Current Projects

Exwater UK Ltd is currently assisting South West Water Ltd (SWW) in reducing and more accurately targeting network leakage through the redesign of District Metered Areas (DMA) and the reduction of the Company Average Zonal Night Pressure (AZNP) which also incorporates some redesign of Pressure Managed Areas (PMA) and the installation of Pressure Reducing Valves (PRV).

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DMA Redesign

Why redesign a DMA? | Key Factors in DMA Design | Why Torquay?
Phase 1 | Phase 2 | Phase 3 | Results

Why redesign a DMA?

The cost of targeting and identifying leakage is increased in a poorly designed or maintained DMA. DMAs with a high property count or excessive numbers of meters become increasingly difficult to accurately target or report leakage. Long established DMAs may no longer fit the purpose they were designed for.

The significance of establishing the accuracy of source data is of paramount importance when designing DMAs.

We believe robust DMA designs offer better management and control ultimately leading to the reduction in real water losses from the system.

Key Factors in DMA Design

The designs should:

	Create separate trunk main DMAs
	Reduce the numbers of import meters per DMA (ideally single feed)
	Reduce the number of properties per DMA (<1500 approx)

Further considerations during the design phase:

	Separation of reservoir supply areas
	Operability
	Existing PMAs and additional pressure reduction
	Regulatory exposure (DG2)
	Emergency contingencies (reduced reservoir capacity, pumping regimes)
	Historic distribution problems in supply areas (high burst frequency etc.)
	Seasonal demand
	Future development
	Water quality issues
	Minimising capital expenditure (utilise existing meters and PRVs)
	Continuing rehab on trunk mains
	Large Commercial and Industrial users

Why Torquay?

South West Water had identified the need to improve the accuracy of leakage reporting in some DMAs and Torbay had always been regarded as a difficult area to approach due to:

	Complexity of WIS design
	High burst frequency
	High percentage of brought forward DMAs
	Lack of confidence in DMA boundaries
	Lack of confidence in STRUMAP records
	‘Patchy' local knowledge
	Average of 5 import/export meters per DMA
	High property count per DMA (1 DMA > 5000 & 6 DMAs > 2500 properties)

Extensive rehabilitation in the area dovetailed perfectly with Leakage Control's desire to resolve the ongoing issue of brought forward DMAs and the project was commissioned to redesign Torquay (WIS 508) The original WIS Zone comprised of 16 DMAs and supplying 31000 properties.

Following consultation it was agreed to undertake a sluice valve survey. Due to the complexity of this area we needed to confirm the accuracy of existing GIS assets and initial consideration was given to surveying only DMA “parting valves”. It was felt this could still leave internal valve anomalies and a definitive “state of the system” was needed. As a by-product we would also address mains status and positions and abandoned mains during the course of the survey.

Exwater UK Ltd was tasked with co-ordinating the project. This would incorporate a Pilot Study, Valve Survey and DMA Redesign, 3 phases in all.

Phase 1 (Pilot Study) – to undertake a survey of 30% of all sluice valves in Torquay (WIS 508A/B).

The pilot study covered 14 sq/km (1000 valves) of both rural and urban areas. It was used to investigate the level of anomalies and determine whether there was a need to survey the whole WIS Zone. It revealed a high level of anomalies (>35%) which necessitated a survey of the remaining sluice valves (33 sq/km in total).

Phase 2 - Valve Survey

The valve survey was undertaken by 2 teams who completed a physical inspection of approximately 2500 sluice valves. All anomalies were noted such as incorrect records of size, position, orientation (open/closed/throttled), also where existing valves were not shown on GIS. All anomalies were addressed with the local Distribution Inspector and rectified to reflect the current operation of the network. All valve data was collated and presented to GIS for re-digitising. Once updated the modified GIS data was QA'd as a final check for accuracy.

Torquay survey results:

Results
In brief the table below is a snapshot of the reported leakage immediately following design and implementation of the new DMAs.

Since the completion of this project Leakage have benefited from reduced leakage, improved targeting for leak detection, robust data for reporting and with the introduction of “remote logging” greater transparency on the day to day operation of DMAs. Many more benefits were derived from the project with SWW continuing to apply this design ethos to further WIS Zones in Torbay. To date Exwater UK Ltd have undertaken further DMA redesign projects of WIS 506 (Brixham) and WIS 507 (Paignton) with WIS 509 (Newton Abbot) nearing it's completion.

Typical DMA MANAGEMENT PLAN
(You may need to to view this file).

In all, the project benefited through fully integrated client/consultant resource incorporating all criteria to meet the operational needs of both Leakage and Distribution Departments.

To find out more please contact us.

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AZNP Reduction

Scope of Work | Case Study | Results

Scope of Work

As of the June Return 2006 it became a mandatory requirement for all Water Companies to report the Company AZNP. SWW had one of the highest reported AZNPs of all water companies in England and Wales.

Exwater UK Ltd was tasked to provide solutions to reduce the Company AZNP. Using the company AZNP spreadsheet “traffic light” system as a guides, studies were started at DMA level focusing on the reported AZNPs highlighted “red” (>70m). Pressures were to be reduced principally through the identification of new PRV schemes, verification of existing extracted PMAs and a critical assessment of associated pumps and PRV settings to ensure optimum performance.

Example of “Traffic Light” AZNP spreadsheet:

Using existing SWW data we were able to design a predictive model to confirm areas with potential reduction possibilities.

A further benefit of the project was the subsequent updating of all identified anomalies on the Company GIS during the course of our studies.

Case study - Launceston Town centre

Launceston town centre (DMA 407D07) consists of just over 1000 properties with a reported AZNP of 90.909m. The area is supplied from Windmill Service Reservoir via two import meters. There are two export meters supplying adjoining DMAs. Although certain areas experienced operational pressure as high as 105m, it was accepted that pressure reduction was not possible due to the high elevation of properties in the downstream DMAs.

Original DMA comprising of 1 PMA.

Following consultation with the Distribution & Leakage Departments a detailed study was undertaken. The network was redesigned to separate the DMA into two discrete areas, using one import meter to feed 180 properties and export to adjoining DMAs, with the second import meter supplying a discrete area containing 900 properties. The added benefit of separating the DMA into two discrete areas was pressure reduction could be applied to the St. Thomas area thereby creating a third PMA.

Post- design DMA incorporating 3 highlighted PMAs.

The proposed changes were modelled using “Strumap” and the resultant data was applied to our predictive model. These modelled results predicted that the DMA AZNP would be reduced from 90.909m to 57.887m.

All network changes were completed using existing sluice valves. During the trial of the new DMA set-up all necessary data was collected and analysed to confirm the accuracy of the predictive model. Once confirmed a Meter/PRV arrangement was installed on the supply to the St. Thomas area (150 properties) significantly reducing pressure by approximately 70m.

Results

On successful completion of the scheme the DMA now comprised 3 PMAs and the corresponding Average Zonal Monitoring Points (AZMPs) were identified and logged. The DMA AZNP was recalculated resulting in a newly reported AZNP of 59.208m, a reduction of 31.701m.

Implementation of this scheme not only reduced the DMA AZNP but also improved pressure management and leakage control.

Critical point data following PRV installation:

To find out more please contact us.

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