Iron Mountain has announced plans to enhance shareholder value by returning $2.2 billion through 2013. We are placing our 'BB-' corporate credit rating for Iron Mountain on CreditWatch with negative implications. The negative CreditWatch listing reflects the potential for a downgrade if the transaction causes leverage to go above 5.5x, our leverage target at the current rating level NEW YORK (Standard&Poor's) April 19, 2011--Standard&Poor's Ratings Services said today it placed its 'BB-' corporate credit rating for Boston-based Iron Mountain Inc., as well as all related issue-level ratings, on CreditWatch with negative implications. "The CreditWatch listing follows the company's announcement that it plans to enhance shareholder value by returning to stockholders $2.2 billion through 2013, including approximately