When Pat Callahan gets on her bike, it's hard for her to stop. She rides 35 to 40 miles each Saturday on one of her pro-level Cannondale models, when she's not entering events like the five-hour, 100-mile Marin Cyclists Club ride she pedaled through this summer. She also takes a "spin in the gym" when darkness falls, "which is often true given the way I'm working these days."

Long days are the norm now for the executive vice president in charge of integrating the former Wachovia into the now nearly $1.3 trillion-asset Wells Fargo. Callahan, who also heads Wells' human resources, communications and social responsibility units, was tapped by CEO John Stumpf to lead the transition team last December. She has taken charge of more than 20 business integration teams combining the brands, operations and the markets all under the Wells flag - a monumental task being watched closely by skeptics who wonder if Wells will come to regret outbidding Citigroup for Wachovia, whose current and future losses are estimated at around $74 billion.

The most visible signs of change are just around the corner; in November, Wachovia branches and ATMs in Colorado will be converted to the Wells Fargo brand. In all, some 3,300 branches will be re-branded, a process that Callahan says could take up to three years. Reams of changes are already well underway behind the scenes, including the completed merger of legal, finance and treasury services departments. Callahan is also spearheading a $5 billion reduction in expenses by 2011, brought about by store closings and vendor consolidations, as well as an undisclosed number of layoffs and cutbacks in benefits and compensation.

Mergers are nothing new for Callahan, a 31-year Wells veteran who has been through more than a dozen in the last eight years as the bank's human resources chief. She's also held posts in charge of compliance and enterprise risk management, wholesale banking, finance and operations.

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