Bioretention: Construction checklist

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

Erosion and Sediment Control
	Bioretention locations should be blocked from construction traffic and should not be used for erosion and sediment control.
	Proper erosion and sediment controls should be in place for the drainage area.

Materials • Gravel for the underdrain should be clean and washed; no fines should be present in the material. • Underdrain pipe material should be perforated and of the correct size. • A cap should be placed on the upstream (but not the downstream) end of the underdrain. • Biomedia should be tested to confirm that it meets specifications. • Mulch composition should be correct.

Elevations Elevations of the following items should be checked for accuracy: • Depth of the gravel and invert of the underdrain • Inverts for inflow and outflow points • Filter depth after biomedia is placed • Ponding depth provided between the surface of the filter bed and the overflow structure • Mulch depth

Landscaping and Stabilization • Correct vegetation should be planted. • Pretreatment area should be stabilized. • Drainage area should be stabilized prior to directing water to the bioretention.

The following items should be checked after the first rainfall event, and adjustments should be made as necessary: • Outfall 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 should drain within 24 hours of the end of the storm event. The filter media bed should fully drain within a maximum period of 72 hours. • Excessive sediment accumulation should not be present.

Soil, 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.

A shallow excavated surface depression containing prepared filter media, mulch, and planted with selected vegetation.

Soil, 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.

The 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.

A perforated pipe used to assist the draining of soils.

Soil particles with a diameter less than 0.050 mm.

A perforated pipe used to assist the draining of soils.

a top dressing over vegetation beds that provides suppresses weeds and helps retain soil moisture in bioretention cells, stormwater planters and dry swales.

Initial 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.

The 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.

A shallow excavated surface depression containing prepared filter media, mulch, and planted with selected vegetation.

The point, location, or structure where wastewater or drainage discharges from a sewer pipe, ditch or other conveyance to a receiving body of water.

The 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.