AND HERE'S ONE I PREPARED EARLIER - after the big fish kill of August 3rd when we saw dead fish in the Thames from Barnes to Hampton. "Whilst the "buck passing" between Thames Water, Ofwat and Defra is not acceptable, lets not forget that the Aug 3rd sewage overflow was probably, to a large degree, caused by Storm Tank problems at Thames Water's Mogden STW. Since the closure of Kew STW (sold to property developers), Perry Oaks (closed to make way for T5), and the diversion of additional flow from Iver South, I have long suspected that Mogden could not cope with the increased flow. In the excellent BBC TV investigative report by Gareth Furby on Thursday night, Thames Water admitted that it would have been logical for Mogden to have extra storm tank capacity as the basic operation of the plant has remained the same since 1936. The reason given for not increasing tank capacity was that there wasn't enough space on site and due to close proximity of houses, they couldn't expand off-site. The report, however, uncovered that Thames Water had sold off nearby land to three different property developers, one of them partly owned by Thames Water themselves and one as recently as year 2000, well after the closure of Kew! Whilst Thames Water confirmed that the profits from these sales had been injected back into their business, they did not state that any substantial proportion of this was invested in Mogden, in fact they did not link this to Mogden at all! Would the August 3rd event have been so immense if Mogden had been properly managed, funded and modified with some of the proceeds from the property sales? Mogden Residents Action Group put the following questions to Thames Water's Mogden operations manager but he has "passed the buck" and referred us to their press office who have refused to reply to us directly. "MRAG is getting an increasing number of calls from journalists about the role played by Mogden in the 3 August fish-kill incident in the Thames. We thus think it would help to avoid speculation or inaccurate reporting if we could know the answers to the following questions: 1. How many million litres of sewage was released directly from Mogden into the Thames and how much was released from sewer overflows in the catchment as a result of the storm on 3 August? 2. What was the maximum flow received by Mogden during and after the storm and for how long was this in excess of the design capacity of 810 Ml/day? 3. Which of the four west-side primary tanks was out of commission for modifications at the time of the storm and what is its volume? 4. Given the above and the fact that the east side was struggling with excessive sludge flows from an unknown source, how much did this reduce the treatment capacity of the plant at the time of the storm? 5. Also in view of the above, were any storm tanks in use prior to the storm and did any fail to fill during and after the storm?" In the absence of a response from Thames Water, this is what we believed happened on 3 August. 1. Total sewage overflow from Mogden on 3 August was 200,000 million litres - a third of the sewage released into the Thames that day but by far the most toxic compared to that from combined sewer overflows. 2. The maximum flow into the works was probably not much above it's theoretical capacity of 810 Ml/day. However, in an attempt by Thames Water to save costs during the 1998/99 extension, the plant's actual maximum flow capacity only ended up around 690 Ml/day. Storm flows typically last up to a day due to the size of the catchment. 3. We know at least one of the four large west side primary tanks was out of commission for repairs due the continuing breakdown of their antiquated scraper bridges. The effect on flow reduction would be around 50 Ml/day. 4. The flow through the larger east side could have been impeded by as much as a third due to a 'mystery' sludge - possibly even from Thames Water itself, further reducing the treatment capacity by around 150 Ml/day. 5. The Mogden storm tanks are in nearly daily use due to inadequate capacity at the plant. Why else would Thames be applying to spend £50 million to cover them if they were only used for a few hours on a few days a year? You only have to look at any aerial photograph of the plant, all of which are taken on dry clear days, to see several storm tanks in use. Even the photograph on Thames Water's Mogden website shows all the tanks in use! It would be safe to say that at least two thirds the 91 Ml the tanks were in use prior to the storm of 3 August. So, assuming a storm equal to the theoretical design treatment capacity of the plant of 810 Ml/day, the capacity and performance shortcomings would have reduced this by 320 Ml/day. The remaining storm tank capacity would have filled in just over 2 hours and 15 hours later you would have 200,000 Ml of raw sewage killing fish in the Thames. All those fish need not have died if the plant was professionally managed by an organisation that put engineering and the environment first and profit second. It is time the regulators woke up to this fact and took some real action. Stephen Taylor"
Steve Taylor ● 7020d