Proper Construction

Incorporate construction specifications, detail, notes, and plan requirements to assist the contractor in successfully completing green infrastructure installations. For example:

• Require geotechnical engineer to observe excavation and suitability of subgrades; perform soil testing on subsurface layers to remain and on all replacement soil mixes.
• Require under-excavation of infiltration-based systems during construction, with final excavation to design subbase depth and installation of engineered soil layers to be performed only after heavy equipment is no longer traversing the area and after the entire drainage area is stable.
• Specify uniformly graded coarse sand as the surface layer of infiltration basins.
• Specify bioretention soil based on the expected silt and nutrient loading to the BMP.
• Require temporary forebays at all inlets to BMPs.
• Require silt fence to protect BMP perimeters during construction.
• Require sod to stabilize steep slopes around BMPs.
• Design wet pond depths to allow for the accumulation of silt while maintaining at least minimum design depth.
• Utilize low-ground-pressure vehicles to minimize soil compaction during construction.