Temporary dewatering from excavations to surface water

You usually need an environmental permit if you discharge liquid or waste water into surface water.

Source: Environment Agency 7th February 2018

Liquid or waste water includes:

  • poisonous, noxious or polluting matter
  • waste matter
  • trade effluent
  • sewage effluent
  • contaminated surface water

 

Surface water includes:

  • rivers
  • streams
  • estuaries
  • lakes
  • canals
  • coastal waters

However, you do not currently need to apply for a permit if you:

  • have a short term, temporary discharge of uncontaminated water which is wholly or mainly rainwater, from an excavation to surface water (such as pumping water out of excavations on a building site)
  • comply with all the conditions in this regulatory position statement (RPS)

 

You need to apply for a bespoke permit if:

  • your water discharge is from pumping out contaminated groundwater or water from contaminated land so it can be treated
  • your water discharge is from quarry activities
  • you cannot comply with the conditions in this RPS

Conditions you must comply with

The discharge must:

  • be clean water, for example clear rainwater or infiltrated groundwater which has collected in the bottom of temporary excavations
  • not result in water containing fine or coarse suspended solids (silty water) entering surface water
  • not last more than 3 consecutive months (the activity may stop and restart but the clock does not restart) – if the activity is likely to go over 3 consecutive months then you need to apply for a permit
  • be made to surface water, such as a river, stream or the sea
  • have a method statement that minimises the risk of pollution

The discharge must not:

  • pollute surface water
  • contain any chemical dosing agents, flocculants or coagulants
  • be from a site which is contaminated by oil, metals, hydrocarbons, solvents or pesticides or other polluting substances
  • result in the spread of non-native invasive species, parasites or disease
  • cause flooding from surface water
  • cause erosion of the banks or bed of the receiving watercourse
  • contain concrete wash water even if it has been treated
  • contain site drainage from surface areas such as haul roads, storage or working areas
  • be from a site with naturally elevated concentrations of substances which exceed environmental quality standards

Before starting work on site you must:

  • plan how to minimise the level of contaminants such as silt entering the excavation
  • plan how to dispose of water that enters the excavation
  • plan not to use machinery in excavations while dewatering is taking place
  • minimise water entering the excavation, for example from rainfall, runoff, groundwater ingress or high water table
  • consider using sustainable urban drainage construction methods

The discharge must not be located within, or less than 500 metres upstream of:

  • Sites of Special Scientific Interest
  • Special Areas of Conservation (SACs)
  • Special Protection Areas (SPAs)
  • candidate SACs, possible SACs, potential SPAs and sites of community importance
  • internationally designated Ramsar sites
  • other nature conservation sites, such as ancient woodlands, local and national nature reserves – check the map
  • local wildlife sites – find your local council

Contact the Environment Agency if your discharge rate is more than 10% of the dry weather flow (Q95 low flow) rate of the surface water. A high discharge rate may increase flood risk or have other local environmental consequences.

Enforcement

An RPS means that the Environment Agency will not normally take enforcement action against you provided:

  • your activity meets the description set out in this RPS
  • you comply with the conditions set out in this RPS
  • your activity does not (and is not likely to) cause environmental pollution or harm human health

When to check back

This RPS will be reviewed by 30 April 2020. You’ll need to check back then to see if it still applies or if you need to apply for a permit.