Storm overflow register · Severn Trent Water

Tickhill sewage works: storm overflow spills 2025

Tickhill sewage treatment works, run by Severn Trent Water, has 2 monitored storm overflows discharging to Slutwell Stream. In 2025 they recorded 91 spills totalling 323 hours, against 94 spills and 336 hours in 2024. By hours spilling, it ranks 124 of 435 Severn Trent Water works, where 1 spilled longest.

Works size: 5,170 population equivalent (TICKHILL 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.

JanFebMarAprMayJunJulAugSepOctNovDecTickhill Sewage…39 spills, 4.9 h, 1 Jan to 1 Jan173 spills, 94.2 h, 5 Jan to 14 Jan4 spills, 0.1 h, 15 Jan to 15 Jan11 spills, 0.4 h, 18 Jan to 18 Jan38 spills, 1.5 h, 19 Jan to 21 Jan25 spills, 1.8 h, 23 Jan to 25 Jan140 spills, 22.2 h, 26 Jan to 31 Jan9 spills, 0.4 h, 1 Feb to 1 Feb4 spills, 0.2 h, 2 Feb to 2 Feb3 spills, 0.2 h, 10 Feb to 10 Feb8 spills, 0.7 h, 15 Feb to 15 Feb5 spills, 0.4 h, 20 Feb to 20 Feb8 spills, 0.5 h, 23 Feb to 24 Feb5 spills, 0.3 h, 26 Feb to 26 Feb4 spills, 0.1 h, 22 Mar to 22 Mar24 May 2025 01:21 GMT, 106 min30 May 2025 09:10 GMT, 10 min4 spills, 1.4 h, 6 Jul to 6 Jul2 spills, 1.1 h, 19 Jul to 19 Jul4 spills, 1.5 h, 20 Jul to 20 Jul3 Sep 2025 15:26 GMT, 22 min14 Sep 2025 20:26 GMT, 21 min5 spills, 1.7 h, 17 Sep to 17 Sep2 spills, 11.2 h, 20 Sep to 21 Sep28 Sep 2025 03:26 GMT, 39 min2 spills, 0.9 h, 3 Oct to 3 Oct3 spills, 0.7 h, 19 Oct to 19 Oct6 spills, 1.7 h, 23 Oct to 23 Oct7 Nov 2025 18:21 GMT, 30 min2 spills, 2.2 h, 10 Nov to 10 Nov12 spills, 46.5 h, 14 Nov to 16 Nov5 spills, 2.3 h, 18 Nov to 19 Nov9 spills, 2.7 h, 23 Nov to 23 Nov10 spills, 19 h, 28 Nov to 30 Nov2 spills, 1.7 h, 1 Dec to 1 Dec35 spills, 38.1 h, 4 Dec to 10 Dec12 Dec 2025 12:06 GMT, 47 min13 spills, 10.7 h, 15 Dec to 16 Dec16 spills, 19.5 h, 17 Dec to 20 Dec5 spills, 5.6 h, 21 Dec to 22 Dec2 spills, 0.5 h, 24 Dec to 24 DecTickhill Sewage…1 Jan 2025 06:41 GMT, 7 min2 spills, 8.3 h, 5 Jan to 6 Jan27 Jan 2025 02:43 GMT, 63 min10 Sep 2025 19:45 GMT, 27 min4 spills, 2.3 h, 20 Sep to 20 Sep22 Oct 2025 23:54 GMT, 34 min10 Nov 2025 16:00 GMT, 49 min12 Nov 2025 18:13 GMT, 18 min2 spills, 6.3 h, 14 Nov to 15 Nov28 Nov 2025 13:45 GMT, 3 min29 Nov 2025 20:35 GMT, 18 min4 Dec 2025 16:33 GMT, 42 min15 Dec 2025 18:21 GMT, 36 min18 Dec 2025 15:33 GMT, 8 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.

010k20k30kJan 2025: 135 h spilling ≈ 11,924 m³ (range 4,749-29,935 m³)JanFeb 2025: 2.7 h spilling ≈ 239 m³ (range 95-600 m³)FebMar 2025: 0.1 h spilling ≈ 8.9 m³ (range 3.5-22 m³)MarApr 2025: 0.0 h spilling ≈ 0.0 m³ (range 0.0-0.0 m³)AprMay 2025: 1.9 h spilling ≈ 168 m³ (range 67-423 m³)MayJun 2025: 0.0 h spilling ≈ 0.0 m³ (range 0.0-0.0 m³)JunJul 2025: 4.0 h spilling ≈ 354 m³ (range 141-890 m³)JulAug 2025: 0.0 h spilling ≈ 0.0 m³ (range 0.0-0.0 m³)AugSep 2025: 17 h spilling ≈ 1,497 m³ (range 596-3,758 m³)SepOct 2025: 3.9 h spilling ≈ 345 m³ (range 138-867 m³)OctNov 2025: 81 h spilling ≈ 7,158 m³ (range 2,851-17,970 m³)NovDec 2025: 78 h spilling ≈ 6,927 m³ (range 2,759-17,391 m³)Dec
Cubic metres (m³), estimate. Hours are measured by the event duration monitor.

Longest single spills

Started (GMT)OverflowDurationEstimated volume
5 Jan 2025, 15:54Tickhill Sewage Treatment Works2.0 days1,715 - 10,808 m³
14 Nov 2025, 07:46Tickhill Sewage Treatment Works1.6 days1,387 - 8,740 m³
20 Sep 2025, 16:15Tickhill Sewage Treatment Works10.6 h373 - 2,354 m³
9 Dec 2025, 05:01Tickhill Sewage Treatment Works9.8 h347 - 2,187 m³
18 Dec 2025, 14:00Tickhill Sewage Treatment Works9.6 h338 - 2,128 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 estimate28,613 m³range 11,397 - 71,834 m³
In litres28.6 millionrange 11.4 million - 71.8 million L
Olympic swimming pools11at 2,500 m³ each
Organic load, as people's raw sewage42,919person-days of untreated BOD

Assumed spill rate while spilling: 9.8 - 61.8 L/s (central 24.6 L/s), from a dry-weather flow of 9.8 L/s.

Pollutant releasedLowCentralHighConcentration used (low / typical / high)
BOD₅ (organic load) 456 kg2,575 kg14,367 kg 40 / 90 / 200 mg/L
Low/high: Europe range, Ellis & Jenkins 2005; typical: UK, Ellis & Jenkins 2005 (both via botturi)
Suspended solids 1,197 kg12,161 kg51,792 kg 105 / 425 / 721 mg/L
Low/high: Europe range; typical: UK, Ellis & Jenkins 2005 (via botturi)
Ammonium-N 22 kg180 kg668 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 14 kg74 kg388 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 1.1 trillion organisms28.6 trillion organisms718.3 trillion 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.

Tickhill Sewage Treatment Works

Storm tank at sewage works · discharges to Slutwell Stream

Spills 2025
77 (301 hours) · down 3% on 2024
Spills 2024
79 (319 hours)
Long-term average
69.2 spills a year (monitored since 2021)
Monitor uptime
100% of the year
High-spill reason (company)
Not asset maintenance - Hydraulic capacity
Investigation
UWWTR investigation ongoing, Operational investigation completed
Improvement
Operational improvement completed
WFD catchment
Torne from Ruddle to St Catherine's Well Stream (GB104028058400)
Outlet location
SK6019593636 (OS grid reference) · View on Apple Maps
EA ID / permit
SVT02318 · T/83/45915/R · company name: TICKHILL STW (SSTO)

Tickhill Sewage Treatment Works

Inlet overflow at sewage works · discharges to Slutwell Stream

Spills 2025
14 (22 hours) · down 7% on 2024
Spills 2024
15 (17 hours)
Long-term average
23.5 spills a year (monitored since 2021)
Monitor uptime
100% of the year
Investigation
UWWTR investigation ongoing, Operational investigation completed
Improvement
No improvement action in reporting period
WFD catchment
Torne from Ruddle to St Catherine's Well Stream (GB104028058400)
Outlet location
SK6019593636 (OS grid reference) · View on Apple Maps
EA ID / permit
SVT02319 · T/83/45915/R · company name: TICKHILL 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.