Difference between revisions of "Groundwater"

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<poem>
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Where possible, it is recommended that [[infiltration]] BMPs maintain a 1.0 m vertical separation above the seasonally high groundwater table.
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==Target groundwater separation==
Retention of this unsaturated zone:
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In many areas of Ontario the target separation between the base of an exfiltrating LID practice and the water table is 1.0 m.
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This is to mitigate risks due to short periods of groundwater mounding and potentially unobserved seasonal fluctuations. In areas where a 1.0 m separation cannot be provided, or where conditions dictate that an even greater separation may be warranted, additional discussion and/or analysis specific to the physical characteristics of the site and the proposed design should be completed.
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The design practitioner is advised to consult with approval agencies to understand their requirements and/or expectations prior to undertaking work, and to complete an appropriate level of analysis to support their conclusion. The requirement for additional investigation and/or documentation supporting a proposed design may be reduced in areas where ≥ 1.0 m separation is anticipated.
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Retention of an unsaturated zone beneath the practice :
 
*Minimizes the potential for functional impacts associated with reduced percolation rates,
 
*Minimizes the potential for functional impacts associated with reduced percolation rates,
*Maintains the physical and biochemical water quality treatment benefits provided within the vadose zone,
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*Maintains the physical and biochemical water quality treatment benefits provided within the vadose zone.
*Minimizes the potential for localized groundwater mounding to affect nearby buildings or infrastructure, and/or
 
*Provides a factor-of-safety against potential uncertainties related to the elevation of the seasonally high groundwater elevation in areas of limited monitoring.
 
The requirement for additional investigation and/or documentation supporting a proposed design may be reduced in areas where ≥ 1.0 m separation is anticipated. 
 
In areas where a 1.0 m separation cannot be provided, or where conditions dictate that an even greater separation may be warranted, additional discussion and/or analysis specific to the physical characteristics of the site and the proposed design should be completed.
 
The design practitioner is advised to consult with approval agencies to understand their requirements and/or expectations prior to undertaking work, and to complete an appropriate level of analysis to support their conclusion.
 
</poem>
 
  
 
==Groundwater mounding==
 
==Groundwater mounding==
 
Groundwater mounding describes the localised raising of the water table beneath infiltration practices. It may be of concern if it affects nearby structures including building foundations.
 
Groundwater mounding describes the localised raising of the water table beneath infiltration practices. It may be of concern if it affects nearby structures including building foundations.
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When you wish to model the extent of groundwater mounding beneath an infiltration facility. This tool uses Hantush's derivation (1967). 
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{{Clickable button|[[Media:Hantush.xlsm|Download groundwater mounding calculator(.xlsm)]]}}
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Note that this is a minor adaptation (metric units and formatting) from the original tool, written and [https://pubs.usgs.gov/sir/2010/5102/ hosted by the USGS].
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===Preventing groundwater interaction===
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Many LID systems rely upon reuse, or evaporation and transpiration instead of infiltration to the ground. If the site cannot support any infiltration, consider
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*[[Rainwater harvesting]],
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*[[Flow-through planters]],
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*[[Green roofs]], or
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*[[Blue roofs]].
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==Oak Ridges Moraine Groundwater Monitoring Program==
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[[File:ORMGP.JPG|thumb|Depth to groundwater raster and contours from the ORMGP]]
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https://oakridgeswater.ca/
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The Oak Ridges Moraine focused program stretches from the Credit and Nottawasaga Watersheds in the west to the Trent River in the east and reaches from the shores of Lake Ontario northwards to beyond Lake Simcoe and the Kawartha Lakes. Within the publicly accessible maps section there is a depth to groundwater map layer. 
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===Other sources of groundwater data===
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*[http://ontariogroundwater.com/ Ontario groundwater]
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*[https://www.ontario.ca/environment-and-energy/map-provincial-groundwater-monitoring-network Provincial groundwater monitoring network map]
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Latest revision as of 19:49, 1 August 2019

Target groundwater separation

In many areas of Ontario the target separation between the base of an exfiltrating LIDLow Impact Development. A stormwater management strategy that seeks to mitigate the impacts of increased urban runoff and stormwater pollution by managing it as close to its source as possible. It comprises a set of site design approaches and small scale stormwater management practices that promote the use of natural systems for infiltration and evapotranspiration, and rainwater harvesting. practice and the water tableThe upper surface of the zone of saturation, except where the surface is formed by an impermeable body.Subsurface water level which is defined by the level below which all the spaces in the soil are filled with water; The entire region below the water table is called the saturated zone. is 1.0 m. This is to mitigate risks due to short periods of groundwater mounding and potentially unobserved seasonal fluctuations. In areas where a 1.0 m separation cannot be provided, or where conditions dictate that an even greater separation may be warranted, additional discussion and/or analysis specific to the physical characteristics of the site and the proposed design should be completed. The design practitioner is advised to consult with approval agencies to understand their requirements and/or expectations prior to undertaking work, and to complete an appropriate level of analysis to support their conclusion. The requirement for additional investigation and/or documentation supporting a proposed design may be reduced in areas where ≥ 1.0 m separation is anticipated.

Retention of an unsaturated zone beneath the practice :

  • Minimizes the potential for functional impacts associated with reduced percolation rates,
  • Maintains the physical and biochemical water quality treatment benefits provided within the vadose zone.

Groundwater mounding

Groundwater mounding describes the localised raising of the water tableThe upper surface of the zone of saturation, except where the surface is formed by an impermeable body.Subsurface water level which is defined by the level below which all the spaces in the soil are filled with water; The entire region below the water table is called the saturated zone. beneath infiltration practices. It may be of concern if it affects nearby structures including building foundations. When you wish to model the extent of groundwater mounding beneath an infiltration facility. This tool uses Hantush's derivation (1967).

Download groundwater mounding calculator(.xlsm)

Note that this is a minor adaptation (metric units and formatting) from the original tool, written and hosted by the USGS.

Preventing groundwater interaction

Many LIDLow Impact Development. A stormwater management strategy that seeks to mitigate the impacts of increased urban runoff and stormwater pollution by managing it as close to its source as possible. It comprises a set of site design approaches and small scale stormwater management practices that promote the use of natural systems for infiltration and evapotranspiration, and rainwater harvesting. systems rely upon reuse, or evaporationAbiotic transfer of water vapour to the atmosphere. and transpiration instead of infiltration to the ground. If the site cannot support any infiltrationThe slow movement of water into or through a soil or drainage system.Penetration of water through the ground surface., consider

Oak Ridges Moraine Groundwater Monitoring Program

Depth to groundwater raster and contours from the ORMGP

https://oakridgeswater.ca/

The Oak Ridges Moraine focused program stretches from the Credit and Nottawasaga Watersheds in the west to the Trent River in the east and reaches from the shores of Lake Ontario northwards to beyond Lake Simcoe and the Kawartha Lakes. Within the publicly accessible maps section there is a depth to groundwater map layer.

Other sources of groundwater data