Walter C. Giebel was born in Nelson, Wisconsin, on September 20, 1888, the son of Edmund Giebel, a banker and merchant. Walter studied mechanical engineering at the University of Wisconsin. He and his brother Raymond left Wisconsin about 1912 to haul freight from Malta to Zortman and Landusky, Montana. When this proved unprofitable due to bad roads, the brothers homesteaded near Big Sandy. They also hired out with their Big Four tractor in 1913 to plow land for neighboring farmers. When the two brothers registered for service in World War I, Edmund Giebel moved to Big Sandy to look after his sons' homestead. World War I was over, however, before Walter could be called into service. Edmund bought a Ford dealership in Big Sandy, where Walter worked for many years as a mechanic.

In the summer of 1937 Walter Giebel formed a partnership with his sister's husband John H. Patterson, of Nashua, Montana, to work the Green-Campbell Mine near Silver Star in Madison County. The Green-Campbell had been located in 1867, and was a major gold-producer. A ten-stamp mill was built in 1868. In 1938 Giebel and Patterson brought in several other men including Adolph F. Chan of Nashua, and C.L. Hober of Great Falls, and formed the Green-Campbell Mining Company, with Chan serving as president and Giebel as general manager. In August 1942, the War Production Board (WPB) ordered the shut-down of all gold mining operations. When the Montana Supreme Court ruled that the company could not make a claim for damages against the WPB, the company's assets lost their value.

In November 1943, Giebel, C.L. Hober, and George E. Hurd formed the Montana Western Mining Company to operate the Emma Mine for strategic minerals at Rochester near Twin Bridges. This company operated until the end of the war.

After World War II Giebel worked as a mineral dressing engineer for various mining companies, including the U.S. Gold Corporation (1954); the Victoria Mine west of Silver Star (1959-1967); the Rico Argentine Mining Company in Rico, Colorado; and several companies in Arizona and Mexico. He also taught at the Montana School of Mines in Butte. Giebel was very active in developing theoretical solutions to ore processing and sampling problems. Shortly before his death he designed and supervised construction of the Hilger Mill in Lewistown.

Giebel died on May 2, 1978, at the age of 89.