The Gigafactory is less than 20 miles from a drinking water reservoir (and recreation area) in one direction, and the city of Reno in the other.

~30 miles to Lake Tahoe.

And according to https://www.reno.gov/home/showpublishedimage/4088/6351980817..., it's about two miles from the watershed that feeds it.

NMP in particular readily biodegrades in aerobic environments, both in water treatment plants and just in water. Bacteria seem to crack it quickly. It's also not volatile. You have to protect yourself while working with it, but it's not comparable to really nasty stuff, like heavy metals.

I'm not aware of many (non-manmade) barren wastelands on Terra. Even the Empty Quarter has wildlife. About the only place I can think of would be something like the Dead Sea.

It’s not like the health of the public stopped Lonnie from installing a bunch of generators near poorer neighborhoods in Tennessee.

The desert is not a "barren wasteland." It is a valuable, vibrant ecosystem no different than any other.