Sept. 9, 2025
The tallest new dam built in the United States in the last 25 years is now complete. Crews celebrated the huge milestone during an all-site safety meeting on Aug. 7.
The final lift of asphalt was placed on July 18 and the final lift of rockfill was placed on Aug. 7. Then, crews put a thin layer of road base along the top to cover and protect the asphalt core. To complete the main dam, 36-inch boulders were placed every few feet along the top of the 3,600-foot-long stretch as a vehicle fall protection barrier.
The main dam at Chimney Hollow contains almost 13 million cubic yards of rockfill and 75,000 cubic yards of asphalt. Crews put in over 1,000 workdays and 3.3 million work hours to complete the construction of the dam.
The WALO asphalt batch plant and asphalt core paver have been demobilized and are on their way back to Switzerland in a series of shipping containers.
All that remains are a few punch list items such as installing station markers every 100 feet along the top of the dam, completing a new Northern Water weather station on the west side and finishing the markers on the staff gauge.
With this large component wrapping up, all night work is now complete and the total number of staff on site is down to less than 100 individuals (from 500 employees on site at peak production).