Design to be ready by spring for new Fillmore interchange
Changing strategies for the Fillmore interchange, the Colorado Department of Transportation (CDOT) has begun a design process for a new structure there.
Detailed plans are nearing 25 percent completion. CDOT expects to reach 100 percent by spring, which would allow construction to begin if an estimated $11 million becomes available, according to Mark Andrew, a CDOT resident engineer for this region who is spearheading the effort.
The goal is still for a diverging diamond interchange (DDI), as announced last winter. In a DDI layout, through traffic is directed to the left instead of the right (from stoplights at either end of the bridge), which eliminates the need for left-turn signals at the on/off-ramps.
The previous state strategy had been to implant a DDI layout over the existing Fillmore/I-25 bridge deck. But after a federal grant was turned down a few months ago, CDOT hired an engineering firm (HDR) to analyze the matter more deeply.
The diverging-diamond style on interstates is relatively new, with the first having been opened just three and a half years ago in Springfield, Missouri. As HDR's design effort has moved forward, state engineers have agreed that a wider bridge at Fillmore - actually two bridges, side by side - would be needed to accommodate a DDI configuration, Andrew said.
“A diverging diamond on the existing deck would have worked, but barely,” he said. With a wider structure, there will be room, he added, for bike lanes on either side and a single 10-foot-wide sidewalk.
The sidewalk would be in the middle, between the two through lanes, “to avoid conflicts,” he said.
The DDI project will still be smaller and less expensive than what's previously been envisioned at Fillmore/I-25. CDOT had received a federal environmental assessment (EA) OK eight years ago for an interchange replacement estimated at one point to cost $84 million.
Andrew said he was “confident” about the current $11 million construction estimate.
One savings from past strategies for the interchange will be that “there won't be a lot of work associated with the ramps or approaches,” Andrew said. Both the southbound off-ramp and northbound off-ramp were lengthened as part of the COSMIX I-25 project five years ago that widened the interstate to six lanes.
The new project will upgrade the southbound off-ramp and northbound on-ramp. The southbound off-ramp especially has been a problem, with cars backing up from the light, sometimes even onto the interstate shoulder. But that ramp “will have more free flow onto Fillmore” as a result of the recently started Pikes Peak Rural Transportation Authority (RTA) project that is realigning Chestnut Street away from the Fillmore interchange, Andrew said.
The interchange work is intended to tie in with the RTA project, as well as with the existing Fillmore bridges over the railroad tracks and Monument Creek east of the interchange.
Andrew was asked about the cost similarity between a new structure and a DDI-style bridge deck. The deck plan (which also would have included improvements on the two ramps) was estimated at $10 million in the grant request. “That may have been a little high,” he said.
So, what are the chances of the construction being funded? Andrew said he believes “the money is out there.” But depending on how much funding is found, a decision may be needed from the Pikes Peak Area Council of Governments (PPACG) board. Currently, the highest PPACG priority among major, unfunded projects is a replacement Cimarron/I-25 interchange, but that project will require all new ramps, with overall construction estimated at about $95 million.
Andrew said that CDOT is trying to find funds so that the PPACG won't have to choose between the two interchange projects. “Our goal is to have funding for both,” he said.
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