Construction began in 1989 without a signed agreement from Continental and United. By March 1991, the bidding process was in full swing for the main terminal, concourses and tunnel. Preliminary risk analysis involved three areas: Cost: The grading of the terminal area was completed at about $5 million under budget and the grading of the first runway was completed at about $1.8 million under budget. This led management to believe that the original construction cost estimates were accurate. Also, many of the construction bids being received were below the city's own estimates. Human resources: The economic recession hit Denver a lot harder than the rest of the nation. DIA was at that time employing about 500 construction workers. By late 1992, it was anticipated that 6000 construction workers would be needed. Although more than 3000 applications were on file, there remained the question of available, qualified labor. If the recession were to be prolonged, then the lack of qualified suppliers could be an issue as well. Weather: Bad weather, particularly in the winter, was considered the greatest risk to the schedule. Fortunately, the winters of 1989-1990 and 1990-1991 were relatively mild, which gave promise to future mild