Geotechnical Engineering

We provide a range of initial geotechnical assessments to inform early project decisions and streamline the planning process: Pre-purchase/Initial Geotechnical Assessments: These assessments assist clients in understanding potential geological and/or geotechnical constraints on a property before purchase or land development. Reports present site observations, anticipated subsurface conditions, and a preliminary geotechnical assessment based on a desktop study, historic aerial images, and site walkover observations. Feasibility Geotechnical Assessments: Normally carried out to support subdivision Resource Consents, these assessments aim to demonstrate the suitability of potential building areas post-subdivision. They typically begin with a desktop and geomorphologic assessment, with further preliminary geotechnical investigations and stability analysis where risks are identified. Reports provide anticipated subsurface conditions and preliminary geotechnical recommendations. Geotechnical Desk Studies: These geotechnical desk studies review published and unpublished information for a site as an initial step, helping to identify potential geotechnical or geological constraints for large developments.

Our core service involves detailed geotechnical investigations and expert geotechnical reporting, providing the foundation for informed design: Geotechnical Investigation and Reporting: Our geotechnical reports, sometimes referred to as good ground reports, are commonly required for Building Consent applications for proposed new or relocated dwellings, sheds, garages, additions, and other structures to inform civil and structural design. Reports are prepared using site-specific investigation data to provide geotechnical recommendations for the proposed development. Foundation Recommendations: Our geotechnical reports provide foundation design parameters and foundation recommendations based on site-specific geotechnical investigations, aiming to meet the requirements of the New Zealand Building Code. These are utilised by designers or structural engineers where specific engineering design is required. Earthworks Recommendations: Development of most sites includes some form of earthworks. Our geotechnical reports provide earthwork recommendations to inform earthworks design, including fill batter slope angles, cut slope angles, and can incorporate retaining wall design recommendations. Slope Stability Analysis & Retaining Wall Design: For development on sloping sites, VISION's geotechnical services include slope stability analysis carried out using specialised software to assess pre-development and post-development conditions. Where required, this includes recommendations for slope stabilisation measures to reduce the risk of slippage and address slope failure repair methods. We also provide geotechnical assessments on the stability of earthworks. Additionally, our geotechnical reports provide expert recommendations for retaining wall design, offering crucial guidance for slope retention solutions.

We conduct thorough assessments and testing to accurately determine ground conditions: Ground Condition Assessment/Testing: This involves site investigations to determine ground conditions, including inspections and various soil testing for timber pile foundations, ground conditions in pile foundation holes, and retaining wall pole holes. We also provide Producer Statements for ground conditions, including specific aspects like ground bearing capacity tests. Investigation and Remedial Solutions: VISION can undertake site investigations to identify the probable cause of seepage into structures and provide remedial solutions.

VISION conducts geotechnical construction monitoring to observe and confirm that the ground conditions present at a site are consistent with the findings of the geotechnical report and approved plans. This helps to support construction quality and compliance. Our monitoring services include: - Inspecting pile foundations before the placement of piles and concrete, and checking soil conditions, size (diameter), and depth of footings before concrete is poured. - Monitoring ground conditions in strip footings and retaining wall pole holes. - Monitoring subgrade before the placement of hardfill, and monitoring the compaction of hardfill. - Consulting with the structural engineer regarding geotechnical confirmation. - Carrying out construction monitoring to a CM3 level for ground conditions within pile hole excavations, reviewing random samples of important work procedures for compliance with plans and specifications. -Providing Producer Statement 4 (PS4) for ground conditions.

We provide focused assessments for specific geological hazards, including liquefaction potential analysis, fault line assessments, and detailed erosion vulnerability studies, to inform safe and resilient development in areas of specific risk.

Beyond initial feasibility, we provide comprehensive geotechnical input and supporting documentation required for various Resource Consent applications, streamlining the consenting process for your development.

We provide essential services for identifying and monitoring ground movement and landslips: Measuring ground movement using inclinometers installed at a property, taking baseline and subsequent periodic readings. Conducting visual assessments of properties for signs of movement, such as tension cracks, headscarps, and movement of fences. This monitoring is conducted periodically (e.g., 6-monthly) and includes familiarisation with previous monitoring reports and providing letter reports outlining site observations and recommendations. VISION has extensive experience in landslip investigation and monitoring, and a track record of assessment, design, and construction supervision for land subsidence sites. We also conduct landslip damage and settlement assessments on behalf of insurance companies, private clients, and the EQC.

We offer specialised groundwater monitoring services, like measuring groundwater levels in standpipes installed as part of investigations. Measurements are typically taken one week following the installation of the standpipe and periodically thereafter as required for project or site assessment.

For complex projects or where an independent check is required, we provide expert geotechnical peer review services for designs, reports, and methodologies prepared by other consultants, offering an independent assessment to enhance project robustness.