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−__NOTOC__+<p>Infiltration of stormwater into underlying soils is one the priority level 1. mechanisms to achieve MOECC Runoff Volume Control targets.</p>+<ul>+<li>[[Infiltration chambers]] (underground)</li>+<li>[[Infiltration trenches]] (underground)</li>+<li>[[Dry ponds]] (surface)</li>+<li>[[Bioretention cells]] (surface)</li>+<li>[[Bioswales]] (surface)</li>+</ul>}}+===Constraints===+
+<ol>+<li>Where the bedrock is within 1 m below the bottom of the proposed BMP,</li>+<li>Where the seasonal high groundwater level comes within 1 m below the bottom of the proposed BMP,<br>Or in areas where increased infiltration will result in elevated groundwater levels, which can be demonstrated to damage critical utilities or private property,</li>+<li>Over swelling clays or unstable sub-soils,</li>+<li>Over contaminated soils or sites with high risk of contamination from onsite activities, </li>+<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>+<li>In areas where the ecology and natural hydrology are dependent upon surface water,</li>+<li>Where prohibitions and/or restrictions exist per approved Source Protection Plans (see MOECC guidance). +<p>+<ul>+
−<li>[[Bioretention: Internal water storage |Bioretention with internal water storage]]</li>+<li>[[Bioretention:_Partial_infiltration|Partially infiltrating bioretention]]</li>+</ul>}}+{{TextBox|1= Where infiltration is impossible, LID design alternatives exist which can still capture and retain stormwater:
−<ul>
−<li>[[Bioretention: Non-infiltrating | Bioretention planters]]</li>
−<li>[[Rainwater harvesting]]</li>
−<li>[[Green roofs]]</li>
−</ul>}}
−===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}}
{{TOClimit|2}}
−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:
+{{textbox|Drainage via infiltration be achieved through a number of LID BMP types:
−*[[Infiltration chambers]] (underground)
−*[[Infiltration trenches]] (underground)
−*[[Exfiltration trenches| Exfiltration systems]] (underground)
−*[[Bioretention]] (surface, full- or partial-infiltration design variations)
−*[[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 subsoils,
−#contaminated soils or sites with high risk of contamination from on-site activities (i.e. pollution hot spots),
−#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,
−</ol>
+#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 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).
−===Designing within constraints===
+<br>
−{{TextBox|1= Infiltration can still be optimized over 'tight' soils with infiltration rates ≤ 15 mm/hr:
+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 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]]