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Smaller dump trucks, often those mounted on a pickup frame, will have comparably less capacity, sometimes as little as 1-1/2 cubic yards. A cubic yard represents a block of material that measures three feet on each side. Sand can weigh upwards of 3,000 pounds per cubic yard. Dry mulch can weigh as little as 700 pounds per yard. Wet compost mulch can weigh as much as at 1,500 pounds per yard. Most dump trucks have an open-box bed and operate by hydraulics. The back of the bed is hinged to the back of the truck so the front can be raised to dump material out.