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<p>Infiltration of stormwater into underlying soils is one the priority level 1. mechanisms to achieve MOECC Runoff Volume Control targets.
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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|1= Infiltration is promoted through a number of LID BMPs:
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{{textbox|Drainage via infiltration be achieved through a number of LID BMP types:
*[[Infiltration chambers and trenches]] (underground)
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*[[Infiltration chambers]] (underground)
*[[Infiltration basins]] (surface)
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*[[Infiltration trenches]] (underground)
*[[Bioretention cells]] (surface)
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*[[Exfiltration trenches| Exfiltration systems]] (underground)
*[[Bioswales]] (surface)
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*[[Bioretention]] (surface, full- or partial-infiltration design variations)
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*[[Bioswales]] (surface, full- or partial-infiltration design variations)
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*[[Permeable pavements| Permeable pavements]] (surface, full- or partial-infiltration design variations)
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*[[Stormwater Tree Trenches|Stormwater tree trenches]] (surface, partial-infiltration design variation)
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*[[Enhanced swales]] or [[Swales |swales]] featuring check dams (surface)
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*[[Dry ponds]] or infiltration basins (surface)
 
}}
 
}}
</p>
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===Constraints===
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==Constraints==
 
Infiltration practices are not recommended:
 
Infiltration practices are not recommended:
<ol>
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#over-swelling clays or unstable subsoils,
<li>Where the bedrock is within 1 m below the bottom of the proposed BMP.</li>
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#contaminated soils or sites with high risk of contamination from on-site activities (i.e. pollution hot spots),
<li>Where the seasonal high groundwater level comes within 1 m below the bottom of the proposed BMP. Or in areas where increased infiltration will result in elevated groundwater levels, which can be demonstrated to damage critical utilities or private property. </li>
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#in areas of known or implied [[Karst |karst topography]],
<li>Over swelling clays or unstable sub-soils</li>
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#on unstable or steep slopes (>15%),
<li>Over contaminated soils or sites with high risk of contamination from onsite activities </li>
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# to treat construction site runoff,
<li>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. </li>
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#to treat combined sewer overflows, 
<li>In areas where the ecology and natural hydrology are dependent upon surface water. </li>
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#in flood prone areas where the wastewater system is sensitive to groundwater conditions causing sewer backups,
<li>Where prohibitions and/or restrictions exist per approved Source Protection Plans (see MOECC guidance).  
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#in areas where the ecology and natural hydrology are dependent upon surface water,
</ol>
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#in areas where increased infiltration will result in elevated groundwater levels that will damage critical utilities or private property, or
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#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).
 
<br>
 
<br>
<p>Without infiltration, many LID design alternatives exist which can still capture and retain  stormwater:
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See [[Site considerations]] for further guidance on potential site constraints and LID facility type selection and design considerations.
<ul>
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<li>[[Partially infiltrating bioretention]]</li>
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<li>[[Bioretention planters]]</li>
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<li>[[Rainwater harvesting]]</li>
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<li>[[Green roofs]]</li>
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</ul></p>
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===Planning===
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===Designing with constraints===
<h4>Soil Infiltration Testing </h4>
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{{textbox|Infiltration facilities can be effective on low permeability soils with infiltration rates ≤ 15 mm/hr:
<p>Infiltration tests must be undertaken at the location, depth and with a head of water that replicates the proposed design. </p>
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*See [[Underdrains| underdrains]] and  
<h4>Groundwater</h4>
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*Results from STEP studies of infiltration facilities located on [[low permeability soils]] in Ontario.
<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>
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Infiltration facilities should be designed with modifications where:
 
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#the underlying bedrock is within 1 m below the bottom of the proposed BMP, or
<clearFix></clearFix>
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#the seasonal high groundwater level (i.e. water table) comes within 1 m below the bottom of the proposed BMP.
<div class="column clearfix">
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}}
<table class="table table-bordered table-hover" >
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{{:Groundwater}}
<caption><strong>Suggested safety factors to be applied when designing infiltration facilities</strong></caption>
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----
<tr class="success">
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[[category:Infiltration]]
<th rowspan="2">Catchment area</th><th colspan="3">Consequence of failure</th>
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<tr class="success">
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<th>No damage or inconvenience</th><th>Minor damage or inconvenience to external structures (e.g. ponding in parking lot)</th><th>Significant damage to buildings or infrastructure (e.g. flooding damage)</th>
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<tr><td> <100 m<sup>2</sup></td><td>1.5</td><td>2</td><td>10</td></tr>
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<tr><td style="white-space: nowrap"> 100 - 1000 m<sup>2</sup><td>1.5</td><td>3</td><td>10</td></tr>
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</table>
 

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