When large stones or bedrock are encountered, the bedding material backfill to grade must be what?

• A. Portland cement and sand.
• B. Sand, gravel or crushed stone that passes a 3/4-inch sieve.
• C. Concrete.
• D. Topsoil.

Answer: (B)

When large stones or bedrock are present, the pipe needs a bedding that can be packed firmly around it without trapping water or causing movement. The best choice is a granular backfill made of sand, gravel, or crushed stone that passes a 3/4-inch sieve. This material fills gaps around irregularities, distributes load evenly, and allows drainage so the pipe remains stable as the surrounding earth settles. Using Portland cement and sand would set into a rigid bed and resist drainage, risking stress on the pipe. Concrete is even more rigid and can transfer loads in a way that may crack or damage the pipe. Topsoil is unsuitable because it compacts and settles unevenly, offering little support or drainage. So, the correct approach is granular material that passes the 3/4-inch sieve.