Powering a recovery pump system for an Environmental Cleanup project site.

Kevin, the only thing you didn't tell us is the amount of time the pump will be working. If you have a certain flow rate, and know the tank capacity before the pump turns on and the gpm of your pump , you should be able to figure out how much time your pump operates on a daily basis.  Here's a little something to get you started....

First:  120 v x 10.5 amp = 1260 watts

So minimum size inverter would be 1500 - 2000 watts

Since it is just pump, you could go with a cheaper modified sine wave inverter rather than a more expensive pure sine wave one.

If the pump runs 10 hrs a day then:
10.5 amp x 10 hrs =105 amp-hrs

A 120 watt 12 v (or 240 watt 24 v) panel gives you 10 amps and would have to have 10 hrs of sun to give you the 105 amp hrs you need which of course is  little unrealistic.  2 panels would cut the sun time in half.

Battery back up for three days would require 3, 100 + amp hr batteries.
 
To keep the batteries up to charge,  3 times the above panel selection would be needed.

Size a charge controller from the amount of amps coming from your panels.  Size wiring according to voltage and ampacity. (HIgher the voltage and smaller the current, the smaller, and cheaper the wire)

 Three 120 watt 12 volt panels producing 10 amps each would require a minimum of a 40 amp controller.

There are calculators here at AltE to help you with sizing components to your system , as well as employees, if you can't figure it out on your own.