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City chooses arched culvert design for replacement of closed Chestnut Street bridge

       Drawing in part on citizen input at an October open house, city engineers have chosen a design for the new Chestnut Street bridge - an arched concrete culvert.
       “It was not the least expensive, but it is the preferred structure type based upon input at the open house,” said city bridge specialist Aaron Egbert. “Attendees were concerned about the amount of light and openness of the trail.”
       The street, which goes over South Douglas Creek, had to be closed between Vondelpark Drive and Ellston Street in August when compacted dirt under the bridge began to give way, creating a sinkhole in the pavement. Engineers have
A conceptual drawing shows how the arched culvert would look, in a view to the east. The word "channel" refers to where Douglas Creek would flow through the culvert next to the Sinton Trail.
Courtesy of City Engineering
since determined that the cause was a failure in the corrugated pipe, about 30 feet below the roadway, which had carried the creek water.
       A schedule worked out since then anticipates hiring a contractor in March, with the bridge reopening by October 2016. Preliminary work has dug down to remove the pipe, stabilize the ground and temporarily route the creek in the open.
       The new design will be similar in the sense that the bridge will again be built on compacted dirt. The difference will be that instead of a storm pipe there will be a 36-foot wide arched culvert, wide enough for the creek as well as the Sinton Trail. (See the concept drawing on this page.)
       Currently the trail, which parallels the creek west of there, diverges at Chestnut, crossing the street at a crosswalk.
       Other design options displayed at the open house (held at the Springs Journey Church in Holland Park) were a box culvert and a suspension-type bridge. The former would have been the cheapest, the latter the most expensive, city officials have said.
       At 36 feet wide, the chosen design is broader than what was shown in the arch-type renderings (drawn by a city consultant) at the open house. This was in response to citizens' general desires not to have the trail feel dark and tight inside the culvert, Egbert said.
       Another benefit of the wider arch is that the trail there can be raised somewhat higher than the creek, lessening its chances of being washed out in times of high water, Egbert explained.
       Exact cost estimates are not expected until December at the earliest. The city has $1.8 million available from the Pikes Peak Rural Transportation Authority - the bridge was on a list of projects approved by voters in 2012. If the sinkhole hadn't developed unexpectedly, plans had called for the work to be done in 2019.

Westside Pioneer article
(Posted 11/12/15; Transportation: Major Roads)

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