Notice of Availability for Draft Initial Study/Environmental Assessment (IS/EA) Document have been posted on CCTA website. You can view the documents at: http://ccta.net/EN/main/state/162/166/sanpablointerchange.html

Announcement of Public Meeting for I-80/ San Pablo Dam Road Interchange Project. The public is invited to review and comment on the draft IS/EA. Comments must be submitted to Caltrans by 5:00 pm September 8, 2009. A public meeting will be held on August 19, 2009 from 6:00 – 8:00 PM in Maple Hall at San Pablo City Hall, 13831 San Pablo Avenue, San Pablo,California. Click here for Public Meeting details (pdf of notice)

The existing San Pablo Dam Road over I-80 is a narrow 4-lane (2 lanes each direction) bridge with no shoulders or turn lanes.  There are currently narrow sidewalks on both sides of the bridge.  The bridge vertical clearance above I-80 is below current Caltrans standards which makes it prone to accidents.  During peak periods, traffic backups extend in both directions on San Pablo Dam Road.   Left turns into Amador Street are currently not allowed from San Pablo Dam Road westbound direction resulting in unnecessary out-of-the-way travel.  To the north of the I-80/San Pablo Dam Road lies the El Portal Drive interchange, which consists of an isolated (separated from interchange) westbound on-ramp and a partial diamond interchange that are separated by a 2500-foot-long frontage road that runs parallel to I-80. The partial interchange (missing one or more ramps) consists of a westbound off-ramp and eastbound on- and off-ramps, which are connected by the El Portal Drive undercrossing. To the south of the I-80/San Pablo Dam Road, an isolated off-ramp serves McBryde Avenue. The close proximity of the El Portal Drive westbound on-ramp and the McBryde Avenue off-ramp to San Pablo Dam Road interchange contributes to the congestion on the freeway and interferes with access to and from the San Pablo Dam Road.

There is an existing pedestrian bridge over I-80 that serves the Riverside Elementary School. The over-crossing is located east of the terminus of Riverside Avenue and is connected to the Amador Street by a paved pedestrian walkway.  There are also existing non-standard pedestrian access ramps within the project study area that are not in compliance with ADA standards.

To the east of Amador Street and the I-80/San Pablo Dam Road interchange, a geologically unstable hillside (China Slide) is located.

Two design alternatives and a “no-build” alternative are being considered in this project.  Both “build” alternatives include modifications to the El Portal Drive, San Pablo Dam Road, and McBryde Avenue interchanges.

The “Lanes Added” build alternative (Alt-1) would replace the existing four-lane San Pablo Dam Road overcrossing with a new wider seven-lane bridge with shoulders and sidewalks on the same alignment as the existing overcrossing (Figure A).

Figure A: Lanes Added – Alternative 1

The “Tight Diamond” build alternative (Alt-2) would replace the existing San Pablo Dam Road overcrossing with a six-lane bridge with shoulders and sidewalks (Figure B); however, in this alternative the new overcrossing would be curved (re-aligned) to allow relocation of the Amador Street/San Pablo Dam Road intersection to the east without encroaching into the geologically unstable hillside (China Slide).  Amador Street would be relocated over 410 feet to the east and San Pablo Dam Road would be realigned to the north. The eastbound I-80 off-ramp would be lined up with the eastbound I-80 on-ramp to create a typical tight diamond interchange. Under this alternative, a left turn lane would be added from westbound San Pablo Dam Road to Amador Street. 

Figure B: Tight Diamond - Alternative 2

Under both Alternatives 1 and 2, the following improvements are proposed:

1. Turn lanes would be added on San Pablo Dam Road to the I-80 on-ramps.
2. The pedestrian overcrossing serving the Riverside Elementary School would be replaced with a new one, and the landing area on the eastside of the freeway would be relocated to the east side of the Amador Street.
3. The El Portal Drive westbound on-ramp would be relocated (See Figure C) to the north to provide a longer auxiliary lane between the on-ramp and San Pablo Dam Road westbound off-ramp.
4. A new one-way limited access frontage road would be constructed to the south side of I-80 between San Pablo Dam Road and McBryde Avenue.  The new frontage road would replace the McBryde off-ramp (See Figure D) to eliminate the weaving maneuver between San Pablo Dam Road traffic entering westbound I-80 and I-80 traffic exiting at McBryde Avenue.  Traffic heading to McBryde Avenue would exit with San Pablo Dam Road traffic and continue on the frontage road to McBryde Avenue.  Access to neighborhoods served by McBryde off-ramps would continue to be easy but safer with a minimal increase in travel time. A barrier will separate the new frontage road and Riverside Avenue.
5. I-80 westbound exit to San Pablo Dam Road will be widened to two lanes instead of one.

Figure C: El Portal Drive On-Ramp

Figure D: Frontage Road to McBryde Avenue