Valmont was a doctor, a gradate of Université Laval. In 1912, he became a city councillor in the Saint-Roch ward (which today is the Jacques-Cartier ward), a post which he held until 1917.
After becoming mayor in 1926, Valmont soon contracted an unspecified illness and became bed-ridden for much of his term in office. His term of office was due to end in March 1928, but Valmont resigned in December 1927 due to this illness. He was succeeded by Télesphore Simard who completed the remaining months of the mayoral term of office.