Despite a decade of delays, funding uncertainties and political hurdles, California's embattled high-speed rail project continues to slowly advance, with plans to complete the section between San Francisco and Los Angeles by 2033.

On Friday, the effort hit a milestone of sorts when the California High-Speed Rail Authority, which is charged with implementing the project, released an environmental analysis that describes the latest proposal for the Peninsula segment and lists some of the impacts — both good and bad — that communities along the rail line will experience once the project is in place.

The draft Environmental Impact Report identifies about a dozen impacts that are "significant and unavoidable" and, as such, would require a statement of overriding consideration from lawmakers before the project can proceed. Some of these involve disruptions to bus routes during the construction period, while others deal with noise and vibrations relating to rail operations. The new document also suggests that emergency responders in the Peninsula area may face significant delays in crossing the tracks once the new train system is up and running.

Consistent with the rail authority's prior plans, construction is envisioned in two major phases, with the first part of the system stretching between San Francisco and Los Angeles and subsequence expansions to Sacramento and San Diego. The rail authority has already been constructing a portion of the line in the Central Valley, with the goal of ultimately connecting this segment to San Francisco and Los Angeles.

The new environmental document focuses on the northernmost segment of the first phase. It analyzes two similar alternatives for the segment between San Francisco and San Jose. Each would rely on the "blended approach," with high-speed rail and Caltrain sharing the same two tracks on the Peninsula.

The most notable differences between Alternative A, which is the agency's preferred alternative, and Alternative B, are that the latter calls for adding another set of passing tracks in San Mateo County and a dedicated viaduct for high-speed rail in the southern part of the segment, near San Jose. As such, Alternative B would involve more construction, great impacts and higher costs, according to the environmental document.

The system described in the EIR would operate at speeds of up to 110 mph on the Peninsula, with high-speed rail and Caltrain operating on a "coordinated schedule" and with high-speed rail trains having the ability to pass Caltrain trains at the existing four-track segment in the Millbrae station (as well as a new passing track, if Alternative B is adopted).

The main goal of the new system, according to the EIR, is to decrease traffic congestion, lower greenhouse gas emissions and support the California economy. The current statewide and regional transportation system "has not kept pace with significant increases in population, economic activity and tourism in the state, including in the Bay Area," the EIR states.

Currently, the trip between San Francisco and Los Angeles takes between four-and-a-half hours and 11.5 hours, the document states. The completion of Phase 1 of high-speed rail would allow for travel times between the two cities of less than three hours.

The construction plan calls for building two lines — one in the Central Valley (between Madera and Bakersfield) and one in the Bay Area, and then connecting them through the Pacheco Pass tunnel to create what the document calls a "Valley-to-Valley connection," with continuous service from San Francisco to Bakersfield.

"After that portion of the system is built, it is anticipated that the system would be extended to complete all of Phase 1 and ultimately Phase 2," the document states.

The 49-mile section between San Francisco and San Jose would have three high-speed rail stations in San Francisco, Millbrae and San Jose.

Even though the rail authority has abandoned its earlier plan to build a station or a set of passing tracks in the Midpeninsula area, the document indicates that the rail system will create some problems for local jurisdictions. While cities along the Caltrain corridor are exploring ways to separate the tracks from local streets so that they no longer intersect at grade crossings (a realignment known as "grade separation"), the new document suggests that the California High-Speed Rail Authority has no immediate plans to assist with that effort, which is widely seen as necessary to both ensure safety and prevent heavy congestion around intersections.

The rail authority's plan for preventing collisions between cars and trains is not grade separation but the installation of four-quadrant gates that would extend against all lanes of travel, blocking cars from entering the tracks.

"These gates would prevent drivers from traveling in opposing lanes to avoid the lowered gate arms," the document states. "Pedestrian crossing gates would be built parallel to the tracks and aligned with the vehicle gates on either side of the roadway."

While these gates would discourage cars from getting on the tracks, they also will result in greater delays at rail crossings. The document states that the increase in "gate-down time" from the added high-speed rail trains would "result in potential delays in emergency vehicle response times for fire stations/first responders in San Francisco, Millbrae, Burlingame, Redwood City, Menlo Park, Palo Alto, and Mountain View." While cities like Menlo Park, Mountain View and Palo Alto have been trying to mitigate the impacts of train-related delays by planning for grade separation, the rail authority lists the potential disruptions to emergency responders as a "significant and unavoidable" impact.

The document also found that additional traffic near the three new high-speed rail stations would result in "potential delays in emergency vehicle response times for fire stations/first responders," the report states.

Most of the other "significant and unavoidable" impacts pertain to specific locations along the line, including sites near the proposed stations where land-use patterns would have to be altered to accommodate the new system. Some are limited to the construction period. These include impacts of construction on air quality, noise and vibration.

The new line could also bring "continuous permanent impacts" on emergency access and response times in Menlo Park and Mountain View, unless these two cities opt to construct and operate "emergency vehicle priority treatments" east of Ravenswood Avenue and adjacent to Rengstorff Avenue, respectively.

The document estimates that the 49-mile segment between San Francisco and San Jose would cost between $4.3 billion and $6.9 billion. According to the rail authority's business plan, the estimate for the entire Phase 1 segment between San Francisco and Los Angeles is about $77.3 billion.

While the rail authority is planning to complete the system by 2033, progress to date has not gone as planned. Since California voters approved $9.95 billion in 2008 for the high-speed rail line and related transportation improvements, the cost of the new system has ballooned and the project has been subject to intense scrutiny and criticism from state and local leaders, as well as scathing audits from California's state auditor and from the U.S. Department of Transportation's Office of Inspector General.

The EIR notes that in identifying its preferred alternative, the rail authority chose the option that balanced "the adverse and beneficial impacts of the project on the human and natural environment."

"Taking this holistic approach means that no single issue was decisive in identifying the Preferred Alternative in any given geographic area," the analysis states. "The Authority weighed all the issues — including natural resource and community impacts, the input of the communities along the route, the views of federal and state resource agencies, and project costs — to identify what both agencies (the rail authority and the Federal Railroad Administration) believe is the best alternative to achieve the project's Purpose and Need."