Cemex to supply state-of-the-art transit systems in California Bay area, USA
Cemex is to supply structural concrete on two massive, state-of-the-art transit systems in the California Bay Area which, upon completion, are expected to serve more than 61 million people every year.
Between 2000 and 2030, 1.25 million new vehicles are expected to enter the Northern California Bay Area -- a 31.5 per cent increase over 30 years. In response, cities and local transportation agencies are providing much needed alternatives for commuters through the construction of new, state-of-the art mass transit systems. Cemex is contributing to two of these: San Francisco’s new intermodal Transbay Transit Center, and an ongoing extension of the Bay Area’s Rapid Transit system into Silicon Valley.
“At Cemex, we work in close partnership with our customers and communities to help build infrastructure that supports growth and sustainability,” said Karl H Watson Jr, President of Cemex in the USA. “These two projects are testimony to our technical expertise and our commitment to building a better future for our customers and in the communities in which we operate."
The five-story, multi-modal Transbay Transit Center is expected to transform San Francisco into a vibrant, transit-friendly area in the tradition of great cities such as London and Paris. While in Silicon Valley, the 10-mile, two-station “Berryessa Extension” is part of an ambitious effort to extend the reach of the BART system to Silicon Valley, modernising the 40-year-old system currently serving the area. Cemex is supplying concrete on these massive projects that had very specific considerations due to the Bay Area’s groundwater levels and the sustainability specifications of each project.
In San Francisco, the Transbay Transit Center underground structure required very stringent low permeability and low shrinkage concrete. Complex logistics due to the location in an extremely busy neighborhood meant that Cemex trucks could only be dispatched starting at 11:00pm on Friday through Saturday afternoon to complete the 15 large, continuous pours of up to 5000 cubic yards. Along the Berryessa extension’s 10 mile route in the South Bay, groundwater levels varied and required individualised attention. Cemex worked closely with the client to develop, test and deliver 35 tailor-made concrete mix designs to meet the needs of each section of the line.
“The design of the Berryesa extension project had a specific need in terms of the weight of the concrete structures that were placed under ground level,” said Francisco Rivera, Cemex Vice President of Ready-Mix for the Bay Area region. “The type of aggregates that we selected adjusted perfectly to respond to the weight requirements solicited by our client.”
Renowned architect César Pelli’s firm, Pelli Architects, designed the Transbay Transit Center with the aim to achieve a Leadership in Energy & Environmental Design (LEED) gold certification; LEED is the world's premier benchmark for high-performance green buildings. In order to answer the challenge, a Cemex quality control team worked closely with the client to design concrete mixes for all the structures that included up to 35% supplementary cementitious material. The Berryessa project also had sustainable components, including a concrete mix that Cemex specially designed using recycled material removed from the old rail beds and a concrete mix for the massive foundations that included 50% supplementary cementitious material.
According to the Transbay Joint Powers Authority, The Transbay Transit Center is expected to serve up to 45 million people every year starting in 2017, removing thousands of daily-commute vehicles from the road. The Berryessa extension is expected to be completed in 2018, and the Santa Clara Valley Transportation Authority anticipates serving a combined 45,000 daily passengers on its two stations by 2030.
