Part 1 of 2 on Time Impact Analysis (TIA) of Adverse Weather Delay Days in Cost-Loaded Network Analysis Schedules (NAS)
Cost-Loaded Network Analysis Schedules (NAS) for construction using Oracle Primavera P6
The United Facilities Guide Specifications (UFGS) UFGS-01 32 17.05 20, Section 01 32 17.05 20, Cost-Loaded Network Analysis Schedules (NAS) for Design-Build (DB) guide specification applies to Design-Build projects and covers the preparation and use of Cost-Loaded Network Analysis Schedules (NAS) for construction using Oracle Primavera P6. The specification section applies to construction projects with multiple disciplines working simultaneously during multiple phases with critical completion dates for handover to the owner.
Excusable delay for weather — contractor may receive a time extension, but time will not be compensable
1.8 Contract Modification requires the contactor to “…submit a Time Impact Analysis (TIA) with each cost and time proposal for a proposed change. TIA must illustrate the influence of each change or delay on the Contract Completion Date or milestones…” Further, each Time Impact Analysis (TIA) must be submitted to the owner in both narrative and schedule form. The contractor must identify the type of the delay, such as an excusable delay for weather – where the contractor may receive a time extension, but time will not be compensable.
Guide specification only addresses weather lost work days as a result of rain events
The Cost-Loaded Network Analysis Schedules (NAS) for Design-Build (DB) guide specification also describes “Anticipated Weather Lost Work Days,” either National Oceanic and Atmospheric Administration (NOAA) historical monthly averages as the basis for establishing non-workdays or a default value of 2 anticipated weather lost work days per month. However, the guide specification only addresses weather lost work days as a result of rain events, and not other weather events, such as snow, temperature, wind, thunderstorm and lightning events.
Weather risk sensitives and risk tolerances of activities, operations and results to events vary
Further, the guide specification recommends using a nominal 30-year, greater than 2.5 mm (0.10 inch) amount parameter for rain events. With multiple disciplines working simultaneously during multiple phases, schedule activities, equipment operations and work results are at risk of being impacted by numerous weather events. Weather risk sensitives and risk tolerances of activities, operations and results to events vary. For example, earthwork may be less sensitive to a 2.5 mm (0.10 inch) or greater rain event when compared with metalwork.
Data logged at only one station versus data aggregated across many stations
As the basis for establishing a “weather calendar” showing the number of anticipated non-workdays for each month due to adverse weather, the guide specification also recommends to use data as indicated on the station report for the NOAA location closest to the project site — which may not be in reasonable proximity to the construction site. Further, the guide specification recommends to use data logged at only one station versus data aggregated across many stations in a mathematical model, as the basis for establishing a “weather calendar.”
More in the next blog post about weather decision support, weather safety and weather risk management…
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About United Facilities Guide Specifications
Unified Facilities Guide Specifications (UFGS) are a joint effort of the U.S. Army Corps of Engineers (USACE), the Naval Facilities Engineering Command (NAVFAC), the Air Force Civil Engineer Center (HQ AFCEC) and the National Aeronautics and Space Administration (NASA). UFGS are for use in specifying construction for the military services. (Source: https://www.wbdg.org/ffc/dod/unified-facilities-guide-specifications-ufgs)
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