A silt fence is to be installed around a sensitive wetland area downslope from a new road construction. The soil is sandy, and the anticipated runoff velocity is moderate. What is the recommended trench depth for embedding the silt fence fabric to ensure maximum effectiveness?

Question: A silt fence is to be installed around a sensitive wetland area downslope from a new road construction. The soil is sandy, and the anticipated runoff velocity is moderate. What is the recommended trench depth for embedding the silt fence fabric to ensure maximum effectiveness?

Answer options: ✅ Minimum 150 mm (6 inches) deep.

• Maximum 50 mm (2 inches) deep.
• No trenching is necessary; just secure it with stakes.
• As deep as the fabric allows, regardless of soil type.

Correct answer: Minimum 150 mm (6 inches) deep.

Explanation: Proper silt fence installation, vital for its effectiveness, requires embedding the fabric into a trench. A minimum depth of 150 mm (6 inches) is generally recommended across industry standards (e.g., OPSWA, WSBC best practices) to prevent undermining and ensure sediment retention.