Civil Engineering

A civil engineer designs everything the building sits on and connects to: the roads and access, the drainage that takes rain off the site, the foul system that takes waste away, and the water supply that feeds it. On a planning application that work is what shows the site can actually be serviced, and it is assessed by the local authority alongside the architecture.

If the site sits in or beside Flood Zone A or B you will need one, and many local authorities now ask for an assessment on any site near a watercourse. It is staged: a screening exercise first, and a fuller assessment only where the screening finds a risk worth quantifying. The point of it is to show the development is safe over its lifetime, climate change included.

Sustainable Drainage Systems hold rain on the site and release it slowly, instead of piping it straight to the nearest sewer or stream. Local authorities ask for it because the receiving network usually has no capacity left, and because slowing runoff also filters it. In practice it means attenuation, permeable surfaces and swales sized against the storms the site has to take.

It is the percolation test behind a one-off house: trial holes and water table checks that show treated effluent can safely soak away on the site. It is carried out to the EPA Code of Practice for domestic waste water treatment systems, which sets the test depths and the minimum number of holes. It has to be done by a suitably qualified site assessor or engineer, since local authorities do not accept results from anyone else.

It is a check that the vehicles a development will actually receive can get in, turn and get out again. The path each vehicle sweeps is modelled against the road, the entrance and the yard, using the design vehicle the standards require. Planners ask for it wherever refuse trucks, fire appliances or deliveries have to reach a site, which in practice is most schemes above a single house.

For any new or altered connection to a public water or waste water network, yes. The application has to show the proposed pipework and the loads it will place on the network, and the connection is then agreed on terms Uisce Éireann, formerly Irish Water, sets. On larger schemes there is a handover stage as well, where the infrastructure is taken over for ongoing maintenance.

By answering the question the planner actually asked, with drawings and calculations rather than assurances. Most drainage requests come down to three things: where the water goes, what happens in a storm bigger than the design one, and who maintains what. A response that addresses those with figures is the difference between a decision and another round of correspondence.

Because a combined system sends clean rainwater to a treatment plant that has no reason to treat it, and in heavy rain it sends the mixture somewhere neither belongs. Separation is required on new development, and it has to be demonstrated on the drawings, with the two systems kept apart the whole way to their outfalls.