Storm overflow register · Severn Trent Water

Huthwaite sewage works: storm overflow spills 2025

Huthwaite sewage treatment works, run by Severn Trent Water, has 2 monitored storm overflows discharging to Nunn Brook. In 2025 they recorded 96 spills totalling 578 hours, against 140 spills and 1,037 hours in 2024. By hours spilling, it ranks 66 of 435 Severn Trent Water works, where 1 spilled longest.

Works size: 6,132 population equivalent (HUTHWAITE 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.

JanFebMarAprMayJunJulAugSepOctNovDecHuthwaite Sewage…1 Jan 2025 06:24 GMT, 16.9 h2 spills, 65.5 h, 5 Jan to 8 Jan7 spills, 22.7 h, 27 Jan to 28 Jan17 Sep 2025 11:51 GMT, 2.6 h3 Oct 2025 20:49 GMT, 2.5 h10 Nov 2025 20:15 GMT, 94 min12 Nov 2025 20:55 GMT, 100 min5 spills, 56.5 h, 14 Nov to 16 Nov3 spills, 20.9 h, 29 Nov to 30 Nov2 spills, 17.6 h, 1 Dec to 2 Dec6 Dec 2025 12:55 GMT, 4.4 h4 spills, 23.9 h, 9 Dec to 10 Dec15 Dec 2025 17:08 GMT, 30.9 h3 spills, 45.8 h, 17 Dec to 19 Dec22 Dec 2025 10:25 GMT, 3.9 hHuthwaite Sewage…2 spills, 1.4 h, 1 Jan to 1 Jan2 spills, 3.1 h, 5 Jan to 6 Jan3 spills, 3.9 h, 27 Jan to 27 Jan10 Feb 2025 20:12 GMT, 2 min8 spills, 1.9 h, 23 Feb to 23 Feb2 spills, 0.2 h, 12 Mar to 12 Mar2 spills, 0.4 h, 13 Mar to 13 Mar4 spills, 2.1 h, 22 Mar to 22 Mar28 Mar 2025 05:30 GMT, 13 min2 spills, 0.6 h, 15 Apr to 16 Apr4 spills, 0.5 h, 21 Apr to 21 Apr4 spills, 1.8 h, 24 May to 24 May25 May 2025 22:40 GMT, 37 min12 spills, 3.3 h, 26 May to 28 May3 spills, 2.1 h, 6 Jul to 7 Jul15 Jul 2025 10:37 GMT, 96 min2 spills, 1.4 h, 19 Jul to 19 Jul2 spills, 1.2 h, 20 Jul to 20 Jul30 Jul 2025 07:16 GMT, 42 min2 spills, 0.9 h, 4 Aug to 4 Aug29 Aug 2025 13:31 GMT, 42 min2 spills, 1.3 h, 30 Aug to 31 Aug3 Sep 2025 14:00 GMT, 71 min2 spills, 2.1 h, 4 Sep to 4 Sep2 spills, 3.6 h, 14 Sep to 14 Sep17 Sep 2025 03:55 GMT, 8 h3 spills, 8.3 h, 20 Sep to 21 Sep28 Sep 2025 02:02 GMT, 40 min6 spills, 5.3 h, 2 Oct to 3 Oct5 spills, 5.5 h, 19 Oct to 20 Oct3 spills, 1.8 h, 22 Oct to 23 Oct2 spills, 0.4 h, 29 Oct to 29 Oct2 spills, 1.4 h, 31 Oct to 31 Oct2 spills, 6.6 h, 4 Nov to 5 Nov7 Nov 2025 14:52 GMT, 37 min7 spills, 15.2 h, 10 Nov to 12 Nov4 spills, 46.9 h, 14 Nov to 16 Nov4 spills, 3.9 h, 18 Nov to 19 Nov22 Nov 2025 06:40 GMT, 13 min3 spills, 6 h, 23 Nov to 23 Nov5 spills, 18.5 h, 28 Nov to 30 Nov3 spills, 9.4 h, 1 Dec to 1 Dec3 spills, 1.5 h, 4 Dec to 4 Dec3 spills, 7.1 h, 5 Dec to 6 Dec2 spills, 1.3 h, 7 Dec to 7 Dec2 spills, 19.4 h, 9 Dec to 9 Dec2 spills, 1 h, 12 Dec to 12 Dec4 spills, 27.9 h, 15 Dec to 16 Dec5 spills, 20.5 h, 17 Dec to 19 Dec21 Dec 2025 20:03 GMT, 6.4 h

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: 114 h spilling ≈ 11,925 m³ (range 4,750-29,939 m³)JanFeb 2025: 1.9 h spilling ≈ 200 m³ (range 80-501 m³)FebMar 2025: 3.0 h spilling ≈ 315 m³ (range 126-791 m³)MarApr 2025: 1.0 h spilling ≈ 105 m³ (range 42-264 m³)AprMay 2025: 5.7 h spilling ≈ 599 m³ (range 239-1,504 m³)MayJun 2025: 0.0 h spilling ≈ 0.0 m³ (range 0.0-0.0 m³)JunJul 2025: 7.1 h spilling ≈ 746 m³ (range 297-1,873 m³)JulAug 2025: 2.9 h spilling ≈ 305 m³ (range 121-765 m³)AugSep 2025: 27 h spilling ≈ 2,784 m³ (range 1,109-6,990 m³)SepOct 2025: 17 h spilling ≈ 1,765 m³ (range 703-4,431 m³)OctNov 2025: 178 h spilling ≈ 18,744 m³ (range 7,466-47,058 m³)NovDec 2025: 221 h spilling ≈ 23,231 m³ (range 9,253-58,321 m³)Dec
Cubic metres (m³), estimate. Hours are measured by the event duration monitor.

Longest single spills

Started (GMT)OverflowDurationEstimated volume
5 Jan 2025, 07:57Huthwaite Sewage Treatment Works2.7 days2,683 - 16,908 m³
14 Nov 2025, 07:45Huthwaite Sewage Treatment Works2.3 days2,326 - 14,662 m³
14 Nov 2025, 03:46Huthwaite Sewage Treatment Works1.8 days1,807 - 11,391 m³
18 Dec 2025, 12:55Huthwaite Sewage Treatment Works1.4 days1,378 - 8,683 m³
15 Dec 2025, 17:08Huthwaite Sewage Treatment Works1.3 days1,295 - 8,160 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 estimate60,729 m³range 24,190 - 152,464 m³
In litres60.7 millionrange 24.2 million - 152.5 million L
Olympic swimming pools24at 2,500 m³ each
Organic load, as people's raw sewage91,094person-days of untreated BOD

Assumed spill rate while spilling: 11.6 - 73.3 L/s (central 29.2 L/s), from a dry-weather flow of 11.6 L/s.

Pollutant releasedLowCentralHighConcentration used (low / typical / high)
BOD₅ (organic load) 968 kg5,466 kg30,493 kg 40 / 90 / 200 mg/L
Low/high: Europe range, Ellis & Jenkins 2005; typical: UK, Ellis & Jenkins 2005 (both via botturi)
Suspended solids 2,540 kg25,810 kg109,926 kg 105 / 425 / 721 mg/L
Low/high: Europe range; typical: UK, Ellis & Jenkins 2005 (via botturi)
Ammonium-N 46 kg383 kg1,418 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 29 kg158 kg823 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 2.4 trillion organisms60.7 trillion organisms1.5 × 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.

Huthwaite Sewage Treatment Works

Storm tank at sewage works · discharges to Nunn Brook

Spills 2025
29 (317 hours) · down 45% on 2024
Spills 2024
53 (635 hours)
Long-term average
56.8 spills a year (monitored since 2021)
Monitor uptime
100% of the year
Investigation
Env Act (SODRP) investigation ongoing, UWWTR investigation ongoing, Operational investigation completed
Improvement
Operational improvement completed
WFD catchment
Alfreton Brook from Source to Westwood Brook (GB104028052350)
Outlet location
SK4682958180 (OS grid reference) · View on Apple Maps
EA ID / permit
SVT01199 · T/41/45831/R · company name: HUTHWAITE STW (SSO)

Huthwaite Sewage Treatment Works

Inlet overflow at sewage works · discharges to Nunn Brook

Spills 2025
67 (261 hours) · down 23% on 2024
Spills 2024
87 (402 hours)
Long-term average
102.2 spills a year (monitored since 2021)
Monitor uptime
100% of the year
High-spill reason (company)
Not asset maintenance - Hydraulic capacity
Investigation
Env Act (SODRP) investigation ongoing, UWWTR investigation ongoing, Operational investigation completed
Improvement
No improvement action in reporting period
WFD catchment
Alfreton Brook from Source to Westwood Brook (GB104028052350)
Outlet location
SK4682958180 (OS grid reference) · View on Apple Maps
EA ID / permit
SVT01198 · T/41/45831/R · company name: HUTHWAITE 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.