 NEW YORK--BUSINESS WIRE--Halper Sadeh LLP, a global investor rights law firm, is investigating whether the merger of Columbia Banking System, Inc. NASDAQ: COLB and Umpqua Holdings Corporation is fair to Columbia shareholders. Under the terms of the agreement, Umpqua shareholders will receive 0.5958 of a share of Columbia stock for each Umpqua share they own. Upon completion of the transaction, Columbia shareholders will own approximately 38 of the combined company. Halper Sadeh encourages 