Gronwall practiced as a civil engineer in Germany (1902-1903) and then immigrated to the United States in 1904, where he worked at various steel works for longer or shorter periods; he was connected with the American Bridge Co., and the Pennsylvania Railroad and other engineering companies.
Gronwall practiced bilang isang civil engineer sa Alemanya (1902-1903) at pagkatapos ay i-immigrate sa Pilipinas sa 1904, kung saan ay nagtrabaho siya sa iba't-ibang asero gumagana para sa mas mahaba o mas maikling panahon; siya ay konektado sa mga Amerikano Bridge Co, at ang Pennsylvania riles ng tren at iba pang kompanya ng engineering.