"We didn't know (there was going to be a drought), but we didn't want to bank on one thing, either," he said.
Filming of the documentary, which began in early July, will restart Sunday with shooting at the Middlekauf farm near the battlefield. On Monday and Tuesday shooting will take place on Bloody Lane, followed by filming Wednesday at Burnside Bridge.
Graham said additional footage will be shot later, including interviews on the battlefield, but the bulk of the filming will be complete after next week.
"That would fairly wrap up the major stuff," he said.
Three acres of corn that were to be used in the filming were planted in the spring - using authentic planting patterns that were applied during the Civil War era. The crew hoped to shoot the scene near its actual location this month.
The Cornfield was the site of the first fighting on the morning of Sept. 17, 1862, the bloodiest day in the nation's history. Some 23,000 men were killed or wounded at Antietam.
But filming plans were scrapped when the corn didn't grow as tall as the re-enactors who were to be in the scenes.
"It's lousy looking, and the stuff back in Michigan is fabulous," Graham said.
He said action in the Michigan corn, which has grown 14-feet tall, will be shot later this month.
Graham said there are still "several possibilities" for the documentary's release, ranging from a two-hour film to a four-hour "dramatic documentary" with acting scenes. The more extensive version would require more location shooting next year, he said.
"It would be a major documentary," he said.