Car Park Design, Observation and Certification

The Canterbury earthquakes caused significant damage to the Mt Pleasant Community Centre buildings, leading to their demolition and a decision by the Mt Pleasant Community Centre and Residents Association to redevelop the site and build a new community centre. Fraser Thomas Ltd was engaged to provide civil engineering design, geotechnical and contaminated site investigations, structural design, and surveying for the car park and arrival plaza components of the new development.

This project posed many challenges and, despite multiple preliminary investigations completed by other consultants, provided unexpected ground conditions, including:

  • The presence of historic fill and some refuse material, believed to be associated with filling of the wider area encompassing the site in the 1940s associated with the reclamation of land off McCormacks Bay. Fraser Thomas carried out soil sampling in affected areas and advised the contractor of contaminated soil disposal requirements, after liaison with CCC.
  • The presence of asbestos containing material within the carpark excavation area. Worksafe were informed of this, and a specialist contractor undertook the removal of the asbestos contaminated soil material, with this being verified by validation sampling.
  • Unexpected discovery of two septic tanks, with their contents emptied and the tanks disposed of in accordance with Fraser Thomas instructions.
  • Low CBR value of the sub-grade, and high groundwater level, leading to some design changes. Cement stabilised sub-base was used to compensate for the low subgrade CBR value rather than undercut this weak material, due to possibly exposing additional contaminated fill material and the high groundwater table. Subsoil drains and a bubble-up drainage system were designed to mitigate the impact of high ground water levels on the pavement design.

Expertise provided:

  • Geotechnical
  • Civil
  • Structural
  • Surveying
  • Contaminated Land

Project cycle:

  • Detailed design and building consents
  • Construction observation and trouble shooting (i.e. contamination investigations and design changes)
  • Certification