Bascote STW (CSO)
Storm overflow operated by Severn Trent Water. The source names Tributary of River Itchen as the receiving water.
- 12
- Spills in 2025
- 65.8
- Recorded hours
- 99.4%
- Monitor operation
- 6
- Years listed
The reported spill count was 10 higher than in 2024. This compares event counts, not discharge volume.
Checking the latest monitor report…
How it compares in 2025
Bascote STW (CSO) recorded 12 spills in 2025. That is more than 51% of the 14,239 overflows in England with a reported figure, and ranks 6,643rd nationally. Among Severn Trent Water overflows it ranks 963rd of 2,431; the median Severn Trent Water overflow recorded 8 spills. On the Itchen - conf R Stowe to conf R Leam waterbody it ranks 2nd of 3.
| Group | Rank by spills | Median spills | Median hours |
|---|---|---|---|
| This outlet | – | 12 | 65.8 |
| England | 6,643rd of 14,239 | 11 | 22.3 |
| Severn Trent Water | 963rd of 2,431 | 8 | 16.2 |
| Itchen - conf R Stowe to conf R Leam | 2nd of 3 | 12 | 163.8 |
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 | 12 | 65.8 hours | 99.4% | Official data |
| 2024 | 2 | 21.4 hours | 98.9% | Official data |
| 2023 | 14 | 69.9 hours | 95.9% | Official data |
| 2022 | 0 | 0 hours | 100% | Official data |
| 2021 | 0 | 0 hours | 99.1% | Official data |
| 2020 | 47 | 628.3 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
- Inlet storm overflow at a wastewater treatment works
- Permit
- S/12/25831/R
- Activity reference
- A2
- Grid reference
- SP4062063970
- Waterbody ID
- GB109054044110Official 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 “Inlet SO at WwTW”: inlet storm overflow at a wastewater treatment works. The overflow is at the inlet of a treatment works, where wastewater enters the works.
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 1.6 km south-west of the Long Itchington 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.
Open official source ↗Other outlet records nearby
- Long Itchington - Stonebridge Lane (CSO)Current status unknown
Severn Trent Water · River Itchen
- Itchen Bank STW (SSTO)Current status unknown
Severn Trent Water · River Itchen
- Harbury - Deppers Bridge (CSO)Current status unknown
Severn Trent Water · River Itchen
- Harbury - Mill Street (SSO)Current status unknown
Severn Trent Water · Tributary of Radford Brook
Questions about Bascote STW (CSO)
- Who operates Bascote STW (CSO)?
- Severn Trent Water is the operator named in the annual record. The permit reference is S/12/25831/R.
- Where does Bascote STW (CSO) discharge?
- The source names Tributary of River Itchen as the receiving water. This does not show how far a discharge travelled.
- How many times did Bascote STW (CSO) spill in 2025?
- The 2025 return records 12 counted spill events and 65.8 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 99.4% of the reporting period, so the annual figures cover most of the year. They still do not measure discharge volume.
- Is Bascote STW (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 Bascote STW (CSO)?
- The annual return lists the asset type as “Inlet SO at WwTW”, which means inlet storm overflow at a wastewater treatment works. The overflow is at the inlet of a treatment works, where wastewater enters the works.
- How does Bascote STW (CSO) compare with other overflows?
- Bascote STW (CSO) recorded 12 spills in 2025. That is more than 51% of the 14,239 overflows in England with a reported figure, and ranks 6,643rd nationally. Among Severn Trent Water overflows it ranks 963rd of 2,431; the median Severn Trent Water overflow recorded 8 spills. On the Itchen - conf R Stowe to conf R Leam waterbody it ranks 2nd of 3. 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.