A group of community activists has filed an environmental lawsuit ahead of a Monday deadline for any remaining legal challenges to the $1.2 billion expansion of Interstate 70 through northeast Denver and Aurora.

And late in the evening, the Sierra Club and several community groups filed a second new lawsuit against the I-70 project, based on concerns that the expanded highway would violate federal air-quality standards.

The first lawsuit’s filing came with the revival of a longstanding claim: that the Colorado Department of Transportation and the city of Denver obscured what the activists, and even some City Council members, see as an obvious reliance by the I-70 project on a separate set of city storm-drainage projects called the Platte to Park Hill program.

City and CDOT officials, however, maintain a more nuanced position. They say CDOT has planned an independent drainage system of pipes and retention ponds, and it likely would be able to reduce the size of that system if the city proceeds with its complementary neighborhood drainage improvements.

Regardless, the lawsuit contends that the yearslong environmental impact review process conducted by CDOT for the urban highway project should have considered the effects of the city’s drainage project — and because it didn’t, the review failed to cover all of I-70’s drainage needs in the interest of avoiding project delays. The suit says both projects will negatively affect nearby lower-income and majority-Latino neighborhoods, disturb contaminated soils and pollute the South Platte River when runoff from a lowered section is channeled into it.

“This isn’t our preferred alternative to work against the project,” said activist Brad K. Evans during a morning news conference outside the U.S. District courthouse in downtown Denver.

But the new lawsuits are part of a coordinated, multipronged legal strategy by a wide-ranging group of activists across several Denver neighborhoods. They join two other pending lawsuits against the highway and city drainage projects.

Opponents’ efforts so far have failed to stop them, but backers of the new suits say they’re optimistic.

“This is a boondoggle,” said Evans, flanked at the announcement by about 40 community members, project opponents and a few elected officials. “We’re after justice, we’re after transparency and we’re after accounting on this project.” Including a future phase, “this is a $2 billion project that’s likely going to cost much, much more.”

His lawsuit was filed Sunday by the Denver law office Keating, Wagner, Polidori and Free. His fellow plaintiffs are Kyle Zeppelin, Kimberly Morse, Jacqueline Lansing and Christine O’Connor.

Named as the defendant is the Federal Highway Administration, which granted federal approval for the I-70 project in January. The legal filing seeks judicial review of that decision. An FHWA spokesman said the agency doesn’t comment on litigation.

CDOT plans to kick off five years of construction early next year on the funded first phase of the project, estimated at $1.2 billion. It calls for the widening of the six-lane freeway between Brighton Boulevard and Chambers Road to add a new managed express toll lane in each direction. The project would replace a crumbling 1.8-mile viaduct with a below-grade highway between Brighton and Colorado boulevards, through Elyria-Swansea.

Part of that section would be topped by a 4-acre parkland cap next to Swansea Elementary, the largest of several community concessions offered by CDOT.

A statement issued by CDOT expressed confidence in its 14-year environmental review.

“CDOT is confident that our unprecedented community outreach process and our thorough technical analysis meet and exceed the standards set by the National Environmental Policy Act,” Central 70 project director Anthony DeVito said. “We believe this process, our analysis, and this project will stand up under the toughest legal scrutiny.”

That is what CDOT’s work is now likely to get in the courts, and attorney Melissa Hailey said Monday that in coming weeks she planned to seek an injunction pausing both the highway and city drainage projects.

“Cities around the county have figured out that 1960s-era urban highways through minority neighborhoods are some of the worst planning practices from the last century,” said Zeppelin, a developer in Globeville and the River North area. “And now, with a booming economy, it’s time to invest in people and the future with transit, green infrastructure (for storm drainage) and affordable housing.”

Said Jim Alexee, the Colorado chapter director for the Sierra Club: “It’s incumbent upon state and federal entities to fully appreciate and honor the basic human right to breathe clean, healthful air. Neither the state of Colorado nor the federal government has done so in their planning and approval of Central 70.”

The Sierra Club’s lawsuit against the FHWA includes the Elyria and Swansea Neighborhood Association, the Colorado Latino Forum and the Chaffee Park Neighborhood Association as plaintiffs. It’s based on air pollution concerns and health issues caused by the highway, as well as what the plaintiffs consider CDOT’s inadequate consideration of an alternative that would remove I-70 through northeast Denver, rerouting the traffic along interstates 270 and 76 to the north.

CDOT has rejected that option as unrealistic.

“All metro-Denver residents should be alarmed at the callous disregard for the quality of our air shown by CDOT, as well as by our state and city leaders,” says a statement provided by Drew Dutcher, president of the Elyria and Swansea Neighborhood Association. “The healthy environment that makes our region so attractive is already severely compromised in residential areas along I-70 and is further threatened by this ill-conceived, excessive and destructive expansion.”

Does I-70 depend upon city drainage plan?

The city’s drainage work in northeast Denver, estimated to cost $267 million to $298 million, includes a new river outfall at Globeville Landing Park and a detention area on City Park Golf Course. Crews already are working at the Globeville park.

CDOT on Monday reiterated the department’s longstanding position on the relationship between the projects:

“The drainage system for the Central 70 Project described in the Record of Decision is a standalone system that is separate from the city’s projects proposed for City Park and Park Hill,” project spokeswoman Rebecca White wrote in an email. “The I-70 system is independent, and includes a series of underground pipes and detention ponds. It has been designed for flows assuming the city’s projects are never built. Improvements made by the city of Denver might enable CDOT to build a smaller system of pipes and detention ponds.

“However, unless the City builds its system, CDOT will proceed with its independent design. If future changes are needed to the Central 70 drainage system, those will be separately evaluated prior to the start of construction.”

Such assertions haven’t mollified critics in the past.

Those city drainage projects will help protect a new below-grade section of I-70, city officials have said, but they insist larger city storm-drainage needs — and not I-70 — were the impetus. But CDOT and the city struck an intergovernmental agreement to share some costs for both projects, complicating public perceptions.

“Numerous documents show there is a direct connection between the two,” Councilman Paul Kashmann wrote, citing that agreement as an important link, in a lengthy public Facebook post criticizing the project Monday.

Activists cite 2014 document as evidence

The lawsuit’s backers on Monday released an internal 2014 city report on Montclair Basin drainage that they say is supportive of their position, that CDOT and the city purposely obscured CDOT’s need for the city drainage projects to support I-70.

The feasibility evaluation says CDOT’s then-project manager for I-70 had “confirmed from his management team that CDOT cannot include any of the Montclair Creek open channel projects in their design/build contract for the I-70 PCL project” because such a change in scope would require the restarting of the I-70 environmental review process.

Asked about that document, Denver Public Works spokeswoman Nancy Kuhn wrote in an email that it was the city that had considered asking to include the drainage plans in the I-70 environmental review — not CDOT.

“The city explored a wide range of options to address the flooding risks in the Montclair Basin,” she said. “Ultimately, we decided that the best solution for the city’s needs would be to build our own project independent of Central 70.”

A separate lawsuit is pending against the City Park Golf Course portion of the city drainage program, while I-70 already has been targeted by an earlier Sierra Club lawsuit challenging the federal air-quality standards that allowed the project to proceed.

I-70 opponents have said that the air-quality standards suit, if successful, could halt the project, while the type of challenge filed Sunday — under the National Environmental Protection Act — is a challenge of the approval process and may only delay the project by requiring more analysis of the impact.

Monday marked the deadline for lawsuit against the project because it came 150 days after federal approval for the project was published in the Federal Register.

CDOT executive director Shailen Bhatt said after the project received the FHWA’s green light that another round of lawsuits was all but inevitable. But he expressed confidence the project would be able to move ahead.

Update (12:20 p.m. July 11, 2017): This story was updated to reflect that the Sierra Club filed its lawsuit against the Federal Highway Administration in the late evening on July 10, as expected. That lawsuit is the second document embedded below.

Neighborhood activists’ lawsuit:

Sierra Club lawsuit: