Agricultural and Biosystems Engineering
An existing septic system (on-site sewage treatment system) may function well or it may "fail" due to a number of causes. Evaluating septic system failures is a skill that anyone involved with septic systems should have, including installers, building inspectors, system designers, septic tank pumpers, and the homeowner. Perhaps the single greatest cause of septic system failure is extra water entering the system. The extra water may come from leaky plumbing fixtures, but it commonly comes from poor surface drainage around the septic tank or pumping station. The soil absorption area may have been installed in a seasonally saturated soil that is at or above the rock level in the trenches or bed.
Derickson, Russ, "Septic System Failures" (2002). SDSU Extension Extra Archives. 33.