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→Treatment trains with runoff volume reduction facilities
==Treatment trains with runoff volume reduction facilities==
==Treatment trains with runoff volume reduction facilities==
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.
[[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>]]
In the example of LID practices upstream of a wet pond, the overall treatment train would meet the 80% TSS reduction target, since both facilities achieve enhanced level water quality targets. The wet pond may be downsized to account for the upstream reduction in runoff volumes, but the overall volume of water treatment to the enhanced level target (80% TSS removal) would be equal to the volume treated by the LID plus that treated by the wet pond, which together would exceed the 90th percentile water quality requirement.
In the example of LID practices upstream of a wet pond, the overall treatment train would meet the 80% TSS reduction target, since both facilities achieve enhanced level water quality targets. The wet pond may be downsized to account for the upstream reduction in runoff volumes, but the overall volume of water treatment to the enhanced level target (80% TSS removal) would be equal to the volume treated by the LID plus that treated by the wet pond, which together would exceed the 90th percentile water quality requirement.