30th Street Post Office - Second Sub-basement

In the late seventies I was working as a laborer for an electrical contractor who was rewiring 30th Street Post Office, which now belongs to the IRS. We had to go down into the second sub-basement, which is three floors below street level, to pull cables. I remember that the ceiling was very low. What amazed me was that there were drums and drums of water left over from the Cold War days to be used in the case of a nuclear emergency. I wonder if they are still down there.