A PPT on Site Clearance

1. Building Methods & Construction
Technology
Site Clearance

2. Tutor Copy

3. Groundworks
Typical groundwork activities include:
• Site clearance.
• Site preparation.
• Excavation of foundation trenches.
• Groundwater control.

4. Site Clearance
It is normal practice for any above ground
clearance requirements, such as removal
of trees, bushes, walls, slabs, buildings etc
to be shown on a site plan. This plan may
show the position of services, both above
and below ground, allowing these to be
cleared if necessary or avoided for safety
if to be left alone.

5. Site Clearance
Construction sites vary a great deal, and clearance
procedures will, of course, be different on each one.
A Greenfield site out of town may only require soil
removal.

6. Site Clearance
Whereas a Brownfield
site, having been
previously developed,
may need extensive
demolition and
clearance of concrete
slabs etc before any
excavation can
commence.

7. Contaminated Ground
Due to the increase in use of brownfield
sites, and regulations imposed by the
government, many sites have to be
decontaminated before structures can be
built on them. This often involves the
contaminated soil being totally removed
from site and being replaced by clean soil
when the site is landscaped.

8. Protection of Trees
Trees may have a ‘preservation order’ placed on
them by the local authority. This protects the
tree from displacement or removal. The removal
of other trees generally is subject to agreement
with the planning authority before the work on
site commences (usually at planning stage).

9. Removal of Waste
Waste material can be removed by lorry or
skip to a licensed landfill site, or if the
waste is inert, such as brick rubble or
subsoil, it can be used as ‘fill’ in certain
earthworks. This will generally reduce the
cost of removal of the waste to the
contractor.
Burning of rubbish on building
sites is not normally allowed.

10. Removal of Waste
On brownfield sites, where masonry and
concrete demolition is required, it is often cost-
effective for the material to be crushed and
used for hardcore in the contract (if acceptable
to the architect and building control).

11. Removal of Vegetable Soil
The Building Regulations Part C states that
the ground to be built upon must be reasonably
clear of vegetable soil and matter.
This photograph shows the organic vegetable or topsoil
layer on top of the lighter coloured subsoil below.

12. Reduced Level Excavations
Grading and levelling is carried out by the
use of any of the following methods:
• Cut.
• Cut and fill.
• Fill.
‘Cut’ is the process of removal of high
ground to produce a level work area. This
method results in a solid and compact
base.

13. ‘Cut and fill’ techniques are used to provide
a level base for construction on sloping sites
This method requires compaction of filled
areas of soil, in layers. The soil for filling may
be ‘won’ from the cut areas. The cut area will
be already sufficiently compact.
Cut Fill
Natural slope of the land.

14. Trench Excavation
Factors that influence the choice of methods for
excavation include:
• Volume of subsoil to be excavated.
• Nature of the site.
• Type of soil (e.g. stone requires mechanical
excavation).
• Time constraints (how much time
available for excavation).
• Safety of operatives

15. Trench Excavation
Manual or Use of Plant?

16. Or would this be
better?

17. Sometimes this may be required.

18. All services below ground should
be protected and identified by the
following methods:
Service providers should also have plans and
information on where the location of pipes and cables
are before you start digging!

19. Groundwater Control
Water can be classified as either:
• Surface water.
• Ground water.
• Subsoil water.
Rain, snow etc
on the surface
Water table
Upper level
of water
held in the
subsoil
Surface water –
run off from the
surface
Subsoil water –
water held in the
ground below
the water table
Ground water –
water held in the
subsoil

20. Problems Caused by Subsoil
Water
The contractor must, therefore, resist the
ingress of water into excavations as much as
possible. This is typically done by employing
pumps.
A vacuum piston pump being used to reduce ground water from an excavation