cracks and holes leaking groundwater into the concrete liner. This process consisted of three phases, inspection and evaluation, design and construction .
CNA Engineers inspected and evaluated the tunnels using a unique rating system modeled after the NAASCO system to determine the level of repair for each area. Our engineers used liner investigative drilling to determine liner thickness and void size outside the liner. Tunnel liner repairs along with void filling were then designed with appropriate construction methods for completing the repairs in an active tunnel. The leaking cracks were sealed with urethane grout.









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The project consisted of rehabilitating 4.3 miles of storm tunnels in St. Paul, Minnesota. The tunnels varied in size from seven to 12 feet in diameter and were severely damaged with large cracks and holes in the concrete liners. Our firm was hired to inspect and evaluate, design as well as construction observation and engineering.
CNA Engineers inspected and evaluated the tunnels using a unique rating system modeled after the NAASCO system to determine the level of repair for each area. Also used was ground penetrating radar and liner investigative drilling to determine liner thickness and void size outside the liner. We performed load testing of the concrete liner in conjunction with tunnel hydraulic analysis to determine future tunnel pressures on the tunnel liner. Tunnel liner repairs along with void filling were then designed with appropriate construction methods for completing the repairs in an active tunnel. The tunnel was repaired in 3 phases from 2007-2009.






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The St. Anthony Park Tunnel System consists of 5.3 miles of active storm tunnels in St. Paul, Minnesota, varying in size from 6-13 feet in diameter. The tunnels were severely damaged with large cracks and holes in the concrete liners. Our firm was hired to handle this multi-year project of inspection and evaluation, design and construction. The work involved design of tunnel liner repairs and replacements along with void filling, with appropriate construction methods. The tunnel is being repaired in six phases between 2009 - 2015.






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The existing 6,500-ft long, 8-ft diameter 10th Ave Storm Sewer was in poor condition due to failed tunnel concrete and voids developing outside the liner. Our firm conducted extensive inspections, rating the conditions, testing and analyzing. The design repairs included liner replacement, grouting, a new outlet structure, and enlargement of an existing access shaft. Our engineers were also hired during the construction phase for observation, engineering and administration







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CNA provided site investigation, structural design, geotechnical analysis, inspection and repairs for over 3 miles of existing and new utility tunnels, utility system engineering for tunnels, open cut, bridges, construction documents, shop drawing review, construction monitoring in St. Paul, MN.














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