The Great River Aire Outfall Safari 2023
Building a picture of the pollution problems facing the River Aire
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.
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.
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.
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.
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!
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
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
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.
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.
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.
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.
On Fagley Beck, we found a severe misconnection that was discharging detergent into the beck and heavy sediment run-off from on construction site.
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.
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.
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:
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.
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.