Edinger Channel Tunneling Design

Huntington Beach, CA

PACE prepared the preliminary planning and final design for the reconstruction of a portion of the Edinger Channel (Facility C05S05) which crossed under the Edinger Avenue I-405 freeway roadway overcrossing approaches, which include about 30-feet of earthen fill.  This channel drains a tributary watershed area of 284-acres. The existing concrete trapezoidal channel and existing 63-inch RCP at the Edinger Avenue crossing was replaced in order to double the hydraulic capacity.  An alternative feasibility study was prepared to investigate multiple alternative options to install additional underground facilities to increase the conveyance at the road crossing. There were numerous constraints that had to be addressed including a horizontal alignment of the facility which was not straight, multiple utilities, and avoiding influence to the existing bridge structure.

An innovative construction installation concept was developed that involves developing a temporary shored bridge system instead of using a conventional tunneling or jacking system.  This system was ultimately the selected alternative being more cost effective and allowing installation of a double RCB facility rather than parallel pipes which improved the hydraulics.  The temporary bridging system is placed over a vertical shored trench allowing complete access for vehicular traffic while the RCB is being constructed below the street level. PACE then prepared the construction drawings for the proposed facility and installation details of the temporary shored bridging system.