(ONN) – The Ohio Department of Transportation says its employees have spent more than 20,000 hours helping with cleanup from tornadoes and other severe weather that swept through parts of the state in May.

ODOT says its cost for helping clean up damage caused by tornadoes, severe storms, straight-line winds, flooding and landslides has totaled more than half-a-million dollars.

21 tornadoes touched down during severe storms that swept through 10 counties May 27th and 28th.

During the tornadoes in Dayton, ODOT plow drivers used their plows to clear debris off of Interstate 75.