Why has Florida DEP mandated a pump intake be placed two feet below the water column when purging?

If pump intake placement doesn’t matter why would the Florida DEP mandate that his pump intake be placed two feet below the water column when purging a non-submerged screen well?

Unfortunately, when the original 2002 version of the Florida DEP’s SOP FS2200 came out it did not have any of those requirements in it. When they revised it in 2006, they came up with limitations on screen length, and they came up with pump position limitations. Unfortunately, none of it seems to be based on any science that I can identify. So, the answer to your question is I don’t know.