The District 4 Alemany Project Fact Sheet

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What is the project about?

The US-101 freeway in San Francisco was built in 1950. This section of freeway, just south of the “hospital curve” corridor, above Alemany Blvd is a bridge with an approximate length of 800 feet. The project is to replace the concrete bridge deck in both northbound and southbound directions above Alemany Circle while maintaining both regional and local traffic.

  Alemany Project Map

Why do the decks need to be replaced at this time?


Caltrans performs bi-annual inspections for all of its bridges. The inspection reports revealed cracking and corrosion of the decks and recommends replacement. The column and foundation are in satisfactory condition. Caltrans routinely repairs unsafe cracked sections, potholes, and worn surfaces at night by closing lanes so maintenance workers can access the site. The frequency of those deficiencies will accelerate due to the corrosion.

The new decks will perform better and provide a higher chance that the freeway is operable during a major earthquake.

How will traffic be maintained during construction?

Before demolition can occur on the US-101 northbound decks, traffic will be detoured to a 2 lane offramp and onramp at Alemany exit. The northbound US-101 Alemany exit will be closed 3 days in advance and eastbound Alemany Blvd will be closed to through traffic so that the project off and onramp detour can be constructed. The existing westbound Alemany Blvd will be converted to a 2 way street to also accommodate east bound traffic. Once the northbound detour is in effect, the decks will be demolished and reconstructed within approximately 9 days. Once northbound decks are completed, the southbound US-101 traffic will be crossed over to the newly constructed northbound deck while the southbound deck is being demolished and reconstructed in approximately another 9 days. It is likely a total of approximately 18 days that this project will affect regional traffic. Local Alemany Blvd will be restored as soon as possible.

What is the travel speed for the US-101 detours?

The speed limit will be 35 mph for the northbound off and onramp detour. The speed limit in the second half of construction for southbound crossover transition will be 35 mph.

I drive on the US-101 from the peninsula though the project site during my daily commute. How does this project affect me?

For northbound travel, expect long delays of over 6 miles from the project site as you approach the SFO and 380 interchange for the approximately 18 day duration. For your return trip home during the afternoon commute, expect traffic to slow down on the southbound US-101 because of the adjacent northbound construction activities. After the northbound deck has been reconstructed, the southbound US-101 traffic will be crossed over to the newly constructed northbound decks while the southbound deck is demolished and reconstructed. This crossover of southbound motorist onto the northbound deck will cause delays that may extend to the Bay Bridge.

I live nearby. How will traffic affect me?

Although local traffic movements will be accommodated, expect traffic delays coming out of the business districts and getting to nearby US-101 northbound freeway onramps at Cesar Chavez and south of Silver Avenue US-101 onramp. The northbound Alemany Bayshore offramp will be closed for most of July 2020. Motorist are advised to take the northbound US-101 Silver offramp. US-101 at 3rd Street northbound onramp needs to be closed to facilitate as efficient of an operation as possible. 3rd Street northbound onramp will be closed from 6 am to 9 pm and advised to take I-280 at Cesar Chavez or at Geneva.

Will businesses be open?

Yes, San Bruno and Bayshore business and farmer’s market and flea market will be open.

What can I do to help alleviate traffic?

Please consider taking alternative routes on the freeway and city streets if available. If possible, delay your trip to the off peak travel periods, consider public transportation. Caltrans is working with employer groups to help facilitate ridesharing and alternative work hours if possible during this period in July 2020.

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