Resilience Planning for Large Diameter Trunk Mains. Joe Hartley MWH

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1 Resilience Planning for Large Diameter Trunk Mains Joe Hartley MWH

2 Cabinet Office: Resilience is the ability of assets, networks and systems to anticipate, absorb, adapt to and/or rapidly recover from a disruptive event OFWAT: Resilience is the ability to maintain essential services under extreme circumstances UKWIR: Disruptive and extreme events - defines types of hazards to be considered Weather, flooding, etc Not minor pipe bursts or leakage UKWIR Report published May 2013 MWH have developed a model based approach to trunk main resilience assessment

3 F-Links (Functional Links) are sections of strategic mains between network assets and major junctions in the network; their function is to transfer water between locations (e.g. from A to B) and this function can be disrupted by failure. F1 SR WTW F2 PS SR DMA F3 F4 F5 F6 Junction

4 The F-Link resilience assessment is undertaken by assigning a scoring/weighting to each Link Based upon Two parameters:- A Functional Resilience Code; Alphanumeric code assigned to each F-Link to reflect the availability of downstream storage capacity and the number/capacity of alternative supply routes. An Impact / Severity Score; Scores are assigned to each F-Link to reflect the numbers and types of consumers affected and for how long an F-Link outage would apply.

5 The Functional Resilience Code identifies: Downstream storage, which can be utilised during an F-Link outage Alternative supply routes, which limit the impact of an F-Link failure Downstream Storage Code A B C D E F Z Description No storage downstream and a pipe failure will immediately affect properties or key customers <6 hours storage downstream 6-12 hours storage downstream hours storage downstream hours storage downstream >36 hours storage downstream No effect on storage downstream Alternative Supply Code Description 0 No alternative trunk supply available 1 A single alternative trunk supply through duplicated pipes 2 Two or more alternative supply routes

6 Downstream Storage Code Description A B C D E F Z No storage downstream <6 hours storage downstream 6-12 hours storage downstream hours storage downstream hours storage downstream >36 hours storage downstream No effect on storage downstream A B C D E F Z Immediate Impact Little Impact

7 Impact assessment score: weighted score (1 to 10) based on number of Domestic, Key and Sensitive customers affected plus any adverse reputational effect. Severity assessment score: weighted score (0 to 10) based on expected outage duration after exhausting available storage. Combined Impact / Severity Score: product of two scores (0 to 100), where low scores indicate high resilience and high scores suggest low resilience (i.e. a vulnerable link in the network). Impact Score Severity Score Combined Impact/ Severity Score Inputs Domestic Customer Score + Top User Score + Reputation Score Repair Hours + Operability Hours less Reserve Hours Impact Score x Severity Score Weighted Scoring Scale

8 . Apply InfoWorks WS Critical Link Analysis (simulation option) to provide accurate and automated resilience assessments. Quantifies the ability of assets to transfer the required volumes of water. Allows application of Programmable Controls; to simulate the interaction of the various components in the system (pumping stations, control valves, storage tanks, etc.). Assess the capacity of alternative supply systems. Reduced uncertainty in flow-path variables; hydraulic engine used to assess WSS capability to maintain supplies. (e.g. flow, pipe roughness). Test various demand conditions (scenario analysis). A more accurate assessment of reservoir survival times.

9 Total Impact score = D1+D2+D3+D4+D5 Additional weighting for large consumers and sensitive customers Plus a Wild card score for high profile venues and industries (e.g. National Assembly, Power Station, Regional Hospital) Direct disconnection plus overland flood impact can be included Infoworks Criticality Module used to evaluate the impact of loss of each F-Link trunk main section. Burst Overland Flood Impact Modelling

10 The total time that a pipeline is assumed to be non-functional is based on: load/organise and travel time, repair time and recharge time Without downstream storage, the F-Link outage duration curve also gives the duration of supply interruption to customers. Few trunk main pipes are assumed to be repairable under a 6 hour limit Larger diameters and older materials require longer repair times Travel to remote sites is also considered

11 Properties Impacted From To Mid Point Impact Score Impact Duration < 0 hrs. 0 6 hrs hrs hrs hrs hrs. >72hrs ,000 4,999 3, ,000 9,999 7, ,000 19,999 15, ,000 39,999 30, ,000 79,999 60, ,000 99,999 90, ,000 ~ 100, Actionable range Number of customers served is broadly dependent on pipe diameter, and pipe diameter broadly affects the repair time. Impact duration is modified by available storage, so it is possible for a large diameter pipe repair to take marginally longer time than the available reservoir volume can support, which makes short duration / high impact events possible. High impact/severity pipes are more likely to be found in systems supplying more than 5000 properties. Response Hours Severity Score

12 More Resilient Less Resilient

13 Conduct physical condition assessment survey Further consideration of likelihood of failure No action indicated

14 NDT Decision Support Tool Developed in InfoNet Select specific test type and location for main Prepare contractor information pack Issue work orders and track progress Check results submitted Store results centrally MWH Decision Support Tool (InfoNet) Testing Schedule Pipe Material Cast, Ductile and Spun Iron Steel Soil tests for metallic pipes Soil tests for plastic pipes upvc Polyethylene Glass Reinforced Plastic Test Method Magnetic flux leakage Broadband electromagnetics Ultrasonic thickness measurement Moisture content Liquid limit Plastic limit ph Resistivity Sulphates Redox potential Chlorides Hydrocarbon contamination Dichloromethane C-ring test Single edge notch bend test Circumferential deep notch tensile test Pressure test Ring stiffness test Longitudinal tensile test

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16 MWH Decision Support Tool (InfoNet) Create network schematics Assign data Run batch queries to evaluate each F-Link Analyse results Plot thematics Produce Excel reports Driven by macro buttons Available on a centralised SQL server Accessible to multiple user Automatic audit trails Expandable to entire company region

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21 30 inch CI Ring Road to North Lane Junction The 30 inch CI mains have been identified as the least resilient in the LHLW system. Although the network appears to have sufficient redundancy built into the system where connections with the 18 inch CI and 20 inch CI mains exist, the ability of the network to supply the required quantity of water under all circumstances was compromised due to poor hydraulic performance.

22 Identified Risk Critical trunk main sections identified having high Impact/Severity Scores, i.e. low resilience Bulk supply very sensitive to high demand levels. Insufficient storage capacity Customers supplied directly off the trunk mains network without local storage facilities. Potential Action Follow-up investigations and reporting. Consider condition assessment studies. Investigate hydraulic and connectivity issues. Additional storage capacity or alternative supplies (infusions). Investigate to identify interventions, e.g. re-zoning or contingency plans.

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