The house on the subject site had been constructed by others cutting in a building platform into a steep, bush clad slope and was subject to multiple problems – unauthorised diversion of a natural watercourse, uncertified fill, suspected piping of stormwater runoff through this fill and multiple overland flowpaths impacting the house itself during heavy rainfall. The new owner gradually became aware of these problems and decided to seek redress through legal action.
Fraser Thomas provided multi-disciplinary engineering services, including the following:
- Stormwater investigation, catchment analysis and modelling using HEC-HMS and HEC-RAS software; detailed concept design of stormwater control and conveyance remedial measures, including appropriate erosion/stabilisation measures;
- Geotechnical field investigations and geotechnical/structural design of remedial works;
- Costing of geotechnical, structural and stormwater mitigation works and of future professional fees for detailed design, consenting and construction observation.
The proposed solution involved substantial retaining walls on two sides of the house, one with a debris capture barrier, and collecting stormwater runoff from upgradient catchments and diverting it away from the residential dwelling. This was achieved by incorporating engineered concrete dish drains along the top of the proposed retaining walls and upgrading a portion of the eastern channel into an engineered channel with stabilised base and sides.
Subsequent work involved the preparation of expert evidence for a High Court hearing covering the above and reviewing the process followed by Council in processing the resource and building consents against RMA and Building Act requirements; expert conferencing mediation meeting and conferencing statement; attendance at High Court with the case being settled on the first morning of the hearing, with the plaintiff being awarded costs in the six figures as well as general damages, expert costs and legal costs on the High Court scale.