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Posted on December 12, 2013 at 1:52 PM by grodericks grodericks
PG&E stands for Pacific Gas & Electric. We are all aware of the overhead (and sometimes underground) lines that provide electricity to our homes. When there is a hazard involving these lines it is often something to which we can immediately see and respond, such as a downed power line with an arcing cable or getting home at night to find the lights are out. Come to find out, a transformer somewhere down the street has blown or a tree fell into the lines.
But the “G” in PG&E represents the company’s massive underground gas pipeline infrastructure. Gas lines, like electricity lines, are essential to the provision of services to an urbanized community and are a fact of delivery of those services. Like underground sewer and water lines, these are assets out of sight and out of mind when it comes to identifying a local hazard. Lately there has been a lot of press surrounding PG&E’s gas pipeline infrastructure and their efforts and ability to maintain it. The Town has been engaged with PG&E in an effort to trace, identify, and document the location and condition of PG&E’s transmission and distribution lines running underground throughout Town. These are the lines that PG&E maintains. Every resident will typically have a local lateral line, like a local sewer or water laterals, these are maintained by the resident.
Recently, the Town met with PG&E to go through the detail. PG&E services 2,558 gas meters in Atherton using approximately 56 miles of gas distribution and service lines. Safety regulations require PG&E to conduct periodic or routine leak surveys on its distribution and transmission systems. The frequency depends on the local conditions of the line itself such as where it is installed, its material, and operating conditions. Field technicians perform the surveys using both vehicle-mounted and handheld leak detectors. In general, PG&E surveys its transmission and distribution facilities at least once every five years and annually surveys those lines in business districts and near public facilities.
A “distribution line” is anywhere from ¼” to 24” inches in diameter and operates between 2 psi and 60 psi. These are not major lines and they do not operate at a significant pressure level. Most every street in Atherton will have a distribution line running underground off of which household lateral lines connect. These are smaller, low-pressure lines – which in most instances, are the ones that contractors and homeowners will damage when they are conducting work in and around their property. This is the origin of “Dig Alert – Call or Click before you Dig” to protect that underground, invisible infrastructure. Anyone doing any type of digging, except homeowners working on their own private property without the need of a permit or power equipment, is required – required – to contact DigAlert to determine the location of any underground utilities. Formed in 1976 in response to a deadly incident in Culver City, DigAlert can be located at www.digalert.org.
A “transmission line” – now that’s a major line. Transmission lines are between 10” and 42” inches in diameter and typically operate between 150 and 900 psi. These are the major lines through which PG&E transmits its service. There are five transmission lines operating in Atherton boundaries, two are main distribution lines and three are distribution feeder mains (smaller lines).
Line 109 and Line 132 are the larger of the transmission lines in Atherton. They are both steel lines operating at 300 psi. Line 109 was installed in 1936 with upgrades in 1989. It is between 22 and 24 inches in diameter. It is located generally along the 280 border of Town. Line 132 was installed in 1947 and is 24 inches in diameter. It too is located generally along the 280 border of Town.
The Town and its emergency service responders are aware of the exact locations of these lines as they are part of the Town’s emergency awareness and response plans. However, public distribution of the survey maps denoting the exact location of the line(s) are not publicly distributed due to security concerns related to access to such infrastructure.
The smaller transmission lines feed Atherton’s local distribution lines. Line 0205-01 is of varying size as it services downward for pressure. It ranges from 2 to 6 inches in diameter. It operates at 230 psi. It is a steel pipe originally installed in 1938 with upgrades in 1940, 1963, 1971, 1972, 2003, 2005, 2011, and 2013. The line travels generally along Walsh Road to Alameda de Las Pulgas from Lines 109 and 132.
Line 0217-01 is of varying size from 6 to 8 inches. It is a steel pipe operating at 175 psi. It was originally installed in 1987 with upgrades in 1989. It is located generally along Ringwood Avenue from Middlefield to the 101 Freeway. It connects to Line 0201-01 at Middlefield. Line 0201-01 runs out of Town at that juncture. Line 0201-01 is of varying size from 6 to 8 inches. It is a steel pipe operating at 120 psi originally installed in 1927 with upgrades in 1987 and 2005.
A report from PG&E on the Town’s pipeline infrastructure is available online via the Town’s website. It details the lines discussed above as well as provides information on PG&E’s inspection, maintenance, and upgrade plans and programs.
For more information, feel free to contact Town Hall and we can put you in touch with someone at PG&E who can provide you with additional information and assistance.
Town of Atherton
Tag(s): PG&E, infrastructure, hazards, gas lines