Southern Water project for storm discharges

The News, Portsmouth

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00:00Okay, yeah, so we've identified Grove Road CSO spills around 24 times a year, so our

00:10objective is to try and get that below 10 spills a year. And what we've identified is

00:14above Grove Road, we have a lot, at the time we didn't know, but we have got a lot of misconnections

00:20into the foul sewer. So what we've done is we sent a team out, there was 800 properties

00:25that we looked at, out of the 800, 200 have come back misconnected, which is, when I mean

00:32misconnected I mean the surface water is connected at a point in the property and they both feed

00:37out to the foul sewer. So the objective is to try and disconnect them at the source,

00:42run a separate sewer out to the surface, connect it onto the surface, which in turn will take

00:46stress off of Grove Road, which then pumps to Kilcommon, so it's a kind of, you know.

00:52Is that one of the issues that kind of creates the stormwater overflows that we see?

00:55Yeah, it's that unnecessary water, rainwater into the sewers, that's what gives us, so you know,

01:00we were seeing spikes, we've got SLMs, which are monitoring units on the manhole covers,

01:06inside the manholes, and we will find that during heavy rainfall the sewer level's coming up,

01:11so it was a heavy indication that in that area, obviously we had misconnections on the sewer.

01:18So hopefully this work should hopefully reduce stormwater flows.

01:21Yeah.

01:22And yeah, what does it entail?

01:24So when the team come out, the first thing they do is identify that the, identify the point of

01:30where it's misconnected, and here for instance we found that the top gully, or the top downpipe even,

01:35sorry, takes the majority of the roof, and then we also want to have one at the rear that comes

01:40round, so at this point here we've got the foul and the surface mixing into one gully pot, that

01:45then goes out, obviously mixed, and during heavy rainfall obviously, you know, that runs through

01:50100% sometimes, instead of the normal kind of 15-10% or, you know, normal household kind of

01:55usage. So what we're going to do is, as you can see over here, we've run a new sewer out, this

02:00is what the trench is for, this will go straight into the surface waterline, and yeah, it will be

02:06a case of disconnecting the two gully pots, and once we're live in the sewer, then it'll be a

02:10case of disconnecting the two gully pots, and then obviously when we leave the property we'll have

02:15two separate lines, one for the foul, one for the surface, and then it'll be a case of when we have

02:18that heavy rainfall, it will just go straight out to the surface water, rather than running in the foul.

02:25They approached us earlier on, I think it was early, not last year, the year before,

02:32to say that we were a good site for it, especially with our sloping site

02:36and the rainwater runoff, and they put in eight of these units.

02:42Right, and what's in the units, where are they? In the bottom, they hold the initial water,

02:48I think it's 300 litres of storage, and then halfway up it is the soil and the sub base

02:56for that, and the plants that were also provided by Southern Water. Perfect, and how important was it?

03:01Sure, my name's Keith Herbert, and I'm reducing storm overflows in Portsmouth Harbour.

03:06So we're here today announcing a £170 million project that's ongoing, so what does that entail?

03:12So storm overflows happen because water runs off roads, roofs, car parks, driveways,

03:17and goes into the same pipe as the sewage, so the toilets, sinks and dishwashers, and overwhelms it.

03:23Now this is rainwater that doesn't need treating, so our strategy for reducing storm overflows in

03:28Portsmouth Harbour is to separate that water out, because if water companies only had to treat sewage

03:33there wouldn't be storm overflows. So we are going door-to-door to disconnect people's roof drainage

03:39from the fowl sewer and connect it into the right pipe. Each one of those homes that you saw today

03:45will add 50 tonnes of rainwater into the fowl system every year, which has power costs and

03:51it causes storm overflows, so really we're trying to get back to a system that only treats sewage

03:56rather than has to treat rainwater as well. Okay, so yeah, so obviously with this work I guess

04:02there's never any guarantees, but how much of an impact should it have on storm overflows?

04:06Should it end it? Should this be the resolution or is there more to do?

04:10We're in this for the long haul and it's really important that we work with local authorities

04:14as part of local plans to make sure that we have a say going forward in large developments, to make

04:20sure that the new houses that are built as part of the government's housing plan are the most

04:24sustainable draining but also water efficient going forward with an eye on climate change.

04:32you

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