Transcript from Wordwave

Transcript created by WordWave Event: Public meeting held at 19:30 in Camelford Hall, Clease Road, Camelford PL32 9PE to discuss the Draft Report of the COT Subgroup on the Lowermoor Water Pollution Incident Date: 17 February 2005 Chairman: Professor Frank Woods CBE In attendance: Professor Kevin Chipman, Professor Stephan Strobel, Dr Lesley Rushton OBE, Dr Anita Thomas, Mr Peter Smith, Mr Douglas Cross, Ms Frances Pollitt, Mr Khandu Mistry, Mr Malcolm Brandt, Mr James Powell, Ms Sarah Fisher (Press Officer), Kabir Gobim (Recording Technician), John Fallon (Public Address system) Audience included: Paul Tyler CBE MP, Dan Rogerson (Prospective Parliamentary Candidate for North Cornwall, Ms Anderson, N Neale, Robin Penna, S Davey, W E Chapman, M Beal-Toms, N M Jones, N Evans, Sybil V Griffiths, R Gibbons, B Pentecost, R E Newman, Judith Young, J Stockton, Peggy & John Molesworth, Ray Bowler, Sarah Almond, Melanie Shelton, David Bloye, Dr J Lunny, J Spratt, Dr Anthony Nash, Dr D Miles, Mrs Miles, Pat Owens, T Chadwick, Mr & Mrs Ian & Ro Clewes, Carole Wyatt, June Hills 020 7404 1400 [email protected] www.wordwave.co.uk Smith Bernal WordWave, 190 Fleet Street, London EC4A 2AG CHAIRMAN: This meeting is part of the 12-week consultation period which takes place and is taking place following the publication of our draft report, which appeared towards the end of last month. The Lowermoor subgroup, most of whom are sitting at this table, was set up as part of the Committee on Toxicity of Chemicals in Food, Consumer Products and the Environment. And we started the substantive work in January 2002, meeting on 19 occasions, and you will recall that we held our first public meeting in Camelford in April 2002. We had two terms of reference. The first was to advise on whether the exposure to chemicals resulting from the 1988 Lowermoor water pollution incident has caused or might be expected to cause delayed or persistent harm to human health. And secondly, to advise whether the existing programme of monitoring and research into the human health effects of the incident should be continued and whether or not it should be modified in any way and to make recommendations. Those of you who have looked at our report I think will realise that we carried out a wide-ranging investigation, using and seeking information from as many sources as possible, including the commissioning of studies carried out by outside contractors. And you will hear a little more about that later. These sources of information are listed in section 12 of chapter 2 of our report. And we are of the opinion that this is the most comprehensive report into the health effects of the 1988 pollution incident that is in existence. Now, this meeting is going to be in two main parts. I am not going to say any more by way of introduction. We are now going to have a number, a small number, of brief presentations by outside contractors and also by members of the committee. The purpose of that is to set www.wordwave.co.uk 1 out some key points, not all of the key points, but some of the key points that are very germane to the way in which we have tackled the problem that we were faced with. And we would also hope that these would provide some sort of structure upon which you could hang your questions, because once my colleagues have given their presentations, I am then going to throw this meeting open to your questions. And I wish to remind you and I will continue to remind you throughout this evening that this report is a consultation document. This is not necessarily the final form of that document because what people say to us, write to us or convey to us may well change the content of our report. I think it must be clear to you that any interpretation we put on information that is given to us may be looked upon in a slightly different way by others. And indeed, from past experience it is possible to find that there is further information which at the time of writing that report was not available to us. Now, I am now going to go straight into the presentations. I’ve been reminded that I have to tell you that if you have a mobile telephone, it would be rather nice if you turned it off because I am assured by the electronic experts that if it goes off, so will all of these things. The first of our papers is given by Mr Brandt of Black and Veatch. Now these are the gentlemen who helped us a great deal by modelling certain aspects of water quality - this being a very important aspect of our work - because we needed to know the range of exposures in relation to the quantity of toxicants present in the water. And I am going to ask Mr Brandt to start this off. MALCOLM BRANDT: Thank you. I don’t know how I’m going to juggle three things but we’ll see how we go. I’ll start off with a brief overview of the system. The www.wordwave.co.uk 2 water, raw water, is derived from Crowdy reservoir, comes into Lowermoor treatment works where it is pre-treated with chemicals. It then -- the raw water flocculates and settles out in the settlement tanks. There is often a little bit of carry over, so then there is further removal of solids in the sand filters. It is then disinfected, usually with chlorine, before it enters the contact tank where it has usually up to about 30 minutes contact time for it to work effectively. The final water then transfers into a storage reservoir, which acts as a buffer to manage the difference between supply and demand. The water then finally enters the distribution system. The part of our brief was to look at the components of the system where the aluminium was actually accidentally dumped. Traditionally it would be -- normally it would enter the system at the head of the system, head of the treatment works. So our objectives were, we were asked to model the hydraulics of the incident, with these following objectives. That is, investigate the extent of the mixing, which is essentially the dilution of the alum within the treatment works; predict the peak concentrations of the aluminium in the water leaving the works and simulate the spread of that aluminium through the network. Although we refer to alum, in fact we only modelled at the aluminium concentration and we did not model secondary contamination -- secondary chemical reactions that could have contributed to the contamination within the distribution system. Our approach was for the contact tank, we used CFD modelling, that is computational fluid dynamics. It’s a 3D modelling technique widely used in the engineering industry, an example being it’s extensively used in aeroplane design and car design, usually looking at the air flows. We www.wordwave.co.uk 3 use it in the water industry to analyse the hydraulic performance of facilities, e.g. the circulation of water in storage tanks, which is exactly the use that we’re using it here. We also modelled the storage reservoir using the same technique. For the trunk main network, we used a hydraulic network analysis model that we had been involved with in 1993. And this is a method of tracking water quality problems through a distribution system. To give you a little bit of background, we started off with the contact tank, to give you a few details of it. It comprises the inlet; there are four effective sections - the water is mixed in these sections; there are baffles, which were installed at a later stage. This tank, we believe, was used -- had a prior life, probably as a storage reservoir, not as a contact tank. It therefore has this chamber in here through which there are two holes, and these two holes are fundamental to the performance of that tank. The alum was discharged at the head of the fourth section and the outlet, which is a high level outlet, is at the end of the fourth section. Just a point to note, there is also -- on the records there is a low-level washout for that tank. This slide looks a bit messy but it just demonstrates the complexity of the flow patterns. I won’t try to describe what’s actually happening here; but the complexity of the flow patterns in the early chambers and the intense mixing that is going on. By the time it gets into the last two sections, you’re getting more into what we’d call plug flow. So this is the -- I’ll run through the simulation of it; it’s a three hour simulation of the incident. The time 0 is 5.00pm when the incident started. The concentration increases with time at the maximum of 40 minutes, the time when they stopped discharging. And the concentration; as you can see as www.wordwave.co.uk 4 the time progresses, the concentration at the outlet is reducing. The other point to make is that the colour indicates the significant, shall we say, concentration of aluminium at the bottom of the tank. So the conclusions are that the aluminium does sink to the bottom of the tank and spreads, and it spreads upstream against the flow of water. The holes in the tank, which I was talking about, which is there’s one there, which is this cross-section here, that’s the hole, it is showing how the aluminium and the water are mixing and that’s a significant hydraulic characteristic of this tank.

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