FACT SHEET - Lake Washington Ship Canal

Published April 13, 2018


Connecting Commerce


The U.S. Army Corps of Engineers began construction of the Lake Washington Ship Canal and Hiram M. Chittenden Locks in 1911. They were dedicated on July 4, 1917. The 30-foot-deep canal connects Puget Sound on the west with Lake Washington eight miles to the east. A dam, gated spillway, fish ladder, gardens, visitors’ center and two navigation locks are located 1.5 miles east of the entrance on Puget Sound. The locks and canal materially contribute to the industrial, municipal, commercial, environmental and recreational development of the area while serving multiple functions: (1) Controlling the elevation of Lake Washington within a narrow range allows for east-west highway traffic across two floating bridges, Interstate 90 and Washington State Highway 520, which are key to commerce for Ports of Seattle and Tacoma. (2) This is the busiest navigation lock in the nation. The Alaska fishing fleet is home ported in Lake Union. The canal and locks provide a navigation link from freshwater Lake Washington and Lake Union to saltwater Puget Sound. (3) The fish ladder and locks are the only connection for salmon moving from Puget Sound to freshwater Lake Washington and its 607-square-mile watershed. (4) The Locks is a popular destination in Seattle and receives more than 1 million visitors per year.

The Locks marks its centennial in 2017. A Probability Failure Mode Analysis, a 2012 Periodic Inspection and Periodic Assessment and a 2013 Operational Condition Assessment highlighted the poor and sometimes failed condition of many critical lock and dam components. A prioritized list of multiple major maintenance projects, as well as numerous minor maintenance projects need to be accomplished to ensure the facility continues its mission into the future. The replacement of the radial spillway gates was completed in fiscal 2014. The next priority is the dewatering pump plant which experienced two pipe failures; construction will be completed this summer. A similarly high priority is replacement of the original 1916 stoney gate filling culvert valves, for which design was recently completed. In November 2013, there was a failure of the 1923 derrick crane that is part of the Emergency Closure System for the large lock chamber. This crane will need to be replaced to reduce risk of pool loss, protecting $10 billion in floating bridge infrastructure, including I-90. Based on recent Endangered Species Act biological opinions, repairs to the saltwater drain to address the problem of adult salmon becoming trapped in the fish ladder's diffuser well are being evaluated for future action. The temporary Adult Salmon Exclusion Structure continues to function effectively, but it is reaching the end of its design life and needs a permanent solution to avoid take of ESA fish.



The River and Harbor Act of 1890 authorized a survey to select the most feasible location to construct a ship canal and give an estimate of expense. Construction, Operations and Maintenance of Lake Washington Ship Canal with a double lock was authorized in the River and Harbor Act of 1910. Recreation facilities were authorized in 1944 (Public Law 78-534).


Infrastructure Projects


Projects are prioritized by need, safety, and/or requirement to meet the mission


  • Monolith Scour Repair - COMPLETE

  • Spillway Radial Gate Replacement  – COMPLETE

  • Pumping Plant Replacement  - ~$6M – will complete in FY17


  1. Large Lock Emergency Closure System Rehabilitation (Crane Replacement) - $4M-$8M. Design is complete. Likely in 2017 or 2018 budget for replacement.
  2. Filling Culvert Valve and Machinery Replacement (Stoney Gate valves) – Construction funding needed $5M - $12M. Design recently completed.
  3. Large Lock Gate Rehabilitation – currently condition unknown. Estimate ~$6M - $10M. Need inspection and design.
  4. Emergency Generator Connections. (Seismic retrofit of transformer house is cost prohibitive) Less than $1M
  5. Saltwater Drain Intake System and Permanent Solution to Diffuser Well. Large unknowns – plan and design needed. Likely a new temporary screen installed in 5 years for $500K to $2M. Complete drain replacement could be $5M to $10M.
  6. Emergency Closure for Small Lock. Unknown – design needed. Estimate $1M - $5M.
  7. Electrical System Rehabilitation. Estimate $7M based on previous costs.
  8. Small Lock Machinery Replacement. Unknown – design needed. Estimate $3M to $5M. 
  9. Saltwater barrier Replacement. Unknown – design needed. Estimate $1M - $2M
  10. Maintenance Building Rehabilitation. Unknown – inspection and design needed.


Project Costs


Original Construction $3,831,781


O&M, Costs FY16 Appropriation $12,097,000


O&M, FY17 President's Budget $12,325,000