Storm overflow register · Anglian Water

Jaywick sewage works: storm overflow spills 2025

Jaywick sewage treatment works, run by Anglian Water, has 1 monitored storm overflow discharging to The North Sea. In 2025 it recorded 52 spills totalling 186 hours, against 86 spills and 504 hours in 2024. By hours spilling, it ranks 115 of 419 Anglian Water works, where 1 spilled longest.

Works size: 27,184 population equivalent (JAYWICK 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.

JanFebMarAprMayJunJulAugSepOctNovDecJaywick Water…1 Jan 2025 13:34 GMT, 5.4 h8 spills, 25 h, 5 Jan to 6 Jan3 spills, 0.5 h, 8 Jan to 8 Jan2 spills, 4 h, 23 Jan to 23 Jan5 spills, 0.8 h, 31 Jan to 31 Jan2 spills, 0.5 h, 4 Feb to 4 Feb12 spills, 13.3 h, 9 Feb to 11 Feb3 spills, 3.4 h, 22 Feb to 22 Feb3 spills, 6.2 h, 24 Feb to 24 Feb26 Feb 2025 14:04 GMT, 2.7 h2 spills, 5.6 h, 15 Apr to 15 Apr21 Apr 2025 19:08 GMT, 2.1 h24 May 2025 06:22 GMT, 2.1 h2 spills, 1 h, 27 May to 27 May7 Jun 2025 18:40 GMT, 2.6 h2 spills, 2.9 h, 13 Jun to 14 Jun2 spills, 6.7 h, 6 Jul to 6 Jul3 spills, 7.6 h, 19 Jul to 19 Jul2 spills, 6.1 h, 20 Jul to 21 Jul24 Jul 2025 12:56 GMT, 2.1 h3 Aug 2025 18:58 GMT, 118 min3 spills, 4.7 h, 3 Sep to 3 Sep2 spills, 0.9 h, 4 Sep to 4 Sep2 spills, 0.9 h, 10 Sep to 10 Sep3 spills, 1 h, 13 Sep to 13 Sep2 spills, 2.1 h, 14 Sep to 14 Sep4 spills, 0.8 h, 17 Sep to 17 Sep4 spills, 5 h, 3 Oct to 4 Oct2 spills, 6.9 h, 20 Oct to 20 Oct2 spills, 1.6 h, 21 Oct to 21 Oct7 spills, 12.8 h, 22 Oct to 23 Oct9 spills, 9.4 h, 29 Oct to 30 Oct1 Nov 2025 05:32 GMT, 3.1 h2 Nov 2025 09:12 GMT, 3.3 h3 spills, 1.1 h, 10 Nov to 10 Nov19 spills, 11.2 h, 13 Nov to 14 Nov19 Nov 2025 10:32 GMT, 104 min2 spills, 5.8 h, 22 Nov to 23 Nov7 Dec 2025 14:42 GMT, 10 min3 spills, 3.7 h, 9 Dec to 9 Dec6 spills, 6.9 h, 18 Dec to 18 Dec28 Dec 2025 17:30 GMT, 6 min29 Dec 2025 19:58 GMT, 14 min

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.

020k40k60kJan 2025: 36 h spilling ≈ 16,628 m³ (range 6,623-41,746 m³)JanFeb 2025: 26 h spilling ≈ 12,203 m³ (range 4,861-30,637 m³)FebMar 2025: 0.0 h spilling ≈ 0.0 m³ (range 0.0-0.0 m³)MarApr 2025: 7.7 h spilling ≈ 3,587 m³ (range 1,429-9,004 m³)AprMay 2025: 3.2 h spilling ≈ 1,491 m³ (range 594-3,742 m³)MayJun 2025: 5.5 h spilling ≈ 2,562 m³ (range 1,020-6,432 m³)JunJul 2025: 22 h spilling ≈ 10,434 m³ (range 4,156-26,194 m³)JulAug 2025: 2.0 h spilling ≈ 932 m³ (range 371-2,339 m³)AugSep 2025: 10 h spilling ≈ 4,844 m³ (range 1,930-12,161 m³)SepOct 2025: 36 h spilling ≈ 16,582 m³ (range 6,605-41,629 m³)OctNov 2025: 26 h spilling ≈ 12,250 m³ (range 4,879-30,754 m³)NovDec 2025: 11 h spilling ≈ 5,124 m³ (range 2,041-12,863 m³)Dec
Cubic metres (m³), estimate. Hours are measured by the event duration monitor.

Longest single spills

Started (GMT)OverflowDurationEstimated volume
5 Jan 2025, 01:10Jaywick Water Recycling Centre17.0 h3,154 - 19,879 m³
10 Feb 2025, 16:10Jaywick Water Recycling Centre7.8 h1,453 - 9,160 m³
29 Oct 2025, 13:12Jaywick Water Recycling Centre7.8 h1,447 - 9,121 m³
21 Jul 2025, 05:58Jaywick Water Recycling Centre5.8 h1,082 - 6,821 m³
1 Jan 2025, 13:34Jaywick Water Recycling Centre5.4 h1,008 - 6,354 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 estimate86,636 m³range 34,509 - 217,502 m³
In litres86.6 millionrange 34.5 million - 217.5 million L
Olympic swimming pools35at 2,500 m³ each
Organic load, as people's raw sewage129,953person-days of untreated BOD

Assumed spill rate while spilling: 51.5 - 324.8 L/s (central 129.4 L/s), from a dry-weather flow of 51.5 L/s.

Pollutant releasedLowCentralHighConcentration used (low / typical / high)
BOD₅ (organic load) 1,380 kg7,797 kg43,500 kg 40 / 90 / 200 mg/L
Low/high: Europe range, Ellis & Jenkins 2005; typical: UK, Ellis & Jenkins 2005 (both via botturi)
Suspended solids 3,623 kg36,820 kg156,819 kg 105 / 425 / 721 mg/L
Low/high: Europe range; typical: UK, Ellis & Jenkins 2005 (via botturi)
Ammonium-N 66 kg546 kg2,023 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 41 kg225 kg1,175 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 3.5 trillion organisms86.6 trillion organisms2.2 × 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.

Jaywick Water Recycling Centre

Inlet overflow at sewage works · discharges to The North Sea

Spills 2025
52 (186 hours) · down 40% on 2024
Spills 2024
86 (504 hours)
Long-term average
74.2 spills a year (monitored since 2020)
Monitor uptime
100% of the year
High-spill reason (company)
Not asset maintenance - Hydraulic capacity
Investigation
Env Act (SODRP) investigation ongoing
Improvement
Env Act (SODRP) improvement ongoing
WFD catchment
Essex (GB650503520001)
Outlet location
TM1374012190 (OS grid reference) · View on Apple Maps
EA ID / permit
AWS00664 · AEECS12400 · company name: JAYWICK NEW 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.