Mapperley - Marshall Rd/Hallam Rd (CSO)
Storm overflow operated by Severn Trent Water. The source names Ouse Dyke as the receiving water.
- 46
- Spills in 2025
- 69
- Recorded hours
- 100%
- Monitor operation
- 2
- Years listed
The reported spill count was the same as in 2024. This compares event counts, not discharge volume.
Checking the latest monitor report…
How it compares in 2025
Mapperley - Marshall Rd/Hallam Rd (CSO) recorded 46 spills in 2025. That is more than 86% of the 14,239 overflows in England with a reported figure, and ranks 1,911th nationally. Among Severn Trent Water overflows it ranks 175th of 2,431; the median Severn Trent Water overflow recorded 8 spills. On the Ouse Dyke Catchment (trib of Trent) waterbody it ranks 2nd of 12.
| Group | Rank by spills | Median spills | Median hours |
|---|---|---|---|
| This outlet | – | 46 | 69 |
| England | 1,911th of 14,239 | 11 | 22.3 |
| Severn Trent Water | 175th of 2,431 | 8 | 16.2 |
| Ouse Dyke Catchment (trib of Trent) | 2nd of 12 | 26.5 | 40.3 |
Rank 1 has the most spills. Equal counts share a rank. Only overflows with a reported count are ranked. Counts do not measure volume, so a higher rank does not mean more sewage.
Annual spill history
| Year | Spills | Duration | Monitor operation | Source |
|---|---|---|---|---|
| 2025 | 46 | 69 hours | 100% | Official data |
| 2024 | 46 | 73.3 hours | 100% | Official data |
A missing figure means the source did not provide a usable value. A zero is shown as zero. Monitor operation below 90% can make comparison less reliable.
Outlet details
- Water company
- Severn Trent Water
- Outlet type
- Storm overflow on the sewer network
- Permit
- Unpermitted
- Activity reference
- Unknown
- Grid reference
- SK5940542401
- Waterbody ID
- GB104028053260Official waterbody record ↗
- Location source
- Official annual grid reference
- Location precision
- About 1 metres
- Location note
- Unknown
About the name and type
The annual return lists this asset as “SO on sewer network”: storm overflow on the sewer network. The return places this overflow on the sewer network.
The waterbody link opens the Environment Agency record for the exact ID in the return. It is a source lookup; we do not import its classification.
Where it is
The recorded position is about 2.6 km west of the Carlton (Gedling) reference point in the ONS built-up areas data.
Area and water pages
Check the official record
Public access to this outlet is unknown. Do not enter restricted land or use this page as a route guide.
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Questions about Mapperley - Marshall Rd/Hallam Rd (CSO)
- Who operates Mapperley - Marshall Rd/Hallam Rd (CSO)?
- Severn Trent Water is the operator named in the annual record. The permit reference is Unpermitted.
- Where does Mapperley - Marshall Rd/Hallam Rd (CSO) discharge?
- The source names Ouse Dyke as the receiving water. This does not show how far a discharge travelled.
- How many times did Mapperley - Marshall Rd/Hallam Rd (CSO) spill in 2025?
- The 2025 return records 46 counted spill events and 69 hours of recorded discharge. Spills are counted with the 12/24-hour method, so this is not a count of every start signal.
- Can I trust the 2025 figures for this outlet?
- The monitor worked for 100% of the reporting period, so the annual figures cover most of the year. They still do not measure discharge volume.
- Is Mapperley - Marshall Rd/Hallam Rd (CSO) discharging right now?
- This record is linked to a company live feed. The panel above shows the latest report we hold, with its date. That report can be old, and the monitor can be offline, so check the date before relying on it. A report that no discharge is taking place is not a water-quality result.
- How accurate is the map marker?
- The marker comes from the grid reference in the official annual return, which is accurate to about 1 metres. It shows the recorded outlet position, not the extent of any discharge.
- What kind of outlet is Mapperley - Marshall Rd/Hallam Rd (CSO)?
- The annual return lists the asset type as “SO on sewer network”, which means storm overflow on the sewer network. The return places this overflow on the sewer network.
- How does Mapperley - Marshall Rd/Hallam Rd (CSO) compare with other overflows?
- Mapperley - Marshall Rd/Hallam Rd (CSO) recorded 46 spills in 2025. That is more than 86% of the 14,239 overflows in England with a reported figure, and ranks 1,911th nationally. Among Severn Trent Water overflows it ranks 175th of 2,431; the median Severn Trent Water overflow recorded 8 spills. On the Ouse Dyke Catchment (trib of Trent) waterbody it ranks 2nd of 12. Ranks compare counted spill events only. They do not compare volume or harm.
- Does zero spills mean the water was safe?
- No. A zero means the annual return recorded zero counted spill events for this outlet and year. It is not a water-quality test, and pollution can come from other sources.