Dittisham Main STW
The monitor is reporting and shows no discharge.
This looks like a fault, not a storm.
This overflow has discharged in dry weather 33 times since 2020 — spills with no rainfall to excuse them. Its treatment works is not itself over capacity, so a catchment-wide explanation does not hold. Applied to this record, the two-stage lawfulness test is hard to pass: a recurring dry-weather discharge is not an exceptional circumstance, and where the remedy is routine maintenance the disproportionate-cost exception is hard to run.
How this verdict is reached →Can its works cope?
Full capacity view →This overflow drains to Dittisham Main STW, serving about 388 people on a 66 m³/day permit.
The works has headroom — so spills here point to another problem, often on that branch of the network (a blockage, a failed pump or infiltration).
On our estimate the works has spare capacity for about ~80 more people before it reaches its permitted flow.
Its permit
What the environmental permit sets for this overflow — and where the public record is silent, which is itself the finding.
- Pass-forward flow
- 66 m³/day (works DWF)
- Spill frequency limit
- None set
- Monitoring tier
- Not published
- Assessment trigger
- Crossed — over 10 spills/year
Is anyone acting on this?
- Install and run event-duration monitoringMonitoringcomplete 2021
- Investigate the cause of the spillsInvestigationcomplete 2022
- Move AMP7 U_INV2 driver output to 2-minute flow monitoring (U_MON4b)Monitoringdue 2026
- MCERTS certification of an AMP7 U_MON3 driver output overflow operation monitor (U_MON3a)Monitoringdue 2026
- Reduction of spills to meet EnvAct_IMP driversImprovementdue 2030
A physical improvement is committed against this overflow.
What you can do about this one
Ask for the data
Under the Environmental Information Regulations, Dittisham Main STW's telemetry, the works' flow-to-full-treatment setting, and any spill investigations are emissions information — they cannot be withheld on commercial-confidentiality grounds. A written request is the fastest lever.
Get it into the next programme
Investigations that will shape the 2030–35 environment programme must complete by this date. Putting this overflow on the record now — to South West Water and the Environment Agency — is what gets it considered.
Put it in the drainage plan
South West Water's draft Drainage & Wastewater Management Plan goes to a twelve-week consultation. A named overflow with evidence behind it is far harder to leave out.
The record since 2020
33 dry spills and 0 pre-STW spills since 2020. Pick a year to see its events below.
2025: 46 spills · 159 discharge events
Counted spills — the EA's 12/24-hour block method, the basis of the 10-a-year cap. Published annual return where available, computed the same way for the current year. Two ways to count →
Dry spills, every year
33 dry spills since 2020 · showing up to 12
Spilled before its works
0 events since 2020 · started while Dittisham Main STW stayed shut
This overflow has never been recorded spilling ahead of its treatment works.
Spills by month, 2025
Dry Wet weatherEvery spill in 2025, most recent first
Each event checked against the nearest rain gauge and against the treatment works’ own overflow. Open any row for its evidence dossier.
Showing the last 80 events of 159 in 2025.
Excluded from the counts, classification and flags above — too short to weigh against rainfall, and often an operational blip rather than a genuine discharge. Listed here for completeness. How we know.