Wassenaar (1995) also noted that although nitrate derived from human wastes in domestic septic systems would be indistinguishable isotopically from animal wastes, less than 10% of the nitrate in the aquifer could be derived from septic systems based on the estimated density of septic systems above the aquifer.
En de nombreux endroits, le champ d’épandage souterrain des fosses septiques s’étend sous l’horizon de sol, dans la couche perméable de sable et de gravier.