Introduction to Construction Management
SUBJECT: Homework Assignment #7
Dear CMGT 240 student,
Please complete for following assignment and submit a hardcopy prior to the beginning of class, April 30, 2014. The assignment must include a memorandum identifying the submittal content and submitter as the cover sheet.
Homework Value: 50 points
This assignment provides you the opportunity to experience short term scheduling.
Sincerely,
Scenario:
Pipe Pro, put together a cost estimate that made Dirt Diggers select them as their subcontractor for the foundation excavation work package. Dirt Diggers was awarded with the sitework contract for being the lowest bidder. After receiving the Notice to Proceed, the new earthwork contractor signed the formal agreement.
Then the site preparation began at the site. The demolition of an old structure and the clearing of the site were followed by the excavation. The total dirt to be moved measured 250,000CY. Pipes were laid for the water supply and the sewer system as well as for the stormwater drainage. Many other activities are soon to follow. To perform the site preparation in an economical manner, time, cost, and quality needed to be monitored closely.
Dirt Diggers received a request from the Construction Manager to provide them with a detailed schedule for the sitework. Dirt Diggers had been in business for many years and had an experienced team in the scheduling department. Therefore, the preparation of such a schedule did not cause any problems. However, Dirt Diggers' scheduling team needed to know how much time Pipe Pro estimated for their portion of the job. Dirk from Dirt Diggers placed a call to Pipe Pro.
The phone rang in Peter Piper's office. Peter picked up the phone and spoke to Dirk, the scheduler. After finishing the phone call he went to see Tim Timer, the person in charge of schedules at Pipe Pro. Peter provided Tim with the memo and all the calculations that were produced during the preparation of the cost estimate for Dirt Diggers. He also had this to tell Tim.
Peter: The guy from Dirt Diggers told me on the phone that there would be some storage restrictions on site. We can store all the bedding material at the site, but the pipes will be a problem. We can have no more than 850 feet of pipe on site at once.
Tim: Okay, I can plan for different deliveries.
Peter: Do you remember the delivery times for bedding material from the job we just did last week?
Tim: Yes, of course. We needed to order the aggregate we use at least 6 workdays in advance and they would deliver about 150 LCY per day max. They tend to deliver in the afternoon, so we should plan on deliveries the day before we need them.
Peter: How about our pipe supplier?
Tim: I don't really know. I will have to check with them.
Peter: All right, go for it.
Tim called the pipe supplier and they told him that he could order by telephone a minimum of 7 workdays before delivery. Orders should be placed in 850 LF quantities; however, the supplier's truck capacity is limited to delivering 425 LF of pipe per day.
Tim called the general contractor on the job as well, and found out that once Pipe Pro had completed all of the excavation work, the GC would come out and set up the formwork and pour the footings. The GC estimated that this would take 4 days to complete.
From past experience Tim knows that it takes about 3 days to move in the equipment. Before the start of pipe placement, the first 250 feet of pipe should be on site, 1/3 of the bedding material must be in place, and the concrete footings must have cured for at least 7 days. Tim made a note to himself to notify the general contractor about coming back to remove the formwork and having the 2-inch rigid insulation in place by the time the 7-day cure was completed so that wouldn’t slow down Pipe Pro. Only one excavator will be available for construction along with a dozer and compactor. All of the pipe must be in place before the remainder of the bedding material can be placed and compacted. Compacting the backfill will occur simultaneously with placing the backfill, so these items may be combined into one activity on the schedule. The pipe will be laid by hand because it is only 4-inch diameter perforated PVC pipe.
(The story is fast-forwarded here.)
Tim Timer finished his schedule and it was sent to Dirt Diggers. Construction started and proceeded as scheduled. The excavation ran fairly smoothly. The GC ran into some problems when they were setting up the formwork for the footings. The weekend before they started, it snowed nearly 30 inches in a freak April snowstorm. This slowed down the contractor significantly and they were unable to get all the formwork completed in four days as planned. They wound up spending six days getting the formwork ready and pouring the footings. The GC notified Pipe Pro of the delay when they completed the work on the forms and poured the concrete. This delay put Pipe Pro two days behind their schedule, due to no fault of their own. As soon as he found out, Paul Piper got on the phone to call the pipe supplier.
Paul Piper talked to the pipe supplier the day before and ordered the second set of 800 feet of pipe. Today he had to ask the supplier about possibly delaying the delivery of this set of pipe by two days. The supplier was not delighted about this change, but he said it would be possible. Other than the two days of delay from the general contractor, work continued as it had before the snowstorm.
On the day that the second set of pipes was scheduled for delivery, however, no truck from the pipe supplier arrived. As soon as Paul heard about this, he grabbed the phone and called the supplier to find out what was going on. Unfortunately, different orders became mixed up at the pipe-manufacturing site, and it would take another two days until the pipes could be shipped to the project site. The piping crew continued to place and joint pipes for that day. The next two days, the crew was actually sent to another job site since they had nothing to do at the current project. By the end of the first day on which the pipe crew was absent, Tim Timer prepared a new schedule showing what Pipe Pro had done thus far and how they were planning to finish the job.
Table 1
Item # | Description | Productivity | Units | Quantity determined | Units |
| For this HW Use Durations |
1 | Excavation | 200 | LCY/HR | 2101 | LCY | 16 HR | |
2 | Pipe Material | 7 Workdays before delivery, total truck capacity 425 LF per day | |||||
3 | Bedding Material | 6 Workdays before delivery, 150 LCY per day maximum | |||||
4 | Place Bedding Mat’l | 37.5 | LCY/HR | 469 | LCY | 12 HR | |
5 | Compact Bedding Mat'l | 25 | LCY/HR | 469 | LCY | 16 HR | |
6 | Lay & Joint Pipe | 50 | LF/HR | 1650 | LF | 36 HR | |
7 | Backfill | 144 | LCY/HR | 1000 | LCY | 8 HR | |
8 | Compaction | 115 | LCY/HR | 1000 | LCY | 8 HR | |
9 | Overhead | 172 Total Hours | |||||
Notes:
- No more than 850 LF of uninstalled pipe allowed on site
- 3 days to mobilize equipment
- 4 workday + 7 day (including weekends) lag for concrete between excavation finish and bedding/pipe/compaction start
- 5 workdays per week, 8 hours per day
- Job efficiency factor already included in productivity rates
Assignment 7
Prepare a schedule for the construction of the foundation system. Your assignment is to prepare a professional memo for Peter and Paul Piper including the following:
- Prepare an as-planned bar chart diagram for the whole project using Microsoft Excel, prior to the snowstorm delay.
- Provide a planned delivery schedule for the bedding material and pipes, prior to the snowstorm delay.
- Display the duration of each activity clearly. Note the total duration of Pipe Pro's part of the project. Include the lag time waiting for the concrete formwork, pours, and cure time when noting the duration of Pipe Pro’s work.
- Produce a second schedule depicting the as-built portion with the delays and the updated, as-planned portion.
- Show the duration of each activity. By how many days will the project be delayed?
Describe your thoughts about the impact of this delay overall on the project
