Determining the Overall Project Duration at 80% confident Level with a predicted Weather Condition Using the Oracle Primavera Risk Analysis.

After determining the activities duration for the construction of a Dam Project in the Northern Part of Mozambique (Detailed in my previous article). The same contractor wants me to predict the overall project duration at 80% confident level using expected weather condition as shown below:

My Approach

One of the significant risks in the delivery of a construction contract is the effect on delivery time of delays in critical activities. Delays caused by weather conditions, are beyond the contractor’s control and it can not be reasonably anticipated at the time of bidding for the contract. These delays make it difficult or impossible to meet the project completion date.

Predicting project delays is valuable, particularly at the time of bidding for the contract. Once an issue is recognized as a delay to an activity, it will be important to establish the length of the delay and its effect on the project schedule. In many cases, even though contractor may be aware of the existence of a potential cause of delay, they may not be able to accurately assess key issues like its full extent, its probable consequences, and whether or not it is likely to delay the project completion date. Contractor, therefore, need appropriate tools to assist him in the process of updating the schedule based on the analysis of delays due to weather condition.

Delays as a result of weather conditions are significant risk factors in the contract delivery process. To calculate the expected duration of acceptable delays as a result of weather condition, a reasonable method such as the What-If Analysis based approach is best.

Project Calendar

• 5 days Working Calendar, consisting of 8 Hrs per day
• Non Working Day: All Weekends, & 19th Dec to 6th January

Prediction of Weather Condition

Rain Days > 10mm rain

• January - 10.5 days rain
•  February - 4 days rain
• March – 5 days rain
•  April - 1 day rain
•  May – 2 days rain
• October – 5 days rain
•  November – 6 days rain
•  December – 6 days rain

Calculating Schedule Delay

Based on the above rain days assumptions, the schedule delays may be determined by using the Oracle Primavera Risk Analysis (PRA). 

Project Schedule

The P6 schedule for the project is as shown. The as-planned duration of the project is 354 days

Application of Oracle Primavera Risk Analysis (PRA)

As noted above, Oracle Primavera Risk Analysis provides a process to assist the prediction of the project completion date as a result of weather conditions.

This is basically to help to make decisions. To illustrate this process

• 3-point estimate (Pessimistic, Optimistic & Most Likely) was used to calculate expected completion date for no rain assumption.

• 3-point estimate (Pessimistic, Optimistic & Most Likely) was also used to calculate expected completion date for rain days assumption.

After conducting the What-If analysis, a distribution analyzer for the project was obtained and the confident level at each point was determined as shown below:

With rain days assumption as stated above, the overall Project Duration at P80 (80% Confident level) is 405 days (Shown below).

With No rain days assumption, the overall Project Duration at P80 (80% Confident level) is 363 days (Shown below).

Although weather delays are typical of the so-called “act of God” type of delay. Based on experience, general conditions of contract are that only adverse weather conditions that cannot be reasonably anticipated would qualify as a basis for time extension. But improved prediction of project duration has the potential to assist the contractor to make better estimates of the expected delivery dates of projects. Better prediction of project duration as a result of weather condition has the potential to enhance target time and cost estimates. it is also an important step in better predicting the likely time of a construction project given likely weather conditions, with resulting benefits for both the customer/client and the contractor.

Thank you