The phrase "since the completion of" is correct and can be used in written English.
It is typically used to refer to actions or events that have taken place after a specific event or task has been finished or completed. Example: Since the completion of their new office building, the company has seen a significant increase in productivity among its employees. In this sentence, "since the completion of their new office building" indicates that the increase in productivity has occurred after the building was finished.
Since the completion of the New England Aquarium in Boston three decades ago, much has changed.
Since the completion of the Japanese Earth Simulator, some policy makers have expressed renewed concern about United States technology leadership.
Since the completion of the Interstate Highway System, U.S. and state governments have not developed a coherent strategy for infrastructure.
The Yankees have shed five regulars from their starting lineup since the completion of the World Series -- Paul O'Neill, Tino Martinez, Scott Brosius, Chuck Knoblauch and David Justice.
Ever since the completion of Wright's first residential commissions, his clients and their successors have worked to achieve this seamless melding of horticulture and architecture.
It has been struggling with its finances since the completion of a £22m refurbishment of its central London headquarters in 2008.
Although many studies have searched for the underpinnings of personality since the completion of the Human Genome Project, in 2003, many of the relevant genes remain in question.
Since the completion of the CZCS work there has been a 10 years gap in monitoring chlorophyll spatial distribution dynamics in the ocean.
Since the completion of the H.O.V. lane, my journey (often made with passengers) has been quicker, easier and almost, dare I say, a pleasure to undertake.
Since the completion of conservation, our Silver Swan is looking wonderful, operating smoothly, and continuing to delight visitors of all ages with its performance.
Unless off-site space is leased, the refurbishment would be the first substantial new construction on the site since the completion of the Hammarskjold Library in 1961.
