94 Highway drainage – the next pollution scandal?
Martin Osborne
Water industry strategic advisor, asset planner and drainage expert Winner of the 2023 WaPUG Prize for contributions to the development of urban drainage practice
Some of you urban drainage nerds will recognise the picture as being from the front cover of “The Wallingford Procedure for design and analysis of urban storm drainage†published in 1981.? It was just three years later that I started to work with many of the team who created it.
In the news
Pollution from highway drainage is starting to be a big discussion point.? There have been articles in the press and on television and radio.? There is a Planet Possible podcast on pollution from highway drainage and what National Highways (the body responsible for motorways and major roads in England) and the Environment Agency are going to do about it.? CIWEM (The Chartered Institute of Water and Environmental Management) has a blog post on the issue and is soon to publish a document, describing the problem, assessing the scale of it, and presenting an array of possible solutions. The report – ‘Road runoff and the water environment’ – will explain, “how the regulatory framework and the regulators have overlooked this problem, conveniently side-stepping the requirement to require permits for these discharges and avoiding calls to measure the extent of the problemâ€.
Common to a lot of these articles is the wonderful campaigner Jo Bradley who is researching and publicising the problem.
But, has it always been a problem and if so why has nothing been done about it?
The law
Criminal law
Remember that I am not a lawyer and my explanation of the law is likely to be simplistic or even wrong.? However, I refreshed my understanding of the law relating to pollution from highway drainage by consulting “Water pollution and water quality law†by Howarth and McGillivray.? I would love to recommend that you buy a copy, but at over 1200 pages and over ￡100 it is a bit of a niche publication.?
The background is that highway drainage was originally assumed not to be a pollution risk.
The basic offence of pollution under criminal law is “to cause or knowingly permit poisonous, noxious, or polluting matter or any solid waste to enter any controlled watersâ€.? There are two key defences to this (that is situations where such a discharge is not illegal).
- If a discharge permit has been issued and the discharge is compliant with the conditions of the permit.
- If the discharge is made from a highway drain by a highway authority.? Unless the discharge is in contravention of a prohibition.
The first of these is how discharges from sewerage system overflows and treatment works are regulated.? The second is a get out clause for local and national highway authorities.
A prohibition can be issued by the environmental regulator if the discharge is causing impact on the watercourse and the highway authority then has to cease the discharge or comply with the conditions of a imposed permit.? I assume that they will be given a reasonable time to make alternative arrangements rather than just blocking the drain and flooding the road.
There is however a confusion in that water companies can reach agreement to discharge surface water to highway drains and vice versa to discharge highway drainage to surface water sewers.? The gotcha here is that if a water company knowingly permits highway drainage to discharge from a surface water sewer, then it would appear not to be able to claim the get out for a highway drain.? Maybe water companies should start to get worried.
So, most direct discharges of highway drainage are exempt from control unless they are shown to be causing significant pollution and a prohibition is issued.
Civil law
As well as the criminal law, highway drainage discharges could be subject to the civil law where someone impacted by the discharge can sue for damages.? This could include owners of the land that the water course passes through.? It is necessary to show that some damage has been suffered but that could include public nuisance or impact on use of the land or the watercourse.
领英推è
There have been some successful cases of highway authorities being sued for pollution of a watercourse but I think that has mostly been due to a one off incident rather than routine storm runoff.
Earlier work
Although the historical assumption was that highway runoff was not polluting, there had been research into what pollutants it did contain.? Much of this was in the USA as part of the Nationwide Urban Runoff Program (NURP) but there was also work in the UK, particularly at Middlesex Polytechnic (now Middlesex University).
In 1993 this led CIRIA to commission a project to produce guidance on “The control of pollution from highway drainageâ€.? The work was carried out by Martin Luker and Keith Montague.? Thirty years ago, almost to the day, I was brought in by CIRIA to edit their final report and to add a chapter on assessing pollutant risk.? This led to the development of a simple assessment tool.
The tool considered the following aspects:
- The area of road draining to the watercourse
- The expected concentration of a range of pollutants depending on the traffic flow
- The dilution of the runoff in the watercourse
- The standards for water that could be treated to be drinking water
It would have been better to consider the pollutant concentrations that would cause environmental impact, but that information was hard to find.
We reduced down the list of pollutants that could be considered; we ignored lead as leaded petrol was going out of use, there was not enough data on hydrocarbons, PFAS or other organics to make a reliable model, no-one had even heard of micro-plastics.? For the rest of the pollutants we looked at which would first breach the standard and came found this would be copper and zinc.? These were therefore used as indicator pollutants for highway drainage being a problem.
The idea of the assessment tool was that it could either be applied to the length of major road draining to a single outfall or to all of the local roads draining to a watercourse through systems and outfalls unknown.? Each class of road would have its own pollutant concentration.
The publication of the CIRIA report led to a lot of interest in highway drainage and a substantial programme of monitoring drainage discharges from major roads.? The risk assessment tool was updated by the Highways Agency and called HAWRAT and then HEWRAT.? The organisation is now called National Highways but the acronym NHWRAT doesn’t work (at least in English).?
The podcast mentioned at the top of this blog has an excellent interview with National Highways talking about how much further they still had to go to deal with all of the identified risks.
The application of these tools seems to have been just to individual outfalls rather than to the road system as a whole.? I am not aware of any local authority using the tool to assess the local roads, but I stand to be corrected if you know better.? The Defra guidance for drawing up Surface Water Management Plans for flood risk does include a requirement for local authorities to “have an understanding of where surface water may impact water quality in receiving watercourses (either directly through surface water runoff, or indirectly via combined sewer overflows).â€
The future
Pollution from highway drainage is now coming up the agenda (only 30 years after that pioneering CIRIA report) and government is aware that action might be needed.? But what can it do?
Government could remove the exemption of highway drainage from pollution law.? This would mean that all highway drainage outfalls would need a discharge permit.? This should also apply to surface water sewers that carried highway drainage.
Obviously that is a massive task to permit all of the outfalls, but we faced a similar task with combined sewer overflows 30 years ago.? The solution then was “deemed consents†where a spreadsheet listing all known discharges was submitted to the environmental regulator and they issued temporary permits with timetables to assess each one depending on its significance.? There was also a requirement that any previously unknown outfalls were notified to the regulator as soon as they were found.? There are a lot more highway drainage outfalls than sewer overflows but the assessment of impact is simpler and we have the advantage of powerful GIS tools and even AI.
I think that it could be done; but is there the will?
Chair Of The Board Of Directors at CAVERSHAM BRIDGE NEWS LIMITED
11 个月A concise summary of a very complex issue Martin. We began to explore issues relating to non-agricultural diffuse pollution from around the time of the creation of the National Rivers Authority in 1989. Working with Brian D'Arcy from the then Forth Rivers Board (later SEPA) we highlighted the impact of road drainage and the techniques which could be used to reduce its impact. This was one of the drivers for the development of the SuDS approach to drainage. I have always believed we should focus on better design for new construction (SuDS), removing pollutants at source (eg lead weights used to balance car wheels) and targeted retrofitting at outfalls which have a proven adverse impact. Nick Orman's post makes a very sensible suggestion about focussing on the most heavily trafficked roads. Having been involved in efforts to regulate surface water discharges in the past, I believe the costs involved in permitting or registering outfalls would be large, and without monitoring and enforcement, a waste of resources. And who believes the regulators will have the resources to do any of this?
AECOM Water Eng. Senior Project Manager (seconded to Environment Agency)
11 个月As recommended - 'Water Pollution and Water Quality Law'
Technical Director at HR Wallingford
11 个月I think the government and EA record on environment protection and treating pollution (and monitoring of it) speaks for itself. I suspect 'Highways' can relax for many years to come.
Specialist in Urban Drainage planing, design, rehabilitation and maintenance. Winner of the 2024 WaPUG Prize from CIWEM's Urban Drainage Group for a significant contribution in the development of Urban Drainage.
11 个月Helpful article as ever Martin, the number of outfalls is clearly going to be an issue, and we must also remember that local highway authorities have been starved of funds for the last 14 years. That said doing noting is not an option, but we could prioritise. Fortunately work carried out - some at WRc - has found that the pollution disproportionately comes from the most heavily trafficked roads. So why not start with trunk roads and the most heavily trafficked local roads? The two locations highlighted in the press by Jo Bradley and CHARLOTTE HITCHMOUGH were both from motorways so trunk roads would be a good place to start. Other roads could be brought in on an exception basis where problems are highlighted in the receiving watercourse.
Chartered water and environmental manager
11 个月Who’s rainwater is it? Is it a waste product or a resource? Does the owner need to pay for disposal (or discharge to the environment) or sell it as a resource? Perhaps time to rethink how we manage rainwater in communities? Thanks Martin for writing another interesting and topical blog!