What should be done to the surface of compacted fill before adding topsoil in embankment construction?

Scarifying the surface layer of compacted fill is essential before adding topsoil in embankment construction because it improves the bonding between the existing soil and the new topsoil. This process involves breaking up the surface to create a rough texture, which facilitates better adhesion and ensures that the new layer integrates well with the compacted fill beneath. This is crucial for promoting plant growth and minimizing erosion, as it allows roots to penetrate deeper and establish a stronger hold.

Scarification also helps in creating a more uniform surface, which reduces the chances of water pooling or runoff, thus enhancing the overall effectiveness of the stormwater management system. Proper preparation of the surface is particularly important in preventing the layering phenomenon, where water may accumulate between different soil types, leading to drainage problems.

Moistening the layer, covering it with a tarp, or leaving it undisturbed can result in poor soil structure and hinder the interaction between topsoil and the compacted fill, impacting the stability and performance of the embankment.