Field Note: Sorrento to Miramar Double Track, Phase One

The Sorrento to Miramar Double Track project in San Diego, Calif., is the first of two phases of construction to speed passenger and freight rail services on the Los Angeles-San Diego-San Luis Obispo rail corridor.

The project involves straightening part of the slowest, steepest, and highest-curve territory of any segment along the corridor. A wooden trestle bridge built in the early 1940s will also be replaced, and a new track crossover will be installed.

Flatiron proposed using innovative permanent soldier pile tieback walls on a portion of the project to owner SANDAG as a Value Engineering alternative to the conventional reinforced concrete walls, saving both time and money. The alternative wall design consisted of drilled-in soldier piles with temporary treated timber lagging between, and a permanent rock sculpted shotcrete architectural facing. Lateral support for the wall was provided by permanent tiebacks at taller wall heights. This wall system is traditionally constructed as a “cut” wall but was constructed successfully and economically as a “fill” wall in this instance.

Project completion is expected in April 2014.