January 20, 2012Editor’s Note: In December 2011, Trenchless Technology readers learned about the history and political challenges that engineers and city officials tackled to build the colossal Hetch Hetchy Water System in the early 1900s. In 2002, the San Francisco Public Utilities Commission faced similar challenges to rebuild, retrofit and replace the aging water infrastructure that serves 2.5 million customers in the Bay Area. In this article, readers will learn more about the challenges SFPUC staff and consultants faced for the Crystal Springs Pipeline No. 2 Replacement Project.
First built in the 1930s, Crystal Springs Pipeline No. 2 (CSPL2) is a 19-mile-long steel pipeline that provides drinking water to several cities on the San Francisco Peninsula. Eighty years later, San Francisco Public Utilities Commission (SFPUC) engineers and contractors have reached the halfway point of a construction program to seismically upgrade sections of this large and antiquated water delivery pipeline that provides drinking water to hundreds of thousands of residents in the urban areas of the San Francisco Peninsula.
In 2002, San Francisco voters approved the program, which included increased water rates and allowed SFPUC to finance improvements to rebuild the regional water system.
CSPL2 is one of a number of pipeline replacement projects in the $4.6 billion Water System Improvement Program. In 2002, SFPUC engineers identified this water main to be seismically upgraded and replaced to ensure a reliable water supply following a seismic event. CSPL2 is also one of the most complicated pipelines to replace because of the environmental reviews, community relations issues and the fact that much of the pipeline lies under the Bay Area’s oldest highway, El Camino Real.
“When the planning of this regional water main replacement began in 2004, SFPUC allocated a little more than $50 million for this project,” says CSPL2 project manager Susan Hou. “The replacement of this pipeline will enable it to withstand a 7.9 magnitude earthquake and last another 80 years.”
While this water pipeline ranges in width from 60 in. to 54 in., there were many design and planning challenges that needed to be addressed before construction could start. The project team kicked off construction last April after five years of research, planning, design, environmental review and a lengthy permitting process. The completion of construction in the 18 work areas within seven Bay Area cities is scheduled for January 2013.
Before elaborate interstate freeways were built, narrower California highways were the primary means to travel on the San Francisco Peninsula. El Camino Real is the Bay Area’s oldest highway serving more than a dozen cities between San Francisco and San Jose. More than a couple million motorists use it annually, and more than three miles of the CSPL2 water main is located under this busy highway.
CSPL2 was first installed to transport the high-quality Hetch Hetchy water to the San Francisco area from more than 160 miles away. It was the abundant, high-quality water that supported urban development around the pipeline alignment, including the need to construct the historic highway to support the densely populated neighborhoods and bustling downtown areas.
SFPUC water engineers analyzed the geography of the alignment and identified a number of constraints ranging from traffic to environmental impacts.
“After five years of planning, our biggest challenges were to address and mitigate traffic impacts, utility conflicts, design around tree roots in the Burlingame community and to coordinate with utility companies,” says CSPL2 project engineer Paul Y. Louie.
Towering Eucalyptus trees are iconic in the City of Burlingame, and the city’s logo prominently features a tree in the background. Encroaching roots from the tree were a major concern on this project as well. If crews removed trees, not only did it present environmental challenges, but community members would be unhappy, stirring outcry to draw media or city council attention.
Tree challenges coupled with highway traffic impacts forced project designers to be creative on how they would plan for construction along El Camino Real. With the help of design consultant URS Corp., 11 pit locations were identified to help crews avoid tree removal and create access pits for the construction crews to slipline a new, smaller-diameter pipe into the host pipe.
While URS Corp. helped SFPUC engineers locate and design the possible pit locations, many of these locations were revised as utility conflicts. Driveway access and tree removal concerns came up when the contractor began preparing the pits. In fact, due to old drawings, community concerns and inaccurate information from utility companies, pit locations were moved slightly at least three times.
How It Is Being Built
While sliplining is a common practice in the water industry, the small size of these pit locations (80 ft by 10 ft) is challenging when installing a massive pipeline along a narrow and bustling highway.
Ranger Pipelines Inc. is a small Bay Area contractor that has worked on several WSIP pipeline projects in San Francisco. Ranger Pipeline is creative and has in-house trade secrets that gives it an edge when bidding on these kinds of projects. Given the small size of the access pits, Ranger Pipelines designed a custom pulley system for this project to slipline the new pipeline carefully through the existing pipe. Lowering the pipe into the trench was challenging, but wheeling it through the pipe and pulling it out from the other end was how Ranger Pipelines successfully completed this delicate task.
Caltrans, the owner of the highway, permitted a seven-hour work day (7 a.m. to 2 p.m., Mondays through Fridays). In the past, projects along El Camino Real were permitted for a five- to six-hour work day. To expedite construction and increase permitted work hours, engineers performed a traffic analysis and submitted the comprehensive report to Caltrans for approval. With this extra effort, construction crews continue to make significant progress each day, and install approximately three lengths of pipeline (each segment is 60 ft long) daily.
“I would encourage utility departments to pothole more — especially with an older pipe,” says Hou. “We coordinated with more than a dozen utility companies before construction started. Unfortunately, when we potholed the area, we realized that our drawings and the neighboring cities were not only out dated, but sometimes inaccurate.”
As construction continues, Ranger Pipelines received only two traffic complaints and a handful of noise complaints as a result of the installation of the steel plates. Otherwise, residents continue to be cooperative, as they understand the importance of improving the water system for the community. While no trees have been removed, careful traffic coordination and strong public outreach to the community continue to benefit the project, so that the contractor can quickly and effectively continue to stay on schedule.
“It is a race against time, and it’s important for the SFPUC to safely and quickly rehabilitate our massive water infrastructure to provide water service to our 26 wholesale customers,” says WSIP director Julie Labonte. WSIP includes more than 80 unique water infrastructure improvement projects, ranging from seismically upgraded tunnels, water treatment facilities and dams in six Bay Area counties.
Susan Hou is the risk manager for the Water System Improvement Program and is a project manager at SFPUC. She has worked on WSIP since 2002, and managed four WSIP projects to date.
Paul Louie is a project engineer at SFPUC and worked on WSIP for more than six years. Previously, he worked at the San Francisco Airport for 10 years. To date, Louie has worked on four WSIP projects.
Daniel Jaimes is an onsite WSIP community outreach consultant at the SFPUC since 2009. He is also the communications liaison for the CSPL2 replacement project. This is his fifth pipeline project.