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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