I really don't think you can. API 1102 uses a 144 sqin ( 1 sq ft) wheel contact area but the formula and graphs relate to a load on that area, not a large superimposed load.
however 1000 psf is 50kPa or 5 tonnes per sq m. If the load is really a uniform spread out load that isn't that big a figure.
If it passes a wheel load of 10,000 lbs it should be good for 1000 over a larger area.
A bigger issue is settlement and shear loads if the ground compacts under the load and remains as is on the unladen part. You need to get a geotech assessment of the area.
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