Percolation testing


The code replaces previous guidance issued by the EPA on wastewater treatment systems for single houses (EPA, 2000) and incorporates the requirements of new European guidelines, recent research findings and submissions and comments received during the consultation process.


An assessment methodology for the determination of site suitability for an on-site wastewater treatment system and identification of the minimum environmental protection requirements.


A visual assessment which involves looking at the site and its surroundings to gain an indication of how well or poorly drained the site is likely to be and what targets are likely to be at risk in the area (e.g. Rivers and streams bounding a site, public or private wells in close proximity to the site).

ACS carries out site suitability assessments for on-site wastewater treatment systems under the EPA Groundwater Protection Scheme.

The EPA (Environmental Protection Agency) code of practice (CoP) establishes an overall framework of best practice in relation to the development of wastewater treatment and disposal systems, in unsewered rural areas, for protection of our environment and specifically water quality. The code replaces previous guidance issued by the EPA on wastewater treatment systems for single houses (EPA, 2000) and incorporates the requirements of new European guidelines, recent research findings and submissions and comments received during the consultation process.

This EPA code of practice sets out the following:

  • An assessment methodology for the determination of site suitability for an on-site wastewater treatment system and identification of the minimum environmental protection requirements.
  • A methodology for the selection of a suitable wastewater treatment system for sites in unsewered rural areas.
  • Information on the design and installation of conventional septic tank systems, filter systems and mechanical aeration systems.
  • Information on tertiary treatment systems.
  • Maintenance requirements for the above systems.

Site Suitability Assessment

In all cases where a planning application involves a proposal to use a septic tank or other on-site treatment system, a site assessment is required. This is to ensure ground waters are protected.

The system of site assessment required under the EPA document involves several elements:

  • A desk study which looks at available documented information on a site. This includes information on the soils, geology, location of wells and streams etc.
  • A visual assessment which involves looking at the site and its surroundings to gain an indication of how well or poorly drained the site is likely to be and what targets are likely to be at risk in the area (e.g. Rivers and streams bounding a site, public or private wells in close proximity to the site).
  • On-site investigations including an assessment of the soil profile up to a depth of 2m, or greater in some cases, and percolation tests to confirm the drainage conditions.
  • Recommendations as to the form of wastewater treatment, if any, are best suited to the site conditions.

ACS (Axiom Construction Services)
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