A project requires a contractor to excavate 28,000 bank CY dryearth, haul it away to a borrow area located 3 miles away. Thecontractor has 4 weeks to complete the work. The contractor doingthe work has decided to mobilize scrapers with a capacity of 20loose CY. Each Scraper has a typical cycle time of 20 minutes dueto the rough terrain at the site. The contractor can purchase onescraper but will have to rent additional scrapers if necessary. Thecost data for a CAT 621 Scraper is as follows: A new CAT 621G costs$450,000 (without tires). The contractor plans to use it for fiveyears (average 2000 hours per year) and sell it for $190,000. Thescraper tires cost $4,250/tire (scraper has 4 tires) and willlikely last 6000 hours. The scraper consumes 10 gallons of fuel perhour. Diesel cost can be estimated at $3.0/gal. The annualmaintenance cost for the scraper can be estimated at $18,000.Scraper operator costs $58.00 /hour including overheads. The rateof interest can be assumed to be 6.5%. The rental agency is willingto rent a 621G for $6,000 per week or $ 18,000 per month. Thecontractor will have to provide fuel and operator. The mobilizationand demobilization cost for each scraper is $2,500. Based on thisinformation, analyze the earthwork operations. Makerecommendations:
1. How many scrapers should the contractor rent?
2. Estimate the cost in $$/bank CY
(Please show all work clearly and neatly)
