Security Pacific National Bank is selling its escrow department to Spring Mountain Escrow Corp. of Newport Beach, according to sources close to the bank. The sale price was not disclosed and spokeswomen for both companies declined to comment. But the sources said the transaction is expected to be completed next week. Spring Mountain is the largest independent escrow company in Southern California, with 115 employees and 20 offices. Security Pacific employs about 200 people in its escrow department, and it was unclear what arrangements have been made for their employment after the sale. The transaction fits a pattern in which Security Pacific and its parent company, Security Pacific Corp., are selling off assets to finance acquisitions in neighboring states.