Storm overflow register · Northumbrian Water

Branxton sewage works: storm overflow spills 2025

Branxton sewage treatment works, run by Northumbrian Water, has 1 monitored storm overflow discharging to River Till Trib. In 2025 it recorded 75 spills totalling 270 hours, against 57 spills and 177 hours in 2024. By hours spilling, it ranks 77 of 183 Northumbrian Water works, where 1 spilled longest.

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.

JanFebMarAprMayJunJulAugSepOctNovDecBranxton STW4 spills, 1.3 h, 1 Jan to 1 Jan2 spills, 0.5 h, 5 Jan to 5 Jan4 spills, 1.3 h, 26 Jan to 27 Jan2 spills, 0.3 h, 12 Mar to 12 Mar7 spills, 0.6 h, 22 Mar to 22 Mar3 spills, 0.1 h, 16 Apr to 16 Apr3 spills, 0.5 h, 23 May to 24 May13 spills, 1.1 h, 26 May to 27 May2 spills, 0.7 h, 29 May to 29 May4 spills, 0.3 h, 3 Jun to 3 Jun7 spills, 1.2 h, 5 Jun to 5 Jun30 spills, 3.1 h, 6 Jun to 7 Jun16 spills, 1.3 h, 9 Jun to 9 Jun13 spills, 1.3 h, 14 Jun to 14 Jun2 spills, 0.1 h, 17 Jun to 17 Jun33 spills, 22.4 h, 21 Jun to 24 Jun6 spills, 0.7 h, 2 Jul to 2 Jul2 spills, 0.1 h, 5 Jul to 5 Jul7 Jul 2025 18:25 GMT, 2 min2 spills, 0.5 h, 27 Aug to 27 Aug3 spills, 11.3 h, 28 Aug to 29 Aug3 spills, 0.7 h, 30 Aug to 31 Aug25 spills, 7.9 h, 31 Aug to 3 Sep2 spills, 0.4 h, 7 Sep to 7 Sep4 spills, 2.3 h, 10 Sep to 11 Sep3 spills, 1.1 h, 13 Sep to 13 Sep49 spills, 23.9 h, 14 Sep to 18 Sep5 spills, 3.1 h, 20 Sep to 21 Sep5 spills, 2.2 h, 2 Oct to 3 Oct6 Oct 2025 01:21 GMT, 4 min6 spills, 4.2 h, 19 Oct to 20 Oct6 spills, 1.4 h, 24 Oct to 24 Oct27 Oct 2025 02:13 GMT, 48 min27 Oct 2025 22:21 GMT, 42 min2 spills, 0.8 h, 1 Nov to 1 Nov2 spills, 1.2 h, 4 Nov to 4 Nov11 Nov 2025 11:37 GMT, 62 min32 spills, 8.8 h, 13 Nov to 13 Nov7 spills, 6.2 h, 18 Nov to 19 Nov3 spills, 1.2 h, 20 Nov to 20 Nov16 spills, 7.7 h, 23 Nov to 24 Nov18 spills, 134.5 h, 26 Nov to 2 Dec3 spills, 4.4 h, 5 Dec to 6 Dec9 spills, 3.4 h, 7 Dec to 7 Dec2 spills, 1.3 h, 9 Dec to 9 Dec10 Dec 2025 08:27 GMT, 42 min14 Dec 2025 02:55 GMT, 10 min5 spills, 1.1 h, 17 Dec to 17 Dec21 Dec 2025 20:31 GMT, 10 min

Hours spilling by month, 2025

050100150Jan 2025: 3.0 hours spillingJanFeb 2025: 0.0 hours spillingFebMar 2025: 0.8 hours spillingMarApr 2025: 0.1 hours spillingAprMay 2025: 2.3 hours spillingMayJun 2025: 30 hours spillingJunJul 2025: 0.8 hours spillingJulAug 2025: 13 hours spillingAugSep 2025: 39 hours spillingSepOct 2025: 9.3 hours spillingOctNov 2025: 123 hours spillingNovDec 2025: 50 hours spillingDec
Hours, measured by the event duration monitor.

Longest single spills

Started (GMT)OverflowDuration
27 Nov 2025, 13:41Branxton STW5.0 days
28 Aug 2025, 14:43Branxton STW11.1 h
23 Jun 2025, 17:13Branxton STW10.7 h
16 Sep 2025, 01:13Branxton STW6.9 h
24 Jun 2025, 04:29Branxton STW3.6 h

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.

This works serves fewer than 2,000 people, or was not matched to a UWWTD report, so its size is not published. The population equivalent above is a placeholder of 1,000. Enter the population served if you know it.

Volume, central estimate4,625 m³range 1,842 - 11,610 m³
In litres4.6 millionrange 1.8 million - 11.6 million L
Olympic swimming pools1.8at 2,500 m³ each
Organic load, as people's raw sewage6,937person-days of untreated BOD

Assumed spill rate while spilling: 1.9 - 11.9 L/s (central 4.8 L/s), from a dry-weather flow of 1.9 L/s.

Pollutant releasedLowCentralHighConcentration used (low / typical / high)
BOD₅ (organic load) 74 kg416 kg2,322 kg 40 / 90 / 200 mg/L
Low/high: Europe range, Ellis & Jenkins 2005; typical: UK, Ellis & Jenkins 2005 (both via botturi)
Suspended solids 193 kg1,965 kg8,371 kg 105 / 425 / 721 mg/L
Low/high: Europe range; typical: UK, Ellis & Jenkins 2005 (via botturi)
Ammonium-N 3.5 kg29 kg108 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 2.2 kg12 kg63 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 184.2 billion organisms4.6 trillion organisms116.1 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.

Branxton STW

Inlet overflow at sewage works · discharges to River Till Trib

Spills 2025
75 (270 hours) · up 32% on 2024
Spills 2024
57 (177 hours)
Long-term average
46.0 spills a year (monitored since 2021)
Monitor uptime
93% of the year
High-spill reason (company)
Not asset maintenance - Hydraulic capacity
Investigation
Env Act (SODRP) investigation ongoing, Operational investigation ongoing
Improvement
Operational improvement ongoing
WFD catchment
Pallins Burn Catch (trib of Till) (GB102021072990)
Outlet location
NT8915137910 (OS grid reference) · View on Apple Maps
EA ID / permit
NWL00189 · 210/0039

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.