1,647
edits
Changes
Jump to navigation
Jump to search
Line 37:
Line 37: − Learn about wet ponds here:+ − {{Clickable button|[[File:Screenshot 2025-08-29 101218.png|thumb|130 px|link=https://wiki.sustainabletechnologies.ca/wiki/SWM_ponds]]}} − Click the button below to register for training on SWM pond inspection and maintenance:+ − Line 142:
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 167:
Line 147: − − Higher catchment imperviousness may require a larger storage volume, as shown in the chart on the right. Line 308:
Line 286: + + + + + + + + + + + + + + + + + + + + + + + + + Line 317:
Line 320: + + + + + + + + + + + + Line 342:
Line 357: + Line 355:
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
===STEP Training===
===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:
{{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]]}}
{{Clickable button|[[File:Screenshot 2025-08-29 101010.png|thumb|130 px|link=https://sustainabletechnologies.ca/lid-swm-inspection-maintenance-training/]]}}
==Planning considerations==
==Planning considerations==
===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===
==Performance==
==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==