Hydrographic Surveying Example Project

Client: POWERCO-TENIX ALLIANCE (0623)

Project: 11Kv Submarine Power Cable Installation – Tairua – Pauanui

Task: Powerco-Tenix contracted LMS to undertake an as-built hydrographic survey of the under-sea cable from Tairua to Pauanui.

The survey was conducted using RTK GPS with lead-line soundings taken to obtain a seabed profile along the alignment of the as-laid cable. The equipment & personnel were deployed aboard a small vessel hired from Discovery Marine Limited – Mt Maunganui

The cable-laying contractor had previously marked the cable alignment with buoys (plastic bottles) attached to tethers that were tied to the cable during the laying phase.

In places the cable and trench were still visible in water depths up to 4m.  The cable was trenched to an approximate depth of 1m below the seabed.

Deliverables:

• Hydrographic survey profile of seabed along cable route
• Nautical data in WGS-84 datum sent to LINZ Wellington
• AutoCAD drawings showing the relationship of the as-laid cable to property boundaries and physical ground features

Land Marine Surveying Equipment:

• Sokkia GSR2700IS RTK GPS
• Nikon NPL- 632 Reflector-less Total Station