Though the South Fork Dam had a long history of disfunction, most survivors of the Great Flood blamed the dam's failure on the South Fork Fishing and Hunting Club, an exclusive resort located near the dam.
Club members were mostly wealthy Pittsburgh industrialists, including a young banker named Andrew Mellon. Repairs made by club owners--raising the lake level, and building cottages and a clubhouse to create a secretive retreat--made the area more vulnerable to massive flooding.
Despite evidence of its shoddy condition, no successful lawsuits were ever brought against club members for its failure and the resulting deaths downstream. The court held that the event was an Act of God, for which no one could be held responsible.
Below is a report of the flood printed in the Evening World, on June 1, 1889.
"King Death!...The stream of human bodies which has been washed down the river mingled with the wreckage of the houses, factories and other buildings have been something fearful to witness. At present it is utterly impossible to estimate, even approximately, the damage done...
The foundation of the South Fork dam was known to be shaky a year ago, and leakages have been numerous. It appears that the loss of life at Johnstown was incurred through neglect and disbelief."
Johnstown Flood Wikipedia entry
Johnstown Area Heritage Association
Andrew Mellon Wikipedia entry
Also, check out David McCullough's book on the Johnstown Flood.