Define culvert and list common materials and design considerations.

• A. A drainage ditch that sits on the surface; materials include wood and asphalt; design focuses on appearance and noise.
• B. A conduit for water under a road; materials include concrete, metal, HDPE; design focuses on capacity, headwater, invert, and scour protection.
• C. A vertical shaft in a dam for water release; materials include concrete and steel; design focuses on maintenance access.
• D. A tunnel through a mountain; materials include shotcrete; design focuses on ventilation and blasting safety.

Answer: (B)