"The department believes that this action was not necessary," it said in a statement.
But the department believes that some increase is inevitable anyway.
The department believes radioactive material would move only slowly with the flow of water deep underground.
He said the department believed that it might be premature to start pumping by this month.
"The department acknowledged the abuse, tried to address it and believed that they had," he said.
But he said the department now believes the decision was wrong.
The department had believed the girl was a runaway.
His department believes that may have resulted in fewer children being screened for lead.
But each department believes it can handle any event.