Sump / sewage pumps ... one of my favorite topics!
I'll tell you how, IMO, the job should be done. Period. Seldom seen, but still 'right.'
First off, don't put any sort of box or receptacle IN the pit. Even if they don't fill with muck or condensation, they will corrode at warp speed. Good luck undoing any screws. Ditto for the life expectancy of any wiring devices in the pit.
The only 'wiring accessory' in the pit should be a hook to hang up the coiled excess cords. (You'll want extra there when you need to replace something). You need this hook, or the wires will get tangled with the floats.
What you do is set a handhole right next to the pit. Connect the handhole to the pit with TWO large diameter sweeps, entering the bottom of the handhole.
Forget cable fill tables; the cable jackets WILL swell- a lot. Better to use 'huge' sweeps.'
I prefer sweeps to a straqight pipe run because they allow you to pull straight up, and foster drainage. Even so, there needs to be several inches of gravel under that handhole for drainage.
One sweep is for the float wires. The other is for the power wires.
Leave the wires LONG. Long enough to come out of the ground a couple feet. Unless, of course, you like working by laying on your belly and reaching into the muck to make your connections.
IDENTIFY the wires. Be able to tell, at a glance, which wires go to 'pump 1' or the 'middle float.'
Connections are made best by using wire nuts, then inserting the whole thing into a little epoxy pack. If the pump is for 'clean' water, you can get away with just dipping the nuts into Scotch-kote. When you fold - not coil- the wires into the handhole, set the nuts so they will tend to drain.
GFCI protection is generally not required, and maybe not even desireable. That's another discussion. What matters here is that the GFCI, if there is one, be located indoors, away from the pit, maybe even at the breaker.
