When it opened in 1927, Pacific Coast Coal Company’s New Black Diamond was one of most modern coal mines in the western U.S. A million-dollar tunnel under Cedar Mountain connected the rich coal seams with the surface facilities built near the Cedar River along the Maple Valley highway. Starting in 1926 and over the next 16 years, the mine produced over 2.4 million tons of coal before closing in 1941. This photo dated March 15, 1941 appeared in the Seattle Times as the mine equipment was being dismantled. Shown here is the Rheolaveur wash plant, which Pacific Coast Coal placed into operation in October 1927. The mine, and plant were featured in the April 1929 issue of the Mining Congress Journal. Rheolaveur derives from the Greek ‘rheo’ meaning flow and the French ‘laveur’ translated as cleaner or washer. And that is exactly how the plant operated: water flowing over coal to clean and wash out impurities. Though located three miles south of Renton, the mine was named New Black Diamond because it replaced the company’s historic mines in Black Diamond. Miners rode trains daily to and from Black Diamond to cover the three shifts. The last remnant of the New Black Diamond mine, the company’s administration building later known as the King County shop, was recently torn down when Sunset Materials ceased operating at the facility. In July of 2016 the property was purchased by the asphalt paving company, Lakeside Industries. This photo comes courtesy of JoAnne Matsumura, an Issaquah-based researcher and former archivist at the Black Diamond Historical Museum.
