Before a contractor starts working with us, we want to know they are a safe company that has good systems, capability, and is backed by credible evidence. Prequal is one of the first steps for selecting good Contractors.

We use Prequal NZ, an assessment subsidiary of Impac, to give us an assessment report with a percentage score of a contractor. Prequal NZ is widely used by NZ's largest companies, and a contractor can simply supply their prequalification to other companies they do business with. Prequalifying safe and good Contractors are major steps of the Principal's Guide to Contracting to meet Health and Safety Legislation.

All third parties who do physical work and/or high-risk work for us must be prequalified and meet a minimum required score of 60%. If a contractor scores between 60% and 80%, additional controls must be put in place to ensure contractors have the support they need to work safely.

It can take some time for both contractors and Prequal NZ to work through the requirements. New Contractors should give their safety evidence to Prequal NZ about 3 months before a tender closure date. It takes Prequal NZ around 2 months to assess their evidence. See their FAQs.

It is our intention to adopt the Tōtika prequalification scheme in 2022. This will reduce the number of prequalification assessments a contractor needs to complete in order to work for different clients, such as Wellington Water. This scheme recognises ISO45001 and other certifications in replacement of a third party prequalification assessment.

We have made steps towards also allowing ISO45001 to be used in place of Impac’s prequalification assessment. If you would like to make use of this exception please contact our Health and Safety Team for formal approval. As of December 2020, only four parties have been approved to use other evidence in place of Impac’s prequalification scheme.


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Prequal Renewal Times

Contractors need to renew every 6 to 24 months depending on their score. The re-submission criteria is exactly the same as the first time. So it pays to have good safety and get a high score early on.

0 to 30% need to renew within 6 months

30 to 60% need to renew every 12 months

60 to 100% need to renew every 2 years

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  1. We inform prospective contractors of our H&S requirements in our communications and tender documents
  2. We inform Prequal NZ that there is a non-prequalified yet prospective contractor
  3. Prequal NZ does the 'leg work' and guides the contractor in the assessment process
  4. The contractor provides their H&S evidence and information to Prequal NZ to assess
  5. Prequal NZ assesses the contractor
  6. Prequal NZ gives a score of the contractor, and provides Wellington Water the score too
  7. We use this prequalification score together with other scoring attributes (e.g. pricing, past performance) in the contractor's tender