History

The City and County of Denver designed this project to bring the flood zone from the Broadway Street corridor over to the Platte River.  This project included over 1400 LF of 6’x4′ RCBC, requiring 74″ tunnel under the UPRR, BNSF & RTD light rail tracks, and a tunnel (MTBM) under Sante Fe Road.  It included installation of multiple Type-B and Type-P manholes and an outfall structure at the Platte River.    

Challenges

Railroad permitting proved to be time consuming and difficult requiring construction methods of the tunnel to be approved by all agencies involved.  Upon commencing construction, two unidentified foundation walls were encountered: a cement foundation and a sandstone foundation wall.  Crews also encountered soil with petroleum based contamination which required remediation.  Original design called for vertical soil compaction piers above the alignment but, with railroad restrictions denying access to the track surface, an alternate method was proposed- Microtunnel (MTBM).  

Solutions

Obstacles Overcome! And while the closed face slurry system of the MTBM was ideal for use under the six (6) sets of tracks, BTrenchless elected to employ a 24/7 hand tunnel operation.  Soil contamination was remedied using a biological degradation product at the tunnel face.  Ultimately, the redesign resulted in substantial Cost Savings to the owner.

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BT Construction