Difference between revisions of "Infiltration"
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<p>[[Infiltration: Testing|Infiltration tests]] must be undertaken at the location, depth and with a head of water that replicates the proposed design. </p> | <p>[[Infiltration: Testing|Infiltration tests]] must be undertaken at the location, depth and with a head of water that replicates the proposed design. </p> | ||
<table> | <table> | ||
− | <table class = "table-responsive table table-striped"> | + | <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> | + | <caption><strong>Suggested safety factors to be applied to measured percolation rate when designing infiltration facilities</strong></caption> |
− | <tr class="success"> | + | <tr class="success"> |
− | <th rowspan="2">Catchment area</th><th colspan="3" class="text-center">Consequence of failure</th> | + | <th rowspan="2" class="text-center">Catchment area</th> |
− | <tr class="success"> | + | <th colspan="3" class="text-center">Consequence of failure</th> |
− | <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> | + | <tr class="success"> |
− | <tr><td> <100 m<sup>2</sup></td><td>1.5</td><td>2</td><td>10</td></tr> | + | <th class="text-center">No damage or inconvenience</th> |
− | <tr><td style="white-space: nowrap"> 100 - 1000 m<sup>2</sup><td>1.5</td><td>3</td><td>10</td></tr> | + | <th class="text-center">Minor damage or inconvenience to external structures (e.g. ponding in parking lot)</th> |
− | </table> | + | <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> | <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> | <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> |
Revision as of 19:37, 10 July 2017
Infiltration of stormwater into underlying soils is one the priority level 1. mechanisms to achieve MOECC Runoff Volume Control targets.
Infiltration is promoted through a number of LID BMPs:
- Infiltration chambers and trenches (underground)
- Infiltration basins (surface)
- Bioretention cells (surface)
- Bioswales (surface)
Constraints[edit]
Infiltration practices are not recommended:
- Where the bedrock is within 1 m below the bottom of the proposed BMP,
- 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, - Over swelling clays or unstable sub-soils,
- Over contaminated soils or sites with high risk of contamination from onsite activities,
- 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 where the ecology and natural hydrology are dependent upon surface water,
- Where prohibitions and/or restrictions exist per approved Source Protection Plans (see MOECC guidance).
Infiltration can still be optimized over 'tight' soils with infiltration rates ≤ 15 mm/hr:
Without infiltration, many LID design alternatives exist which can still capture and retain stormwater:
Planning[edit]
Soil infiltration rate
Infiltration tests must be undertaken at the location, depth and with a head of water that replicates the proposed design.
Catchment area | Consequence of failure | ||
---|---|---|---|
No damage or inconvenience | Minor damage or inconvenience to external structures (e.g. ponding in parking lot) | Significant damage to buildings or infrastructure (e.g. flooding damage) | |
<100 m2 | 1.5 | 2 | 10 |
100 - 1000 m2 | 1.5 | 3 | 10 |
Groundwater
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.
- REDIRECT Special:ArticleFeedbackv5