Sewage, trash and the Environment Agency
Water quality and pollution are key issues affecting the health of the Welsh Harp (Brent Reservoir). The Environment Agency plays a fundamental role in both.
Among its statutory duties, Environment Agency (EA) is responsible for water quality in the principal rivers, streams, canals and lakes of the UK, and sets the standards for any discharges into them. It also takes responsibility for conservation and ecology, prioritising the protection and improvement of land and biodiversity.
The process of improvement in water quality falls under the Water Framework Directive, which was enacted in the UK in 2003. The Water Framework Directive’s original objective was that all water bodies (rivers, lakes and groundwater) would be in 'good' overall environmental health by 2015, with the EA reporting on the progress towards the meeting of this target every three years. The 2015 deadline wasn't met. It then became 2021. That wasn't met either, and now it has been pushed it back to 2027. Judging from the Water Quality in Rivers report by the UK Parliament’s Environmental Audit Committee published in January 2022, it would suggest the chances of reaching the deadline by 2027 are slim.
Why is this happening? And what is the impact on the Welsh Harp and its ecology? In 2021, we had a series of discussions with Samantha Lumb, area director of the Hertfordshire and North London office of the Environment Agency to address issues of water quality, pollution and trash screen maintenance affecting the two rivers - the River Brent and Silk Stream - that flow into the Welsh Harp SSSI.
River Brent trash screen, December 2021
Water quality
Current government data rates both the water quality of the River Brent (upstream of the reservoir) and the water quality of the Silk Stream as 'moderate'. Within this generous classification, key metrics are of particular concern to the Welsh Harp: invertebrate numbers (food sources for bird species) are ‘poor’; phosphate concentrations (which lead to toxic algae and oxygen depletion) are ‘poor’; dissolved oxygen levels (essential for aquatic life) are ‘bad’; metal content (toxic) is ‘high’; and levels of priority chemical substances (toxic) are excessive. The classification of both rivers may be deemed ‘moderate’, but it is hard to paint a good picture of water health at the Welsh Harp, and how it impacts on issues of conservation.
Urban runoff
The poor condition of the water is caused primarily by urban run-off - rain flushed off roads, driveways, car parks and contaminated land into surface drains that lead to local rivers, entering via outfalls; this is regular rainwater laced with a long list of surface pollutants, not least engine oil, petrol, diesel, rubber, metals, paint from road markings, de-icing chemicals, salt, screen wash, and herbicides from roadside weed control.
EA oversees special tanks called interceptors that act as a filter on the water entering rivers from outfalls. Interceptors are designed to separate out dangerous contaminants, and in December 2021 EA told us officers had been out on site with Highways England to inspect them and other general highway drainage around the Welsh Harp.
Yet the Silk Stream still runs black after heavy rain, and frothing effluence from ammonia and phosphate loads is visible almost daily on the River Brent, 100m from the protected SSSI wetlands of the Welsh Harp.
The reality is a fraction of what needs to be done to control urban runoff is being done. EA are overstretched and underfunded. Morale is low. Angry voices from the public are loud. The Silk Stream is estimated to be made up of 60-70% urban runoff. Sediment carried by the rivers massing in the SSSI marshlands at the river mouths is toxic. Water quality is at best, moderate, and aquatic life - the food source for breeding birds and overwintering wildfowl notified under the SSSI citation - severely compromised. Effectively, the reservoir is in danger of slowly dying and solidifying.
Misconnections
The second biggest pollutant comes from misconnections - household waste and soil pipes wrongly connected to rainwater drains, which then head to rivers, instead of to sewers.
Thames Water - who are in charge of wastewater in the River Brent and Silk Stream catchment - is legally obliged to track polluting outfalls and trace the offending households. According to ZSL’s report Tackling Pollution in London’s Rivers (2017), 90% of households are said to rectify mistakes once informed, with 10% needing local council enforcement action, but are Thames Water informing enough households?
EA - who oversee Thames Water’s activities - told us in May 2021 that Thames Water had resolved 162 out of 194 identified misconnections from residential properties affecting surface water outfalls on the Brent and Silk Stream catchments. It did not tell us how long that took Thames Water, or how many more misconnections are unaccounted for, but it is thought North London is particularly blighted by misconnections - a recent estimate put it at an eye-watering 300,000 households. In December 2021, EA told us it was still working with Thames Water on misconnections in the area.
The same ZSL report - commissioned in part (and not without irony) by Thames Water itself - concluded bluntly that “a five-fold increase in investment by Thames Water in tracing, identifying and remedying misconnections” was needed before 2025. Why? Because in the five years running up to 2020, EA allowed Thames Water to budget for tackling just 40 outfalls per year across the WHOLE of their service area. To put that in perspective, in a survey of a just a third of river channels in the River Brent catchment, ZSL identified 29 seriously polluting outfalls alone, of which several are immediately upstream of the Welsh Harp.
In response, Thames Water have proposed improving their annual outfall track and trace from 40 to 100 for the period 2020-2025.
Again it would seem a fraction of what needs to be done is being done.
Silk Stream, downstream of auto-trash screen, December 2021
Plastic and debris
Inflowing plastic and debris remain a threat to the reservoir. In March 2021 - following our first crisis report - Natural England admitted this was now an ecological concern.
Back in the late 1980s a trash screen was installed on the River Brent, and another on the Silk Stream in the 1990s. Both are a little way upstream of the reservoir and act as a protective measure against debris inflow, but both are now heavily overstretched.
The Silk Stream sports the Edgware auto-trash screen, which collects accumulated rubbish from the river channel with an overhead claw at timed intervals. The debris is deposited into a waterside skip for removal by lorry. In contrast, the River Brent has a static grill-type trap near Priestley Way, which needs manual maintenance and emptying.
EA manage both screens. On several occasions they have told us that "both trash screens are cleared of debris on a weekly basis" by "field teams", but there are clearly periods when this is not happening, particularly on the River Brent, where a field team can mean an occasional visit from one man with a wheelbarrow.
The upshot is the River Brent trash screen is almost permanently clogged with storm debris, plastic bottles, polystyrene, fly-tipped building materials (plasterboard, insulation panels, timber, sacks), bottle tops, cans and microplastics, and a scum of sewage and frothing effluence.
High water can then take the contents up, over and around the congested screen, and down towards the reservoir, bypassing even the floating boom designed to hold back surface pollutants.
In heavy rain, due to debris congestion at the screens, burst banks also mean the protected SSSI wet woodland around the screens is littered with a permanent carpet of debris and sewage.
Why is this allowed to happen?
The crux of the matter lies in how EA are forced to prioritise its statutory duties through underfunding and under-resourcing. Forced to make a choice, it puts flood prevention ahead of protection and improvement of land and biodiversity at the Welsh Harp. As long as water can flow freely enough through the screens, and properties and businesses upstream are not threatened by flooding caused by debris congestion at the screens, ecology can be allowed to suffer.
EA appeared to confirm this in December 2021, when it told us, “We still regularly visit the site to clear debris from the screen as part of our regular maintenance activities. This maintenance regime will not be increased unless we perceive there to be an increased flood risk.”
EA should not have to make this choice. They are responsible for both flood control and conservation and should be funded by DEFRA to adequately discharge their responsibilities for both.
Downstream
All of this only pushes the problem into the hands of the Canal and River Trust, who have jurisdiction over the river channel and river banks downstream and the land either side of the trash screens.
Luckily, January 2022 will see a clean-up of the River Brent inlet downstream of the screen as part of Canal and River Trust’s £85k winter works programme - the first major investment in the area around the east marsh at the Welsh Harp in decades - but it will only scratch the surface of the problem. A visit to the Silk Stream recently revealed a huge raft of plastic bottles and polystyrene wedged in the river channel only metres from the protected north marsh, and large areas of wet woodland at both sites remains littered with debris and sewage.
What next?
EA can inform us of their small victories, but it is abundantly clear much more needs to be done.
Regarding plastic pollution, we urge EA to take more responsibility for clearing debris congestion at the River Brent and Silk Stream trash screens. A focus on flood control upstream cannot be at the expense of poor conservation practice and localised flooding at the screens themselves. This only sees debris washed up and over into the river channel downstream, and onto upstream riverbanks, both of which pass an ecological problem onto others and threaten the habitats of a SSSI.
We urge it to work more robustly with councils in the catchment to address issues of upstream fly-tipping into river channels and illegal dumping of oils and diesel into surface drains. There are known hot-spots; one is just yards from the River Brent trash screen on the Priestley Way bridge.
With regard to water quality, we urge it to force Thames Water to ramp up their tracking of polluting outfalls and the rectifying of misconnections in line with commissioned recommendations. Phosphate and ammonia loads, toxic sediment and oxygen depletion kill life in the waters of the Welsh Harp. They are a fundamental threat to the health of the SSSI. Five of the worst outfalls in the catchment are immediately north of the Silk Stream trash screen.
Looking ahead, we call for legislation to incorporate compulsory drainage checks at the point of sale of a property by 2025, and on new-builds at the point of build completion.
We urge EA to improve the broader urban runoff crisis not just in the better maintenance of outfall interceptors, or working with Thames Water and Highways England on better mitigation measures, but in insisting on more green infrastructure.
Trees, plants and soil naturally remove pollutants from water. Concrete, pavements, roads and driveways do not; they act as hard surfaces, fast-tracking polluted surface water into rivers.
We urge EA to push for less concrete and more soil; more ground absorbency, less impervious surfaces; to engage as passionately as possible with private developers - such as those at Hendon Waterside - and local councils, to shape future strategic plans for development that encompass these aims.
And we urge DEFRA to either fund and resource the EA to give it some proper teeth, or disband it and come up with an alternative that is fully fit for purpose. Otherwise the Welsh Harp will continue to endure the damage done by the inadequate local stewardship of water quality and inflowing debris.
We continue to press for information and action.