Water supply asset discharges: consents, permits and risk assessments

This guide is for water companies who operate water supply assets.assets in England. This includes reservoirs, wells and boreholes.

YouBefore must get a consent or an environmental permit from the Environment Agency before you make certain discharges from your water supply assetassets to surface waters.

Beforewaters, you applymust forget a either:

• consent or– permitunder yousection need166 toof carry out a risk assessment. This assessment will identify the potentialWater risksIndustry beforeAct you1991
• an makeenvironmental a discharge so you can manage them effectively.
  permit

When you need a consent or a permit

You must consider each type of discharge you may make from your water supply asset andto decide whetherif you need a consent or permita for the discharge.permit.

ConsentsConsent

WaterYou companiesmust whohave operateconsent waterunder supplysection assets166 canof applythe for a Water Industry Act 1991 section 166 consent from the Environment Agency.Agency for discharges:

Water

• that companymay operatorscontain solids or polluting matter
• of drawdown releases through the scour valve
• through pipes that are larger than 229mm diameter

You do not need consent for qualifying discharges from a pipe that is 229mm diameter or less. However,But operatorsyou must take all steps to make sure the discharge is as free from pollutants as is reasonably practicable.

Permits

WaterSome companydischarges operatorsdo mustnot havequalify consent from the Environment Agency for discharges:

• thatconsent mayunder contain solids or polluting matter
• of drawdown releases through the scourWater valve
• throughIndustry pipesAct that1991. are larger than 229mm diameter

Permits

You must have ana environmental permit from the Environment Agency for allthese discharges from water supply assets that may contain solids, accumulated deposits or other pollutants.discharges.

You do not normally need a permit for discharges that are:

• uncontaminated surface waters
• a water transfer and the discharge iswill nonnot pollutingpollute
• made in an emergency to avoid danger to human health – but you must take all reasonably practicable steps to minimise pollution and you must tell the Environment Agency as soon as reasonably practicable

Before you apply for a consent or a permit

WhenYou you apply for a consent or permit to make a discharge from a water supply asset, you need to:

• carryassess out a risk assessment of the potential environmental and safety risks of your proposed discharge
• develop a management system – a written set of procedures that identify and minimise the risks of pollution

CarryHow outto aassess riskthe assessmentrisks

YouYour must carry out a risk assessment forwill allbe waterpart supplyof assetthe dischargestechnical information that requiresupports ayour consent or permit.permit Yourapplication.

The riskdetail assessmentyou willneed beto partprovide depends on:

• the type of water supply asset
• the technicalvolume informationand thatduration supportsof yourthe application.

  Readdischarge

• the sensitivity of the riskreceiving assessmentwater
• the overviewpotential for guidancewater onquality howimpacts

For higher-risk discharges, you’ll need to complete a riskmore assessment.

Youstructured shouldsupporting reviewrisk your assessment. regularlyFor andexample updatefor it if circumstances change.discharges:

If

• from yourlarge assessmentstorage showsreservoirs
• that theare dischargehigh‑volume, mayprolonged representor ainto significantsensitive risk,waters

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The Environment Agency will consider whether youryou managementhave system has properly assessed the risks. TheYou Environment Agency will only giveget you a consent or a permit if you have mitigated the risks as far as is reasonably practicable.

Increase in downstream flow

You must assess whether your water supply asset discharge will haveaffect an impact on the downstream flow.

A large increase in downstream water flow can have serious environmental impacts and safety risks, including flooding.

An increase in downstream flow can:

• damage property, bridges, boats and bankside structures
• affect land use, for example block access tracks
• risk the life and health of humanspeople and animals
• change the river’s appearance, for example erode the river bank
• damage the river ecology, for example wash away aquatic plants
• destroy fish habitats and breeding sites
• displace fish downstream

To reduce the impact you must control the:

• rate of your discharge
• volume of your discharge
• increase in the depth of the channel downstream

You must carry out routine drawdown operations to prevent or minimise downstream impacts and flood risks, as far as is practicable.

Your risk assessment must identify any properties or situations that your routine discharge operations may affect.impact. For example example:

• houses, businesses, caravan andsites camp sites, and campsites
• local water users like anglers, boaters and canoeists. canoeists

You should maintain a contact register and give warning before drawdown operations.

Discharge of sediment

You must consider if the discharge from your water supply asset will impact on sediments downstream. Significant deposits of sediments can:

• damage the river ecology
• destroy fish habitats and breeding sites
• change the river’s appearance

Consider thesurveying need for a survey to find out how much sediment has accumulated that could be washed through the scour valve. Include details of sediment levels in relation to the scour valve height and sediment sampling,sampling as part of your consent or permit application.

Your discharge is more of a risk if:

• you have not opened the scour valve for over one year
• there has been an event that could have created large amounts of sediment, for example a flood upstream of thea water supply assetreservoir

If a large quantity of sediment may wash through the scour valve, you must develop a plan to prevent a damaging discharge.

To reduce the impact, consider the following mitigation measures:

• coincide the discharge with higher natural river flows and increased natural sediment transport
• open the scour valve gradually
• make frequent small discharges
• install and maintain sediment traps to remove trapped sediment

Discharge of polluted sediment

You must consider if pollutants may be present in significant amounts in your water supply asset discharge sediment.

IfDischarge the sediment containscontaining pollutants these may be carried into the downstream river and can:

• cause deterioration in river quality – for water users and abstractors
• damage the river ecology – in the short or long term

IfYou yourmust sedimentschemically maytest containthe pollutantssediment youif mustit chemicallymay testcontain the sediment.pollutants.

To reduce the impact, consider dredging the polluted sediment from the water supply asset.asset’s discharge. You must follow the requirements for disposing of business waste to make sure you dispose of the dredged sediment safely.safely.

Discharge of poor quality water

You must check whether your reservoirwater supply asset discharge is subject to thermal stratification. Thermal stratification is where there are changes in temperature and dissolved oxygen at different depths of the reservoir.depths.

Discharges of stratified water can lower the levels of dissolved oxygen and increase levels of iron and manganese. This can:

• cause deterioration in river quality – for water users and abstractors
• kill fish and other aquatic animals

For stratified reservoirs, your risk assessment must include profiling for:

• dissolved oxygen
• temperature

The Environment Agency is unlikely to allow a discharge if profiling shows the dissolved oxygen is below 50% saturation in the bottom profile of the reservoir.

If your profiling shows less than 80% dissolved oxygen, you should monitor the downstream watercourse during the discharge. Your risk assessment should set a downstream trigger limit for dissolved oxygen. If dissolved oxygen levels drop below this limit, stop the discharge and notify the Environment Agency.Agency.

Algal blooms in reservoirs can cause poor quality discharge water. You should not make planned discharges if there is a significant algal bloom, unless you have shown that the bloom does not affect the discharge quality.

ReleaseImpact ofon fish

Discharges of water can displace fish from thea reservoir into the downstream river.

You must consider the impact on fish if you plan a substantial drawdown. This includes drawdown to a permanently lower water level and also to temporary lower water levels for maintenance before you refill.

You should contact the Environment Agency and ask to speak to your local fisheries team. You may need to rescue the fish so you can relocate them elsewhere or restock them after you’ve refilled the reservoir.

Apply for consent

Apply for consent under section 166 of the Water Industry Act 1991 using the online form. You will need:need to provide:

• details about the discharge and its location
• your site plan
• yourinformation completedon riskthe assessmentrisks and proposedhow mitigationyou measureswill mitigate them

Start now

Apply for a permit

If you cannot get consent

Check to discharge under section 166 of the Water Industry Act 1991, check how to apply for a bespoke permit for the discharge instead.