RIV_2600294 Ashley Rakahuri Stopbank Upgrade Investigation

Summary

CRC seeks a provider who has experience with geotechnical investigation and designing stopbanks and flood protection schemes. We have completed the hydraulic modelling in house. Hydraulic modelling results files (i.e., water surface elevation, depth, velocity, etc) will be provided by Environment Canterbury for this work. The provider needs to provide an initial geotechnical assessment (Part A), then a detailed geotechnical investigation including necessary augering and test pitting (Part B). Part B also includes the geometric design of stopbank crosssections, volume analysis and a risk based geotechnical review of the existing stopbanks with recommended remediation to be undertaken with the upgrade. A volume analysis is required to cover all stopbank materials including quantities of culverts that may require extension. We have recently completed CCTV survey inspections of all culverts that cross the stopbank scheme in this area and will provide the results of these to assist with this work. The provider needs to take a risk informed, pragmatic approach to the investigation. The primary risk is considered to be erosion of the stopbank during a flood, so the investigation and design should be undertaken with this in mind along with considering other failure modes. It may not be possible to provide the optimal engineering solution to the whole scheme, so we need to know where the higher-risk sections are and what our options for the future might be. What we do not want/need At this stage we do not anticipate hydraulic modelling will be required by the provider. Results files from the HEC-RAS 2D model developed by Environment Canterbury will be provided including water surface elevation, depth, and velocity.