Sunset Tunnel
| Company type | Infrastructure |
|---|---|
| Industry | Public transportation |
| Founded | 1928 |
| Headquarters | San Francisco , United States |
| Products | Light rail and streetcar passageway |
The Sunset Tunnel, initially known as the Duboce Tunnel, is a dedicated light rail and streetcar passageway located in San Francisco, California. It lies beneath the hill adjacent to Buena Vista Park and serves solely the N Judah route of the Muni Metro system.
Its eastern entrance is situated at the intersection of Duboce and Noe streets by Duboce Park within the Duboce Triangle, San Francisco, while the western entrance opens into Richard Gamble Memorial Park near Carl and Cole streets in the Cole Valley, San Francisco area.
Early Proposals
In March 1913, engineer Bion J. Arnold introduced a concept for a Mission–Sunset Tunnel in his transportation improvement report for San Francisco. This proposed tunnel would commence near Eureka Valley station, acting as a conduit for rail, road vehicles, and pedestrian traffic from the Panhandle region to a future Market Street subway. Its purpose was to enhance transit connections to the Sunset District from areas south of Market Street by providing a more direct alternative to existing indirect routes.
Arnold's design featured a dual-level tunnel: an upper level for vehicles and pedestrians above a two-track rail tunnel below, with lengths varying between 3,720 and 4,720 feet depending on the chosen alignment.
| Plan No. 1 | Plan No. 2 | Plan No. 3 | |
|---|---|---|---|
| Carl & Cole | Frederick & Cole | ||
| 16th & Noe | 17th & Castro | "Market & Eureka (extension)" | |
| 4,720[convert: needs unit name] | 4,400[convert: needs unit name] | 3,720[convert: needs unit name] | |
Progress on constructing a tunnel to serve the Sunset District was postponed until after completion of the Twin Peaks Tunnel, which opened in June 1918. By July 1918, an alignment along Duboce Avenue was proposed for the Sunset Tunnel.
Following an appropriation of $500,000 in September 1921, City Engineer M.M. O'Shaughnessy evaluated four potential routes: two surface options, Arnold's original 1913 plan from Eureka Valley station, and the Duboce Avenue alignment suggested in 1918. He recommended the Duboce route, which received approval from the Board of Supervisors on May 31, 1922. This decision established a special assessment district despite some opposition favoring surface alternatives. Residents of the Sunset District largely backed the more direct Duboce route.
Construction and Inauguration
Funding for exploratory test borings was secured in June 1922, with detailed engineering plans and cost estimates submitted by September of that year. The tunnel was designed to extend approximately 4,233 feet with an estimated expenditure near $900,000. After considerable political discussion, the final alignment received formal approval on April 6, 1925.
The construction contract was awarded on May 10, 1926, to Youdall Construction Company following their low bid of $687,572. Groundbreaking occurred on June 10, 1926. Including its approaches, the Sunset Tunnel stretched roughly 4,233 feet with a consistent grade of 3%, a width of 21 feet, and vertical clearance of 15 feet above the tracks. The approaches measured about 1,000 feet combined. Excavation primarily proceeded through serpentine rock formations using three drifts: one pilot drift at the crown and two sidewall drifts. The pilot drift was completed in less than twelve months by March 11, 1927. Overall construction concluded on February 4, 1928, with total costs amounting to $890,000.
After nearing completion, a contract for track installation was awarded; however, work was delayed due to an injunction lasting from October 1927 until May 1928. The tunnel officially commenced revenue operations on October 21, 1928, during an opening ceremony officiated by Mayor James Rolph. The newly established "N" line rapidly became second in gross revenue among streetcar services. Both the Twin Peaks and Sunset tunnels played crucial roles in accelerating development within the Sunset District—especially facilitating residential projects by developer Henry Doelger throughout the 1930s and 1940s.
Intrusion
Entry to the tunnel is exclusively permitted for San Francisco Municipal Railway light rail vehicles. Nonetheless, the tunnel has experienced incidents of vandalism, theft of copper wiring, and graffiti defacement. Unauthorized vehicles have occasionally gained access, with four such occurrences documented in February 2017 alone.
Trackway Improvement Project
The Sunset Tunnel Trackway Improvement Project encompassed track replacement and significant infrastructure upgrades, including installation of a new overhead contact system, refurbishment of fire sprinkler valves, seismic retrofitting, and reconstruction of platforms at the 28th Avenue stop. The initiative began in November 2014 and was initially planned to conclude by June 2015; however, it extended until October 2017 due to unforeseen additional repairs discovered during construction and community resistance to nighttime work permits. During weekend closures of the tunnel, N Judah trains were short-turned at Church & Duboce, with bus shuttles providing service to Ocean Beach. The overall project cost increased by $4 million, reaching a total of $23.3 million.
External links
- Tentative Plan, Buena Vista Station, Sunset Tunnel, Duboce Avenue Route (1926), City and County of San Francisco, Department of Public Works, Bureau of Engineering
- Sunset Tunnel a Reality, Walter Gaines Swanson, The Municipal Employee, October 1928
- Judah's Prius – Video showing N Judah train towing Toyota Prius out of Sunset Tunnel