A $1.2 billion proposal to widen and toll parts of Interstate 70 through northeast Denver is being called one of the country’s most wasteful highway projects by a national public interest group.

But state planners for I-70 say their designs for the highway will improve local neighborhoods, cut congestion and provide welcome alternatives for motorists. They said the project is a 100-year investment in the corridor.

“We will have an express lane to encourage car pooling, a commuter rail line will soon be opening nearby, … these are the types of projects we want to see developed,” said Rebecca White, spokeswoman for the east I-70 project. “We are going to do this in a very thoughtful way.”

Still, a report by the Colorado Public Interest Research Group, or CoPIRG — unveiled under the shadow of the I-70 viaduct near Swansea Elementary School — says the I-70 proposal will burn up at least $58 million in taxpayer dollars. That’s funding that could go toward investing in other forms of transportation, like a commuter bus service or in programs to discourage driving, said Danny Katz, director of the CoPIRG Foundation.

CoPIRG lumps the I-70 proposal with 11 national highway projects that will waste at least $24 billion in tax dollars. The report says the projects are “wrongly prioritizing expansion over repair of existing infrastructure” and are based on poor projections of future needs.

“While replacing a crumbling viaduct that needs to be addressed, Colorado proposes wasting millions of dollars widening the road and increasing pollution in the surrounding community,” the report says.

At a news conference Tuesday near Swansea Elementary, which is next to the I-70 expansion area, Katz said the viaduct is a “dirty mess” but added that expanding the highway to 10 lanes is not needed.

“We need to be spending our limited transportation dollars on repairing and maintaining our current roads and bridges and investing in transportation solutions that reduce the need for costly and disruptive highway expansion projects,” Katz said.

He said research shows that adding more lanes on highways does not solve congestion, but rather creates more traffic in which more drivers spend more time behind the wheel.

CDOT, however, says its plan remakes a badly worn highway while also adding alternatives like toll lanes. They will encourage motorists to get off the general purpose lanes and relieve congestion. The agency says the section of I-70 is congested up to 10 hours a day and carries up to 220,000 vehicles daily.

“I-70 can’t handle the traffic now, and we are looking at a 40 to 50 percent growth over the next few years,” said White. “If we do nothing, you can expect it to take 65 minutes to travel 12 miles on the highway.”

CDOT wants to remove the deteriorating 50-year-old viaduct on I-70 between Brighton Boulevard and Colorado Boulevard, lowering the highway below grade and adding two tolled express lanes in each direction.

The viaduct would be replaced with a 4-acre green cover near the elementary school. This will reunite the Swansea and Elyria neighborhoods.

The plan has also garnered support from various groups including the Denver Chamber of Commerce, National Western Stock Show, Union Pacific Railroad and the Elyria-Swansea Business Association.

A study of the environmental impact of the plan can now be reviewed this month and will be the subject of three public hearings in February.

CoPIRG is part of a national consumer research group that is funded by donations and with a mission of “standing up to powerful interests.” CoPIRG emerged in the 1970s on college campuses and is considered by many to be a left-leaning watchdog group.

Thad Tecza, a vocal critic of the I-70 plan, says it’s unlikely the CoPIRG report will do much to sway CDOT from canceling or altering its plan, which he says is plagued by environmental and fiscal problems.

“There used to be a song about Vietnam that said we were slowly but surely being sucked into the big muddy, and I think that is what is happening here,” said Tecza. “But hope springs eternal that this will be stopped.”

Monte Whaley: 720-929-0907, mwhaley@denverpost.com or @montewhaley