Honestly I’ve been dealing with ground squirrels (prairie dogs) for years and you’re only hope is exclusion - fencing off an area and keeping them out. There are far too many of them and too few of you. You have no possibility of killing them all (short of an infinity gauntlet and a snap of your finger) and your efforts will be a waste of energy. Exclude their food source and bring in a natural predator, that’s it.
One thing I will say is this - NEVER USE POISON BAIT!
Poison bait is an absolute danger to children and household pets. As well, poison bait never kills instantly and, when the gopher becomes sick, it will wander outside its but burrow and become easily predated. This will lead to a secondary kill of its direct predator, and possibly the predator’s offspring, thus reducing the predators population and actually INCREASING the target creatures population. Here in the desert we have dozens of cases every year of owls and hawks that get killed through secondary poisoning. Pack rats and ground squirrels can gestate multiple times per year whereas their predators will gestate on a few times over multiple years. Thus, one poisoned rat can wipe out the predator population leaving its fellows free to flourish. Poison is not ever helpful.
And yes, mixing bleach and ammonia is dumb. It creates chloramine mostly which will make you very sick. Given the vigorous and uncontrolled nature of the reaction, pouring the chemicals down the hole is a sure fire way to get yourself hurt and/or sent to the ER for resuscitation and oxygen therapy.
