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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. + − + − + − + − + − + + + + + + − </p>+ − ===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). + − </ol>+ − <br><p>+ − Infiltration can still be optimized over 'tight' soils with infiltration rates ≤ 15 mm/hr: − <li>[[Bioretention:_Partial_infiltration|Partially infiltrating bioretention]]</li></p> − <p>Without infiltration, many LID design alternatives exist which can still capture and retain stormwater:+ − <ul> − <li>[[Bioretention planters]]</li> − <li>[[Rainwater harvesting]]</li> − <li>[[Green roofs]]</li> − </ul></p> − + − <h4>Soil Infiltration Testing </h4>+ − <p>Infiltration tests must be undertaken at the location, depth and with a head of water that replicates the proposed design. </p>+ − <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>+ − + − <clearFix></clearFix>+ − <div class="column clearfix">+ − <table class="table table-bordered table-hover" >+ − <caption><strong>Suggested safety factors to be applied when designing infiltration facilities</strong></caption>+ − <tr class="success">+ − <th rowspan="2">Catchment area</th><th colspan="3">Consequence of failure</th> − <tr class="success"> − <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> − <tr><td> <100 m<sup>2</sup></td><td>1.5</td><td>2</td><td>10</td></tr> − <tr><td style="white-space: nowrap"> 100 - 1000 m<sup>2</sup><td>1.5</td><td>3</td><td>10</td></tr> − </table>
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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:
{{textbox|Drainage via infiltration be achieved through a number of LID BMP types:
*[[Infiltration chambers and trenches]] (underground)
*[[Infiltration chambers]] (underground)
*[[Infiltration basins]] (surface)
*[[Infiltration trenches]] (underground)
*[[Bioretention cells]] (surface)
*[[Exfiltration trenches| Exfiltration systems]] (underground)
*[[Bioswales]] (surface)
*[[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,
#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).
<br>
<br>
See [[Site considerations]] for further guidance on potential site constraints and LID facility type selection and design considerations.
===Planning===
===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]]