On flat or rolling ground, cut and sidecast construction is acceptable.
- All material is sidecast.
- Fill must be stable.
- Do not use sidecast fill if it could enter a waterway.
- Use a bench to retain fill where required, or use the “cut and bench fill” construction method (see next section).
- Sidecast material is contained within the roadway by windrowed slash.
- It has low risk of movement.
- Earthworks have been minimised.
- Extra earthworks add cost and can increase environmental risks.
How steep is too steep for sidecasting?
There is no rule as it depends on the site, however:
- Most non-compacted fill will not be stable if steeper than 60% (30 degrees). It changes depending on the material. Rock fill is the most stable.
- Once the ground gets steeper than about 40% (20 degrees) the fill is harder to contain and stabilise.
- The sidecast is contained and stable.
- The fill slope is less than 60% (30 degrees).
- This slope is too steep for sidecast construction.
- Material has gone to the gully bottom. Sediment could enter a waterway.
- The fill has spilled 50 m down the slope (see the vehicle, arrowed, for scale).