Bioretention: Construction checklist

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Common construction pitfalls can be avoided with careful construction supervision that focuses on the following aspects:

Erosion and SedimentSoil, sand and minerals washed from land into water, usually after rain. They pile up in reservoirs, rivers and harbors, destroying fish-nesting areas and holes of water animals and cloud the water so that needed sunlight might not reach aquatic plans. Careless farming, mining and building activities will expose sediment materials, allowing them to be washed off the land after rainfalls. Control
  BioretentionA shallow excavated surface depression containing prepared filter media, mulch, and planted with selected vegetation. locations should be blocked from construction traffic and should not be used for erosion and sedimentSoil, sand and minerals washed from land into water, usually after rain. They pile up in reservoirs, rivers and harbors, destroying fish-nesting areas and holes of water animals and cloud the water so that needed sunlight might not reach aquatic plans. Careless farming, mining and building activities will expose sediment materials, allowing them to be washed off the land after rainfalls. control
Proper erosion and sedimentSoil, sand and minerals washed from land into water, usually after rain. They pile up in reservoirs, rivers and harbors, destroying fish-nesting areas and holes of water animals and cloud the water so that needed sunlight might not reach aquatic plans. Careless farming, mining and building activities will expose sediment materials, allowing them to be washed off the land after rainfalls. controls should be in place for the drainage areaThe total surface area upstream of a point on a stream that drains toward that point. Not to be confused with watershed. The drainage area may include one or more watersheds.
Materials
  Gravel for the underdrainA perforated pipe used to assist the draining of soils. should be clean and washed; no finesSoil particles with a diameter less than 0.050 mm. should be present in the material
UnderdrainA perforated pipe used to assist the draining of soils. pipe material should be perforated and of the correct size (when specified in design)
A cap should be placed on the upstream (but not the downstream) end of the underdrainA perforated pipe used to assist the draining of soils. (when specified in design)
Biomedia should be tested to confirm that it meets specifications
Mulcha top dressing over vegetation beds that provides suppresses weeds and helps retain soil moisture in bioretention cells, stormwater planters and dry swales. composition should be correct
Elevations
  Depth of the gravel and invert of the underdrainA perforated pipe used to assist the draining of soils.
Inverts for inflow and outflow points
Filter mediaThe engineered soil component of bioretention cell or dry swale designs, typically with a high rate of infiltration and designed to retain contaminants through filtration and adsorption to particles. depth
Ponding depth provided between the surface of the filter bed and the overflow structure
Mulcha top dressing over vegetation beds that provides suppresses weeds and helps retain soil moisture in bioretention cells, stormwater planters and dry swales. depth
Landscaping and Stabilization
  Correct vegetation should be planted
PretreatmentInitial capturing and removal of unwanted contaminants, such as debris, sediment, leaves and pollutants, from stormwater before reaching a best management practice; Examples include, settling forebays, vegetated filter strips and gravel diaphragms. area should be stabilized
Drainage areaThe total surface area upstream of a point on a stream that drains toward that point. Not to be confused with watershed. The drainage area may include one or more watersheds. should be stabilized prior to directing water to the bioretentionA shallow excavated surface depression containing prepared filter media, mulch, and planted with selected vegetation.
The following items should be checked after the first rainfall event, and adjustments should be made as necessary:
  OutfallThe point, location, or structure where wastewater or drainage discharges from a sewer pipe, ditch or other conveyance to a receiving body of water. protection/energy dissipation at concentrated inflow should be stable
Flow should not concentrate and should spread evenly over the filter bed
Ponded water at the surface of the bioretenton facility must drain within 24 hours of the end of the storm event.
The biomedia should fully drain within a maximum period of 72 hours
Excessive sedimentSoil, sand and minerals washed from land into water, usually after rain. They pile up in reservoirs, rivers and harbors, destroying fish-nesting areas and holes of water animals and cloud the water so that needed sunlight might not reach aquatic plans. Careless farming, mining and building activities will expose sediment materials, allowing them to be washed off the land after rainfalls. accumulation should not be present