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Incidents and Events 2009
Kathryn Buist
23 June 2010
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• Background• 2009 performance• Event types and causes• Event review
– Seahouses– North Charlton SR– Hulne Park, Alnwick
• Summary
Contents
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Notifications
• DWI notified on 23 occasions in 2009• 10 classified as cat 3 – significant• In the Northern region 86 events notified, 49
significant
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Notifications / Incidents - numbers
27
30
36
31
22
25
20
13
32
23
9
11
21
14
9
12
9
56
18
10
7
0
5
10
15
20
25
30
35
40
2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010
notifications
incidents
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Incidents 2009
Jan 1 - Leadgate, discoloured water March 2 - Metaldehyde, pesticideMay 3 – Ashington, discoloured water
4 – Kirkleatham, discoloured water and loss of supply
June 5 – Gosforth, discoloured waterJuly 6 – Seahouses, micro failure and precautionary boilAugust 7 – North Charlton, micro sample failureNovember 8 – Northern Trunk main, loss of supply,
precautionary boilDecember 9 – Brunton Park, discoloured water
10 –Bedlington, discoloured water
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2009 Incident by type
0
1
2
3
4
5
6
7
8
discolouration Ecoli pesticide
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2009 Incident by cause/area
0
1
2
3
4
5
6
7
AoDW Distribution Ecoli pesticide
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Event review - Seahouses
•Overview on the wall
•Bichwood BPT and Elford SR supplied via NTM from Warkworth
•Seahouses – seasonal variation in demand – 622m/day , 750m/d in summer
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Background -
• Samples reported on 22 July 2009• Reg sample from Elford – 15 p.E.coli and 18 p coliforms• Ops sample from Birchwood - 9 p.E.coli and 29 p coliforms
• Discussed with LA and HPA and precautionary advice issued – allow investigation and minimise risk to public health
• Network analysis involved • 1,335 advice to boil cards issued• Samples from network
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Background
Site visits at both sites undertaken on 22 July
Birchwood BPT removed from serviceRemoval of Elford – network would be starved
- area needed to be rezoned to protect supplies
Sampling organised from 3 local supply chains
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Northern supply chain:-
Mousen SR Glororum SR
Southern supply chain: -
Hedgeley SR North Charlton SR
Central supply chain: -
Wandylaw SR Birchwood BPT Elford SR
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• Some discolouration due to rezoning (10 contacts)
• To protect public health and combat potential contamination, residuals were raised
• Initially through secondary chlorination, but not effective enough
• Manual addition at SR which lead to 1 customer complaint
• Widespread flushing could not be done – water resource issue
• Targeted flushing as required
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• 2 sets of clear micro samples available on 25 July
• Boil advice lifted, cards delivered between 19:30 and 21:55
• Rezoning of area had caused increase in leakage and high demand required tankering for 4 days
• Total of 119 micro samples taken over 7 days, 9 were unsatisfactory– (2 from SR and 7 from customer properties – low level coli and
E.coli)
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Further investigations
• 23 July – flood test and structural inspection at Birchwood– Ingress identified, repaired and return to service on 12 August
• 27 July - flood test and structural inspection at Elford– No ingress identified return to service on 30 July
• Air valves on network checked by ops team
• Review of maintenance strategy for SR – inspection of 100 SR by March 2010
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North Charlton no 1 SR - August
• Supplied from branch off the NTM• 2 tanks, supply 1,353 properties in total
• 29 August 2009, reg sample reported as containing– 1 pres coli (confirmed as 1 E.coli)
• Sampling campaign set up• Following samples, residual raised at N Charlton• All results satisfactory• Both compartments were removed from supply to allow
flood testing and inspection – all satisfactory• Audit of lab - satisfactory
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DWI assessment
Critical of – 10 discoloured water contacts
2 consumer contacts for T and O – chlorine
no mention of Warkworth data in the 20 day report for N.Charlton
Concerned – of ‘hydraulic link’ between the reservoirs. 13km of main between N Charlton and
Elford. All other SR on the NTM were satisfactory.
NWL responded and incident has been closed
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Hulne Park November 2009
• NTM from Warkworth - Alnwick area• Number of pumping stations, critical link between Bolton
PS and the WTWBolton PS has secondary chlorination (0.5mg/l)
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Warkworth and NTM
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• Low level alarm at Hedgeley SR followed by lo lo• Maintenance on site at Bolton PS – not delivering water.
Assumed to be pumps overheating.• Warkworth WTW confirmed NTM running ok.• 10:40 Hedgeley 0.4m, suction pressure at Bolton PS still low,
onsite team conclude Hedgeley SR not receiving water.• TMC involved and Warkworth NTM increased – no
improvement– Burst suspected on NTM– DTS requested to walk the NTM to locate burst (8
involved)• Tankering requested for North Charlton SR• 13:20 1st disc water contact received (54 in total from
Alnwick)• Step testing done to identify burst location• Exact location identified 16:45
Hulne Park, Alnwick 8-12 Nov 2009
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08 November
• Assumed discolouration in Alnwick was from increase in mains velocity
• Burst location 3m deep, 1.5m away from a lake – limited access only with 4x4 vehicles
• H and S issues - trench and flooding• Area around the burst subject to flooding, 6.9km of
12” NTM isolated
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08 November• Hedgeley, Wandylaw and North Charlton SR depleting and
concern over time for repair, depressurisation and loss of supply.
• 23:00 silver team called – Distribution, RCC, WQ, CCC, Production and Emergency Planning
• DWI notified based on >50 disc water contacts
• Some of network would lose supplies before repair complete• Hedgeley and Wandylaw SR nearly dry, N Charlton and
Wandylaw ~12 hrs left. Glororum SR isolated to remain on storage
• Decision made for BWN based on depressurisation of rural network 4209 properties
• Considered need for alternative supplies and mutual aid tankering
• 06:50 1st no water contact received• Liaison with HPA, LA and CCW commenced
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09 November • Repair was carried out and NA working on plan for
recharge – 36 hours predicted • Static tanks made available, bottled water stations
designated• Few opportunities to chlorinate upstream of repair,
decision to increase Warkworth to 1.5mg/l. Secondary chlorination increase 1mg/l
• All SRs to be hand dosed
• 4209 properties received BWN• 18:00 all SR dry (except Glororum). • 280 contacts, 110 for no water and messaging
system was used • 2 bottled water stations set up• Hedgeley SR making water and pressure building up
at PS upstream of Bolton PS
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10 November
• Sampling plan for when properties were due to come back on line
• 2 sets on first day
• BWN to be lifted at earliest opportunity, but ‘blanket lift’ impractical
• Withdrawal of static tanks and the bottled water stations
• PRV checks in network
• Chlorine residuals 1.5-2mg/l
• Discussions with HPA regarding lifting of BWN
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11 November• 1st set clear samples
• Tankers stood down and statics recalled
• Chlorine back to target dose
• HPA and LA updated
• 16:30 second set of samples clear – safe to drink to 1448 properties
• 12 November
• 2nd set of samples clear – safe to drink to 2761 properties
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Some facts
• 115 micro samples between 8-11 Nov• All clear for coli and E.coli• 687 contacts received
226 hits on message system. Website updated 18 times
• 32 static tanks (2,200l each) were deployed between 9-11 Nov.
• 3 bottled water stations – 52 pallets of bottled water (26,960 l)
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DWI assessment
• Critical of not consulting HPA and LA prior to issuing BWN– This has been rebriefed to the WQ team and the event is
closed
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Summary
• Discolouration still an issue• Acceptability managed through AoDW programme for
System zone 7 (due date 2012)– A project is in the final business plan for AMP 5 (2010 – 2015)
for SZ6