Cottonwood Creek Bridge (41C0006) features a patented flooring system designed for industrial buildings called the Thomas slab. It is similar to the Turner Mushroom System (visible on bridges 25C0116 and 29C0232), but it never achieved the same popularity because of the space-consuming beams. The Thomas slab flooring system utilizes a concrete slab supported on longitudinal beams with a reinforcement bar placed in a Warren truss configuration. William Thomas designed the bridge; he was best-known for his patented three-hinge arch bridge design. This was the only California example of a Thomas slab bridge.