Storm overflow register · Anglian Water

Ingoldmells sewage works: storm overflow spills 2025

Ingoldmells sewage treatment works, run by Anglian Water, has 1 monitored storm overflow discharging to North Sea. In 2025 it recorded 72 spills totalling 160 hours, against 36 spills and 133 hours in 2024. By hours spilling, it ranks 127 of 419 Anglian Water works, where 1 spilled longest.

Works size: 56,329 population equivalent (INGOLDMELLS 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.

JanFebMarAprMayJunJulAugSepOctNovDecIngoldmells WRC11 spills, 2 h, 3 Jan to 4 Jan4 spills, 24 h, 6 Jan to 7 Jan12 Jan 2025 13:34 GMT, 2 min14 Jan 2025 17:16 GMT, 2 min2 spills, 0.4 h, 15 Jan to 16 Jan4 spills, 0.5 h, 17 Jan to 17 Jan19 Jan 2025 09:54 GMT, 10 min21 spills, 4.1 h, 30 Jan to 3 Feb4 spills, 0.5 h, 13 Feb to 14 Feb2 spills, 0.3 h, 17 Feb to 17 Feb2 spills, 0.3 h, 18 Feb to 18 Feb19 Feb 2025 09:56 GMT, 18 min5 spills, 0.6 h, 12 Mar to 13 Mar3 spills, 0.8 h, 14 Mar to 14 Mar9 spills, 2.3 h, 15 Mar to 17 Mar28 Mar 2025 16:38 GMT, 18 min3 spills, 0.3 h, 29 Mar to 29 Mar15 spills, 3.7 h, 15 Apr to 15 Apr3 spills, 0.6 h, 19 Jul to 19 Jul21 Jul 2025 18:30 GMT, 2 min5 spills, 0.3 h, 27 Jul to 28 Jul5 spills, 1.1 h, 1 Aug to 1 Aug2 Aug 2025 07:08 GMT, 2 min2 spills, 0.2 h, 3 Sep to 3 Sep2 spills, 1.2 h, 14 Sep to 14 Sep17 Sep 2025 08:04 GMT, 3 h3 spills, 2.6 h, 3 Oct to 3 Oct6 spills, 6.9 h, 23 Oct to 23 Oct2 spills, 1.1 h, 3 Nov to 3 Nov20 spills, 1 h, 10 Nov to 10 Nov37 spills, 1.6 h, 12 Nov to 12 Nov346 spills, 27.2 h, 14 Nov to 17 Nov126 spills, 7.3 h, 18 Nov to 19 Nov4 spills, 0.3 h, 20 Nov to 20 Nov118 spills, 10.8 h, 22 Nov to 24 Nov26 spills, 1.3 h, 25 Nov to 25 Nov198 spills, 14.4 h, 29 Nov to 2 Dec62 spills, 3.1 h, 4 Dec to 4 Dec57 spills, 3.8 h, 5 Dec to 6 Dec40 spills, 2.2 h, 7 Dec to 7 Dec140 spills, 12.3 h, 9 Dec to 10 Dec12 Dec 2025 17:58 GMT, 2 min63 spills, 4.1 h, 16 Dec to 16 Dec182 spills, 13.2 h, 18 Dec to 19 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.

050k100k150kJan 2025: 29 h spilling ≈ 27,700 m³ (range 11,034-69,543 m³)JanFeb 2025: 3.8 h spilling ≈ 3,668 m³ (range 1,461-9,208 m³)FebMar 2025: 4.2 h spilling ≈ 4,054 m³ (range 1,615-10,177 m³)MarApr 2025: 3.7 h spilling ≈ 3,571 m³ (range 1,422-8,965 m³)AprMay 2025: 0.0 h spilling ≈ 0.0 m³ (range 0.0-0.0 m³)MayJun 2025: 0.0 h spilling ≈ 0.0 m³ (range 0.0-0.0 m³)JunJul 2025: 0.9 h spilling ≈ 869 m³ (range 346-2,181 m³)JulAug 2025: 1.2 h spilling ≈ 1,158 m³ (range 461-2,908 m³)AugSep 2025: 4.4 h spilling ≈ 4,247 m³ (range 1,692-10,662 m³)SepOct 2025: 9.5 h spilling ≈ 9,169 m³ (range 3,652-23,019 m³)OctNov 2025: 62 h spilling ≈ 59,647 m³ (range 23,759-149,747 m³)NovDec 2025: 42 h spilling ≈ 40,344 m³ (range 16,070-101,285 m³)Dec
Cubic metres (m³), estimate. Hours are measured by the event duration monitor.

Longest single spills

Started (GMT)OverflowDurationEstimated volume
6 Jan 2025, 06:40Ingoldmells WRC17.3 h6,664 - 42,000 m³
23 Oct 2025, 06:14Ingoldmells WRC6.3 h2,435 - 15,346 m³
6 Jan 2025, 01:46Ingoldmells WRC4.9 h1,871 - 11,792 m³
15 Nov 2025, 08:44Ingoldmells WRC4.0 h1,538 - 9,692 m³
17 Sep 2025, 08:04Ingoldmells WRC3.0 h1,153 - 7,269 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 estimate154,137 m³range 61,396 - 386,967 m³
In litres154.1 millionrange 61.4 million - 387.0 million L
Olympic swimming pools62at 2,500 m³ each
Organic load, as people's raw sewage231,205person-days of untreated BOD

Assumed spill rate while spilling: 106.8 - 673.1 L/s (central 268.1 L/s), from a dry-weather flow of 106.8 L/s.

Pollutant releasedLowCentralHighConcentration used (low / typical / high)
BOD₅ (organic load) 2,456 kg13,872 kg77,393 kg 40 / 90 / 200 mg/L
Low/high: Europe range, Ellis & Jenkins 2005; typical: UK, Ellis & Jenkins 2005 (both via botturi)
Suspended solids 6,447 kg65,508 kg279,003 kg 105 / 425 / 721 mg/L
Low/high: Europe range; typical: UK, Ellis & Jenkins 2005 (via botturi)
Ammonium-N 117 kg971 kg3,599 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 74 kg401 kg2,090 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 6.1 trillion organisms154.1 trillion organisms3.9 × 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.

Ingoldmells WRC

Inlet overflow at sewage works · discharges to North Sea

Spills 2025
72 (160 hours) · up 100% on 2024
Spills 2024
36 (133 hours)
Long-term average
43.7 spills a year (monitored since 2020)
Monitor uptime
97% of the year
High-spill reason (company)
Performance - Asset configuration (e.g. PS/rising main/storm tanks)
Investigation
Env Act (SODRP) investigation ongoing, Operational investigation completed
Improvement
Operational improvement ongoing
WFD catchment
Lincolnshire (GB640402492000)
Outlet location
TF5971069000 (OS grid reference) · View on Apple Maps
EA ID / permit
AWS00641 · ANNCS13577 · company name: INGOLDMELLS STW

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.