Shrewsbury, Coton Hill (The Flash) storm overflow
Severn Trent Water · Shrewsbury - Coton Hill (The Flash) (CSO) · SVT00643
This page collects what public records say about one storm overflow: its permit, how often it spilled, and the improvements recorded for it. It is not a water test and does not say whether the water is fit to swim in. A spill count is not a finding that the overflow broke its permit: overflows may spill in heavy rain under their permits, and nothing here can tell whether a spill was allowed.
The record
| Company | Severn Trent Water |
|---|---|
| Environment Agency id | SVT00643 |
| Name in the company's return | SHREWSBURY - COTON HILL (THE FLASH) (CSO) |
| Permit reference | S/02/21023/O, activity A1 (2025 return) |
| Type | SO on sewer network |
| Discharges to | RIVER SEVERN (water body: Severn - conf Bele Bk to conf Sundorne Bk) |
| Bathing water named in the return | River Severn in Shrewsbury |
The permit reference is as the Environment Agency's annual returns give it. The EA's consents register holds the permit itself, but its licence allows internal use only, so its conditions are not published here.
Swim spots downstream
SwimSignal counts this overflow at 2 swim spots. km is along the river network, through any lake on the way. The model weight is SwimSignal's estimate of how much this overflow's spills count at that spot, not a measurement (how it is worked out).
- River Severn in Shrewsbury · 0.9 km upstream · model weight 96% · every overflow there
- River Severn at Ironbridge · 38.4 km upstream · model weight 6% · every overflow there
Spills each year
| Year | Spills | Spill hours | Monitor uptime |
|---|---|---|---|
| 2021 | 36 | 284.47 | 87.97% |
| 2022 | 22 | 21.92 | 73.86% |
| 2023 | 48 | 533.97 | 73.4% |
| 2024 | 18 | 20.03 | 48.66% |
| 2025 | 23 | 6.54 | 99.97% |
From the water company's annual return to the Environment Agency, as published: the spill count as the company returned it, and the hours as the Environment Agency works them out from the return's total duration, to two decimal places. Spills are counted by the Environment Agency's 12/24 method: any discharge in the first 12 hours counts as one spill, then one more for each 24 hours with any discharge. A dash: no return for that year. Monitor uptime is the share of the year the monitor worked; a year with low uptime may undercount.
Recent spills
When this page was updated (31 Oct 2026, 20:24), its company's live feed showed it not discharging. The last spill the feed reported ended on 30 August 2026.
How long its spills lasted, 2024 and 2025. How long this overflow's spills lasted in 2024 and 2025, from the water company's monitor records published by the Environment Agency. A record of the past, not a forecast. It says nothing of how much was discharged.
| Typical spill | 17 min |
|---|---|
| Long end | 1.1 h |
| Longest | 12 h |
| Spills 2024 | 26 |
| Spills 2025 | 32 |
Typical: half its spills were shorter, half longer. Long end: one in ten lasted longer. A spill here is the monitor's events joined when they overlap or start less than an hour apart, so these counts differ from the annual returns' above. More on spill lengths.
Each spill's start and stop times: not listed here. The Environment Agency publishes them for 2024 on, under the Open Government Licence (its start/stop files); this page gives only the summary above.
Improvements recorded
| Return year | Improvement activity | Investigation activity |
|---|---|---|
| 2024 | Operational improvement ongoing | Env Act (SODRP) investigation ongoing, UWWTR investigation completed, Operational investigation completed |
| 2025 | Operational improvement completed | Env Act (SODRP) investigation ongoing, UWWTR investigation completed, Operational investigation completed |
Word for word from the annual returns. The 2023 return left these columns empty. A year's entry covers that year only; work under way may not show until a later return.
The PR24 WINEP lists no storm overflow improvement action on this overflow's permit.
Not published here: Water UK's National Storm Overflows Plan, whose terms forbid reuse without written permission.
Send this record
The button opens your own email app with a short, factual draft about this overflow and a link to this page. Read it, change it as you wish, and add the address yourself: SwimSignal sends nothing and keeps no copy.
Severn Trent Water's own contact details are on its contact page. To send the same record to your MP, find your MP on the UK Parliament website.
The draft
Storm overflow Shrewsbury, Coton Hill (The Flash) storm overflow (SVT00643) Dear Severn Trent Water, I am writing about your storm overflow Shrewsbury, Coton Hill (The Flash) storm overflow (Environment Agency id SVT00643, permit S/02/21023/O). It is upstream of River Severn in Shrewsbury; River Severn at Ironbridge, where people swim. Your annual returns to the Environment Agency record 2024: 18 spills, 20.03 hours; 2025: 23 spills, 6.54 hours. Your 2025 return lists its improvement activity as: "Operational improvement completed". Could you tell me what is planned for this overflow, and when the work is expected to be finished? The public record I am referring to is here: https://swimsignal.co.uk/overflow/SVT00643/ Thank you.
Sources and credits
Storm overflow annual returns, including permit references and improvement and investigation activity: © Environment Agency copyright and/or database right, Open Government Licence v3.0; the figures are the water companies' own returns. PR24 Water Industry National Environment Programme: © Environment Agency copyright and/or database right 2025. All rights reserved. Published under the Open Government Licence. Spill lengths: Environment Agency storm overflow EDM start/stop data 2024 and 2025, Open Government Licence v3.0. Live status: the water companies via the National Storm Overflow Hub, CC BY 4.0. Spots, distances and model weights: SwimSignal, traced on OS Open Rivers (contains OS data © Crown copyright and database right 2026). Sources: annual returns, PR24 WINEP, start/stop data, National Storm Overflow Hub. All credits and licences.