On-site sewage facilities can treat residential sewage very efficiently if designed properly for the on-site conditions. But a shallow water table in the soil treatment zone is a particularly hazardous condition for OSSFs. 

Saturated soils will not treat wastewater. Standard gravity-fed systems that rely on subsurface soil treatment will fail during periods when a shallow water table is present in the 4-foot treatment zone.

Of all the limitations that must be examined as part of an on-site evaluation (texture, gravel, soil restrictive horizons, slope, floodplain), seasonal shallow groundwater is without a doubt the most difficult to analyze. 

All of the other limitations can be assessed by a simple and direct site evaluation in the field. But with shallow groundwater, the evaluator is almost always basing his or her evaluation on indicators, and not on direct observation.  This simple fact introduces considerable uncertainty into the process, increasing the chances that a bad call will be made, with the resulting surfacing of untreated sewage. A major public hazard by any measure.

This is an 8-hour TCEQ-certified (1487) course for the OSSF program.

This course is designed to help the site evaluator and others protect public health in the face of uncertainty, and to reduce their own liability from bad calls.

This is a totally independent online course that you take on your own schedule. You can stop at any point and automatically and come right back to where you left off.

Course Resources:

• Course Outline (a little bit about each lesson)

• Your Instructor