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AMP 4 Wastewater Studies

Eastern and South West England

Project outline

Forming a key part of the Water Companies Business Pans for the 4th Periodic Review, Faber Maunsell undertook assessment the current and projected level of risk in the sewerage network, in accordance with the "Common Framework" and determined the associated levels of investment in Capital Maintenance. Combining risk assessment techniques, mathematical modelling and GIS analysis, and based upon wide ranging base data, the approach was praised by industry regulator OFWAT.

Contract value

£0.5m

Key features

Predictive asset condition modelling, Provide a basis for estimating the infrastructure funding profile
Implementation of UKWIR Common Framework for Capital Maintenance

Skills utilised

Asset Management
GIS
Pipeline Rehabilitation
Regulatory Framework
Risk Assessment
Wastewater Networks

Project detail

Predictive modelling of infrastructure condition provides a powerful mechanism for determination of future investment levels to maintain or improve serviceability. A mathematical model, using Markov Chain Deterioration Matrices was applied to project unfettered deterioration of assets. The model was then adjusted by applying different quantities and mixes of intervention, including: replacement, rehabilitation and patch repair to provide future scenarios of projected condition for each selected level of intervention.

Another facet of business planning is the analysis of the level of risk in the network, in accordance with the "Common Framework". The first stage was to build a risk framework applied covering service and asset failure mechanisms and impacts, at the core of which is a risk matrix and/or a set of standardised questions and risk threshold definitions. Levels of investment were then determined and categorised according to different regulatory drivers and associated key activity levels. This method was systematically applied using a combination of corporate data and structured interviews.

The process had to be both flexible and transparent, for full audit by OFWAT's Regulatory Reporters.

South West Water

The sewerage network was classified by catchment size; all of the large catchments were studied, as were a significant sample of those of medium size.

Levels of risk were determined via a risk framework, which involved asking a set of standardised questions and assessing the responses against a set of risk threshold definitions, covering both likelihood and consequence of failure. For each risk identified, notional solutions were identified, scoped in outline, categorised by asset type, costed using unit cost and proportioned according to the key regulatory drivers. The output was a strategic programme, prioritised by risk level.

The following processes were developed and implemented:

Compilation of key catchment information
Risk Framework
Structured sewerage risk methodology
Formal interviews with operators
Review and challenge by senior operators
Quantification of risk on all assets
Identification of scope of intervention
Formulation of notional solutions (capital and operational)

Anglian Water

An automated GIS-based process for assigning criticality to Anglian Water's sewers was developed, and to determine the current and projected condition grades of sewers and rising mains, together with the associated future intervention costs. This information was collated in a form suitable for completion of the Business Plan for PR04.

A new methodology for "Collapse Risk" was built from two components, namely the probability of collapse and the ensuing consequence. This was structured around concepts enshrined in the Common Framework, and underpinned by existing asset data. The overall objective was to optimise capital maintenance expenditure in regard to the location of sewers that present service risk due to their physical state within Anglian Water's 31,000km of gravity sewers. Key activities included:

Determination of age of sewers, by either direct or indirect means;
Assessment of the current and projected future condition grades of sewers;
Projection future levels of intervention with different scenarios on sewers to maintain an equilibrium state.