Seattle City Light Powerhouse Upgrades and Dam Safety Inspections

Diablo Dam Aerial

Seattle City Light Powerhouse Upgrades and Dam Safety Inspections

Reinforcing Seattle’s Power Supply with Modernized Powerhouses and Reliable Dams

Reliably operating hydroelectric generators and dams is critical to Seattle City Light. SCL was the first utility in the United States to achieve a carbon neutral status — an accomplishment still achieved today as a result of hydropower leading its generation mix. We’re working alongside SCL as owner’s engineer to upgrade generators at Diablo Powerhouse and Boundary Powerhouse, and to conduct dam safety inspections at Diablo Dam, Ross Dam and Gorge Dam. 

Hydropower Powerhouse Upgrades

Together, the Diablo and Boundary Powerhouses supply more than half of the power in SCL’s total energy portfolio, which serves over 450,000 metered customers. We’re working alongside SCL to overhaul aging units at both powerhouses to improve capacity, performance and reliability of two enclosed, vertical Westinghouse generators, and three vertical General Electric generators. We also supported engineering and procurement efforts for the rebuild of two large Toshiba units. 

As part of powerhouse modernization efforts, we paired our former OEM designers with SCL to forecast potential generator capacity. The forecasts considered the benefits of increasing the continuous capacity of the Boundary and Diablo generators with the goal of adding an additional 40 years of service life.

Dam Safety Inspection Using Drones, Artificial Intelligence and Machine Learning 

To ensure the safety of the utility’s dams, we’re partnering with SCL to inspect Diablo Dam, Ross Dam and Gorge Dam. Field inspections, including helicopter survey of the reservoir rim, were conducted on the concrete gravity and concrete arch dam sections at all three sites. Rope access inspection of the gates and spillways were conducted at Diablo Dam and Ross Dam. At Diablo Dam we augmented traditional dam inspection with a drone survey. The drone allowed a safe and detailed extension and augmentation of the rope access spillway and rock abutment, as well as the condition of the concrete arch and foundation. 

During a two-hour drone flight, more than 80 million data points (x, y and z coordinates) were collected for the arch dam, spillways and rock abutments, and a composite 3D model was created. The drone also captured high definition photos, documenting the current condition of structures to provide a baseline for future observations. Using data collected, we developed a high resolution virtual model of the dam to identify surficial cracks. Artificial Intelligence is being developed to “learn” how to reliably identify areas of concrete that are cracked or spalled — differentiating between shadows, discolorations and algae/moss growth as well as concrete deterioration. 

By keeping hydroelectric generators and dams up to date, we’re helping SCL produce reliable power around the clock now and into the future.  

Diablo Dam Aerial