Box culverts designed in accordance with ASTM C1577 Standard Specification for Precast Reinforced Concrete Monolithic Box Sections for Culverts, Storm Drains, and Sewers and Caltrans Standards D83A and D83B for Precast Reinforced Concrete Box Culvert.  Loading per AASHTO LRFD Bridge Design Specifications 6th Edition HL-93.