How many fish died as a result of draining clypse reservoir?

Summary

The request sought information on fish mortality and replacement costs due to the draining of Clypse Reservoir. The authority disclosed a risk assessment detailing mitigation strategies to relocate fish rather than kill them, but did not provide specific mortality counts or financial costs.

Key Facts

• Fish stocking was paused in early July 2025 to allow fish to relocate.
• Slow water release was implemented to enable fish to leave via conduits to Kerrowdhoo.
• Stranded fish were to be relocated by DEFA to Kerrowdhoo.
• The reservoir water level was reduced at a rate of less than 300mm per day.
• The risk assessment identified 'Fish killed' as a potential hazard with a high initial risk score of 25.

Data Disclosed

• 06.08.2025
• early July
• <300mm a day
• 25
• 5
• 1
• 12
• 6
• 3
• 9

Original Request

I am looking at finding out how the draining of clypse reservoir has impacted the wildlife and mainly the fish living in the body of water.I would like this information to be made available. Also i want to know if they have been replaced and at what cost to the tax payers.

Data Tables (20)

Full Response Text

Page 1 of 6

Risk Assessment Title: Draining Clypse IR in advance of valve replacement Dept: Water Document No: IR_ Risk Assessment Undertaken by: K. Woakes Date: 06.08.2025 Risk Asst Revision 001 Sheet No: 1 of 6 Reviewed by:
Date:
Activity Definition Hazard Identification Potential Risk Assessment Risk Mitigation Residual Risk Assessment Residual Risk Act No. Activity Description Description of Hazard (consider the themes in grey below) Consequence – Potential risk to environment Severity S (1-5) Likelihood L (1-5) Potential Risk Rp = S x L (1-25) Elimination / Control measures Severity S (1-5) Likelihood L (1-5) Potential Risk Rp = S x L (1-25) High Medium Low

Wildlife - Enhancement or detriment to wildlife sites or species (birds, bats, ASSIs, fish, orchids, trees etc.) Loss or damage to species, habitats

1 Lowering water level Reduced body of water; Empty reservoir; Reduced oxygen concentration; Fish killed 5 5 25 Slow water release from the reservoir allows the fish to leave the reservoir via any of two conduits and relocate to Kerrowdhoo; fish stocking paused early July; reservoir monitored daily – any stranded fish will be relocated by DEFA to Kerrowdhoo Reservoir; 5 1 5 Low 2 Lowering water level Disturbed habitat and feeding grounds for birds such as seagulls; cormorants, mallards, herons Limited food supply; 3 4 12 The rate at which the reservoir water level will reduce is slow <300mm a day; birds can move to nearby Kerrowdhoo IR or other bodies of water; 3 1 3 Low

Page 2 of 6

nesting/ hatching season is over; 3 Lowering water level Disturbed habitat and feeding grounds for amphibians Limited food supply; limited nesting; 3 4 12 Nearby body of water such as residuum pond upstream of reservoir that can be used by animals; regular walk overs to check on any stranded animals – those will be important when the reservoir level drops significantly; 3 2 6 Medium 4 Lowering water level Water plants Drier habitat than normal 3 4 12 No typical water plants within the reservoir; only vegetation on the banks may be affected; Vegetation on banks is used to receding water level as the water level fluctuates during the year; wet autumnal weather will help throughout the year; 3 1 3 Low

Waste – e.g. generation and disposal e.g. Land resource lost to disposal sites, potential ground, water and air pollution. consumption of materials and energy

4

N/A

5

6

Page 3 of 6

Air – e.g. F gases, particulates, sulphur dioxide, CO2 etc. E.g. from equipment leaks, emissions from transport, equipment e.g. Ozone depletion, climate change, smog, air pollution, acid rain

7 N/A

8

9

Land – e.g. Leaks and spills of pollutants (oils, chemicals etc.) from vehicles, storage of materials, bulk storage tanks etc Soil contamination, ecosystem damage, potential groundwater pollution.

10 Lowering water level Reservoir banks may slide; ground subsidence Disturb habitat for fauna and flora 3 3 9 The rate at which the reservoir water level will reduce is very slow <300mm a day; This is to avoid any ground subsidence;
3 1 3 Low 11

12

Noise/ vibrations - Creation of noise, vibration, light, odour pollution etc. e.g. heavy vehicle traffic, extended operating hours Disturbance of wildlife/ local residences

13

N/A

Page 4 of 6

14

Resource use - Use of non-renewable resource, e.g. metals, oils, plastics, chemicals, water Depletion of natural resources, habitat damage/ loss (also potential waste and energy issues)

15

N/A

16

Energy - Burning of fossil fuels, e.g. from, equipment use. Release of air pollutants Depletion of natural resources, Atmospheric emissions- leading to climate change, acid rain, poor air quality

15

N/A

16

Water Contamination

17

18

Page 5 of 6

Guidance to Risk Assessment Scores SEVERITY (S) LIKELIHOOD (L) RISK CATEGORY 1 Negligible Impact
1 Very Unlikely 1 – 5 Low Risk – acceptable 2 Temporary impact
2 Unlikely 6 – 12 Medium Risk – maintain effective control measures to reduce risk 3 Minor Impact
3 Likely 13 -25 High Risk – do not start task – mitigate risk by changing work method 4 Major Impact
4 Very Likely

5 Significant Impact
5 Certain / Imminent

Score Scale of Impact
Location of Impact Interested Parties Affected Description (guide) 1 Negligible Impact Within MU premises and system Manx Utilities Very slight environmental damage Easily resolved Remaining within MU premises and system Likely to be short lived 2 Temporary impact Within MU premises and system Manx Utilities Possible 3rd party Some environmental damage Damage is short term, days or weeks Resolved quickly Remaining within MU premises and system Possible 3rd party involvement 3 Minor Impact Within or outside MU premises and system Manx Utilities 3rd Parties Public Causes pollution or emission harming the environment No long-term damage Consequences contained in time, e.g. a couple of months 3rd party involvement Public involvement might happen

Page 6 of 6

4 Major Impact Outside MU premises or system Manx Utilities 3rd Parties Public News/Press Agencies Causes pollution or emission that harms the environment Enduring long term damage lasting years Hard to mitigate consequences Impact outside of MU premises or system Likely to generate public and press interest
5 Significant Impact Outside MU premises or system Manx Utilities 3rd Parties Public News/Press Agencies Large scale pollution or emission causing extensive change/damage to the environment Large scale impact outside of MU premises or system Requires extensive clean-up or mitigation involving external agencies May have continuing consequences, 50 +years or permanent damage Very likely to generate public/press interest

Detailed Incident Report Reference INC-001059 Org Unit Manx Utilities -> Water Date of Incident 20/10/2025 Incident Type Environment Incident Severity Moderate Reported By Kasia Woakes About The Incident Org Unit Manx Utilities -> Water Reference INC-001059 Date of Incident 20/10/2025 Time of Incident 13:00 (UTC+00:00) Dublin, Edinburgh, Lisbon, London Lost Time (Days) (Actual) 0.00 Location / Area of the Incident Clypse Reservoir Reported By Kasia Woakes What Happened Description of Incident Whilst overpumping the remaining water from the already nearly drained resevoir, several fish were noticed in the water. At that point water was cloudy with all the disturbed sediments causing death to smaller fish. DEFA was informed and requested to attend the site. It should be noted that DEFA was kept informed about the reservoir being drained prior to draining and then throughout. Incident Severity Moderate Near Miss? No Lost Time Accident? No Is the accident reportable under RIDDOR? No Incident Type Environment Who Was Involved Injury Details Was Injury Or Ill Health Sustained? No Was any treatment given? No Environment Incident Details Type of Environmental Incident Incident Action Taken To Control The Situation DEFA's Fisheries team rescued the live larger in size fish and took it off site, presumably to Kerrowdhoo IR. Smaller fish could not have been rescued. Detailed Incident Report 2 Non-conformance Details Wildlife Line Managers Comments Line Managers Comments & Follow Up Discussion Details This task is only completed every 20 years. We have spoken to DEFA and they concur that nothing else could have been done to save the last few fish Has follow up/discussion with person reporting the Incident been completed? Yes Record Approval Approval Stage Approved Approver Gareth Patchett Date 12/11/2025 In the event of an accident, the following procedure is to be adopted: Prior to leaving the accident site, ensure that all parties involved in the accident have provided up to date contact details. Please follow the steps shown and complete the relevant boxes. Formal Investigation Investigation Documents/Checklist Who was the incident reported by? Was first aid offered? Photo's of the scene of the accident If available, please attach CCTV footage Please ensure redacted version is attached and approved by the local security manager Copy of environmental breaches / discharge permits for the date of the incident If applicable please attach relevant documentation Related Risk Assessments Detailed Incident Report 3 This is the Risk Assessment(s) currently in place that are relevant to the incident, if none are available please detail why in the comments Employee Training Records Other document / supporting evidence Investigation Details Lead Investigator What was the person doing when the Accident / Incident occurred? (Identify tools, equipment or material the employee was using). How did the accident / incident occur? (Identify tools, equipment or material the employee was using). What Personal Protective Equipment was used, if applicable? Please tick all that apply, if applicable What health and safety precautions were in place? Brief description of any damage to plant, equipment, vehicle, property (Identify tools, equipment or material the employee was using). ROOT CAUSE - Root Cause tree Contributing Factor - Behaviour Contributing Factor - Tools, Equipment and/or Vehicle Contributing Factor - Permits and Supervision Contributing Factor - Collective and/or personnel protective methods Contributing Factor - The Environment Contributing Factor - Policy / Procedure Contributing Factor - Leadership / Supervision Contributing Factor - Personal Factors Contributing Factor - Competency / Capability / Training Lessons Learnt Detailed Incident Report 4 Description Please summarise your findings from above Impact Please describe the impact Solution Please summerise steps taken to reduce / prevent reoccurrence Potential Improvement What improvements will be achieved Detailed Incident Report 5

Manx Utilities PO Box 177, Douglas Isle of Man, IM99 1PS

e: enquiries@manxutilities.im t: 01624 687687 www.manxutilities.im

Our ref: 5095845 04 December 2025

Dear ###

We write further to your request, received 18 November 2025, which states:

"I am looking at finding out how the draining of clypse reservoir has impacted the wildlife and mainly the fish living in the body of water.I would like this information to be made available.
Also i want to know if they have been replaced and at what cost to the tax payers." While our aim is to provide information whenever possible, in this instance Manx Utilities does not hold or cannot, after taking reasonable steps to do so, find some of the information that you have requested. Some of the information is potentially held by the Department of Environment, Food & Agriculture (DEFA). I have detailed below the information that is held.

I am looking at finding out how the draining of clypse reservoir has impacted the wildlife and mainly the fish living in the body of water.I would like this information to be made available.

Manx Utilities (MU) began detailed planning for the valve replacement at Clypse Impounding Reservoir in June 2025. As part of this process, MU liaised with DEFA Fisheries to ensure the impact on stocked trout in the reservoir was minimised. Draining the reservoir was the only viable option to carry out the essential works and an environmental impact assessment was undertaken to assess the potential impact on wildlife – see attached (Env Risk Assessment Reservoir Drainings).

In early July, DEFA ceased stocking the reservoir with fish. Anglers continued fishing until the end of August when fishing was prohibited due to safety concerns related to the steep and slippery reservoir banks. Following several meetings with DEFA prior to draining, Manx Utilities anticipated that as water levels dropped, the majority of the remaining fish would migrate from Clypse to the adjacent Kerrowdhoo Impounding Reservoir via the interconnecting pipework.

Draining of the reservoir commenced in mid-July, with water being gradually transferred from Clypse to Kerrowdhoo at an average rate of 20 mm per day. Full- scale draining began in mid-August, with rates maintained at approximately 200–300 mm per day, aiming for completion by mid-September. By 15 September, the reservoir had been drained as far as the pipework allowed.

Following this date the reservoir refilled during periods of wet weather and was subsequently drained again. Daily inspections indicated no signs of fish distress during this process, and it was assumed that the fish population had migrated to Kerrowdhoo as expected.

When valve replacement works commenced on 20 October the remaining water had to be pumped out. A small number of distressed fish were observed and DEFA’s Inland Fisheries Division was informed and attended the site. An internal incident was recorded – see attached (Incident 20.10.25).

Also i want to know if they have been replaced and at what cost to the tax payers.

Manx Utilities do not hold information regarding the replacement of fish stocks. DEFA may be able to advise.

Please quote the reference number 5095845 in any future communications.

Your right to request a review

If you are unhappy with this response to your freedom of information request, you may ask us to carry out an internal review of the response, by completing a complaint form and submitting it electronically or by delivery/post.

An electronic version of our complaint form can be found by going to our website at https://services.gov.im/freedom-of-information/Review . If you would like a paper version of our complaint form to be sent to you by post, please contact me and I will be happy to arrange for this. Your review request should explain why you are dissatisfied with this response, and should be made as soon as practicable. We will respond as soon as the review has been concluded.

If you are not satisfied with the result of the review, you then have the right to appeal to the Information Commissioner for a decision on; 1. Whether we have responded to your request for information in accordance with Part 2 of the Freedom of Information Act 2015; or 2. Whether we are justified in refusing to give you t

[Response truncated — full text is 15,705 characters]