Out here, there are specifically-engineered soil mixes required by law, usually trucked in, then spread atop septic fields/areas with low to no percolation (out here, limestone rock).
These manmade sewage drainfields / irrigation fields are planted with grasses and other mowable plants (again, specified by regulation) that are meant to be able to absorb sewage water that is aerated / sprayed onto the surface using sprinkler heads above grade. These engineered septic fields are supposed to be flat; be situated away from wells, caves, big cracks in the ground/rock, creeks, rivers; be situated well-apart from where people might live; and operate perfectly in all kinds of extreme Texas weather (drought, flood, hard freezes, etc.), all day every day.
The solids collect in septic tanks (typically below grade, good luck carving out that hole for it!). Full septic tanks are emptied by big tanker trucks (sludge transporters) that suck out the solids, driving the load “away” to be competently processed, one would hope, by some big ol’ sewage treatment plant in a civilized part of the county that has infrastructure and engineers and chemicals and stuff.
There are state and county, and in some cases inside a city limit, city regulations that factor into design and implementation and operation. The Texas Council on Environmental Quality relies on individual counties and cities to make sure state regs are obeyed. Ish.
In the case of massive amounts of sewage disposal, it is common for treated effluent (filtered sewage water that has been minimally processed and then dosed with chlorine to sanitize) to be applied to golf courses, which are thus septic irrigation fields. A lot of 'burbs have golf courses here for the purpose.
Poop water’s gotta end up someplace and to do that cheaply, the closer that place is, the “better.” /s
(I have plenty to say on the matter but that’s even longer and more off-topic than I already am.)
Rock saw excavators are a common sight here, and are necessary to lay in utilities, sometimes, if those utilties can’t be strung up on poles. They make terrific noise and dust, and consume enormous amounts of fuel.
The steel teeth on those blades have to have carbide tips to work out here. The teeth are built to snap off cleanly when they break, so the whole cutting wheel or chain is not ruined.
Plumbing in our part of Texas depends on use of these machines for installation, then soils, gravity, topography and electric power if some of these are not in one’s favor. Yes, the pvc pipes delivering potable water are laid in the ground, bedded in sand ideally, though the deeper the pipes are laid, the more expensive to install, so often they are laid in at minimum depth. Very very minimum. As required by law. Usually.