Groundwater & Basement Water Intrusion in Mead Valley, CA

That is compacted decomposed granite doing exactly what it does. Undisturbed, this material takes water reasonably well; graded and driven on for years, it seals into a hard surface that sheds nearly everything. The driveway then becomes the primary channel on the property. A cross drain or a shallow diversion partway up the drive, moving water off it before it reaches the building, solves more of this than anything done at the garage door.

It depends almost entirely on where the casing sits. A wellhead in or beside a natural drainage path can take surface water directly if it becomes submerged, and that water carries whatever the property surface was holding. Raising the casing and grading the ground away from it are inexpensive and permanent. After any event where the head was underwater, the water needs disinfection and testing before it is used for drinking, whatever it looks like.

Not necessarily. A leach field disposes of effluent by letting it soak into the soil, and when that soil is already saturated by winter storms there is nowhere for it to go. The system backs up, then recovers as the ground drains. Repeated slow performance every wet season, or backups that do not clear, do point at a field at the end of its capacity, which is a different and much larger job than a tank pump-out.