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?
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Foundation drains daylighting below 100 yr. BFE
- Thread starter rcspiel
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Every foundation drain in Florida south of Tampa discharges below the 100 year flood elevation, because FFEs are all set 0.01 ft above the BFE.
Moral of the story is this: "it depends on where you're at."
Question, though. Are you saying the 100 year is only 3.75 ft up from the normal water surface in the river? You sure about that? What's the 1 year, 5 year, and 10 year stage in the river?
Hydrology, Drainage Analysis, Flood Studies, and Complex Stormwater Litigation for Atlanta and the South East -
Moral of the story is this: "it depends on where you're at."
Question, though. Are you saying the 100 year is only 3.75 ft up from the normal water surface in the river? You sure about that? What's the 1 year, 5 year, and 10 year stage in the river?
Hydrology, Drainage Analysis, Flood Studies, and Complex Stormwater Litigation for Atlanta and the South East -
- Thread starter
- #5
Yes,the 100 yr. BFE of the river is approx. 3.75' higher than the NWL based on studies. In fact, it may be less with the new flood study FEMA is conducting. A dam (used by a power plant now gone) exists just downstream of the site. Does silt back up when foundation drains become inundated with flood water or do you use flapper gates in Florida? Are the foundations drains wrapped in filter fabric to keep fines out?
GeoPaveTraffic
Geotechnical
Guess I'm the odd man out here.
I would not want any foundation drain to exist at an elevation that could be covered by flood water. Instead I would use a closed system and a sump pump.
Mike Lambert
I would not want any foundation drain to exist at an elevation that could be covered by flood water. Instead I would use a closed system and a sump pump.
Mike Lambert
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