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E STIMATION 1 Excavation 2 lesson 5

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E XCAVATION 2 Recap from excavation 1 Looking at site plans Desk top study Site Visit Unit pricing of excavation Excavate to reduced levels Excavate trenches Disposal of water Removal of excavated material

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E XCAVATION 2 Battering the slope of the excavation

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E XCAVATION 2 Nature of the ground Weather conditions Proximity of in ground services Trench/excavation depth Previously disturbed ground

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E XCAVATION 2 Earthwork support/shoring

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E XCAVATION 2 Earthwork support/shoring The cost is influenced by The nature of the ground and depth of excavation The type of excavation that needs shoring The material cost of the timber and the assessment made on how many times it can be used. Sheet pile shoring is usually used today.

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E XCAVATION 2 Unit cost for earthwork support Cost The labour cost of fixing and removing the timber The material cost itself The number of times the timber can be used before it is unfit for further usage

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E XCAVATION 2 Unit cost for earthwork support Cost The cost of the earthwork support is allowed by diving the initial cost of timber per m2 by the number of times it can be used Cost of timber is $220/m2 of face of excavation Can be used 10 times Allowance for earthwork support = $220/10 = $22.00/m2 of face of excavation

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E XCAVATION 2 Working space

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E XCAVATION 2 Working space Area for tradesmen to complete their work May or may not be required- estimator to review

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E XCAVATION 2 Schedule of Quantities for excavation

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E XCAVATION 2 Schedule of Quantities Consider the type of plant to use and the nature of the ground and quantities for excavation and disposal Check the amount of excavation = the amount of disposal

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E XCAVATION 2 Schedule of Quantities The total excavation Topsoil 380 m2 x = 105 m3 To reduced levels 246 m3 Trenches 38m3 Total 389 m3

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E XCAVATION 2 Schedule of Quantities The total disposal Topsoil 380 m2 x = 105 m3 Filling to excavation 47 m3 Disposal off site 237 m3 Total 389 m3

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E XCAVATION 2 Labour and machine constants Digger (banksman the same constants) Top soil –0.15 hr/m3 To reduced levels – 0.09hr/m3 To trenches – 0.14 hr/m3 Digger and roller (labourer the same constants) Working space allowance–0. 08hr/m3 Filling excavations – 0.08hr/m3

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E XCAVATION 2 Labour and machine rates Digger - $28.00/hr Digger + roller - $31.00/hr Banksman - $12.00/hr Labour - $12.00 hr Hardcore 1.95 t/m3 = $10.00/t

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E XCAVATION 2 Topsoil – 275mm deep Digger 0.15hr/m3 x $28.00/hr = $4.20 Banksman 0.15 hr/m3 x $12.00 = $1.80 Sub total = $6.00/m3 Top soil 1 m2 x.0275 = 6 x = $1.66/m2

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E XCAVATION 2 Excavate to reduced levels Digger 0.09hr/m3 x $28.00 = $2.52 Banksman 0.09hr/m3 x $12.00 = $1.08 Total $3.60/m3

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E XCAVATION 2 Excavate trenches Digger 0.14hr/m3 x $28.00 = $3.92 Banksman 0.14hr/m3 x $12.00 = $1.68 Labourer 0.14/m3 x $12.00 = $1.68 Total $7.28/m3

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E XCAVATION 2 Working space allowance Excavation as for trenches$7.28/m3 Assume 75% filling and 25% disposal Digger + roller (75% x 0.08hr/m3) = 0.06 hr/m hr/m3 x $31.00 = $1.86

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E XCAVATION 2 Working space allowance Labourers (2no) =(2 x 0.08) x $12.00 = $1.44/ m3 Additional earthwork support – not priced Additional disposal (25% x 1 m3) =.25 x $15.80 = $3.95 Total cost of working space/m3 = $ = $14.53/m3

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E XCAVATION 2 Working space allowance Working space is measured in m2 ( standard allowance is 250mm wide) Total cost of working space/m2 1 x.25 x $14.53/m3 = $3.63/m2

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E XCAVATION 2 Filling with excavated material Assumed that transport over short distances can be provided by a site dumper and an allowance for this has been included in the preliminaries Digger +roller 0.08 hr x $31.00 = $2.48 Labourer (2 no) (2 x.08 x $12.00 = $1.92 TOTAL $4.40/m3

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E XCAVATION 2 Hardcore filling Hardcore materials 1.9t x $10.00 = $19.50 Waste 10% 0.19t x $10.00 = $1.90 Digger + roller.05 x $31/hr = $1.55 Labourer (2 no) (2 x 0.05 x $12.00) = $1.20 TOTAL $24.15/m3

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E XCAVATION 2 Operational estimating This is form of estimating where all the resources needed for part of the construction are considered together Examples Drain runs including excavation, earthwork support, bedding, pipework and backfill

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E XCAVATION 2 What labour and plant is required ??

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E XCAVATION 2 Operational estimating Forecasting anticipated durations of activities Resourcing Advise from construction managers and subcontractors Estimator to provide a method statement so construction staff can understand assumptions made when preparing the estimate

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E XCAVATION 2 Operational estimating Estimator collates a list of resources for each operation to calculate the cost Estimator to provide a method statement so construction staff can understand assumptions made when preparing the estimate

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E XCAVATION 2 Advantages Construction methods are selected which are practical Programme of works included holidays, time of year, facilities available which give a more realistic guide to the time needed for plant and labour Alterations and repair works are priced globally not against each individual item which causes overpricing The sequencing of works can be looked at before the project commences which make for more efficient resources.

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E XCAVATION 2 Disadvantages If pricing a schedule of quantites it is difficult to split the costs accurately against each items. Initial discussion with other team members is necessary to provide the correct method statement and then implementing it once the works commence re Housing New Zealand rollouts

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E XCAVATION 2 Comparison of pricing a schedule of quantities with an operational estimate (looking just at plant and labour) Weighbridge foundation is priced based on the schedule The site Foreman knows that a similar project took 2 weeks for 4 labourer, a return visit for 2 men to complete. A backactor and roller was needed for 3 days to complete the project

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E XCAVATION 2

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Labour 4 no x 2 weeks x 45 hrs x $15.00 = $ no x 2 days x 9 hrs x $15.00 =$ TOTAL LABOUR $5, Plant 1 no x 3 days x 8 hrs = $ TOTAL = $6,780.00

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E XCAVATION 2 Review the difference in the total costs and ask the question why?? Good check for labour constants

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E XCAVATION 2 Hourly labour rates Standard code of practice to calculate the labour rate Hourly rate = annual cost of employing an operative/actual hours worked

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E XCAVATION 2 Considerations Rate includes public and annual holidays Overtime working No of hours worked each week Trade supervision Skilled operatives in the area/resources Travelling time/ subsistence allowance _ Hamiliton Bonus payments Insurances

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E XCAVATION 2 Plant rates Identify specific items of plant Purchase for the contract Company owned plant Hire from an external source Price sourcing Calculate from first principles Internal plant department rates Hirer’s quotations Published schedules

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E XCAVATION 2 References Estimating and tendering for construction work – Martin Brook

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