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Line 1: − <p>Infiltration of stormwater into underlying soils is one the priority level 1. mechanisms to achieve MOECC Runoff Volume Control targets. In many areas of Ontario, where municipal supplies of potable water are drawn from aquifers, it's also an important mechanism to recharge groundwater supplies.</p>+ − + + − + − + − + + + + + − ===Constraints===+ + − + − + − + + + + + − + − + − + + + + + + + + − + − ===Designing within constraints=== − {{TextBox|1= Infiltration can still be optimized over 'tight' soils with infiltration rates ≤ 15 mm/hr: − *[[Bioretention: Internal water storage |Bioretention with internal water storage]]8 − *[[Bioretention:_Partial_infiltration|Partially infiltrating bioretention]] + − {{TextBox|1= Where infiltration is impossible, LID design alternatives exist which can still capture and retain stormwater: − *[[Bioretention: Non-infiltrating | Bioretention planters]] − *[[Rainwater harvesting]] − *[[Green roofs]] − }} − ===Planning=== − <h4>Soil infiltration rate</h4> − [[Infiltration: Testing|Infiltration tests]] must be undertaken at the location, depth and with a head of water that replicates the proposed design. − <table class="table-responsive table table-striped"> − <caption><strong>Suggested safety factors to be applied to measured percolation rate when designing infiltration facilities</strong></caption> − <tr class="success"> − <th rowspan="2" class="text-center">Catchment area</th> − <th colspan="3" class="text-center">Consequence of failure</th> − <tr class="success"> − <th class="text-center">No damage or inconvenience</th> − <th class="text-center">Minor damage or inconvenience to external structures (e.g. ponding in parking lot)</th> − <th class="text-center">Significant damage to buildings or infrastructure (e.g. flooding damage)</th> − </tr> − <tr> − <td class="text-center"><100 m<sup>2</sup></td> − <td class="text-center">1.5</td> − <td class="text-center">2</td> − <td class="text-center">10</td> − </tr> − <tr> − <td style="white-space: nowrap" class="text-center"> 100 - 1000 m<sup>2</sup> − <td class="text-center">1.5</td> − <td class="text-center">3</td> − <td class="text-center">10</td> − </tr> − </table> − <h4>Groundwater</h4> − <p>The bottom of the infiltration BMP must ≥ 1 m vertically separated from the seasonally high water table, and underlying bedrock. This reduces the risk of contaminating groundwater and helps to ensure reliable infiltration rates throughout the year. </p> − − {{:Feedback}}
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{{TextBox|1= Infiltration is promoted through a number of LID BMPs:
Infiltration of stormwater into underlying native subgrade soils is one mechanism to achieving MECP [[runoff volume control targets]]. In many areas of Ontario, where municipal and private drinking water supplies are drawn from aquifers, it's also an important mechanism for groundwater recharge.
{{textbox|Drainage via infiltration be achieved through a number of LID BMP types:
*[[Infiltration chambers]] (underground)
*[[Infiltration chambers]] (underground)
*[[Infiltration trenches]] (underground)
*[[Infiltration trenches]] (underground)
*[[Dry ponds]] (surface)
*[[Exfiltration trenches| Exfiltration systems]] (underground)
*[[Bioretention cells]] (surface)
*[[Bioretention]] (surface, full- or partial-infiltration design variations)
*[[Bioswales]] (surface)
*[[Bioswales]] (surface, full- or partial-infiltration design variations)
*[[Permeable pavements| Permeable pavements]] (surface, full- or partial-infiltration design variations)
*[[Stormwater Tree Trenches|Stormwater tree trenches]] (surface, partial-infiltration design variation)
*[[Enhanced swales]] or [[Swales |swales]] featuring check dams (surface)
*[[Dry ponds]] or infiltration basins (surface)
}}
}}
==Constraints==
Infiltration practices are not recommended:
Infiltration practices are not recommended:
#over swelling clays or unstable sub-soils,
#over-swelling clays or unstable subsoils,
#over contaminated soils or sites with high risk of contamination from onsite activities,
#contaminated soils or sites with high risk of contamination from on-site activities (i.e. pollution hot spots),
#in flood prone areas where the wastewater system is sensitive to groundwater conditions causing sewer backups, and where LID BMPs have been found to be ineffective,
#in areas of known or implied [[Karst |karst topography]],
#on unstable or steep slopes (>15%),
# to treat construction site runoff,
#to treat combined sewer overflows,
#in flood prone areas where the wastewater system is sensitive to groundwater conditions causing sewer backups,
#in areas where the ecology and natural hydrology are dependent upon surface water,
#in areas where the ecology and natural hydrology are dependent upon surface water,
#in areas where increased infiltration will result in elevated groundwater levels, which can be demonstrated to damage critical utilities or private property, or
#in areas where increased infiltration will result in elevated groundwater levels that will damage critical utilities or private property, or
#where prohibitions and/or restrictions exist per approved Source Protection Plans (see MOECC guidance).
#where prohibitions and/or restrictions exist per approved source water protection plans (e.g. should not be used to treat pavement runoff within wellhead protection area B, 2 year time of travel zones, nor within groundwater quality issue contributing areas where Sodium or Chloride is a threat).
Infiltration facilities should be designed with drainage modifications where:
<br>
See [[Site considerations]] for further guidance on potential site constraints and LID facility type selection and design considerations.
===Designing with constraints===
{{textbox|Infiltration facilities can be effective on low permeability soils with infiltration rates ≤ 15 mm/hr:
*See [[Underdrains| underdrains]] and
*Results from STEP studies of infiltration facilities located on [[low permeability soils]] in Ontario.
Infiltration facilities should be designed with modifications where:
#the underlying bedrock is within 1 m below the bottom of the proposed BMP, or
#the underlying bedrock is within 1 m below the bottom of the proposed BMP, or
#the seasonal high groundwater level comes within 1 m below the bottom of the proposed BMP.
#the seasonal high groundwater level (i.e. water table) comes within 1 m below the bottom of the proposed BMP.
}}
}}
{{:Groundwater}}
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[[category:Infiltration]]
[[category:Infiltration]]