Storm overflow register · United Utilities

Workington sewage works: storm overflow spills 2025

Workington sewage treatment works, run by United Utilities, has 1 monitored storm overflow discharging to Irish Sea. In 2025 it recorded 122 spills totalling 644 hours, against 152 spills and 1,001 hours in 2024. By hours spilling, it ranks 78 of 289 United Utilities works, where 1 spilled longest.

Works size: 52,154 population equivalent (WORKINGTON 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.

JanFebMarAprMayJunJulAugSepOctNovDecWorkington WwTW9 spills, 14 h, 1 Jan to 1 Jan3 Jan 2025 09:55 GMT, 5 min4 spills, 1 h, 4 Jan to 4 Jan19 spills, 22.2 h, 5 Jan to 6 Jan4 spills, 3.4 h, 13 Jan to 13 Jan2 spills, 0.1 h, 15 Jan to 15 Jan2 spills, 1.4 h, 22 Jan to 22 Jan21 spills, 7.9 h, 23 Jan to 26 Jan13 spills, 9.7 h, 27 Jan to 28 Jan7 spills, 3.4 h, 30 Jan to 31 Jan2 Feb 2025 22:29 GMT, 4 min9 spills, 9.6 h, 4 Feb to 4 Feb13 spills, 16.7 h, 20 Feb to 22 Feb20 spills, 19.7 h, 23 Feb to 25 Feb3 spills, 1 h, 26 Feb to 26 Feb5 Mar 2025 13:59 GMT, 1 min8 Mar 2025 18:42 GMT, 2 min18 Mar 2025 15:58 GMT, 2 min4 spills, 0.4 h, 22 Mar to 22 Mar24 Mar 2025 15:43 GMT, 1 min2 spills, 4.2 h, 27 Mar to 28 Mar2 spills, 8 h, 29 Mar to 29 Mar11 spills, 1.3 h, 14 Apr to 14 Apr2 spills, 0.5 h, 18 Apr to 18 Apr9 spills, 2.4 h, 23 May to 24 May24 May 2025 20:55 GMT, 3.3 h27 May 2025 12:12 GMT, 19 min4 spills, 17.4 h, 28 May to 29 May33 spills, 26.9 h, 3 Jun to 5 Jun2 spills, 6.6 h, 6 Jun to 6 Jun7 spills, 13 h, 9 Jun to 10 Jun3 spills, 4.1 h, 12 Jun to 12 Jun7 spills, 24.3 h, 14 Jun to 15 Jun19 Jun 2025 09:42 GMT, 3 min21 spills, 24.9 h, 21 Jun to 24 Jun6 spills, 12.1 h, 26 Jun to 26 Jun27 Jun 2025 09:57 GMT, 101 min7 spills, 4 h, 1 Jul to 2 Jul3 spills, 17.3 h, 3 Jul to 5 Jul2 spills, 1.5 h, 6 Jul to 6 Jul2 spills, 5.9 h, 14 Jul to 14 Jul8 spills, 18.3 h, 15 Jul to 16 Jul5 spills, 3.6 h, 20 Jul to 20 Jul3 spills, 3.8 h, 3 Aug to 3 Aug17 spills, 12.9 h, 4 Aug to 5 Aug4 spills, 0.3 h, 27 Aug to 27 Aug6 spills, 1.5 h, 28 Aug to 28 Aug29 Aug 2025 15:51 GMT, 26 min30 Aug 2025 16:29 GMT, 1 min8 spills, 7.3 h, 1 Sep to 1 Sep19 spills, 21.7 h, 3 Sep to 5 Sep3 spills, 0.9 h, 7 Sep to 7 Sep8 Sep 2025 18:09 GMT, 14 min5 spills, 1.9 h, 10 Sep to 10 Sep3 spills, 2.3 h, 11 Sep to 11 Sep57 spills, 56.8 h, 13 Sep to 17 Sep4 spills, 52.7 h, 19 Sep to 21 Sep3 spills, 2.3 h, 27 Sep to 27 Sep4 spills, 17.4 h, 30 Sep to 1 Oct33 spills, 7.1 h, 3 Oct to 4 Oct19 spills, 1.2 h, 7 Oct to 7 Oct18 Oct 2025 16:29 GMT, 25 min2 spills, 1 h, 21 Oct to 21 Oct26 Oct 2025 14:35 GMT, 35 min2 spills, 1.7 h, 27 Oct to 28 Oct28 Oct 2025 19:41 GMT, 45 min15 spills, 23.6 h, 31 Oct to 2 Nov4 spills, 12.1 h, 3 Nov to 3 Nov26 spills, 18.2 h, 10 Nov to 12 Nov35 spills, 41.5 h, 12 Nov to 15 Nov31 spills, 7.6 h, 18 Nov to 19 Nov37 spills, 32.5 h, 22 Nov to 24 Nov15 spills, 1.5 h, 26 Nov to 27 Nov

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.

0100k200k300k400kJan 2025: 63 h spilling ≈ 56,477 m³ (range 22,496-141,789 m³)JanFeb 2025: 47 h spilling ≈ 42,090 m³ (range 16,765-105,668 m³)FebMar 2025: 13 h spilling ≈ 11,349 m³ (range 4,521-28,492 m³)MarApr 2025: 1.8 h spilling ≈ 1,609 m³ (range 641-4,038 m³)AprMay 2025: 23 h spilling ≈ 20,911 m³ (range 8,329-52,498 m³)MayJun 2025: 114 h spilling ≈ 101,606 m³ (range 40,472-255,085 m³)JunJul 2025: 51 h spilling ≈ 45,128 m³ (range 17,976-113,296 m³)JulAug 2025: 19 h spilling ≈ 16,979 m³ (range 6,763-42,626 m³)AugSep 2025: 146 h spilling ≈ 130,649 m³ (range 52,040-327,998 m³)SepOct 2025: 40 h spilling ≈ 35,477 m³ (range 14,131-89,067 m³)OctNov 2025: 127 h spilling ≈ 113,580 m³ (range 45,241-285,148 m³)NovDec 2025: 0.0 h spilling ≈ 0.0 m³ (range 0.0-0.0 m³)Dec
Cubic metres (m³), estimate. Hours are measured by the event duration monitor.

Longest single spills

Started (GMT)OverflowDurationEstimated volume
19 Sep 2025, 00:56Workington WwTW2.0 days16,819 - 106,005 m³
1 Oct 2025, 02:28Workington WwTW17.2 h6,105 - 38,476 m³
4 Jul 2025, 13:15Workington WwTW16.7 h5,950 - 37,504 m³
14 Jun 2025, 10:05Workington WwTW12.1 h4,313 - 27,184 m³
5 Jan 2025, 17:06Workington WwTW12.1 h4,289 - 27,034 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 estimate575,408 m³range 229,197 - 1.4 million m³
In litres575.4 millionrange 229.2 million - 1.4 billion L
Olympic swimming pools230at 2,500 m³ each
Organic load, as people's raw sewage863,112person-days of untreated BOD

Assumed spill rate while spilling: 98.9 - 623.2 L/s (central 248.2 L/s), from a dry-weather flow of 98.9 L/s.

Pollutant releasedLowCentralHighConcentration used (low / typical / high)
BOD₅ (organic load) 9,168 kg51,787 kg288,917 kg 40 / 90 / 200 mg/L
Low/high: Europe range, Ellis & Jenkins 2005; typical: UK, Ellis & Jenkins 2005 (both via botturi)
Suspended solids 24,066 kg244,548 kg1.0 million kg 105 / 425 / 721 mg/L
Low/high: Europe range; typical: UK, Ellis & Jenkins 2005 (via botturi)
Ammonium-N 435 kg3,625 kg13,435 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 275 kg1,496 kg7,801 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 22.9 trillion organisms575.4 trillion organisms1.4 × 10¹⁶ 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.

Workington WwTW

Inlet overflow at sewage works · discharges to Irish Sea

Spills 2025
122 (644 hours) · down 20% on 2024
Spills 2024
152 (1,001 hours)
Long-term average
143.7 spills a year (monitored since 2021)
Monitor uptime
100% of the year
High-spill reason (company)
Performance - Asset configuration (e.g. PS/rising main/storm tanks)
Investigation
No investigation activity in reporting period
Improvement
No improvement action in reporting period
WFD catchment
Solway Outer South (GB641211630003)
Outlet location
NX9732031880 (OS grid reference) · View on Apple Maps
EA ID / permit
UUP02175 · 017580285 · company name: WORKINGTON WwTW

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 United Utilities 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.