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CROSS Safety Report

Concern about foundations to telecoms masts

Report ID: 690 Published: 1 January 2018 Region: CROSS-UK

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Overview

Concerns are raised about a potential safety problem with the design and construction of ‘root’ foundations for telecom poles.

Key Learning Outcomes

For construction professionals:

  • The robustness of a planted foundation depends on the workmanship achieved during installation. Supervision and inspection by a competent person on site can ensure a suitable standard is achieved.

For asset owners:

  • It is good practice to periodically monitor existing monopoles, particularly those whose failure might impact an adjacent building or facility

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Whilst recognising the attractiveness and value that is offered to the industry a reporter writes about a potential safety problem with the design and construction of ‘root’ foundations for telecom poles.

Several concerns raised

The reporter's concerns are:

  • The telecommunications industry, apart from planning requirements, is self-regulating
  • The industry is highly competitive, which may be an incentive for some to cut corners
  • The major companies distance themselves from the risk of failure by placing the onus for safety on the construction/contracting companies
  • Monopoles of up to 20m in height are being, and have been, erected in their thousands close to roads and railways on root foundations. If such a pole falls across a road or railway line, then lives could be lost.
  • Some are built at the back of footpaths so that on the side nearest the road there is often weak backfill to service
  • Trenches for power supply cables to the poles may be filled with gravel to facilitate drainage. Rainwater runs down the poles and pumping action due to wind forces may leave voids at the top of the root as material is displaced.

Monopoles of up to 20m in height are being, and have been, erected in their thousands close to roads and railways on root foundations. If such a pole falls across a road or railway line, then lives could be lost

The roots are designed, according to the reporter on the basis of PD6547 (PD 6547:2004+A1:2009 Guidance on the use of BS EN 40-3-1 and BS EN 40-3-3) which is an advisory document for street lighting. The designers of root foundations have, says the reporter, adopted what suits them in PD6547 whilst ignoring other aspects.

By imparting this knowledge to others, the reporter hopes that the risk may be evaluated and any appropriate action if any might be taken before a tragedy occurs.

Expert Panel Comments

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The requirements in PD 6547 – 2004 for planted foundations are a carry-over from an earlier version of EN40 (BS5649-2 – 1978, aka EN40-2).  When EN40 was revised, the requirements were dropped in Europe, but the UK did not want to lose them, so they continued to be referenced in documentation.

CROSS’s concerns are:

  • The robustness of a planted foundation depends on the workmanship achieved during installation. Given the cost of a monopole, there may not be sufficient site supervision in place to guarantee that a suitable standard is achieved.

  • A PD contains guidance and is not a British Standard. This creates a problem for public clients who cannot then refer to a PD as a specification. They may suggest that application of the PD constitutes the default method of compliance with the Eurocodes or Euronorms.

  • Private clients may do what they want, but often lack the technical know-how to say what is needed (and the value of a single monopole deters them from taking advice from an expensive consultant) 

  • The rules were originally introduced for lighting columns (the majority of which were in the 6m to 8m tall range). The same rules are now being applied to 20m tall monopoles with bigger head loads. There may therefore be an issue with extrapolation.

A PD contains guidance and is not a British Standard. This creates a problem for public clients who cannot then refer to a PD as a specification

The advice given by the reporter for caution and proper risk assessments on new installations should be heeded. Existing monopoles should be monitored periodically, particularly those whose failure might impact an adjacent building or facility.

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