The Trench: a testament to modern construction.

From the air, it's easy to see the scope of the Mid-Corridor Trench. It's 10 miles long, 33 feet deep and 50 feet wide, stretching toward the horizon and literally reshaping the landscape of southern Los Angeles County.

But a glimpse inside the construction process confirms its true value as a monument to modern engineering.

"The Mid-Corridor Trench is the signature project of the Alameda Corridor," said Tim Buresh, Director of Construction and Engineering for the Alameda Corridor Transportation Authority (ACTA). "From an engineer's perspective, the Mid-Corridor Trench is probably the most challenging and rewarding project most of us will work on n our careers."

* More than 750 underground and overhead utilities were relocated or reconstructed.

* A bypass track was built to ensure continuous rail service during construction.

* More than 4 million cubic yards of dirt were excavated.

* An estimated 450,000 tons of contaminated soils from previous operations were removed and properly disposed.

* 27,000 holes were dug and rebar cages built for the pilings that support the trench walls.

* 2,200 pre-cast concrete struts were installed across the top of the trench.

* 30 bridges were built to carry street traffic over the trench.

* 20 miles of railroad track (two sets in each direction) were installed.

The trench had to be completed under strict deadline for the Alameda Corridor grand opening in April 2002--a little more than three years after the notice to proceed was issued.

How was that accomplished?

A leading factor was that the Mid-Corridor Trench was constructed under the design-build method of project delivery, Buresh said, giving ACTA greater control over costs and schedules. This method enabled ACTA to award the Mid-Corridor contract based on lowest ultimate cost, with a contract that ensures the work will be completed by a fixed date and at a fixed cost, subject to significant financial penalties.

Moreover, a design-build contract differs from a traditional public works contract in that the contractor is responsible not only for building the project but also designing it (based on parameters provided by the contracting agency). That carries the advantage of allowing various tasks to proceed concurrently.

ACTA officials estimate that utilizing the design-build approach saved 14-18 months in project delivery.

Another factor in successfully keeping Mid-Corridor Trench work on schedule and on budget, Buresh said, was close coordination among ACTA staff, their consulting engineers at the Alameda Corridor Engineering Team (ACET, and the prime contractor, the Tutor-Saliba Team.

"It sounds like a cliche, but from the beginning we really placed a premium on teamwork and cooperation among ACTA, ACET and the contractors," Buresh said. "We knew our performance would be closely monitored by government officials at the federal, state and local levels, and we all committed ourselves to delivering work that would make us proud."

Another factor that drove the speedy construction schedule was that Trench excavation and construction proceeded from two locations simultaneously, rather than from only one location.

"It was almost like managing two separate and nearly identical construction projects at the same time," Buresh said.