Excert
"A vast number of trench’s are constructed every day throughout the country with a low percentage of failures occurring. It is however important due to the complex nature of the potential rescues that we are correctly informed and prepared.
So what is a trench? The definition given by The Trenching Practice carried out on behalf of CIRIA is “an excavation forming a structure as a result of digging, lifting and removing earth, fill or other materials from the ground. The purpose of which may be to form foundations, install services, drainage etc”
A trench by law need not be supported as long as the depth does not exceed 1.2m, the ground is self supporting and a safe working method can be employed. Over 1.2m alternatives to trenching should be considered and a suitable support system designed by an experienced person should be
employed.

In a study of fatal accidents in trench’s in the period 1973 – 1980 it showed that:

63% of deaths were due to unsupported excavations
20% of deaths were due to working ahead of the support system
14% of deaths were due to inadequate support systems
3% of deaths were due to unstable slopes of open cut

It also showed that 35% of all the above cases occurred in “made” ground or ground which had been disturbed by previous earth works

Further to this a recent HSE report from 19th August 2004 gave the following fatal statistics for accidents involving trench’s:

Year Fatal
97/98 0
98/99 1
99/00 0
00/01 1
01/02 1
02/03 2
03/04 2
04/05 3

This report is written with the view of providing information regarding the factors affecting trench’s and also how the skills and equipment gained from URST 2 course can be integrated into this field."

The full report is viewable in the attached PDf file.