The leak down under
On a Friday morning in late July, the southbound lane of Railroad Avenue between Third and Fourth streets was closed for several hours, allowing crews to fill in a spot where the asphalt sank due to underlying water saturation. The fix, explained Public Works Superintendent Bobby O’Dell, was a short-term one intended to give the city more time to come up with a potential solution.
Now, after having examined four proposals ranging from $25,000 to $75,000, council is expected to decide at its next meeting on a solution to the problem, which is in itself a strange one, according to O’Dell.
City personnel first noticed the sinkage in the fall of 2014, at which point the city started monitoring it, City Engineer Rick Barth told council last Wednesday. The problem grew as 2015 progressed, which led to an investigation into the issue.
The investigation revealed several peculiar aspects down below. First, the city discovered a 6-inch concrete slab running from sidewalk to sidewalk between Third and Fourth streets. Neither the city nor the Colorado Department of Transportation knows when or why the slab was installed, O’Dell said.
When a waterline was installed in 2004, the contractor cut through the slab and failed to reattach the two pieces. While the cut created a scenario where the slabs could shift, there was no noticeable problem until last year.
With increased rainfall last fall and one of the wettest springs on record, the city determined underlying moisture was exacerbating the problem and causing the slab to sink. However, the source of the moisture was not discovered until the city ran a video through a storm-water pipe underneath Railroad Avenue.
The video revealed leaks in at least three locations, including a two-sided leak near the mid-line of the pipe. When the pipe becomes a third of the way full, it leaks out of the holes in the mid-line. Additionally, at least two joints appear to be leaking from the bottom.
While there could be other sources of moisture, the leaks in the storm-water pipe are undoubtedly contributing to the problem, Barth told council.
In a memo to council, Barth and O’Dell presented four different solutions ranging in cost, impact and potential effectiveness. All four are designed to stop the leakage without replacing the entire line, which could cost in the neighborhood of $150,000.
The cheapest of the four would involve spot repairs of the known leaks, requiring night work, excavations and paving repair at a cost of $25,000. Aside from major impacts to the road, the other drawback, as noted in the memo, is the spot fix would not address any unknown or potential future leaks in the line.
The second and third solution would both cost an estimated $30,000 and involve slip-lining the pipe — one with fixed pipe and the other with a resign stock. The first would provide structural support but likely require excavation at one manhole, while the second may not require that excavation but would not provide the structural integrity.
The fourth and most expensive proposal at an estimated $75,000 involves reconstructing a new pipeline to the west down Fourth Street — effectively removing a utility from the busy Railroad Avenue corridor.
As Councilor Joe Elliott noted during the work session discussion Aug. 19, West Fourth Street is still in good condition, and it doesn’t make sense to dig up a good street when so many in the city are in need of repair. City staff agreed with Elliott’s statement. The present issue is more of a utility issue, rather than a road issue, Barth said.
At the meeting, Elliott along with Mayor Randy Winkler and councilors Barb Clifton and Jay Miller leaned toward the third option involving a resign stock slip-line, which O’Dell, when asked what he would do if he were in council’s position, said would likely be the least intrusive most reasonably priced option.
A local contractor is in talks with a larger company and if those are successful, the project would be done as a demonstration at a reduced cost, O’Dell said. Since those negotiations are ongoing, he declined to name either company.
However, the council members present at the work session debated the issue of other sources of groundwater, and whether or not fixing the storm-water pipe would solve the problem.
There is groundwater all over the city, Barth said, adding “we’re not guaranteeing it’s going to solve the problem but at least we’ll eliminate the storm-water contribution.”
A formal proposal is expected to appear before council at its Sept. 2 meeting.
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