Drainage concerns delay ped bridge transfer to city
January 17, 2018
Concerns that the elevator tower serving the new Grand Avenue pedestrian bridge at Seventh Street could be inundated with water during a major flood event has led to some extra storm drainage engineering to make sure that doesn't happen.
However, the additional work has also caused a delay in the planned transfer of the $12 million pedestrian bridge from the state to the city of Glenwood Springs. It's also resulted in some extra costs that the city and Colorado Department of Transportation hadn't anticipated.
That changing of hands is a key condition of the larger $126.5 million Grand Avenue Bridge deal.
Currently, both the pedestrian bridge and the vehicle bridge are owned by an arm of CDOT known as Colorado Bridge Enterprise, which funded the project. Replacement of the old 1954 vehicle bridge, along with the former pedestrian bridge that was constructed in the 1980s, has been the largest Western Slope infrastructure project in 25 years.
The new pedestrian bridge became necessary as part of the larger project so that numerous electrical, gas, communications and other utilities that used to run beneath the old traffic bridge could be moved to the pedestrian bridge and remain on the same basic alignment.
Part of the deal with the city was to transfer the pedestrian bridge and the accompanying elevators, which were chosen by city officials to provide access from Seventh Street, over to the city once the project was completed.
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A bill of sale between the state and the city is in the works, said Roland Wagner, CDOT's resident engineer in Glenwood Springs.
During the process of going through the punch-list items to complete that transfer, though, the city and CDOT discovered some inadequacies in the storm-water drainage system that funnels into the Colorado River from the east side of downtown Glenwood.
"It was brought to our attention that we had undersized that basin," Wagner said, explaining a "design error" on the part of CDOT involving some of the new drainage infrastructure beneath Seventh Street.
Not only that, city officials admitted that the existing storm-water drainage system serving the broader area east of Grand Avenue in that part of town is not designed to handle a so-called hundred-year flood event.
"That's a pretty extreme event, but it's the most extreme event that we try to design to," Wagner said.
The upshot of it all is that such an event would totally overwhelm the storm drainage system in the lower part of downtown and result in flooding along Seventh Street and, worse yet, in the new elevator building, he said.
"That's the primary concern for the city," Wagner said, especially since the city will be in charge of maintaining the elevator once it becomes city property.
So, "we got together with the city and came to an agreement that we both have some diligence here and decided to make it right," he said.
That meant increasing the size of the culverts and inlets near Seventh Street, and spreading the flow out between the two outfalls that run beneath the Union Pacific Railroad tracks to the Colorado River.
The UP has also been involved in the negotiations, since some of the infrastructure will have to run beneath the railroad platform in order to avoid disrupting utilities under Seventh Street, Wagner said. Some drainage improvements on the railroad property are also in the works, he said.
The extra drainage work will end up costing CDOT about $250,000 to $300,000 more than planned, but that still falls within the project budget, Wagner added.
For its share, the city will take the cost for the extra work that it had to do out of a $400,000 grant from the Colorado Department of Local Affairs that was meant for Seventh Street improvements anyway, City Manager Debra Figueroa said.
Total cost for the city's portion is still being determined, she said.
In addition to dealing with the drainage issues, the city has also been through required training to learn how to operate and maintain the elevators.
Figueroa said that responsibility will fall to the city's Parks and Recreation Department.
"We will have a maintenance contract on the elevators like we do for all elevators in our buildings," she said.