For proper installation of a silt fence, a trench ____ by _____ must be excavated.

For the proper installation of a silt fence, a trench is required to be excavated at a depth of 4 inches and a width of 4 inches. This specification ensures that the silt fence is installed securely and effectively, allowing it to function as intended for controlling sedimentation.

When the silt fence is placed in the trench, it should be embedded sufficiently to prevent water from flowing underneath it and to hold the fabric firmly in place. The 4-inch depth is adequate to ensure that the base of the fence is anchored properly, which is crucial for maintaining its stability during heavy rains or storms when sediment-laden runoff might occur. The width also allows for a sufficient area of the fence to be buried, further enhancing its performance against erosive forces.

Overall, adhering to these installation dimensions is critical for ensuring that the silt fence provides the intended sediment control measures.