Basement in high water table
Basement in high water table
(OP)
Hi, I'm an unlucky homeowner with a finished(tile) basement that has a high water table from an irrigation ditch that flows in the summer. The water table is a foot below our poured cement slab. We have a layer of 1-2" gravel under the slab with an airspace on top of gravel. We have a working exterior footer/french drain that empties to daylight (downstream) at road in front of house. The only time the basement flooded slightly was when the footer drain outlet was clogged with leaves. We have a deep interior closed sump pit in basement that is only draining an exterior stairwell and and a furnace room.The house is 50 years old.
Can anyone out there in engineering land help us brainstorm options to help us stay dry? We are thinking along the lines of drilling holes on bottom of closed sump, adding several continuous run low flow sumps, adding outside sump, taking scuba lessons.
Can anyone out there in engineering land help us brainstorm options to help us stay dry? We are thinking along the lines of drilling holes on bottom of closed sump, adding several continuous run low flow sumps, adding outside sump, taking scuba lessons.





RE: Basement in high water table
Assuming that ditch water is what is feeding ground water to the house, consider a man hole outside with a sump pump in it discharging well away from the building. Feeding to that manhole would be perforated pipes in a trench (dug and then filled) that intercepts that water before it gets to the house. Backfill around that perforated pipe should be a filter material. While some here may call for clear gravel that is enclosed in a filter fabric, I have 100 percent success with the following. The backfill is a filter made from the fine aggregate used in concrete, ASTM C-33. The pipe has holes on the bottom quarter 3/16" diameter. The concrete sand can be dumped in over the pipe. In case of trench sides caving in as you dig, you can keep ahead of that caving by that method. Whereas with a caving trench and fabric surrounding gravel, good luck,.
Any sump pit with holes and no filter could work, if somehow that nearby soil is well graded sand and gravel, but otherwise it may bring along soil and cause undermining.
I've used the "moat around a castle" term for the cut off drains. It does not involve messing up the inside of the building, but you have to dig sufficiently low to be effective.
RE: Basement in high water table
To construct, you can feed the pipe into the trench behind the excavator and immediately backfill as you work along. Much better in caving ground than the fabric around the rock system.
RE: Basement in high water table
RE: Basement in high water table
RE: Basement in high water table
RE: Basement in high water table
Sounds good, but with any fix keep the filter business in mind. A reference on this may be found at the NAVAC web sites under DM (design manuals).
I'll try to attach the figure showing information on proper filters.
You may see clear water, but the proof would be seeing no"delta" at the pump discharge.