Official Report: Minutes of Evidence

The Chairperson (Mr Martin): I welcome Simon Richardson, Stuart Wightman and Marie-Louise Wise from the Department for Infrastructure. I need members' agreement that the evidence session be reported by Hansard.

The Chairperson (Mr Martin): You have up to 10 minutes in which to make a brief opening statement. Every statement that I have heard from the Department has been shorter than that. Perhaps I should congratulate you on that, although it puts me under pressure to get my questions ready for you. After the briefing, you can expect members to ask questions.

Simon, the floor is yours.

Mr Simon Richardson (Department for Infrastructure): Thank you, Chair. We may take our full 10 minutes, if you do not mind.

The Chairperson (Mr Martin): How refreshing. [Laughter.]

Mr Boylan: Do not say that, Simon.

Mr Richardson: Thank you, Chair and members. Good morning. We have two sessions here this morning. The first is about sustainable drainage systems (SuDS) and our ongoing consultation on SuDS in new housing developments. Stuart is the lead on that project, and he will take us through the presentation in the first session. The second is on a consultation that we did earlier this year on the living with water in Derry/Londonderry plan. Marie-Louise is the lead on that project, and she will take us through the second session to give us an update on the responses that we have had.

There is one key link between the sessions, and we welcome the fact that they are happening back to back, because there will be issues that are relevant to both. The common theme is that we are trying to promote nature-based sustainable drainage systems. We are doing that in two ways: by retrofitting existing drainage systems, whereby we try to slow the flow of water on the surface; and by ensuring that any new builds are built with nature-based drainage solutions in mind. There is no point in building new developments in the old way and then having to retrofit them, so that is what we are trying to do.

That leads us into our first session, which is on the development of our policy on sustainable drainage systems in new developments. I will pass over to Stuart. You have the slides in your packs, but we will go through the slide presentation online and take questions afterwards.

Mr Stuart Wightman (Department for Infrastructure): Thanks, Simon. Good morning, everyone. Chair, you will remember my evidence from when I came to the Committee with Alison Clydesdale, director of water and drainage policy, to talk about the Water, Sustainable Drainage and Flood Management Bill. I mentioned the public consultation that day — you guys had just received the consultation document — so I thought that it would be useful to come along and run through its contents to inform members. As Simon said, we can cover questions at the end.

It is important to provide some context. There is the Bill, which you are scrutinising, and how the consultation fits in with it. I will also give an overview of the parts of the document that deal with how drainage systems are currently dealt with in new developments. I will then move on to where we want to go with the policy aim. That is what we are consulting on.

First, the Bill. Clauses 2 and 3 deal with the enabling powers. They enable the Department to make regulations down the line. The Committee will be considering the appropriateness of all the powers in the Bill. At this stage, we are talking about a regulatory regime for the SuDS arrangements, but we do not have all the answers for what the SuDS approval body will be, where the funding will come from or who will undertake the maintenance operation. That is part of the consultation, and there will be further consultations down the line. Rather than wait until the Bill completes its passage through the Assembly before starting to look at the detailed policy, it is expedient to develop the two things in tandem. Early in the next mandate, we will probably be in a position to lay the regulations. That obviously depends on how fast the Bill goes through the Assembly, because we need the powers to make the regulations. The consultation is the first step in taking forward the policy for the regs.

When it comes to the existing provision, there are two scenarios in new housing developments. There is a surface water drainage system that collects rainfall, and that rainfall goes into either a river or a receiving sewer. We touched on some of that in our previous evidence session. Depending on which scenario it is, there are two relevant pieces of legislation. The first of those is the Drainage (Northern Ireland) Order 1973, under which my colleagues in DFI Rivers have the power to restrict discharges to what we call greenfield run-off in order to protect a river. That encourages developers to try to attenuate those flows on-site in order to meet that level of discharge. Similarly, if the proposal is to connect to the existing sewer network, that is governed by the Water and Sewerage Services (Northern Ireland) Order 2006. Northern Ireland Water (NIW) can require the developer to slow the flow of water into the sewer in order to protect the sewerage network. Those two pieces of legislation encourage SuDS.

At the moment, those are hard SuDS, because they can be adopted. Hard SuDS involve bigger pipes and tanks; sewers that are below ground. What does that look like? You will see some diagrams in the consultation document. Where there is a new development, there will be a traditional pipe network that collects storm water from roofs and driveways. There will be a tank or a larger sewer at the end of the pipe, which attenuates the flow before it goes into a river or a receiving sewer. The difference between soft SuDS and hard SuDS is that with hard SuDS there will be a continuing flow of water when it rains into the river or the sewer. Where there is a heavier flow, it will start to back up and attenuate.

Conversely, although there are no arrangements for the approval and adoption of soft SuDS, you can have a soft SuDS system. I know that the Committee will visit a site in Antrim in a few weeks' time that is a good example of developers going out at their own risk to build a soft SuDS, which brings a lot more environmental benefits. The challenge with that is that you need a lot of space. As you can see in the soft SuDS diagram, a couple of houses are shadowed out because the developer could potentially lose a bit of land on which to build houses, because of the size of those installations. One of the challenges is that, because of its size, the installation tends to be at the back of the development, and it tends to be fenced off for health and safety reasons. It can be difficult to integrate such features into a development.

By way of a comparison between the two systems, let me draw your attention to the graphic that illustrates the four pillars of sustainable drainage systems: water quality, water quantity, amenity and biodiversity. Hard SuDS only partially deal with water quantity. Although they slow the water down, all the water still ends up in the receiving river or sewer. Soft SuDS, on the other hand, allow for filtration and evaporation. If it is designed correctly, a soft SuDS installation will hold the water. It is only when it is overwhelmed that the water will start to pass through. There is a clear benefit there. Furthermore, soft SuDS provide water quality benefits, because you get filtration of pollutants, particularly when the water has a chance to sit and slowly pass through the ground. There are also amenity place-making benefits and biodiversity benefits.

Our policy aim is what we call a "SuDS management train". Although the end-of-pipe soft SuDS, such as the example that you will see in Antrim, are great, we want SuDS at every level of a development. The idea is that you do not just do it and have one big pond at the end, but that you have SuDS at property level, street level and development level. One of the challenges for the industry is that there is a 10% target for green space in developments, but a SuDS does not count towards that green space for a developer. That is a challenge for developers, so we are looking at that. When it is dry, that green space can be used as an amenity, but when it rains, it can store water temporarily.

I will offer the analogy of a champagne fountain, which you can see on the slide. The top glass of the fountain is the property. When it fills up, the water goes to street level and then to the development level. If that is done right, it will only be during a heavy rainfall event that any water leaves the site. That is what we are trying to do. We are trying to manage rainwater at source.

The next slide shows you what that looks like. In the first instance, you would possibly have permeable paving on driveways and water butts. You might, then, move to swales along the edge of the street. Instead of having a pipe network, you would replace that with water on the surface. You would still have detention ponds at the end, but those would be much smaller. You would not be losing any real estate because you would be incorporating the systems into the amenity spaces of developments. As you can see from the slide, that approach is similar to others, but it is not end-of-pipe based, because we are integrating the SuDS at every level of the development.

What do they look like? There are some examples on the slide that you can see. You can have a planted water butt at property level and permeable paving. The middle picture on the slide, showing the marker post, is of a verge rain garden, and there are pictures of two grassed swales at street level on either side of that. There is a detention basin at the bottom of the slide, which would be more at the end of the development. There are different levels, and there will not be a one-size-fits-all solution. Obviously, not all developments are perfectly flat. The topography will dictate that. We recognise that it will not all be soft SuDS: there will also be a place for hard SuDS, depending on the site's topography. There is a combination, and it is about having the menu that developers can pick from.

I am not going to go through the consultation questions in detail. We can pick those up during questions if you want. The consultation document contained eight questions, and you can see the types of questions. We do not have the answers yet. As I said at the start, we are asking questions around a SuDS approval body, who should be responsible for the maintenance of SuDS and so on. That will inform the policy down the line.

We are in the middle of the consultation process. That closes just before Christmas — 19 December — and will hopefully give us the buy-in to the SuDS management train approach. If that is the preferred option, the next step will be to review the responses in the new year, and we said that we would come back to the Committee to give you an overview of that. The next stage will be to move towards developing the best and most appropriate framework, which will involve getting into the detail at the next consultation about SuDS approval and around maintenance and what those arrangements might look like. Ultimately, that will inform the draft regulations.

Apologies; the writing on the slide is quite small. We are only three months in, so we are at the start of a 30-month journey. At the end of the journey, which will probably be just into the start of the next mandate, we will be hoping to make these regulations. They are draft affirmative, so they will have to be laid by resolution of the Assembly. They are not negative resolution, so they will have a chance to be discussed in the Assembly Chamber. That is the plan, and, as I said, there are two tiers there. There is a tier on policy and legislation, and, in the bottom tier, which is in dark blue, we recognise that it is not a case of not having a SuDS approval body one day and having one the next day. We realise that we will have to start to develop shadow arrangements and possibly phase in SuDS.

That was quick, and I probably did not take up all my time. I will take any questions.

The Chairperson (Mr Martin): Well done, Stuart. That is great. I am pretty sure that I am a visual learner, so I kind of liked your diagrams and graphics. They were useful.

I will start with the slides on existing drainage provision. I looked at the slide with the graphic for an end-of-pipe hard SuDS and compared it with the next one for an end-of-pipe soft SuDS, and my thinking was, "Why would a developer give up two houses for a large attenuation pond?". On the slides entitled "The Policy Aim", the houses are back and the attenuation pond is slightly smaller. I know that this is not scientific, but is it your belief that the additional things that we see, such as permeable paving, water butts, swales and gullies, will do enough to offset the smaller attenuation pond that allows two additional houses to be built there?

Mr Wightman: Yes, it is. What I did not get into in detail is the fact that, in the SuDS management train, one of the first principles is prevention. So, when you are designing the site, you are trying to minimise the amount of permeable surfaces. That is done right at the start by, for example, making sure that you select the right materials when you are doing surfacing. The idea is that the volume that you lose by going to a smaller detention pond will be catered for by property-level and street-level interventions throughout the development.

Mr Richardson: It will depend on the geography of the site. We cannot say that it will happen in every case. Every site will stand or fall on its merits. All of the tools are still in the box. We are not doing away with the hard SuDS that we talked about at the start. If a soft SuDS is not available to us, a hard SuDS is still an option for the developer.

It is something that we are learning. We are trying to learn with the developers and let them bring their issues to us. It was very useful for us to go to the Antrim site and learn from what has been done there. We had a conference back in June; we invited some of the developers to listen to our thoughts. That has generated a lot of interaction, which has been very beneficial for us. We intend to continue that throughout the consultation process.

Your question is right, but each site will be addressed individually. We hope that the SuDS management train provides the potential to maximise the number of houses that a site can take while integrating nature-based solutions in the best way.

The Chairperson (Mr Martin): I am still learning in the Committee. I take you back to the slides on existing drainage provision. As you said, Simon, that involves hard SuDS and an underground tank. How does that underground tank work? In my mind, I see a large construction under the ground that slowly fills with water when there is heavy rain: is that all that that is? A large container fills up with water to offset the amount that will go into the storm drain. Is that just one tank that fills up first, so that the flow into the storm drain is offset by 10,000 cubic litres of water or whatever?

Mr Wightman: Effectively, there is a hydrobrake or restriction. You will —.

The Chairperson (Mr Martin): What is a hydrobrake? It sounds like something out of 'Space: 1999'.

Mr Wightman: I am dropping down here.

The Chairperson (Mr Martin): It is OK. Hopefully, you were not — oh, you were on screen. There you go. I was hoping that the camera was still on me, Stuart. That will be a moment for your colleagues to see later.

Mr Wightman: I am not going to live that down.

As I said, it is only when you get a rainfall event that the level starts to build up. The normal flows will be allowed to pass through. It is, effectively, a bit like going from a pipe with a diameter of 1 metre down to one with a much smaller diameter. When you get a heavy rainfall event, it gradually starts to back up. It is, effectively, a restriction that lets the flows build up. The tank fills up and then gradually empties. As you said, it is basically a space below the ground that is able to fill up when you get a heavy rainfall event. However, if there was not that much rain and the capacity was there and you had the smaller pipe to take it, it would not fill up; it starts to fill up only when there is heavy rain. It is a feature that can be put in when you are doing SuDS. Even the ponds have them; it restricts the flow, so it enables the water to back up for a period of time.

The Chairperson (Mr Martin): I am considerably more confused than I was before you answered that question. Do you want to have a go at it, Simon?

Mr Richardson: Simple Simon will have a go at it.

The Chairperson (Mr Martin): Just pretend that you are answering a question from a 12-year-old. Go ahead, Simon.

Mr Richardson: The tank fills up, and, as Stuart said, the water discharges from the tank at a slower rate into the river or the existing sewer network. The tank has to empty. If it does not, it will not be ready to take the next flow of rain that comes down. It has to empty at some point. It empties at a slower rate into the existing sewers. All of the rainfall that goes into the tank ends up in the existing sewer network. There is no infiltration into the ground, so there is no benefit from water's naturally seeping into the ground. All of the water goes in. It does not just fill up and stay filled up; it has to empty, so all of the water goes into the existing network, ready for the next event. That does what it says on the tin: it slows the flow of water, as Stuart said in the presentation. It deals with the rate at which water enters the sewer network, but it does not reduce the quantity of water that enters it.

The Chairperson (Mr Martin): That makes more sense. Perhaps you could send us some stuff on how exactly they work, preferably with diagrams.

You said that all of it goes into the storm drain at the end. Is there a reason that hard SuDS are not made with some sort of permeable membrane, so that you get some offset benefit? I am just following the logic. You are using permeable offsetting in soft SuDS. If that water will, in the end, slowly going into a storm drain, surely it would be better to make that construction permeable in some way, in keeping with the principle that you use overground. Is there a reason why it is not?

Mr Wightman: There are a couple of things. They sometimes put in geocellular tanks, which look like milk crates. Sometimes, those are lined, and sometimes they are not. If they are not lined, there will be a bit of infiltration into the ground. Depending on the typography of the area, you do not want groundwater ingress into the tank. There can be different reasons like that, but it all depends on the local make-up of the ground.

The Chairperson (Mr Martin): That is fine. I have one more question. That answer was really useful. Do you have a sense of how the findings from the consultation will shape the forthcoming regulations that will be enabled by the Bill? You had a timeline there.

Mr Wightman: As I said the last time that I was up here, we will review the responses first thing in the new year. At this stage, it is a very high-level policy consultation. As Simon said, even in the Department, we are changing our views. The SuDS management train is quite new to us in the Department. If we get buy-in and a mandate to take that forward, that is where we will go. We are certainly getting that from the industry. As Simon alluded to, I met members of the Construction Employers Federation (CEF) a few weeks ago. You mentioned the hard tank. The example that you will see was going to be a hard tank, but it was inviable economically and as well as practically — the tank was huge. Given the effects of climate change and the allowances, the volume is impractical when trying to build such a tank alongside other services. That is another reason and incentive for developers to move towards green, nature-based solutions. The idea is that, after we are given a mandate, we will do the more detailed consultation at the back end of next year. That is the timeline. We will prepare an internal business case on the options. As you can imagine, there will be a raft of options around the approval. How are you going to approve it? Will it be a new organisation or an existing organisation?

I should highlight the fact that developer services-type work is being done in DFI Rivers and Northern Ireland Water and by our DFI Roads colleagues. That type of work is being done, so it will not be all new. For the likes of developers, we need to move towards a one-stop shop. You will probably hear CEF say that it is frustrated about how long it takes, because you have to apply to different parts of the same Department to get things. That is where we are going. The timeline is the back end of next year, but we will do the draft regulations alongside that.

The Chairperson (Mr Martin): That is fine.

Mr Stewart: Thanks, folks, for coming along. It is really interesting. I appreciate that this is just the start of a long process, so apologies if my questions get ahead of that. Following on from the Chair's point, will you talk me through the difference logistically and financially for a developer, or anyone who builds a development, between hard SuDS, which are, for the most part, currently used, and soft SuDS on a scalable trajectory? For example, what is the impact cost to a developer, ergo the cost of a house, if they build 10 houses and use hard SuDS versus if they build 10 houses and are required to use soft SuDS? Does that make sense? How do we go about working that out? Ultimately, how appealing are soft SuDS to a developer, and where does the cost come in?

Mr Richardson: That is a valid question. It is something that we have struggled with as well — well, not struggled with, but what is the incentive for a developer to pick up soft SuDS?

Mr Stewart: Correct.

Mr Richardson: One of the benefits of our solution for developers is that NI Water will adopt the network. That in itself is — are we going to get those guys to move at all? From our discussions with developers, they realise that, given the way that things are going, if they use a soft SuDS on a site, there is a chance, as Stuart said, that that will have minimal impact on the existing network, with very little water leaving the site. There may be circumstances in which that would be really beneficial to a developer. I am highlighting the fact that we need all the tools in the box. We will need hard solutions at some points, and we will need ponds on their own at some point. At other sites, we may be able to use the full management train. We do not have figures for how much a hard or soft system adds to the cost of building a house. The costs are specific to each site. They come down to the hydraulic issues at each site and its geography and topography. All those things have to be considered. I cannot answer your question —

Mr Stewart: That is fine. That is understandable.

Mr Richardson: — but it is the right question to ask. We will continue to ask that question, because, if we come to a point at which developers say to us, "Look, we are just going to go back to building concrete tanks", we will have lost the battle. We have had a positive response, and we want to build on that. The consultation process is throwing up a lot of positive responses from developers, and we hope to maintain that and get their expertise in designing the policy properly, because we think that it is the way to go.

Mr Stewart: Absolutely. Developers' buy-in is key, because they are the ones who build the houses.

Mr Wightman: Generally, as you move up to bigger developments, there is more scope to have space for those things. The new regime would probably kick in where there are five or more properties. That is where the category of a private street kicks in for our Department. Five or more properties would be the level for the new regime. When you get into hundreds and hundreds of properties, there is definitely a lot more scope for blue-green solutions.

Mr Stewart: I know that we are still at the early stages, but question 4 in the consultation was:

There was a list of options. I am interested in hearing what you think that should look like. I am also conscious of the fact that we have 11 councils, some of which have produced area plans and some of which have not. There is a potential postcode lottery in how the proposals will be interpreted and adopted by local councils when it comes to planning. What is done now when, for example, developers voluntarily opt for soft SuDS and send those plans to councils? How does that work at the minute, and what should that look like after this process?

Mr Wightman: Those are very good questions. There have been a couple of pilot schemes — the Antrim site is one of those — with a storm-water management group and the Department. The developer had to get self-assurance from the industry, because the Department did not have the power to approve anything. That was a long and frustrating process for the developer.

Mr Stewart: I can imagine.

Mr Wightman: There is only a handful of sites where a developer or developers have taken on that risk. You are then left with it being up to a management company, and households pay for that. I do not want to pre-empt the policy.

Mr Stewart: No, but I am curious to know about it, given your expertise.

Mr Wightman: Wales introduced schedule 3 to the Flood and Water Management Act 2010 in 2019, so it has had a SuDS approval regime. There are 22 councils. The policy is done centrally by government, but, similar to what you mentioned, it is interpreted in 22 ways. We aim to have one policy in Northern Ireland and do something centrally to have consistency. That is where we are going, but that will be subject to what happens down the line. Our intention is to keep things consistent. The same developers work in different council areas, so let us keep it consistent.

Mr Richardson: We would need to agree the best way forward with the councils and the planning authorities in each council. That issue is there for discussion and agreement as we move forward.

Mr Stewart: OK. No doubt there will still be a different interpretation among each of the 11 councils' planning authorities in how they do it, but consistency will, ultimately, be the key.

Stuart, you talk about the fact that soft SuDs have been used by developers in only a handful of cases: is that mainly because the process of working with councils and getting self-assurance has been so laborious?

Mr Wightman: Yes. No government regime is in place to which developers can look. It is up to the developers to do it on their own. That is the challenge for them.

Mr Stewart: Yes, and they are not being incentivised to do that.

Mr Wightman: We are trying to develop that new regime.

Mr Stewart: You have ably led me on to my next question. You might talk through the example of Wales. There is a lot of concern among the public, because, while having those spaces is great for sorting the problem, when developers leave and management companies are not formed, because agreement to them cannot be reached, we end up in a limbo land, asking, "Who on earth is responsible for those patches?". They could be hedges or areas of grass or weeds. Down the line, they might be soft SuDS areas. What is the ideal scenario for their maintenance? Is it adoption by NI Water, for example? Would a management company have to be set up to ensure that they are maintained properly and kept functioning?

Mr Wightman: You are describing the questions that we have asked, obviously. Again, I do not want to pre-empt the policy discussion down the line, but we are well aware of the issues of unadopted developments. I live in a development where the developer went bust, and it was messy at the time getting the management company, because it also was affected. Therefore, I am well aware of the legacy and I do not want to add to it. Adoption is slightly different to ownership, but certainly around the adoption, central government needs to be able to step in. We need to factor all that in. I do not rule out the management company option; we cannot at this early stage. All options are on the table. However, your concerns will be factored in.

Mr Stewart: I said at the start that I knew that it was going to stray into policy, just by the nature of it.

Mr Wightman: Your points are well taken. One of the challenges that we will have is this: how will all this be funded?

Mr Stewart: Exactly.

Mr Wightman: If it is factored in in a simplistic way, it is a green space that fills up with a bit of water versus a green space that does not. Grass will need to be cut on both. The management piece should not be that much different. Specialist maintenance will be needed maybe once every five or 10 years. If there is a model there, you will not want to tamper with it too much, because you are getting income from the residents who benefit from those green spaces. There are arguments for and against. That is what I am saying.

Mr Richardson: Maintenance is a big factor. The regulations allow us to design, approve, operate and maintain. We have to put in place a policy system which will do those four things, and the maintenance one is at the end of the line.

Mr Stewart: Absolutely.

Mr Richardson: We have to look at that. As Stuart said, hopefully, if these are designed properly, if there is a management company within a development, it will cut the grass, do tree pruning and whatever. This, if these are designed properly, will not add much more general maintenance to it, and it could be incorporated —.

Mr Stewart: It is self-sufficient, effectively.

Mr Richardson: Yes, hopefully. That is the importance of designing this and getting it right at the start.

Mr Stewart: I will make a final point, if I may. You talked about Wales, Stuart. I am just curious. If you are looking at somewhere, anywhere in the world, that does this immaculately and you think, "That is the gold-plated standard. I want to copy and paste it and bring it here", is anywhere doing it well at the moment? One of the things that are good about coming late to the party on this is that we can copy what goes well and learn from what went badly. Where are we looking at?

Mr Wightman: From the UK point of view, that is Wales. The problem is that our climate is different. I have relatives who used to live in Florida, were there are swales built into the front gardens. The problem is that, in Florida, it rains, but, 20 minutes later, the sun is out and the water evaporates.

Mr Stewart: Whereas we rain for two months.

Mr Wightman: There are places where it has been integrated like that. However, locally, Wales is a fairly good example. They have struggled in England: they have had the Flood and Water Management Act 2010 schedule 3 for a long time, but they still have not implemented it. We have the benefit in Northern Ireland in that we have one Department, which we are all in, and one water company. All right, we have 11 councils, but, in England, there is a plethora of authorities. All our roads are in one place, whereas they have local roads.

Wales went ahead and brought it in. There are lessons learned — a bit of a lessons-learned piece in Wales — that we can learn from. You mentioned the difference in interpretation from one area to another: we can avoid that by having one authority that the councils can refer to. That is what we are thinking.

Mr Stewart: That is really fascinating. I look forward to continuing this as it goes along. Thank you.

Mr Dunne: Thank you, folks, for your presentation. A couple of points were made very well by the Deputy Chair that I was going to cover. I come back to the point about 10%: the green space issue. How problematic is that? Ultimately, the main interest of developers is to make money and build houses. They get as much land as they can and squeeze in as many houses as they can. We have seen that trend growing over the years. Gardens are much smaller now than they used to be. How do you overcome that hurdle, that 10%, which is not included in the figure for green space?

Mr Wightman: A document was made quite a long time ago, a guidance document, 'Creating Places', by the Department of Regional Development (DRD) and Department of the Environment (DOE)'s Planning Service. That is where the 10% comes from. However, you will see that there are other figures, depending on the local councils. They can dictate higher percentages than that. When you go to the Antrim site, you will be surprised. It is spacious; there is a lot of green space on that site. Antrim is a good example. The SuDS features that they had there did not contribute to the — as the Chair mentioned, that would be the disincentive. Why would you build those things if they do not count towards the green space? That is just taking away money from sites for properties, so that is a key driver for us. We also need to work with our planning colleagues, because there might be an interpretation that green space has to be a usable space — that you can kick a football up and down it — whereas one could argue that, if it is aesthetically pleasing, it should be treated equally. If it is planted out with benches and things, is that equally green space? That will be a challenge for us that we will have to work through with our planning colleagues.

Mr Dunne: That is OK. I know that the consultation will still run for a few weeks yet, but has there been any initial feedback on engagement with developers, or are you satisfied that there is good buy-in and interest in it?

Mr Wightman: As Simon said, we had a conference in June. As a follow-up, we met the Construction Employers Federation (CEF) a couple of weeks ago. Every builder is going to be different; every developer will have a slightly different view on it, depending on the size and scale of the sites that they are working on. Certainly, the feedback from CEF to date has been positive, and you will be able to explore that yourselves when you meet it. However, depending on the size and scale of the smaller developments — the Deputy Chair mentioned that it might be more of a challenge for some of the smaller developments to try to make room for those things — certainly, when you take the capacity constraints that we have, and so on, if there is an incentive to do —.

Mr Dunne: That was what I was going to say. The sector is ready and willing to be innovative. It is very much up for it and looking around the world, globally, and we have met them on those issues. I suppose that is the thing: is the incentive there because it is an alternative to, ultimately, get the green light in some cases around capacity, or is it a mixture of

?

Mr Wightman: It is a mixture of both, and with a lot of additional drivers. SuDS has been on the table for a very long time — for as long as I can remember; for the past 20 years, certainly. This is the first time ever that I can genuinely say that there is definitely a change in momentum with the industry in particular. It is the first time that I have heard examples of it being no longer economically suitable for them to put a tank in the ground; it is better for the developer to go for the above-ground, natural solution. That was news to me. Ten years ago, that would not have been the case. There are all sorts of challenges now with the Climate Change Act, and nature-based solutions are the in thing now. That move is a permanent one, and the industry recognises that.

Mr Richardson: Our hope is that the nature-based solution becomes the norm, becomes business as usual, rather than the concrete pipes and tanks, but I reiterate the point that we need all the tools in the box for different sites to allow that to happen. We have not been surprised — rather, really pleased — with the response from developers and their positivity on it and their willingness to be involved in the discussion and to help us take it forward.

Mr Dunne: That is good to hear. A final point on that maintenance issue and the cost: how much of this initial work will ultimately be put onto house buyers as well?

Mr Richardson: For my part, getting back to the point: if we can design the SuDS management train properly, we can make the additional maintenance minimal compared to what the grass-cutting and tree maintenance at any site at this time. If you are grass-cutting a flat green space or one with a swale in it, there probably is not much difference. If it can be designed in a way that has minimal cost to future maintenance, that is one of the key aspects that we would like to learn to come forward with our design proposals.

Mr Dunne: I presume that the Department will not ultimately be the one maintaining them, but we have seen how the Department has struggled in many cases with the challenges of maintaining what is out there today, whether that is grass, weeds or road maintenance, and so on. We can talk a lot more about that. Ultimately, it will come down to the people to have to —.

Mr Wightman: The 10% is really important, because if you have 10% green space including the SuDS, the additional costs should be fairly minimal, but if you have 10% green space and another 10% for the SuDS, you are doubling the amount of space that needs to be maintained.

Mr Dunne: You know more about engineering than I do, but it needs to be maintained regularly as well. It will look great now, but in five, 10 or 15 years, there will be maintenance costs. I have some concern for residents, going forward, but I certainly appreciate the ongoing work.

Mr Harvey: Basically, looking at your diagrams, we have the old way, which is about getting all the water from the houses and paths away as fast as possible into the waterways, and some were man-made and some made their way into the sea. We are allowing for normal rain, but it is abnormal rainfalls that are the problem. When all the tanks and all your bits and pieces for retaining the water are backed up, if there is an abnormal rainfall, will the flow still be the same?

Mr Wightman: You have brought in another crucial aspect, which is that the hard system has a finite capacity because it is beneath the ground. SuDS can be designed so that no water leaves the site while each level of the champagne fountain fills up, and it gives the rest of the network a chance to drain. In a typical hard SuDS scenario, there will be a constant flow of water leaving the site during the rainfall event, albeit that it will not get any higher because it has been throttled and kept back. You are right: the soft SuDS will hold the water back and help the rest of the network. It copes better with the peaky, flashy sort of water, and it helps with that. The challenge is that all our systems have been designed to get the water downstream, away from the property, as quickly as possible, and that is where the flood risk is. That is the challenge for us.

Mr Harvey: If there was abnormal rainfall in one area at one time, it would still produce the same result, because it will fill up, and then it has to disperse.

Mr Richardson: It could be, yes.

Mr Harvey: Your grass storm drains get the water away, but they are somewhat porous. Have the dangers of those drains, for example, if they fill up and flow, been considered?

Mr Wightman: Health and safety is a big part of the works, and we have to do all sorts of assessments. The SuDs systems have to be designed very much —. Even the bigger systems, like the basins where you have a bigger volume of water, have to be designed with flat slopes. Health and safety is of paramount importance. In England, there are examples where the SuDS pond is at the back of the development with a 12-foot fence and a life ring; they cannot be integrated into the development because of a health and safety assessment. It needs to be done in such a way that it becomes an integral part of the development, in the same way as there are ponds and lakes in parks. There is an education piece when you are developing them.

Mr Harvey: Obviously, it is important to divide the clean water from the sewer water. You never want clean water going into the sewer. We want to get it away as quickly as possible. Thank you.

Mr McMurray: I was struck by your last point about the developers becoming more financially viable. It is like Adam Smith's "invisible hand" in real life, which is interesting in its own way. A lot of the points have been covered, and I appreciate that. Where do you want to see responsibility for design going? The big issues are the responsibility for design and the funding approval body, if that makes sense. Those are two separate points. Start with the responsibility for design. Where do you think it needs to go?

Mr Richardson: The design of the site, ultimately, will be done by the developer, because they develop the hard pipes that go into the ground at the moment. Going forward, we would like to put a policy in place for the design options available to developers. The developer will then design their site in accordance with the technical guidance documents that we will develop for that type of intervention, and they will put the plans forward for approval through the planning process. There will need to be an approval element of SuDS design within that planning process. We do not have that at the moment. That will need to sit somewhere within the overall approval process. Fundamentally, we are not looking to take the design away from developers. The developers will still design their own sites, but they will do so within the guidance documents for soft sustainable drainage systems.

Mr McMurray: We referenced the Welsh model, where there are 22 ways of doing it. You have already indicated your preference that there would be one —.

Mr Wightman: To be clear, there would be one organisation, preferably. I do not want to pre-empt that, because I am conscious of where we are —.

Mr Richardson: It is not our preference.

Mr Wightman: Basically, the 11 authorities would pass over to that one entity, and it would give the stamp of approval or else refuse. That is the function that we are talking about here.

Mr Richardson: That is one option. The 11 councils could go to what we would call a "SuDS approval body" (SAB), wherever it might sit, in order for the design to be approved, denied or whatever. That would then go back to the council, which would go through its normal planning approval process. We are saying that that is an option. We are not saying that it is our preference, but there needs to be a body to approve the design that developers bring to the table.

Mr McMurray: I have a quick comment and then another question. We have talked about maintenance companies. I am sure that colleagues on the Committee have had issues with maintenance companies in their constituencies. There needs to be an awareness of that when handing over to a maintenance company. That is probably reflected in some of the responses.

Mr Richardson: I pay a maintenance company in my development as well. It comes along and does a reasonable job — actually, it does a good job. In cases where a maintenance company is working well in a development, we would expect them to continue to work well, because, if the soft SuDS are designed properly, there will not be a vast increase in the amount of maintenance that they have to do. I am not saying that there are never any problems with maintenance companies; there are. There are problems now, however, before we even go to soft SuDS. In cases in which maintenance companies are working currently, adding well-designed soft SuDS infrastructure will hopefully not add much more difficulty to maintaining the site.

Mr McMurray: Thank you. We have the Bill here, and there are various points in it. We have talked, Chair, about Henry VIII and all that carry-on. I am curious: is there a danger there, or does the one depend on the other so that the policy does not get ahead of the legislation, if that makes sense? We do not want to end up in a contrived scenario in which we approve the Henry VIII powers, if you will, but we do not actually know what policy is going down and all the rest. Does that make sense?

Mr Richardson: As Stuart said, SuDS have been around for a long time — we recognise that — and have not moved forward. Our colleagues are taking the Bill forward, and the Bill will give us the power to design, approve, build, operate and maintain soft SuDS. We could wait until the Bill was there to start the process, but we are trying to get ahead of the game and, as the Deputy Chair said, to get buy-in from the developers. The first question I had for developers was, "Is this the right thing to do?" If they were to say that they were not going to do it, there would have been no point in us spending our time trying to force people to do it. We are trying to get buy-in at that high level at this stage. I think that we are moving in that direction, but we will always have to wait until the primary power is in place to give us the power to do what we want to do. When it comes to that point, however, we want to be in a position to move to saying what the policy will look like and what the technical design guidance for developers may look like. We will not be able to get ahead of ourselves.

Mr Wightman: I was trying to draw that out at the start. There are two separate things. The Bill will give us the enabling powers. Looking at the Bill, the question is probably whether those enabling powers are fit for purpose and provide sufficiently for what the regime may look like. As I said, a lot of things are up in the air, because we need to develop the policy. To reassure you, I can say that we worked closely with our colleagues when they worked with the Office of the Legislative Counsel (OLC) around the enabling powers in developing the Bill. In England and Wales, they put all the detail into the primary legislation, whereas we realised that a lot of things need to be developed, so we made the decision to put the detail into the subordinate legislation. There is a distinct difference, and you will see that. Scotland is different again, and we are probably more akin to Scotland in that respect. It is important to draw the two things out. It is quite a normal practice — I have been involved in it before — to do the regulations alongside the primary legislation so that you do not have that gap. We are not setting a precedent here or anything.

Mr McMurray: My next question is about water quality. I think we all know that there is a challenge with water quality across the board. One element of water quality is surface water picking up all the detritus, microplastics, oils and whatever. Is there any information or finding that the sustainable drainage, when you go into those swales, filters out some of that? Again, that would be an important thing to draw out if it is the case, but also making sure that it does, just to improve the water quality. If it just goes into a big concrete tank, all the nastiness is still in the tank and then goes into the river.

Mr Wightman: Well, our diagram shows the four pillars of SuDS design. You are totally right: the basic premise is that the more you hold the water back, the more opportunity there is to filter those pollutants out. For the hard SuDS, there is virtually no opportunity. If you move to the end of the pipe green — soft SuDS or detention basin — there is a bit of time, but it is still limited, whereas, if you have it at every stage of the development, there is more opportunity. Even with the grass swales, as the water is being conveyed, some of it is infiltrating. I think that one of the members raised that. At every stage, you get an opportunity for infiltrating, for example, grease or oil from the road, and there is more opportunity to prevent it from making it through to the receiving watercourse.

Mr McMurray: That is important. That is me finished, Chair. I like the SuDS analogy, and I like the management train. Like getting on the gravy train, we should all get on the SuDS management train. Thank you.

The Chairperson (Mr Martin): Unbelievable, Andrew. Your line was interesting.

Before I bring Cathal in, I have a couple of questions about some of the stuff I have just heard . In the first instance, we talked about the SuDS approval body, and I have a question about that. If there is a SuDS approval body, do you envision or see a possibility of it being a statutory consultee at a planning level, or is there another way that it will feed in? You said that it needs to be stamped so that it can proceed. In terms of the current planning analogy, do you see that as a statutory consultee or something else?

Mr Wightman: The quick answer is yes. DFI Rivers, at the moment, has a schedule 6, and it goes to the planning advisory unit in Rivers. It would be similar to that sort of authority. You go to Northern Ireland Water to get your article 161; it is the same idea.

The Chairperson (Mr Martin): OK, so because you have opened it up a wee bit, I am going to gently segue into the Bill. Stuart, you mentioned that OLC drafted the primary legislation, and you noted that it is not uncommon in how it is drafted that the regs come after, and there are good reasons for that. Certainly, that has been my experience of primary legislation being drafted, and it seems very appropriate for the flood management Bill. We took some evidence from the Examiner of Statutory Rules around the Henry VIII clauses that my colleague just mentioned, and my understanding is that Henry VIII clauses are not unusual, although they give extremely wide-ranging powers. Those clauses, as drafted at the minute, do not seem to be overly limited in scope, so Henry VIII clauses are OK, but there should be very clear boundaries around them. You may not be an expert on the Bill. I do not know how much detail you have had, but do you accept that it is important, when drafting Henry VIII clauses as they apply in this Bill, that the scope of those clauses should be limited so that they do not give wide-ranging powers outside the policy intent of the Bill in the first place?

Mr Wightman: First of all, I am not an expert on Henry VIII clauses, but I know the clauses that you are talking about; they enable changes to be made to primary legislation through regulations. We need those, certainly, because, as you mentioned, we might need to make changes — we do not know yet — to the planning. You mentioned planning. You asked about limitation. Certainly, it would make sense that the legislation that, you feel, you need to amend should be listed, but, because of uncertainty about which legislation needs to be amended, that is why it is not restricted in that way. That is my limited understanding of it. I understand why they are needed, and that is why the regulations will have to be laid before the Assembly and debated in draft, rather than by the usual negative resolution procedure: you are potentially changing primary legislation.

The Chairperson (Mr Martin): One example of that, which is relevant to the session that we are dealing with, is clause 2(4), which states:

I believe that the Examiner of Statutory Rules was a little concerned about "a specified person", and that a body was going to be formed — the body that we are currently talking about — but not actually specified in the primary legislation. It just refers to "a specified person". That is the SuDS approval body that we are talking about. Is the Department open to having a look at that? Certainly, the Committee has discussed it, and I am sure that we will get into it in much more depth. Rather than leaving that as "a specified person", is the Department considering tidying that up to a degree, as per the Examiner's commentary around that, and saying what that body actually is?

Mr Wightman: I have to confess that I have not seen the Examiner's comments and scrutiny on that. We can certainly look at it. Obviously, at the minute, there are options that we do not have. Therefore, we have to be careful. We cannot pre-empt. Certainly, we can liaise with our colleagues on water drainage policy on that point.

Mr Richardson: That is what we will do: liaise with them and take their view on it, Chair.

Mr Wightman: That is a good holding answer there, Simon. That is fine.

Apologies, Cathal: I took up a wee bit of time there, but you will get your go now. I am looking forward to it, Cathal. Away you go.

Mr Boylan: My moment in the sun, Chair. Thanks very much

The Chairperson (Mr Martin): Yes. Get your Instagram ready.

Mr Boylan: Thank you very much for the presentation. It is quite an interesting one. I have been shouting for these measures — permeable paving, and so on — for a long time; a number of years. The concept and premise behind it is very good. It is interesting. We talk about the Bill. The broad premise of the Bill is fine, but we need to line up all our plans. I can understand why the Department is doing it, but, if we do not get our area plans right, do not identify our floodplains and go forward on the new build stuff — if we do not marry all that up — we are going nowhere with this, to be honest with you.

Members have asked about developers, but there are two things. Ultimately, the consumer is going to pay for this, one way or another, whether you like it or not. If a developer puts a property up and we have introduced new SuDS standards, will they come under British Standards Institution (BSI) standards? Eventually, if we get some regulations and regulatory form, properties will have to be built to a certain standard and introduced. They will go on the market, and people will buy properties in that development. That is one element. What standards are we really looking at with regard to the regulations?

I agree with those measures. I also agree with the idea that you start with the house and then work from the house down the driveway, onto the footpath, out onto the road and into the tank, or whatever measure you use. I believe in that. If we do not get people to buy into this, they will not buy the properties. We need people in this. I agree that it starts with the developer and the planning process. We have a good opportunity. At the minute, we have serious problems with the retro stuff, legacy sites and everything else. That is a matter for another day. If we are serious about getting people on board with this, we need to have.

I agree with doing this process now in tandem with the Bill, so that we get a better understanding of where we are going. Certainly, the developer has a big part to play, but all those measures that you are talking about — I am looking forward to a visit to see exactly how that works, because, like the Chair; I like to see the physical stuff to see how it works.

Andrew's point is interesting. It is always about the management group. If we are seriously thinking about putting in SuDS, it should be high-quality, low-maintenance stuff. Let us have all that discussion.

That was a wee bit of a rant, Chair, but I know the subject inside out, and I think that it is a good time to put all those issues on the table now, in tandem with our discussion on the Bill.

It is funny, every time Henry VIII is mentioned, I think of somebody coming along on a horse. I understand the reason behind that principle. We do not know where we are going at the minute, how we will bring in the primary legislation and what the regulations will be at the end of it. We need to find out all those things. For those of us who have been around a wee while, we understand the principle behind it.

With regard to the regulations and area plans, that is a broader discussion that we need to have, if you understand where I am coming from.

Mr Wightman: When we met, the CEF was saying that a couple of developers mentioned that they need to understand now, which is your point, when they are purchasing sites to see how much space they need to allow. I know that it will be decided in the next mandate, but I recognise that there are decisions being taken now. That is why it is good to have the consultation.

Mr Boylan: Yes, 100%. Will BSI standards be used? Do you know what standards will be used?

Mr Wightman: There are standards out there. There is an organisation called the Construction Industry Research and Information Association (CIRIA), which represents best practice for the whole of the UK. We have a question to answer around whether we go for a Northern Ireland-bespoke standard or whether we follow elsewhere. It may be a combination of both. We may need to put a filter over it because we want to walk before we can run with it. There are standards that we can learn from. We are not reinventing the wheel.

You mentioned permeable paving. We may not do the full suite of SuDS measures to begin with. We might gradually roll it out. We will learn from best practice that is already out there. The standards will involve detailed drawings. The grassed swale looks like a depression in the grass, but it is actually an engineering feature. There is stuff below the ground that you cannot see. There are filters, stones and pipes. All that stuff is out there. It is just about how much of it we adopt in Northern Ireland from day one. That is the decision that we have to make.

Mr Boylan: It will come down to costs at the end of the day.

Mr Richardson: One of the things that you mentioned, which is a very valid point, is what will the design standards for the street-level and house-level interventions look like? Will that look like a development that people want to live in? It has to be something that is nice and aesthetically pleasing, so that people will want to live there. It is integrating the necessity of the drainage with the look and the amenity spaces in a site as well, so it is very important.

Mr Boylan: It is an interesting conversation. Thanks very much for the presentation.

The Chairperson (Mr Martin): I will bring a virtual Justin in now, I hope.

Mr McNulty: Thank you, folks. I can sense the energy and enthusiasm for SuDS coming through my screen. If there were a salesperson's job available for SuDS, you would get it; so, well done, folks.

I have several questions. The 1973 and 2006 legislation do not mandate SuDS in developments. Further to what Cathal was talking about, surely planning policy is the way to proceed on this front to ensure that SuDS is mandated as part of every development. What is your perspective on that?

Mr Wightman: Through the legislation and the drafting, the advice that we received was that we will have the power. We can mandate SuDS. Through the Bill, we can have regulations that will require SuDS to be mandated in all new developments. It would be part of the planning process, but, with regard to the legalities, it would be a self-standing Bill. The Bill would become an Act, and we would be able to use the powers in the Act to introduce a regulation to say that all developments of a certain size over five properties must do x, y and z. We will have that ability through the regulations in the proposed powers. I mentioned earlier that it might be done through the statutory consultee process. However, a developer would not be able to proceed unless they had that approval for the SuDS system in question.

Mr McNulty: Further to what Andrew was saying about hard SuDS versus soft SuDS, surely soft SuDS is a no-brainer. You would think that the cost of construction and maintenance for hard SuDS would be higher compared with costs for soft SuDS. The environmental implications for hard SuDS would be more complex. The positive implications of soft SuDS are, again, a no-brainer with regard to their value. Therefore, is it not simpler to employ soft SuDS as a solution to storm water run-off? Also, where you are at with developments and maintenance, do soft SuDS need to be mowed? Can you not put wildflower beds into soft SuDS? The idea that every green space has to have a lawn mower over it every week is just crazy. Do you know where I am coming from on that front? What is your perspective on that?

Mr Richardson: All those considerations are correct, and we need to look at all of them. It would be wrong of us to sit here, and say, "Yeah, OK, we have to mandate for soft SuDS", even though that is the way that we want to go, because there will be sites where soft SuDS will not be viable due to the topography or whatever it may be. I have said this a few times, but we need to keep all the tools in the box. I agree that we need to mandate for SuDS and slow the flow of water and reduce the amount of water, but in certain circumstances we have to allow developers to be able to deliver that through hard solutions if that is the only solution available to them.

I have no difficulty in mandating for SuDS. Mandating on a narrower window when we do not fully know the implications of mandating that are is where my caution is. That is why I am really keen to involve the developers, and say, "OK, look, where we can, we want to move down the route of soft SuDS because there are benefits for us", but, if we exhaust all soft SuDS options and there is no other option, maybe it is a combination of hard and soft, and that may be regular. Therefore, we do not want to commit to mandating soft SuDS at this point because we just do not know what the implications of that may be.

Mr McNulty: As for the criteria, is SuDS progressed for green field run-off or less?

Mr Wightman: As I said earlier, if there was a requirement for the SuDS management train, which could be hard and soft in a new development, yes, the initial requirement would be green field run-off. In Northern Ireland, we tend to use a 10 litres per second per hectare figure. In other parts of the UK and even in Europe, that figure could be a lot less and dependent on local topography and ground conditions of the site. The answer is yes, green field run-off. In the future, we may have different levels of green field run-off depending on where the site is, but the answer is yes, that would be our starting point.

Mr McNulty: The whole objective is to slow flows and put less pressure on drainage systems and treatment works. Water is an aid to treatment works on occasion, but when it comes to separation, what is the rationale for SuDS, on the one hand, to take water off a site that is still going into a combined sewer or downfall?

Mr Wightman: NI Water has informed me that only in limited circumstances nowadays would a developer get a connection into the combined system. The diagrams referred to going into the receiving watercourse or receiving sewer. When we talked about "sewer", we meant a storm sewer. You are totally right: we do not want storm water going into the combined sewerage network. You hear about spills and out-of-sewer flooding, and we have traditional solutions for dealing with those. The root cause of the problem, however, is that too much rainwater is getting into the network, and we need to slow that. We have a retrofit transformation project that we briefed the Committee on, I think, in May, where we are going out and trying to retrofit SuDS, and that will inform some of the policy work. We need to be maintaining water on a site as much as we can even before we put it into a watercourse, a river or, in very limited circumstances, into the combined sewerage network. I realise that, in some instances, it might end up in a combined sewer at some stage down the network. If it goes into the combined sewer, it is only going to contribute to spills and other issues in the network.

Mr McNulty: Where are water butts currently used in the North, if at all?

Mr Wightman: They are more of a voluntary thing. I think that there have been some examples in schools of their use, but that has only been on a voluntary basis. My understanding is that, in government, we have not rolled them out as part of a measure. On the property-level stuff, it would be a new thing if we were to roll them out. My understanding is that some commercial premises and some schools have trialled them.

Mr McNulty: Should the design criteria around soft SuDS not provide for self-maintenance, going back to the point around wildflower beds and such? Is the idea that swales and attenuation ponds are some sort of health-and-safety threat not a prehistoric one? Should they not be embraced as features in a development whereby the price of a development is actually better? I absolutely want a pond nearby for my kids to be able to play around, rather than seeing it as a danger. We are all too risk-averse in this society. Catch a grip, guys. What is your perspective on that?

Mr Wightman: We agree. Simon mentioned that we have a toolbox, and there is an education piece here. There is an expectation, which you alluded to, that people expect bowling green lawns in new developments. There is an education piece about the wild. Not everybody will want to live in a development that has that. Some people will look at a wildflower garden and think that it is unkempt, and other people might embrace it, so there is an education piece. There will not be a one-size-fits-all approach.

The images that I showed you included a closely mowed swale versus a planted area. Of course, it adds amenity if it is done in the right way. Probably, the more plants and things that you put in, the more expensive it becomes. In theory, you have lifetime maintenance; maybe every five years or 10 years you have to desilt those things, so it might be more expensive if they are planted. You are right to say that these things can contribute to place making.

Mr Richardson: We have to be very serious about health and safety. I know that you are, and I am not suggesting that you are not. In the design of these, good design will make it easy to maintain and will make it safer. All of those considerations need to be taken on board. The design of the interventions that we will use will, hopefully, involve minimal maintenance and will definitely have to be safe.

Mr McNulty: Folks, thank you so much for your evidence.

The Chairperson (Mr Martin): I have one final question for you, and, again, it is on your slides. I am sure that there is a really good reason for this. In your slides on point 2, ponds are called "attenuation pond", which is, I think, what I referred to them as. In the slides on the policy aim, they change to "detention pond". What is the difference between an attenuation pond and a detention pond?

Mr Wightman: There is a range, and they are basically the same thing. "Attenuation" is just another word for storage and holding the stuff back. Detention basins are a subcategory of the attenuation ponds. Detention basins tend to be dry and then fill up with water. With attenuation ponds, as soon as you introduce the pond, it tends to be that there will be some permanent bit of water there. There is a whole category of things under "attenuation". Some of them will have some permanent water, and some will be dry and then fill up.

The Chairperson (Mr Martin): Finally, on that, on the third set of slides on the policy aim there is what we will call a detention pond because that is what you call it there. It would be useful if you were to provide the Committee with some graphics to show what these things are. From this evidence session, I am kind of half thinking that these are 10-feet deep and normally filled with water, and they have wire around them so that animals and people do not fall in. I am also thinking that, no, they are little basins and that they are usually dry and that kids could run into them in the summer, and there is no water in them. It would be useful, for my understanding, to know what an attenuation pond looks like. In point 2 of your slide presentation, the attenuation ponds look larger. Is there is a difference in point 3, which is on your policy aim, between those and a detention pond? The next slide shows a picture of a detention basin, which looks absolutely fine. However, if it was full, it would be deep water.

Mr Wightman: That is a retrofit example in Mansfield. Believe it or not, it is so deep because they had to make it like that to pick up the infrastructure of the existing storm network, It only ever fills up to roughly the level of the stones. That is why retrofitting is so much more challenging. If you design them right, they can be a lot shallower to begin with, because you are running the water on the surface rather than into it. That one is so deep because they had to pick up the level of the pipes.

The Chairperson (Mr Martin): I hope that my maths hold out, but I am guessing that the larger the attenuation pond, the shallower it can become in terms of surface area by volume. If you have a larger area, it will take in more water, but, if you have something significantly smaller, it would need to be deeper to have the same effect. Is that right?

Mr Wightman: Yes.

The Chairperson (Mr Martin): Maybe you could share a few more.

That is all that I have. As far as I am aware, no members want to come back in.

If members are content, we will take a short comfort break of five or 10 minutes to allow people to stretch their legs.