Our distance to the endpoint for the worst-case release is 0.3 miles. The nearest public receptor is 0.32 miles away. What tools are available to document that the public receptor is beyond the distance to the endpoint so we can qualify for Program 1?

The results of any air dispersion model (from EPA’s guidance documents or other models) are not precise predictions. They represent an estimate, but the actual distances to the endpoint could be closer to or farther from the point of release. If your distance to the endpoint and distance to a public receptor are so close that you cannot document, using a USGS map, that the two points are different, it would be advisable to comply with the higher Program level. The most detailed maps available from the US Geological Survey (scale of 1:24,000) are accurate enough to map the distances you cite and document that the two points (which are about 100 feet apart) differ. GPS systems may also allow you to differentiate these points.