DES MOINES – Plans were unveiled Friday indicating computer giant Microsoft has selected West Des Moines as the site for a $1.1 billion regional data center to be built in four phases.Details of Project Alluvion were made public during the state Economic Development Authority’s monthly board meeting indicating the company based in Redmond, Calif., plans to create up to 84 jobs on a 154-acre site at a projected cost of $1.126 billion.