On Site Waste Water Treatment Systems

In the absence of sewerage, it is necessary to provide an on-site treatment system for each dwelling house.  In deciding on the location of such systems Sligo County Council insists that planning applicants and their agents must have regard to the protection of the environment.

On site treatment systems must be designed, and installed properly and maintained regularly for the system to function satisfactorily. Public health and water quality are threatened when on site systems fail to operate correctly.

Guide to On-Site Treatment Systems (PDF) - 247 kbs

Potential Detrimental Impacts

Poor design and installation of systems can result in significant problems including:

  • Surface ponding of effluent causing a public health hazard
  • Surface water pollution
  • Groundwater contamination
  • Odour nuisance
  • Insects, rodents and pests that create health problems.

Problems may be caused by one or more of the following:

  • Inadequate permeability in the soil/subsoil
  • Use of soak-pits or general absence of percolation areas
  • Septic tanks/soak-pits connected directly to a watercourse.
  • Poorly designed, constructed and/or installation of septic tanks
  • Inadequate maintenance of systems
  • Connection of rainwater or surface water into the septic tank
  • Not connecting baths, washing machines etc to the septic tank.

The key to installing a reliable on-site system, that minimises potential pollution, is to identify a suitable treatment system following a thorough site assessment.

An application for planning permission must contain sufficient information to ensure the proposed development will be environmentally sustainable. It is a requirement that all planning applications which include an on site treatment system are accompanied by an Environmental Protection Agency Site Suitability Assessment and that Sligo County Council’s On Site Treatment System Technical Guidance document is strictly adhered to.

Planning applications for one off houses, in water sensitive catchments, were assessed by the Environmental Services Section.

An educational campaign has also been developed to target existing septic tank owners with the aim of improving maintenance of the tanks and to encourage the use of phosphate-free products. Sligo County Council is also in the process of drafting an information leaflet regarding on site treatment systems.