List of tunnels in Seattle

This is a list of tunnels built in the city of Seattle, in the U.S. state of Washington.

The Puget Sound region, where Seattle lies, has a history of glaciation that has left many hills and ridges that civil engineers have needed to traverse for transportation and utilities.[1] Some of these tunnels are part of megaprojects.

## Tunnels

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Year(s) Constructed | Tunnel | Diameter | Length | Notes | References

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1894  | Lake Union Sewer Tunnel  | 72 in (1.8 m) | 5,736 ft (1,748 m)  | Hand excavated  | [1]
1894  | South Bayview Street Tunnel  | 4 ft (1.2 m) x 6 ft (1.8 m) | 4,526 ft (1,380 m)  | Hand excavated  | [1]
1903–1905  | Great Northern Tunnel | 38 ft (12 m) | 5,141 ft (1,567 m)  | Hand excavated  | [1]
1907  | Oregon and Washington Railroad Tunnel  | 38 ft (12 m) | 900 ft (270 m)  | Hand excavated; never completed (filled in 1922)  | [1]
1910  | First Avenue Utilidor Tunnel  | 8 ft (2.4 m) | 300 ft (91 m)  | Compressed air, hand  | [1]
1910  | 4th and Connecticut Ave. Sewer  | 3–6 ft (0.91–1.83 m) | 7,060 ft (2,150 m)  | Supported trench  | [1]
1910  | Ravenna Sewer Tunnel  | 80 in (2.0 m)
Relined 66 in (1.7 m)  | 2,875 ft (876 m)  | Hand; tried tunnel boring machine | [1]
Early 1900s | Wallingford Tunnel  | 9 ft (2.7 m) | 1,803 ft (550 m)  | Open cut and tunnel  | [1]
Early 1900s | Pacific Street Tunnel  | 9 ft (2.7 m) | 11,325 ft (3,452 m)  | Open cut and tunnel  | [1]
1910  | Lander Street Sewer  | 4.5–9 ft (1.4–2.7 m)  | 5,290 ft (1,610 m)  | Supported trench  | [1]
1911  | Fort Lawton Tunnel  | 10 ft (3.0 m) | 9,720 ft (2,960 m)  | Hand dug  | [1]
1911  | Montlake Siphon Tunnel  | 4 ft (1.2 m) | 2,005 ft (611 m)  | Hand dug  | [1]
1912  | Dexter and 8th Avenue Tunnel  | 5 ft (1.5 m) | 9,315 ft (2,839 m)  | Hand dug  | [1]
1912  | Washington Park Tunnels  | 5 ft (1.5 m) | 4,052 ft (1,235 m)  | Hand dug  | [1]
1913  | Third Avenue West Siphon Tunnel  | 21 ft (6.4 m) | 500 ft (150 m)  | Hand dug  | [1]
1926  | Jackson Street Drainage Tunnel | 4 ft × 6 ft (1.2 m × 1.8 m) | 1,500 feet (460 m)  | Hand dug
35 psi compressed air  | [1]
1930  | South Hanford Street Tunnel  | 9 ft (2.7 m) | 6,055 ft (1,846 m)  | Hand dug  | [1]
1931  | Charleston Street Tunnel  | 3.5 ft (1.1 m) | 2,830 ft (860 m)  |  | [1]
1936  | Henderson Trunk Sewer Tunnel  | 60 in (1.5 m) (I.D., concrete)
48 in (1.2 m) (brick)  | 3,000 ft (910 m)  | Hand dug
Concrete and brick  | [1]
1936  | Laurelhurst Trunk Sewer Tunnel  | 9 ft (2.7 m) | 1,850 ft (560 m)  |  | [1]
1938–1941  | Mount Baker Tunnel | 28 ft × 23 ft (8.5 m × 7.0 m) | 1,330 ft (410 m)  |  | [1]
1934–1942  | WPA slide control drainage projects  | 4 ft × 6 ft (1.2 m × 1.8 m) | 4,926 ft (1,501 m)  |  | [1]
1952–1954  | Battery Street Tunnel |  | 3,140 ft (960 m)  | Originally named Battery Street Subway  | [2][3]
1963  | Montlake Siphon Tunnel replacements  | 42 in × 108 in (1.1 m × 2.7 m) | 586 ft (179 m)  |  | [1]
1965–1966  | Elliott Bay Interceptor section 6 tunnel  | 8 ft × 12.5 ft (2.4 m × 3.8 m) | 1,750 feet (530 m)  | Tunnelling shield | [1]
1964–1967  | Lake City Sewer Tunnel  | 8 ft × 11 ft (2.4 m × 3.4 m) | 17,570 feet (5,360 m)  | Close-face wheel excavator | [1]
1967–1968  | Second Avenue Sewer Tunnel  | 8.5 ft × 12.5 ft (2.6 m × 3.8 m) | 19,900 feet (6,100 m)  | Tunnelling shield | [1]
1960s to present  | University of Washington utilidors | Various, 5–10 ft (1.5–3.0 m) | 50,000 feet (15,000 m) total  |  | [1][4]
1975  | Northwest Kidney Center pedestrian tunnel  | 10 ft (3.0 m) horseshoe  | 120 ft (37 m)  | Bobcat loader | [1]
1983–1986  | Mount Baker Tunnel expansion  | 65 ft (20 m) | 1,330 ft (410 m)  | Tunnelling shield
World's largest diameter soil tunnel  | [1]
1984  | Seattle Public Utilities Beacon Hill Waterline/Cedar River Pipeline  | 12 ft (3.7 m) | 150 ft (46 m)  |  | [1]
1985  | Columbia Center pedestrian tunnel  | 14 ft (4.3 m) horseshoe  | 280 ft (85 m)  |  | [1]
1985  | Virginia Mason Hospital pedestrian tunnel  | 10 ft (3.0 m) horseshoe | 120 ft (37 m)  | Bobcat loader | [1]
1986  | Renton Sewer Tunnel ETS-4A  | 12 ft (3.7 m) O.D. | 2,403 ft (732 m)  | Drill and shoot  | [1]
1986  | Renton Sewer Tunnel ETS-4B  | 12 ft (3.7 m) O.D. | 620 ft (190 m)  | Drill and shoot  | [1]
1986  | Renton Sewer Tunnel ETS-5  | 12 ft (3.7 m) O.D. | 1,820 ft (550 m)  | Drill and shoot  | [1]
1986  | Renton Sewer Tunnel ETS-6  | 12 ft (3.7 m) O.D. | 1,056 ft (322 m)  | First use of Earth Pressure Balance Machine in Seattle  | [1]
1987–1988  | Downtown Seattle Transit Tunnel | Twin 21.25 ft (6.48 m) | 13,624 ft (4,153 m)  | Tunnelling shield
First use of waterproofing PVC membrane in USA  | [1]
1990  | Fort Lawton Tunnel/West Point Sewer  | 15.5 ft (4.7 m) O.D. | 8,400 feet (2,600 m)  | Partial Earth Pressure Balance Machine | [1][5]
1993  | Royal Brougham Street Sewer Tunnel  | 10 ft (3.0 m) O.D. | 300 ft (91 m)  |  | [1]
1993  | Lake Washington Canal Tunnel  | 3.3 ft (1.0 m) | 1,518 ft (463 m)  | First slurry microtunnel in Seattle  | [1]
1995  | Lander Street Sewer Tunnel  | 10 ft (3.0 m) O.D. | 130 ft (40 m)  |  | [1]
1995  | First Avenue Utilidor Tunnel  | 10 ft (3.0 m) | 500 ft (150 m)  | Microtunnel | [1]
1995–1997  | West Seattle Sewer Tunnel  | 13 ft (4.0 m) | 10,500 feet (3,200 m)  | Partial Earth Pressure Balance Machine
Maximum 400 feet (120 m) below surface  | [1][5]
1997  | Eastlake Storm Sewer Tunnel  | 3.5 ft (1.1 m) | 475 ft (145 m)  | Slurry microtunnel | [1]
2001  | Justice Center Tunnel  | 15 ft (4.6 m) horseshoe | 200 ft (61 m)  |  | [1]
2002  | Denny CSO Storage Tunnel  | 16.8 ft (5.1 m) O.D. | 6,212 ft (1,893 m)  | First complete Earth Pressure Balance Machine tunnel in Seattle  | [1][5][6]
2002  | Henderson CSO Storage Tunnel  | 16.8 ft (5.1 m) O.D. | 3,105 ft (946 m)  | Earth Pressure Balance Machine, connecting microtunnels | [1][5]
2006  | Beacon Hill tunnel | Twin 20 ft (6.1 m) | 1 mi (1.6 km) | Tunnel boring machine | [7]
2009–2012  | University Link Tunnel | Twin 20 ft (6.1 m) | 3 mi (4.8 km) | Tunnel boring machine
$1.9 billion megaproject | [8][9]
2007–2011  | Brightwater Sewage Tunnel | 17.5 ft (5.3 m) | 13 mi (21 km) | Four tunnel boring machines
Maximum depth 400 feet (120 m)
Part of $1.8 billion megaproject | [5][10][11][12]
2013–2018  | Alaskan Way Viaduct replacement tunnel | 57 feet (17 m) | 2 mi (3.2 km) | $4.25 billion megaproject
World's largest tunnel boring machine, 57.5 feet (17.5 m) in diameter  | [13]
2014–2016  | Northgate Link tunnel | Twin 20 ft (6.1 m) | 3.4 mi (5.5 km) | Tunnel boring machine
$2.1 billion megaproject | [14]
2019–  | King County Ship Canal Water Quality Project  | 21.67 ft (6.61 m) and 8 ft (2.4 m) | 2.7 mi (4.3 km) | Largest tunnel boring machine named "Mudhoney" to construct combined sewer outflow storage tunnel under EPA consent decree. Two smaller machines for conveyance tunnels.  | [15][16]

## See also

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* List of tunnels in the United States

## Further reading

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* Lynda V. Mapes (December 10, 2011), "Tunnels: Seattle's boring past filled with thrills", Pacific Northwest magazine, The Seattle Times, retrieved December 16, 2012

## References

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1. ^ a b c d e f g h i j k l m n o p q r s t u v w x y z aa ab ac ad ae af ag ah ai aj ak al am an ao ap aq ar as at au av Robinson, Robert A.; Cox, Edward; Dirks, Martin (2002), Tunneling in Seattle: A History of Innovation, North American Tunnelling Conference, Seattle, Wash., archived from the original on April 6, 2010, retrieved December 16, 2012
2. ^ Bridges and roadway structures, Seattle Department of Transportation, retrieved December 17, 2012
3. ^ Phil Dougherty (April 1, 2007), "Final phase of Seattle's Alaskan Way Viaduct opens to traffic on September 3, 1959", HistoryLink, Seattle: History Ink
4. ^ Jenny Hansson (September 27, 1995), "The freedom to have a tunnel map", UW Daily, retrieved December 16, 2012
5. ^ a b c d e 2010 Brightwater Project Progress and Tunneling Status (PDF), King County Waste Treatment Division
6. ^ Featured Project: Denny Way CSO Control Project, American Underground Construction Association, retrieved December 16, 2012
7. ^ Mike Lindblom (April 21, 2006), Beacon Hill tunneling a breeze, The Seattle Times
8. ^ Scott Gutierrez (May 15, 2012), Light rail tunnels now link downtown to Capitol Hill, UW, Seattle Post-Intelligencer
9. ^ "University Link Extension". Sound Transit. Archived from the original on October 14, 2012. Retrieved December 15, 2012.
10. ^ Jack Broom (September 8, 2009). "2 tunneling machines on Brightwater sewer project are damaged — and 300 feet deep". The Seattle Times. Retrieved December 15, 2012.
11. ^ Scott Gutierez (August 17, 2011). "Brightwater tunneling completed this week". Seattle P-I. Retrieved December 15, 2012.
12. ^ Jeff Switzer (September 25, 2007), "Machine moves 100 trucks of dirt a day", Everett Herald
13. ^ Alaskan Way Viaduct replacement program: Tunneling, Washington State Department of Transportation, retrieved December 17, 2012
14. ^ "Sound Transit contractor completes mining last tunnel segment for Northgate Link Extension" (Press release). Sound Transit. September 2, 2016. Retrieved September 10, 2016.
15. ^ Tim Newcomb (April 19, 2021), "Seattle's Latest Tunnel Boring Machine Will Dig 2.7 Miles", Engineering News-Record
16. ^ "Meet our tunnel boring machines". Ship Canal Water Quality Project. Retrieved March 3, 2022.

* v
* t
* e

Bridges and tunnels in and around Seattle

* List of bridges in Seattle
* List of tunnels in Seattle

Bridges|

| Road|

* Alaskan Way Viaduct
* Ballard Bridge
* Cowen Park Bridge
* East Channel Bridge
* Evergreen Point Floating Bridge (1963)
* Evergreen Point Floating Bridge (2016)
* First Avenue South Bridge
* Fremont Bridge
* George Washington Memorial Bridge (Aurora Bridge)
* Homer M. Hadley Memorial Bridge
* Jose Rizal Bridge
* Lacey V. Murrow Memorial Bridge
* Magnolia Bridge
* Montlake Bridge
* North Queen Anne Drive Bridge
* Schmitz Park Bridge
* Ship Canal Bridge
* South Park Bridge
* Spokane Street Bridge
* 20th Avenue NE Bridge
* University Bridge
* West Seattle Bridge
* West Spokane Street Bridge

|

Rail|

* Salmon Bay Bridge
* Wilburton Trestle

Tunnels|

| Road|

* State Route 99 Tunnel
* Aubrey Davis Park (Mercer Island Lid)
* Battery Street Tunnel
* Convention Center-Freeway Park Lid
* Mount Baker Tunnel

|

Rail|

* Beacon Hill Tunnel
* Downtown Seattle Transit Tunnel
* Great Northern Tunnel
* Northgate Link tunnel
* University Link tunnel

Utility|

* Brightwater sewage tunnel

Italics denote former bridges and tunnels.
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