Rev. 1-22-97

BIN-TYPE RETAINING WALL

714-R-003

DESCRIPTION. This work shall consist of metal bin-type retaining walls constructed in accordance with these specifications and in conformance with the lines, grades, and dimensions shown on the plans, or as otherwise directed.

MATERIALS. Metal bin-type retaining walls shall consist of a plurality of pairs of columns. One column of each pair is to be in the plane of the pairs of columns shall be spaced longitudinally with overlapping U-shaped facing and rear members called stringers, and transversely with overlapping U-shaped tie members called spacers. The necessary bolts and appurtenances shall be furnished for complete assembly of the units into a continuous closed face wall of connected bins.

The units in the wall shall be in accordance with the dimensions and gages shown on the plans. The units shall present a uniform workmanlike appearance when assembled.

The base metal of the galvanized sheets shall be in accordance with AASHTO M 218.

The base metal sheets shall be galvanized on both sides by mean of the not-dip process. A coating of prime western spelter or equal shall be applied at the rate of not less than 610 g/m5 (2 oz/sft) of double exposed surface. If the average spelter coating as determined from the required samples is less than 610 g/m5 (2 oz/sft), or if one sample is less than 550 g/m5 (1.8 oz/sft) of double exposed surface, the lot sampled shall be rejected. The finished sheets shall be of first class commercial quality, free from injurious defects, such as blisters, flux, and uncoated spots.

CONSTRUCTION REQUIREMENTS. The wall members shall be constructed of metal of the gage shown on the plans, but not less than 16 gage. All units shall be so fabricated that units of the same nominal size shall be fully interchangeable. No drilling, punching, or drifting to correct defects in manufacture will be permitted. All units having improperly punched holes shall be promptly replaced by the manufacturer with no additional payment. The ends of all stringers and spacers shall be bolted to corner columns by means of connecting channels.

The proper curvature for the face of a wall constructed on a curve shall be obtained by the use of shorter stringers in the front or rear panels of retaining walls as shown on the plans or as otherwise directed.

The wall height and depth may be varied. Two or more designs of retaining walls may be incorporated in the same wall by the use of standard split columns to make the connection on the step-back.

The units shall be erected as shown on the plans. Members shall be handled carefully and those which are damaged shall be removed and new members substituted with no additional payment.

The filling for the interior of the bin and behind the wall shall be B borrow placed in layers not to exceed 150 m (6 in.) in thickness and tamped or consolidated as directed. Compaction by saturation will not be permitted. Backfilling behind the wall shall progress with the filling of the bins and shall not be carried ahead of binfill. Existing slopes, which are shaped so as to cause a wedge action in the backfill, shall be step-cut or benched before backfilling.

METHOD OF MEASUREMENT. This work will be measured by the square meter (square foot) of facial area for each design height and thickness of wall complete in place and accepted.

BASIS OF PAYMENT. This work will be paid for at the contract unit price per square meter (square foot) for retaining wall, bin-type. The B borrow required and used for backfilling, complete, in place and accepted, will be paid for at the contract unit price per cubic meter (cubic foot) for B borrow for structure backfill.

The costs of furnishing, handling, and installing the metal units including all materials, bolts, and appurtenances; necessary excavation; and all labor, equipment, and necessary incidentals shall be included in the cost of this work.