Density of Disposal Areas ​

Generally, high disposal system densities tend to produce greater deleterious effects, but much depends on site conditions. For example, groundwater may not exist in an area, or its natural quality may be such that its beneficial uses are already severely limited.

The 1998 NSW Guidelines On-site Sewage Management for Single Households refers (p.58) to US EPA, Victorian and Western Australian publications which indicate that in-ground disposal systems are polluting, or may be polluting, groundwater if their densities exceed between 15 and 25 systems per square kilometre.