“We are trying to fix the sins of our fathers and mothers,” said Shailen P. Bhatt, executive director of the Colorado Transportation Department. “But I can’t fix — I can’t go back to 1950 and not put a highway through here. What I can do is, I can mitigate to the extent possible. I can reconnect the neighborhood. I can fix the school. And I can do the right thing by the people who we are relocating.”

Many people say that is not enough, and the project is among the most controversial in a city buzzing with construction.

Already, children living by the highway have asthma hospitalization rates 40 percent higher than Denver as a whole, and residents die of heart disease at a rate 13 percent greater than the rest of the city, according to city data.

In Elyria-Swansea, where the Sanchez family lives, the effects of the interstate are compounded by the factories and railroads that dot and crisscross the area. More cars, residents fear, will mean more health problems. One recent assessment, by the property database Attom Data Solutions, called the neighborhood the most polluted in the nation.