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#1 Posted : 16 May 2018 20:08:53(UTC)
Rank: New forum user

Can anyone point me in the right direction for guidance on excavating a trench for HV cable diversion.

Mark out line of excavation. Mechanical excavation, Hand dig within 1.5m of identificd services.

I am ok with the services location side of things but im struggling on the 900mm depth and the methods adopted considering trench collapse. Expecting depth to be determined by the utilities company but i have assume 900mm at this stage. Width will be assume to be approx 1m?

Excavated spoil to be stockpiled 1.5 x depth away from trench in normal soil conditions

I am aware that the 1.2m rule for trench support is out the window and its based on soil and weather conditions.

At this stage I am must assuming made ground.

Just feel like I am still missing something.

Any comments or feedback appreciated.

#2 Posted : 21 May 2018 13:29:37(UTC)
Rank: Super forum user

Charlie, it is my understanding that only hand digging within 500mm of service is recommended. You are correct that the substrate and prevailing weather conditions will be the main determining factors for the trench support. I suggest you review HSG 47 for further info. 


#3 Posted : 23 May 2018 11:56:14(UTC)
Rank: Forum user

HSG47 is a useful document, but if you are looking at guidance on depths, support requirements and techniques then the Construction Health and Safety Manual series published by: Construction Industry Publications Limited are really usefull publiciations.

Volume E is specifically focused on excavation and goes through in detail for example:

  • soil types and angle of repose
  • support arrangements including measurements for the ground conditions etc.

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