According to this[1] the weight for 1 cubic meter of dry soil is 1200kg, so 6 grams of uranium per cubic meter.
Looking at average suburban lot sizes, they seem to be about 7200 sqft , which is about 668m^2.
Which gives 668m^3 which gives about 4kg of uranium shockingly.
[1] https://www.reference.com/science/much-cubic-meter-soil-weig...