Changes

[[File:Treatmenttrain TRCA.JPG|thumb|550px|Example of a generalization of utilizing a “Treatment Train Approach” illustrated here. Using [[permeable pavement]] as a source control/lot control on your business/residential property, effluent then flows into conveyance control such as an [[Exfiltration trench|exfiltration system]], used in conjunction with the minor stormwater system as shown above. and then flowing into a stormwater management pond (wet pond) for additional erosion and flood control (TRCA, n.d.).<ref>TRCA, n.d. Understand - Stormwater Management. Accessed: https://trca.ca/conservation/stormwater-management/understand/</ref>]]

[[File:Treatmenttrain TRCA.JPG|thumb|550px|Conceptualization of the “Treatment Train Approach”. Source controls (e.g. [[permeable pavement]], [[rain gardens]]) drain to conveyance practices (e.g [[enhanced grass swale|grass swale]], [[exfiltration trench|exfiltration system]]) within the drainage network, and these in turn drain to end-of-pipe practices (e.g. stormwater management pond, [[infiltration chambers|underground tank]].  The upstream treatment practices are typically designed to provide water quality treatment whereas the large storage end-of-pipe facilities provide erosion and flood control, and may also have a water quality polishing function (TRCA, n.d.).<ref>TRCA, n.d. Understand - Stormwater Management. Accessed: https://trca.ca/conservation/stormwater-management/understand/</ref>]]

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==Overview==

==Overview==

A treatment train uses a combination of lot-level or source (LID), conveyance and/or end-of-pipe practices to meet water quality, water quantity, water balance, and erosion design criteria for the site.  These may be implemented to reduce the burden of facility maintenance, address a broader range of design criteria, increase overall treatment system performance, and/or control the rate of flow through downstream facilities.

A treatment train uses a combination of lot-level or source (LID), conveyance and/or end-of-pipe practices to meet water quality, water quantity, water balance, and erosion design criteria for the site.  These may be implemented to reduce the burden of facility maintenance, address a broader range of design criteria, increase overall treatment system performance, and/or control the rate of flow through downstream facilities.<br>

{|class="wikitable"

{|class="wikitable" style="width: 1250px;"

|+Examples of stormmwater practices that may be used in treatment trains<ref>Ministry of the Ontario Conservation & Parks (MECP). 2021. Understanding Stormwater Management: An Introduction to Stormwater Management Planning and Design. Major concepts and environmental concerns to consider in the Ministry of the Environment’s Stormwater Management Planning and Design Manual 2003. Updated: July 15, 2021. Accessed: https://www.ontario.ca/page/understanding-stormwater-management-introduction-stormwater-management-planning-and-design</ref>

|+Examples of stormmwater practices that may be used in treatment trains<ref>Ministry of the Ontario Conservation & Parks (MECP). 2021. Understanding Stormwater Management: An Introduction to Stormwater Management Planning and Design. Major concepts and environmental concerns to consider in the Ministry of the Environment’s Stormwater Management Planning and Design Manual 2003. Updated: July 15, 2021. Accessed: https://www.ontario.ca/page/understanding-stormwater-management-introduction-stormwater-management-planning-and-design</ref>

|-

|-

*Temporary Parking lot storage

*Temporary Parking lot storage

*Oversized storm sewer storage

*Oversized storm sewer storage

|

|

|-

|-

*[[swales]]

*[[swales]]

*[[Vegetated filter strips]]

*[[Vegetated filter strips]]

|

|

|-

|-

*[[Filter Media Additives for Phosphorus Removal|Media Filters]]

*[[Filter Media Additives for Phosphorus Removal|Media Filters]]

*[[Pretreatment#concentrated underground flow|Proprietary concentrated underground flow features]]

*[[Pretreatment#concentrated underground flow|Proprietary concentrated underground flow features]]

 

|

|

|-

|-

*[[Infiltration chambers|Infiltration basins]]

*[[Infiltration chambers|Infiltration basins]]

*[[Stormwater Tree Trenches]]

*[[Stormwater Tree Trenches]]

|}

|}<br>

==Types of Treatment Trains==

==Types of Treatment Trains==

These are the most common types of treatment trains.  They typically involve installation of one or more [[pretreatment]] devices upstream or at the [[inlet]] of the primary stormwater treatment facility.   

These are the most common types of treatment trains.  They typically involve installation of one or more [[pretreatment]] devices upstream or at the [[inlet]] of the primary stormwater treatment facility.   

[[File:Treatment train air force.JPG|thumb|800px|An example of a stormwater treatment train approach at Tyndall Air Force Base in Florida, in a coastal environment. This example includes source controls of [[bioretention]] parking islands, [[permeable pavement]], and conveyance controls of[[swales]], a natural infiltration basin in a forested woodlot, and end-of-pipe controls of [[dry ponds]], [[constructed wetlands]] and coastal dunes. All of these features help to reduce traditional SWM features' maintenance, treatment and rehabilitation coasts, while also reducing pollutants into the receiving waterbody. (U.S Air Force, 2020)<ref>U.S. Air Force. n.d. LANDSCAPE MASTER PLAN - C. Site Development Criteria.  CO4. Stormwater - C04.3.2 Stormwater at Individual Building Sites. Accessed: https://www.tyndallifs.com/images/LMP_pdf/TAFB_Final_LandscapeMasterPlan_2020-09-24_SectionC04.pdf</ref>]]

[[File:Treatment train air force.JPG|thumb|800px|. An example of a stormwater treatment train approach within a coastal environment at Tyndall Air Force Base in Florida. This example includes source controls of [[bioretention]] parking islands, [[permeable pavement]], combined with [[swales|swale]] based conveyance controls and end-of-pipe controls using an infiltration basin, [[dry ponds]], [[wetlands|constructed wetlands]] and coastal dunes. All of these features help to reduce traditional maintenance, treatment and rehabilitation costs of the SWM features, while also reducing pollutants discharged to the receiving waterbody (U.S Air Force, 2020)<ref>U.S. Air Force. n.d. LANDSCAPE MASTER PLAN - C. Site Development Criteria.  CO4. Stormwater - C04.3.2 Stormwater at Individual Building Sites. Accessed: https://www.tyndallifs.com/images/LMP_pdf/TAFB_Final_LandscapeMasterPlan_2020-09-24_SectionC04.pdf</ref>.]]

'''Example''': Runoff into larger treatment practices such as [[bioretention]] or [[Stormwater Tree Trenches|stormwater tree trenches]] may be pretreated by [[Inlet sumps: Gallery|concrete sumps]] at [[curb cut]] inlets, [[forebays]] or catch basin inserts, which are designed to capture coarse sediment, debris and trash.  Centralizing sediment and trash captured at the inlet or entrance to the facility reduces maintenance by preventing [[filter media]] [[clogging]] and limiting the area over which sediment and trash needs to be removed.  In some cases, pre-treatment device clean-outs may be incorporated into existing municipal catch basin cleaning programs.   

'''Example''': Runoff into larger treatment practices such as [[bioretention]] or [[Stormwater Tree Trenches|stormwater tree trenches]] may be pretreated by [[Inlet sumps: Gallery|concrete sumps]] at [[curb cut]] inlets, [[forebays]] or catch basin inserts, which are designed to capture coarse sediment, debris and trash.  Centralizing sediment and trash captured at the inlet or entrance to the facility reduces maintenance by preventing [[filter media]] [[clogging]] and limiting the area over which sediment and trash needs to be removed.  In some cases, pre-treatment device clean-outs may be incorporated into existing municipal catch basin cleaning programs.   

[[File:Sump inelt to chamber system.JPG|thumb|500px|Example of a [[Pretreatment#Concentrated underground flow|overland flow sump inlet]] allowing sediment to settle out of influent stormwater before entering a large infiltration chamber housed under a parking lot/ The outlet control device can then drain into a [[dry pond]] furthu downstream or offsite (Source: Philadelphia Water Department. 2020)<ref>Philadelphia Water Department. 2020. Stormwater Management Guidance Manual: Version 3.2. Accessed from: https://www.pwdplanreview.org/upload/manual_pdfs/PWD-SMGM-v3.2-20201001.pdf</ref>]]

[[File:Sump inelt to chamber system.JPG|thumb|500px|Example of a [[Pretreatment#Concentrated underground flow|overland flow sump inlet]] allowing sediment to settle out of influent stormwater before entering a large infiltration chamber housed under a parking lot. The outlet control device can then drain into a [[dry pond]] further downstream or offsite (Source: Philadelphia Water Department. 2020)<ref>Philadelphia Water Department. 2020. Stormwater Management Guidance Manual: Version 3.2. Accessed from: https://www.pwdplanreview.org/upload/manual_pdfs/PWD-SMGM-v3.2-20201001.pdf</ref>]]

===2. Treatment trains designed to address one or more design criteria===  

===2. Treatment trains designed to address one or more design criteria===  

'''Example''': [[Pretreatment#Concentrated underground flow|Proprietary filtration treatment device]] (providing water quality) draining to an underground [[infiltration trench]] or [[Infiltration chambers|chamber system]] (providing water balance control).  Overflows from the trench or chamber system could drain to a [[dry pond]] or other flood control facility to provide water quantity and erosion control).  Another example may be to direct low flows from a stormwater management pond [[Overflow|outlet]] to an infiltration practice.   

'''Example''': [[Pretreatment#Concentrated underground flow|Proprietary filtration treatment device]] (providing water quality) draining to an underground [[infiltration trench]] or [[Infiltration chambers|chamber system]] (providing water balance control).  Overflows from the trench or chamber system could drain to a [[dry pond]] or other flood control facility to provide water quantity and erosion control).  Another example may be to direct low flows from a stormwater management pond [[Overflow|outlet]] to an infiltration practice.   

'''Performance calculation''':  Treatment trains designed to address multiple design criteria may improve overall water quality performance by, for example, reducing water quality concentrations in the first facility and reducing water quality loads (through infiltration/evapotranspiration) in a second facility.  Even if the effluent concentration from facility one and facility two are the same, the overall load reduction of the treatment train may be greater than provided by any one of the facilities alone.

'''Performance calculation''':  Treatment trains designed to address multiple design criteria may improve overall water quality performance by, for example, reducing water quality concentrations in the first facility and reducing water quality loads (through infiltration/evapotranspiration) in a second facility.  Even if the effluent concentration from facility one and facility two are the same, the overall load reduction of the treatment train may be greater than provided by any one of the facilities alone. <br>

===3. Treatment trains designed to enhance overall treatment system performance===

===3. Treatment trains designed to enhance overall treatment system performance===

[[File:Storm bmps rev3.png|thumb|400px|An example of a treatment train approach used to enhance treatment performance in an area with limited surface area due to parking and the adjacent municipal roadway. In this example water is able to be collected and then conveyed from a [[green roof]] system, a [[bioswale]] and [[permeable pavement]] parking lot, through an [[OGS|oil and grit separator]] and then to an [[Infiltration chamber]] or an underground [[Rainwater harvesting|cistern]] tank. Clean water can then be reused onsite or overflow out to the municipal storm sewer and receiving waterbody (City of Saskatoon, 2023).<ref>City of Saskatoon. 2023. Storm Water Management Credit Program. Image courtesy of the City of Mississauga. Accessed: https://www.saskatoon.ca/services-residents/power-water-sewer/storm-water/storm-water-management-credit-program</ref>]]

[[File:Storm bmps rev3.png|thumb|750px|An example of a treatment train approach used to enhance treatment performance in an area with limited surface area due to parking and the adjacent municipal roadway. In this example water is able to be collected and then conveyed from a [[green roof]] system, a [[bioswale]] and [[permeable pavement]] parking lot, through an [[Oil and Grit Separator|oil and grit separator]] and then to an [[Infiltration chamber]] or an underground [[Rainwater harvesting|cistern]] tank. Clean water can then be reused onsite or overflow out to the municipal storm sewer and receiving waterbody (City of Saskatoon, 2023).<ref>City of Saskatoon. 2023. Storm Water Management Credit Program. Image courtesy of the City of Mississauga. Accessed: https://www.saskatoon.ca/services-residents/power-water-sewer/storm-water/storm-water-management-credit-program</ref>]]

The design intent of these treatment trains is to enhance overall system performance.  The previous category of treatment train may enhance performance, but the objective may not always be to address a broader range of stormwater criteria.   

The design intent of these treatment trains is to enhance overall system performance.  The previous category of treatment train may enhance performance, but the objective may not always be to address a broader range of stormwater criteria.   

'''Example:'''  A bioretention and infiltration chamber in series.  Adding the second facility increases the overall area available for infiltration, which in turn reduces the overall load of pollutants to the receiver. This type of treatment may be advantageous where surface space is limited, but water balance requirements can not be met with available space allocated to the surface bioretention cell alone.   

'''Example:'''  A bioretention and infiltration chamber in series.  Adding the second facility increases the overall area available for infiltration, which in turn reduces the overall load of pollutants to the receiver. This type of treatment may be advantageous where surface space is limited, but water balance requirements can not be met with available space allocated to the surface bioretention cell alone.   

'''Performance calculation''':  In the example above, the [[bioretention]] facility would provide water quality load reductions through filtration (water quality concentration reductions) and infiltration (volume reductions).  Since the second facility would receive effluent from the [[underdrain]] of the bioretention, no further reduction in TSS concentrations would be expected (ie. the TSS concentration would already be at the ‘irreducible’ level) (Schueler, 2000)<ref>Schueler, T.  2000.  Irreducible Pollutant Concentration Discharged from Stormwater Practices.  Technical Note #75, In Watershed Protection Techniques. 2(2), 369-372, Centre for Watershed Protection. Accessed: https://owl.cwp.org/mdocs-posts/elc_pwp65/</ref>.  The TSS water quality load would be reduced in the second facility only by further reductions in volumes through infiltration.  If the parameter of interest was total [[phosphorus]] (TP) rather than TSS, there is the potential that the second facility may further reduce TP through filtration/adsorption, especially if the second facility contained [[Sorbtive media|reactive media]] designed to remove phosphorus.

'''Performance calculation''':  In the example above, the [[bioretention]] facility would provide water quality load reductions through filtration (water quality concentration reductions) and infiltration (volume reductions).  Since the second facility would receive effluent from the [[underdrain]] of the bioretention, no further reduction in TSS concentrations would be expected (ie. the TSS concentration would already be at the ‘irreducible’ level) (Schueler, 2000)<ref>Schueler, T.  2000.  Irreducible Pollutant Concentration Discharged from Stormwater Practices.  Technical Note #75, In Watershed Protection Techniques. 2(2), 369-372, Centre for Watershed Protection. Accessed: https://owl.cwp.org/mdocs-posts/elc_pwp65/</ref>.  The TSS water quality load would be reduced in the second facility only by further reductions in volumes through infiltration.  If the parameter of interest was total [[phosphorus]] (TP) rather than TSS, there is the potential that the second facility may further reduce TP through filtration/adsorption, especially if the second facility contained [[Sorbtive media|reactive media]] designed to remove phosphorus.<br>

===4. Treatment trains designed to optimize treatment facility sizing through flow control===

===4. Treatment trains designed to optimize treatment facility sizing through flow control===

'''Example''':  A filtration facility drained by a catchment with temporary upstream water storage through oversized storm sewer pipes, parking lot storage and/or orifice controlled roof drains.  In the case of oversized storm sewers or parking lot storage, the pipe feeding the filtration facility would normally have an orifice to control flow rates draining into the facility.   

'''Example''':  A filtration facility drained by a catchment with temporary upstream water storage through oversized storm sewer pipes, parking lot storage and/or orifice controlled roof drains.  In the case of oversized storm sewers or parking lot storage, the pipe feeding the filtration facility would normally have an orifice to control flow rates draining into the facility.   

'''Performance calculation''': The capacity of this type of treatment train to improve performance depends on sizing of the downstream practice.  If this practice (e.g. proprietary filtration MTD) is sized to the new controlled flow rate (and the design storm remains the same), then the performance of the facility may be the same or similar to what would have been achieved without upstream controls because there would be a similar number of overflows (i.e flows that bypass the treatment chamber).  If the downstream practice is a settling device, such as an OGS, then the performance of the downsized facility may be slightly lower than without flow controls because performance of these devices are more sensitive than filters to the rate of flow through the treatment chamber See performance curves (TSS removal efficiencies vs surface loading rates) [[Oil and Grit Separator#Performance Test Results|'''on our OGS page here''']].

'''Performance calculation''': The capacity of this type of treatment train to improve performance depends on sizing of the downstream practice.  If this practice (e.g. proprietary filtration MTD) is sized to the new controlled flow rate (and the design storm remains the same), then the performance of the facility may be the same or similar to what would have been achieved without upstream controls because there would be a similar number of overflows (i.e flows that bypass the treatment chamber).  If the downstream practice is a settling device, such as an OGS, then the performance of the downsized facility may be slightly lower than without flow controls because performance of these devices are more sensitive than filters to the rate of flow through the treatment chamber See performance curves (TSS removal efficiencies vs surface loading rates) [[Oil and Grit Separator#Performance Test Results|'''on our OGS page here''']]. <br>

Of course, the real world is not black and white, and it is possible to blend these categories to meet a variety of different site stormwater management objectives.  The purpose of categorizing the treatment train types into design priorities is to highlight the need to consider different objectives, while recognizing that if the design priority of the treatment train is narrowly focused, objectives other than those targeted may not be met.

Of course, the real world is not black and white, and it is possible to blend these categories to meet a variety of different site stormwater management objectives.  The purpose of categorizing the treatment train types into design priorities is to highlight the need to consider different objectives, while recognizing that if the design priority of the treatment train is narrowly focused, objectives other than those targeted may not be met.

==Calculating Performance of Treatment Trains==

==Calculating Water Quality Performance of Treatment Trains==

The performance of a treatment train will vary based on the type of stormwater treatment practices implemented and their arrangement within the treatment train.  Various changes occur as [[Runoff volume control targets|runoff]] moves through the treatment train.  Key changes that need to be considered when [[Low impact development treatment train tool|calculating treatment train performance]] including:

The performance of a treatment train will vary based on the type of stormwater treatment practices implemented and their arrangement within the treatment train.  Various changes occur as [[Runoff volume control targets|runoff]] moves through the treatment train.  Key changes that need to be considered when [[Low impact development treatment train tool|calculating treatment train performance]] including:

===1. Changes in the composition of runoff, especially the [[Grain size analysis|size distribution of sediment particles]]===

===1. Changes in the composition of runoff, especially the size distribution of sediment particles===

Stormwater facilities are often designated as providing enhanced (80% TSS removal) or basic treatment (50 to 60% TSS removal) based on their capacity to remove fine particles (MOE, 2003)<ref>Ministry of Environment. 2003. Stormwater Management Planning and Design Manual. March 2003. Copyright: Queen’s Printer for Ontario, 2003. ISBN 0-7794-2969-9. PIBS 4329e. Accessed: https://www.ontario.ca/document/stormwater-management-planning-and-design-manual-0.</ref>. These facilities change not only sediment loads of sediment but also the composition of sediment loads, which has important implications for calculating performance.

Stormwater facilities are often designated as providing enhanced (80% TSS removal) or basic treatment (50 to 60% TSS removal) based on their capacity to remove fine particles (MOE, 2003)<ref>Ministry of Environment. 2003. Stormwater Management Planning and Design Manual. March 2003. Copyright: Queen’s Printer for Ontario, 2003. ISBN 0-7794-2969-9. PIBS 4329e. Accessed: https://www.ontario.ca/document/stormwater-management-planning-and-design-manual-0.</ref>. These facilities change not only sediment loads of sediment but also the composition of sediment loads, which has important implications for calculating performance.

The water quality load is the product of runoff concentrations and runoff volumes.  Hence, a change in either of these variables will result in a change in load.  As concentrations and volumes are affected by different variables it is best to consider the components separately, and then combine them to calculate overall load based performance for the treatment train under consideration.

The water quality load is the product of runoff concentrations and runoff volumes.  Hence, a change in either of these variables will result in a change in load.  As concentrations and volumes are affected by different variables it is best to consider the components separately, and then combine them to calculate overall load based performance for the treatment train under consideration.

Thus, treatment performance of facilities designed to reduce runoff volumes would be calculated based on their capacity to reduce water quality loads, as seen below:

Treatment performance of facilities designed to reduce runoff volumes would be calculated based on their capacity to reduce water quality loads, as seen below:

===Equation 1:===

===Equation 1:===

===Equation 2:===

===Equation 2:===

<math>R_{L}=\frac{100(A - B}{A}</math>

<math>R_{L}=\frac{100(A - B)}{A}</math>

 

{{Plainlist|1=Where:

{{Plainlist|1=Where:

*''R'' = Removal Efficiency (%)

*''R'' = Removal Efficiency (%)

Since basic level facilities remove TSS particles that are effectively removed by enhanced level facilities, the removal efficiency of a treatment train consisting of two non-infiltrating facilities would be equal to the removal efficiency of the highest performing facility (i.e. 80% TSS removal), assuming that the facilities are sized appropriately.

Since basic level facilities remove TSS particles that are effectively removed by enhanced level facilities, the removal efficiency of a treatment train consisting of two non-infiltrating facilities would be equal to the removal efficiency of the highest performing facility (i.e. 80% TSS removal), assuming that the facilities are sized appropriately.

Examples of this type of treatment train would include: (i) [[Pretreatment features|catch basin inserts]] (aka water quality inlets) upstream of a filtration facility (e.g. lined [[bioretention]], [[Pretreatment|proprietary filtration system]], [[Media filters|sand filter]]); (ii) [[OGS]] upstream of a wet pond;  (iii) [[Infiltration chambers|temporary parking lot or pipe storage]] upstream of a filtration facility.  If an OGS is placed upstream of a [[dry pond]], the overall treatment performance would be equal to that of the dry pond since the finer particle size fraction of TSS is not captured.  As mentioned above, the major benefit of these types of treatment trains is to reduce long term maintenance cost and effort by centralizing sediment in the upstream practice where it is easier to clean out.

Examples of this type of treatment train would include: (i) [[Pretreatment features|catch basin inserts]] (aka water quality inlets) upstream of a filtration facility (e.g. lined [[bioretention]], [[Pretreatment|proprietary filtration system]], [[Media filters|sand filter]]); (ii) [[Ogs|OGS]] upstream of a wet pond;  (iii) [[Infiltration chambers|temporary parking lot or pipe storage]] upstream of a filtration facility.  If an OGS is placed upstream of a [[dry pond]], the overall treatment performance would be equal to that of the dry pond since the finer particle size fraction of TSS is not captured.  As mentioned above, the major benefit of these types of treatment trains is to reduce long term maintenance cost and effort by centralizing sediment in the upstream practice where it is easier to clean out.

In some cases, it may be advantageous to include two level one facilities in a treatment train.  An example may be a lined [[bioretention]] with pre-treatment upstream of a [[Pretreatment#Concentrated underground flow|filter with media designed to enhance phosphorous uptake]].  The overall [[Phosphorus#Limiting excess phosphorus|phosphorus removal rate]] for the treatment train would be equivalent to that of the downstream filter, assuming that it is sized appropriately for the site in question.  The bioretention facility in this instance would help to control flow rates to the downstream facility while also filtering out sediments that would otherwise cause pre-mature [[clogging]] of the downstream [[filter media]].

In some cases, it may be advantageous to include two level one facilities in a treatment train.  An example may be a lined [[bioretention]] with pre-treatment upstream of a [[Pretreatment#Concentrated underground flow|filter with media designed to enhance phosphorous uptake]].  The overall [[Phosphorus#Limiting excess phosphorus|phosphorus removal rate]] for the treatment train would be equivalent to that of the downstream filter, assuming that it is sized appropriately for the site in question.  The bioretention facility in this instance would help to control flow rates to the downstream facility while also filtering out sediments that would otherwise cause pre-mature [[clogging]] of the downstream [[filter media]].

==Treatment trains with runoff volume reduction facilities==

==Treatment trains with runoff volume reduction facilities==

[[File:72208733 sustainable drainage 624.jpg|thumb|650px|A treatment train example of source controls in a housing development neighbourhood with [[vegetated filter strips]], [[swales]] and [[permeable pavement]] driveways and roadways achieving water balance requirements during a 90th percentile event and then overflows can be conveyed to a [[dry pond]] / [[wet pond]] and then into receiving [[constructed wetlands]] and water courses (Susdrain/CIRIA, 2014)<ref>Susdrain/CIRIA. 2014. Sustainable Urban Drainage Systems (SUDS) in Flood Prevention. DuratexUK Rubber & Plastics Ltd. Accessed: https://www.duratex.co.uk/company-blog/industry-news/sustainable-urban-drainage-systems-suds-in-flood-prevention</ref>]]

[[File:72208733 sustainable drainage 624.jpg|thumb|650px|A treatment train example of source controls in a housing development neighbourhood with [[vegetated filter strips]], [[swales]] and [[permeable pavement]] driveways. These practices provide water balance control for the 90th percentile event and roadways achieving water balance requirements during a 90th percentile event.  Flows from larger rain events are conveyed to a [[dry pond]] / [[wet pond]] and then into [[constructed wetlands]] and water courses (Susdrain/CIRIA, 2014)<ref>Susdrain/CIRIA. 2014. Sustainable Urban Drainage Systems (SUDS) in Flood Prevention. DuratexUK Rubber & Plastics Ltd. Accessed: https://www.duratex.co.uk/company-blog/industry-news/sustainable-urban-drainage-systems-suds-in-flood-prevention</ref>.]]

These types of treatment trains are becoming more common because they can achieve multiple [[Runoff volume control targets|stormwater control]] and [[water quality|treatment objectives]].  Since wet ponds alone do not achieve stormwater water balance criteria, they must be supplemented with facilities providing runoff volume reductions to meet regulatory requirements. If site water balance objectives require control of the 90th percentile event (roughly 25 – 30 mm in most jurisdictions), the same infiltration facilities may also be used to treat the water quality storm (typically 25 mm), allowing for a [[dry pond]] or similar temporary detention facility to be used at the end-of-pipe to meet flood and erosion control criteria.

These types of treatment trains are becoming more common because they can achieve multiple [[Runoff volume control targets|stormwater control]] and [[water quality|treatment objectives]].  Since wet ponds alone do not achieve stormwater water balance criteria, they must be supplemented with facilities providing runoff volume reductions to meet regulatory requirements. If site water balance objectives require control of the 90th percentile event (roughly 25 – 30 mm in most jurisdictions), the same infiltration facilities may also be used to treat the water quality storm (typically 25 mm), allowing for a [[dry pond]] or similar temporary detention facility to be used at the end-of-pipe to meet flood and erosion control criteria.