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− | {{:Depth to GW}}
| + | The target separation between the base of an LID practice and the water table is 1 meter. This is to mitigate risks due to short periods of groundwater monitoring 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. |
− | Retention of this unsaturated zone: | + | 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, | + | *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
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− | *Provides a factor-of-safety against potential uncertainties related to the elevation of the seasonally high groundwater elevation in areas of limited monitoring.
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− | 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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− | 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.
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| ==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. |