The tropical depression that dumped record rain throughout the Mid-Atlantic in June 1972 severely tested Maryland's Conowingo Dam. The landmark engineering project is the subject of a new Maryland Public Television documentary, “Conowingo Dam: Power on the Susquehanna.”

Tropical Storm Agnes caused state officials to consider blowing up part of the dam to allow the swollen Susquehanna to escape the structure between Harford and Cecil counties. The documentary examines the trials the dam has faced since its construction in 1928. (It is available on demand from the MPT website (video.mpt.tv). It will also air at 8 p.m. July 6 on MPT-2.)

The documentary contains archival footage of the structure's construction. Its builder, a Boston-based firm, commissioned the film about the construction project.

MPT's Michael English discovered the movie, shot in 1927 and 1928.

“We were about ready to complete the project,” he said. “Amazingly, the film turned up on eBay.” He said a California-based film director was selling part of a collection.

The film, now incorporated into the documentary, revealed how a small army of construction workers lived in compounds along the river as the dam was constructed. Several workers died during the project. English said that he could find no member of the construction team to interview.

jacques.kelly@baltsun.com