jeff_stockton, the appearance of septic tank effluent on the surface of the leach field is an indication that the clogging mat which is formed on the soil below the leach field has reduced the percolation rate of the effluent into the soil to a rate that is slower than the application rate. The effluent will flow in the path of least resistance, in this case, that path is to the surface at the edge of your leach field.
Do not ignore this potential threat to the environment, and threat to the public health (particularly your family’s health). In my view, the correct method of repair of the soil absorption system is to install a diversion valve in the septic tank effluent pipeline, and install another leach field. Alternating the effluent flow from one leach field to the other on an annual basis will give you the ability to control the thickness of the clogging mat, and therefor, the ability to control the percolation rate of the effluent into the soil below the leach field.
Monitoring and ventilation ports should be installed in each leach field so that the field which is in the “resting” mode can be ventilated with atmospheric air. The leach field riser port that is on the “in-use” field is fitted with a solid, threaded plug to prevent sewer gasses from emanating into the yard.
Expanding the size of the leach field will not be a long term solution to the problem. If alternating leach fields were installed from the “get-go”, and if you performed your annual septic system maintenance duties, you would not have this problem. JWA