Drainage Assessments in Northern Ireland (NI)

We deliver expert Drainage Assessments in Northern Ireland to ensure your new development is fully protected from flood risks and meets all local planning regulations.

Under current Strategic Planning Policy Statement (SPPS) guidance and Policy FLD 3, a formal Drainage Assessment is mandatory if your project meets any of the following criteria:

• Residential Layouts: Any development comprising 10 or more dwelling units.
• Site Footprint: Any development site exceeding 1 hectare in size.
• Hard Surfacing: New buildings or hard surfaces exceeding 1,000 square meters.
• Flood History: Any location with historical evidence of surface water flooding.
• Agency Flag: Sites where a drainage complaint has been logged with DfI Rivers.

Drawing on over 15 years of combined experience across both the private sector and the Northern Ireland Environment Agency (NIEA), our specialist team at O’Sullivan Environmental secures seamless approvals for developers, architects, and housing associations.

To discuss your site’s needs, contact a member of our Team here.

Our Engineering & Consultative Services

Every civil drainage assessment we undertake is executed by qualified environmental consultants in strict compliance with current NI planning policies. Our services include:
• Detailed site walkovers and visual environmental inspections.
• Comprehensive reviews of site development proposals against local area plans.
• Submission of Schedule 6 agreements under the Drainage (NI) Order 1973.
• Calculation of expected peak rainfall and proposed site surface water runoff.
• Sustainable Drainage Systems (SuDS) designs in line with CIRIA C753 guidance.
• Liaison with DfI Rivers and submission of NI Water Pre-Development Enquiries (PDE).