It would have been “unthinkable,” Afton Mayor Richard Bend said, to cancel one of Washington County’s most popular summer events just because the rebuilt St. Croix Trail downtown didn’t yet have a final coat of asphalt.

Or because new boulevards weren’t yet planted, or side roads remained in various states of reconstruction.

“Never. We never even considered it. How could Afton never have its Fourth of July parade?” the mayor asked.

And so it happened. Afton, population about 2,900, surely grew in size tenfold as paradegoers swarmed over the unfinished street and sidewalks. Even the toe-stubbing curbs, temporarily higher than normal until the final layer of asphalt is applied, didn’t dent the celebration.

The makeover of St. Croix Trail, also known as County Road 21, is just one feature of the city’s $12.5 million public works project that includes upgrades on 17 miles of side streets, rebuilding the levee along the St. Croix River waterfront, and installing a new sanitary treatment plant to replace individual septic systems that leaked raw sewage into the river.

The joint city-county project is one of the largest in Washington County this summer.

The county’s portion — improvements on St. Croix Trail, the main thoroughfare where the parade was held — will be completed in August. Residents told engineers they wanted improved traffic and parking lanes, wider and extended sidewalks through downtown and better pedestrian crossings, which will result in a narrower road that’s safer to cross, said Frank Ticknor, a county traffic engineer.

St. Croix Trail “started a long time ago as a gravel road through the village,” said County Engineer Wayne Sandberg, and became a sea of patches and overlays over the years.

Before the reconstruction, the road lacked water drainage and sometimes shed rivers of rain through residents’ garages. “We weren’t even sure where some of the water was going,” Sandberg said.

Putting major construction on pause to hold a parade and other summer events isn’t common practice, but he said that work was scheduled accordingly.

“One of the questions we asked was, ‘Can the parade not happen?’ We have to ask that question. The city was clear from the beginning there would be a Fourth of July parade in 2017,” Sandberg said.

The rest of the story plays out in Afton’s extensive infrastructure improvements.

Bend said the sprawling project won’t change “the quaint river city appearance in Afton,” but it will result in a more inviting downtown. Cost to local taxpayers, he said, will run about $4 million.

And because of levee improvements, he said, downtown business owners soon will be free of a legal limit on how much money they can invest to improve their buildings in a flood zone.

Downtown’s Old Village will remain “low density,” meaning city zoning won’t allow significant growth.

The project couldn’t have been accomplished without the participation of the Valley Creek Watershed District and other “agencies most concerned with the environment,” Bend said, describing them as Afton’s “greatest benefactors.”

Sandberg said that building a construction project around a parade isn’t unprecedented in Washington County. It was done several years ago during an overhaul of Broadway Avenue in Forest Lake.

But what’s new is combining work on county roads with city projects to make improvements more affordable.

Washington County has done that recently in Marine on St. Croix and now in Afton, a small city historically hobbled by outdated and inefficient infrastructure.

“Every one of our projects now is an opportunity to do more than a county road and you’re seeing that with the communities now,” Sandberg said.

“It think it’s fair to say we both needed each other to get this done.”