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 *
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.