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no edit summary
==Design==
==Design==
[[Bioretention: Sizing]]
==Inlets==
{{:Inlets}}
===Inlets===
==Overflow==
Inlets for BMPs in the right of way should be located:
{{:Overflow}}
*At all sag points in the gutter grade
*Immediately upgrade of median breaks, crosswalks, and street intersections.
It is recommended to include multiple inlets, sized to distribute inflow along the length of the practice or between multiple facilities, where feasible, rather than concentrating all inflow into a single location. ([[Overflow|Offline overflow]]).
====Trench drains====
Trench drains are long, covered channels that collect and direct water into the BMP. They are 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.
====Curb cuts====
[[Curb cuts]] are breaks along the length of a curb system to allow water to flow into a LID/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.
<gallery mode="packed" widths=200px heights=200px>
County Court Blvd biofilter spillway inlet and CB overflow.jpg|OPSD 605.040 Asphalt Spillway inlet to biofilter swale and road catch basin overflow outlet. County Court Blvd., Brampton, ON.
Curb inlet Miss Rd.jpg|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.
LSRCA curb.jpg| [[Curb cuts|Curb cut]] used as a controlled [[overflow]] route from [[permeable pavements|permeable pavement]] to a [[bioretention]] facility with monitoring well, Lake Simcoe Region Conservation Authority, Newmarket, ON.
Curb cut CNT.jpg| Curb cut into a bioretention facility in Hinsdale, IL. [[Stone]] in the center of the facility reduces erosion and dissipates power inflow around the [[Inlets|inlet]] area. A monitoring/maintenance [[well]] can be seen in the foreground. Photo credit: [[Acknowledgements|CNT]]
Curb cut AV.jpg | Curb cut into a bioretention facility in Brown Deer, WI. Stone is used to reduce erosion around the inlet area. Photo credit: [[Acknowledgements|Aaron Volkening]]
Ajax_curb_inlet.JPG| Curb cut into a bioretention facility in Ajax, ON.
IMAX Stone Inlet.jpeg| [[Stone]] lined inlet at IMAX site in Mississauga
Curb inlet grade.jpg| 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|permeable pavement]].
</gallery>
====Inlet sumps====
An inlet sump is recommended to settle and separate sediments 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]], supported [[soil cells]] or underground practices such as [[trenches]] or [[chambers]].
Sump inlets should not be sited where pedestrians will have to negotiate with them.
{{:Inlet sumps: Gallery}}
====Depressed drains====
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.
{{:Trench drains: Gallery}}
[[File:Routing.png|thumb|Conceptual diagram of the excess routing alternatives: On the left, excess flow leaves the [[bioswale]] via an overflow; on the right, excess flow is diverted so that only the design volume enters the cell.]]
===Overflow===
====Routing====
*Infiltration facilities can be designed to be inline or offline from the drainage system. See figure to the right for an illustration.
*Inline facilities accept all of the flow from a drainage area and convey larger event flows through an overflow outlet. The overflow must be sized to safely convey larger storm events out of the facility. The overflow must be situated at the maximum surface ponding elevation or furthest downgradient end of the facility to limit surface ponding during periods of flow in excess of the facility storage capacity.
*Offline facilities use flow splitters or bypass channels that only allow the design storm runoff storage volume to enter the facility. Higher flows are conveyed to a downstream storm sewer or other BMP by a flow splitting manhole weir or pipe, or when the maximum surface ponding depth has been reached, by by-passing the curb opening and flowing into a downstream catchbasin connected to a storm sewer.
====Overflow Elevation====
The invert of the overflow should be placed at the maximum water surface elevation of the practice (i.e. the maximum surface ponding level).
A good starting point is 150 to 350 mm above the surface of the mulch cover. However, consideration should be given to public safety, whether or not an underdrain is included, the time required for ponded water to drain through the filter bed surface, and if no underdrain is present, into the underlying native soil (must drain within 48 hours).
See [[Bioretention: Sizing]] for more details.
====Freeboard====
{{:freeboard}}
====Overflow Outlet Options====
Metal grates are recommended (over plastic) in all situations.
{| class="wikitable sortable"
! Feature
! Anti Vandalism/Robust
! Lower Cost Option
! Self cleaning
|-
| Dome grate
|
|
| x
|-
| Flat grate
|
| x
|
|-
| Catch basin
| x
|
|
|-
| Ditch inlet catch basin
| x
|
| x
|-
| [[Curb cut]]
| x
| x
| x
|}
==Inspection and Maintenance==
Maintenance requirements for [[bioswales]] is similar to [[swales00 and [[bioretention]]. It typically involve a low level of activity after [[vegetation]] becomes established. [[Grass]] channel maintenance procedures are already in place at many municipal public works and transportation departments. These procedures should be compared to the recommendations provided on the [[Inspection and Maintenance: Enhanced Swales]] page to assure that the infiltration and water quality benefits of enhanced grass swales are preserved.
Meanwhile, bioswales also require regular weeding, pruning, and mulching, similar to other landscaped areas, as well as the removal of trash, debris and sediment accumulated in pretreatment areas, inlets and outlets.
Inspections should occur twice annually (spring and late fall) and after major storm events. Inspect for vegetation density (≥ 80% coverage), damage by foot or vehicle traffic, erosion, debris and sediment accumulation, and damage to any [[pretreatment]] devices.<br>
Cleanouts and access points should be provided to allow clean-out of the underdrain and overflow pipe. Camera inspection of these pipes should be conducted every 5 years to ensure pipes are free of roots, sediment and debris. Hydraulic flushing or root removal may be needed to clear debris or obstructions.
<br>
Take a look at the [[Inspection and Maintenance: Bioretention & Bioswales]] page and the[[Inspection and Maintenance: Enhanced Swales]] page by clicking below for further details about proper inspection and maintenance practices:
{{Clickable button|[[File:Cover Photo.PNG|150 px|link=https://wiki.sustainabletechnologies.ca/wiki/Inspection_and_Maintenance:_Bioretention_%26_Bioswales]]}} {{Clickable button|[[File:Cover Photo swales.PNG|150 px|link=https://wiki.sustainabletechnologies.ca/index.php title=Inspection_and_Maintenance:_Enhanced_Swales&action=edit]]}}
==Materials==
==Materials==
All forms of bioretention are complex in their structure, so please follow separate links for the materials.
All forms of bioretention are complex in their structure, so please follow separate links for the materials.