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LID SWM Planning and Design Guide β



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=Target groundwater separation
===Target groundwater separation==In many areas of Ontario the target separation between the base of an exfiltrating LID practice and the water table is 1.0 m. This is to mitigate risks due to short periods of groundwater mounding and potentially unobserved seasonal seasnal 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.
*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 table beneath infiltration practices. It may be of concern if it affects nearby structures including building foundations.