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Guidance: Reservoirs: How to manage your large raised reservoir

Environment Agency

July 25
14:00 2024

Introduction

Dams and reservoirs are an important part of our national infrastructure.

If we do not manage them properly, they could cause:

  • serious flooding
  • major damage
  • loss of life

They need monitoring and maintaining to keep them as safe as possible. The Environment Agency want to work with reservoir owners and operators (known as undertakers) to reduce the risk of dams failing.

We have produced this guide to help anyone who manages and operates reservoirs.

It contains advice on:

  • the roles involved in managing reservoirs
  • your role as an undertaker
  • common problems
  • how to spot them
  • how to reduce the risk of these happening

This guide is not a substitute for professional advice. If in doubt, you must consult a qualified civil engineer.

Health and safety

Reservoirs can be dangerous places. You should always consider your health and safety when visiting your reservoir.

Take these steps to reduce the risks:

  • wear appropriate clothing and footwear for the site
  • take extra care not to slip on wet sloping surfaces such as the upstream (where water goes into the reservoir) and downstream (where water leaves the reservoir) faces of the dam
  • wash your hands after touching reservoir water or wet vegetation this prevents leptospirosis, Weils disease and other waterborne diseases
  • wear gloves and use appropriate tools for example, spindle extensions, lever bars and other specialist equipment are available for operating valves
  • do not enter confined spaces such as manhole chambers or tunnels unless you are trained specialist confined spaces safety training is available
  • if visiting a remote reservoir, let people know where you are and when you expect to return
  • take a telephone in case of emergency and check your signal on arrival

Legislation

Overview

The Reservoirs Act 1975 provides the legal framework for ensuring reservoir safety. Reservoir safety means the prevention of flooding from an uncontrolled escape of water (failure). The safe operation and management of reservoirs reduces the risk of dam or reservoir failure. The act covers any large raised reservoir (LRR). This is one where the volume of water held above the surrounding land is 25,000 cubic metres or more. That is approximately 10 Olympic swimming pools.

LRRs are spilt into high risk and not high risk:

High risk reservoirs are those where an uncontrolled release of water from the reservoir could endanger human life. It does not mean that these reservoirs are at high risk of failure.

High risk LRRs must fulfil all the requirements of the act. Not high risk reservoirs must also fulfil specific requirements. Undertakers should be aware that under common law, they may be held responsible for any damage or injury caused by a failure. If an undertaker fails to ensure reservoir safety, they could also face criminal prosecution.

Employers also have a duty for the safety of others under current health and safety legislation.

Roles

Environment Agency

The Environment Agency is the enforcement authority for England. We follow the Regulators Code and are responsible for comprehensive regulation and enforcement of the act.

We are responsible for:

  • maintaining a register of reservoirs and making this available to the public
  • reporting to Defra
  • making sure that undertakers have their high risk reservoirs regularly inspected by inspecting engineers
  • making sure that undertakers appoint a supervising engineer for their high risk reservoirs
  • making sure that undertakers appoint construction engineers to design and build their reservoirs
  • making sure that undertakers carry out maintenance and necessary repairs to high risk reservoirs - an inspecting engineer will have said what is required at each reservoir
  • making sure undertakers report on any incidents
  • making sure that undertakers prepare on-site emergency flood plans for their reservoirs
  • sharing the lessons learnt from incidents with the industry
  • enforcing the act by working with undertakers to make sure they comply and if needed, warning and prosecuting those that do not
  • commissioning engineering services and repairs if undertakers fail to comply - we then recharge our costs to the undertaker
  • acting in an emergency if the undertaker is not available or incapable - we may recharge our costs to the undertaker

We are happy to advise undertakers and engineers on how to manage compliance. You can email us if you have any questions or would like to discuss any concerns relating to your reservoir.

Undertakers

Undertakers are operators or owners of a reservoir. They have ultimate responsibility for its safety.

They can include:

  • water companies
  • navigation authorities
  • the Environment Agency
  • the Ministry of Defence
  • private landowners
  • businesses, including commercial enterprises and farms
  • other reservoir users such as sailing and fishing clubs

Even if a reservoir is not being used, responsibility rests with the owner. Section 4 of this guide gives an overview of the responsibilities an undertaker has.

All panel engineers

Panel engineers are a group of specialist civil engineers known as qualified civil engineers (QCEs). The Secretary of State appoints them. They are specifically experienced in, and are qualified for, reservoir safety.

Panel engineers may be:

  • construction engineers
  • inspecting engineers
  • supervising engineers

The act requires them to oversee the safe construction, operation and maintenance of reservoirs.

The undertaker must appoint a construction engineer when:

  • building a new reservoir
  • existing reservoirs are repaired or changed

Construction engineer

The role of a construction engineer is to supervise the design and construction of a new reservoir. They are also required when modifying an existing reservoir. A construction engineer will be on the All Reservoirs Panel.

Inspecting engineer

Inspecting engineers must inspect high risk reservoirs at least every 10 years or more frequently if needed.

The role of an inspecting engineer is to:

  • inspect a reservoir
  • report their findings
  • make recommendations to improve safety - these could be measures in the interest of safety, or maintenance measures

In their role as a QCE, they supervise and certify that the measures have been acted upon. Inspecting engineers are members of the All Reservoirs Panel.

Supervising engineer

The role of a supervising engineer is to:

  • supervise the operation and maintenance of a reservoir at all times
  • prepare a written statement (a section 12 statement) at least every 12 months that summarises the activities carried out to fulfil the inspecting engineers recommendations - it should also highlight if they are not doing this
  • help the undertaker prepare incident reports and flood plans
  • certify on-site flood plans

You can see a list of supervising engineers on the contact details of engineers on the supervising engineer panel website.

Undertaker requirements

Main responsibilities of an undertaker

As an undertaker, you must do certain activities to make sure your reservoir stays compliant with the act. These activities depend on the risk designation the Environment Agency has given your reservoir.

You will receive a risk designation from the Environment Agency after your reservoir construction is finished and certified.

We follow this process:

  • the Environment Agency gives provisional risk designation - high risk or not high risk
  • there is time for undertaker representation, which gives you the chance to provide further evidence if you disagree with the provisional designation
  • the Environment Agency gives final designation
  • there is time for appeal if your reservoir is designated as high risk
  • the designation takes effec

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