Refined Modelling Confirms Silverstream Floor Levels at Correct Height

Published: 01-Jul-2019

Waimakariri District Council last week sent letters to home owners in parts of Silverstream who believe the floor levels of their properties had been built to the incorrect height due to utilising incorrect survey data.

When the subdivision was consented in 2012 a survey of the relevant area was used to set temporary benchmarks throughout the development.  These temporary benchmarks were used to set the requirements for minimum finished floor levels (floor heights) - one of the main protections against flooding. 20190701 - Silverstream East

These floor height requirements are based on various modelling scenarios, which recommended a level between 4.3m and 4.4m depending on the individual property.

In 2016 an independent building company surveyor found irregularities with the 2012 temporary benchmarks which suggested there were homes which had been built with floor heights lower than the requirements.

Since then, Council has been working with independent consultants to refine and update the flood behaviour modelling used at the time of building consent within Silverstream. This was done to address residents’ concerns and to determine whether properties met the requirements with respect to floor heights relative to modelled flood levels. This included surveying every individual house to ensure specific detail could be provided to each homeowner.

The latest modelling, reviewed by experts independent of Council and independent of the subdivision, shows that there are no properties within subdivision with floor heights lower than the requirements.

Relevant property owners have been written to by Council with specific  information for their property detailing compliance with the requirements for the floor height of the house.

This type of land information is commonly collected and stored on property files by Council. Also it is utilised by Council in the preparation of a Land information memorandum (LIM). LIMs are regularly requested by intending home buyers.

Council’s Manager of Utilities and Roading, Gerard Cleary says he would like to thank the relevant property owners for their patience while the modelling was being further refined.