A mile is 1609m

A sq mile is 1609x1609 = 2,588,881 square meters

Times 10m, 25,888,810 cubic meters

A cubic meter of water weighs 1000 Kg

I think you're right. Here's my math:

https://www.wolframalpha.com/input?i=%28%281+square+mile+*+1...

Don’t think it’s even a year… should be 8-9e6 m^2 per year, or 3-3.5 mi^2 per year.

> Is your math right? 90 million tons of water/10 m gets me 1.7 km2, so a 1 sq mi landfill would last around ... 1 year, not 287.

You're right, looks like I forgot to convert liters to tons.

>On the other hand, I'm not sure you can just assume that waste has the same density as water; from a cursory glance it seems to about 1/3.

is this before or after compaction? Intuitively speaking, most things I throw out would sink in water. A garbage bin/trash bag might float because it has a bunch of air, but presumably that will all get pushed out when buried 10 meters deep.

Well you clearly don't have great intuition

Why is that, could you elabotate?