I-70 storm flooding in Denver project zone prompts investigation

State project officials for the $1.3 billion rebuild of Interstate 70 through northeast Denver say they will investigate after severe flooding Sunday night in an under-construction section required the rescue of motorists.

“Safety is always CDOT’s number one priority, we will do what it takes to help prevent something like this from happening again in the future,” Stacia Sellers, the spokeswoman for the Colorado Department of Transportation’s Central 70 project office, wrote in an email late Sunday.

The Denver Fire Department reported that its firefighters rescued 11 people from their waterlogged or stranded vehicles on the highway near York Street, on the westbound side. The flooding closed I-70 for hours, with the highway reopening about 10 p.m.

Flooding occurred in a 1.8-mile recessed, mostly open air section that was built below ground level between Brighton and Colorado boulevards to replace an old viaduct. That section is nearing the completion of major construction later this year. It’s the most complex portion of the 10-mile Central 70 project, requiring a stormwater drainage system that includes 6-foot-diameter pipes and eight detention ponds.

But that system is not yet complete, Sellers said in the Sunday night statement. Still, it’s “nearing completion,” she wrote — and now project officials will probe what happened to overload the system.

“The Central 70 Project is going to conduct a thorough investigation to determine what exactly caused the flooding this evening,” Sellers wrote. “As an active construction project, if there are any system failures, we are able to go in and remediate any issues that occurred during this event and have everything in order before the project is officially complete.

“However, without conducting the investigation, we do not know if there was a system failure.”

The drainage system, once complete, is designed to channel water off the freeway surface during a 100-year flooding event, according to project documents and CDOT’s comments before construction began four years ago. That is the same standard as a similar drainage system built for a recessed section of Interstate 25 in Denver, between University Boulevard and Broadway, during the T-REX reconstruction project that was completed in 2006.

It was unclear if Sunday night’s rainfall over I-70 neared the 100-year event threshold.

During construction, Sellers said, an interim arrangement during heavy rainstorms includes having the lead contractor, Kiewit Construction, send workers to pump water to offset the lack of a full drainage system.

In the recessed highway zone, the eastbound side’s traffic now is in its final configuration, as of last month, but the westbound side remains in a temporary setup, with crews planning to remove remaining concrete barriers in coming weeks.

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