If Southwest light rail is ever completed, its first riders may board the train carrying Christmas presents rather than Halloween pumpkins.

Project organizers announced Wednesday night that the timeline had been bumped back about three months after federal transit officials agreed with a Minneapolis Park Board request for earlier environmental analysis. If all goes smoothly for the project — which so far it has not — the line would open at the tail end of 2019.

The new request means the Metropolitan Council will now conduct an expedited assessment of how the project affects parks and whether there are "prudent" alternatives to minimize detrimental effects. The Park Board thinks routing light rail through a tunnel rather than a planned bridge between Cedar Lake and Lake of the Isles would help satisfy that goal.

But that tunnel would come at tremendous cost and delay, Met Council officials told the Park Board on Wednesday. The change would push the project into late 2020 or early 2021 and add costs ranging from $105 million to $145 million, depending on the type of tunnel. Some of those added costs were attributed to inflation, since the project would also miss the 2016 construction season.

"We are short today on time and short on regional resources," council chairman Adam Duininck told the Park Board.

The Federal Transit Administration asked the Met Council to move up the review after the Park Board sent it a letter saying the project is violating federal law. The letter said the project had advanced too far without more substantive analysis of how to minimize park impacts — though council staff noted to the board Wednesday that about 850 hours were spent studying a shallow tunnel through the channel.

"The SWLRT Project has failed to engage in any meaningful evaluation of feasible and prudent avoidance alternatives, or make plans to ensure that the least overall harm alternative is adopted with respect to federally protected parkland," board President Liz Wielinski wrote in a letter to the agency in January.

In particular, the board is concerned about the noise and vibrations that would be caused by light-rail trains crossing a bridge that now carries only recreational and freight rail traffic. A replacement bridge would be substantially wider to accommodate the new traffic, which a consultant hired by the board said in a presentation Wednesday would "reduce natural light in the channel" and have a "visual impact."

The Park Board is facing increased pressure to reach a deal after Gov. Mark Dayton threatened to slash state funding for Minneapolis' regional parks over their actions pertaining to Southwest light rail. At Wednesday's meeting, Commissioner Anita Tabb said other entities also added delay to the project.

"I would say, in my opinion, that it's not just the Park Board that has held this up," Tabb said. "We're probably the last little bit of this. But to hold us responsible for the project impacts increasing so significantly, I think is just really tremendously unfair."

There are also positive signs for the project emerging from the federal government. Federal officials increased the project's rating from medium to medium-high and the White House recommended funding Southwest in its 2016 budget — making it one of only seven projects in its class added this year.

Eric Roper • 612-673-1732

Twitter: @StribRoper