Kiewit has cleared the site and relocated utility lines in preparation for the construction, according to Denver's Regional Transportation District.
The redevelopment of Union Station is central to RTD's FasTracks project. The station will serve as a hub for passenger rail lines throughout the city.
But the rail association is fighting RTD's plan, arguing that it puts light-rail and commuter-rail passenger platforms too far apart. The platforms are separated by several blocks, with the underground bus station in between for rail passengers to use to reach the other platforms.
The association filed its request for a restraining order stopping construction on March 1. The association argued that allowing construction to proceed while its larger court fight continues against RTD's plan for Union Station, a plan approved by the Federal Transit Administration, would render the case moot.
But RTD has argued that delaying construction could threaten the financing of the station's redevelopment by putting federal funding at risk. The station project recently received $304 million in loans from the U.S. Department of Transportation to help pay for construction.
In his decision, Kane said that it is "speculative and entirely tenuous" to argue that the rail association would succeed in its larger fight against the Union Station plan -- a key factor when deciding whether or not to stop construction at the station.
"The planning and NEPA [National Environmental Protection Study] procedures underpinning the project at issue took place over six years, publicly, and with input from public and private entities," Kane said in his ruling.
"Plaintiff's legal arguments boil down to little more than repeated conclusory assertions that the NEPA process has 'flaws.' Nothing more. On the record before me, I cannot conclude plaintiff has made a sufficient showing of likelihood of success on the merits of its appeal," he said.