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Fillmore/I-25 contractor chosen for Chestnut Street project; work to start soon

The Chestnut Street closure can be seen in early March between Vondelpark Drive (foreground) and Ellston Street (background).
Westside Pioneer photo
SEMA Construction, the company building the Fillmore/I-25 interchange, has been hired as the contractor to reopen the long-closed Chestnut Street bridge
       Work on the $2.9 million project should get started by the end of March, according to Mike Chaves of City Engineering. Completion is anticipated in October.
       “We want to get started as quickly as possible,” he said. “The neighborhood has been inconvenienced by this.”
       A frontage road just west of I-25, Chestnut has been closed between Vondelpark Drive and Ellston Street since last August when a sinkhole cracked open the pavement across both lanes of traffic. The city then began a process, including an October public meeting, that led to a final replacement design. The city advertised for contractor bids, and the Pikes Peak Rural Transportation Authority (RTA) approved City Engineering's recommendation for SEMA at its March 9 meeting.
       At the public meeting (and at a traffic-related meeting in January), Holland Park residents talked about issues resulting from losing a key street and finding an increase in detouring speeders through their neighborhood. The city has since added four stop signs (three on Vondelpark and one on Holland Park Boulevard) to help slow vehicles down.
       While agreeing that “it seems like a long time [since the sinkhole happened],” Chaves opined that the city's response to the closure, with construction now imminent, “is actually pretty good for a project of this magnitude.”
A conceptual drawing shows how the arched culvert will look, in a view to the east. The word "channel" refers to where South Douglas Creek will flow through the culvert next to the Sinton Trail.
Courtesy of City Engineering
The sinkhole cause was identified as seepage from a corrugated metal storm pipe that had carried South Douglas Creek's flow. This failure compromised the compacted dirt supporting the roadway about 30 feet above. (Note: Engineers call this configuration a "bridge," even though the road does not span the creek in the traditional sense.)
       The new bridge design calls for a 36-foot-wide concrete culvert in place of a metal pipe to carry the creek water. It will have higher flow capacity than before and include a raised path for the Sinton Trail, which currently crosses Chestnut Street at Ellston.
       The bridge is less than a mile north of Fillmore/I-25, where SEMA is in the final months of a $15.1 million contract with the Colorado Department of Transportation (CDOT) to replace the 55-year-old bridge at that location and upgrade its ramps.
       The city had been aware of the Chestnut/South Douglas Creek pipe problem long before the sinkhole issue, having included the project as an A-list item when voters reapproved the Pikes Peak Rural Transportation Authority (RTA) sales tax in 2012. The original schedule called for the pipe replacement in 2019, but it became an immediate priority in August.
       The $2.9 million contract for SEMA is noticeably higher than the RTA's $1.8 million estimate in the 2012 election. The board did not object to the change,
This aerial photo/ rendering of the closed-off part of Chestnut Street (in tan, marked with "road closed") was displayed in a poster that City Engineering and its design consultant presented at the public meeting Oct. 8. It also shows the realignment (in yellow) of the Sinton Trail, which now crosses over Chestnut. In the new configuration (shown as "potential" at the meeting), the trail will avoid traffic by using the new Chestnut drainage culvert.
Westside Pioneer photo of City Engineering graphic
agreeing with a City Engineering proposal to move funds from other RTA projects in which costs have been lower than expected.
       Regarding the Chestnut increase, Chaves cited several reasons in a report to the RTA board and in follow-up questions from the Westside Pioneer.
       His report cited a “rise in construction costs and a final design encompassing more work than originally estimated, including significant [creek] channel excavation, stabilization and armoring, utility relocations, roadway restoration and ROW [right of way].”
       In response to questions, Chaves elaborated that construction costs, particularly on more complicated projects such as this one, have risen in general in the past year. He did not have a specific percentage, but said the increases are significant enough in certain construction aspects that the city will have to take them into account throughout the coming construction season.
       Improvements to the creek channel (about 100 feet above and below the bridge) had been anticipated, but the needs turned out to be more extensive “when we looked closer,” Chaves said. For example, he pointed out, it was hard to know before final design the exact scope of retaining walls and the extent of structures to prevent undermining on the upstream side and pooling on the downstream side.
       As for utility relocations, the city had foreseen that need also, but because the sinkhole shutdown was an emergency situation, the utility lines under the roadway had to be literally cut off and temporary diversions set up. This will make utility reinstallations more complicated and costly than if the project had been arranged in advance (as once expected), Chaves explained.
       The right of way cost will be to obtain some privately owned land along South Douglas Creek just downstream, on which the city currently has an easement to access the bridge for maintenance purposes. The city policy in such scenarios is to own both upstream and downstream sides outright, if possible; already at Chestnut, the city owns the necessary land on the upstream side, Chaves said.
       Another cost that was unanticipated before the 2012 RTA election is extending the pavement about 100 farther south and north along Chestnut Street to add to the new bridge's stability, he said.

Westside Pioneer/press release
(Posted 3/11/16; Transportation: (Major Roads)

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