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DSEAR / PEXA in Dŵr Cymru Welsh Water Peter Griffiths DSEAR Technical Surveyor.

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Presentation on theme: "DSEAR / PEXA in Dŵr Cymru Welsh Water Peter Griffiths DSEAR Technical Surveyor."— Presentation transcript:

1 DSEAR / PEXA in Dŵr Cymru Welsh Water Peter Griffiths DSEAR Technical Surveyor

2 Overview Introduction What is DSEAR and PEXA PEXA / DSEAR and the risks to Dŵr Cymru Welsh Water Zoning programme

3 A bit about me ! Started working for Dŵr Cymru Welsh Water in August 1980 as a Tanker Driver in Waste Water Got involved in H+S as a Safety Rep Moved from Tanker Driver to Team Leader Late 1990s took on the role of PEXA surveyor for Mid Wales Waste Water Entered into H+S full time around 1995 and began getting involved with DSEAR and PEXA on a more in depth basis Represented DCWW on the UK Sludge Dryer User Group

4 What is DSEAR and PEXA DSEAR stands for D angerous S ubstances E xplosive A tmospheres R egulations 2002 PEXA Stands for P otentially EX plosive A tmospheres ATEX ATEX derives its name from the French title of the 94/9/EC directive: Appareils destinés à être utilisés en ATmosphères EXplosibles.

5 So, what can blow up in Welsh Water Sludge Dryers Sewers Pumping Stations Batteries Explosion risk

6 Sources of fuel Petrol / Hydrocarbons Methane Hydrogen Carbon Monoxide Hydrogen Sulphide Ammonia Dust

7 Southport golf course DCWW Dryers Junction 32 M4 Incidents

8 Southport Golf Course Explosion Seaside Golf Course “Explodes” An explosion in a seaside pumping station between the 14th and 15th fairways at Southport Municipal Golf Course, showered lumps of brick and concrete for over 300 yards across the course. Petrol, believed to have leaked from a service station into the flood water drains running between the fairways ignited when the automatic switch in the pumping station came on. Head Green keeper John Wright, well known in the North West Section for his marathon running, told The Golf Course it was very fortunate no one was injured as the explosion happened alongside the temporary green at a peak playing time on Saturday afternoon. Golfers playing the course during the morning reported a strong smell of petrol when they played their round. The course is now closed for repairs to the sewer and pumping station. From John's point of view that is no bad thing as the mild winter has produced so many golfers the course has been overplayed and it will give him a chance to improve the drainage and attend to essential maintenance.

9 Sewer Explosion Jct 32 M4 Welsh Water Sewer “Explodes” 2005 At approximately 1500hrs on the 14 th July 2005, an explosion occurred in the main Y&P sewer that carries sewage from the Cynon and Taff valleys into Cardiff WwTW. The exact location was in a large manhole located between the M4 motorway and the GE medical factory (formerly Amersham) in dense woodland, the explosion was contained within the sewer and blew off five manhole covers, one upstream of the main manhole two on the main chamber and three downstream of the main chamber. The main chamber consisted of three large concrete lids weighing 1 ton each. It appears from the initial site investigation, that a poplar tree that was growing within close proximity to the main chamber, had touched the overhead electrical pylons belonging to the National Grid, carrying 275 kilovolts, this then earthed down the tree into the sewer igniting a pocket of flammable gas causing the explosion.

10 Sewer Explosion Jct 32 M4



13 Dust Explosions Explosion in Sludge Dryer, Cardiff WwTW A dust explosion occurred in dryer no 1 at Cardiff WwTW on 20 th January 2007. Two operators were injured when a cover blew off, hitting one of them in the face causing injury and both receiving facial burns that looked like a sever case of sunburn. Having assessed all relevant data it is likely that the incident was caused by dried product self heating within the BMS producing a build up of hydrocarbon gases at the top. An internal dust explosion within the BMS could have occurred however it is more likely that a backdraft fire and explosion occurred by oxygen ingress from a displacement of the cover. This caused hot flame and vapours to be released from the BMS and it is likely that the cover and grating were blown off. It is thought that one of the operators lifted the cover to investigate where the smouldering was coming from and at this point oxygen entered the BMS mixing with the unburnt gases. The smouldering material the ignited those gases creating the blast.


15 Who are the DSEAR Group Small multi-discipline group Provides advice and guidance to DCWW on all DSEAR and PEXA Zoning issues Maintains the DCWW PEXA Handbook

16 What is my current project Re-zoning and De-zoning DCWW Assets Sites first Zoned in 2003 based on the risk of spillages of petrol into sewers on the basis that there were one or more petrol stations in the catchment area.

17 DCWW DSEAR Zoning Project

18 Statistics DCWW assets that could be De-zoned based on the removed risk of spillage from petrol stations 667 These include WwTW and associated SPS and CSOs

19 Statistics Within the DCWW network we have, 677 Petrol Stations 667 Active Petrol Stations, 10 stations currently do not sell fuel but are still operational 517 Active Stations that are connected to the DCWW Sewer Network 429 Petrol Stations with Interceptors 88 Petrol Stations without Interceptors, these are the ones that pose the highest risk to our assets.

20 Statistics In 1970 there were 37,539 Petrol Stations in the UK In 2012 that had fallen to 8,677 a 75% reduction Supermarkets now own 14% of all petrol stations, but sell 40% of all fuel.

21 Where are we now What has prompted the current review. Decreased number of petrol stations Improved safety systems at petrol stations Risk project completed to determine which petrol stations are a risk.

22 Current Project The role of DSEAR Technical Surveyor has been created to review and update the DCWW asset database to ensure our assets are compliant. Visit the 88 sites to complete the zoning survey and produce new classification documents and site plans and to renew the site signage. Carry out further survey work to ascertain if local industry or onsite process such as sludge digestion are present and to complete or update the zoning for those risks.



25 Questions Questions !

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