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.