St Nicholas Storm Sewer Overflow
Storm overflow run by United Utilities, discharging into Mill Dam.
Linked bathing water: Wallasey, classified Good for 2025. Named in the company’s return to the Environment Agency. A name opens that bathing water’s official profile, with any pollution warning in the season. The classification is the Environment Agency’s for that bathing season, from all its samples there: it is not a reading of the water today, and it does not say what part this overflow played.
"Not discharging" means the company's monitor reports no discharge right now — not that the water is clean. The feed publishes status only; no discharge volume is measured.
Year by year
The Environment Agency's official annual returns, counted the EA's way (12/24-hour spills). 2026 is our own running count, the same way, from the live feed: our own log of it begins on 28 February, and the discharges before that are Top of the Poops' record of the same feed. The official figure is published next spring.
A spill is the EA's 12/24-hour count: the first 12 hours of a discharge count as one, each further 24 hours with discharge as one more. "Monitor" is the share of that year the monitor was working, so a 0 beside a working monitor is a real zero; "no data" means the monitor produced no usable data that year — not zero. Years before 2024 are matched to this site by name and location, because the EA's site IDs changed that year; a monitor figure beside one of them means the outlet's permit confirms the match.
Twin outlet
United Utilities runs another overflow within 300 m that also discharges into Mill Dam. They share the sewer and the storm, so one outlet's figures are only part of what reaches the water.
This overflow: 7 spills in 2025. Distances are between the published outlet points.
What the 2025 return says
From United Utilities's annual return to the Environment Agency for this overflow.
"High spill threshold not met" means this overflow did not spill often enough to trigger the EA's formal high-spill review for that year. It is not a statement that the spills were harmless.
Discharges we have recorded
58 discharge periods since 2 Jan 2024. 55 of them come from United Utilities's own event-duration-monitoring records (published on Stream, Jan 2024 – Nov 2025); this overflow has no live feed, so nothing after that log is held. The official annual count is the figure to quote.
-
16 min
-
3 min
-
3 min
-
6 min
-
16 min
-
5 min
-
0 min
-
16 min
-
54 min
-
1 min
Show 30 earlier (of 58)
| Started | Ended | Discharge time |
|---|---|---|
| 1 min | ||
| 1 min | ||
| 16 min | ||
| 2 min | ||
| 0 min | ||
| 11 min | ||
| 1 min | ||
| 0 min | ||
| 0 min | ||
| 2 min | ||
| 16 min | ||
| 16 min | ||
| 0 min | ||
| 1 min | ||
| 34 min | ||
| 1 min | ||
| 1 min | ||
| 1 min | ||
| 1 min | ||
| 1 h 10 min | ||
| 1 min | ||
| 29 min | ||
| 1 min | ||
| 1 min | ||
| 1 min | ||
| 1 min | ||
| 17 min | ||
| 4 min | ||
| 41 min | ||
| 10 min |
The year figures above use the EA's 12/24-hour counting method, so they are comparable with the official figures; the monitor log's 84 raw blocks were merged into 58 continuous discharge periods (gaps under 15 min joined).
Rain nearby last 30 days
Nearest live rain gauge: Rainfall gauge nr Over Kellet, 6.0 km away. Brown shading = when this overflow was discharging; ▼ = a discharge start.
Overflow shading is a timing match, not proof of cause — heavy rain and spills share a trigger. Times come from the water company’s event-duration monitor (site status only; no discharge volume is published).
Where it is
Concerned about this overflow?
Report pollution you can see or smell to the regulator straight away; the company handles complaints about the overflow itself.
Write to the MP
The Environment Agency's return places this overflow in the Liverpool Riverside constituency. An MP can ask the company and the regulator questions on a constituent's behalf. These words carry the official figures; change them as you like.
The link opens Parliament's own "Find your MP", which gives the MP's name and how to write to them. FloodRadar sends nothing and keeps nothing you write. Check the constituency against your own address: an MP acts only for people who live in it.
Annual spill figures: Environment Agency Event Duration Monitoring return, © Environment Agency copyright and/or database right, Open Government Licence (OGL) v3.0. Storm-overflow spill events: © the respective water company, published on Stream (data.streamwaterdata.co.uk) under CC BY 4.0. Discharges marked "via Top of the Poops", and this year's figures before 28 February, come from Top of the Poops' record of the same company feed, used under CC BY-SA 4.0: the feed's own start and end times as its pages print them, not their derived hours. Times are shown in UK local time. FloodRadar republishes the monitor's status and the EA's figures; it does not measure discharges itself. Constituency and council area from the EA's return: contains OS data © Crown copyright and database right 2026.