Lift Station Buoyancy
Lift Station Buoyancy
(OP)
I've noticed on several details here in my office that for a concrete wet well (sewer lift station), the caisson section is keyed into the concrete base. There are no other notes or details for anchoring or connecting the sump to the base. Should there be some kind of anchoring to prevent uplift on the circular portion of the sump. I realize that the base is sized to resist the uplift forces through it's weight, but if the circular section is not attached with some sort of rebar or dowels, then wouldn't the sump float up with the base not moving? What would be a proper way to tie in to each other?





RE: Lift Station Buoyancy
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The base typically extends outward at least 12" beyond the cylinder to prevent uplift of the lift station.
You can use the concrete-pipe.org brochure on manhole floatation to calculate the uplift forces:
http://www
RE: Lift Station Buoyancy
Steve
RE: Lift Station Buoyancy
However, I'm not sure you should necessarily want to immediately abandon your intuition of somehow tying walls to bases only on this revelation without further investigation. It has already been inferred that if it is desirable to handle a station as one piece, attachment would be helpful in that case. I also wonder a little what if the surrounding environment was not "fluid" (not buoyant conditions, but there was instead some tendency for whatever reason of the base to settle downward instead of float (and even relative to walls for whatever reason might be somehow held up by some sort of non-obvious inverse action, say with more firm/founded surrounding backfill?) Of course, with fluid in the station that fluid would exert a pressure DOWN on the bottom. I guess the odds or experience of that happening could be so low however that tying might not have been economically or otherwise justified/ in the design you are looking at?
As far as exactly how to tie the base in considering all, I alas don't know enough about that business to answer that question!