The effects of the Aug. 10 derecho, a violent thunderstorm system that struck Iowa with 100-mph winds, are still being felt as rebuilding has begun.

One of the cities hardest hit by the storm was Cedar Rapids, where it is estimated that more than 800 buildings experienced partial collapse of the roof, walls, ceiling or floors. Among the damaged buildings was the city-owned ice arena, ImOn Ice, which had half its roof torn off, as well as more than 20 school buildings in the city.

Some of the counties that suffered the most destruction include Story, Ames, Marshall, Linn and Clinton counties.

John Boston, director of engineering for Alliant Energy, the biggest gas and electric distribution utility in the state, estimated that 1,200 miles of power lines were downed during the storm. He also reported more than 3,100 poles were affected, along with overhead transformers and underground equipment, for which he didn’t yet have a damage estimate.

At the peak, about 256,000 Alliant customers were without power. As of Aug. 20, that number had been reduced to about 18,000.

Another result of the rare and violent storm is the large number of trees that were felled, and which city crews have been working to clean up. “All those trees landed on lines, poles and wires and in some cases even underground transformers were damaged,” Boston said.

“What we’re dealing with most is tree debris,” said Jen Winter, public works director for the city of Cedar Rapids.

She estimated that about 25% to 50% of the tree canopy came down, but said the city won’t have a clear picture of the extent until they have a chance to compare before and after aerial photographs of affected areas.

“We’ve been hauling debris,” she said. “As of yesterday we estimate we’ve hauled 22,000 tons of material out of neighborhoods, and we’re estimating we’re only 25% to 30% done.”

In addition, all of the city’s 190 traffic signals received damage. In the wake of the storm, hundreds of streets were closed and the city used generators to get the signals running at main traffic intersections. “Now we’re moving those generators around to areas that don’t have power to get the signals up there too,” she said.

About 75% to 80% of the city’s regulatory signs were blown over or destroyed as well. Sign and traffic signal crews from other cities in Iowa have been working to restore signs and signals.

Utility companies including Alliant have provided additional crews that are focused on restoring power and communications. Boston said Alliant has about 1,700 electric linemen working to restore power and 500 tree-trimming crews helping to cut up fallen trees and get them out of the way. In addition, 140 to 160 members of Iowa National Ground are helping to remove trees.

Bob Doetsch, a spokesperson for ITC Midwest, which transmits energy to distributors such as Alliant, said it had restored electricity to all of its transmission substations by Aug. 18.

President Donald Trump signed on Aug. 17 a disaster declaration for Iowa.

“We’ve met with FEMA and we feel pretty confident that we’ll be able to get at least some level of reimbursement for our public infrastructure,” Winter said. She added that she expects all debris to be removed and public infrastructure, such as traffic signals, to be restored within 60 to 90 days. She estimated that it will take up to a year for the city to recover entirely.