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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. 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 :