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Results found in several dictionaries: Collins, Collaborative Dictionary
spadework  n  (fig) trabajo  m  preliminar

Collaborative Dictionary     English-Spanish
spadework n. el trabajo preparatorio Reverso General Dictionary 
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'spadework' also found in translations in Spanish-English dictionary
trabajo preliminar pref. spadework Reverso General Dictionary 

"Collins Spanish Dictionary 8th edition published in 2005 © William Collins Sons & Co Ltd 1971, 1988 © HarperCollins Publishers 1992, 1993, 1996, 1997, 2000, 2003, 2005"