Why it keeps happening
Three things we can measure in the data. None of them proves a cause on its own, but each points at a different kind of infrastructure problem.
A discharge in dry weather is not an exceptional circumstance, so it is not permitted on any reading of regulation 4.
See the 25 →A strong signal, not a finding. We cannot see whether flow is transferred to another works for treatment, and the permitted figure is not always published.
See the 4 →Rainfall across the catchment does not explain a discharge that an overflow's own treatment works did not share.
See the 31 →Where the indicators concentrate
| Overflow | Hours | Dry | What it points to | Verdict |
|---|---|---|---|---|
| Dartington Sch TwoCSO | 506 | 49 | Dry spilling | On record |
| Scorriton STWSO | 1,833 | 154 | High spill frequency | No action |
| Rattery STWSO | 1,712 | 1775 | High spill frequency | On record |
| Kilbury STW, BuckfastleighSSO | 1,397 | 260 | High spill frequency | On record |
| Smith St, DartmouthCSO | 148 | 21 | High spill frequency | On record |
| Ferry Boat pumping station, DittishamPS-CSO/EO | 79 | 37 | High spill frequency | On record |
| Harbertonford STWSSO | 2,494 | 78 | Very long spills | On record |
| Harberton STWSSO | 1,656 | 67 | Very long spills | On record |
| Broadhempston STWSSO | 1,039 | 56 | Very long spills | On record |
| Cornworthy STW, DartmouthSSO | 999 | 32 | Very long spills | On record |
Hours are the last full year; dry spills are since 2020. Verdict is whether a measure is linked to the overflow — see the gaps.
What this analysis cannot see
These indicators are measured from spill timing and rainfall alone. They cannot see misconnections, the quality of effluent from a works that is running normally, flow transferred between works for treatment, a company's maintenance history, or the periods when a monitor was offline. Because a quiet monitor records nothing, every count here is a floor, not a total.