Cost Estimating 101Conceptual Estimating

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Learning Objectives

• Select appropriate estimating approach and prepare base cost estimate.

• Determine cost estimate components and quantify them.

2

Learning Objectives (cont’d)

• Develop estimate data based on historical cost database.

• Apply conceptual estimating techniques

3

Conceptual Estimating Overview

• Planning and early scoping estimates–very little project definition

• Estimating total project cost by major components:–Right of way –Construction–Engineering/Design –Construction engineering 4

Conceptual Estimating Overview (cont’d)

Conceptual estimating techniques are based on: – statistical relationships

– ratios between project definition information/data and historic costs

–using similar projects

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Conceptual Estimating Overview (cont’d)

• Specific work items are undefined/unquantifiable:

– it is difficult to estimate costs in detail.

• Use major project features (reflect a specific type of facility) to develop the cost relationships.

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What is Conceptual Estimating?

• Methodology to attain total project cost at earliest stages of project development.

• STA should have its own historical cost database to:

–develop cost estimates based on minimal definition of project parameters.

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What is Conceptual Estimating? (cont’d)

• A method that often relies on previous similarly projects.

• Conceptual estimating approaches provide reasonably accurate estimates in a timely manner.

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Why to Use Conceptual Estimating?

Develop early projections of project cost when limited information is available to:

–develop long-range plans– assess benefit-to-cost ratios – compare the cost of different project

alternatives

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Determine Estimate Basis

The basis of the estimate comes from: –project definition –project characteristics

Challenge: Ensure the estimate covers all categories of each major project component.

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Project Definition

• At a high level, –project definition reflects the major

components of a facility

• Project type information: –preservation – rehabilitation– reconstruction project–new construction 11

Project Definition (cont’d)

Sketches or schematic drawings with approximate dimensional information.

To prepare conceptual estimate for complex

projects

Increased level of project definition details

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Project Characteristics

Focus is on the “larger picture” characteristics: –project location–potential environmental issues and utility

impacts– the extent of right-of-way required

Principle driver defining specific project characteristics

project’s level of complexity

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Project Characteristics (cont’d)

• Estimators should consider a visit to the project site.

• If a physical visit is not possible

–Google street view –Google Earth–Pathweb Viewer

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Conceptual Estimating Techniques

(1)Conceptual estimating techniquesGeneral considerations

Square Yard cost factors

Bridge cost factors

Historical percentages

Non-construction cost components15

General ConsiderationsConstruction Cost Factors

• Can start with the lowest level of cost details.

• Construction bids are aggregated to reflect a fundamental parameter associated with the project type.

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General ConsiderationsConstruction Cost Factors

• Current conceptual cost factors might not include newly enacted requirements that affect projects.

• An appropriate contingency should be added to account for these changes.

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Lane Mile Cost Factors

• Lane-mile cost factors can be based on:– typical sections representing common

types of facilities–historical cost data.

• Use data from relevant bid items.

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Lane Mile Cost Factors (cont’d)

An example of developing a lane-mile cost factor using weighted average unit prices per pay item.

Source: Florida Department of Transportation Roadway Design

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Development of Lane-Mile Cost

Factor

Description: Configuration—New Construction 5-Lane Undivided Urban Arterial with Center Turn Lane and 4 ft Bike Lanes Basis—Typical Roadway Configuration and Section for 1 mi and Bid Pricing Cost per Mile Factor—$4,700,000 Pay Item

Description

Total

Quantity

Unit

Weighted Avg. Unit

Price

Total Amount

0101 1 MOBILIZATION 10.00 %* $419,501.06 0102 1 MAINTENANCE OF TRAFFIC 7.00 %* $274,439.94 0104 10 3 SEDIMENT BARRIER 10,560.00 LF $.84 $8,870.40 0104 11 FLOATING TURBIDITY BARRIER 250.00 LF $7.76 $1940.00 0104 12 STAKED TURBIDITY BARRIER-

NYLON REINFORCED PVC 250.00 LF $3.75 $937.50

0104 15 SOIL TRACKING PREVENTION DEVICE

1.00

EA

$2,154.40

$2,154.40

0104 18 INLET PROTECTION SYSTEM 53.00 EA $35.52 $1,882.56 0107 1 LITTER REMOVAL 1.20 AC $16.66 $19.99 0107 2 MOWING 1.20 AC $29.11 $34.93 0110 1 1 CLEARING & GRUBBING 20.18 AC $4,832.63 $97,522.47 0120 1 REGULAR EXCAVATION 19,360.00 CY $3.54 $68,534.40 0120 6 EMBANKMENT 103,851.73 CY $4.96 $515,104.58 0160 4 TYPE B STABILIZATION 42,920.53 SY $2.35 $100,863.25 0285709 OPTIONAL BASE, BASE GROUP 09 39,893.33 SY $10.66 $425,262.90 0334 1 24 SUPERPAVE ASPH CONC, TRAF D,

PG76-22

6,582.40

TN

$86.37

$568,521.89 0337 7 20 ASPH CONC FRIC COURSE, INC

BIT, FC-12.5, FC6, PG76-22

3,191.47

TN

$140.75

$449,199.40 0400 2 2 CONCRETE CLASS II, ENDWALLS 36.00 CY $795.54 $28,639.44 0425 1351 INLETS, CURB, TYPE P-5, <10″ 36.00 EA $3,061.55 $110,215.80 0425 1451 INLETS, CURB, TYPE J-5, <10″ 10.00 EA $4,602.64 $46,026.40 0425 1521 INLETS, DT BOT, TYPE C, <10″ 5.00 EA $1,899.03 $9,495.15 0425 1541 INLETS, DT BOT, TYPE D, <10″ 1.00 EA $2,404.23 $2,404.23 0425 2 41 MANHOLES, P-7,<10′ 5.00 EA $2,589.96 $12,949.80 0425 2 71 MANHOLES, j-7, <10′ 1.00 EA $4,477.67 $4,477.67 0430171103 PIPE CULVERT OPTIONAL

MATERIAL, ROUND-SHAPE, 37-48″, STORM SEWER

5,056.00

LF

$137.23

$693,834.88 0430171104 PIPE CULVERT OPTIONAL

MATERIAL, ROUND-SHAPE, 49-60″, STORM SEWER

200.00

LF

$195.73

$39,146.00 0430175112 PIPE CULVERT, OPTIONAL

MATERIAL, ROUND, 12″S/CD 2,328.00 LF $43.82 $102,012.96

0430175130 PIPE CULVERT, OPT MATERIAL, ROUND, 30″S/CD

208.00 LF $66.39 $13,809.12

0520 1 10 CONCRETE CURB & GUTTER, TYPE F

10,560.00

LF

$12.68

$133,90.80

0522 1 SIDEWALK CONCRETE, 4″ THICK 5,866.67 SY $26.49 $155,408.09

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Lane Mile Cost Factors (cont’d)

Alternative Approach

– Develop lane-mile cost factors based on using the actual cost of completed or ongoing projects.

Dollars per Centerline Mile

– Divide the cost of the completed project by the total centerline miles for the project.

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Bridge Cost Factors

Bridge costs per deck area ($/SF) is similar to the lane-mile approach for roadways.

cost per square foot of deck area varies

provide a range for the deck cost factor

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Type of Bridge Measure

(SF Bridge Deck)

Low

($/unit)

Average

($/unit)

High

($/unit)

Prestressed Concrete Girders—Span 50-175 ft

Water Crossing w/ Piling SF 150 175 200

Water Crossing w/ Spread Footings SF 140 165 190

Dry Crossing w/ Piling SF 120 155 180

Dry Crossing w/ Spread Footings SF 110 145 160

Reinforced Concrete and Post-Tensioned Concrete

Box Girder—Span 50-200 ft

Water Crossing w/ Piling SF 200 250 300

Water Crossing w/ Spread Footings SF 175 225 275

Dry Crossing w/ Piling SF 160 200 250

Dry Crossing w/ Spread Footings SF 150 190 230

Concrete Bridge Removal SF 20 35 50

Widening Existing Concrete Bridges (including

Removal) SF 175 200 300

SE Wall Precast Concrete Panels SF 30 40 50

SE Wall Welded Wire SF 20 30 40

NOTES:

Bridge areas are computed as follows:

Typical Bridges: Width x LengthLength: Distance between back of pavement seats, or for a bridge having wingwalls, 3′-0 behind the top of the embankment

slope; typically end of wingwall to end of wingwall.Special Cases:Widening—actual area of new construction Source: Design Manual 2011

$/SF of Bridge Deck-

Statewide Average

Historical Ranges in

2011 Dollars

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Source: Caltrans Bridge Cost Estimating

$/SF of Bridge Deck-Statewide

Average Historical Ranges

in 2011 Dollars

SIMPLE CONTINUOUS

RC SLAB 0.06 0.045 16-44 100-300

RC T-BEAM 0.07 0.065 40-60 100-200

RC BOX 0.06 0.055 50-120 110-180

CIP/PS SLAB 0.03 0.03 40-65 90-200

CIP/PS BOX 0.045 0.04 100-150 90-170

PC/PS SLAB0.03

(+3" AC)0.03

(+3" AC)20-50 100-250

PC/PS0.06

(+3" AC)0.055

(+3" AC)30-120 120-230

BULB T GIRDER 0.05 0.045 90-145 120-200

PC/PS I 0.055 0.05 50-120 110-190

PC/PS BOX 0.06 0.045 120-200 140-250

STRUCT STEEL I-GIRDER

0.045 0.04 60-300 170-425

Spread FootingNo Stage Construction

COMPARATIVE BRIDGE COSTSJANUARY 2011

The following tabular data gives some general guidelines for structure type selection and its relative cost. These costs should be used just for preliminary estimates until more detailed information is developed.These costs reflect the 'bridge costs' only and do not include items such as: bridge removal, approach slabs, slope paving, soundwalls or retaining walls.

Remote LocationCantilever Abutment

**COST RANGE ($ /

FT2)REMARKS

Widenings Less Than 15 ft.

Factors That Will Increase the Price Over the High End of the Price Range 25%-150%Structures With More Than 2 Construction Stages

Unique Substructure Construction

The following factors must be taken into account when determining a price within the cost range:

Factors for Lower End of Price Range Factors for Higher End of Price Range

Pile Footing2 Stage Construction

Short Spans, Low Structure Height, No Environmental Constraints, Large Projects, No Aesthetic Issues, Dry Conditions, No Bridge

Skew

Long Spans, High Structure Height, Environmental Constraints, Small Project, Aesthetic Issues, Wet Conditions (cofferdams required), Skewed Bridges

Urban LocationSeat Abutment

NO FALSEWORK REQUIRED

NO FALSEWORK REQUIRED

NOTE: Removal of a box girder structure costs from $8 - $15 per square foot.

**Average Cost/SQFT are calculated using "Bridge Costs Only" as defined by the FHWA

THESE ARE THE MOST COMMON TYPES AND ACCOUNT FOR ABOUT 80% OF BRIDGES ON CALIFORNIA STATE HIGHWAYS.

STRUCTURAL SECTION

(STR. DEPTH/MAX SPAN) COMMON SPAN RANGE

(feet)

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Historical Percentage Cost Factors

• Used when construction elements are not: –defined at the planning phase – covered in historical data sources

Selected construction elements

Total construction cost category

Historical percentage cost factors

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Historical Percentage Cost Factors (cont’d)

• Projects should be similar in definition and complexity.

• Several projects should be used – so that a range of percentages can be

reviewed.

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Computer-Generated Cost Factors

Computer software is used to store and sort historical cost data.

–AASHTO Trnsport BAMS/DSS®

–AASHTOWare Project Estimation

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Prepare Base EstimateKey Steps

1. Select appropriate estimating approach.

2. Determine estimate components and quantify.

3. Develop estimate data.

4. Calculate cost estimate.

5. Document estimate assumptions and other estimate information.

6. Prepare estimate package. 28

2. Determine Estimate Components and Quantify (cont’d)

Example:• project requires both structures and pavement

construction.

• Estimators derives quantities for the major parameters such as: – lane miles – square foot of bridge deck area/retaining wall area

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3. Develop Estimate Data

The estimator:

1. matches the types of quantities with the construction cost data.

2. applies proper adjustments based on:• Project type• Project definition• Site characteristics

3. decides on the percentages of ROW, PE, and CE costs. 30

3. Develop Estimate Data (cont’d)

• Selecting historical cost data• Adjustments to cost data

–Time –Location–Unique project location characteristics–Scope–Unique project definition

• Adjustment Summary 31

Selecting Historical Cost Data

• The data selected represents the type of project for which an estimate is being prepared.

• In selecting the cost factor, project definition or scope should be clear.

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Adjusting Historic DataLocation

• Cost factors are often developed based on statewide averages.

• Cost differentials may impact:

– labor wage –materials cost – construction equipment cost

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Adjusting Historic DataUnique Project Characteristics

• Site specific considerations:

– terrain–batch plants –haul distances

• Input from construction engineers.

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Adjusting Historic DataScope

• The estimator develops percentages to cover work elements not covered by the basic cost factor.

• The cost factors database should identify what is included in the standard cost factor,

– so estimators can make any appropriate adjustments.

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Adjusting Historic DataUnique Scope Issues

• Some projects have unique project scoping issues.

• Cost adjustments are sometimes required for wetlands and other environmental impacts not clearly identified in cost factors.

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Adjustment Summary

• Apply various adjustments to cost factors for:– location characteristics– project definition– project complexity

• Can cover in contingency not in base estimate• Cost estimate documentation should describe all

adjustments.

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Cost Factors for Non-Construction Components of Total Project Cost

• Estimated using percentages.

• Relate these percentages to construction costs.

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Construction Engineering

Cost of activities associated with administering a project such as:

–payroll and expenses for inspection forces–material testing and evaluation – central office administrative efforts– field reviews

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Construction Engineering (cont’d)

CE cost is calculated as a percentage of total construction costs based on:

–Project type –Project complexity –Project dollar size

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Determine Risk and Set Contingency

• Estimators should develop a contingency amount for the project based on the risk analysis process.

• Larger percent contingencies should be considered for conceptual estimates.

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Contingency

Conceptual cost estimates require considerable estimator experience and judgment to estimate contingency due to:

– lack of detailed project definition

– types of conceptual estimating techniques

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What to Check?

• Conceptual estimates have little detail to check.

• One review approach is to compare estimated costs with other similar projects which are:

– currently under construction – recently bid– in the letting phase

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Summary

• To create a conceptual cost,

–The estimator should prepare a total-project cost estimate based on major project parameters.

• The estimator must ensure that cost factors reflect the scope of the current project estimate.

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Resources

• Anderson, S., Molenaar, K., and Schexnayder, C. (2007). NCHRP 574: Guidance for Cost Estimation and Management for Highway Projects During Planning, Programming, and Preconstruction, Transportation Research Board of the National Academies, Washington, DC. (Mar. 29, 2011).

• Anderson, S., Molenaar, K., and Schexnayder, C. (2009). NCHRP Report 625: Procedures Guide for Right-of-Way Cost Estimation and Cost Management, Transportation Research Board of the National Academies, Washington, DC. (Mar 30, 2011).

• Anderson, S., Molenaar, K., Shane, J., Hughes, P., and Hall, J. (2008). Cost Estimation and Cost Management Technical Reference Manual, Minnesota Department of Transportation, Minneapolis, Minnesota. (May 1, 2011).

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Resources (cont’d)

• “Contract Estimate” (2011). Plans Preparation Manual Washington State Department of Transportation, Olympia, WA., 8-1 – 8-8. (May 1, 2011).

• Design Manual (2008), Washington Department of Transportation, July 2008. (May 1, 2011).

• “Recording and Coding Guide for the Structure Inventory and Appraisal of the Nation’s Bridges” (1995). US Department of Transportation, Federal Highway Administration, Report No. FHWA-PD-96-001, Office of Engineering, Bridge Division.

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Image References

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