The Regional Connector Transit Corridor (RCTC) comprises a 1.9-mile underground light-rail project woven through downtown Los Angeles (LA). This $1-billion design-build project's reference design indicated the need for a large and intrusive open excavation, approximately 100-feet long and 30-feet wide, to remove existing tiebacks within the public right-of-way and in conflict with the RCTC bored tunnels. To minimize surface impacts, the design-build team, Regional Connector Constructor (RCC), proposed an alternative tieback removal concept comprising a vertical shaft and mined adit. This paper describes the use of Building Information Modeling as a powerful design tool to optimize the location, size and alignment of the concept and demonstrates its feasibility to the Project Owner, LA Metro, and describes the shaft and adit construction in a dense urban setting and the tieback removal process.
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