Construction of Basements and Basement Impact Assessment (BIA)

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Basements can affect the environment and nearby structures in a number of ways. The impacts of such development on the geological, hydrological and hydrogeological environment are of concern to Dublin City Council and the occupants / owners of neighbouring properties.  While small, isolated basements may have little impact, the cumulative effect of incremental development of basements in close proximity, particularly when these are large, potentially creates a significant impact.

The objective of this policy is to present a methodology where the impact of basement development proposals and underground construction on the surrounding ground and groundwater is assessed on a site-specific basis, with any impacts mitigated where necessary. This policy is set out in the BIA Basement Development Policy Document - Version 1.1 . The related BIA Basement Development Guidance Document - Version 1.1  offers guidance to complete a risk-based impact assessment. The required assessment shall be known as a “Basement Impact Assessment” (BIA). Where the proposed development includes the construction of any form of basement, any planning application submitted on or after 3rd February 2020 shall include a Basement Impact Assessment (BIA) as part of the planning application

The principal concerns from a Planning Authority perspective include (but are not limited to);

  • Groundwater
  • Cumulative effects of adjacent basement construction
  • Land stability, ground movement and impact on adjacent properties
  • Surface water flow and flooding
  • Construction Activity and Temporary works e.g. ground anchors
  • Other related factors

A “Basement Impact Assessment” (BIA) is to follow the format typically undertaken to complete an Environmental Impact Assessment process comprising of the following stages;

  • Scoping
  • Ongoing Site Investigation, study and monitoring
  • Continuous scoping
  • Impact assessment and development of mitigation measures
  • Review and decision making (by the Planning Authority)

The BIA process is to be Developer led. Each stage of the process requires Developers to look at the characteristic of the project, the existing site and the potential impacts on the surrounding environment. DCC may obtain the services of an independent expert to undertake a technical evaluation of the submission, as necessary.

Temporary Works Designs and Ground Anchor Licences;

Planning applicants should note that, for all applications lodged on or after 7th October 2019, they will be required to submit a temporary works design to DCC, prior to the commencement of construction. This temporary works design shall clearly indicate whether ground anchors that extend outside of the site (red-line area) form part of that design.

Applicants are advised that, if such ground anchors form part of the design and extend into the public domain, a Ground Anchor Installation Licence (GAIL) must be applied for and received prior to the commencement of any works related to or reliant on such ground anchors Ground Anchor Application form and Checklist. Guidance notes to assist applicants are also available Ground Anchor Installation Guidance Notes.

It should also be noted that if ground anchors extend outside the red-line and into areas other than the private realm the applicant shall also need to submit to the planning authority a written letter from the relevant landowner expressing consent for ground anchors to be placed within their property.