Estimate the direct cost of labor, materials, and simple equipment for the construction of a double-sided straight retaining wall 125 ft long, 15 ft high, and having a 12-in. interior dimension for the concrete. The wall will be resting on a footing that is in place. Oaks stakes to secure bracing are placed in firm earth. Reinforcing steel bars are required. Horizontally, the design calls for 25 ft 3 in. No. 6 pairs at 2-, 7-, and 13-ft stations. Vertically, No. 5 paired-bars are tied every 10 ft. The vertical bars are 16 ft long. Do not include the cost of the concrete and its placement. Find the total cost for the retaining wall structure, cost per yd³of concrete placed, and the cost per ft²of area in contact with the concrete surface.

(Hints: Use 1-by-6-in. tongue-and-grooved matched pine with rough and smooth sides, 2-by-4-in. lumber for studs and wales. Braces are 10-ft studs and are required every 4 lin ft, both sides. The oak stakes cost $0.65 each. Assume that lumber is used two times, which allows the overlooking of waste for this problem. Cost of lumber are $150 per 100 bft. To overcome the pressure of concrete, the spacing for the vertical studs is 20 in. and for the horizontal wales is 25 in. Spacing of ties is 30 in., and the area per tie is 5 ft². Nails are $0.50 per lb. Portable electric equipment prorated first-cost and use contributes $1 per hour of operation, and its capacity is rated at 400 bft/hr for all lumber. A scheduled crew consists of a carpenter, a helper and foreman for 50% time for the forms. A reinforcing crew consists of a steel and a common laborer.)

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