Difference between revisions of "Infiltration"
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− | + | Infiltration of stormwater into underlying soils is one the priority level 1. mechanisms to achieve MOECC Runoff Volume Control targets. In many areas of Ontario, where >municipal supplies of potable water are drawn from aquifers, it's also an important mechanism for groundwater recharge.</p> | |
− | {{TextBox| | + | {{TextBox|Infiltration is promoted through a number of LID BMPs: |
*[[Infiltration chambers]] (underground) | *[[Infiltration chambers]] (underground) | ||
*[[Infiltration trenches]] (underground) | *[[Infiltration trenches]] (underground) | ||
Line 8: | Line 8: | ||
*[[Bioswales]] (surface) | *[[Bioswales]] (surface) | ||
}} | }} | ||
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− | + | ==Constraints== | |
Infiltration practices are not recommended: | Infiltration practices are not recommended: | ||
#over swelling clays or unstable sub-soils, | #over swelling clays or unstable sub-soils, |
Revision as of 23:46, 14 August 2017
Infiltration of stormwater into underlying soils is one the priority level 1. mechanisms to achieve MOECC Runoff Volume Control targets. In many areas of Ontario, where >municipal supplies of potable water are drawn from aquifers, it's also an important mechanism for groundwater recharge.
Infiltration is promoted through a number of LID BMPs:
- Infiltration chambers (underground)
- Infiltration trenches (underground)
- Dry ponds (surface)
- Bioretention cells (surface)
- Bioswales (surface)
Constraints[edit]
Infiltration practices are not recommended:
- 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,
- in areas where increased infiltration will result in elevated groundwater levels, which can be demonstrated to damage critical utilities or private property, or
- where prohibitions and/or restrictions exist per approved Source Protection Plans (see MOECC guidance).
Infiltration facilities should be designed with drainage modifications where:
- the underlying bedrock is within 1 m below the bottom of the proposed BMP, or
- the seasonal high groundwater level comes within 1 m below the bottom of the proposed BMP.
Designing with constraints[edit]
Infiltration can still be optimized over 'tight' soils with infiltration rates ≤ 15 mm/hr:
Where infiltration is impossible, LID design alternatives exist which can still capture and retain stormwater:
Planning[edit]
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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 |