worker in sewer pipe underground
Calendar 28 April, 2022 (Updated 13 July, 2023)

Construction Professionals are Worried about Waste Going into Sewers from Building Sites

Over the past few years, increased media focus has been on how illegally fly-tipped and exported waste from the construction industry can harm the environment.

However, there have so far been few column inches about how similar waste enters the environment via our drainage system directly from building sites – despite it being a well-known issue for most groundworkers and construction professionals.

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In this study, we explain how and why waste lost via the sewage system from building sites is an issue and reveal the findings of our survey of over 350 building trade professionals. The new study highlights how the vast majority of professionals familiar with building sites are concerned about the environmental impact of this issue and believe it to be widespread across the industry.

How much waste does the construction industry produce?

As one of the largest producers of commercial waste in the UK, the construction industry has long been challenged by how it disposes of the massive quantities of rubbish that it produces every year. According to PCB Today, waste from the building trade accounts for over one-third of all annual UK waste output¹.

If that wasn’t bad enough, the type of waste that the industry creates is also problematic for the environment. Our recent study of Department for Environment, Food & Rural Affairs (DEFRA) data found a 45.72% increase in the amount of plastic waste from UK construction businesses over the last two years. Many plastics are particularly bad for the environment as they are often unbiodegradable.

How does waste from the construction industry get into the sewer system?

If you work in the building trade, chances are you are already aware that potentially harmful waste products such as silt, mud, litter, plastic, excess building materials and discarded tools abound on construction sites. Most of this waste gets disposed of properly via specialist removal companies, while some of it gets exported, or even illegally dumped by unscrupulous individuals.

However, a not-insignificant amount of it also ends up entering manholes on building sites, where it enters the national sewage system. Often this is accidental as a result of waste falling into open manholes, however, there may also be a minority of workers who dispose of waste deliberately via the drainage system. Disposing of waste this way would be more convenient and cheaper than traditional methods of waste disposal.

Although most of the waste that enters the UK sewage system is treated before being released back into the environment, sadly a large amount of untreated waste can end up in rivers during storm overflow and pollution events.

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How much construction waste ends up entering the sewage system?

The problem of waste entering manholes on construction sites is largely hidden from public view as it often happens by accident and is rarely reported as a serious incident to senior managers, industry bodies or environmental watchdogs. This makes it very difficult to quantify the exact extent of the problem. We spent a long time researching the issue, and sadly we could find very few government or industry bodies collecting statistics on this issue.

As a result, we decided to run our own study and surveyed 363 professionals who work on or for UK construction sites about their knowledge of waste entering the drainage system on construction sites. The results of our study reveal that the issue is widespread, with 96% of survey respondents saying that they had seen, experienced or heard about this happening on building sites they have worked with. If this is happening regularly on most building sites, it is safe to assume that large quantities of construction industry waste is making its way into the sewage system.

In addition to environmental concerns are the obstructions that building materials create in the UK’s sewer systems. In 2019, a ‘concreteberg’ weighing 105 tonnes received national media attention for blocking a London sewer. Concretebergs are giant masses of concrete from building sites that enter and block the UK’s sewer systems. The data shows that they are far from rare. According to Construction News, concretebergs of a significant size happen every year. Welsh Water reported 220 sewer blockages caused by concrete and other construction materials such as bricks and rubble in just one year.

The majority of professionals surveyed were also concerned about the environmental impact of waste entering the UK’s drainage system from construction sites. 98% said that waste entering manholes on construction sites is having a negative impact on the environment and the water system. 74% believed the environmental impact of this issue was likely to be ‘very negative’, while 24% felt that the problem is ‘slightly negative’. 96% of respondents said that they’d welcome a solution which prevents silt, mud and litter from accidentally falling into drainage.

How does construction waste that enters the sewage system become an issue for the environment?

Once waste enters the sewage system, it is normally screened and treated before it is released into the rivers to limit its impact on the environment. However, every year large amounts of untreated waste from the sewer system sadly ends up being released into the environment by water companies during storm overflow events. Storm overflow events happen when heavy rainfall puts a larger-than-usual strain on the sewage system. During these events the water companies release untreated sewage into the environment to ease pressure on the system and to prevent raw sewage from backing up into buildings and peoples’ homes.

However, when this happens, raw sewage can end up polluting rivers, often with devastating consequences for local wildlife and nature. According to a UK parliament committee earlier this year², this 'chemical cocktail’ of sewage, slurry and plastic waste can cause high levels of nutrients, such as phosphorus and nitrogen, to build up in our rivers. This then chokes the rivers with algal blooms which reduces oxygen levels and sadly suffocates wildlife such as fish, plants and invertebrates.

According to the conservation charity The Rivers Trust³, sewage is discharged into rivers across the UK and Ireland on a daily basis due to overspill events.

sewage treatment plant

Revealed: Where in the UK does crude and storm sewage waste get released into the environment?

While not everything that enters the environment from the sewage system is necessarily highly hazardous, it does appear to be a growing problem for the environment. We analysed the latest pollution data from the Department for Environment, Food & Rural Affairs (DEFRA)⁴. Our analysis reveals that there was a 23.26% rise in the number of reported pollution incidents which involved the release of crude or storm sewage into the environment in England last year.

The data shows that reported incidents of pollution from crude or storm sewage increased from 43 in 2020 to 53 last year. In addition, 49 of the incidents in 2021 were recorded as having a ‘major’ or ‘significant’ environmental impact on water bodies such as rivers – representing a 25.64% year-on-year increase.

The study of DEFRA data also reveals the areas of England where the most pollution incidents from crude and storm sewage have taken place since 2019, with Northamptonshire, Cornwall, Kent and Surrey topping the list.

Counties & Local Authorities in England with the most sewage pollution incidents since 2019

  • Northamptonshire: 8
  • Cornwall County: 7
  • Kent County: 7
  • Surrey County: 7
  • Lincolnshire County: 6
  • Cambridgeshire County: 5
  • Hertfordshire County: 4
  • Norfolk County: 4
  • Oxfordshire County: 4
  • Bedfordshire County: 3
  • Buckinghamshire County: 3
  • Derbyshire County: 3
  • Devon County: 3
  • East Sussex County: 3
  • Hampshire County: 3
  • North Yorkshire County: 3
  • Somerset County: 3
  • West Sussex County: 3
  • Worcestershire County: 3
  • Enfield London Boro: 3
  • Harrow London Boro: 3
  • Leeds District: 3
  • Sheffield District: 3
  • Walsall District: 3
  • Cumbria County: 2
  • Bracknell Forest: 2
  • City Of Peterborough: 2
  • City Of Plymouth: 2
  • East Riding Of Yorkshire: 2
  • South Gloucestershire: 2
  • Swindon: 2
  • West Berkshire: 2
  • York: 2
  • Camden London Boro: 2
  • Barnet London Boro: 2
  • Wakefield District: 2
  • Dorset County: 1
  • Durham County: 1
  • Gloucestershire County: 1
  • Leicestershire County: 1
  • Northumberland County: 1
  • Nottinghamshire County: 1
  • Staffordshire County: 1
  • Suffolk County: 1
  • Wiltshire County: 1
  • Milton Keynes: 1
  • Rutland: 1
  • Thurrock: 1
  • Hillingdon London Boro: 1
  • Doncaster District: 1
  • Bexley London Boro: 1
  • Sunderland District: 1
  • City Of Westminster London Boro: 1
  • Kingston Upon Thames London Boro: 1
  • Calderdale District: 1
  • Newcastle Upon Tyne District: 1
  • Rotherham District: 1
  • Bromley London Boro: 1
  • Sefton District: 1
  • Kirklees District: 1
  • Rochdale District:1
  • Harlow District: 1

What about other waste from the construction industry?

Illegal dumping of construction waste is also a big problem that can have devastating consequences for the environment. However, our study of Department for Environment, Food & Rural Affairs (DEFRA) data on illegal dumping incidents⁵ highlights some progress for the construction industry here.

The data reveals a 54.55% reduction in illegal dumping incidents from ‘construction, demolitions, and excavations’ in the last five years in England and a 23.27% decrease in the last year alone. Although the total number of illegal dumping incidents across all sectors has decreased by 40.44%, the reduction in illegal dumping of construction waste is nearly 15% greater than overall. This is not insignificant, given that construction, demolition, and excavation waste accounts for 62% of all UK waste, according to DEFRA.

Of all the incidents of illegal dumping of construction waste in the last five years, five were categorised as having a 'significant impact' on the environment, while most other incidents have been classified as having a minimal impact.

The most common locations for the illegal dumping of waste in England in the last two years are Hertfordshire & North London (119 incidents), East Anglia (72), the Thames area (53) and the Kent, South London & East Sussex area (42).


¹How is the construction sector combatting its waste? (

²‘Chemical cocktail’ of sewage, slurry and plastic polluting English rivers puts public health and nature at risk - Committees - UK Parliament

³ Raw sewage in our rivers | The Rivers Trust

Environmental Pollution Incidents (Category 1 and 2) -

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Mark Chambers Drainfast Team Portrait

Written by
Mark Chambers

Marketing Manager

As Marketing Manager, Mark plays an active role in running strategic projects to increase our brand profile.

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