31/05/2006 -
In the interests of protecting our water quality, Sligo County Council have recognised the importance of designing on-site treatment systems which take account the characteristics of the site and the vulnerability of groundwater resources. The key to protecting water quality is to ensure that new development is guided towards sites where acceptable wastewater treatment and disposal facilities can be provided. The identification of suitable sites is largely dependent upon the quality of site suitability assessments being undertaken by consultants in preparing applications for planning permission.
With a view to improving the quality of information submitted for planning permission, it is recommended that applications for developments which include an on-site treatment system should have the site suitability assessment prepared by a member of a panel approved by Sligo County Council. For a full listing of approved assessors please view the Sligo County Council web-site at www.sligococo.ie or Tel: 071-9111111.
Rosie Morrissey, Environmental Scientist with Sligo County Council outlines the requirements for the provision of on-site treatment systems for houses not served by a public sewerage system.
In the past many planning applications which included on-site treatment systems had the following defects:
This invariably resulted in delays in the Planning Process, requests for further information and in some cases refusals of planning permission with the applicant’s time and money being wasted. The employment of consultants from the approved panel should ensure that only sites suitable for on-site systems are submitted for consideration. This should lead to a more efficient service for the public.
On-Site Treatment Systems
Houses located in rural areas, not served by public sewers, depend on either a septic tank system or a proprietary effluent treatment (PET) system to treat and dispose of wastewater. A properly designed, installed and maintained system can provide years of reliable low-cost service.
When systems fail to operate effectively, ground and surface water pollution, property damage, health risks and odour nuisance can occur. In this article, the Environment Section of Sligo County Council outline the steps that are needed to be taken to ensure that environmental pollution does not occur and that householders comply with planning guidelines.
The crucial elements of an on site treatment system are as follows:
An accurate site assessment is the key element to the provision of an efficient on-site treatment system. The site assessment should be one of the first tasks undertaken when considering buying a site and/or designing a house. If a site assessment fails, planning permission will not be granted for that site.
The overall responsibility for attaining accurate site assessment and the recommendation of an effluent treatment system should be done by a qualified site assessor. An assessor considers a wide variety of environmental factors such as soil depth and type, water table levels and proximity to wells and watercourses etc. to assess its suitability for effluent treatment.
Sligo County Council has formed a panel of consultants with particular expertise in the area of assessing the suitability of sites for treating effluent. Sligo County Council requires that applicants for one off houses in the country-side should engage the services of one of these consultants to carry out the site assessment and make recommendations.
System design
On-site treatment systems should be designed in accordance with the Environmental Protection Agency publication “Treatment Systems for Single Houses” and the Sligo County Council’s Technical Guidance Document. Both documents are available on the internet.
Designers should ensure that the effluent treatment system is sufficient to treat and dispose of the effluent and yet not be too complex. A septic tank and percolation area should normally be installed where site conditions are suitable.
It should be noted that some sites may pass the site assessment but not be suitable for the installation of a septic tank and percolation area – in these cases consideration may be given to the installation of an effluent treatment plant.
Septic Tank and percolation area
The conventional on-site treatment system is the septic tank system, which consists of a septic tank and percolation area. The septic tank:
The Percolation Area
The percolation area is a critical part of an on-site system, as most of the treatment takes place here.
Effluent Treatment Plants
Proprietary Effluent Treatment (PET) systems are used to treat wastewater from a dwelling where a site is unsuitable for a conventional septic tank system. They should not be regarded as an instant solution for all problem sites. It is crucial that systems are properly designed and installed, and that proper maintenance and monitoring procedures are put in place. Adequate capacity to allow for one year sludge storage should be provided with all PET systems.
Effluent treatment plants differ in effluent treatment process, size, electrical consumption, cost and complexity. In the rush to obtain planning permission and build, many applicants do not consider the implications of their on-site treatment systems. On sites, problems may not emerge in the first few years, but may do so in subsequent years. A long term view is necessary to ensure that there is no risk of water pollution or risk to public health from these systems.
Applicants should research the type of system before purchase to ensure the correct system is purchased for the particular site.
The following information should be requested:
The purchase of a wastewater treatment system is an extremely important long- term investment and this should always be borne in mind when purchasing.
Installation
Engineers/Architects with appropriate professional indemnity will be required to certify that the treatment system complies with the planning conditions and the Environmental Protection Agency Wastewater Treatment manual. The certificate should be retained by the householder and be made available to the Local Authority on request.
Photographs of the whole system should be taken by a competent person before backfilling to show that the system is installed correctly. These photographs should be certified and retained by the householder.
Maintenance
All single house sewage treatment systems require regular maintenance in order to prevent the risk of pollution. Maintenance includes de-sludging and monitoring of effluent from treatment plants and de-sludging of septic tanks. Documentary evidence of regular maintenance may be required to be submitted to the Local Authority.
Site Improvement works
It is sometimes possible to carry out site improvement works by drainage or the importation of suitable soils to allow for a proprietary effluent treatment system to be installed. Site improvement works requires a considerable degree of expertise, and should only be undertaken by an experienced competent company/engineer. The specialist engineer or company with indemnity insurance must design and supervise the installation, and sign off on the proposed system. Following improvement works/drainage work having been carried out on a site, the site must be reassessed after a sufficiently long period, to establish whether the improved subsoil is satisfactory.
This article aims to reduce delays in the planning process for new house builders and will be available on the Sligo County Council web-site: www.sligococo.ie for future reference.