San Francisco Inner Sunset
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Underground Construction is nearing completion on Pacific Gas and Electric Companyís Inner Sunset Phase 2 project. The project located in the Sunset District of San Francisco is part of PG&Eís Rule 20 overhead-to-underground utilities conversion master planned project. The project scope consists of placing approximately 14,000í of joint distribution trench, the installation of approximately 8,500í of high-pressure gas main, and approximately 350 residential/ commercial gas services. The construction team consists of Project Manager Ashley Carter, Superintendent George Castro and Foremen Jose ìPepeî Machuca, Jesus Ochoa, and Cesar Coronel, all performing manhole and trench installation, with Chris Stream heading up the gas service installation. The Sunset District of San Francisco is a collage of the City as a whole. The area boasts Golden Gate Park, the University California San Francisco, a commercial district full of shops and restaurants considered to be among the best in San Francisco, and beautiful neighborhoods of century old homes. Though a wonderful place to visit or live, the characteristics of the area create a very difficult setting for a construction project. These difficulties include heavily congested streets and sidewalks, major public transportation routes used by both buses and rail cars, densely populated commercial business districts, holiday moratorium restrictions, and the tough construction requirements set by the Department of Parking and Traffic. |
Among the most daunting challenges facing the construction team is the subsurface soil conditions, consisting of fine sugary sand that once landscaped the area with sand dunes leading out to the Pacific Ocean. Though developed over a century ago, one swipe of the shovel below the concrete reveals conditions fit for sand toys rather than excavators. To sustain a safe excavation, nearly the entire trench has been solid sheeted with a combination of hydraulic shores, sheeting, and many units of plywood. Also inherent to the aging District has been constructing among an infrastructure placed in the early 20th century. Because the majority of trench is located in the sidewalk area, aging and decaying utilities are abundant. The crew has done a masterful job of working cautiously around these utilities. In order to mitigate the tough construction conditions, a number of changes were made in the field. The crew utilized small rubber track excavators that weighed much less than the traditional backhoe which gave the operator greater swing mobility in confined spaces. The crew also introduced water to the in situ soil prior to excavating to add cohesiveness to the sand. Additionally, aluminum sheets were fabricated to mimic the characteristics of plywood yet be lighter to handle and easier to place in the trench. Finally, dozens of special permits were applied for and granted to close sidewalks and minimize pedestrian traffic in the construction zone. |
Possibly the biggest challenge of the Inner Sunset Phase 2 Project was re-acquainting ourselves with the gas service work. This work is characterized by placing the gas service lines from the newly installed high pressure gas main to the connection at the existing house lines including the placement of a regulators, meters, risers, etc. The work consists of a wide range of skills including pipefitting, welding, and carpentry, among others. Additionally, scheduling plays a key role in coordinating construction between the tenant, Underground Construction Co., and PG&Eís relight crews to minimize the inconvenience to the resident. Midway through the project, Pacific Gas and Electric expressed interest in accelerating the project to meet a December 31, 2002 completion date. In order to meet the deadline, Underground and PG&E have been working together to maximize the strengths of both companies. This included placing an additional trenching crew on the project to install the high-pressure gas main, so PG&E forces could jointly perform the gas service work. By doing so, PG&E was able to begin their shutting off and abandoning of aging gas mains to meet their deadline. The PG&E Inner Sunset Phase 2 project has posed many challenges for
Underground Construction Co. Through the hard work of the construction team,
including the fine efforts of the 35-man crew, the project will be finished
ahead of schedule and to satisfaction of the owner, among some of the toughest
conditions found in San Francisco.
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