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  3. NZSOLD 2017 workshop Peter Lilley talks Trustpower and RIDM



The Quake Centre was proud to be a part of the 2017 NZSOLD (Society of large dams) Workshop, with speakers from New Zealand and around the world gathered to talk about risk informed decision making (RIDM).




Workshop presenter Peter Lilley, is the immediate past Chairman of the New Zealand Society of Large Dams (NZSOLD) and represents New Zealand

at the International Commission on Large Dams (ICOLD) Public Safety committee.


Peter is currently a private consultant providing specialist input into project development and governance around water infrastructure and dam safety. Prior to this he headed Trustpower Limited’s dam safety and hydro-electric, storage and irrigation development programmes.


At the NZSOLD workshop, Peter spoke about some of the challenges around managing Trustpower's extensive portfolio of large dam structures throughout the country in regards to RIDM.


“Dam safety is a ‘slow burn’ issue,” says Peter. “There’s a low probability of failure but if they were to fail in the event of a natural disaster such as an earthquake, there is potential for very catastrophic consequences.”


With twenty-nine hydro electric power generator schemes in New Zealand, Trustpower is the country’s fifth largest electricity provider in terms of capacity, output and revenue and the fourth largest retailer (in customer numbers).


The company accumulated a lot of dam structures over a short five-year period from the late 1990’s to the early 2000’s. Of these, parentage ranged significantly from government, to local authority, to privately built and owned. Levels of deterioration were markedly different too - some a youthful 10 years of age with others pushing a more veteran 100 years old.


“Across the Trustpower port folio there’s a wide range of dam structures from reservoirs and canals to spillways and gates,” says Peter. “All are relevant in the context of dam safety, with each structure ranging from low to medium Potential Impact Classification (PIC).”


“Early on, from a dam safety management point of view, it was pretty obvious where we had to put our money to plug the big leaks, so to speak,” says Peter. “The most deteriorated structures stuck out like sore thumbs and it really was a bit of a fire fight to get in and do something about it.”


In the grand scheme of things some dam structures had never had an independent safety evaluation and there was a lack of knowledge around the documentation and deterioration of aging assets. As they dug deeper the challenges became more complex and overwhelming. Vast dollars allocated were but a drop in the bucket of the overall dam risk management required.


“It got to a point where we were overloaded with the challenges but could never actually get anything achieved,” say Peter. “Our dam safety management procedures from the past didn’t fit the future and clearly it was time for change.”


“The question became how do we balance risk and cost across such a wide port folio and multitude of structures, beyond randomly rolling a dice or flipping a coin over safety management distribution?”


A solution was to utilise the maturity matrix approach for RIDM. A scientific mechanism that, from Trustpower’s point of view, allowed them to factor risk into safety decision making - without it swamping the process.


Peter explains how the maturity matrix continuum essentially, “anchors a particular dam structure on a spectrum, from good - a reasonable confidence in its current performance, to bad – keeps you awake at night!” In a verified, well-documented way for risk safety management purposes.












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