Outline of the Arterial Drainage Maintenance Programme and Appropriate Assessment

Follow on response from OPW to AIE on Pre-Publication of Works Planned under the Scheme, Appropriate Assessments and Community Engagement

Statutory Requirement for Arterial Drainage Maintenance by the OPW

Following the passing of the Arterial Drainage Act, 1945, the OPW began investigations to determine where Arterial Drainage Schemes would be expedient and economically viable. The implementation of the Schemes began in the late-1940s.

The amendment to the Arterial Drainage Act in 1995 has changed the OPW focus from carrying out large scale catchment wide schemes for agricultural purposes to works on a more localised basis for the protection of property.

The OPW has a statutory duty to maintain the schemes that have been completed in proper repair and effective condition.

Today, the OPW’s annual arterial drainage maintenance works programme provides drainage outfall for 260,000 hectares (650,000 acres) of agricultural lands and comprises 11,500km (7,150 miles) of river channel and approximately 800km (500 miles) of embankments and are providing a level of protection from flooding to urban areas, critical infrastructure, including in excess of 20,000 properties.

This maintenance work is organised on a regional basis, with headquarters in Limerick, Headford, Co. Galway and Trim, Co. Meath.

To view the Arterial Drainage Schemes maintained by OPW click here:


Regular Maintenance Activities- 5 year cycle

The OPW has a statutory duty to maintain the schemes that have been completed under the Arterial Drainage Acts in proper repair and effective condition. Arterial Drainage (AD) maintenance is an ongoing programme of works of a cyclic nature.

Appropriate Assessments (AA) have been conducted in accordance with S.I. No. 477/2011 – European Communities (Birds and Natural Habitats) Regulations 2011, as amended, for all these maintenance works and these assessments are reviewed and updated every five years for each scheme.

Where the works are screened-in for Stage 2 AA, a Natura Impact Statement (NIS) is prepared in accordance with the Regulations. The AA documentation for each AD scheme for the current five year cycle is published on the OPW website.

By looking at the Bonet NIS 2019 to 2023 as referenced in our original correspondence, the AD maintenance for the Bonet catchment is described, the existing environment is described and then the potential impacts are assessed.

The OPW consults with the NPWS prior to making an AA Determination.

Up to this Summer, there was no statutory requirement for public consultation by the OPW prior to making an AA Determination.

In accordance with amendments to the Regulations introduced by S.I. No. 293/2021, the AA for the next 5 year cycle will include public consultation.

Using the Bonet example, the AA on AD maintenance activities for 2024-2028 will be carried out during 2023 and will include public consultation.

Site-specific activities

Additional appropriate assessments are carried out for certain site-specific works within a scheme.

In accordance with the Regulations as amended in 2021, AA Screening Determinations for site-specific activities will be published on the OPW website in advance of works. Where an AA is screened in, a NIS will be prepared and public consultation will be carried out prior to the making of an AA Determination.

The identification of site-specific works requirements is an ongoing activity throughout the year.

Where any site-specific works required in 2022 have already been identified in advance of year-end, these will be referenced in the OPW’s operational AD Maintenance Programme for 2022 outlined below and will be subject to the AA process as outlined.

Documentation on past site-specific assessments has now also been published according to year.

Work Programme

Each year, the OPW prepares an AD maintenance programme for internal operational use that identifies the proposed maintenance activities and locations within each AD scheme catchment area.

This programme is provided to IFI, NPWS and LAWPRO and consultations with these environmental stakeholders continue at regional level to assist OPW with programme delivery.

The annual programme is made available in hard copy at each Regional Office where a member of staff can assist a member of the public with any queries.

The OPW is working to make information from the programme for 2022 available on the OPW website in the form of pdf maps.

In carrying out the programme, the OPW needs to be flexible to address emerging priorities during the year as the scheduling of maintenance is dependent on a several variables such as weather and flood conditions, land use constraints, environmental windows etc.

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