Environmental Engineering Reference
In-Depth Information
• Curb cuts with grading for sheet flow entrance
• Roof leaders with direct surface connection
• Entering velocities must be nonerosive where concentrated runoff enters
the rain garden—use erosion control mats or blankets and/or inlet energy
dissipaters such as rocks or splash blocks
Ponding area
• Provides temporary surface storage of runoff
• Provides evaporation for a portion of runoff
• Allows sediment to settle
• Depth no more than 6 to 18 in. for aesthetics, functionality, and safety
Plant material
• Absorbs stormwater through transpiration
• Root development creates pathways for infiltration
• Bacteria component of the plant-soil community helps create healthy soil
structure with water quality benefits
• Can improve site appearance
• Provides habitat for animals
• Should be native plant species
• Ensure that plants can tolerate snowmelt chemicals, if applicable (at high
elevations)
• Should be placed according to water and saturation tolerance
Surface mulch or organic layer
• Acts as a filter for pollutants in runoff
• Protects underlying soil from drying and eroding
• Reduces the likelihood of weed establishment
• Provides a medium for biological growth, decomposition of organic material,
and adsorption and bonding of heavy metals
• Wood mulch should be shredded for easier decomposition—compost or leaf
mulch is preferred
Planting soil/volume storage bed
• Makes water and nutrients available to plants
• Enhances biological activity and encourages root growth
• Provides storage of stormwater by the voids within the soil particles
• Provides surface for adsorption of nutrients in runoff
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