Most commercial breweries use a plate chiller. It is FAR more efficient then an immersion chiller. It would take quite a lot of cold water to drop a bbl from boiling to pitching temps with just an immersion coil and tap water.
A lot will depend on the temp of your chilling water. You can get a dual stage plate chiller in which you can use ground water to drop to a certain temp and then a refrigerated glycol system to take it down to pitching temps.
Here in CO I have never needed anything other then ground water. In TX and AZ, a glycol system was mandatory.
Good luck in your endeavors.