Not to get too technical here, but gophers don't normally live in colonies. If your setting is in Texas, think prairie dogs. An added benefit here is that they don't just skulk quietly around in ther tunnels, they also stand up and yell at you making for a great showdown scene.
Actually, in the southwest, there's a critter generally called a "gopher" that is technically a ground squirrel. It looks like a miniature prairie dog. True prairie dogs are rare enough that there's been some talk of putting them on the endangered species list.
Gophers -- the southwest kind -- are very definitely a colony animal. I can provide pictures if need be. ;-)
I wage war on them every summer as they like my field, and I have goats, and sooner or later somebody's going to break an ankle. And it might just be ME. Plus they commit suicide by drowning in the goat's water, and then the goats won't drink it. And they're murder on a garden.
To the OP, the best way to explode a colony is with propane. They make commercial colony-exploding devices that sort've look like a weed whacker. Push one button, and propane floods the burrows. Push another, and it sparks and ignites the propane and whoooooosh. Great hilarity is had by all (particularly if a few beverages are involved) except for the gophers. This is not the safest method, however, and many injuries have resulted, plus a few wildfires.
Other methods for gopher eradication include dry ice in a bucket of hot water set down next to the highest hole; put a barrel over the top and the expanding CO2 is forced into the burrows and asphyxiates them. A less creative form of gassing them is to use auto exhaust. Drowning is also a favorite -- though I've run a hose full blast into a network of burrows for three hours straight and not filled it up. (Judging by the odor later, which smelled rather like large dead cow, I did kill some.)
There are also traps which work okay but are somewhat labor intensive.
My personal method of choice is a BB gun. It's quick, humane, and fairly efficient.
Gopher holes also tend to harbor snakes, including ones with buzzing tails, if you need to add more excitement to your exploding-gopher scene.
-- Leva
(NOT a fan of gophers. The local name may be gophers, but I've been known to refer to them as garden rats.)