Round Table Teases Out Lessons Learned from SUDS in Scotland

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Special Report


Round Table Panel Members

Dr Scott Arthur, Heriot-Watt UniversityChair:
Dr Scott Arthur,
Senior Lecturer, Director of Studies, Heriot-Watt University

Brian Jones, Hydro InternationalBrian Jones,
Regional Manager,
Hydro International

Phil Collins, Hydro InternationalPhil Collins,
Sales & Marketing Manager, Hydro International

Ron Jack, Walker Group (Scotland) LtdRon Jack,
Technical Manager,
Walker Group (Scotland) Ltd

Doug Buchan, Scottish WaterDoug Buchan,
SUDS Co-ordinator,
Scottish Water

John Millar, West Lothian CouncilJohn Millar,
West Lothian Council

Neil McLean, MWH, CIWEMNeil McLean, Senior Environmental Scientist, MWH, CIWEM

Jane Shields, Living Water Ecosystems LtdJane Shields,
Director / Flood Risk Manager, Living Water Ecosystems Ltd

Chris Pittner, WSPChris Pittner,
Technical Director,

Andy Hemingway, SEPAAndrew Hemingway,
Technical Secretary to the SUDS Working Party,

Kenneth MacDougall, EnvirocentreKenneth MacDougall,
Projects Director,

Andy Bogle,
Professional Officer,
City of Edinburgh Council

Ged Mitchell, Bear ScotlandGed Mitchell,
Senior Environmental Engineer,
Bear Scotland

Judith Tracey, SEPAJudith Tracey,
Head of Managing Flood Risk Team,
Scottish Government

Drew Hill,
Senior Environmental Engineer,
Transport Scotland

Martin Findlay, Cala HomesMartin Findlay,
Engineering Manager,
Cala Homes

Round Table Teases Out Lessons Learned from SUDS in Scotland

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SCOTLAND has led the way in making the design and installation of Sustainable Drainage Systems (SUDS) compulsory, supported by legislation first established 10 years ago.

So Engineering Nature’s Way brought together an expert panel of practitioners closely involved in SUDS approval, design, implementation and policy in Scotland to ask what has made SUDS successful?  What can be learned from the challenges encountered? It turned out to be a passionate debate.

Chaired by leading academic Dr Scott Arthur, Senior Lecturer and Director of Studies at Heriot-Watt University, the panel explored the findings of the SUDS in Scotland – Experience and Opportunity survey during a lively and thought-provoking discussion.


Scottish SUDS Survey

The survey was commissioned for Engineering Nature’s Way by sustainable drainage specialists Hydro International who hosted the Round Table Event on November 7 in Edinburgh.  The initiative was conducted in association with CIWEM and British Water.

According to the survey, practitioners involved in SUDS design and implementation in Scotland believe they have been overwhelmingly successful.   Discussion between 18 panel members, many of whom have contributed to the influential Scottish SUDS Working Party, revealed the key challenges and barriers to future progress in Scotland.  It also provided vital clues for the successful implementation of SUDS in the rest of the UK.



The Debate


What Does Success Look Like?

Drew Hill, Senior Environmental Engineer, Transport Scotland, kicked off the debate by asking what does success look like and how is it measured?  Neil McLean, MWH stressed that Scotland had not been 100% successful with SUDS.

“There have been some success stories and some failures as well.  This process was always going to be evolutionary; it wasn’t going to happen overnight.”

The panel noted that in Scotland water quality had been the principle focus of developing legislation and regulation, whilst in England and Wales the emphasis has been on controlling flooding and water quantity.

“Scotland in general is much further ahead on implementation of SUDS and other licensing and good practice,” said Jane Shields, Partner/Flood Risk Manager of Living Water Ecosystems Limited, adding she felt the Scottish Environmental Protection Agency (SEPA) were often more open to trialling new ideas.

At the same time tensions over who takes responsibility for adopting and maintaining surface water drainage features are presenting a barrier to progress.  The discussion exposed how ‘disconnects’ between Scottish Water and local authorities in Scotland are leaving many systems in unadopted ‘limbo’ and sometimes leaving householders to pick up additional estate management charges.




Adoption of SUDS

“I think what is really disappointing is that adoption has always been an issue for SUDS,” said John Millar, Flood Risk Management Officer of West Lothian Council. We’ve had SUDS since 1995/96… and there is still an issue of adoption by local authorities or by Scottish Water.  I think what is the most disappointing thing is that people who are buying new houses are having to pay over and above their council tax and their sewerage charges to maintain part or the whole of the drainage system and I think that’s very poor.”

Ron Jack, Technical Manager of Walker Group (Scotland) Ltd, commented: “I don’t think there was any consideration given to how maintenance was going to be funded…  To that extent what has happened is that both local authorities and Scottish Water have been reluctant to take on this additional burden without any funding, so developers have had to take on alternative means of maintaining these systems and that’s generally come down to the fact that we have to make estate management arrangements.  There is a whole joined-up process that is just not really there.”

Scottish Water’s SUDS Coordinator Doug Buchan responded by pointing out that many legacy SUDS schemes had been designed and built at a time there was a lack of knowledge and experience of SUDS.  Scottish Water cannot adopt SUDS that do not meet their standards.  The water company had conducted a project with the University of Abertay to show that SUDS were not being constructed according to the design specification.  80% had no, or the incorrect vortex flow control device installed, for example.


Evidence and Monitoring

The comment raised the issue that very little ongoing monitoring of the performance of SUDS features has been undertaken.  “We put these systems in, but who monitors them at the end of the day?” asked Andy Bogle, Professional Officer from Edinburgh City Council.

Andy Hemingway, Scottish SUDS Working Party Coordinator for Scottish Environmental Protection Agency (SEPA) stressed that it would welcome a project to assess whether existing SUDS systems have been constructed according to design and whether they are being maintained.   “We need some hard facts about this; how effective these systems are, and how are they being maintained.   SEPA’s Director of Operations has written to the Scottish Government about the effectiveness of SUDS implementation and how the regulatory system is working, because we have got concerns about it.”

John Millar, West Lothian Council, added that there may also be a question around inspecting SUDS systems during construction to ensure they are being installed according to the design specification.

Andy Bogle, Professional Officer, Edinburgh City Council, pointed out that the skills and resources needed to maintain SUDS may be lacking:  “Councils have been maintaining roads and gullies for hundreds of years; now we are asking them to maintain permeable paving that has to be cleaned and brushed twice a year and you get blank looks; they don’t have the facilities, the machinery to do that.  It’s the same with swales; they don’t have the expertise and the machinery to do that. “

Drew Hill, Senior Environmental Engineer, Transport Scotland pointed outthe challenges around shared ownership of SUDS and the requirement for adoption.  “On the Transport Scotland side …we don’t require adoption and we maintain the systems because they are there for a reason; they are protecting the asset… So we design SUDS and we make sure they perform.  So I wonder if there is a disconnect between the various organisations involved in delivering SUDS and who actually owns them.”


Scottish Water’s Responsibilities

Judith Tracey, Head of Managing Flood Risk Team of Scottish Government, asked whether there was always an assumption that Scottish Water should adopt.  Neil McLean, Environmental Scientist for MWH responded:

“If we can place the onus upon Scottish Water to accept the SUDS systems as the water authority then we should be doing that and not look to people who live in houses, who don’t know about SUDS and sewerage systems and reed beds…  I’m not saying that under every circumstance.. but where there is an opportunity for an authority to exist in perpetuity as Scottish Water will, as local authorities will, then we should be placing the onus on them… and not on a residents association, for example.”

Following a frank exchange of views between panellists, Judith Tracey added: “Scottish Water is a utility company; that’s what it does.  If what we are looking for is a variety of different kinds of SUDS, is it reasonable to expect a utility company to be responsible for maintaining a wetland?  I’m just asking the question – it’s not their expertise.”

Chair of the debate Dr Scott Arthur, Senior Lecturer / Director of Studies for Heriot-Watt University, pointed out that householders do not really realise the divide between the responsibilities.  “I guess if I was a householder sitting in this discussion, it would  be quite frustrating to see how people are ping-ponging back and forward about. The division of responsibility between Scottish Water, Local Authorities and developers may be clear to us, but it isn’t clear to the public.”


Challenges for Good Design

Dr Arthur, Senior Lecturer / Director of Studies for Heriot-Watt University, expressed the view that the type of SUDS that Scottish Water has been willing to adopt has shaped the way SUDS in Scotland have developed.  However, the arrival of Water Sensitive Urban Design in Scotland had potentially opened up new possibilities.  “Most of the SUDS I have seen look absolutely fantastic and I do feel they add value for communities, nonetheless challenges remain. We are likely to be more successful in implementing SUDS with the broader Green Infrastructure agenda… Systems that are well designed and well maintained can deliver a lot of the amenity values we aspire to.  ”

Jane Shields, Partner/Flood Risk Manager for Living Water Ecosystems suggested that good SUDS design should incorporate a more integrated approach to water management on a site, that included recycling and reusing water, as well as developing opportunities to create biodiversity and habitats.  However, several panellists expressed the view that restrictions in regulation and adoption of SUDS in Scotland were limiting design choices.

Dr Kenneth MacDougall, Projects Director of Envirocentre added: “As was reflected in the survey findings, we are quite limited in what we can do as designers, looking at what else you can do with SUDS to work it into the landscape, the Green Infrastructure approach…. We are looking at a site where we have got effective natural wetlands and the option for the development is that we are going to have to dig that out and put a pond in, which is counterintuitive…  … You can’t expect developers to have to maintain a site.  What they do is they come on to a site, they develop it and they move onto the next one, so you have to recognise that”.

Chris Pittner, Technical Director of WSP agreed:  I think that’s a good point.  We can design things that do create habitat, do create biodiversity … but what we tend to find is that we design these things and then they won’t be adopted by Scottish Water because they don’t comply with Sewers for Scotland… in terms of your one in three batters, your maintenance track, and a kiddie proof fence around it and that detracts from what you are actually trying to achieve at the end of the day.”



In the survey 61% of respondents agreed that affordability presented a barrier to design and implementation on new developments.  From the chair, Dr Arthur, Senior Lecturer / Director of Studies for Heriot-Watt University, questioned whether design constraints were limiting the amenity value of surface water drainage.  “Will developers still try to squeeze as many houses on these sites as possible and always try to keep everything below ground?

Martin Findlay, Engineering Manager of Cala Homes, respondedUltimately coming from a housebuilding perspective that’s obviously what we do, because we are here to make money at the end of the day.  But we do incorporate SUDS at a very early stage, when we are preparing the layout and we know what we have to do with regard to Scottish Water’s standards. “


Retrofitting SUDS

According to the survey, the vast majority of practitioners in Scotland believe more could be done to retrofit SUDS.    “I think there’s a big question mark about whether we are delivering good water quality… There’s a lot more that could be done in terms of retrofitting, particularly industrial estates which are the main causes of water quality downgrades.  It boils down to the usual issue of… lack of maintenance of existing SUDS.”

Ged Mitchell, Environmental Engineer for Bear Scotland, added “The report says that 81% of people say retrofitting is not happening to a great extent and that feeds the water quality issue in Scotland.  I personally don’t see retrofitting and I wonder if the Local Authorities have got a programme, I wonder if SEPA are looking at retrofitting.  I don’t see it.”

Dr Arthur pointed to industrial estates where site constraints prevented implementation of SUDS.  Andy Hemingway, Scottish SUDS Working Party Coordinator for SEPA added:  “Scottish Water along with SEPA have identified the most polluting industrial estates and the most appropriate ones for retrofitting…  [With limited resources] there’s quite an emphasis on going into the individual units and making sure they are following best practice. … We have to go out there and get on the ground to make them aware of what they are doing.  Nine times out of ten they are not aware where the drainage goes; there are a number of surface water action plans for the most polluting industrial estates.”

“We accept that in a lot of cases there isn’t space to put in traditional SUDS pond or basin, which is why in our guidance we say for retrofitting … we’ll accept proprietary systems.”

Dr Arthur, Senior Lecturer / Director of Studies for Heriot-Watt University, commented that it was likely that Scotland would see more retrofitting ‘fairly soon’, in response of a greater emphasis on controlling flood risk.


Design Freedom and Proprietary Systems

The limitations on using proprietary systems were raised by several panel members as a barrier to successful SUDS design as well as effective ongoing maintenance.  Brian Jones, Regional Manager of Hydro International pointed out that in England and Wales the market for Hydro’s Downstream Defender® Vortex Separator had been growing ‘exponentially’, while in Scotland strict limitations were imposed on developers.

“Our products are often best used in conjunction with other things,” he pointed out. “I could offer you the example of Hopwood Services where we have a Downstream Defender® in a treatment train of ponds; HR Walllingford monitored this and SEPA have the report. SEPA’s in house SUDS newsletter “Permeate” ran a two page article on Hopwood Services.  They were monitoring 99.7% reduction in total suspended solids, a huge reduction in phosphates, nitrates, hydrocarbons; we were looking at a really exceptional SUDS system.  Unfortunately, although the report went through this in great detail and published how great the results were, they neglected to mention that there was a Downstream Defender® in the beginning taking out the worst of the pollutants.”

Chris Pittner, Technical Director of WSP commented: “Normally we don’t use proprietary systems, the main reason being that if we are going through the planning process, or submitting a CAR license if we put the proprietary system on that it would probably be rejected by SEPA.  So that’s the real reason why we don’t tend to specify them.”

Ron Jack, Technical Manager for Walker Group (Scotland) Ltd pointed out that in Scotland SEPA do not accept proprietary systems as a level of treatment.  “If you put in a Downstream Defender®, you still have to put in a level of treatment as well.”



What defines a level of Treatment?

Phil Collins, National Sales and Marketing Manager for Hydro International added “I think one important question we have to ask is what is defined as a level of treatment.  That’s fundamental in terms of what types of SUDS can be used in any type of application.  Until that is defined in terms of some sort of sediment loading rate, for example … we are in this kind of limbo land of what is good for a level of treatment.  Tell me what a level of treatment is: that’s a real fundamental.”

“I tend to agree,” said Dr Arthur, Senior Lecturer / Director of Studies for Heriot-Watt University, “Perhaps there should be more focus on discharge standards or suspended solid removal rate.  Just bolting together elements of a treatment train might not always give you the answer you want, and that answer might not always be that efficient.”

Ron Jack, Technical Manager for Walker Group (Scotland) Ltd added that including biodiversity in the SUDS triangle was severely restricting design opportunities.  Vortex separators were regarded as pre-treatment as a result of guidance from the CIRIA SUDS manual.  However there was growing information to validate their performance.

Phil Collins added: “The SUDS Manual is being reviewed and anybody who has any involvement in that needs to take a look at what is a level of treatment.  You can have a really well-designed SUDS but it can fail on construction and when you take that back to the SUDS manual and look into a swale or a pond being defined as a level of treatment.  How well will that perform if it hasn’t been constructed properly?

“If the demands are being put out there for an integration of proprietary and soft systems, then we should be looking closely at how they correlate together.  We have got great exemplar of where a Downstream Defender® has been put upstream of a sedimentation forebay, and also to improve the efficiency of the pond itself.  That’s not just with our products, it’s happening around the world…   based on facts and evidence. ..You have a great opportunity to rewrite the SUDS manual to perhaps address that in terms of all SUDS, not just proprietary devices.”

Doug Buchan, SUDS Coordinator for Scottish Water added:
“The SUDS Manual was a good start and gave everyone an easy rule of thumb.  You needed one, two, three levels of treatment.  But so much has gone on.  With experience, the whole principle is probably questionable at best …There’s a lot of innovation out there at the moment, we’d like to consider them; we’d like to have them recognised as an acceptable solution for water quality.

“Some sites will be quite constrained, small sites… and struggling with land where we can’t put in ponds or basins, swales or porous pavement – the local authority would not take them on.  Before the CAR regulations, these products were going in and seen as protecting the water environment.   We have the experience of academic testing, whereas no two swales are the same; no two basins are the same, but we use principles that assume they are.  With the experience we have gained we have become a bit smarter now, and I think this is where the key change could be to drive even more success moving forward.  We are still protecting the environment because that is what everybody wants.”

Andy Hemingway, Scottish SUDS Working Party Coordinator for SEPA added that SEPA’s concerns were not to do with the effectiveness of proprietary systems, but with long-term maintenance and the fear that underground systems are forgotten about and not maintained.

Phil Collins, National Sales & Marketing Manager for Hydro International, pointed out that manufacturers have GIS data about the location of every installed system.  “The question has to be asked, is there now a time for a national register to map where these assets are – even understand the numbers installed and how they are performing.“


Concluding Remarks

Closing the debate, Dr Arthur, Senior Lecturer / Director of Studies for Heriot-Watt University, said:

“People outside Scotland do think we have got the ideal solution, but it’s clear that although we have been 99.9% successful, that last fraction of a percent is pretty hard to achieve.

“There will be opportunities with Sewers For Scotland 3 and also to follow what’s happening in England, especially with proprietary SUDS where appropriate. England are going to be leading with that aspect and perhaps that experience may help inform the debate in Scotland.

“I think we all welcome the survey; it has stimulated a lot of debate here.”



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Kenny Birch says:

All of the discussion seemed useful and constructive–but–I see the ‘U’ was missing, ”Urban” , in all the discussion. Planning departments and SEPA ,currently always ask for Sustainable Urban Drainage Systems–strange really in country properties–which have for the most part had Sustainable RURAL Drainage Systems for centuries. In my experience, it it the Local Authorities who have had the most severe adverse impact on drainage over many years, by insisting on rainwater going to mains drainage, for the best part of a century- and SEPA, who are totally set against sustainable Sewage Systems–despite their own record of leaks and discharges of untreated sewage.
I have been involved with projects where sustainable rainwater was prohibited, and others where it was compulsory, and in projects where pumped drainage was a requirement, and on the next along the same street a soakaway was acceptable.
It is difficult to reconcile the good intentions and ideas expressed at this conference with the variable practices inflicted on developers.

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