Safe Quarry - Health and Safety Authority

PART 6 EXCAVATIONS INCLUDING (QUARRY FACES), TIPS AND LAGOONS
50.1 Design of Excavations,Tips and Lagoons
When a new tip, excavation or lagoon is to be
created it is necessary to carry out planning and
design to ensure it can be developed without
becoming a significant hazard both during its
construction and during its subsequent use. To
ensure that all hazards have been evaluated it will
be necessary to carry out a site investigation.
A site investigation should include any relevant
historical information about the site and its
surroundings and should be carried out before
starting a new excavation, tip or lagoon. The
purpose of this is to ensure a design which is safe
and enables safe operation. See Schedule 3 of the
Regulations at Appendix 3.
If all relevant data is not available or is not reasonably
accessible additional investigations may be
required or extra caution may be required to be
built into the design, particularly if the information
is critical.The design should conform to good
engineering practice and relevant standards.
Slopes should be so designed to provide stability
throughout their life. The risk of failure of the
excavation, tip or lagoon should be assessed to
ensure the design provides an adequate margin
of safety.
The excavation, tip or lagoon may need to be reassessed
and redesigned as a result of information
obtained during routine working, inspection,
appraisal or geotechnical assessment. Simple
management procedures are, therefore, needed to
ensure that any such information relevant to the
design is reviewed.
Where an appraisal of an existing excavation, tip
or lagoon indicates that there could be a concern
that may constitute a significant hazard at a later
date it may be necessary to carry out a site investigation
if such information is not already available
in order to ascertain if a geotechnical assessment
is required.
Where a proposed excavation, tip or lagoon is
likely to constitute a significant hazard and will
require a geotechnical assessment it is strongly
recommended that a geotechnical specialist is
involved in the design stage. In such cases, the
original design, appraisal and assessment may be
amalgamated and the design documentation may
form the assessment report provided it addresses
all the relevant matters covered by Schedule 3 of
the Regulations.
The maximum safe height of excavated faces is
influenced by the geology and physical properties
of the material, the size, height and type of
machinery and working methods used. However,
where the face height exceeds 20 metres a
geotechnical assessment is required. Generally,
the lower the face, the easier it is to safely manage
and maintain it. In operations involving unconsolidated
materials the height of the face should be
based on risk assessment which includes the
physical properties of the materials worked,
particularly its natural angel of repose and the
extraction methods used.
Figure 38: Horizontally bedded strata
Figure 39: Steeply dipping strata
SAFE QUARRY GUIDELINES TO THE SAFETY, HEALTH AND WELFARE AT WORK (QUARRIES) REGULATIONS 2008 71