Where should a berm be located relative to the trench in cup trench construction?

• A. On the outermost downhill side.
• B. On the uphill side.
• C. Across the trench center.
• D. No berm is used in cup trench construction.

Answer: (A)

In cup trench construction, the berm is kept on the downhill outer edge to act as a protective barrier that catches embers, debris, and soil that could roll downhill into the trench or along the fireline. Building the berm on the downhill side uses gravity to help form a stable edge that blocks heat and flames from reaching the trench, keeping the line safer and more effective. Placing a berm on the uphill side wouldn’t stop downhill fire activity, and a berm across the trench center would undermine the trench’s integrity. Also, skipping a berm isn’t aligned with cup trench practice, which relies on that protective downhill berm to enhance the line.