Storm overflow register · Northumbrian Water

Howdon sewage works: storm overflow spills 2025

Howdon sewage treatment works, run by Northumbrian Water, has 4 monitored storm overflows discharging to River Tyne Saline Estuary. In 2025 they recorded 269 spills totalling 2,225 hours, against 462 spills and 4,630 hours in 2024. By hours spilling, it ranks 1 of 183 Northumbrian Water works, where 1 spilled longest.

Works size: 933,912 population equivalent (NEWCASTLE (Howdon) 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.

JanFebMarAprMayJunJulAugSepOctNovDecHowdon STW42 spills, 12 h, 1 Jan to 1 Jan45 spills, 90.5 h, 5 Jan to 10 Jan5 spills, 0.1 h, 11 Jan to 11 Jan15 spills, 0.9 h, 12 Jan to 12 Jan14 spills, 11 h, 24 Jan to 24 Jan38 spills, 42.4 h, 26 Jan to 29 Jan10 spills, 0.9 h, 29 Jan to 29 Jan7 spills, 0.4 h, 31 Jan to 31 Jan92 spills, 67.8 h, 8 Feb to 12 Feb15 Feb 2025 21:56 GMT, 1 min9 spills, 5.7 h, 20 Feb to 20 Feb4 spills, 3.1 h, 26 Feb to 26 Feb2 spills, 4.1 h, 7 Mar to 7 Mar23 spills, 12.9 h, 12 Mar to 13 Mar22 Mar 2025 19:32 GMT, 7.2 h6 spills, 10.8 h, 24 May to 25 May7 spills, 7.7 h, 27 May to 27 May18 spills, 21.7 h, 29 May to 30 May14 spills, 4.1 h, 4 Jun to 5 Jun5 spills, 11.1 h, 7 Jun to 8 Jun3 spills, 6.5 h, 9 Jun to 10 Jun14 Jun 2025 15:06 GMT, 5.1 h2 spills, 0.8 h, 22 Jun to 22 Jun2 spills, 1.7 h, 26 Jun to 26 Jun11 spills, 16.1 h, 2 Jul to 3 Jul2 spills, 0.1 h, 6 Jul to 6 Jul4 spills, 1.2 h, 7 Jul to 8 Jul6 spills, 7.2 h, 14 Jul to 14 Jul3 spills, 7.8 h, 15 Jul to 16 Jul5 spills, 12.8 h, 19 Jul to 20 Jul3 spills, 5 h, 4 Aug to 4 Aug5 spills, 7.3 h, 11 Aug to 12 Aug12 spills, 3.5 h, 28 Aug to 29 Aug4 spills, 2.3 h, 31 Aug to 31 Aug3 spills, 6.3 h, 3 Sep to 3 Sep8 spills, 14.8 h, 10 Sep to 13 Sep10 spills, 26.6 h, 14 Sep to 16 Sep2 spills, 5.5 h, 17 Sep to 17 Sep4 spills, 47.2 h, 19 Sep to 22 Sep23 Sep 2025 10:50 GMT, 8 min1 Oct 2025 07:42 GMT, 8.3 h14 spills, 26.5 h, 2 Oct to 4 Oct23 spills, 25 h, 19 Oct to 20 Oct21 Oct 2025 17:44 GMT, 5 h6 spills, 11.5 h, 24 Oct to 25 Oct2 spills, 4.9 h, 27 Oct to 28 Oct5 spills, 8.9 h, 4 Nov to 5 Nov4 spills, 6 h, 9 Nov to 10 Nov13 spills, 14.5 h, 10 Nov to 12 Nov6 spills, 66.3 h, 12 Nov to 15 Nov2 spills, 1.8 h, 16 Nov to 17 Nov40 spills, 480.6 h, 18 Nov to 12 Dec7 spills, 24.4 h, 15 Dec to 16 Dec3 spills, 44.2 h, 17 Dec to 19 Dec2 spills, 1.1 h, 20 Dec to 20 Dec12 spills, 20.7 h, 21 Dec to 22 DecHowdon STW6 spills, 1.2 h, 1 Jan to 1 Jan2 spills, 63.9 h, 5 Jan to 7 Jan4 spills, 4.2 h, 24 Jan to 24 Jan12 spills, 16.2 h, 26 Jan to 28 Jan2 spills, 3.4 h, 8 Feb to 8 Feb7 spills, 9.6 h, 10 Feb to 11 Feb20 Feb 2025 14:41 GMT, 3.1 h2 spills, 1.2 h, 26 Feb to 26 Feb7 Mar 2025 13:17 GMT, 2.6 h4 spills, 10.3 h, 12 Mar to 13 Mar16 Mar 2025 15:10 GMT, 13 min22 Mar 2025 19:36 GMT, 4.4 h3 spills, 11.9 h, 24 May to 25 May27 May 2025 15:07 GMT, 5.3 h29 May 2025 04:24 GMT, 5.3 h3 Jun 2025 08:11 GMT, 15 min4 spills, 14.8 h, 4 Jun to 5 Jun2 spills, 9.9 h, 7 Jun to 7 Jun2 spills, 5 h, 9 Jun to 10 Jun14 Jun 2025 14:57 GMT, 3.6 h2 spills, 2.2 h, 26 Jun to 26 Jun28 Jun 2025 18:07 GMT, 3.1 h2 spills, 9.9 h, 2 Jul to 2 Jul7 Jul 2025 20:24 GMT, 2.6 h2 spills, 7.8 h, 14 Jul to 14 Jul15 Jul 2025 16:27 GMT, 4.7 h19 Jul 2025 14:51 GMT, 10.1 h3 Aug 2025 10:37 GMT, 16 min4 Aug 2025 07:45 GMT, 3.8 h2 spills, 1.3 h, 7 Aug to 7 Aug11 Aug 2025 20:57 GMT, 4.2 h2 spills, 4.1 h, 28 Aug to 29 Aug2 spills, 2 h, 31 Aug to 31 Aug1 Sep 2025 14:24 GMT, 97 min2 spills, 2.9 h, 3 Sep to 3 Sep4 Sep 2025 13:54 GMT, 45 min2 spills, 0.7 h, 8 Sep to 8 Sep2 spills, 6.5 h, 10 Sep to 11 Sep12 Sep 2025 22:10 GMT, 2.3 h5 spills, 10.9 h, 14 Sep to 15 Sep17 Sep 2025 05:29 GMT, 2 h2 spills, 45.1 h, 19 Sep to 21 Sep2 spills, 1 h, 28 Sep to 28 Sep2 spills, 7.7 h, 1 Oct to 1 Oct2 spills, 11.5 h, 2 Oct to 3 Oct2 spills, 0.4 h, 6 Oct to 6 Oct2 spills, 16.5 h, 19 Oct to 20 Oct21 Oct 2025 17:46 GMT, 2.5 h24 Oct 2025 16:43 GMT, 10.8 h26 Oct 2025 17:31 GMT, 11 min27 Oct 2025 23:42 GMT, 3.3 h4 spills, 6.3 h, 4 Nov to 5 Nov9 Nov 2025 18:23 GMT, 4 h3 spills, 11.9 h, 10 Nov to 12 Nov4 spills, 54.8 h, 12 Nov to 15 Nov16 Nov 2025 23:07 GMT, 80 min3 spills, 52.5 h, 18 Nov to 21 Nov16 spills, 173.6 h, 22 Nov to 2 Dec20 spills, 90.2 h, 4 Dec to 10 Dec12 Dec 2025 09:34 GMT, 70 min3 spills, 19.1 h, 15 Dec to 16 Dec4 spills, 16 h, 17 Dec to 19 Dec2 spills, 5.1 h, 22 Dec to 22 Dec2 spills, 0.6 h, 29 Dec to 29 DecHowdon STW14 spills, 39.8 h, 5 Jan to 7 Jan2 spills, 0 h, 24 Jan to 24 Jan6 spills, 5.4 h, 27 Jan to 27 Jan4 spills, 1.6 h, 24 May to 24 May15 spills, 1.2 h, 2 Jul to 2 Jul3 spills, 1.3 h, 15 Jul to 15 Jul11 spills, 6.7 h, 19 Jul to 19 Jul6 spills, 0.2 h, 1 Aug to 1 Aug2 spills, 0.4 h, 28 Aug to 28 Aug16 spills, 3 h, 15 Sep to 15 Sep41 spills, 18.4 h, 20 Sep to 21 Sep20 spills, 5.1 h, 3 Oct to 3 Oct10 spills, 7.8 h, 19 Oct to 20 Oct16 spills, 0.3 h, 24 Oct to 24 Oct34 spills, 29 h, 13 Nov to 14 Nov11 spills, 17 h, 18 Nov to 19 Nov45 spills, 10.8 h, 23 Nov to 25 Nov7 spills, 4.9 h, 28 Nov to 28 Nov12 spills, 8.7 h, 29 Nov to 30 Nov17 spills, 11.5 h, 1 Dec to 1 Dec18 spills, 3.9 h, 5 Dec to 6 Dec11 spills, 7.7 h, 7 Dec to 7 Dec16 spills, 3.3 h, 9 Dec to 9 Dec22 spills, 1.2 h, 17 Dec to 18 DecHowdon STW24 May 2025 03:14 GMT, 21 min19 Jul 2025 18:06 GMT, 20 min10 spills, 3.3 h, 20 Sep to 20 Sep

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.

010M20M30MJan 2025: 289 h spilling ≈ 4.6 million m³ (range 1.8 million-11.6 million m³)JanFeb 2025: 94 h spilling ≈ 1.5 million m³ (range 598,514-3.8 million m³)FebMar 2025: 42 h spilling ≈ 665,685 m³ (range 265,156-1.7 million m³)MarApr 2025: 0.0 h spilling ≈ 0.0 m³ (range 0.0-0.0 m³)AprMay 2025: 64 h spilling ≈ 1.0 million m³ (range 410,482-2.6 million m³)MayJun 2025: 68 h spilling ≈ 1.1 million m³ (range 434,066-2.7 million m³)JunJul 2025: 90 h spilling ≈ 1.4 million m³ (range 571,106-3.6 million m³)JulAug 2025: 34 h spilling ≈ 548,870 m³ (range 218,626-1.4 million m³)AugSep 2025: 199 h spilling ≈ 3.2 million m³ (range 1.3 million-8.0 million m³)SepOct 2025: 147 h spilling ≈ 2.4 million m³ (range 938,245-5.9 million m³)OctNov 2025: 700 h spilling ≈ 11.2 million m³ (range 4.5 million-28.1 million m³)NovDec 2025: 503 h spilling ≈ 8.0 million m³ (range 3.2 million-20.2 million m³)Dec
Cubic metres (m³), estimate. Hours are measured by the event duration monitor.

Longest single spills

Started (GMT)OverflowDurationEstimated volume
29 Nov 2025, 09:23Howdon STW3.7 days573,231 - 3.6 million m³
23 Nov 2025, 07:54Howdon STW2.9 days435,978 - 2.7 million m³
5 Jan 2025, 08:34Howdon STW2.8 days434,916 - 2.7 million m³
5 Jan 2025, 07:41Howdon STW2.6 days392,529 - 2.5 million m³
4 Dec 2025, 21:41Howdon STW2.3 days355,029 - 2.2 million 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 estimate35.6 million m³range 14.2 million - 89.4 million m³
In litres35.6 billionrange 14.2 billion - 89.4 billion L
Olympic swimming pools14,239at 2,500 m³ each
Organic load, as people's raw sewage53.4 millionperson-days of untreated BOD

Assumed spill rate while spilling: 1,770.5 - 11,159.4 L/s (central 4,445.0 L/s), from a dry-weather flow of 1,770.5 L/s.

Pollutant releasedLowCentralHighConcentration used (low / typical / high)
BOD₅ (organic load) 567,180 kg3.2 million kg17.9 million kg 40 / 90 / 200 mg/L
Low/high: Europe range, Ellis & Jenkins 2005; typical: UK, Ellis & Jenkins 2005 (both via botturi)
Suspended solids 1.5 million kg15.1 million kg64.4 million kg 105 / 425 / 721 mg/L
Low/high: Europe range; typical: UK, Ellis & Jenkins 2005 (via botturi)
Ammonium-N 26,941 kg224,268 kg831,147 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 17,015 kg92,555 kg482,601 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 1.4 × 10¹⁵ organisms3.6 × 10¹⁶ organisms8.9 × 10¹⁷ 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.

Howdon STW

Inlet overflow at sewage works · discharges to River Tyne Saline Estuary

Spills 2025
120 (1,238 hours) · down 44% on 2024
Spills 2024
214 (2,523 hours)
Long-term average
173.0 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
No improvement action in reporting period
WFD catchment
TYNE (GB510302310200)
Outlet location
NZ3370066130 (OS grid reference) · View on Apple Maps
EA ID / permit
NWL00714 · 235/1695

Howdon STW

Inlet overflow at sewage works · discharges to River Tyne Saline Estuary

Spills 2025
113 (795 hours) · down 29% on 2024
Spills 2024
160 (1,379 hours)
Long-term average
136.2 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
No improvement action in reporting period
WFD catchment
TYNE (GB510302310200)
Outlet location
NZ3370066130 (OS grid reference) · View on Apple Maps
EA ID / permit
NWL00713 · 235/1695

Howdon STW

Inlet overflow at sewage works · discharges to River Tyne Saline Estuary

Spills 2025
33 (187 hours) · down 60% on 2024
Spills 2024
83 (723 hours)
Long-term average
67.5 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
No improvement action in reporting period
WFD catchment
TYNE (GB510302310200)
Outlet location
NZ3370066130 (OS grid reference) · View on Apple Maps
EA ID / permit
NWL00712 · 235/1695

Howdon STW

Inlet overflow at sewage works · discharges to River Tyne Saline Estuary

Spills 2025
3 (3.9 hours) · down 40% on 2024
Spills 2024
5 (4.1 hours)
Long-term average
7.7 spills a year (monitored since 2020)
Monitor uptime
100% of the year
Investigation
Env Act (SODRP) investigation ongoing
Improvement
No improvement action in reporting period
WFD catchment
River Tyne (GB510302310200)
Outlet location
NZ3370066130 (OS grid reference) · View on Apple Maps
EA ID / permit
NWL00711 · 235/1804

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 Northumbrian 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.