Pumps that should have drained water along a section of Interstate 70 under construction in northeast Denver failed to turn on Sunday evening, contributing to severe flooding that required the rescue of nearly a dozen stranded motorists, according to the lead contractor on the $1.3 billion highway rebuild.
“An error in the drainage pump system appears to have prevented the pumps from turning on automatically,” Kiewit Infrastructure Co. said in a statement Monday. “Once this was determined, Kiewit turned the pumps on manually. After the pumps turned on, the area was drained in a short period of time.”
A Kiewit superintendent on the Central 70 Project noticed flooding on I-70 and on the south side of 46th Avenue around 7 p.m. Sunday, the company said, and dispatched a crew to troubleshoot problems in the drainage system, which still isn’t complete.
Kiewit expressed confidence the system should work properly in the future and handle much larger rainstorms than the one that pummeled metro Denver on Sunday evening, dumping as much as 2.5 inches of total rainfall in some areas.
At the height of the storm’s intensity, a measuring station east of downtown Denver recorded 1.76 inches of rainfall in 26 minutes, according to the National Weather Service.
The deluge sparked flash flooding along I-70 on the northeastern edge of the city, as well as around City Park and other parts of Denver.
On Monday, state project officials said they would ask Kiewit to investigate what went wrong to prevent failures in the future.
“Like everyone, we are relieved no one was hurt during last night’s storm that flooded part of the lowered section of I-70, and we appreciate the efforts of Denver first responders to help people out of the water,” said Stacia Sellers, the spokeswoman for the Colorado Department of Transportation’s Central 70 project office, in an email Monday.
She said CDOT has asked Kiewit to investigate every possible contributing factor, with a particular focus on the water diversion and pumping systems, the current conditions during construction, and any previously unknown issues.
“They will be sharing these details with CDOT and the public as soon as we learn additional information. CDOT will hold the contractor accountable for meeting all the obligations under the contract, including ensuring full functionality of the drainage system,” she said.
The Denver Fire Department reported that its firefighters rescued 11 people, including three children, from their waterlogged or stranded vehicles on the highway near York Street, on the westbound side. After heavy rain fell in a short amount of time, flooding closed I-70 for about two hours, with the highway reopening about 10 p.m.
The fire department also reported rescuing eight people, including an infant and other children, from a minivan submerged in the underpass of 38th and Blake streets. Other spots with flooding that necessitated rescues Sunday included 46th Avenue and Washington Street, 23rd Avenue and Colorado Boulevard, and 14th Avenue and Krameria Street, according to the Denver Fire Department.
No injuries were reported amid the 29 total rescues, fire officials said.
Flooding occurred in a 1.8-mile recessed, mostly open-air section of I-70 that was built below ground level between Brighton and Colorado boulevards, near the water table, 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.
Kiewit expressed regret that motorists became stranded and gratitude to the Denver Fire Department for its “quick and effective response.” The company also said it was working with CDOT to pinpoint exactly what went wrong and to improve its protocols so future storms can be managed during construction and after completion.
“Until the final investigation is completed and results are available within the month, we have put processes in place to ensure the pumps will turn on properly for future weather events to avoid issues like this in the future. The team is also investigating all areas along the corridor to ensure they are functioning properly,” the company said.
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.
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 the remaining concrete barriers in coming weeks.
