Storm overflow register · Severn Trent Water

Ledbury sewage works: storm overflow spills 2025

Ledbury sewage treatment works, run by Severn Trent Water, has 1 monitored storm overflow discharging to River Leadon. In 2025 it recorded 49 spills totalling 104 hours, against 65 spills and 20 hours in 2024. By hours spilling, it ranks 257 of 435 Severn Trent Water works, where 1 spilled longest.

Works size: 12,036 population equivalent (LEDBURY STW, UWWTD 2018). Used for the spill volume estimate.

Every spill in 2025

Each blue mark is one spill, placed by when it started and sized by how long it lasted. Hover over a mark for the date and duration.

JanFebMarAprMayJunJulAugSepOctNovDecLedbury Sewage…3 spills, 1.1 h, 1 Jan to 1 Jan32 spills, 4.9 h, 5 Jan to 6 Jan23 Jan 2025 12:29 GMT, 6 min2 spills, 0.6 h, 24 Jan to 24 Jan23 spills, 3.8 h, 26 Jan to 28 Jan2 spills, 0 h, 15 Feb to 15 Feb2 spills, 1.1 h, 21 Feb to 21 Feb6 spills, 1 h, 23 Feb to 24 Feb15 Apr 2025 18:44 GMT, 1 min12 May 2025 16:43 GMT, 3 min2 spills, 0.6 h, 7 Jun to 7 Jun4 spills, 0.2 h, 29 Jul to 29 Jul31 Jul 2025 14:23 GMT, 3 min2 spills, 0.4 h, 27 Aug to 27 Aug4 Sep 2025 06:05 GMT, 116 min7 Sep 2025 09:14 GMT, 4.5 h4 spills, 1 h, 8 Sep to 8 Sep3 spills, 0.9 h, 10 Sep to 10 Sep7 spills, 1.8 h, 13 Sep to 13 Sep3 spills, 5.2 h, 14 Sep to 14 Sep6 spills, 0.7 h, 3 Oct to 3 Oct2 spills, 0.1 h, 19 Oct to 19 Oct5 spills, 2 h, 22 Oct to 23 Oct1 Nov 2025 17:03 GMT, 1 min6 spills, 3.5 h, 4 Nov to 4 Nov3 spills, 1.2 h, 10 Nov to 10 Nov15 spills, 7.5 h, 11 Nov to 12 Nov15 spills, 24.6 h, 14 Nov to 15 Nov2 spills, 0.1 h, 22 Nov to 22 Nov2 spills, 0.2 h, 29 Nov to 29 Nov8 spills, 4.1 h, 1 Dec to 2 Dec18 spills, 11.5 h, 5 Dec to 6 Dec6 spills, 6.3 h, 9 Dec to 10 Dec2 spills, 1 h, 12 Dec to 12 Dec16 Dec 2025 05:58 GMT, 4 min5 spills, 12.1 h, 17 Dec to 18 Dec

Estimated spill volume by month, 2025

Hours spilling each month × the estimated spill rate for a works of this size. The bars are central estimates and the whiskers show the low-high range. Method.

05,00010k15k20kJan 2025: 10 h spilling ≈ 2,145 m³ (range 854-5,385 m³)JanFeb 2025: 2.1 h spilling ≈ 433 m³ (range 173-1,087 m³)FebMar 2025: 0.0 h spilling ≈ 0.0 m³ (range 0.0-0.0 m³)MarApr 2025: 0.0 h spilling ≈ 0.0 m³ (range 0.0-0.0 m³)AprMay 2025: 0.1 h spilling ≈ 21 m³ (range 8.2-52 m³)MayJun 2025: 0.6 h spilling ≈ 124 m³ (range 49-311 m³)JunJul 2025: 0.2 h spilling ≈ 41 m³ (range 16-104 m³)JulAug 2025: 0.4 h spilling ≈ 82 m³ (range 33-207 m³)AugSep 2025: 15 h spilling ≈ 3,155 m³ (range 1,257-7,922 m³)SepOct 2025: 2.8 h spilling ≈ 577 m³ (range 230-1,450 m³)OctNov 2025: 37 h spilling ≈ 7,672 m³ (range 3,056-19,260 m³)NovDec 2025: 35 h spilling ≈ 7,239 m³ (range 2,883-18,173 m³)Dec
Cubic metres (m³), estimate. Hours are measured by the event duration monitor.

Longest single spills

Started (GMT)OverflowDurationEstimated volume
14 Nov 2025, 08:06Ledbury Sewage Treatment Works23.2 h1,909 - 12,029 m³
18 Dec 2025, 12:31Ledbury Sewage Treatment Works11.1 h909 - 5,730 m³
6 Dec 2025, 04:21Ledbury Sewage Treatment Works5.7 h470 - 2,960 m³
12 Nov 2025, 06:17Ledbury Sewage Treatment Works5.1 h415 - 2,615 m³
14 Sep 2025, 13:54Ledbury Sewage Treatment Works5.0 h412 - 2,597 m³

Estimated 2025 spill volume and pollution

Estimate, not a measurement. Monitors record how long an overflow spills, not how much. This calculator back-calculates a spill rate from the size of the works, using the Environment Agency's permit formulae, and multiplies it by published storm-sewage concentrations. How it works.

Volume, central estimate21,407 m³range 8,527 - 53,742 m³
In litres21.4 millionrange 8.5 million - 53.7 million L
Olympic swimming pools8.6at 2,500 m³ each
Organic load, as people's raw sewage32,110person-days of untreated BOD

Assumed spill rate while spilling: 22.8 - 143.8 L/s (central 57.3 L/s), from a dry-weather flow of 22.8 L/s.

Pollutant releasedLowCentralHighConcentration used (low / typical / high)
BOD₅ (organic load) 341 kg1,927 kg10,748 kg 40 / 90 / 200 mg/L
Low/high: Europe range, Ellis & Jenkins 2005; typical: UK, Ellis & Jenkins 2005 (both via botturi)
Suspended solids 895 kg9,098 kg38,748 kg 105 / 425 / 721 mg/L
Low/high: Europe range; typical: UK, Ellis & Jenkins 2005 (via botturi)
Ammonium-N 16 kg135 kg500 kg 1.9 / 6.3 / 9.3 mg/L
Low: Germany, Brombach 2005; typical/high: Paris range 3.3-9.3 midpoint and top, Gasperi 2012 (via botturi); no UK value found
Total phosphorus 10 kg56 kg290 kg 1.2 / 2.6 / 5.4 mg/L
Low/high: Paris, Gasperi 2012; typical: Slovakia (via botturi). UK figure of 10 mg/L treated as an outlier
E. coli 852.7 billion organisms21.4 trillion organisms537.4 trillion organisms 10,000 / 100,000 / 1.0 million per 100 mL
Median range at CSO and retention-tank outlets, Stott et al. 2018 (via botturi); typical = log midpoint

Low combines the low spill rate with low concentrations, and high combines high with high, so the true figure is very likely inside the range. Long spills become more diluted as they go on, so the central figure tends to overstate the load of long events. The calculator does not estimate the effect on the receiving water, which depends on river flow or tide at the time of the spill.

Ledbury Sewage Treatment Works

Inlet overflow at sewage works · discharges to River Leadon

Spills 2025
49 (104 hours) · down 25% on 2024
Spills 2024
65 (20 hours)
Long-term average
41.2 spills a year (monitored since 2021)
Monitor uptime
100% of the year
High-spill reason (company)
Not asset maintenance - Hydraulic capacity
Investigation
UWWTR investigation completed, Operational investigation completed
Improvement
No improvement action in reporting period
WFD catchment
Leadon - source to conf Preston Bk (GB109054039640)
Outlet location
SO7009237022 (OS grid reference) · View on Apple Maps
EA ID / permit
SVT01337 · S/21/26211/R · company name: LEDBURY STW (CSO)

How the estimate works

  1. Dry-weather flow (DWF) = population × water use per person × (1 + infiltration). Water use is 136.5 L per person per day, England's per-capita consumption for 2024-25 [EA]. Infiltration of groundwater into sewers is taken as 0-40% of that flow [Escritt, via HBF]. The Environment Agency defines DWF as PG + I + E [EA].
  2. Population. The size of each works comes from the load entering it as reported under the Urban Waste Water Treatment Directive, in population equivalents (1 p.e. = 60 g of BOD a day) [UWWTD]. We treat population equivalent as population. That overstates flow where trade effluent adds load, and no official source links the two. Works serving fewer than 2,000 p.e. are not reported, so their size has to be entered by hand.
  3. Low spill rate = DWF. This is the method used by Giakoumis & Voulvoulis (2026), which they note likely underestimates storm loads [G&V].
  4. High spill rate = Formula A − flow to full treatment = (DWF + 1360P) − 3DWF. This is the largest flow the permit expects the storm tanks to handle before it passes on to treatment or overflows [EA]. The central rate is the geometric mean of the low and high rates.
  5. Volume = spill rate × hours spilling, with hours taken from the event duration monitor.
  6. Pollution = volume × published storm-sewage concentrations [Botturi et al.] [US EPA]. Organic load is also shown as person-days of untreated sewage at 60 g of BOD per person per day [UWWTD].

What this cannot tell you. It gives no real flow for any single spill, and no effect on the river or sea, which depends on the flow, tide and the other pressures on the water at the time. It gives no figure for spills from overflows on the sewer network, which serve catchments of unknown size. It is a way to put hours into rough physical terms, not a substitute for flow monitoring.

Sources

  1. EA: Water companies - environmental permits for storm overflows and emergency overflows
  2. EA: Water resources 2024 to 2025 - per capita consumption
  3. HBF: Foul sewer design - historic conventions (citing Escritt 1984 on infiltration)
  4. Giakoumis & Voulvoulis (2026), Environ. Sci.: Water Res. Technol., doi:10.1039/D5EW00860C
  5. Botturi et al. (2021), Crit. Rev. Environ. Sci. Technol. 51:1585 - CSO quality review, Table 2
  6. US EPA (2004) Report to Congress on CSOs and SSOs, chapter 4
  7. Urban Waste Water Treatment Directive, Article 2(6): 1 p.e. = 60 g BOD5/day
  8. Olympic-size swimming pool: 2,500 m³ at the nominal 2 m depth

← All Severn Trent Water works · Contains Environment Agency data licensed under the Open Government Licence v3.0. Spill start and stop times: © Environment Agency copyright and/or database right 2026. All rights reserved. They are water-company data and have not been verified by the Environment Agency. Works size: EEA Waterbase UWWTD. How to read the data.