Note to nuclear plant designers: Don't carry tritium-water in underground pipes!
I remember we went through the same exercise at Pickering. Hole after hole was bored to find the leak, or the extent of the leak. Once you have it all located, you can usually stop the radioactive plume by using wells. Tritium decays quickly, and can never be detected in the lake water if it slowly oozes out of the ground.
As I've said before, in the old days if we got a dose of tritium, we just drank a lot of beer to get it washed out. It isn't very dangerous, and just serves to increase your general dose, that you get from airplane flights, xrays, granite counter-tops, and wallowing in the mud!