SINKHOLE STREET: What’s caused so many collapses along Oxford Avenue?

BY NINA JOSS NJOSS@COLORADOCOMMUNITYMEDIA.COM

e sinkhole that opened on Oxford Avenue on June 22 happened on the same stretch of roadway where at least ve other sinkholes have occurred since 2015, according to the City of Englewood.

City sta said more investigation is necessary before they can determine the cause of the most recent sinkhole, but they do not believe the failure was related to the previous sinkholes in the area.

“We really need to know and understand what the issue is at the current sinkhole to understand what’s going on in the area, if anything,” Public Works Director Victor Rachael said.

e current leading hypothesis about the cause of the recent hole leads the city to believe that the various failures have been unrelated, he added.

With the recent sinkhole happening east of Santa Fe Drive just inside Englewood and most of the others west of it, the road failures have been split between the cities of Sheridan and Englewood. But because the Oxford Avenue storm pipes running from South Windermere Street/South Navajo Street to the South Platte River carry Englewood stormwater, e City of Englewood maintains them in both cities. impact on many of our residents, residents that are visiting our city and we know that these are inconveniences … for drivers,” he said at a June 26 study session. started working to repair the sinkhole on June 23, is trying to gure out why the pipe failed — especially considering its recent inspection.

City Manager Shawn Lewis said approximately 11,500 vehicles drive on Oxford Avenue daily.

What caused the sinkhole?

In 2019, the storm pipe under Oxford Avenue was deemed safe during an inspection, Rachael said.

In the study session, Rachael said the leading theory is that an “unrestrained joint” caused the sinkhole.

When a uid ows through a rigid pipe at a bend, the force puts pressure on the pipe, Rachael explained in an interview with the Englewood Herald. A “restrained” pipe has a block or restraint on the other side of the bend, often in the form of a manhole, to help absorb the force and prevent the pipe from breaking.

If there is no restraint, however, the pipe is at risk when large quantities of stormwater ow through it.

During the June 22 storm, the area received approximately 1.2 inches of rain in a 40-minute time period, according to a rain gauge in Rotolo Park, Rachael said.

“ ere were several 45-degree angle turns without restraining (in the storm pipe),” he said. “So without blocking, restraining or a manhole, those are susceptible unfortunately — under large events — to additional strain. And once a small seam breaks, then you start to get the sinkhole action where soil lique es and pulls back into the pipe.”

Rachael said it’s hard to know for sure why the pipe would not have been restrained at that section, but