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The Bay Trail Circles San Francisco Bay Area

Bay Trail Makes Waves for Public Shoreline Access: 9 Counties, 47 Cities, 500 miles.

From the Association of Bay Area Governments

Map of Virginia


While sitting at a restaurant on the City of San Leandro, California shoreline twenty years ago, then state senator Bill Lockyer mused on the topic of public access and the San Francisco Bay. What if there were a pathway around the entire San Francisco Bay, linking neighborhoods, schools, transit, job centers and recreation facilities to the shoreline? Within the prior decade, the steady decline of the San Francisco Bay shoreline had been halted by the "Save the Bay" movement, and Bay Area residents were slowly awakening to a shoreline renaissance. This reawakening combined with Senator Lockyer's musings lead to the introduction of Senate Bill 100 which called for the planning and implementation of a continuous recreational corridor around the entire San Francisco Bay— the Bay Trail.

Photo of trail under Golden Gate Bridge
Crissy Field under the Bolden Gate Bridge

Today, that "back of the envelope" idea has been formally adopted by each of the nine Bay Area counties and 47 cities the Bay Trail passes through, and regional coordination efforts are staffed by four full-time employees. When fully built-out, this visionary trail corridor will be approximately 500-miles long. The trail will pass through myriad terrains ranging from extremely remote wetland areas where shorebirds outnumber hikers and bikers in the North Bay, to the Embarcadero promenade in San Francisco with several thousand users per day. The alignment will cross seven toll bridges, offer access to commercial areas, points of historic, natural and cultural interest, and over 130 parks and wildlife preserves. The ultimate goal is for the entire alignment to be a fully separated pathway that is accessible to pedestrians, cyclists, rollerbladers, and wheelchair riders.

Map of Bay Area

Bay Trail map (view a large map - 480 kb)


Currently more than 50% complete, the Bay Trail passes through incredibly diverse landscapes on its trek from wine country in Sonoma and Napa Counties to the heart of Silicon Valley in the southern Santa Clara and San Mateo Counties. Two of the most challenging aspects of trail development in the San Francisco Bay region are wetland and habitat issues, and existing industrial and port/airport related uses. Among the shoreline uses that essentially preclude public access are two international airports, four active seaports, one NASA research center, and seven military installations in various stages of conversion. While Bay Trail planners continue to actively pursue an alignment as close as possible to the water, in areas such as these, the trail may move to inland routes and provide point access ("spur trails") to the waterfront where possible.

Wildlife and Public Access

Developing public access trails that offer a spectacular shoreline experience without impacting wildlife is central to the Bay Trail's mission. However, building a shoreline trail while protecting wildlife, sensitive habitat, and the natural environment can be a challenge.

Photo of trail on edge of grassy bluff
The Bay Trail at Point Pinole

This delicate balancing act has been the subject of continuing debate in the Bay Area and worldwide. Many resource managers and environmental advocates are concerned that the presence of humans (and their pets) on trails may be deleterious to shoreline wildlife. These concerns often lead to heated controversy and can sometimes create roadblocks for trail implementation. Conversely, policymakers are often frustrated because there is limited scientific data to support expressed concerns about the potential impacts of public access trails on wildlife.

To begin to find answers to these questions, the Bay Trail Project initiated a study to look at if and how recreational trail users impact shorebirds. The Wildlife & Public Access Study, launched in 1996, is being led by an independent research team. Specifically, the Study is examining the potential effects of non-motorized recreational trail use on the diversity, abundance, and behavior of shorebirds and waterfowl that use mudflat foraging habitat along the Bay Trail. The Study will build a foundation of statistically valid data that can begin to guide the development and management of trails in a manner that respects and protects wildlife.

Photo of busy trail with dog walkers
Dog walkers at Point Isabel

The research team completed two years of field research in 2001, and produced preliminary findings based upon summary data. The preliminary findings indicated that the study functioned as designed and suggested that there is no general relationship between trail use and either bird abundance or overall species diversity in foraging habitat in the San Francisco Bay area. However, there were many caveats, and much more to learn from the detailed data sets and statistical analyses. The Study has generated great and broad interest. Funds for a third phase of research were secured and in the fall of 2004, the team was back in the field for an additional quarter of field work.

To address questions about the data already collected, two new features were added to the protocols implemented during the first two years. In addition to collecting data on trail users and bird diversity, abundance, and behavior, the study took a qualitative look at food supply.

The team also evaluated whether there is significant impact on shorebirds and waterfowl in the quads when observers are present as compared to when no observers are present. The principal investigators have completed the analysis of the mountain of data collected during the 27 months of observations and expect to have a final report available for presentation to the Bay Trail Board of Directors in May 2006, followed by submittal to peer reviewed journals later this year.

Photo of trail along marshes
The trail through the East Bay marshes (click photo to enlarge)

Gap Analysis

Two of the most commonly asked questions raised by funders and policy-makers are "when will the Bay Trail be complete, and how much will it cost?" To this end, the San Francisco Bay Trail Gap Analysis Study was initiated. The geodatabase and geographic information system (GIS) created as background for the study provides staff with details on every gap in the Bay Trail system, and includes such information as proposed trail type and surface, obstacles to implementation, cost for construction, design and permitting, and estimated completion timeline.

Using the cost-estimating methodology created by trail planning professionals for this particular project, and the best available information regarding timeframes for completion, the cost to complete the remainder of the Bay Trail will be approximately $188,000,000. This estimate includes costs to plan, design, permit and build, and does not include trail segments that will be included in larger transportation infrastructure projects, nor does it include costs for segments that will be implemented as part of a permit requirement or as formal mitigation measures. The estimated timeframe for completion is 15 years, or full build-out in 2020.

Photo of paved trail by bay
The trail through Burlingame on the west side of the Bay

As the Bay Trail slowly encircles the Bay, momentum toward what the San Francisco Chronicle has dubbed "an unofficial national park— right in the midst of the nation's fifth-biggest urban area" (San Francisco Chronicle Special Edition— "The Bay Trail Adventure," August 2003) continues to gather, and the benefits of the trail only seem to multiply. Whether riding in a pack of proficient road cyclists at 30+ miles per hour, or "Birding the Bay Trail" with the Pt. Reyes Bird Observatory guide, the Bay Trail offers something for all 7+ million Bay Area residents.

Bay Trail maps including photos and recommended routes are available for purchase from our website. To order maps, t-shirts, hats, The San Francisco Bay Shoreline Guide or for more information, please visit

The Bay Trail Project is a non-profit administered by the Bay Area's regional planning agency, the Association of Bay Area Governments (ABAG). Through funding provided by the California Coastal Conservancy, the Bay Trail Project provides grants to local jurisdictions for planning and construction projects so that the trail can be implemented at the local level. The Bay Trail is not built through grant funding alone— private shoreline development projects, local grassroots efforts, as well as cities and towns constructing segments as part of their own recreational infrastructure plans are equally important to system-wide completion.

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