Combined Sewage Overflow

Summary

The requester asked for the number of untreated sewage discharges from the Lake Road Combined Sewage Overflow in 2021 and how many lasted over three hours. The authority disclosed that data was only available until September 2021 due to a telemetry malfunction, provided historical data for 2017-2020, and clarified that the discharged liquid is screened 'storm sewage' rather than raw human sewage.

Key Facts

• The telemetry system at the Lake Road CSO malfunctioned on 23 September 2021, limiting 2021 data availability.
• Discharged liquid is defined as 'storm sewage' (a diluted mixture of foul sewage and surface water) passed through a 6mm screen.
• Many spills occur during prolonged rainfall and would be counted as single events under UK methodology.
• Raw data was manually interpreted to generate the figures, so accuracy cannot be fully assured.
• The equipment at Lake Road is now fully functional.

Data Disclosed

• 23 September 2021
• 2017
• 2018
• 2019
• 2020
• 01/01/21 – 23/09/21
• 43
• 62
• 51
• 66
• 17
• 35
• 40
• 49
• 15
• 13
• 20
• 10
• 9
• 6
• 6mm
• 10 minute
• 3 hours
• 12/24/24

Original Request

How many times during 2021 did the Combined Sewage Overflow located in Lake Road, Douglas discharge untreated sewage? How many of these discharges lasted more than three hours?

Data Tables (1)

Full Response Text

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

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

Our ref: 2303765 16 March 2022

Dear ###

We write further to your request which was received on 3 March 2022 and which states:

"How many times during 2021 did the Combined Sewage Overflow located in Lake Road, Douglas discharge untreated sewage? How many of these discharges lasted more than three hours?"

Our response to your request is as follows: The telemetry system at the Lake Rd CSO malfunctioned on the 23rd September 2021, so only figures up to that date can be provided for 2021. Therefore, in addition to these figures we can provide the equivalent data for the previous 4 years. Please note that these are spills of greater than 10 minute duration (to avoid including events that were likely false readings). The equipment at Lake Road is now fully functional. Many of these spills are close together, occurring during prolonged rainfall events. In the UK these would be combined and classed as one spill. Period Total Number of Spills Number of spills using UK 12/24/24 counting methodology Spills

3 hours 2017 43 35 13 2018 62 40 20 2019 51 35 10 2020 66 49 9 01/01/21 – 23/09/21 17 15 6 To obtain these figures raw data has been manually interpreted and as such accuracy cannot be assured This liquid is not raw human sewage. It is ‘storm sewage’ - a highly diluted mixture of foul sewage (containing waste from toilets, sinks, showers, dishwashers, washing machines etc.), surface water from both roofs and roads, along with groundwater that infiltrates into the sewers. This storm sewage is passed through a 6mm screen to prevent the discharge of solid matter as per UK best practise.

Please quote the reference number 2303765 in any future communications.

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