LONDON (Reuters) - OMERS Private Equity and the Alberta Investment Management Corporation (AIMCo) have sold a controlling stake in consultancy Environmental Resources Management (ERM) to private equity firm KKR, the Canadian funds said on Monday. The 60% stake sale gives ERM an enterprise value of $2.85 billion, a source familiar with the matter said. UK-headquartered ERM operates in 40 countries and has more than 5,500 staff, advising clients on sustainability challenges and commercial opportunities. OMERS had a little over 40% of the business while AIMCo had slightly under 20%, with ERM management holding the balance, the source added. OMERS Private Equity, a unit of the Ontario Municipal Employees Retirement System, and AIMCo started investing in ERM in 2015 in a deal that valued the company at $1.7 billion. KKR is due to close its stake purchase in the third quarter. Reporting by Carolyn Cohn; Editing by Pravin Char Our Standards: The Thomson Reuters Trust Principles.