A restructuring and management shakeup is afoot at the largest wealth management firm in the Tri-Counties.

Michael Mayfield, CEO and co-chief investment officer of Santa Barbara Asset Management, is retiring from the firm effective March 1, after 18 years there. During that time, he helped SBAM more than double its assets under management, to $5.3 billion currently, making it by far the largest wealth management firm in the tri-county region.

James Boothe, a portfolio manager with the Santa Barbara office, has been named chief investment officer.

Nuveen Investments, the Chicago-based firm that purchased SBAM for $50 million in cash in 2005, confirmed the leadership changes.

A Nuveen spokesperson also told the Business Times that as part of of the transition, some of SBAM’s business will move over to another affiliate, Nuveen Asset Management, which was taken over last year by Bob Doll, a big-name portfolio manager. Doll made headlines late last year when he left Wall Street giant BlackRock to join Nuveen.

Santa Barbara Asset Management’s 8,474-square-foot headquarters on the fifth floor of the El Paseo building at 820 State St. may be put back on the leasing market, several sources in the South Coast commercial real estate industry told the Business Times. The wealth management firm moved into the prominent downtown location in early 2011, from a smaller space on Carrillo Street.

The Nuveen spokesperson declined to comment about SBAM’s possible relocation. She also declined to provide information on the number of staff affected by the changes.

Mayfield was named the Executive of the Year by the South Coast Business & Technology Awards in 2011.