Alto Tunnel Fact Sheet

Update: The Marin County Board of Supervisors allocated $250,000 in Pilot Program funds for a Mill Valley – Corte Madera Gap Closure study which will evaluate the Alto Tunnel, Horse Hill route, and Camino Alto. The RFP for the study is expected to be released in summer 2008.

For more information, email deb@marinbike.org

• Where is the Alto Tunnel and what is its history?
• Some say that Alto Tunnel is curved, and there would be no light at the end of the tunnel. Is that true?
• Why would the County of Marin want to restore Alto Tunnel?
• What have been the experiences when other bicycle and pedestrian tunnels have been opened throughout the United States?
• What is the condition of the Alto Tunnel today?
• How much would it cost to re-open the Alto Tunnel and make it a part of the North-South Bikeway?
• Where would the money come from to open the Alto Tunnel?
• Would funds to open Alto Tunnel take away from schools, parks, emergency services, or other projects?
• How many people are projected to use the Alto Tunnel on a daily basis?
• How would security and maintenance be handled?
• How will opening Alto Tunnel affect the neighbors?
• Are there any environmental considerations?
• Emergency egress benefits of Alto Tunnel
• What else is happening with plans to construct the North-South Bikeway from Sausalito to Sonoma?

Where is the Alto Tunnel and what is its history?

The Alto Tunnel was built in 1884 and is located in Marin County along the former Northwestern Pacific Railroad right-of-way. The tunnel is 16-feet wide and 20-feet high and served as a single-track rail tunnel for nearly ninety years, connecting Corte Madera and Mill Valley. In 1958, there was a substantial upgrade to the northern portal, which remains intact and in good condition today. The tunnel remained open until 1971, when substantial bulkheads were added at each portal to prevent entry. In 1975, a plug extending approximately 125-feet was added near the north end of the tunnel and in 1981, there was a collapse at the southern portal. The southern portal area was stabilized in 1982 with gravel and earth fill, which remains today. The middle 1600-feet of the tunnel remains sealed off from both ends today and likely has the original redwood timber support system in place.

Some say that Alto Tunnel is curved, and there would be no light at the end of the tunnel. Is that true?

While the historical railroad tunnel had a slight bend at the south portal, this would be altered when the tunnel is reconstructed. Because the 400 feet at the south portal is collapsed, and the hillside in that region is shallow, when the tunnel is rebuilt, engineers would move the southern portal 100 feet or more to the north, effectively removing the bend in the tunnel. Thus, one would be able to see "the light at the end of the tunnel".

Why would the County of Marin want to restore Alto Tunnel?

The County of Marin owns the property on either side of the tunnel, and the railroad right-of-way has always been slated for use as a transportation corridor. Since the 1970s, the County has had plans for a North-South Bikeway which would run along the Northwestern Pacific Railroad right-of-way, spanning Marin County from North to South, providing access to transit centers, businesses, schools, and town centers. There is currently a well-used multi-use pathway that extends for three miles, from Sausalito and through Mill Valley, leading right up to the south portal of Alto Tunnel. Another pathway continues north from the north portal of Alto Tunnel, through Corte Madera and Larkspur, approaching the Larkspur trestle. Here are some benefits of "closing the gap" in the North-South Bikeway through opening the Alto Tunnel for bicycle and pedestrian use:

1) Improved Safety: Currently, bicyclists and pedestrians have two choices for traveling between Mill Valley and Corte Madera, neither of which are appealing. They can go out of their way to the "Horse Hill" (Alto Hill)/Highway 101 Freeway path (which includes 200 total feet of climbing and carbon monoxide fumes from the freeway traffic), or travel over Camino Alto, which is a 320 foot climb along a busy, narrow, winding road. Police statistics from Corte Madera indicate that there have been numerous injuries and two deaths of non-motorized users along Camino Alto over the past ten years.

2) Decreased Traffic Congestion: Opening Alto Tunnel would create a straight, flat pathway that would be accessible to people of all ages and physical abilities. People would be able to commute to San Francisco, access the Manzanita Transit station, shop at businesses on either side of the hill, attend soccer practice and other after-school activities, go to the new Mill Valley community center and the pool, and to commute to the College of Marin. Many auto trips could easily be replaced with bicycle or pedestrian trips once the tunnel is open. The Metropolitan Transportation Commission for the Bay Area estimates that traffic congestion will increase 249% in the San Francisco Bay Area over the next 20 years, opening Alto Tunnel would help to reduce traffic congestion in Marin County.

3) A Route for People in Wheelchairs: Opening the Alto Tunnel would provide a socially- equitable transportation option for persons in wheelchairs. People-powered or electric wheelchairs would allow members of the disabled community to transport themselves, without relying on other people or automobiles for transportation.

4) Emergency Vehicle Access: Everyone living in Marin has experienced the nightmare of traffic congestion on Highway 101. While this is stressful for most, it can be a matter of life or death for some. Ambulances traveling from southern Marin to Marin General Hospital during the afternoon rush hour currently have no way to avoid the traffic nightmare on Highway 101. If the Alto Tunnel were opened, emergency vehicles could use this route, saving lives. In the event of a major disaster, the tunnel would provide a critical secondary route to transport the injured to hospitals, and supplies to where they are needed. Tunnels perform well in earthquakes, and the Alto tunnel is not located along any major faults.

5) Personal Health Benefits: Opening the Alto Tunnel would enable people to have a safe, flat route for walking and biking, thus increasing exercise options in the Mill Valley/Corte Madera region. The U.S. Centers for Disease Control and Prevention estimate that 300,000 Americans die each year due to complications associated with obesity and sedentary lifestyles. The CDC recommends 30 minutes of physical exercise, five times a week, for adults and states that replacing trips by automobile with walking or cycling is one of the best ways the get this exercise.

6) Environmental Health Benefits: The useful route provided by the tunnel will replace motor-vehicle trips, reducing air and water pollution.

7) National Security Benefits: Fewer motor-vehicle trips means a stronger country in many ways.

8) Physically and Fiscally Responsible: Bicycling is the most efficient form of personal transport known. This project is about reduction of waste. Bicycling for transportation saves us all money.

What have been the experiences when other bicycle and pedestrian tunnels have been opened throughout the United States?

In the Fall of 2000, the County of Marin commissioned the Rails-to-Trails Conservancy to do a study of tunnels which have been opened throughout the United States for use by bicyclists and pedestrians. The report, released in June of 2001, is titled "Tunnels on Trails, A Study of 78 Tunnels on 36 Trails in the United States". The report covers issues related to: safety, liability, costs of tunnel restoration, construction, maintenance, and the impacts of tunnels on the existing transportation network and surrounding communities. The report concludes that tunnels are overwhelmingly safe, that they are valued by communities, and that there is a trend throughout the United States to open more tunnels to non-motorized use. The most serious crime reported at any of the 78 tunnels was an attempted purse snatching, where the purse was recovered due to security cameras. The study also found that property values often increased, and that while all neighborhoods had concerns before the tunnels were opened, some of the most vocal opponents of the tunnels came to be the most frequent users and supporters of the tunnels once they were opened. You can find the RTC study on-line in PDF format at: http://www.railtrails.org/whatwedo/information/tot.asp

What is the condition of the Alto Tunnel today?

The northern 170-feet was inspected in June, 2001 and determined to be in good structural condition. The exact condition of the middle 1600-feet of the tunnel is unknown at this time; however, further investigations are being proposed to better determine the condition in this zone. The existing redwood timbers may be in various stages of decay, depending on the amount of moisture in the sealed portion of the tunnel. Regardless of the existing conditions, the existing redwood timber support system will have to be replaced and augmented with a new concrete liner for both structural safety, aesthetics, and to eliminate any fire danger. The Southern 350-feet was backfilled with gravel in 1982 and will have to be excavated and supported with a new concrete structure.

How much would it cost to re-open the Alto Tunnel and make it a part of the North-South Bikeway?

No one knows exactly how much it would cost to re-open the Alto Tunnel, which is one reason that the County of Marin’s Mill Valley – Corte Madera Gap Closure study (which should start in 2008) is so important. The study will analyze all possible alternatives for bicycle/pedestrian traffic flows between Mill Valley and Corte Madera. The study will also allow us to learn more about the condition of the tunnel, thus allowing for a more accurate cost estimate. In a worst case scenario, if the tunnel were significantly collapsed, it could still be re-opened, and it would cost less than boring a new tunnel.

Where would the money come from to open the Alto Tunnel?

There are several possible funding sources, which could be used to open Alto Tunnel. The funding from the tunnel may come from one or a variety of the following sources:

1) Bicycle Transportation Grants: Approximately, every 5 years, the federal government authorizes a transportation expenditure bill which funds nearly all types of capital expenditure projects for land transportation. Some components of this bill fund large bicycle and pedestrian projects. After a feasibility study is completed on the Alto tunnel, the County could also choose to apply for grants to open the Alto Tunnel. Generally, federal grants require an 11.5% local match. The State of California also has a Bicycle Transportation Account.

2) Demonstration Projects: Congress often appropriates funds for "demonstration projects" that help to relieve traffic congestion. The Marin County Board of Supervisors have passed a resolution declaring that they would like to make Marin County a model bicycle and pedestrian community for the Nation. The pursuit of a Congressional appropriation could result in the funds to open Alto Tunnel.

3) Private Fundraising: Appeals to individuals, businesses, and foundations could also play a role in helping to fund the opening of Alto Tunnel. These types of funds could help to secure the local match needed to leverage large federal and state grants.

Would funds to open Alto Tunnel take away from schools, parks, emergency services, or other projects?

No. The funds that would be used to open the Alto Tunnel would be transportation project funds; they would not take away from schools, parks, emergency services, etc. In addition, most of the sources of funds stated above could not be used for small bicycle and pedestrian projects - only for large capital projects related to bicycle and pedestrian use. When assessing the costs for Alto Tunnel, it is important to also look at the costs for other transportation projects. The HOV gap closure project which will add one traffic lane and a reversible barrier along Highway 101 for 4 1/2 miles from Terra Linda to Larkspur is costing the County $150 million. It will cost $800 million to widen the Highway one lane in each direction from Novato to Petaluma.

How many people are projected to use the Alto Tunnel on a daily basis?

The March 2008 Marin County Bicycle and Pedestrian Master Plan indicates that the tunnel would essentially provide a level, separated connection from Sausalito to Corte Madera, Larkspur the upper Ross Valley, and central San Rafael. Preliminary 2001 estimates indicate that the tunnel alone could attract an additional 800 bicyclists during a typical weekday, many of whom were driving previously. This is approximately 33 bicyclists per hour, based on a 24 hour time line, or 50 bicyclists per hour if the concentration of use takes place between 7 AM and 10 PM.

How would security and maintenance be handled?

Once the Alto Tunnel is re-opened, there will be annual costs to maintain and operate this facility. Some security measures that have been used in other tunnels include: security cameras, police patrols, and lighting. These are likely the types of features that we would see if Alto Tunnel were re-opened.

The Rails-to-Trails Conservancy Tunnel Study found that all liability costs were covered in other tunnels under normal insurance policies for trails. Most tunnel maintenance costs were also covered through regular maintenance of the trail, thus the tunnel did not create a significant extra financial burden. For those tunnels that did accrue an extra cost, the average cost to maintain a tunnel was determined to be $2,305 per month.

Because the portals to Alto Tunnel enter and exit in Mill Valley and Corte Madera, a cooperation and coordination among the towns would be essential. It is likely that the towns would form a joint powers agreement to cover maintenance and operations, as well as use of the tunnel by emergency vehicles.

How will opening Alto Tunnel affect the neighbors?

Some neighbors that live near Alto Tunnel have stated that they do not want the tunnel to be re-opened. They state that they do not want the tunnel to change the character of their neighborhood. While satisfying neighbors is important, it is also necessary to recognize that there are many ways to minimize any possible negative impacts that an open the tunnel may have. Signs can be posted urging tunnel users to please be quiet and respect the neighbors. Landscaping can create a visual barrier to the pathway, and sound mitigation can help to reduce any errant noise. In addition, as with any transportation or development project, neighbors concerns must be weighed against the benefits of the project. Furthermore, the Northwestern Pacific Railroad right-of-way is a transportation right-of-way which was used by trains for almost 90 years; it has been intended for use as a transportation corridor in the future.

Are there any environmental considerations?

Any transportation project has "environmental impacts". The project would need to go through review under CEQA, the California Environmental Quality Act. If the County of Marin were to determine that they were ready to move forward with opening the Alto Tunnel, the appropriate departments within the County of Marin would determine the type of environmental review necessary. Because this project is a "replacement or reconstruction of existing structures or facilities" it has a different status of review than an entirely new transportation project.

In addition, it seems that the overall environmental impacts of the Alto Tunnel would be greatly beneficial to Marin County. People's health would benefit from increased walking/jogging/cycling, and environmental benefits would be accrued from motor vehicle trip reduction. The existence of a flat, straight, car-free route would attract people who might walk or bicycle today, but are dissuaded due to the hills and automobile traffic they would have to contend with.

Emergency egress benefits of Alto Tunnel

There has been much attention placed on the slogan “Get Ready Marin” which urges residents to be prepared in the event of a disaster. Many Alto Tunnel proponents comment on how the tunnel would provide an important emergency egress should there be a fire. The Alto Tunnel would provide a quick and level route for people and their families to easily leave a hazardous fire.

What else is happening with plans to construct the North-South Bikeway from Sausalito to Sonoma?

A lot! Here is a link to our recent North South Greenway update.  One key strategy is the development of a continuous North-South Bikeway, and the Alto Tunnel is the cornerstone of this plan.

Last updated April 2008