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Line 140: − {| 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) − |- − | 35% − | 90 − |- − | 55% − | 150 − |- − | 70% − | 200 − |- − | 85% − | 240 − |} − Line 157:
Line 147: − − Higher catchment imperviousness may require a larger storage volume, as shown in the chart on the right. Line 269:
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Line 371: + − Inspection points for dry ponds include (MOE, 2003)<ref name="MOE"></ref>:+ − + − + − + − *visible sediment accumulation in the bottom of the pond or around the high water line of the pond - may indicate need for sediment removal − − − A field data sheet for the inspection of constructed wetlands is available below. You can download (downward facing arrow on the top righthand side) and print (Printer emoticon on top right hand side) the Dry Pond or Dry Extended Detention Basin Inspection and Maintenance Checklist developed by the City of Ontario, Ohio<ref>City of Ontario, Ohio. https://ontarioohio.org/stormwater-management/</ref>. − <pdf width="450" height="600">File:Post-Construction-OM-Dry-Basin-Inspection-Sheet.pdf</pdf><br clear="all" />+ +
→STEP Training
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[[File:Dryponds map.PNG|thumb|link=https://goo.gl/68Ewnz|Click here to see map of Dry Ponds in Scarborough and surroundings]]
[[File:Screenshot 2025-08-29 092912.png|400px|thumb|right|link=https://open.hamilton.ca/datasets/SpatialSolutions::stormwater-management-facilities/explore?filters=eyJGQUNJTElUWV9UWVBFIjpbIkRyeSBQb25kIl19&location=43.231533%2C-79.840637%2C11.00&style=FACILITY_TYPE|Click on the image to open a map of dry ponds in Hamilton.]]
See also [[Water squares]]
See also [[Water squares]]
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{{TOClimit|2}}
==Overview==
==Overview==
*distributing across a larger development site.}}
*distributing across a larger development site.}}
[[LID Case Studies#Dry Ponds|Click here to read a case study on dry ponds at the The University of Toronto Scarborough campus.]]
[[File:Screenshot 2025-08-25 144851.png|400px|thumb|right|link=https://sourcetostream.com/2024-track-1-day-1-denich-eves/|Click on the image to read about an infiltration facility with OGS pre-treatment located beneath an existing dry-pond in the Lake Simcoe Watershed (Denich & Eves, 2024)<ref>Dennich, C. & Eves, C. 2024. KDO3 Dry Pond Sub-surface Infiltration Facility Design, Construction & Monitoring. Source to Stream Conference Presentation. https://sourcetostream.com/2024-track-1-day-1-denich-eves/</ref>.]]
Click the button below to read about a case study of a dry pond on the UTSC campus.
{{Clickable button|[[File:UTSC bioretention.PNG|130 px|link=https://sustainabletechnologies.ca/app/uploads/2015/07/U-of-T-Scarborough.pdf]]}}
===STEP Training===
Click the button on the left to register for training on SWM pond inspection and maintenance and the button on the right to learn about wet ponds:
[[File:Screenshot 2025-08-25 144851.png|400px|thumb|left|link=https://sourcetostream.com/2024-track-1-day-1-denich-eves/|Click on the image to read about an infiltration facility with OGS pre-treatment located beneath an existing dry-pond in the Lake Simcoe Watershed (Denich & Eves, 2024)<ref>Dennich, C. & Eves, C. 2024. KDO3 Dry Pond Sub-surface Infiltration Facility Design, Construction & Monitoring. Source to Stream Conference Presentation. https://sourcetostream.com/2024-track-1-day-1-denich-eves/</ref>.]]<br clear="all" />
{{Clickable button|[[File:Screenshot 2025-08-29 101010.png|150px|link=https://sustainabletechnologies.ca/lid-swm-inspection-maintenance-training/]]}} {{Clickable button|[[File:Screenshot 2025-08-29 101218.png|150 px|link=https://wiki.sustainabletechnologies.ca/wiki/SWM_ponds]]}}
==Planning considerations==
==Planning considerations==
*no steeper than 1:3 to permit vegetation stabilization and maintenance/amenity access (except where pond <0.5 m deep)
*no steeper than 1:3 to permit vegetation stabilization and maintenance/amenity access (except where pond <0.5 m deep)
*stepped or benched slopes possible depending on maintenance access (Ballard et al., 2015)<ref name=Ballard/>
*stepped or benched slopes possible depending on maintenance access (Ballard et al., 2015)<ref name=Ballard/>
*recommended that the grading of the pond side slopes be terraced with an average slope of 4:1 or flatter.
|-
|-
|[[Dry ponds#Inlet|Inlet]]
|[[Dry ponds#Inlet|Inlet]]
===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>
*''f''' = design infiltration rate (mm/hr)
*''f''' = design infiltration rate (mm/hr)
*''t'' = [[drainage time|time permitted for ponding to infiltrate]] (hrs) (typically 48 hours)}}
*''t'' = [[drainage time|time permitted for ponding to infiltrate]] (hrs) (typically 48 hours)}}
===Detention time===
===Detention time===
===Inlet===
===Inlet===
[[File:Screenshot 2025-08-20 115733.png|400px|thumb|Dry pond inlet (MOE, 2003)<ref name="MOE"></ref>]]
[[File:Screenshot 2025-08-20 115733.png|400px|thumb|Dry pond inlet (MOE, 2003)<ref name="MOE"></ref>]]
The number of [[Inlet|inlets]] into the pond should be minimized. To reduce [[Erosion|erosion]] risk, the use of environmental stone or interlocking blocks with large openings that support vegetative growth is recommended at the inlet. A flow deflector or energy dissipation blocks may also be installed to limit scour and prevent the resuspension of previously settled pollutants from the pond bottom (MOE, 2003)<ref name="MOE"></ref>.
The number of [[Inlet|inlets]] into the pond should be minimized. The invert of the inlet pipe is set at the maximum design water level in the pond. To reduce [[Erosion|erosion]] risk, the use of environmental stone or interlocking blocks with large openings that support vegetative growth is recommended at the inlet. A flow deflector or energy dissipation blocks may also be installed to limit scour and prevent the resuspension of previously settled pollutants from the pond bottom (MOE, 2003)<ref name="MOE"></ref>.
===Outlet===
===Outlet===
[[File:Screenshot 2025-08-20 115140.png|400px|thumb|Dry pond outlet (MOE, 2003)<ref name="MOE"></ref>]]
[[File:Screenshot 2025-08-20 115140.png|400px|thumb|Dry pond outlet (MOE, 2003)<ref name="MOE"></ref>.]]
The performance of a dry pond can be enhanced via a shallow micropool at the outlet which concentrates finer sediment and reduces re-suspension. The micropool is normally planted with hardy wetland species such as [[Wetlands: Plants|cattail]] (MOE, 2003)<ref name="MOE"></ref>.
The outlet should be located in the pond embankment wherever possible for ease of maintenance and aesthetics. The performance of a dry pond can be enhanced via a shallow micropool at the outlet which concentrates finer sediment and reduces re-suspension. The micropool is normally planted with hardy wetland species such as [[Wetlands: Plants|cattail]] (MOE, 2003)<ref name="MOE"></ref>. A reverse sloped pipe makes the outlet more resilient to clogging (MOE, 2003)<ref name="MOE"></ref>.
*a naturalized landscape approach should be used which strives for a [[Plant lists|vegetation]] community with long-term sustainability and no maintenance requirements (MOE, 2003)<ref name="MOE"></ref>.
*a naturalized landscape approach should be used which strives for a [[Plant lists|vegetation]] community with long-term sustainability and no maintenance requirements (MOE, 2003)<ref name="MOE"></ref>.
See [[Turf|Salt-Tolerant Turf Grasses]], [[Shrubs: List]], and [[Trees: List]] for a list of native species which could be planted in the buffer strip.<br clear="all" />
See [[Turf|Salt-Tolerant Turf Grasses]], [[Shrubs: List]], and [[Trees: List]] for a list of native species which could be planted in the buffer strip.
===Planting Strategy===
Depending upon the proposed planting strategy, these maximum storage depths may be reduced to 1 to 1.5 metres. It is anticipated, however, that the dry pond will not be actively planted in the extended detention portion due to harsh growing conditions (frequent wetting/drying). The planting approach for a dry pond is typically less intensive than for a wet pond, involving fewer species and lower planting density. Vegetation is generally organized into three zones according to soil moisture conditions:
*Extended detention area
*Flood fringe area (for combined quality/quantity SWMPs)
*Upland area
Growing conditions in the extended detention area of a dry pond are more challenging than in a wet pond because there is no permanent pool to moderate moisture levels. As a result, this zone requires particular attention to ensure that desired plant species establish successfully (MOE, 2003)<ref name="MOE"></ref>.
==Performance==
{| 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)<ref name="MOE"></ref>.
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 (MOE, 2003)<ref name="MOE"></ref>.
==Modeling==
==Modeling==
==Inspection and Maintenance==
==Inspection and Maintenance==
[[File:Dry pond maintenance.jpg|400px|thumb|right|Dry pond maintenance in Alberta (City of Airdrie, 2024)<ref>City of Airdrie. 2024. Airdrie dry pond maintenance extended till next month. https://discoverairdrie.com/articles/airdrie-dry-pondmaintenance-extended-till-next-month</ref>.]]
[[File:Dry pond maintenance.jpg|400px|thumb|right|Dry pond maintenance in Alberta (City of Airdrie, 2024)<ref>City of Airdrie. 2024. Airdrie dry pond maintenance extended till next month. https://discoverairdrie.com/articles/airdrie-dry-pondmaintenance-extended-till-next-month</ref>.]]
Inspection points for dry ponds include (MOE, 2003)<ref name="MOE"></ref>:
*standing water in pond after rain events for longer than designed detention time - may indicate outlet blockage
*pond is always/relatively dry, even throughout designed detention time - may indicate inlet blockage
*vegetation around the pond unhealthy or dying - may indicate poor species selection
*visible sediment accumulation in the bottom of the pond or around the high water line of the pond - may indicate need for sediment removal
A field data sheet for the inspection of constructed wetlands is available below. You can download (downward facing arrow on the top righthand side) and print (Printer emoticon on top right hand side) the the [https://sustainabletechnologies.ca/app/uploads/2018/04/SWMFG2016_Guide_April-2018.pdf Pond/Wetland Maintenance and Inspection Form] developed by Toronto and Region Conservation Authority (TRCA) and CH2M Hill Canada.
<pdf width="450" height="600">File:SWMFG2016 Guide April-2018.pdf</pdf>
Maintenance requirements vary between dry ponds and wet ponds, although many maintenance tasks overlap.
Maintenance requirements vary between dry ponds and wet ponds, although many maintenance tasks overlap.
|}
|}
===Forecasting Sediment Accumulation and Cleanouts===
{| class="wikitable" style="float:right; margin-left:15px;
{| class="wikitable" style="float:right; margin-left:15px;
|+ Maximum allowable sediment accumulation (m³/ha) in dry ponds by catchment imperviousness for basic protection (STEP, 2016)<ref>STEP. 2016. Inspection and maintenance guide for stormwater management ponds and constructed wetlands. https://sustainabletechnologies.ca/app/uploads/2018/04/SWMFG2016_Guide_April-2018.pdf</ref>
|+ Maximum allowable sediment accumulation (m³/ha) in dry ponds by catchment imperviousness for basic protection (STEP, 2016)<ref>STEP. 2016. Inspection and maintenance guide for stormwater management ponds and constructed wetlands. https://sustainabletechnologies.ca/app/uploads/2018/04/SWMFG2016_Guide_April-2018.pdf</ref>
|}
|}
Accurate forecasting of sediment accumulation in stormwater facilities helps managers schedule and budget for maintenance. MOE (2003) recommends SWMFs be cleaned when the TSS removal efficiency declines below 5% of its original design criterion<ref name="MOE"></ref>. For example, if a dry pond is designed to remove 60% of TSS, an efficiency reduction to 55% triggers the need for sediment removal. The rate of sediment accumulation differs for each facility, and depends on factors such as the characteristics of drainage area (e.g., land use; level of imperviousness; upstream construction activities and effectiveness of sediment and erosion control practices) and municipal practices (e.g. frequency of road/catchbasin cleaning, sanding/salting practices).
To assess whether a SWMF needs sediment removal, three factors are required:
*standing water in pond after rain events for longer than designed detention time - may indicate outlet blockage
*Current storage capacity (from sediment depth measurements or TSS load modelling).
*pond is always/relatively dry, even throughout designed detention time - may indicate inlet blockage
*Minimum efficiency allowed (5% reduction, per MOE 2003).
*vegetation around the pond unhealthy or dying - may indicate poor species selection
*The facility’s efficiency–storage relationship, to compare storage loss with the 5% efficiency threshold.
STEP's [https://sustainabletechnologies.ca/app/uploads/2018/04/SWMFG2016_Guide_April-2018.pdf Inspection and Maintenance Guide for Stormwater Management Ponds and Constructed Wetlands] (section 4.5.1: Forecasting Based on Sediment Depth Measurements) describe methods for forecasting the need for sediment removal and provides a sample forecasting exercise.
<br clear="all" />
==Gallery==
==Gallery==