"1) The proposed equipment will fully comply withEnvironmental Protection Act 1990 , Part 1, Secretary of State's Guidance - Clinical Waste Incineration Processes Under 1 Tonne an Hour, PG5/9(91), February 1991."
" 3.3.1 Carbon Monoxide Carbon monoxide (CO) concentrations averaged 670 mg m-3 in test period 1 and were slightly improved in test period 2. Both are well above the CO limit value given in the Secretary of State's Guidance notes for New Clinical Waste incinerators. Mean combustion efficiency was low, averaging 99.3%. It should be possible to achieve combustion efficiencies of >99.9% on modern clinical waste incinerators, although there are no interim requirements for existing plants given in the Guidance Notes. However, existing units of this design will have to meet the EP Act limits by 1995. Therefore, this type of plant will require combustion modification or face closure. There were frequent, large excursions in carbon monoxide concentration and several of the 15 minute mean values exceeded 1500 mg m-3 (see appendix B) .... 3.4 Reasons For Poor Combustion Performance There are two general reasons for the poor gas phase combustion. These are: (a) operational factors such as poorly controlled bag feeding rates, combustion air settings etc, and (b) engineering design problems. Both of these problems will need to be overcome if the unit is to perform satisfactorily and fully meet the combustion requirements of the Clinical Waste Incineration Guidance Note. More importantly, performance will need to improve considerably to meet the more stringent combustion criteria being considered by the EC for this process. The detailed reasons for poor gas phase combustion are discussed below."
" 3.4.5 Modifications Some operational and minor engineering changes were made to the incinerator in the weeks following the trial. A limited retrial to monitor gas phase combustion was undertaken. Although carbon monoxide levels were much reduced and were on average much closer to achieving the 100 mg/m3 limit, there were still appreciable excursions above 2000mg/m3. The data from this short trial were also very limited and further work will be required to establish what further modifications are necessary to satisfy the Guidance Note CO criteria. The re-trial demonstrated that gas phase combustion problems resulting from low residence times within the combustion chamber and other factors could be considerably reduced by increasing furnace gas temperature and turbulence. Changes to operational practices could also help, but there is a limit to what these measures could achieve and a larger combustion chamber may be required. "
"... Inevitably the Warren Springs report identifies further issues on which I feel we need assurances from Erithglen, specifically on the following points:- W.S. Report in 3.3.1 identifies high CO concentrations with frequent large excursions in CO concentrations exceeding 1500mg m-3."
"... We would answer the questions raised in the letter from the Health Authority as follows:- 3.3.1 - High Carbon-monoxide Concentrations and 3.3.2 - Unburnt Hydrocarbon Emissions. This plant was ordered in early 1989 as a proto-type plant, and was tested in late 1990 by Warren Springs Laboratory. The reasons given in the report 3.4 - Reasons for Poor Combustion Performance, have now been solved by the following design changes:- 3.4.1 - Feeding Problems The elevator is now controlled by an inverter drive, which allows the system to deliver one bag per charge to the new Airlock Loader, see below. This is achieved by detecting the bag at the top of the elevator, slowing the drive and then stopping in approximately 100mm. A second photo-electric cell now detects the bag dropping into the Airlock. 3.4.2 - Furnace Door and Ram Feeder Problems The furnace door has been re-designed to be airtight. The ram feeder system has been discontinued and a new rotary airlock system has been introduced, thus eliminating this problem completely The rotary airlock needs no maintenance during its working life and has only one moving part. 3.4.3 - Low Furnace Chamber Temperature This problem has been largely overcome by 3.4.2. above. Furthermore, the fully modulating primary burner is now controlled by the furnace temperature, thus always maintaining 1050(C. 3.4.4. Low Furnace Gas Residence Times The furnace diameter has been increased, and the primary and post combustion .. are now controlled by inverters which are controlled by the PLC which responds to high/low Carbon-monoxide levels, due to the charging rate. This has resulted in a far better turbulence within the firing chamber. Oxygen Injection Erithglen and BOC are conducting tests on Twin Corsair 1000S Boilers at Derbyshire Royal Infirmary and the new system will contribute the following advantages for our clients:- 1) Higher through-puts with total combustion and burn- out. 2) Reduced gas/oil consumption. 3) Increased thermal efficiency. 4) Substantially lower emissions to atmosphere including Carbon-monoxide and particulates."
"Q: Competent engineers who did not regard the basic concept as fundamentally unsound might well regard Erithglen's assurances as appropriate A: As I have stated earlier, I think that there are areas of competence which would perhaps consider the assurances appropriate, and others who would take a more sceptical view."
"A. Difficult for me to judge, my Lord, how would I have responded in 1991. I tend, I think, to be a somewhat sceptical individual, and had I read in 1991 that they had fitted a larger combustion chamber, that they have - and that they have achieved a greater degree of turbulence by installing inverters I think I might have been sceptical at that time. JUDGE TOULMIN: Only might? A: Probably would. I cannot say for certain but I think so."
"Q. So to a non-specialist that provided a good level of comfort for going ahead?. A. It provided a level of comfort but whether it provided sufficient comfort to go and spend over a million pounds before one had actually seen one tested at its rated throughput is a matter of opinion and probably an area in which I tend to disagree with Mr Carver."
"A. I think you have, yes. I am saying that the areas that Erithglen were addressing in their letter of30th January 1992 were moves in the right direction, but there was no proof there that it was - that they had done enough to completely rectify the problem. JUDGE TOULMIN: So they were entitled to be comforted to some extent by what was in that letter? A. I think that is reasonable, yes. JUDGE TOULMIN: And there was nothing in that letter which amounted to a - either a glaring omission, in other words, an area of the Warren Springs report which was not dealt with, nor alternatively a comment in that letter which should have put them on enquiry that things were not as good as Erithglen said they were? A. Well, I believe that a - to look at the letter with a sceptical eye and to think, "
"Q. Did you mean or intend to convey that answer, by that answer, that a competent engineer would accept the assurances as being appropriate or otherwise? A. I think a competent engineer should have maintained a reasonable degree of scepticism. JUDGE TOULMIN. He may have maintained a reasonable degree of scepticism, the question is what, if anything, he should have done about it on the basis of the letter which he received? A. I think he should have asked for further information: how much larger is the combustion chamber going to be; how have you dealt with the airlock doors."
"Mr Hyde for the SHA made serious criticisms of TBA in his written reports and maintained in evidence that he would in the circumstances have made further checks, but conceded in relation to Mr Piggin's letter dated30 January 1992 that a non-specialist would have been comforted by Mr Piggin's answers, and that it was apparent from the Warren Springs Report that further development work could be done and was being done and that some competent engineers "would perhaps consider the assurances appropriate and others would take a more sceptical view."
"Although the responsibility rested with Mr McKenzie I have no doubt that either Mr Wright or Mr Croydon, who had also recently visited the plant at Derby, would have asked questions directly or through Mr Pym if they had been concerned about what they had seen or heard."