Is it acceptable to daylight foundation drains below the 100yr BFE? or is it better to have the foundation drain system separated so backup does not occur during the 100 yr event. I have an existing building (100,000 sf.) that exists inside the 100 yr floodplain next to a river. Existing FF = 100.00 Proposed FF = 101.75 Existing BFE = 100.46. Approximate NWL = 96.71 Foundation drains (4") to be placed with invert at approx. 99.67 and existing walls backfilled to 108.00. Is this a bad design?