EXCAVATION AND EARTHWORKS
General
1.1 This Work shall consist of all the required excavation within the limits of the Works. It
shall include the removal and proper utilisation and hauling, or disposal of all excavated
materials, and constructing, shaping and finishing of all earthworks over the entire extent
of the Works, in conformity with the Drawings and this Specification.
1.2 The excavation and earthworks shall be executed in such a manner and order as
approved by the S.O. The Contractor shall be responsible for compliance with by-laws
and regulations relating to earthworks.
1.3 Excavation in rock and/or hard material shall respectively be measured and paid for as
extra over to excavation and earthworks in accordance with the Provisional Bills of
Quantities. The Contractor shall give reasonable notice to the S.O to examine, classify
the excavation and to take measurement prior to breaking up. For contract based on
Specifications and Drawings, unless otherwise provided in the Contract, for the purpose
of pricing the excavation and earthworks, the whole excavation shall be assumed to be
without rock and/or hard material as defined hereunder.
1.4 For contract based on Quantities, the pricing shall be in accordance with the Bills of
Quantities.
1.5 Computation of volume of rock excavation for payment shall be based on nett volume
excavated as indicated in the Drawings.
Site Clearing
2.1 The whole Site shall be cleared to the extent as shown in the relevant Drawings. These
shall include clearing, grubbing and removing all trees, shrubs, vegetation and butts; and
clearing, demolishing, breaking up and removing all structures above ground level such
as buildings, walls, fences and other obstruction within the Site which have been
designated to be demolished or removed. All spoil and debris shall be removed and
disposed off as approved by the S.O. in accordance with Environmental Quality Act 1974
(Act 127) and Regulations.
3. Preservation of Existing Trees
3.1 The Contractor shall take precaution to protect from damage, all existing trees and
shrubs which are designated to be preserved as specified under SECTION N.4:
LANDSCAPING AND TURFING.
4. Demolition of Existing Structures
4.1 Any existing structures and other obstruction which are designated to be removed shall
be demolished, broken up, removed and disposed as approved by the S.O.
4.2 All salvaged materials arising from the demolition work shall, unless otherwise specified,
become the property of the Contractor, and shall be removed from Site as soon as
possible.
Excavation and Earthwork
5. Relocation of Existing Utilities and Services
5.1 The Contractor's attention is specially drawn to his responsibilities under the Clause
headed ‘Damage to Property' of the Condition of Contract.
5.2 Before commencing on any excavation, the Contractor or his representative shall
accompany the S.O. on a site inspection to identify the presence of underground cables,
water or other service pipes at or in the vicinity of such excavation. Thereafter, the
Contractor shall carry out the excavation work in a manner and sequence as approved by
the S.O.
5.3 If during excavation, the Contractor's workmen uncover any cables, water or other service
pipes, work shall be stopped immediately and shall not be again started until the matter
has been reported to the S.O. who will notify the appropriate local authority, and
subsequently issue whatever directions he deemed appropriate.
General Excavation
Excavation shall be divided into two categories i.e. common excavation and hard material/ rock
excavation. Payment on excavation is to be made based on the method and equipments used.
6.1 Common Excavation
6.1.1 Common excavation shall mean excavation in any material other than hard
material/ rock excavation.
6.2 Hard Material/ Rock Excavation
6.2.1 Hard material/ rock excavation shall mean excavation in any material that cannot
be loosened by an excavator with a minimum mass of 44 tons and a minimum
rating of 321 BHP. The excavator shall be in good condition, and operated by an
experienced personnel skilled in the use of excavator equipment.
Hard material/ rock excavation shall require one or a combination of the following
methods:
i. Excavation using track excavator exceeding a mass of 44 tons and 321
BHP rating.
ii. Ripping using a tractor unit of minimum weight of 37 tons and 305 BHP
rating and a ripper attached.
iii. Excavation using hydraulic rock breaker.
iv. Excavation using pneumatic tool.
v. Open blasting
vi. Controlled blasting.
Excavation of boulders of individual mass less than 0.5m³ shall not be
considered as rock but as common excavation.
6.2.2 Trial Excavation
If it is apparent that common excavation as per clause 6.1.1 cannot be carried
out, than the S.O may instruct the Contractor to submit his method statement to
the S.O., based on his proposed method of excavation for approval. A trial
excavation shall be carried out to verify and confirm the proposed method of
excavation. The trial excavation shall be witnessed by the respective
representatives of the Contractor and S.O. In the case where the method
statement is rejected by the S.O., the Contractor shall submit a new method
statement to the S.O. and the whole process of trial excavation shall be repeated
to enable the S.O. to consider the new method statement for approval.
6.2.3 Method of Measurement
Levels shall be taken before and after excavation, to calculate the volume for
each method of excavation. Levels taken shall be subject to approval by the S.O.
The levels taken shall be certified by the representatives of the Contractor and
S.O, respectively. For determination of the volume of boulders, diameters in
three orthogonal directions shall be taken at 2m intervals or lesser. The average
of the three diameters shall be used to calculate the volume of boulder. Records
of measurements and photographs shall be taken and kept to support the
calculation of the volume of excavation.
6.2.4 Mechanical Equipment In ‘Good Running Condition’
Prior to the execution of trial excavation, the Contractor shall furnish the following
documents to the S.O as evidence that the excavator is in good running
condition:
i) A copy of the Original Equipment Manufacturer (OEM) performance
handbook or catalogue, with details of the operating weight, BHP and
maximum drawbar pull of the excavator.
ii) Relevant records showing that the excavator has been appropriately and
routinely up-kept and adequately maintained in accordance with the
recommendations of the OEM’s schedule.
Excavation for Foundations, Pits and Trenches
7.1 Foundation trenches, pier holes, etc. shall be excavated to the levels and dimensions as
shown in the Drawings, with sides trimmed and bottoms levelled and stepped as
required.
7.2 All excavation shall be carried down to hard ground. On no account shall foundations rest
on made or filled ground. The depths of foundation shall be decided on the site by the
S.O., but for tendering purposes, unless otherwise shown in the Drawings, the Contractor
shall assume the uniform overall depth 1.5m below formation level. Any variation to such
depth, together with any variation caused thereby to concrete and brickwork, etc., shall be
measured and valued as variations, as provided for in the Contract, and the Contract
Sum shall be adjusted accordingly. The Contractor shall at his own cost and expense,
make good any over excavation below the required depth with suitable material or
concrete as approved by the S.O.
Sides of Excavation
8.1 The Contractor shall ensure that at all times, the sides of the excavation are maintained
in a safe and stable condition, and shall be responsible for the adequate provision of all
shoring and strutting including sheet piling required for this purpose. All temporary works
shall comply with requirements of BS 5975.
9. Excavation To Be Kept Dry
9.1 The Contractor shall be responsible for keeping dry all excavations, whether in open cut
or in trench, so as not to interfere with the work in progress. The Contractor shall, without
extra cost to Government, provide, fix, maintain and work, as and when directed by the
S.O., such pumps, wells, drains, dams and other things necessary to effectively deal with
all water which may collect or find its way into the excavation from any cause whatsoever.
Nevertheless, such directive shall not relieve the Contractor from his liability for any
damage to the Works or adjoining land and property or water courses due to his
Excavation and Earthwork operations.
10. Bottom of Excavation
10.1 Unless otherwise stated, the excavation, whether in open cut or in trench, shall be
proceeded with in such portions at a time as the S.O. may approve, and shall not, in the
first instance, be carried down to a depth nearer than 150mm above the required
excavation level; the last 150mm of depth to the said level shall be carried out by manual
labour immediately in advance of placing concrete.
10.2 Any pockets of soft material or loose rock in the bottom of pits and trenches shall be
removed, and the resulting cavities and any large fissures filled with properly compacted
blinding concrete (1:3:6). The Contractor shall take such steps as and when necessary,
to prevent damage to the bottom of excavation due to exposure to the weather. After the
placing of any blinding concrete, no trimming of the side faces shall be carried out for the
next 24 hours.
Inspection
11.1 The Contractor shall report to the S.O. when the excavation are ready to receive
concrete, and no concrete shall be laid until the excavation have been inspected and
approved by the S.O.
Backfilling
12.1 A portion of the excavated material shall be returned, filled around walls, columns and the
like in 225mm layers and each layer thoroughly compacted using rammers or mechanical
compactors as the S.O. may approve, until compaction is complete. However, only
suitable and approved fill materials shall be returned for backfilling. The surplus
excavated materials shall be deposited, spread and levelled on site or elsewhere as
approved.
12.2 Shoring used for the sides of the excavation shall be withdrawn in stages as the
compaction of backfilling proceeds.
Anti-Termite Treatment
13.1 Termiticide chemicals shall be applied in accordance with the manufacturer’s
recommendation and label instructions prior to the pouring of concrete to construct the
ground slab or for blinding. Notwithstanding the manufacturer’s recommendation, the
minimum surface application rate shall be five (5) litres per sq. meter on all ground floor
built-up areas including apron areas, and also on all areas extending one (1) meter
beyond the perimeter drain all around the building. In addition, termiticide chemical shall
be sprayed on interfaces between the concrete ground beam and the hardcore at a
minimum rate of one (1) litre per linear meter.
13.2 Treatment shall not be performed just before or after heavy rain, unless the area to be
treated can be physically protected to avoid leaching and runoff before the termiticide
chemical has bound to the soil.
13.3 Immediately after spraying of chemical, all surfaces exposed to direct sunlight or rain
shall be covered with an impervious black PVC sheet of minimum thickness of 0.08mm to
reduce the loss of chemical by UV light, alkaline wet concrete, leaching and runoff
caused by rain on exposed treated soil. In the case of areas receiving blinding, the
coverings shall be removed immediately prior to the placement of the blinding concrete.
13.4 As soon as practicable after the completion of anti-termite treatment and prior to the
issuance of the Certificate of Practical Completion, the Contractor shall submit to the
S.O., the anti-termite treatment specialist’s Guarantee against any termite attack to the
Works which may arise during a period of two (2) years from the date of Practical
Completion of Works due to any defect, fault or ineffective anti-termite treatment. The
terms of the Guarantee shall be such as shall be approved by the S.O.
Cut and Fill To Formation Level
14.1 General
Area for buildings, open spaces, fields, roads and footpaths shall be cut and filled to the
required formation levels and grades as shown in the Drawings. Trimming and forming of
banks shall be to the profiles as shown in the Drawings or as directed by the S.O. All
ditches, ponds or wells that are to be filled shall first be excavated to remove all soft spots
if so directed by the S.O. All excavated materials shall be removed from Site and the
depressions including holes resulting from the grubbing of tree roots shall be filled with
approved fill materials and well compacted. Unless otherwise provided in the contract, if
the fill materials obtainable from Site are insufficient, the Contractor shall at his own cost,
obtain such materials from outside source.
14.2 Fill Materials
14.2.1 Only suitable materials such as medium stiff clay, clayey sand or other approved
soils shall be used for filling.
14.2.2 Materials from swamps, peats or top soils and other highly organic clay or silt,
materials containing logs, stumps or boulders, which are susceptible to
combustion, and any other materials which, by virtue of their physical or chemical
composition or at their moisture content will not compact properly, shall not be
used for filling.
14.3 Spreading and Compacting
14.3.1 Prior to placing any fill upon any area, all clearing and grubbing operations shall
have been completed.
14.3.2 All earth filling generally, shall be carried out in layers not exceeding 225mm
thick loose layers. Each filling layer shall be thoroughly compacted by means of
six (6) passes of a smooth wheel 6T roller or other approved compacting
equipment.
14.3.3 Maximum use shall be made of earthmoving plants for initial compaction, and the
Contractor shall be required to vary the routes uniformly to reduce ‘tracking’ and
to obtain uniform compaction over as wide an area as possible.
14.4 Finish to Formation Level
14.4.1 Unless otherwise shown in the Drawings, the upper surface of all platform shall
be finished to a cross fall of 1:400 and where practicable, shall, in addition, be
given a longitudinal fall to ensure rapid disposal of surface water.
14.4.2 For areas to be turfed, the formation shall be completed to an appropriate level
below the finished level indicated, to allow for placement of top soil and turf.
14.5 Soft Spots
14.5.1 Where any undue movements due to the presence of soft unstable soil under the
fill occur, or unsuitable material is encountered at the bottom of the fill, it shall be
excavated to such depth and over such areas as approved by the S.O., and shall
be removed to spoil. The resulting excavation shall be backfilled with suitable
material as specified hereinbefore, and deposited in layers not exceeding
225mm thick and compacted as described above, or with compaction equipment
suitable for working in small excavation.
14.5.2 The Contractor shall allow for settlement or displacement of fill over soft areas,
and shall build up to the required finished level with necessary compaction.
Should any settlement of fill occur during construction or within the Defects
Liability Period, the Contractor shall make good the same at his own cost and
expense.
Filling under Floors, Aprons etc.
15.1 Filling shall be provided and laid under floors, aprons, etc. where required. Filling shall be
of suitable material as specified hereinbefore, deposited in layers not exceeding 155mm
loose thickness, and each layer well watered where necessary, rammed and compacted.
No clay shall be used for filling under floors and aprons.
16. Temporary Drainage Channels and Bunds
16.1 As earthwork progresses, the Contractor shall provide and maintain efficient drainage of
the Site as specified under SECTION A: PRELIMINARIES AND GENERAL
CONDITIONS, until such time as the permanent surface water drainage is installed.
Clearing of Existing Ditches, Drains, Rivers, etc.
17.1 During the execution of the earthwork, the Contractor shall take all necessary precautions
to prevent blockage or obstruction, and to ensure free-flow of existing drains, ditches,
streams and the like.
Protection and Maintenance of Earthworks
18.1 The Contractor shall provide all necessary protection and maintenance of earthwork,
particularly from the damaging effects of water entering the works from rainfall, runoff,
springs, rivers or streams. Damage to finished or partly completed work arising from the
lack of such protection and maintenance work, shall be made good by the Contractor at
his own cost and expense.
18.2 Where turfing is required for slope protection, they shall be planted immediately after the
embankment is formed. The turfing shall be executed as specified hereinafter under
SECTION N.4: LANDSCAPING AND TURFING.
18.3 If due to unforeseen circumstances turfing cannot be carried out immediately, temporary
protection/cover (eg. plastic sheets or equivalent) shall be laid on exposed slopes by the
Contractor.
Hardcore
19.1 Where shown and required, approved hardcore consisting of good, sound broken bricks
or stones shall be provided and laid to the thickness shown in the Drawings, well
rammed, compacted and blinded with sand. All hardcore shall be well watered
immediately prior to the depositing of concrete thereon.
