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National Environmental Standards for Electricity Transmission Activities: project examples of application (6 of 7)

Activities that may make up a transmission activities project:

  1. Relocation of poles to enable roading development
  2. Access track and mid span earthworks
  3. Work on towers involving rivers
  4. Undergrounding
  5. Adding a circuit
  6. Tower foundation cleaning and painting
  7. Thermal uprating on a 220kV double-circuit transmission line

Tower foundation cleaning and painting

Project description: Transpower proposes to undertake foundation refurbishment of 405 transmission towers on three separate lines in the upper North Island. The tower steelwork to be treated is 300mm above ground to approximately 1000mm below ground.  Three of the towers are within the coastal marine area (CMA).

The foundation refurbishment work involves:

  • excavation around the tower legs to a depth of up to 1 metre, to give a working area of several square metres
  • erecting containment tarpaulins around the working area
  • dry abrasive blasting of the tower leg steel and base plate with garnet steel from approximately 300mm above the ground surface, to 800 to 1000mm below the ground surface. 
  • application of a hot zinc spray to the exposed tower steel, and then sealant to the painted steel
  • restoration of the ground after works completion.
Main activities Status under NES
Dry abrasive blasting of tower foundations Permitted by regulation 25(1) provided that the following conditions under regulation 25(3) to (9) are met:
  • The blasting is not done within 50m of a road, water body or coastal marine area or within 100m of an occupied building.
  • The material used in blasting does not contain more than 5% free silica.
  • Waste and debris is collected.  Special conditions apply where lead paint was used.
  • Dry abrasive blasting is done no more than 1m above the ground, and screens are used.
  • None of the listed substances are used for surface preparation.
Applying hot zinc coating to foundations Permitted by regulation 25(1), provided that the coating is applied by hand; pressurised spray may be used, but not more than 1 metre above the ground – regulation 25(10).
Excavation around foundations This is permitted by regulation 33, with the following provisions:
  • Earthworks are not carried out in beds of lakes and rivers or the coastal marine area.
  • If the tower is in a natural area, no more than 50m3 of earth is disturbed. 
  • Conditions relating to preventing erosion and restoring the area must also be met.
  • Earthworks must not be carried out on potentially contaminated land or in a historic heritage area, unless an archaeological permit has been obtained.
If these conditions are not met, the earthworks will be controlled under regulation 34.
Excavation around three tower foundations in the CMA This is controlled by regulation 34 as both the conditions in regulation 33(8) and (9) are not relevant.
Dry abrasive blasting of three tower foundations in the CMA This is restricted discretionary – regulation 27.
Other potentially relevant activities Status under NES
Noise from machinery Noise from machinery is permitted by regulation 37 provided it meets the limits in NZS6803:1999 Acoustics Construction Noise.
Discharges to water Permitted under regulation 28 provided conditions (2) to (6) are met.

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Last updated: 18 January 2010