[Ger-Poland-Volhynia] Stelmach : is this a Ukrainian surname?

[Miles Ertman]

Just curious, is the surname, "Stelmach" a Ukrainian surname?  In  
Alberta, the name is pronounced, "Stelmak".  Ed Stelmach is Alberta's  
new premier and the media state that he is the first Ukrainian  
premier of Alberta.  If this is a Ukrainian name, shouldn't the "ch"  
be pronounced as it is pronounced in English and not as a "k"?

I notice that there are "Stelmach", "Stellmach" in the German  
telephone book and a few "Stellmacher" in the St. Petersburg  
records.  There are also "Stelmach" variants in the master pedigree  
database.

Miles Ertman