SJSinNYC-
I’m not at all familiar with “bubble collapse” water hammer, but that does sound like part two of cavitation (part one being when the cavity forms).
I’m sure Con Ed engineers are more knowledgeable than yours truly about fluid dynamics, as well as other things needed for power generation (hydroelectric, steam generation for Manhattan, etc.)
“…wont be back until monday” – Will my lights stay on until then?