The Environment Agency has published updated guidance for owners and operators of large reservoirs, including information on reservoir safety, how to register a reservoir, appoint a panel engineer, produce a flood plan, report an incident, together with a new requirement to prepare an inspection information pack.

There are different requirements for:

• large raised reservoirs
• reservoirs that hold less than 25,000 cubic metres of water above ground level

All large raised reservoirs must be registered with the Environment Agency – however, there is no requirement to register a reservoir with a capacity of under 25,000 cubic metres.

There are also extra requirements for reservoirs that the Environment Agency decides are high risk where an uncontrolled release of water could put people’s lives at risk.

Topics covered under the guidance includes:

Build or modify a reservoir

You must tell the Environment Agency if you intend to build, bring back into use or alter a large raised reservoir.

Check also if you need planning permission or an environmental permit. Whether you need one or both depends on the type of reservoir and its intended location.

Register a reservoir

Whether you need to register your reservoir or not, you must follow Health and Safety Executive regulations and local council building regulations.

When to appoint a panel engineer

You must appoint a qualified civil engineer for any large raised reservoir - known as a panel engineer. There are 3 types of panel engineer:

• construction engineer
• supervising engineer
• inspecting engineer

Reservoir safety

The Environment Agency provides the following information about research on reservoir safety held on the British Dam Society’s website: 

• post-incident reporting system for UK dams February 2007
• engineering guide to emergency planning for UK reservoirs June 2006
• interim guide to quantitative risk assessment for UK reservoirs May 2006
• floods and reservoir safety (FEH/FSR) - revised guidance for panel engineers June 2004
• early detection of internal erosion - feasibility report November 2003
• vulnerability of UK dam embankments to increased direct rainfall on their surfaces January 2003
• climate change impacts on the safety of British reservoirs January 2002
• sedimentation in storage reservoirs February 2001

Prepare a reservoir flood plan and flood map

It is a legal requirement for all undertakers to prepare an on-site emergency flood plan for all large raised reservoirs in England.

Report an incident

You may be held responsible for any damage or injury caused due to a sudden uncontrolled release of water. Examples of incidents are:

• dam overtopping
• a leak
• slope instability
• cracks in the dam
• instrumentation readings that show abnormal movement in the dam
• material failure
• pollution

New requirement for owners and operators to prepare an inspection information pack

The updated guidance also includes a new requirement for reservoir owners and operators for the creation and maintenance of an inspection information pack for their reservoir(s). This is the first of the new guidance recommended in the Toddbrook Reservoir Incident Independent Review (Part A). The Review followed the collapse in 2019 of a dam wall holding backing water in Toddbrook Reservoir which threatened to flood the town of Whaley Bridge in Derbyshire.

Owners and operators of high risk reservoirs in England will now also be required to prepare an inspection information pack which should:

• contain all relevant and available information for the reservoir
• be provided to the inspecting engineer in advance of a planned inspection
• be easy to access during an emergency
• be accessible to the supervising engineer at all times

The Environment Agency is recommending that owners and operators should prepare the inspection information pack without delay to ensure it is available if an emergency occurs, and to provide the inspection information pack to the inspecting engineer in advance of a planned inspection.

Documents that owners and operators of high risk reservoirs must keep include:

• construction drawings and other design documents
• the reports, certificates, annexes and directions of engineers and referees
• health and safety files for any construction, alteration or maintenance works covered by the Construction (Design and Management) Regulations 2015

The guidance also recommends that the inspection pack should include all the information they are legally required to keep and any other information that:

• helps someone understand how the reservoir was originally designed and constructed
• provides information about historical remedial and improvement works including surveys, investigations and studies
• highlights any actual or apparent problems relating to the operation and maintenance of the reservoir structures including incident reports and investigations
• shows the risk posed by the reservoir such as dam breach modelling and reservoir inundation modelling
• documents events that are important to the safety of the reservoir such as severe flood events, problems of dam water tightness or stability and acts of vandalism
• documents unusual operational problems such as obstructions to site access, spillway blockages, or hydromechanical components not working
• shows how the dam and associated structures were originally constructed
• details any modifications (improvements and major repairs) that have been made
• depicts the current as-built arrangement and situation
• plans, elevations and sections of important structures and features
• hydraulic, structural, geotechnical and other design calculations

The guidance also suggests that the pack should include any documents and records associated with routine and statutory maintenance, for example:

• testing of valves
• scour releases
• gate and valve maintenance activities
• trash clearance from screens
• drainage works
• flood damage repairs
• animal damage repairs
• structural repairs, for example, re-pointing, joint sealing

The Environment Agency also recommend that all incident reports and associated investigation reports for the entire operating life of the reservoir - both all incidents reported to the Environment Agency and those considered not serious enough to report – should form part of the inspection pack.

Reservoir owners, operators and managers in Wales, Scotland and Northern Ireland are also being encouraged to follow the guidance.

In February 2015, Defra announced that it had no plans to make further changes to the reservoir safety regulatory regime.

Click here to access the guidance on preparing an Inspection Pack