The Great River Aire Outfall Safari 2023

Building a picture of the pollution problems facing the River Aire

In Winter 2023 our volunteers set off to build a picture of how pollution entered the River Aire in Bradford and Craven. Their findings should give us grave cause for concern.

View an interactive map of our findings

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Click on the dots and zoom our results map, to see our findings near you


What were we looking for?

Our volunteers walked sections of our river in Bradford, Keighley, and Craven, looking for pipes in the river bank. We asked them to do this in dry weather when it had been at least two days since it rained. By doing this, we knew that any liquid flowing out of them was highly likely to be effluent from someone's home or business. Not rainwater.

An Outfall Safari along the River Aire 2023

What we are particularly keen to find are called "misconnections." Locations where homeowners, developers and businesses have plumbed waste from sinks, toilets and drains into surface water drains. These flow to rivers without treatment. These misconnections are the responsibility of the homeowner, not the water companies.

We believe that not enough is being done to find them. Too much of the response to them is reactive, not proactive. People should be finding them before they cause serious harm to our river.


Pollution from misconnections causes is one of the missing parts from the public conversation about the work that is urgently needed to reduce the harm sewage is causing to our rivers.

Yorkshire Water // What is a Misconnection?


How did we record our results?

Over 70 volunteers were trained to walk the river to look for polluting pipes, using the Zoological Society for London "Outfall Safari" methodology.

Over a 3 month period between October and December, these volunteers walked their local watercourses, recording all the pipes they found over 20cm in diameter. Scoring them out of 20, assessing visible signs of pollution and their effect on the river.

Photographs and scores were then logged on a smartphone app. and submitted to Aire Rivers Trust for review. Any outfall showing clear signs of pollution or scoring over 10 was reported by the volunteer to the Environment Agency (EA) pollution hotline for further investigation by the EA or Yorkshire Water.


What did we find?

In total we found 660 pipes or "outfalls."

The good news is that many of the pipes, or outfalls, we found were clean. Most will be surface water drains from which rainwater flows during storms.

It is important if you own a business that you know which of your drains are surface water drains. We have seen devastating pollution events in the River Worth where employees poured substances down drains believing they were heading for the sewers (and treatment/dilution) but instead went straight into the river.

Even seemingly innocuous substances like milk and food washings can be the cause of some of the worst pollution in rivers.

Polluting substances are rated by their biological oxygen demand (BOD) — the amount of oxygen bacteria consume as they break down organic matter. If a watercourse is contaminated with these pollutants, so much oxygen is consumed that oxygen levels become too low to support aquatic life and death results. The higher the BOD, the more serious the pollution risk.

Raw sewage requires ~300mg/L. Even worse, dairy slurry requires ~3,200mg/L, and milk requires ~30,000mg/L!


How many outfalls did we check?

Overall, our volunteers checked 660 outfalls! These were made up of:

523 Clean outfalls (Score 0-0.9) 79% of Outfalls Record 

76 Low Risk Outfalls (Score 1-2.9) 12% of Outfalls Recorded 

39 Medium Risk Outfalls (Score 3-5.9) 6% of Outfalls Recorded 

22 High Risk Outfalls (Score 6-20) 3% Of Outfalls Recorded 

What pollution did we find?

Within the medium and high-risk outfalls, the largest cause of pollution was found to be misconnected private pipes.

47% Urban Misconnections

22% Public Sewer System

17% Urban & land-based Runoff

14% Land-based business


Pollution hotspots

When the high and medium-risk outfalls we found are displayed on a heat map of the Aire Valley, clear pollution hotspots can be seen.  

Many of these are hidden spaces with huge potential for nature to thrive in our river. We need people to keep reporting pollution in these hotspots to make the authorities take them seriously.

 Hotspot no.1 Keighley

In Keighley, we found a leaking sewer and fuel oil leaking from an old Mill. Click on the points to see photos of what we found.

Heavily fuel oil pollution Mariners Road

 Hotspot no.2 Hirst Wood

Around Hirst Wood, we found multiple combined sewer overflows that concern us together with several misconnections and agricultural pollution. This area is already impacted by the treated effluent from Dowley Gap sewage treatment works.

A misconnection in Hirst Wood Nature Reserve

 Hotspot no.3 Barnsley Beck, Baildon

The outfall of the hidden Barnsley Beck was found to be heavily polluted. The red dot on the map shows the end of Barnsley Beck but we believe there are many hidden misconnections into it as it runs below Baildon.

Pollution discharging from Barnsley Beck

Hotspot no.4 Fagley Beck

On Fagley Beck, we found a severe misconnection that was discharging detergent into the beck and heavy sediment run-off from on construction site.

Detergent pollution on Fagley Beck

Reported Pollution

Of the eleven outfalls reported to the authorities, 64% of the problems were caused by misconnected private pipes. 27% were connected to slurry runoff from manure stores or other point sources on agricultural land, and 9% were from building site runoff.

Private pipe networks and farm discharges have no formal government or water company-operated monitoring system to check their discharges to the river.

Interestingly, no Yorkshire Water or private sewer assets needed reporting to the authorities in this survey. 

Sewer overflows

This map shows the effluent spills from permitted (licensed) sewer overflows in 2022.

Clicking on some of the largest circles tells a shocking story of the number and frequency of spills. In the Aire catchment, combined sewers spilt for 77,350 hours directly into our rivers in 2022.

We should not underestimate the impact of these sewage discharges. Across the Aire, we have long-term volunteers who count river bugs to monitor the health of the river. The death (or decline) of these "river flies" is often the best and earliest indicator that something has gone wrong.

Sewer spills wash nutrients, bacteria and plastic waste in the form of wet wipes and sanitary products into our river.

We expect the figures that Yorkshire Water reports for 2023 will be higher.

A crucial difference between sewer overflows and the pipes we found is discharges from misconnections are much less likely to be diluted by stormwater. They happen every day, even when the river is very empty.

Our river needs both investment to improve the worst sewer overflows and for the number of misconnections to dramatically reduced.

 

Further study

This is the first year we have done an Outfall Safari. There is still much of the Aire Valley that needs volunteers to walk it. These areas are shown in grey on the map, including: 

  • Earby and Broughton Becks 
  • Harden Beck System 
  • Guiseley and Yeadon Becks 
  • All Lower Aire tributaries, particularly within the Leeds conurbation 

This shows the need to carry out future outfall safaris.

Surveying these catchments would give us a good baseline map of outfalls that we can share with others. We also plan to repeat surveys to check for the impact of new developments.  

The pink waterbodies represent the area where we want to carryout a 'diffuse pollution spotting' citizen science project to identify land-based pollution such as soil erosion or manure releases to the river.


If you would like a more detailed insight please read the Full Great Aire River Outfall Safari Report here:

What next?

In 2023, we walked under half of our catchment. We still have need to explore most of Leeds & many other urban areas.

Help to fund us to repeat this in 2024 with the Big Give Green Match Fund between 17 - 24 April

Our 2023 work was funded by public donations through our 2023 Big Give Green Match Fund appeal.

How can you get involved?

  • Report pollution by calling the Environment Agency on 0800 807060
  • Become a river monitor
  • Don’t flush wipes & sanitary waste
  • Share what we found & demand change

Heavily fuel oil pollution Mariners Road

A misconnection in Hirst Wood Nature Reserve

Pollution discharging from Barnsley Beck