Reservoir owner and operator guidance: inspection information pack

Owners and operators of high risk reservoirs should create and maintain an inspection information pack for their reservoir.

This guidance provides advice on what to include in a reservoir inspection information pack, how to prepare one and how to use it.

You should follow this guidance if you’re an owner or operator of a high risk reservoir in England.

A reservoir is designated as high risk if:

  • it is a large, raised reservoir that has a volume of at least 25,000 cubic metres above ground level
  • an uncontrolled release of water from the reservoir could endanger human life

Owners and operators of high risk reservoirs in England must keep certain records. They must provide these records and other information to engineers so they can do their jobs.

The Environment Agency recommends that owners and operators keep all these records and information together in an inspection information pack. Owners and operators should:

  • prepare the inspection information pack without delay to ensure it is available if an emergency occurs
  • provide the inspection information pack to the inspecting engineer in advance of a planned inspection

Reservoir owners, operators and managers in Wales, Scotland and Northern Ireland are also encouraged to follow this guide.

Records that high risk reservoir owners and operators must keep

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

  • the ‘prescribed form of record (PFR)’ which brings together important information about the characteristics and operation of the reservoir and references other records
  • the on-site emergency flood plan
  • 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

See the Institution of Civil Engineers publication – A Guide to the Reservoirs Act 1975 (second edition) for information about the PFR and other records owners and operators must keep.

What to include in the inspection information pack

Reservoir owners and operators 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
  • in any other way, helps the supervising and inspecting engineers to understand the characteristics, history, and performance of the reservoir structures

This information may be in a range of different formats such as paper records and digital files. Arrange the information with the most up-to-date and recent information first.

There may be other things, specific to your reservoir that you should include.

Types of information to include

Design information

Include information about the design of the reservoir structures which:

  • 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

This information should include all available:

  • plans, elevations and sections of important structures and features
  • hydraulic, structural, geotechnical and other design calculations
  • reports relating to the dam, its associated structures and the surrounding area

Panel engineer reports

Include previous panel engineer documents such as the construction, supervising, and inspecting engineer’s reports and certificates

Survey data

Include any survey reports, data and other information about the reservoir structures over its whole operating life. These may include but are not limited to:

  • visual inspection survey records
  • structural and condition surveys
  • topographical and bathymetric surveys
  • geological surveys
  • geophysical surveys
  • environmental and ecological surveys
  • utility, services and drainage surveys
  • tree surveys
  • CCTV surveys
  • drone surveys
  • aerial photography
  • archaeological surveys
  • mine working enquiries or surveys
  • unexploded ordnance (UXO) surveys

Previous studies and investigations

These may include but are not limited to:

  • draw-down tests and assessments
  • condition assessments
  • geotechnical investigations
  • seepage investigations
  • stability assessments
  • laboratory testing of materials
  • flood risk assessments
  • spillway capacity assessments
  • hydraulic modelling
  • condition assessments of pipework, valves and gates


Photographs provide an important record of changes to the condition of the dam and its associated structures over time. Photographs are particularly important where access:

  • for close visual inspection is only possible when the water level in the reservoir is substantially lowered or empty
  • is not possible during a routine inspection for some other reason

It may not be practicable or possible to source and collate all of the photographs available. If producing a new photographic record for the reservoir an effective record would aim to:

  • show the structures over time and during different times of year
  • show the upstream face of the dam at different water elevations
  • include images of areas of damage, deterioration or other matters of concern such as cracking, slumping, wet spots and vegetation problems
  • include images of sub-surface investigations, such as trial pits and their locations
  • document remedial and improvement works (if not included in reports)
  • show the structures under unusual operational conditions, for example, during very cold or windy weather, flood events or during a reservoir drain-down


Make and keep videos of the reservoir structures operating during normal and unusual conditions.

Monitoring data and reports on their interpretation

Continuous monitoring of the dam and its associated structures is very important. The minimum scope and frequency of monitoring is defined by the inspecting or construction engineer and documented in the PFR. With appropriate analysis and interpretation, monitoring data can give advance warning of potential problems such as seepage or deformation.

Include all monitoring data and their analysis and interpretation reports. These might typically include:

  • reservoir water levels
  • monitoring of piezometric pressure within an embankment dam or within a dam foundation
  • deformation or settlement
  • seepage flow rates

Reports should include routine analysis and interpretation of:

  • assessment of trends and apparent anomalies
  • any gaps in critical data
  • known monitoring system failures

Records of maintenance work

Include any documents and records associated with routine and statutory maintenance. Such documents might include:

  • testing of valves
  • scour releases
  • gate and valve maintenance activities
  • trash clearance from screens
  • grass cutting and other vegetation clearance
  • road repairs
  • drainage works
  • flood damage repairs
  • animal damage repairs
  • structural repairs, for example, re-pointing, joint sealing
  • any unusual repairs, for example, the infilling of a sink hole on the dam crest
  • works related to buried services on or near reservoir structures

Incident reports

Include all incident reports and associated investigation reports for the entire operating life of the reservoir. This includes all incidents reported to the Environment Agency and those considered not serious enough to report.

Historical and superseded documents

Include historical documents that have been superseded. For example, design drawings which have been superseded by drawings of improvement works, and flood studies which have been updated to reflect current methodology. Mark superseded documents as such.

Other important information

Include any other information that is available that may be useful to the supervising or inspecting engineer when carrying out an inspection. For example, useful observations since the last inspection from:

  • local stakeholders, such as recreational organisations
  • users of the reservoir, such as walkers

Information requested by the inspecting engineer

The inspecting engineer may request other information to carry out an inspection. Owners and operators must provide this information and should include it in the inspection information pack.

Identifying missing information

Owners and operators should seek help from the supervising engineer to prepare the pack, and to identify gaps in the information. Check historical inspection reports as they may highlight information that is missing. Search other documents for the missing information.

Supervising engineers and inspecting engineers should use their professional judgement to identify gaps in the inspection information pack. They should advise the reservoir owner and operator what actions to take to add missing information. This is particularly important where gaps in information may have historically led to assumptions which, over time, may have become the accepted truth.

Maintaining the inspection information pack

The condition of the dam and its associated structures will change over time.

Owners and operators should maintain the inspection information pack by:

  • reviewing and updating it regularly to reflect changes
  • adding new information when it becomes available
  • storing it in a secure place

Storing the pack

The supervising engineer and those responsible for the operation of the reservoir should be able to access the inspection information pack at all times. Owners and operators should also consider how to access critical information quickly during an emergency.

The owner and operator should consider making a digital information pack. Old paper drawings, photographs and other physical records may deteriorate over time. Converting them to a digital format would create a permanent record for the future. Use high quality settings to ensure information is not lost or distorted. Keep the original documents safe.

Published 6 July 2021