Environmental guidance for your business in Northern Ireland & Scotland
You must not discharge or allow water contaminated with silt to enter a watercourse or drain as it can cause pollution.
Channel run-off away from watercourses and surface water drains when dewatering a site.
Protect all surface water drains and watercourses with cut-off ditches or earth bunds. These should be at least 10 metres from the watercourse.
In Scotland, GBR 10 details the rules relating to discharging water from a surface water drainage system.
From 01 January 2018, GBR 10 has been updated to cover surface water discharge from:
If your site exceeds these thresholds then you will require authorisation from SEPA, see SEPA : Construction site licences..
GBR 10 specifies that all reasonable steps must be taken to ensure pollution does not occur.
The discharge must not:
All parts of the surface water drainage system must be maintained in good working order and repair and steps must be taken to ensure that matter liable to block or obstruct the drainage system is prevented from entering.
Construction specific rules:
Sites operated after 1 April 2007 must be drained to a Sustainable Urban Drainage System (SUDS) unless the discharge is from a single dwelling or to coastal waters.
All parts of the construction site which began operations on or after 01 June 2018, on which works are to be undertaken or any vehicles are to be operated or parked on, must be drained by a surface water drainage system with the capacity to accommodate the maximum volume of run-off expected to occur from the land during the period of construction.
Do not strip soil up to the edges of any watercourse, stream or drainage ditch because loose soil can be washed into the watercourse. This can silt-up the riverbed and harm wildlife. You can be liable for causing pollution even if the pollution was only caused by your indirect actions.
When you plan your works, think about where surface water will run once the vegetation is cleared.
Identify any watercourses, surface and foul drains, or field drains in or next to your site that your work may affect.
Existing field drains can provide a route for the discharge of polluted water to watercourses. It is essential that you know where they are and do not allow polluted run-off to enter them. This is particularly important where you choose to discharge silty water over the ground.
Plan ahead to manage silt run-off so that it does not pollute watercourses or ruin any Sustainable Urban Drainage Systems (SUDS) designed for the completed phase.
Guidance for Pollution Prevention (GPP) 5 contains guidance on measures you can take to avoid causing pollution during building and engineering work.
Produce a method statement to address how the amount of silty water you produce will be minimised and how you will stop it directly or indirectly entering watercourses or drains.
Your method statement should consider the phasing of the works. Large areas of cleared vegetation will increase the risk of run-off causing pollution.
Strip vegetation and topsoil in sequence, clearing only the areas where you need to work.
Minimise the amount of exposed ground and stockpiles of soil on your site. This will reduce the amount of silty water that you have to deal with.
Phase your works to ensure that mud from vehicles or roads or surface water run-off from areas under construction do not enter surface water drainage of areas already completed.
If the completed phase has Sustainable Drainage Systems (SUDS), include details of how these will be protected during the construction phase in your method statements.
If the site is on a slope, consider whether the up-slope works can be completed first to prevent silty water running down-slope into completed works and drainage.
For projects that require open trenches, plan your work so that the length of trench needed at any one time is kept to a minimum. Open trenches will produce silty water.
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