Usage of the phrase "when once"

I heard some local speakers say "when once," for example:

"When once I am there, I'd let you know."
"When once the money is deposited, I'd make a transfer into your account"

I think only one of the words should be used instead of the two simultaneously.

When once is an older way of saying "whenever". As you can see, if we put "whenever" in your sentences, they have the same meaning:

"whenever I am there, I'd let you know."

and

"Whenever the money is deposited, I'd make a transfer into your account"

Also, "when once" is not necessarily "redundant." See this excerpt from

A Celtic Christology: The Incarnation according to John Scottus Eriugena, by John F. Gavin:

Here, both when and once are needed to get the full meaning of the conjunction. It is not just when he was... or once he was... but when once...

"When once" is not used much today, but it's good to know what it means when once you run across it.