Exercise 5- PERT/CPM: Grasso Construction Company.
Exercise 5- PERT/CPM: Grasso Construction Company.
In 2018, Grasso Construction Company had received a contract to construct a water purification system for the city of Wilmington. By the fall of 2019, work was nearly complete on the main system; however, it was apparent that work on a special remote control building would have to be finished earlier than originally planned if the main system was to be completed on time.
Mr. Jason Barnes, field construction supervisor for Grasso Construction Company had arranged a meeting with Ms. Addison Lee, project engineer, to restudy the arrow diagram of their critical path schedule for the construction of the remote-control building in an effort to determine the shortest possible time in which the job could be done without spending more money than necessary.
Grasso Construction used the Critical Path Method as a tool to assist in project planning and control. A list of the activities for the remote-control site is in Exhibit 1. The Cost Table, Exhibit 2, lists the activities and their duration along with the cost needed to complete them in this “normal time”. The Cost Table also lists the minimum amount of time that each activity will require, called the “crash” time. In addition, a final listing in the Cost Table shows how much it will cost to shorten each activity by one week. The sequence of consecutive activities requiring the longest time to complete before the end of the project is known as the “critical path” for that project. The path is considered “critical” because any delay in the particular sequence will delay the completion of the entire project.
Exercise 5- PERT/CPM: Grasso Construction Company.
Exhibit 1
| Job Label | Job Description | Immediately Preceding Job | Normal Time te | tp |
| A | Procure materials | Start | 3 | 4 |
| B | Prepare site | Start | 6 | 8 |
| C | Prepare request for Wilmington Engineering department approval | Start | 2 | 3 |
| D | Prefabricate building and deliver to site | A | 5 | 7 |
| E | Obtain Wilmington Engineering department approval | C | 2 | 3 |
| F | Install connecting lines to main system | A | 7 | 8 |
| G | Erect building and equipment on site | B, D, E | 4 | 6 |
Exhibit 2
Cost Table for Remote Control Building Project
| Normal | Crash | |||
| Activity | te (Weeks) | Dollars | to (Weeks) * | Dollars** |
| A | 3 | $ 5,000 | 2 | $ 5,000 |
| B | 6 | $ 14,000 | 4 | $ 6,000 |
| C | 2 | $ 2,500 | 1 | $ 2,500 |
| D | 5 | $ 10,000 | 3 | $ 4,000 |
| E | 2 | $ 8,000 | 2 | – |
| F | 7 | $ 11,500 | 5 | $ 3,000 |
| G | 4 | $ 10,000 | 2 | $ 7,000 |
| Total Project Cost (No Crashing) |
$ 61,000 | |||
*Crash weeks shown represent the minimum possible time for the given activity, to.
**This is the cost of gaining one week over the normal time by use of “crash” methods.
Exercise 5- PERT/CPM: Grasso Construction Company.
Answer the following questions regarding Grasso Construction Company. Be sure to answer every single question in each individual part.:
- Draw a PERT/CPM diagram of this building project. I need to see your drawing.
**create PERT diagram here***
- What is the critical path?
| Paths | Weeks |
Exercise 5- PERT/CPM: Grasso Construction Company.
- How long will it take to complete the project without crashing?
- It would take ____ weeks
- What is the associated cost? (Remember to reference Normal Dollars in Exhibit 2 for all of the activities)
- Associated cost $________
- Revise the schedule in order to complete the job within 10 weeks using the crashing method. Indicate the new cost and critical path or paths.
(highlight new critical path(s) after crashing)
| Paths | Weeks |
(*note when crashing, I find it easiest to highlight or color my text for each critical path differently to see if there are any overlaps)
| Activity | te (Weeks) | to (Weeks) * | Crashing Cost | Weeks to Crash
(Te-To) |
Goal to get to 10 weeks by crashing
- *crash to 11 weeks* crash ___by 1 week= $_________
- *crash to 10 weeks* crash ____ by 1 week= $_________
- Initial Cost of the project = $_________
- New total cost would be $__________
- Starting from the original tables listed in the exhibits above, Grasso Construction will need to use a new 10-week schedule. However, it became obvious that it would take not two but five weeks to prepare the necessary data for Activity C and that this step alone would now cost $7,000.
****put updated PERT diagram****
(use this grid to put original paths for comparison)
| Paths | Weeks |
- What steps would you take to keep on schedule?
| Paths | Weeks |
(*note when crashing, I find it easiest to highlight or color my text for each critical path differently to see if there are any overlaps.)
| Activity | te (Weeks) | to (Weeks) * | Crashing Cost | Weeks to Crash |
Goal to get to 10 weeks by crashing
- *crash to 11 weeks* Crash ___ by 1 week= $_________
- *crash to 10 weeks* Crash ___ by 1 week= $_________
- Total cost of project = $ _________
- Total cost to get down to 10 weeks= $__________
- What would be your new critical path or paths? (tell me new critical path(s) after crashing)
- Critical Path ___________________
- What would happen to project costs? (Assume that activity C cannot be crashed.)
- Projects costs total = _________________
- Assume that the project was planned for completion in six weeks and that activity C, the preparation for approval, would take two weeks as described in the case (i.e., go back to where you left off at the end of part 1).
- If there is a penalty cost of $10,000 per week for every week the project is late, what action would you take? (make sure to compare the penalty cost to the cost of crashing to see if it is worth it)
| Paths | Weeks |
Exercise 5- PERT/CPM: Grasso Construction Company.
(*note when crashing, I find it easiest to highlight or color my text for each critical path differently to see if there are any overlaps. In this case, if you have multiple critical paths, you need to make sure you crash either one activity on both paths or a combination of activities on the two critical paths that is less than or equal to the 10K penalty. This would count as one step.)
| Activity | te (Weeks) | to (Weeks) * | Crashing Cost | Weeks to Crash |
Goal to get to 6 weeks by crashing
- *crash to 11 weeks* crash ____by 1 week =$_______
- *crash to 10 weeks* crash ___ by 1 week= $________
- *crash to 9 weeks*
- *crash to 8 weeks*
- *crash to 7 weeks*
- *crash to 6 weeks*
- Initial Cost of the project = $___________
- Total cost to get to 6 weeks= $____________
Explain result: _____________________________________________________
- Can you expedite the project so as to finish in 6 weeks? (now it’s time to think about if it is even possible to get it down to 6 weeks. Do not take the penalty into consideration here.)
Goal to get to 6 weeks by crashing-
- *crash to 11 weeks* crash ____ by 1 week =$___________
- *crash to 10 weeks* crash ____ by 1 week= $___________
- *crash to 9 weeks*
- *crash to 8 weeks*
- *crash to 7 weeks*
- *crash to 6 weeks*
- Initial Cost of the project = $_____________
Explain result: ____________________________________________
- What is the probability of completing this building project in 9 weeks?
(Refer to the “Example Using LP” video)
Click here for further assistance on this assignment
