Posted: 31/03/2015 at 18:08
If this was down to septic tank run-off your ground would be saturated. Is that the case? If this is the case there is a problem that needs sorting out by the owners of the septic tank.
Normally it is as Curmudgeon says. Fluid level in my tank is at least 3 foot below ground and the soak-away is lower. Nowhere have I dug into the surrounding ground and met run -off from the tank.