Construction: final excavated grade and verification

LID designs typically have very specific grading requirements. Verifying depths and slopes is critical for optimal performance of the facility. For example, if the design calls for a channel with a 1% slope, the channel may not function as designed if it has a 2% slope instead. Similarly, if the designs call for 1 metre of excavation from grade and only 90 cm are excavated, it will not have enough storage space to meet the design criteria.
Construction steps

1. Excavate from the rough grade to the finish grade using appropriate equipment. This is often done with hand tools.
2. Confirm excavation depths and slopes using appropriate equipment (transit levels, global navigation satellite systems, etc.)

Key inspection points

• Confirm final excavated depths and slopes.

Mistakes to avoid

• “Eye-balling” depths and slopes

Low Impact Development. A stormwater management strategy that seeks to mitigate the impacts of increased urban runoff and stormwater pollution by managing it as close to its source as possible. It comprises a set of site design approaches and small scale stormwater management practices that promote the use of natural systems for infiltration and evapotranspiration, and rainwater harvesting.