133
edits
Changes
Jump to navigation
Jump to search
mLine 1:
Line 1: − <p>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 to recharge groundwater supplies.</p>+ − + + − + − ===Constraints===+ + − + − #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,+ − #Over swelling clays or unstable sub-soils,+ − + − + − + − + − + − + − + − + + + + − ----+ − + − + + − ===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}}+ + + + + + + + + + + +
→Constraints
{{TOClimit|2}}
{{TextBox|1= Infiltration is promoted through a number of LID BMPs:
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.
{{textbox|Infiltration is promoted through a number of LID BMPs:
*[[Infiltration chambers]] (underground)
*[[Infiltration chambers]] (underground)
*[[Infiltration trenches]] (underground)
*[[Infiltration trenches]] (underground)
*[[Dry ponds]] (surface)
*[[Dry ponds]] (surface)
*[[Bioretention cells]] (surface)
*[[Bioretention]] (surface)
*[[Bioswales]] (surface)
*[[Bioswales]] (surface)
}}
}}
==Constraints==
Infiltration practices are not recommended:
Infiltration practices are not recommended:
#Where the bedrock is within 1 m below the bottom of the proposed BMP,
#over-swelling clays or unstable sub-soils,
#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,
#Over contaminated soils or sites with high risk of contamination from onsite activities,
#in areas where the ecology and natural hydrology are dependent upon surface water,
#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 increased infiltration will result in elevated groundwater levels, which can be demonstrated to damage critical utilities or private property, or
#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).
#Where prohibitions and/or restrictions exist per approved Source Protection Plans (see MOECC guidance).
<br>
===Designing within constraints===
Infiltration facilities should be designed with drainage modifications where:
{{TextBox|1= Infiltration can still be optimized over 'tight' soils with infiltration rates ≤ 15 mm/hr:
#the underlying bedrock is within 1 m below the bottom of the proposed BMP, or
*[[Bioretention: Internal water storage |Bioretention with internal water storage]]8
#the seasonal high groundwater level comes within 1 m below the bottom of the proposed BMP.
*[[Bioretention:_Partial_infiltration|Partially infiltrating bioretention]]
===Designing with constraints===
{{textbox|Infiltration can still be optimized over 'tight' soils with infiltration rates ≤ 15 mm/hr:
*See [[Underdrains]] for [[Bioretention]] and [[trees|tree pits]], and
*Results from STEP studies over [[low permeability soils]]
}}
}}
{{TextBox|1= Where infiltration is impossible, LID design alternatives exist which can still capture and retain stormwater:
{{textbox|Where infiltration is impossible, LID design alternatives exist which can still capture and retain stormwater:
*[[Bioretention: Non-infiltrating | Bioretention planters]]
*[[Stormwater planters]]
*[[Rainwater harvesting]]
*[[Rainwater harvesting]]
*[[Green roofs]]
*[[Green roofs]]
*[[Blue roofs]]
}}
}}
==Planning==
===Hydrogeology===
The Conservation Authorities Geoscience Group has prepared a guidance document which attempts to standardize the hydrogeological study requirements for development applications made to Conservation Authorities. It is a helpful guide for all low impact development applications which include infiltration. It is provided with the caveat that not all sections or content are necessary or appropriate for every case. Pre-consultation with your Conservation Authority and municipality is strongly recommended in all cases.
'''[http://www.lsrca.on.ca/Shared%20Documents/permits/hydrogeological%20_guidelines.pdf?pdf=Hydrogeological-Guidelines Hydrogeological Assessment Submissions Conservation Authority Guidelines for Development Applications]'''
==Beginning a BMP design?==
See [[Design infiltration rates]]
----
==See also==
*[[Groundwater]]
[[category:Infiltration]]
[[category:Infiltration]]