Difference between revisions of "Infiltration"
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Infiltration can still be optimized over 'tight' soils with infiltration rates ≤ 15 mm/hr: | Infiltration can still be optimized over 'tight' soils with infiltration rates ≤ 15 mm/hr: | ||
− | <li>[[Partially infiltrating bioretention]]</li></p> | + | <li>[[Bioretention:_Partial_infiltration|Partially infiltrating bioretention]]</li></p> |
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<p>Without infiltration, many LID design alternatives exist which can still capture and retain stormwater: | <p>Without infiltration, many LID design alternatives exist which can still capture and retain stormwater: |
Revision as of 19:07, 7 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 Testing
Infiltration tests must be undertaken at the location, depth and with a head of water that replicates the proposed design.
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.
<clearFix></clearFix>
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 |