Module #4 Time Impact Analysis

Transcription

1 Reviewing & Analyzing CPM Construction Schedules Module #4

2 Forward looking schedule analysis technique that adds a modeled delay to an accepted contract schedule to determine the possible impact of that delay to the project completion. (AACE)

3 References Association for the Advancement of Cost Engineers (AACE) International Recommended Practice No. 52R-06, Time Impact Analysis - as Applied in Construction Web site:

4 Goals Determine the impact of a delay to the project completion date Give time due to the contractor in the contract modification

5 Assumptions Acceptable baseline schedule exists Regular schedule updates Forward looking Keep it simple

6 Schedule Terminology Project Scheduler Schedule Reviewer

7 Schedule Terminology Critical and Non-Critical Delays: Critical delays impact the project completion date Non-critical delays don t

8 Example New Building Addition Approximately 200 CY of petroleum contaminated soil was discovered on October 27 while contractor was excavating the building foundation, and underground water and electrical lines. Excavation cannot continue until the soil is removed. Govt. issued NTP on October 29 to remove soil, haul it away, and backfill with clean fill. Total delay duration is 5 days (2-days stop work and 3-days for excavating and hauling soil to storage yard).

9 Step 1 Identify affected activity(s) Model delay impact

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11 Step 1 Affected Activity: BA650 Excavation

12 Step 1 Determine delay impact 2 days stop work + 3 days removal/back fill = 5 Day Delay

13 Step 1 Model impact with a schedule fragnet

14 Step 1 Fragnet Opt. 1 Act. 1 Delay Act. 2 Opt. 2 Act. 1a Delay Act. 1b Act. 2 Opt. 3 Act. 1 Act. 2 Delay

15 Step 1 Un-Impacted Excavation 10-days Impacted Install Underground Water Install Underground Electrical Install Underground Water Excavation 7-days Mod. 1 Remove Contaminated Soil 5-days Finish Excavation 3-days Install Underground Electrical

16 Step 2 Select the appropriate schedule Use the last updated schedule prior to the delay start Progress schedule if time frame between previous schedule update and impact too great

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18 Step 2 Note project completion date Completion Date August 4, 2000

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20 Step 3 Insert fragnet into the updated schedule (don t forget calendar, logic, etc.) Set delay duration to zero

21 Install Underground Water Excavation 7-days Mod. 1 Remove Contaminated Soil 0-days Remaining Excavation 3-days Install Underground Electrical

22 Step 3 Re-compute CPM completion date should not change Original completion date August 4, 2000

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24 Time Impact Schedule Step 4 Insert delay duration: 5 days Re-compute CPM

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26 Step 5 Note new completion date If applicable, note completion date(s) for all other contractual milestones

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28 Step 6 Determine the number of days owed to the contractor: Old completion date is August 4 New completion date is August 11 Total Float = -5 days 5 or 7 days?

29 Step 7 Determine actual dates for the critical delay Delay begins on first day of negative float; ends when the number of delay days are exhausted October 28 November 3

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31 Step 8 Review Schedule for Concurrent Delays Contractor delay during same period, then Excusable and noncompensable No contractor delay, then Excusable and compensable

32 Step 9 Document TIA Price Negotiation Memorandum (Act ID, issue, affected trades, date changes, etc.) Contract Modification

33 Sample Problem