Earthworks Proposal for Underground Car Parking Area Adjacent to Retirement Village

This earthworks proposal outlines the excavation, drainage, and monitoring processes required for the construction of an underground car parking area adjacent to a retirement village. The proposal includes information on the effects of seasonal changes, access to the site, temporary accommodation and construction facilities, and the installation of perimeter sheet piles. The proposal also includes information on monitoring devices, dewatering wells, and the establishment of truck parking and settlement pond access.

Earthworks for underground car parking
area adjacent to the retirement village
with dimensions approximately 55m by
15m by 4m deep, designed for 30 cars.

This earthworks proposal
has been prepared for the
construction of an
underground car parking
area adjacent to the
retirement village
dimensioned 55m by 15m
by 4m deep, designed for
30 cars.
Location: Oran Park Precinct,
Camden
Source: Douglas Partners

Earthworks activities that will be
carried out in the construction of
the named project will include:
• Establishing access into the
underground car parking site
• Installation and upgrade of
current drainage systems and
settlement ponds
• Excavation and removal of
unstable soils
• Provision of temporary
construction facilities
• Current data available of the site
Various earthworks undergoing in a site
Source: Douglas Partners

Effects of seasonal changes
This section will address how the
effects of seasonal change will be
dealt with. The earthworks
activities will be categorized into
two major activities: removal of
unstable and aggressive soil and
filling the site with aggregate
material.
This process that involves
removing all unstable soils from
site generally involves excavation,
windrowing and offloading of all
the unstable soils. All the
excavated soils are required to be
windrowed within a period of 9
days after which they shall be
offloaded from the site by a truck.
These excavation works are
strictly weather dependent and
are required to be done in the dry
season.
Areas with saline and mineral soils marked as
orange
Source: Douglas Partners

Areas with aggressive
soils within a depth of
1.5m marked as
green
Source: Douglas Partners

Site works
All earthworks contained in this proposal will be carried out in the following sequence:
• Installation of drainage system
• Upgrade access to the site
• Installation of sheet piles
• Actual excavation
Access
The current access route to the area is by road. Since the current site is an open field, demarcation of new
access routes will be important. The access route will be compressed and hardcore poured to allow ease of
movement for trucks.
View of the current site and the main access highway. Source: JBA

Temporary accommodation and construction facility
The necessary temporary accommodation will be set up. It
will include welfare activities for the earthworks staff,
storage for the required machinery and a meeting room for
the contactor. Furthermore, this facility will function as a
temporary building facility that will contain the site office
and meeting room which will function as storage and
administrative facilities.
Monitoring
Monitoring devices will be installed on site before the
commencement of any earthworks to ensure that the
groundwater levels and ground movement are continually
monitored. This is due to the presence of unstable and
aggressive soils on site. The monitoring devices for this
proposal include inclinometers, settlement plates and
piezometers.
Inclinometer piezometer

Dewatering wells
One dewatering well will be drilled adjacent to the site to assist reducing groundwater levels, increasing the
workability of the ground soil. This is mandatory especially in areas that are detected to contain mineral
soils so as to increase workability during excavation.
Establishing Truck Parking
In conjunction with upgrading the main access to the site, a parking area will be located adjacent to the
western edge of the site. The parking bay for the trucks will be comprised of ballast that is poured atop of
compressed ground. This parking will provide the prerequisite haulage that will function both as storage
and parking. The temporary truck parking will from part of the underground parking eventually.
Establishing settlement pond access and location
After the construction of the main access to the site, the location for the settlement pond will be
determined and its access is determined. The one access will be provided from the main access channel to
the settlement pond.

Initial excavation of the unstable soils
The unstable soils will be initially removed from
the eastern edge of the site and gradually
progressing towards the western boundary
following the southerly direction.
As excavation continues, the area containing
mineral soils will be excavated last to ensure
workability during windrowing. Windrowing will
consist of excavating the unstable soils from the
existing grounds and placing them in linear
stockpiles (windrows) that will range at an
approximately height of 3.5m at the center of the
pile. The windrows will be placed in a line from the
northern edge of the site to the southern edge of
the site. The mineral soils should be dry enough
after being excavated and added to the windrow
to achieve the quality for loading into the trucks
after which its carried for deposition.
This initial excavation is projected to take a period
of 10 days, while windrowing is projected to take a
week to complete. The daily offloading rate is
required to be 3000m3 .
Excavated and compressed
site with settlement plates
Source: USGS Publications

Installation of perimeter sheet
piles
Piles will be placed along the
perimeter of the setting out points
for the underground parking. The
function of the sheet piles is to
retain and hold back soil and water
during earthworks and
construction. The sheet piles
should be interlocked during
placement to form a continuous
wall that will have no leakages.
Perimeter sheet pilesSource: Wynyard Quarter

References
Burch, D., 1997. Estimating Excavation. London: Craftsman Book Company.
Department, N. D. P., 2018. NSW Government. [Online]
Available at:
http://www.planning.nsw.gov.au/Plans-for-your-area/Priority-Growth-Areas-and-Precincts/South-West-Grow
th-Area/Oran-Park
Maginn, P., 17 Feb 2012. Planning Australia: An Overview of Urban and Regional Planning. London:
Cambridge University Press.