Specifications include, but are not limited to: Ditching: 1. Ditch will be excavated deep enough to drain the road base and handle an expected runoff depth of 1.5’ – 2’ deep. 2. Ditch bank side slopes should be a maximum 2:1 horizontal to vertical ratio. 3. Ditch should be at least 2’ wide forming a slightly rounded (parabolic) shape to help slow and disperse water. 4. Outlet the ditch into a vegetated area whenever possible. Culvert Installation: 1. Bottom width of culvert trench should be twice the width of the culvert, with sidewalls no steeper than 1:1. 2. A 0.5% positive slope is the minimum to allow for positive drainage flow. 3. A minimum of 18” to 24” of fill is required over the culvert, with required compaction in 6”lifts. Lifts should be soaked with water to achieve maximum compaction.
