Insulating below grade chilled water piping

[puzzled]

Does anyone have any experience of insulating long runs (1200 feet) of chilled water pex using closed cell spray applied foam?
The cost of pre insulated pex seems prohibitive, but maybe we are making a false economy.
The pex piping is 1.5 and 2 inch dia and will be 36" at least below grade in incredibly fast draining sand.
It would be great to hear from anyone who has tried this approach.

[nomadpeo]

not a clue, but my sense is this is a job for a contractor who specializes in it. good luck.