Inlets

Inlets for BMPs in the right of way should be located:

• At all sag points in the gutter grade
• Immediately upgrade of median breaks, crosswalks, and street intersections.

Trench drains	Curb cuts	Inlet sumps	Depressed drains
A long, covered channel that collects directs water into the BMP. An excellent solution for streets where walking across the entire surface is to be encouraged. They can be designed as detectable edges or part of a detectable edge, and may be used to help define curbless or 'complete streets'. Trenches may either be shallow (where runoff volume is less of an issue) or deep and covered by a metal grate. Deeper trench drains may gather sediment and require frequent maintenance. Drains may be configured either perpendicular or parallel to the flow direction of the roadway, collecting runoff and directing to a single inlet in the BMP.	Inlet aprons or depressions increase inflow effectiveness of curb cuts. Steeply angled aprons can be hazardous, especially to people bicycling. Curbside and protected bike lanes along concrete aprons should be at least 1.8 m to give cyclists adequate clear width from the curb and any pavement seams. Aprons can also be marked visually to indicate their perimeter. For aprons into bioretention, the curb may angle into the cell to improve conveyance of gutter flow into the facility. Aprons typically drop 50 mm into the bioretention cell, with another 50 mm drop behind the curb to maintain inflow as debris collects. A depressed concrete apron can be cast in place or retrofitted in by grinding down the existing concrete pavement. Where the curb alignment along the street is straight, the curb opening may optionally have a bar across the top of the inlet.	An inlet sump is recommended to settle and separate sediment from runoff where a large amount of debris is expected. Water drains into a catch basin, where debris settles in its sump. After pretreatment, water drains via a pipe or opening into the BMP. The sump can be directly connected to a perforated underdrain pipe to distribute the flow to the bioretention or connected tree pits. Sump inlets should not be sited where pedestrians will have to negotiate with them.	Runoff in the gutter drops into a grate-covered drain before flowing into the BMP. Drain covers must be compatible with bicycling and walking; grid covers are preferred. Depressed drains are a potential solution for bioretention cells on sloped streets where directing runoff into the cell is a challenge. This style of inlet can be combined with a curb cut, to maintain capacity in case debris clogs the grate.
	OPSD 605.040 Asphalt Spillway inlet to biofilter swale and road catch basin overflow outlet. County Court Blvd., Brampton, ON. This curb cut has been sawn into existing concrete as part of a retrofit. Note the temporary (erosion log) and permanent stone erosion control measures in place. Mississauga Road, ON. Curb cut used as a controlled overflow route from permeable pavements to a bioretention facility with monitoring well, Lake Simcoe Region Conservation Authority, Newmarket, ON. Curb cut into a bioretention facility in Hinsdale, IL. Stone in the center of the facility reduces erosion and dissipates power inflow around the inlet area. A monitoring/maintenance well can be seen in the foreground. Photo credit: CNT Curb cut into a bioretention facility in Brown Deer, WI. Stone is used to reduce erosion around the inlet area. Photo credit: Aaron Volkening Curb cut into a bioretention facility in Ajax, ON. Stone lined inlet at IMAX site in Mississauga The grading around this inlet prevents flow in the correct direction. i.e. from the pavement onto the grass. Not too critical in this example, as the surface is permeable pavements. Curb cut into a rain garden on a green street in Newmarket, ON. Curb cut leading into a small bioretention cell in Brampton, ON. Curb cut leading to a bioswale in Brampton, ON.

External links

https://nacto.org/publication/urban-street-stormwater-guide/stormwater-elements/bioretention-design-considerations/inlet-design/

Best management practice. State of the art methods or techniques used to manage the quantity and improve the quality of wet weather flow. BMPs include: source, conveyance and end-of-pipe controls.

The portion of water precipitated onto a catchment area, which then flows as surface discharge from the catchment area past a specified point.

Water from rain, snow melt, or irrigation that flows over the land surface.

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.

Ground depression acting as a flow control and water treatment structure, that is normally dry.

The portion of water precipitated onto a catchment area, which then flows as surface discharge from the catchment area past a specified point.

Water from rain, snow melt, or irrigation that flows over the land surface.

A mixture of mineral aggregates bound with bituminous materials, used in the construction and maintenance of paved surfaces.

A bioretention BMP featuring an impermeable liner and underdrain that prevents infiltration of runoff into the underlying native soil; provides sedimentation and filtration of urban runoff as it passes through the mulch layer, engineered filter media and vegetation root zone.

A bioretention cell that features an impermeable liner that collects and treats stormwater through sedimentation and filtration only (i.e., no infiltration).

A shallow constructed channel, often grass-lined, which is used as an alternative to curb and channel, or as a pretreatment to other measures. Swales are generally characterized by a broad top width to depth ratio and gentle grades.

Includes the protection of soil from dislocation by water, wind or other agents.

Linear bioretention cell designed to convey, treat and attenuate stormwater runoff. The engineered filter media soil mixture and vegetation slows the runoff water to allow sedimentation, filtration through the root zone, evapotranspiration, and infiltration into the underlying native soil.