Storm overflow register · Anglian Water

Immingham sewage works: storm overflow spills 2025

Immingham sewage treatment works, run by Anglian Water, has 1 monitored storm overflow discharging to The River Humber. In 2025 it recorded 75 spills totalling 332 hours, against 82 spills and 368 hours in 2024. By hours spilling, it ranks 67 of 419 Anglian Water works, where 1 spilled longest.

Works size: 14,760 population equivalent (IMMINGHAM 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.

JanFebMarAprMayJunJulAugSepOctNovDecImmingham Water…24 spills, 2.1 h, 1 Jan to 1 Jan73 spills, 60.9 h, 5 Jan to 7 Jan65 spills, 4.1 h, 20 Jan to 21 Jan16 spills, 0.8 h, 23 Jan to 23 Jan16 spills, 1 h, 24 Jan to 24 Jan69 spills, 8.4 h, 27 Jan to 28 Jan7 spills, 2.2 h, 20 Feb to 20 Feb23 Feb 2025 09:50 GMT, 2 min2 Apr 2025 19:48 GMT, 12 min8 spills, 4.1 h, 15 Apr to 15 Apr8 spills, 0.6 h, 21 Apr to 21 Apr3 spills, 0.3 h, 7 May to 7 May5 spills, 1.1 h, 24 May to 24 May2 spills, 0.8 h, 29 May to 29 May4 spills, 1.5 h, 5 Jun to 5 Jun7 spills, 0.5 h, 9 Jun to 10 Jun5 spills, 2.1 h, 6 Jul to 6 Jul10 spills, 1.8 h, 19 Jul to 19 Jul9 spills, 5.4 h, 20 Jul to 20 Jul4 spills, 1.1 h, 22 Jul to 22 Jul10 spills, 1 h, 23 Jul to 23 Jul4 spills, 1 h, 27 Aug to 27 Aug2 spills, 1 h, 29 Aug to 29 Aug4 spills, 0.1 h, 30 Aug to 31 Aug2 spills, 1.4 h, 3 Sep to 3 Sep11 spills, 4.1 h, 4 Sep to 4 Sep5 spills, 1.3 h, 12 Sep to 12 Sep4 spills, 0.9 h, 17 Sep to 17 Sep19 spills, 10.7 h, 20 Sep to 21 Sep10 spills, 2.6 h, 28 Sep to 28 Sep12 spills, 4.3 h, 3 Oct to 3 Oct20 Oct 2025 09:56 GMT, 14 min19 spills, 5.3 h, 23 Oct to 23 Oct10 spills, 1.2 h, 4 Nov to 4 Nov127 spills, 22.2 h, 10 Nov to 12 Nov35 spills, 41.4 h, 14 Nov to 16 Nov35 spills, 4.2 h, 18 Nov to 19 Nov15 spills, 0.9 h, 20 Nov to 20 Nov47 spills, 6 h, 23 Nov to 24 Nov25 Nov 2025 10:46 GMT, 4 min122 spills, 53.3 h, 28 Nov to 2 Dec107 spills, 22.8 h, 4 Dec to 6 Dec7 Dec 2025 19:44 GMT, 2 min42 spills, 14.7 h, 9 Dec to 9 Dec39 spills, 16.1 h, 16 Dec to 17 Dec75 spills, 15.9 h, 18 Dec to 20 Dec2 spills, 0.2 h, 30 Dec to 30 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.

020k40k60k80kJan 2025: 77 h spilling ≈ 19,524 m³ (range 7,777-49,016 m³)JanFeb 2025: 2.2 h spilling ≈ 556 m³ (range 222-1,397 m³)FebMar 2025: 0.0 h spilling ≈ 0.0 m³ (range 0.0-0.0 m³)MarApr 2025: 4.9 h spilling ≈ 1,239 m³ (range 494-3,111 m³)AprMay 2025: 2.2 h spilling ≈ 556 m³ (range 222-1,397 m³)MayJun 2025: 2.0 h spilling ≈ 506 m³ (range 201-1,270 m³)JunJul 2025: 11 h spilling ≈ 2,883 m³ (range 1,148-7,238 m³)JulAug 2025: 2.1 h spilling ≈ 531 m³ (range 212-1,333 m³)AugSep 2025: 21 h spilling ≈ 5,336 m³ (range 2,126-13,397 m³)SepOct 2025: 9.8 h spilling ≈ 2,478 m³ (range 987-6,222 m³)OctNov 2025: 113 h spilling ≈ 28,654 m³ (range 11,414-71,937 m³)NovDec 2025: 86 h spilling ≈ 21,674 m³ (range 8,633-54,413 m³)Dec
Cubic metres (m³), estimate. Hours are measured by the event duration monitor.

Longest single spills

Started (GMT)OverflowDurationEstimated volume
6 Jan 2025, 00:00Immingham Water Recycling Centre1.0 days2,418 - 15,238 m³
15 Nov 2025, 00:00Immingham Water Recycling Centre19.9 h2,001 - 12,614 m³
29 Nov 2025, 05:58Immingham Water Recycling Centre18.0 h1,817 - 11,450 m³
5 Jan 2025, 06:34Immingham Water Recycling Centre17.4 h1,756 - 11,069 m³
14 Nov 2025, 07:18Immingham Water Recycling Centre16.7 h1,682 - 10,603 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 estimate83,964 m³range 33,445 - 210,795 m³
In litres84.0 millionrange 33.4 million - 210.8 million L
Olympic swimming pools34at 2,500 m³ each
Organic load, as people's raw sewage125,946person-days of untreated BOD

Assumed spill rate while spilling: 28.0 - 176.4 L/s (central 70.3 L/s), from a dry-weather flow of 28.0 L/s.

Pollutant releasedLowCentralHighConcentration used (low / typical / high)
BOD₅ (organic load) 1,338 kg7,557 kg42,159 kg 40 / 90 / 200 mg/L
Low/high: Europe range, Ellis & Jenkins 2005; typical: UK, Ellis & Jenkins 2005 (both via botturi)
Suspended solids 3,512 kg35,685 kg151,984 kg 105 / 425 / 721 mg/L
Low/high: Europe range; typical: UK, Ellis & Jenkins 2005 (via botturi)
Ammonium-N 64 kg529 kg1,960 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 40 kg218 kg1,138 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 3.3 trillion organisms84.0 trillion organisms2.1 × 10¹⁵ 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.

Immingham Water Recycling Centre

Inlet overflow at sewage works · discharges to The River Humber

Spills 2025
75 (332 hours) · down 9% on 2024
Spills 2024
82 (368 hours)
Long-term average
96.8 spills a year (monitored since 2020)
Monitor uptime
100% of the year
High-spill reason (company)
Performance - Pump failure / issue
Investigation
Env Act (SODRP) investigation ongoing, Operational investigation ongoing
Improvement
Env Act (SODRP) improvement ongoing, Operational improvement ongoing
WFD catchment
HUMBER LOWER (GB530402609201)
Outlet location
TA2141015600 (OS grid reference) · View on Apple Maps
EA ID / permit
AWS00636 · ANNTS13654 · company name: Immingham Water Recycling Centre

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 Anglian 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.