In that case here is something to think seriously about.
How far away from your plant is the share holder owned utility.
Depending on how far away and what your plants electrical usage is the power company would more than likely be very willing to run new service out to your plant.
It is surprising how much better service you get when a companys profit depends no keeping its you happy.
I would think your system reliability would be better served with a larger reservoir, if using ground water, or a Million gallon storage tank if using surface filtered water.
In both of these cases, auxiliary power is fairly common, with less than a 100kW genset with 72hr daytank serving most emergencies.
The Reservoir would likely provide a 3-7day reserve even without plant operations, while maintaining fire fighting capacities to a reasonable extent.
Compared to other utlities, the water distribution system is probably one of the best able to buffer an electrical power outage. Electrical power required to operate pressure tanks and pumps is much less per capita than most other utilites, and the potential energy may be stored in an elevated tank if necessary at competitive costs in most metropolitan, suburban, and rural areas.