Dodgeman is correct about about the constructing a leach field in a high water table. It doesn't happen. Most states require aminimum of 2' to 4' separation. It sounds like a leaky septic tank. You probaly have ground water leaking into the septic tank. This needs to be repaired! This situation could cause flooding in your leach field causing it to fail premaature. You should contact the tank manufacture and have them repair the tank.