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Line 139: − {| class="wikitable" style="float:right; margin-left:15px;" − |+ style="text-align:center;" | Recommended storage volumes per ha by catchment imperviousness for continuous flow dry ponds with basic protection (MOE, 2003)<ref name="MOE"></ref> − ! Imperviousness of Catchment − ! Storage Volume (m³/ha) − ! Permanent pool (extended detention) (m³/ha) − |- − | 35% − | 90 − | 50 − |- − | 55% − | 150 − | 81 − |- − | 70% − | 200 − | 89 − |- − | 85% − | 240 − | 107 − |} − Line 310:
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no edit summary
===Volume===
===Volume===
The surface storage volume of a dry pond (''A<sub>p</sub>'') is determined:
The surface storage volume of a dry pond (''A<sub>p</sub>'') is determined:
<math>A_{p}=\frac{RVC_T\times A_{c}}{f'\times t}</math>
<math>A_{p}=\frac{RVC_T\times A_{c}}{f'\times t}</math>
==Performance==
==Performance==
Dry ponds may include a deep pool in the sediment forebay to minimize scour and sediment resuspension, but the main basin does not retain a permanent pool of water. As a result, contaminants cannot settle between storm events, nor is there dilution of pollutants during storms. Consequently, while dry ponds are effective for erosion and flood control, they may need to be paired with other LID features in a [[Treatment train|treatment train]] to improve water quality beyond the basic treatment level of 60% long-term TSS removal.
{| class="wikitable" style="float:right; margin-left:15px;"
|+ style="text-align:center;" | Recommended storage volumes per ha by catchment imperviousness for continuous flow dry ponds with basic protection (MOE, 2003)<ref name="MOE"></ref>
! Imperviousness of Catchment
! Storage Volume (m³/ha)
! Permanent pool (extended detention) (m³/ha)
|-
| 35%
| 90
| 50
|-
| 55%
| 150
| 81
|-
| 70%
| 200
| 89
|-
| 85%
| 240
| 107
|}
Stormwater ponds and constructed wetlands are designed to meet water quality targets based on drainage area imperviousness. Pollutant removal occurs mainly in the permanent pool, with effectiveness depending on hydraulic residence time—longer times improve sedimentation and biological uptake. In Ontario, most facilities must achieve 80% TSS removal, with storage requirements based on a 24-hour drawdown time (MOE, 2003).
Dry ponds may include a deep pool in the sediment forebay to minimize scour and sediment resuspension, but the main basin does not retain a permanent pool of water. As a result, contaminants cannot settle between storm events, nor is there dilution of pollutants during storms. Consequently, while dry ponds are effective for [[Erosion|erosion]] and flood control, they may need to be paired with other LID features in a [[Treatment train|treatment train]] to improve water quality beyond the basic treatment level of 60% long-term TSS removal.
==Modeling==
==Modeling==