Depends on what aspect you look at it from.
There was an effort by the Wayne County back in the late 80's early 90's to build a new terminal. They even had a design competition that Bechtel had won. The initial design came in at around $1 Bil +. NW
was not in a good financial position at that time so the project was put on hold.
In '96 NW
and the County came to an agreement that NW
would manage the project; design, construction, and finances.
In late '96 the NW
Project Team was organized and design work was started with SmithGroup, aka SHG being the terminal designer. In about summer of '98 civil work was started. Actual terminal work did not start until Feb '99. Work was completed in early 2002 and went online 24FEB02.
The original scheduled opening date was for December '01 but do to several factors, including Sep 11th it was pushed back to Feb '02.
So to answer your question, the actual terminal construction took about 34 months.