June 8, 2023

Main Dam Nears 100 Feet

Chimney Hollow Reservoir’s main dam is expected to reach 100 feet by mid-June. To reach that goal, crews will raise the dam 7.5 feet each week, which requires approximately 1.4 million cubic yards of rockfill material and 8,000 cubic yards (about twice the volume of an Olympic-size swimming pool) of asphalt. Crews will place 10, 9-inch asphalt lifts per week for a total of 134 lifts to reach the 100-foot milestone. 

Chimney Hollow has many project features, all of which must be synchronized to remain on schedule. For the next two years, approximately 10 haul trucks will empty 100 tons of rockfill material every two minutes, 20 hours a day. Additionally, 17 40-ton haul trucks will operate during the day (and three at night) to keep materials moving.   

“The project is a well-orchestrated machine that must all work together,” said Joe Donnelly, Northern Water’s Principal Project Manager for the Chimney Hollow Reservoir Project. 

Seeing visual changes to the main dam helps generate enthusiasm and boosts employee morale on site. 

Rockfill on the side of the main dam
From the downstream toe (north) of the main dam embankment, looking east toward the right abutment.

“It’s important to celebrate success when we hit our targets and achieve the project’s goals,” Donnelly said.