After months of delay, heavy construction machinery began covering ground on Friday at the site of Williston’s new airport. 

Huge site graders, vehicles that level off land, scraped and piled dirt near a future runway, while representatives from Native American tribal groups watched closely for the unearthing of any artifacts, which are under the protection of federal law. 

Although work was scheduled to start on Monday, progress was limited to surveying and putting up fences to block off construction boundaries, along with the habitats of two birds discovered on the land. Workers cordoned off a patch of field and a tree where a mallard duck and great horned owl were living to make sure the birds can stay on the land, city administrator David Tuan said. 

“We could not start this until the fences were up as a protective measure,” he said, pointing out a large patch of land where a handful of vehicles were creating clouds of dust. 

Site grading, which will cover much of the project’s 1,500 acres northwest of Williston, is likely to take Martin Construction of Dickinson all summer to complete. 

The next step in the $250 million airport relocation, which will replace the existing Sloulin Field International Airport with the Williston Basin International Airport, is to reinforce the ground on the site of the terminal building with a thick layer of packed dirt. That work is likely to start within several weeks, while a reroute of 59th Street NW, which runs through the airport land, is scheduled to begin in May, Tuan said. 

A contract for runway construction is to be awarded this summer, and work on the terminal building, which is estimated to cost between $30 and $40 million, may start around August. 

Construction, which was originally expected to start last fall after a groundbreaking in October, was delayed when deed transfers and other paperwork from the $13.5 million purchase of privately owned farmland took longer than anticipated. 

A portion of a $27 million grant from the Federal Aviation Administration, $17 million of which was marked for the purchase of land, is expected to be deposited into the city’s bank account in coming weeks, Tuan said. About $10 million of the grant is to be used for a number of things, including engineering and preliminary construction work, while the remaining money from property acquisition may be redirected to other parts of the project, he added.