Question

You are planning to excavate the 30-foot by 40-foot basement area of a house to a depth of 10- feet in common earth. An 18-inch wide, 5-foot deep, 100-foot long sewer trench will also be required. You have at your disposal a hydraulic excavator with a ½ cubic yard 24-inch wide bucket. The excavator’s maximum digging depth is 14.7-feet and the average angle of swing is estimated to be 75-degrees. Job efficiency is expected to be 45-minutes per hour with costs for the excavator being $50 per operating hour and $250 each to transport the excavator to the site and return it to the equipment yard after trench and basement excavations are complete. Allow for 5-percent overage in basement excavations and 10-percent overage beyond the capabilities of the equipment for the trench. After the foundation has been placed and backfilled, and the trench has been covered, it is estimated that 400 cubic yards of loose material will remain in a single stockpile that will need to be moved offsite. You will have at your disposal a crawler crane with a 0.90 LCY clamshell to load a series of dump trucks. Cycle time for the clamshell is estimated to be 45-seconds with the same 45-minute per hour efficiency. Costs for the crane and clamshell are $75 per operating hour and a combined lump sum of $500 to mobilize and demobilized.

ASSUMPTION(S)/CONDITION(S)  Excavator bucket heap accounts for material swell. You do not need to account for swell and/or shrinkage in your calculations.

 When using tables to determine appropriate factors to use in your calculation and a range is given, use the middle value between the high and low.

 All material excavated for the trench will be used during backfilling operations. There are no spoils remaining from the trench portion of the excavation.

 Assume that sufficient dump trucks will be available into which to load the remaining basement spoils. That is, there will be no downtime waiting for trucks to become available.

 No partial workdays are allowed. Should less than a full day be required to all or a portion of the work, payment for the full 8-hours is still required.

QUESTION 1 How much material is required to be excavated from: a) The basement, and b) The trench?

QUESTION 2 What is the time required to excavate a) the basement, and b) the trench?

QUESTION 3 What are the total costs and unit costs to excavate: a) The basement, and b) The trench?

QUESTION 4 How many hours does it take to load the remaining excavation spoils to transport them off-site?

QUESTION 5 How much does it cost to mobilize, demobilize, and load the excavation spoils in total and as a unit cost?

Answer 1

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